A2A Piper Cherokee 180 User Manual

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A2ASIMULATIONS

CHEROKEE

ACCU-SIM CHEROKEE 180

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RISKS & SIDE EFFECTS

ERGONOMIC ADVICE

Always maintain a distance of at least 45cm to the screen to avoid straining your eyes.

Sit upright and adjust the height of your chair so that your legs are at a right angle. The angle between your upper and forearm should be larger than 90º.

The top edge of your screen should be at eye level or below, and the monitor should be tilted slightly backwards, to prevent strains to your cervical spine.

Reduce your screen’s brightness to lower the contrast and use a flicker-free, low-radiation monitor.

Make sure the room you play in is well lit.

Avoid playing when tired or worn out and take a break (every hour), even if it’s hard…

EPILEPSY WARNING

Some people experience epileptic seizures when viewing flashing lights or patterns in our daily environment. Consult your doctor before playing computer games if you, or someone of your family, have an epileptic condition.

Immediately stop the game, should you experience any of the following symptoms during play: dizziness, altered vision, eye or muscle twitching, mental confusion, loss of awareness of your surroundings, involuntary movements and/or convulsions.

A2ASIMULATIONS

CHEROKEE

ACCU-SIM

CHEROKEE 180

6	PIPER CHEROKEE PA-28-180 AN
	AEROPLANE FOR THE REST OF US

CHEROKEE SPRING

DEVELOPER’S NOTES

FEATURES

QUICK-START GUIDE

ACCU-SIM AND THE CHEROKEE 180

ACCU-SIM AND THE COMBUSTION ENGINE

PROPELLERS

GENERAL

LIMITATIONS

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102

NORMAL PROCEDURES

PERFORMANCE

WEIGHT AND BALANCE

AIRPLANE & SYSTEM DESCRIPTIONS

EMERGENCY PROCEDURES

EMERGENCY PROCEDURES EXPLAINED

AIRPLANE HANDLING,

SERVICE & MAINTENANCE

CREDITS

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PIPER CHEROKEE PA-28-180 AN AEROPLANE FOR THE REST OF US

By Mitchell Glicksman

This flying machine may rightly be called a “Goldilocks” aeroplane. It is not too big and not too small, not too complex and not too simple, etc. The Piper Cherokee 180 is, as the little flaxen-haired girl so famously declared, “Just right!”

The entire PA-28 Cherokee line from the humble twoseat 150 h.p. PA-28-140 to the swift, retractable undercarriage PA-28R-200 Arrow, to the powerful, heavy load-carrying 235 h.p. PA-28-235 Dakota, is respected as being one of the most popular, commercially successful series of aircraft containing within some of the most pilot-friendly aeroplanes ever built. Each member of the Cherokee family fills its particular niche at least as well as, and often better than other aircraft of similar type. However, of all of the many Cherokees the Cherokee 180, sitting as it does right in the middle of the pack has proven itself to be most popular and justifiably so.

Introduced to the public in 1961, the first Cherokee, the 150 hp PA-28-150 was immediately well-received setting the pace for its later siblings who went on to provide pilots of all levels of experience with honest,

dependable and well-performing aircraft which are fun and satisfying to fly, reliable, safe and economical to own and operate. However, getting to this place took some time and some very astute business and aeronautical skills and sense.

HIGH FLYING ON HIGH WINGS

After a necessary hiatus during World War II the industry known as “General Aviation” (GA) which encompasses all privately (as opposed to government and airline) owned aircraft recommenced in a far better economic environment, the Great Depression not actually having ended until the U.S. entered W.W.II on December 8, 1941. For the first post-war years of the later 40’s, however, it was very slow going in the GA market. The virtually universally held high expectations that droves of exservice pilots would enthusiastically seek to own their own aeroplanes turned out to be more than somewhat optimistic.

As the turbulent and violent early 40s and the uncertain, transitory late 40’s passed into history, and after

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1961 Piper PA-28-150 Cherokee 150

the first three years of the next decade in which a new, smaller, but no less vicious conflict in Korea came and went, a new, thriving American middle class began to enjoy the substantial positive changes engendered by the new peacetime culture and economy. As the economic boom of the ‘50s began to improve the lives of so many, all markets, and no less the GA market, began to grow and thrive as well. By the end of the ‘50s very few aircraft of the pre-war era were still being manufactured; however, in their place promising, new, exciting, and for those times revolutionary aeroplanes began to become available.

But old conventions die hard. In the immediate postwar era and for more than a decade most GA aeroplanes still had wings which sat up atop of the fuselage (known as the “high wing” design) as they had in the pre - war years. The prominent post-war manufacturers of GA aeroplanes, Piper, Cessna, Taylorcraft, Stinson, Aeronca, Luscombe and such all exclusively offered aircraft with high wings and, naturally, that was how the public pictured all GA aeroplanes, all of which they generally deemed to be “Piper Cubs”.

The prolific and successful high-wing design has a number of virtues: it is easier to design and build a wing which does not have to support itself (non-cantilever), but which may be held up with struts attached to the wings and the bottom of the fuselage. The highwing

A real Piper J-3 “Cub”

1948 Stinson 108-2

1947 Luscombe 8a Silvaire

1948 Taylorcraft BC-12d

1950 Aeronca 7AC Champ

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AN AEROPLANE FOR THE REST OF US

Left: 1947 Cessna 190 showing

an unusual cantilever high wing

design was also the choice of most GA aircraft manufacturers because a strutbraced wing is economical to build being that it is lighter, thinner, and requires fewer parts than a cantilever wing. Except for aeroplanes like the Cessna 190/195 models, the Helio Courier STOL (short take-off and landing), and the Dornier Do. 27/28, high-wing aeroplanes of the 50’s were virtually all strut braced.

Of course, the struts themselves add back some the weight savings of a non-cantilever high wing and additionally impose a drag penalty which the cantilever wing design, requiring no support struts, does not. However, while more aerodynamically clean, the weight penalty of the heavier and bulkier cantilever wing may be as great a detriment in its way to overall aircraft performance as is the drag coefficient produced by wing support struts. Properly designed, a wing strut’s production of drag may be minimised. Aside from economical concerns, another of the virtues of a high-wing design is that the pilot’s and passengers’ are granted an almost unobstructed view of the ground during flight. In addition, for purposes of visual navigational orientation as well as for sightseeing, a high wing gives good service.

Today, and since the introduction of the Cherokee series of aircraft in 1961, Piper Aircraft has come to be known as a manufacturer of mostly lowwing GA aeroplanes, the PA-18-150 Super Cub being the lone exception. However, for 24 years, from its founding in 1930, when businessman and oil speculator William T. Piper

purchased the assets of the bankrupt Taylor Aircraft Company for $761.00, except for a small number of interesting Piper low-wing prototypes along the way (PT-1 Trainer-1942, PA-7 Skycoupe-1944, PA-6 Skyse- dan-1945, and PA-8 Skycycle-1945, none of which went into production), Piper Aviation had exclusively produced highwing aircraft until the twin-engine PA-23 Apache in 1954. The Taylor/Piper Cub and its progeny, the PA-15/17 Vagabond, the PA-16 Clipper, PA-18 Super Cub and the PA-20 Pacer with its variants including the revolutionary tricycleundercarriage PA-22 Tri-Pacer were all highwing, fabriccovered aeroplanes. The PA22 Tri-Pacer which was introduced to the public as early as February 1951 predated Cessna’s first tri-gear singles, the 172 and 182 by five years.

Typical wing struts

1960 Piper Pa-18-150 Super Cub

1954 Piper PA- 23-150 Apache

Piper Pa-22-150 Tri-Pacer

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THE BONANZA BONANZA

Of course, amongst all of this GA high-wing high-jinx there were a few exceptions with one very strong standout, the remarkably prescient Beechcraft Bonanza Model 35, designed in 1945 and introduced in 1947. Well named, this aeroplane was a remarkable economic success for Beechcraft, the first GA success story of the immediate post-war times. In fact, it was the enormously positive response to the Bonanza in 1947 that fuelled many GA aircraft manufacturer’s starry-eyed optimism and belief in the sales boom that never happened.

Designed by Ralph Harmon and his associates in 1945 as the war was coming to an end, Bonanza Model 35 had its first test flight on December 22, 1945. Incorporating what was then known of aerodynamics, aviation technology and modern manufacturing techniques, its clean, stressed skin (monocoque) all-metal structure was reminiscent of the recently lionised Spitfires and Mustangs and in many ways was a distinct departure from previous GA aircraft. With a retractable undercarriage, V-tail, seats for four adults, constant speed propeller and powered by a simple to manage and inexpensive to run six-cylinder, horizontally opposed, air cooled 165 hp Continental 0-470- E165 engine, it was the first of a new breed.

In its class and for its time the Bonanza was the epitome of aeronautical design and engineering — fast, sturdy, and looking like nothing that had come before. Sure, it was pricey at the then great sum of $7,975.00 ($7,975.00 in 1947 had the same buying power as $85,165.95 in 2013, annual inflation over this period being 3.65%), but to its purchasers it was worth every dime. Upon its introduction, corporations, businesses and wealthy professionals placed almost 1,500 orders in advance of its release making the Bonanza an unqualified and immediate roaring success.

While Cessna and many other manufacturers seemed to be still tied to old, pre-war designs and concepts, Beechcraft’s Bonanza was an entirely new breed, a leap forward that looked like and in every way was “the very model of a modern” aeroplane. Throughout the 50’s the Bonanza’s sales continued to soar and its place at the top of the food chain remained essentially unchallenged.

1947 Beechcraft Bonanza Model 35

1947 Beechcraft

Bonanza Model 35 instrument panel with 50’s style non- “T” instrument layout and early classic Narco “Omnirange” VOR receiver as almost an afterthought. Noteno ILS equipment and 30’s-40’s throwback throw-over yoke system, toe brakes only on left rudder pedals.

Continental 0-470

1947 Beechcraft Bonanza Model 35 3-view

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AN AEROPLANE FOR THE REST OF US

1958 Piper PA-24-250 Comanche with one - piece windshield and aftermarket spinner

THE BONANZA KILLER

Most painfully cognizant of the Beechcraft Bonanza’s well-deserved success, by the end of the 1950s Piper Aviation was anxious to produce its own modern, all metal, retractable undercarriage, high performance sin- gle-engine aeroplane. Seeking to enter and to dominate the high-performance GA business aeroplane market and unseat the Bonanza, Piper Aviation made ready to topple the King and to take its place on the GA highper- formance throne.

To this end, Piper designed and developed the PA-24 Comanche, “The Bonanza Killer”. Piper Aircraft’s ambitious intent was to not only put an end to the Bonanza’s longheld high-performance singleengine commercial reign, but to put Piper firmly on the map as GAs leading and most advanced aircraft manufacturer. Piper knew that to do all of this would require an exceptional aeroplane, one that performed to the highest standards, was fast, comfortable and safe. Of all, this last requirement was key.

Piper Aviation has traditionally leaned heavily towards flight safety in its designs. Gentle and predicable stall characteristics, inter-connected rudder and ailerons to prevent inadvertent spins on some models, slow landing speeds and the like had been regularly and scrupulously designed into Piper aircraft from the beginning. Accordingly, by the mid 1950s Piper had not been historically known for producing fast, all-metal, high-performance aircraft; but all that was going to dramatically change before the decade was out.

TAKING THE LOW (WING) ROAD TO SLAY THE KING

William T. Piper knew that in seeking to enter the highperformance, single-engine business aeroplane market and challenging the iconic Bonanza that he was he was taking on a very tough, commercially risky task.

By January 1958 the first Piper PA-24-180-Comanche was delivered to the public. Its cruising speed at 75%

1960 Piper PA-24-250 Comanche instrument panel with 50’s style non- “T” instrument layout. As in contemporary Bonanza, radios seem to be almost an afterthought. Note- modern-style VOR but no ILS equipment, dual controls but toe brakes on only left rudder pedals, large flap handle but no Johnson bar brake handle.

1964 Piper PA-24-

250 Comanche with unpainted spinner, aftermarket onepiece windshield and tip-tanks

1967 Piper PA-24-

250 Comanche with

3-blade propeller, aftermarket spinner, onepiece windshield and tip-tanks

1959 Piper PA-

24-250 Comanche Notetail low ground stance, large nose wheel and short main undercarriage legs.

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at 8,000’ is 139 knots (159.85 mph) which in its day was excellent for a four-seat, 180 hp aeroplane, but not quite fast enough to seriously compete with the 165 knot (189.75 mph) 240 hp Bonanza 35H at 75% power.

The first low-wing GA aeroplane produced in over a decade, the Comanche was something new and exciting. A breathtakingly beautiful design, its novel sweptback tail, its gracefully tapering wings and sleek fuselage gave it the look of innovative modernity in the same way that Lancaire and the Cirrus aircraft appear to us today.

Accordingly, Piper began to immediately test the installation of a 250 hp Lycoming O-540 engine in the Comanche. The PA-24-250, introduced in April 1958 has a very competitive 75% cruise speed at 8,000’ of 160 knots (184 mph).

So, did the Comanche actually kill the Bonanza? Well, the answer is clearly, no. However, it did compete well with it and better in that regard than anything else in its time. Piper and Beechcraft continued to strive with each other until the Comanche suddenly ceased production in 1972, along with the excellent, sleek and speedy Twin-Comanche, as a result of catastrophic damage to Piper’s Lock Haven, PA factory caused by the record rising of the nearby Susquehanna River due to Hurricane Agnes. Today, as newer and even sleeker modern composite designs vie with it for top dog in the GA high-performance, singleengine market the Bonanza lives on, albeit in the shape (if not the name) of the venerable, conventional tail Debonaire, and is still in production with no end in sight.

While its time in the market as a new aeroplane was relatively short (1958-72), since its introduction the Piper Comanche has been and still is one the most highlyrespected and desirable GA aeroplanes. A good one in good condition is considered a prime find on the used aircraft market. Today there are many thousands of loyal Comanche adherents who firmly believe, and

with good reason, that it is the most beautiful, elegant Lycoming 0-360 and overall best performing single-engine GA aeroplane

ever built. Right, Scott?

Second test proto-type of Piper PA-24-180 Comanche

1958 Beechcraft Bonanza H35 with tip-tanks

1959 Beechcraft

Bonanza 35J

Piper PA-24- 250 all original

Piper PA-30- 160 Twin Comanche - R. I. P.

contemporary Beechcraft Bonanza G36

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AN AEROPLANE FOR THE REST OF US

HOW ABOUT AN AEROPLANE FOR THE REST OF US?

Without any question, the Bonanza and the Comanche were and are very high performance single-engine GA aircraft aimed at distinctly well-heeled potential private/corporate owners. However, there also existed a significant segment of the GA market that wished to own a new, reasonably fast (if not the fastest), modern, all-metal, fourseat aeroplane, but who could not afford the Comanche’s and especially the Bonanza’s high price tag. FBOs (fixedbase operators), flight school operators and flying clubs were also looking for aircraft that they could rent out at rates that the average weekend private pilot could afford.

As the prosperous second half of the 1950s came to a close, Piper understood that the time of the fabriccov- ered Tri-Pacer and Colt had come to its end. Studies within Piper Aviation in the mid50’s showed that with modern manufacturing techniques it was actually now more cost-effective to produce an all-metal aeroplane than to continue to produce the old school parts and labourin- tensive, metal frame, fabriccovered Tri-Pacer and Colt.

Even with plans to build the Comanche already drawn, the factory tooling up to manufacture it, and with Piper’s well-founded hopes and expectations that its new beauty would well-establish Piper Aviation in the high-performance single-engine, business aeroplane market, William T. Piper knew that if Piper was going to survive and flourish into the next decade and beyond that, further aeronautical invention and progress was wanted. He, his son Pug and the entire Piper team knew that they had to produce a new, modern entry to mid-market level aeroplane as soon as possible in order to compete with Piper’s true rival, the only other major aircraft company that was actively and successfully servicing that segment of the GA market, Cessna.

Immediately upon the introduction of the allmetal Cessna 172 in 1956 Piper knew that its internal evaluations regarding the obsolescence of fabric-covered aircraft were indeed valid and that their then single-engine star, the Tri-Pacer, had already been eclipsed. While the exceptional Comanche had, in fact, turned out to be highly competitive in the high-end GA niche, giving the equally exceptional Beechcraft Bonanza a good run for the money, Piper well understood that in order to compete in and command a viable position in the entry/ middle price market it needed to offer something new,

Ribstitching a fabric covered Tri-Pacer’s

wing before doping — one of this process’s many labour-

intensive steps.

something that would give potential owners an attractive alternative to Cessna’s popular 172.

Looking to produce a four-seat design which would be simpler and which could be produced less expensively than the complex, retractable gear, constantspeed propeller Comanche, Piper also knew that in order to be competitive in the lucrative trainer market they needed to build a replacement for the twoseat Colt which had been commercially greatly overtaken by the all metal Cessna 150. If these two needs could be resolved by one overall design, so much the better.

A product of the prosperity and economic confidence of the late ‘50’s in the United States was a wave of new student pilots. Flight schools and clubs were popping up at virtually every local airport and business was very brisk. Since its introduction in 1958, the all-metal, twoseat Cessna 150 had become by far the most popular aircraft in this burgeoning trainer market. As the last of the J-3’s, Aeronca Champs and other similar tail-wheel (then called “conventional undercarriage”) aircraft began to disappear from attrition mostly due to tailwheel induced taxiing and landing accidents, they were quickly being replaced by the tricycle undercarriage 100 hp Cessna 150 and, to Piper’s disappointment, to a far lesser extent the 108 hp, two seat version of the old TriPacer, the fabriccovered Piper Colt. It was understood that the old tailwheel trainers did not offer as relevant a training experience to student pilots who looked for-

1959 Cessna 150

1961 Cessna 172

1960 Piper PA-22-108 Colt

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1956 Cessna 172 interior

1956 Cessna 172

ward to soon flying higher performance aircraft, all of which had tricycle undercarriages.

Also, unlike the J-3, etc. where the student and instructor sit in tandem, in the new trainers the instructor and student sit sideby- side, facilitating communication as well as increasing the confidence of the student and making it easier for the instructor to demonstrate maneouvers and to teach the lesson. Additionally, and most significantly for FBOs, flight schools and clubs, with the advent of these new tricycleundercarriage trainers, ground loops and nose overs whilst landing as well as collisions whilst taxiing became a thing of the unmourned for past.

The Tri-Pacer shared the same market as Cessna’s 172; however, except that they were both high-wing, four place aeroplanes of similar power, they actually shared few similarities, particularly with regard to construction and appearance.

Firstly, the Tri-Pacer was fabric covered whilst the 172 was all metal. The higher maintenance cost of a fabric covering as well as the anticipated expense of an inevitable fabric re-covering was a strong market motivator toward the allmetal l72.

Secondly, the Tri-Pacer’s frame has many steel components within which can and do rust, and eventually cause major repair headaches. The 172’s stressed-skin covered airframe is sturdy, lowmaintenance and is all aluminium.

Thirdly, the Tri-Pacer, which had been introduced in 1951 was distinctly showing its age and was, in fact,

something of an anachronism by the beginning of the following decade. Its foreshortened appearance gave it a somewhat stodgy look and sitting seemingly precariously upon its closely spaced undercarriage, it garnered the unfortunate nickname “Flying Milk Stool”. Piper had to face it; the Tri-Pacer just didn’t imply a clear and definite sense of modernity as surely as the Cessna 172. Taking everything into consideration, Piper saw the writing on the wall.

Ironically, the Tri-Pacer’s performance is excellent, competing well with and in some instances beating the newer Cessna 172. The 160 hp Tri-Pacer climbs at approximately 800 fpm loaded at or near MGW with a top speed of 123 k (141.5 mph) and a 75% cruise of 117k (134.5 mph) at 7,500’. Its useful load is 890 lbs., and its take-off and landing performance as well as its slow and departed flight performance is overall better than the 172’s. The Tri-Pacer is more responsive than the Cessna 172 and many pilots have found it to be more fun to fly. Nevertheless, by the end of the 1950’s the more modern-looking Cessna 172 was running away with the middle GA market.

Before 1961 one might well be excused for thinking that with the exception of the low-wing twin-engine Apache, the Comanche and the Pawnee crop-duster that Piper leaned heavily towards the production of high-wing aeroplanes. After three decades and thousands of fabric-covered, highwing Pipers this trend changed dramatically, marking the end of one era and

1959 Piper PA-	1967 Cessna 172/Skyhawk	1960 Piper PA-25-235
22-150 Tri-Pacer		Pawnee crop duster

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AN AEROPLANE FOR THE REST OF US

Left: Fred Weick’s brilliant and innovative 1936 Erco 315CD “Ercoupe”

Center: Very rare photograph of experimental retractable Ercoupe

Right: Fred Weick with his Ercoupe Noteconstant speed propeller with antiicing boots

John W. Thorp

the beginning of a new one when the first of the all metal low-wing PA-28-150 and PA-28-160 Cherokees were introduced to replace the Tri-Pacer and the Colt which were then withdrawn from production.

CREATING AN AFFORDABLE LEGEND

In 1957, Karl Bergey, Assistant Chief Engineer at Piper’s brand new Vero Beach facility which was built to design, test and ultimately manufacture the Cherokee, led the team of engineers and designers whose task it was to create an aeroplane that would establish the new, modern Piper Aviation in the present and secure it well into the future. Pug Piper sought to create a small team of engineer/designers who had reputations for having the foresight and imagination to create something new. To that end, Pug Piper’s friend, the talented, progressive and imaginative 1928 Collier Trophy winner, Fred Weick was invited to join the team.

Weick was one of the first American aeronautical engineers who had, among other things, worked closely with the United States Postal Service in the early 1920s to establish and to develop the U.S. Air Mail Service. In 1925, whilst an engineer working for the National Advisory Committee for Aeronautics (NACA), Weick was the chief design engineer and responsible for developing streamlined cowlings to improve aerodynamic efficiency while enhancing engine temperature control. He also helped to design the first full-scale propeller wind tunnel.

By 1936, as chief designer at ERCO, Mr. Weick designed the revolutionary ERCO 310, better known as the “Ercoupe”, designed to be virtually stall and spin-proof with integrated rudder and aileron controls (no rudder pedals), a crosswind resistant undercarriage, and one of the first aeroplanes designed with a tricycle undercarriage.

Both William Piper and his son, Pug greatly admired the extraordinary talents of the brilliant and prolific aeronautical engineer/designer John W. Thorp who agreed to join the team. In the course of creating the Cherokee this stellar design team found Thorpe’s keen aeronautical mind to be a great and powerful resource. The design of the Cherokee ultimately greatly benefited from many of John Thope’s ideas and from his excellent past designs. In particular, the team incorporated many features from Thorp’s amazingly ahead of its time, the 1945 allmetal T-211.

A MOST DELICIOUS WING

The first thing that Pug Piper told his team was that the new aeroplane would have a low wing for a new Piper look and so that drag producing struts of any kind could be avoided. He wanted Piper Aviation to build on the excellent reputation that the low-wing Comanche had already established and envisioned an aeroplane that would look and be as entirely different from the Cessna 172 as possible.

1945(!) Thorp “Skyshooter” T211 showing the true genesis of the Cherokee design. Note the Hershey Bar wing, undercarriage configuration, corrugated skin rudder and the stabilator with anti-servo tab.

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An all metal, cantilever 160 sq. ft. (15.14 m²), 30’ (9.2 m) span, 5’ 3” (1.6m) constant-chord (non-tapering) wing, popularly called the “Hershey Bar” wing because of its similarity in shape to that most famous rectangular confection, became the basic platform upon which this new aeroplane was built. This wing’s aspect ratio (span divided by chord) is on the low side at 5.63. This was not a problem or a new situation at Piper. The immediate predecessors of the Cherokee, the socalled “short wing” Pipers, the Vagabond, the Clipper, the Pacer, the Tri-Pacer and the Colt which the Cherokee series of aircraft was to replace had even lower aspect ratios. By comparison Cessna 172’s aspect ratio was 7.448.

It was a deliberate design choice to raise the new Cherokee’s wing’s aspect ratio a bit from the shortwinged Pipers in order to increase its Cl (coefficient of lift) and thereby its efficiency. Up to a point, a higher aspect ratio wing promotes better high altitude cruise, climb and glide performance. However, a wing with a lower aspect ratio has at least one advantage — it has a higher critical angle of attack (Alpha), i.e., the positive Alpha at which it will stall; additionally the stall itself tends to be gentle. The old short-wing Pipers were not very efficient power-off gliders (I recall that the Colt, particularly, glided like a stone); however, they were extremely forgiving at low airspeeds and in extreme departed flight attitudes. They could, with sufficient power applied, seem to “hang on their propellers” with their noses sitting way up in the air whilst flying at very low airspeeds. It had been Fred Weick’s lifelong goal to build aeroplanes such as the Ercoupe that were easy to fly and by extension, safe. All agreed that forgiving flight characteristics would be a most attractive feature to the low-time pilots and FBOs that were Pipers commercial target.

The team designed the Cherokee’s wing to be mounted at an angle of +2º to the fuselage’s longitudinal datum line in order to permit a distinctly nose-down attitude, thus promoting good forward visibility for the aeroplane’s occupants on the ground and in flight, and

Aspect Ratio - wing span (tip to tip) divided by average chord

reducing P-effect (combination of twisting slipstream* and induced propeller yaw in the opposite direction of the turning of the propeller when at positive Alpha) during the takeoff run. They wanted to improve upon the Comanche’s distinctly nose-high stance on the ground which creates a good deal of P-effect on takeoff requiring lots of right rudder to keep it on the centreline.

*For what it’s worth, this writer does not hold very much with the theory of a twisting slipstream as a major P-effect force for a number of reasons to lengthy to go into here. Also, remember, P-effect operates in the yaw axis, torque in the roll axis.

Being a low-wing aeroplane, the Cherokee’s overall vertical centre of gravity (C.G. v) is low, however, it is necessarily at a point above its low wing. This promotes poor stability in the lateral (roll) axis while enhancing maneouverability. While enhanced maneouverability is a good thing in a fighter, aerobatic show or sport aeroplane, it is not necessarily so good in an aeroplane

Left to right:

1)Piper PA-16 Clipper

2)Piper PA17 Vagabond

3)Piper PA-22 Pacer (Tri-Pacer in red above) 4)1964 Piper PA-28-140 showing original “Hershey Bar” rectangular wing

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AN AEROPLANE FOR THE REST OF US

Angle of Attack (AOA) also called “Alpha”

P (propeller) -Effect

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Hershey Bar Cherokee showing 7 degrees of dihedral Cessna 172 showing 3.5 degrees dihedral

designed to be used for training new pilots and for comfortable and easy touring. To create good lateral stability a lowwing aeroplane requires dihedral, more dihedral than is required for a high wing aeroplane. Also, a low wing aeroplane requires greater dihedral to provide for adequate wingtip clearance when on the ground and when a wing may be lowered during a cross-wind landing. Accordingly, the Cherokee’s low wing has 7º of dihedral which gives it very good lateral stability which is especially welcome on long trips and when in mildly turbulent conditions.

The vertical centre of gravity (C.G. v) of a high-wing aeroplane is also low, but at a point below the wing which promotes good stability in the lateral axis. This means that less dihedral is required for high-wing aeroplanes. Accordingly, the high wing Cessna 172’s dihedral is only 3.5º.

Dihedral causes a self-levelling force to occur when the aeroplane is displaced from level in the roll axis. As any force, such as turbulence, begins to roll an aeroplane from level, the downward moving wing’s Alpha increases, creating lift. In addition, the lowered wing assumes a more horizontal attitude than the higher wing and, concurrently, the lower wing creates more lift because of this, as well. Both of these effects tend to roll the aeroplane back towards level.

Of course, too much dihedral can lead to a reduced roll rate as well as over-sensitivity in turbulence, making for an uncomfortable ride in all but the calmest air. Compensating for its generous dihedral, the rectangular wing Cherokee’s large and most effective ailerons produce a rapid roll rate which is faster than that of most GA aeroplanes. This is due in part to the reduced lateral damping effect of the low aspectratio, slightly foreshortened Hershey Bar wing. The Cessna 172’s wingspan is 6’ greater than that of the rectangular wing Cherokee and, accordingly, it creates more lateral axis damping which somewhat reduces its roll rate. Accord-

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ingly, the Cherokee is maneouverable, laterally stable and rides quite well in all kinds of turbulent air. Accordingly, it seems that the Cherokee’s wing’s dihedral, like so much else about this aeroplane, appears to be just right.

Adverse yaw is the tendency for an aeroplane’s nose to yaw in the opposite direction of bank and is caused by the rising wing pulling back because of increased induced drag created by lift. To reduce adverse yaw, virtually all modern aeroplanes, including the Cherokee, have ailerons which are differentially rigged; that is, there is more upward aileron movement than down, causing there to be less liftinduced drag in the rising wing and thereby reducing its tendency to yaw the aeroplane away from the turn.

To simplify the Cherokee’s construction and to keep costs to a minimum, a few new wing mounting techniques were incorporated. As mentioned, the Comanche’s left and right wings are joined in the middle in the factory making the wing one piece. The entire wing is then attached to the bottom of the fuselage, the main spar being bolted to a receiving 3-sided box. This construction makes for a very strong +7g wing, perhaps stronger than necessary in a non-aerobatic GA aeroplane. It is also quite costly. Piper’s team looked for another way to mount the wing to the fuselage that would be strong enough but also simple and economical.

What they came up with is this: The Cherokee’s wings are attached individually to each side of the fuselage. Each of the Cherokee’s wings’ main spar is in the form of an “I” beam which is inserted into to a box beam built as a part of the fuselage frame located under the rear passenger’s seat, spanning the width of the fuselage. Once the wings’ spars are seated within the box beam they are secured with eight heavy bolts essentially making the wing one piece. The inner ends of the forward and aft wing subspars are bolted to the fuselage through matching mounting plates in the wing root and on the

fuselage. This greatly simplifies assembly as well as making major wing repairs or replacement less expensive. An additional plus is that this method of mounting the wings separately permits the use of a much shorter shipping crate, thus saving transportation costs of the unassembled airframe.

Piper reports that it has thoroughly tested the Cherokee’s wing mounting system, running at least 480,000 load and unload cycles with no damage to the wing mounts.

The Cherokee’s constant-chord, rectangular wing planform did not, however, come about without some friction and dissent within the design team. “Pug” Piper wanted tapered wings as on the Comanche, both for aesthetic and aerodynamic reasons. Both Thorp and Bergey also initially thought that a tapered wing for the new aeroplane would be best even though Thorp, in particular, had been a long-time, outspoken advocate of non-tapered wings for GA aircraft (see the Thorp T-112).

Supermarine Spitfires showing elliptical wings

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The team considered a tapered wing for three basic reasons:

At first, Karl Bergey was, as was his boss, Pug Piper, in favour of a tapered wing for the new design which he said more closely emulated the commonly accepted ideal wing plan form, the ellipse, as found on R. J. Mitchell’s spectacular and beautiful Supermarine Spitfire. Piper, Bergey and Thorp initially agreed that an elliptical wing produces less overall lift-induced drag than a rectangular wing and is quite efficient.

The second argument for a tapered wing was that since the tapered outer part of the wing has a shorter chord it has less overall area than the inner part of the wing. This reduced wing area would cause less upward bending pressure on the root of the wing when in flight than if it the chord was constant to the tip. With less bending to worry about, a simpler, lighter inner wing structure could be designed.

The third and perhaps the most practical reason for a tapered wing (from a marketing perspective at least) was that they look sleek and aerodynamically “correct”. Always most aware of the importance of marketing with regard to of any commercial product, Pug Piper, as had his father so many times before him, found this argument to be highly persuasive.

It looked like the Cherokee was going to have a tapered wing similar to the Comanche’s when Thorp began to advocate for a rectangular wing instead. After ruminating about the issue for a while and he began to discount the structural argument for a tapered wing. He reasoned that the difference in the structural weight of a tapered verses rectangular wing of the same size was too small to consider. Combining this with his aerodynamic analysis he said that aerodynamic scale effect makes it possible to use a smaller rectangular wing (rather than a larger tapered wing) for a given stalling speed. He went on to explain that therefore the tapered wing, though possibly inherently slightly lighter, must ultimately be of greater span in order to provide equal wing area to that of the un-tapered wing, thereby erasing any weight saving.

As to the elliptical wing planform theory, Thorp rejoined Piper and Bergey’s opinions and held that there was more to the issue than that socalled “ideal”.

He argued that while the total of aerodynamic forces indeed seemed to favour an elliptical wing form, where the wing’s chord was shorter near and at the tip of such a wing, or in any tapered wing seeking to emulate an elliptical form, the Reynolds Number (RN)* is similarly lower near and at the wing tip, therefore causing a great propensity for the wing tip to stall before the rest of the wing.

Reynolds Number =

V(speed) x L (length of chord)

Kv (kinematic viscosity)

Without getting too deep into the math of this formula, the kinematic viscosity (Kv) is a measure of the

“stickiness” of the air. For simplicity you can use the value 6327 for the Kv of air at the standard temperature of 59 degrees Fahrenheit at Sea Level. The speed value is in feet per second and the length is the chord of the wing in linear feet.

The Reynolds Number is an essential measurement of wing/aircraft performance and if you are a serious student of aerodynamics you will want to know a good deal about it.

The others recognized Thorp’s argument to be sound because, as is well-known, where the RN is lower the maximum Cl is necessarily lower, creating less lift at any given airspeed as compared to any other part of the wing where the chord is longer. Accordingly, it follows that where the maximum Cl is smaller, that part of the wing must stall first.

Thorp further argued that the relatively small size of GA aircraft’s wings and their relatively slow takeoff and landing speeds exacerbates the tip stall problem in a tapered or elliptical wing as the outer wing’s RN is therefore even lower. Additionally, a tapered or elliptical wing is more readily likely to have reduced aileron effectiveness. While it makes sense that the aileron on a tapered wing may be less effective being mounted at the tapered portion of the wing which has a shorter chord and thus a lower RN causing lower efficiency and

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Some fixes for tip stall

Piper PA-28-161 showing semitapered wing PA-28-181 Archer showing semitapered wing

a lower maximum Cl; it is also true that the tapered wing’s outer section produces less aerodynamic lateral damping force in a roll than does a constant chord wing. Therefore, all else being equal, with properly designed ailerons a tapered wing could have as fast or a faster rate of roll than a constant chord wing of identical area and span.

As a tapered wing for the Cherokee was being seriously discussed, the various known “fixes” for tip stall were considered. The commonest of these is wing twist or “washout” where the outer portion of the wing’s trailing edge is built to ride slightly higher than the leading edge (producing lower local static Alpha). Additional preventative measures for tip stall are aerodynamic devices which are attached and/or added to the wing such as drooped or enlarged leading edges, stall strip at leading edge, more greatly cambered (curved) outerwing airfoil sections, fixed or automatic leading edge slots or slats, and downward curved wing tips.

While these fixes do help the problem to some degree, they all add complexity, and/or weight to the wing and all produce additional airspeedrobbing drag which tends to negate the advantage that the tapered wing was supposed to deliver in the first place.

In final analysis, Thorp, Bergey and Weick (who admired Thorp’s sound reasoning on the matter) agreed that nothing of any value, especially airspeed, would be gained by incorporating a tapered wing, and admitted that, in fact, the tapered wing in its pure “unfixed” form was more prone to tip stalls and spins. They agreed that a rectangular wing with a few degrees of washout would

be as or more efficient as an elliptical or tapered wing without any of the tapered wing’s attendant tip-stall problems and without the complexity and additional expense of building a more complicated tapered wing structure.

The team finally agreed upon a rectangular, constantchord, “Hershey Bar” wing for the Cherokee, which indeed proved to possess a high degree of cruise efficiency, near to ideal lift distribution characteristics, and which is highly stable at low airspeeds, near-stall, stall and departed flight conditions.

Always seeking to improve the Cherokee, in 1969 an extension of the wing span was proposed in order to improve load carrying ability and rate of climb. However, preliminary tests showed that a longer wing would necessarily increase positive bending pressure on the wing root and inboard wing structure requiring an entirely new and more robust inner wing design which would necessarily add to manufacturing costs. The idea was tabled for the time being.

In 1973 Piper revisited the Cherokee’s wing design and decided to go with the original idea of a tapered wing. While Thorp and Weick’s original theories regarding tapered vs. rectangular wings were correct and had been well-proved, much to the dismay of many within and without Piper Aviation, a new, tapered wing was approved for the PA-28-150.

This aeroplane also incorporated a few other upgrades, improved wing fairing and seals and was renamed the PA-28-151 “Warrior”. Thereafter, if a Piper aeroplane has a “1” as its last number, as in PA-28-151, etc. it has a semi-tapered wing. The “Warrior” broke Piper’s tradition which began in 1954 with the twin engine Apache of exclusively naming its aircraft after the English language names of Native American tribes, and began a new tradition of also naming aircraft using words such as “Tomahawk”, “Arrow”, “Archer”, “Papoose”, etc. that closely suggested and alluded to that noble culture.

The new PA-28-151 was very similar to the old PA-28- 150, except for its tapered wing, which is actually only tapered from the mid - span point to the tip on each side and therefore ought to more properly be called “semitapered”. The new wing was also increased by 5’ in span to make up for the decreased area of the tapered

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section, as Thorp had said would be necessary. The increase in span raised this new wing’s aspect ratio to 6.66 from 5.63 and likewise slightly raised its Cl. The product of the additional span is a slight gain in rate of climb and high altitude cruise speed and a flatter power-off glide.

Some of these performance gains were initially credited solely to the new semitapered wing itself; but upon closer inspection and analysis it was discovered that they were at least partially, if not mostly due to the improved wing/fuselage seals and fairing incorporated in the PA-28-151. At the same time, the semi-tapered wing’s increased aspect ratio, which in addition to its said performance enhancements also reduces the effective range of Alpha at which the Cherokee may fly before stalling. This causes the semi-taper wing Cherokee’s Alpha at the stall to be lower than that of the Cherokee with a rectangular wing.

In 1976 the PA-28-180 was re-designed with a semitapered wing becoming the PA-28-181 “Archer”; and by 1979 all Piper singleengine aircraft had received semitapered wings, all of them, accordingly, both gaining and losing therefore as mentioned above.

As far as performance goes between the Cherokee with a rectangular or semi-taper wing, all else being equal and without wheel pants, from sea-level to approximately 6,000’ the rectangular wing is actually faster than the semi-tapered wing. However, as altitude increases past 6000’ the rectangular wing loses airspeed more rapidly. As mentioned, the semi-taper wing Cherokee has a slightly better rate of climb and also a flatter glide. Flatter glide is good in itself, but has a down side in that the semi-tapered wing Cherokee is more sensitive to airspeed when landing than is the rectangular wing. This means that if there is any amount of excess airspeed at the flair, the semi-tapered wing tends to float a while before touching down where the rectangular wing settles down more quickly and with less float.

Whatever the reasons may be, the semi-taper wing’s performance increases are very slight. This writer, having flown both versions of Cherokees prefers the rectangular wing over the semi-tapered wing for its speed, sprightlier handling and its excellent landing, low-air- speed and stall characteristics; or perhaps it’s also out of a sense of tradition and nostalgia.

Hershey Bar vs. semi-tapered wings

FOILED AGAIN

After careful analysis, the team selected the rather thick at 15% NACA 652-415 laminar-flow airfoil as it was highly efficient at the airspeeds and altitudes at which the Cherokee was expected to cruise while still preserving good low airspeed characteristics and a most gentle, benign stall.

This airfoil is an NACA “6” series airfoil, has its area of minimum pressure 50% of the chord from the leading edge, maintains low drag at 0.2 above and below the lift coefficient of 0.4, has a maximum thickness of 15% of the chord, a= 0.5 means that the airfoil maintains laminar flow over 50% of the chord.

Despite the NACA numbers, the Cherokee’s wing’s thickest point is actually closer to 40% back from the leading edge.

Just a quick word or two about airfoils and what a “laminar flow airfoil” is. The wing’s airfoil is its crosssection shape from leading to trailing edge and is primarily and most importantly an air diverter*. Among other things, the airfoil diverts the air through which an aeroplane’s wing travels downwards at the wing’s trailing edge so that lift may be generated (see Newton’s Third Law of Motion). In order to do this the “boundary layer”, which is the very thin, viscous layer of air closest to the surface of the wing, must adhere to the wing and not become turbulent or detach from the surface of the wing. As long as the boundary layer adheres smoothly and uninterruptedly to the surface of the wing, the wing will continue to divert air downward at the trailing edge and thereby produce lift.

*There are many theories of lift, some traditional, some imaginative and seemingly intuitive. However, in recent years most of the traditional theories have been discredited as they were found to be flawed, entirely improbable or simply wrong as aeronautical knowledge and understanding has progressed. It is most likely that there are numerous ways in which a wing produces lift. The airfoil as a downwash “air diverter” at the trailing

Cherokee wing root without flap or aileron, “wet wing” fuel tank removed (leading edge facing left)

This is the Cherokee’s airfoil straight black linechord curved grey line - mid line or mean camber line

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edge is and has for many years been what this writer thinks is the most probable correct theory. Of course, the true scientific mind must always be open to new facts and disclosures. This writer awaits with great interest what is yet to be discovered.

Also, a smooth and adherent boundary layer produces minimum pressure and/or parasite drag enabling the aeroplane to fly faster for any given amount of power. Slight micro-turbulation in the boundary layer actually increases its adherence to the surface of the wing; but, when this turbulation becomes more severe and becomes a turbulent flow, lift is reduced and pressure drag increases. If this turbulence becomes too severe, which typically happens at critical positive Alpha, the turbulent boundary layer detaches from the surface of the wing creating random eddies and vortices causing considerable parasite and pressure drag to be produced. Upon boundary layer flow separation from the surface of the wing the former downward diverted air flow ceases and, concurrently, the wing ceases to generate lift. This is the “stall”. An airfoil designed to produce maximum uninterrupted, adhesive boundary layer flow at the surface of the wing and minimum drag is called a “laminar flow airfoil”.

Laminar Flow

NACA NUMEROLOGY

The first number, “6”, of NACA 652-415 indicates that this is a NACA “6-series” airfoil. The second number, “5”, indicates the position in percentage x 10 of the chord (leading to trailing edge) where minimum pressure occurs — here indicating the 50% chord position. Minimum pressure usually occurs at the thickest part of the airfoil.

The subscript “2” indicates that this airfoil’s drag coefficient approximates its minimum value between plus or minus 0.2 of the airfoil’s design Cl. The NACA 65(9)-415 airfoil which is a later refinement of the NACA 652-415 has been used in the Cherokee as well, the only difference between it and the NACA 652-415 being that in the latter airfoil the airfoil’s drag coefficient approximates its minimum value between plus or minus 0.9 of the airfoil’s design lift coefficient.

The number “4” indicates the lift coefficient in tenths; here, 0.4.

The last two numbers, “15”, indicate the wing’s maximum thickness as a percentage of the chord; here, 15% of the chord.

A laminar flow airfoil is typically designed so that its thickest point is usually at approximately 50% of the chord. A normal airfoil’s thickest point is usually at approximately 25% to 33% of the chord. The laminar flow airfoil shape combined with a very smooth wing surface best promotes a smooth and adherent boundary layer. The North American P-51 “Mustang” was the first mathematically designed aeroplane and its wing was the first to be deliberately designed with a “laminar flow” airfoil, however, even a very slight ripple or bump in or on the surface of the wing can prevent the true laminar flow effect. Despite all good intentions the P-51’s wing surface is not sufficiently smooth and uninterrupted nor was it optimally built or usually sufficiently maintained in the field to promote true laminar flow. The Cherokee’s wing surface, however, is actually far smoother and if kept scrupulously clean, promotes a stable, adherent boundary layer very well.

A salient characteristic of the Cherokee’s airfoil is that it has a fairly flat Cd (Coefficient of Drag) curve and thereby looses lift very slowly as the stall is approached. Unlike many others, this airfoil does not possess a single critical angle of attack (positive Alpha) at which it will stall. The NACA 652-415 airfoil flies within a fairly broad range of positive Alpha and does not break sharply at the stall unless very aggressively forced into an extreme positive Alpha condition called a “deep stall”. Spins are likewise very difficult to enter unless aggressively pursued. Additionally, the Hershey Bar wing’s low 5.63 aspect ratio helps to promote the Cherokee’s distinctly anti-stall/spin behaviour. That these gentle stall/spin characteristics were incorporated in the Cherokee’s design is no coincidence and very much in keeping with Fred Weick’s life-long design practices, particularly with regard to his Ercoupe design which, as mentioned, was

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Simple Polar showing relative differences between high and low aspect ratio wing (here - AR)

specifically designed to be virtually stall and spin-proof. Those who have flown a Cherokee will surely attest to its remarkably benign handling at low airspeed and its reluctance to stall or spin. In fact, at one “g” with power off it does not really break at all at the stall, but merely oscillates gently forward and aft while descending rapidly, which is the only indication that the wing has in fact stalled. Pilots generally find the Cherokee to be reluctant to stall with power on; although in this configuration the stall break may be a bit more definite with the left wing falling due to engine torque at high power. With power on the Cherokee rarely loses aileron control. This is a sharp contrast to the Cessna 172 which loses aileron control quite readily when near or at the stall. These stall characteristics apply to both semi-tapered and rectangular wing Cherokees, the rectangular wing being the more benign and reluctant to stall due to its

higher Alpha before stall due to its lower aspect ratio. Because the Cherokee’s NACA 652-415 laminar-flow

airfoil’s thickest point is near the wing’s mid-chord, approximately 40%, the main wing spar is located farther aft than is possible with non-laminar airfoils. Accordingly, as the main wing spar runs longitudinally across the wing at its thickest point, its profile is deep and great strength is gained therefrom. Also, the location of the main spar so far aft locates it under the rear passengers’ seat, permitting the cabin floor to be flat and unobstructed.

KEEPING THINGS STABLE

Following the successful Comanche design, instead of the usual horizontal rear flight surface consisting of a fixed stabilizer with a hinged elevator, the Cherokee incorporates a one piece, allflying “stabilator” with an anti-servo tab (also called an anti-balance tab) upon which, not likely coincidentally, John Thorp holds the patent. A one-piece (i.e. non-hinged), all moving stabilator pitch control surface produces less drag when the

surface is displaced and is more efficient than a conventional fixed stabiliser and hinged elevator. Accordingly, it may be of less overall area than a similar conventional fixed and hinged pitch control surface. Accordingly, the early Cherokees’ stabilator was designed to be approximately two feet shorter in span than later ones making these Cherokees with shorter stabilators slightly less effective in pitch control, particularly at slower airspeeds.

An anti-servo tab is located at the trailing edge of the stabilator, similar to a trim tab; however an anti-servo tab is mechanically linked to the stabilator to move in the same direction as the stabilator when the stabilator is displaced by the pilot. This provides a proportional opposing force to the displaced stabilator, thus avoiding negative aerodynamic stability (the tendency of a balanced, moving, aerodynamic surface to deflect further as it is displaced from neutral) and which, by increasing the load on the stabilator as it is displaced, prevents oversensitivity in the pitch axis control system at all airspeeds.

In the Cherokee pitch trim is controlled by changing the angle of the entire stabilator and anti-servo tab. At the time that the Cherokee was being designed the allflying anti-servo stabilator was already a well-proved, smooth and highly efficient pitch control system which possessed the additional properties of being lighter and, as mentioned, producing less overall drag than

Cherokee showing stabilator and anti-servo tab

An antiservo tab attempts to streamline the control surface and is used to make the stabilator less sensitive by opposing the force exerted by the pilot.

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How a stabilator with anti-servo

tab works

the usual hinged stabilizer and elevator. A stabilator/ anti servo tab horizontal surface very similar to that which was incorporated in the Cherokee appeared on John Thorp’s 1945 T11 and T211. While Thorp’s original design for the stabilator was innovative and effective, it was also a bit complicated as to linkages and such. Ever seeking to economise on production costs, Piper’s Assistant Chief Engineer Karl Bergey modified Thorp’s system and was able to simplify it while still bestowing its essential benefits on the new aeroplane.

Speaking of pitch trim, early Cherokees followed Piper’s unique method of elevator trim control, a horizontal hand-crank and position indicator located in the ceiling between the front two seats. Tri-Pacers, Colts and the first Comanches have the same control. It works fine except that even though it is well-marked, many pilots (me too) have a devil of time remembering which direction to turn the handle for up or down trim. BTW, it’s clockwise for up and anti-clockwise for down.

SWEPT AWAY

We might as well get it out of the way here — the swept back rudder and fin — does it serve any useful aerodynamic purpose as opposed to a straight tail or was it merely intended to sweep customers off their feet with a sweeping new design? (apologies)

Piper had incorporated a swept vertical tail on the 1958 Comanche, which this writer believes is the first time such appeared on any mass-produced GA aeroplane. The Beechcraft Debonaire with its swept rudder and fin was not introduced until 1960. Having innovated this feature, Piper made it a priority to incorporate it as a signature design on its next and subsequent Piper aeroplanes. In any event, the aeroplane that Piper was most competitive in the GA entry/middle market, the 1960 Cessna 172A, now had one. In the late 50’s a swept vertical tail on a GA aeroplane was new. It certainly looked modern and streamlined and suggested the tail surfaces of jet fighters and all. The marketing strategy went something like this: Everyone knows that jet fighters go fast and that they have swept back surfaces; so, if your Piper has a swept back rudder/fin similar to a jet fighter, well then, it ought to go fast as well, right? Of course, the swept surfaces on jet fighters have much to do with trans-sonic and super-sonic flight which Comanches, Cessnas and Cherokees, etc. have little to worry about. For all of that did the swept rudder/fin on the Comanche, any of the Cessnas or, more to the point, the Cherokee enable any of them to fly faster? No, knot at all.

From a strictly aerodynamic perspective a sweptback rudder, its uppermost portion anyway, is located slightly farther rearward than a straight rudder mounted in the same position. This slightly moves the rudder’s CP (centre of pressure) rearward and increases the uppermost part of the rudder’s moment arm which therefore ought to increase its effectiveness to a small degree.

Others have postulated that the swept back fin/rudder is actually less effective and that it somewhat compromises directional stability and spin prevention. It may be, however, that with regard to this it was an earlier straighttailed 172 which was compared to a 1963 or later swept-tail Cessna 172/Skyhawk with “Omni-Vision”

. If so, it is more likely that the cause of any perceived reduced rudder/fin ineffectiveness, etc. was not necessarily the swept vertical surface but was actually the later

Piper PA-28-160 Cruiser showing
swept-back fin and rudder	1967 Mooney M-20C Ranger	1962 Mooney M-20C Ranger

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aircraft’s cut - down rear fuselage which provides for the “Omni-Vision” rear cabin window, and that the reduced side area of the fuselage behind the C.G. is the real culprit for any directional stability or spin issues.

Also, if the aeroplane is banked a displaced sweptback rudder will tend to couple with both the aircraft’s pitch axis (as usual) and also positively to greater than usual degree with the aircraft’s roll axis. Accordingly, a swept forward displaced rudder will couple negatively with the aircraft’s roll axis.

What a swept rudder/fin actually does as compared to a straight one with regard to relatively lowspeed GA aircraft might be able to be measured in a wind tunnel or by a very sensitive set of in-flight instruments, but this writer is not aware that any such study has been conducted. Having often flown versions of the same aircraft (C-172 and 182) with both straight and swept tails this writer has not noticed any appreciable difference in the performance and handling thereof that might be due solely to the rudder/fin configuration. Taking everything we know into consideration it seems that a reasonable conclusion regarding this matter is that the swept back rudder/fin on GA aeroplanes is nothing more than an eyecatching marketing tool which is, after all, still a legitimate reason for its existence.

One last, possibly definitive note on this subject; Al Mooney ostensibly designed the Piper Comanche with its swept back rudder/fin. However, all of his designs for Mooney Aircraft incorporate rudder/fins that famously sweep forward.

COMFORT AND ECONOMY

Comfort: One of the important issues that Piper’s design team had to consider was the creation of a new aeroplane that would cost far less to build and thereby be able to be sold at a much lower price than the Comanche. While the team considered that designing an aeroplane that was less costly to build would not be so arduous a task (Weick and Thorp had been designing inexpensive to build aeroplanes for decades), simultaneously providing the new aeroplane with a cabin as or more comfortable than anything in its class was a bit more daunting.

Cabin size and particularly cabin width is a tricky thing to consider when designing a small aeroplane. Every extra inch expands the frontal area and, accordingly, increases parasite and form drag, resulting in a higher Cd and reducing performance for available power across a broad spectrum.

Piper’s target competition, the Cessna 172’s cabin is a fairly cosy 39 ½” wide. This is a relatively tight fit for full - sized adults, 1/2” narrower than Piper’s previous singleengine flagship, the Tri-Pacer, with its snug 40” cabin width. In years past this writer flew many pleasant hours in Tri-Pacers and somehow does not remember that it was such a tight fit; but then that was many years ago and this writer was then, let’s say, a bit smaller.

The planned cabin width of the new aeroplane was at first to be a generous 44”, the same width as their then

single-engine flagship, the Comanche. However, Piper felt that its new, more economical aeroplane ought not compete so closely with its flagship aeroplane and it wanted to reserve to the Comanche just a bit more cabin comfort than its less expensive brother. Accordingly, the Cherokee, as the new aeroplane was finally named, would have a 40 1/2” wide cabin, still an inch wider than its closest competitor, the Cessna 172.

Another way that the Cherokee was designed to increase cabin space while keeping construction cost low was by utilizing the fuselage’s external belly skin, strengthened with external stiffening members, as the cabin floor. This was inexpensive, light and required fewer parts than did many contemporary designs. This ingenious design treatment added cabin headroom without the need to expand the outer dimensions of the fuselage and thus increase parasite and form drag.

In addition to cabin size, Piper wanted their new aeroplane to be quieter than its competition. The Cessna 172’s design approach is towards a definite lightness of structure which results in a less noiseinsulated cabin due to the 172 having a rather thin firewall, doors, windows and other structural members resulting in a fairly noisy cabin. Well-understanding Cessna’s design preferences, Piper looked to find a way to gain an advantage by reducing the Cherokee’s cabin noise. This was done by generally using thicker, sturdier structural members particularly in and around the cabin and by placing the engine as far forward as possible without jeopardizing good pitch control balance. This kept the engine’s twin exhaust stacks, which are located near the front of the engine, as far away from the cabin as possible. The upshot is that the Cherokee has a very quiet cabin, not usually requiring headphones for its occupants to converse in flight.

Economy: One of the ways that an aeroplane may be produced more economically is for it to be designed with as few parts as possible. The Cherokee was, accordingly, designed to be extremely simple to construct with much redundancy (i.e., all wing ribs were the same size, identical left and right parts where possible, etc.) as well as having very few complex curves requiring more costly and labour intensive aluminium panel construction, shaping and fitting. Accordingly, the new Cherokee was designed with less than ½ as many parts as the more complex and more expensive to build Comanche. A demonstrative example of this is that the Cherokee uses 1,785 rivets while the Comanche uses more than twice that amount at 3,714. (Yes, I did count them all myself — not)

Another example of intentional simplification is that the Cherokee’s ailerons require ten parts to construct while the Comanche’s ailerons require thirty-six parts. Additionally, and in keeping with his long-held and successful design practices, John Thorp designed all of the Cherokee’s tail surfaces, flaps and ailerons to be as lightweight, simple and thereby less expensive to construct

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Corrugated skin on 30’s -

W.W. II era transport Junkers

JU-52 “Iron Annie”

Piper Cherokee rudder showing corrugated skin

Cherokee unpainted stabilator showing corrugated skin

Cherokee unpainted fuselage and fin showing corrugated skin

as possible by requiring no internal ribs or heavy internal structures within them. This particular weightsaving practice is also found in the designs of many GA aircraft. Stiffness of the Cherokee’s tail surfaces, flaps and ailerons is provided by beaded (corrugated) surface skins, similar to that which was pioneered by and appeared on Junkers aircraft of the W. W. I era and later and which was also largely utilised by John Thorp on many of the aircraft which he had previously designed in order to save weight and to foster simplicity of construction. Piper was familiar with this construction technique as its PA-18 Super Cub’s metal ailerons and flaps are covered with the same kind of corrugated skin for stiffness.

Another partscount, weight and cost saving was the Cherokee’s incorporation of “wet wing” or “integral” fuel tanks formed by the wing’s leading edge structure rather than the usual practice of installing separate fuel cells within each wing. The wet-wing fuel tank maximises the quantity of fuel that may be carried on board while requiring the least amount of wing structure to contain it. Of course, the fuelcarrying part of the wing must be designed and built with great integrity so that all panels, rivets, connectors, etc are leak-proof and will not even slightly separate under flight loads. Possibly the earliest application of wet wing fuel tanks appeared in Fred Weick’s remarkably prescient 1936 Ercoupe.

Another cost and weight saving measure applied to the Cherokee was the innovative and extensive use of inexpensiveto- produce fibreglass parts in place of aluminium for the wing and stabilator tips as well as for the cowling. The use of fibreglass in these areas was also potentially cost-effective for the Cherokee’s owner in the event that these parts were ever damaged and had to be replaced as the vulnerable wing and tail tips and cowling are often the common victims of “hangar rash” and other inadvertent abuse.

Cherokee with “wet wing” fuel tank removed

Cherokee fibreglass wing tips

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WHEELS AND FLAPS

The Cherokee’s undercarriage is tri-cycle with a fully steerable nosewheel, independently sprung but directly connected to the rudder control system which was the same arrangement as was used in the Tri-pacer and Comanche. In early Cherokees the main undercarriage brakes were not operated by toe pedals but by a single, centrally located “Johnson Bar” brake handle, also as in the Tri-Pacer. This system somewhat limited tight, precise ground steering and was not a popular feature. While trying to save on manufacturing costs by using previously designed, well-proved and readily available parts and components from the Tri-Pacer, the fact was that some of these were long overdue for an upgrade. The Cessna 172 had toeoperated brakes on both sets of rudder pedals from the get go which was a notable feature discrepancy. Within a few years and after many complaints Piper relented and installed dual individual main toe brakes for both sets of rudder pedals in the Cherokee, operated by depressing the tops of the rudder pedals individually to turn or both together to slow or stop.

Simple, easy to manufacture and to maintain straight oleo (compressed nitrogen and hydraulic fluid) struts are used throughout. The Cherokee has a distinct advantage over the Cessna 172 in that, as a low-wing design, its main undercarriage is attached directly to the main wing spar providing maximum strength and stability. The Cherokee’s 10’ wide main undercarriage tread provides excellent and stable ground handling under all conditions while the Cessna 172’s main undercarriage which is a pair of steel struts attached to the fuselage, has a tread of a little more than 8’ 4”.

Fred Weick had done a number of advanced undercarriage tests when he was designing the Ercoupe which showed that in a tri-cycle undercarriage the nosewheel was often under the greatest load. He also determined that for operations on grass and on other soft fields that all three tires ought to be the same size. Accordingly, the Cherokee has 6.00 x 6 tires on all three wheels. With regard to the Cherokee’s undercarriage, Piper evidently got it right as pilots have universally praised the Cherokee’s easy, dependable ground handling.

With regard to the Cherokees’ flaps, they are narrow in chord and have a simple, inexpensive up/down linkage with an over-centre lock when up. They are manually controlled by a bar with a release button at its top located between the front seats. The flaps have four positions: up, 10º, 25º and 40º down. Although the rectangular wing’s flaps are more effective than those of the semi-taper wing’s, with regard to flaps the palm must go to the Cessna 172. It has larger and more effective broad-chord flaps, linked so that as they lower they also move rearward out of the wing, increasing their overall area.

Most (me, too) would call the C-172’s flaps “Fowler flaps” because of their rearward-moving, area-increas-

Simple flap - Piper and most GA aircraft

Slotted flap – Cessna and some other GA aircraft

Split flap - Many 1930’s and W.W. II era aircraft

Fowler flap – mostly airliners and

heavy aircraft

ing feature; but in all of the FAA approved official C-172 POHs, Cessna calls them “Slotted Flaps” and therefore that is the only correct answer if you ever are tested on the subject by your instructor or the FAA (you’re welcome). The Cessna’s flaps have slots (openings along the hinge line to allow oncoming air to pass through when the flaps are lowered) which prevent their large size from creating uncomfortable induced rumble, vibration and turbulence when deployed. As it is there is still a distinct audible and visceral rumble when you lower the flaps in a 172, but most pilots don’t mind this much as the flaps are effective and do their job well.

In any event, don’t get too exited by the Cherokee’s 40º down flap position. The Cherokee’s flaps do what flaps are intended to do, but even when fully lowered they perform to a lesser extent than those of the 172. In 1964 when the Cherokee had been out only two years Cessna “upgraded” the 172’s manual flaps to an electric operating system. Whether or not this was intended as a one-up on the Cherokee, this writer does not see this as a positive advance as electrically operated flaps are not really necessary in an aeroplane as light as the 172.

In aeroplanes of this class, this writer prefers the direct control granted to the pilot with the manual flap control. For instance, with a manual flap control the pilot can instantly raise the flaps and thereby dump lift upon touchdown to set the tires firmly against the runway for braking if and when such is desired. A manual flap system allows them to be extended or retracted at any rate the pilot wishes while the electric system extends and retracts the flaps at a fairly slow, pre-set, non-adjustable rate. Also, should the aeroplane’s electrical system fail, manually operated flaps would be unaffected.

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VICTORY — EVOLUTION AND REFINEMENT

Once Pug’s, Weick’s, Thorp’s and Bergey’s design was named, solidified and its exact details determined, the Cherokee was assigned Piper Aviation production model number PA-28 and a prototype for flight testing was built. This first flying Cherokee was essentially what would become the PA-28-160 and was powered by the highly reliable 160 hp Lycoming O-320-B2B engine (later PA-28-160’s would also use the O-320-D2A). Thomas Heffner, chief test pilot for Piper, had the honour of being the first Cherokee pilot to fly the first of over 33,000 Cherokees built on either 10 or 14 January 1960 depending upon what you may read.

The new Piper flew, as it is said, “Right off the drawing board” and everything that its brilliant design team had intended and built in to it was realised. The first production Cherokee, the 160 hp PA-28-160 was type certified on 31 October 1960 and went into production in January 1961. After a short period of pre-release promotion it was released for sale to the public, and soon thereafter it was joined by the slightly less expensive 150 hp PA-28-150. Both of these aeroplanes were instant hits with the aviation public. Flight schools, clubs and private owners all throughout the Unites States placed orders and Piper sold 286 Cherokees in its debut year. Gratified (but not, I dare say, entirely surprised) with this a great success, plans which had been made to expand the Cherokee family if all went well went into immediate action.

It is said that when one door shuts, another one opens, and vice versa. This was no less true at Piper Aviation. Simultaneously with the introduction of the Cherokee, the parts inventory, tooling, jigs and part manufacturing stations, all of which had been used to build the once revolutionary PA-22 Tri-Pacer and its twoseat version, the Colt, were disassembled and disposed of. With a sigh and perhaps a tear or two, these aeroplanes passed into aviation lore.

For one year the 150 and 160 hp Cherokees represented the entire line. However, Piper’s well-laid plans to expand it to include Cherokees of greater power were busily being implemented. On 3 August 1962 the PA-28- 180 powered by the versatile and by now ubiquitous workhorse of GA, the 180 hp Lycoming O-360 A2A (yes) was type certified and began to roll out of the new Piper factory at Vero Beach, Florida in early 1963. With a useful load of 1,170 lbs., this was the first Cherokee in which four substantially sized adults could fly in addition to full tanks (50 US gallons).

By the end of 1963, Piper could quite rightly claim victory and justifiably feel that its bourne had indeed gloriously arrived and had produced most excellent fruit. The Cherokee PA-28-160 equalled or bested the Cessna 172C in virtually every area of performance. Additionally, and surely much to Cessna’s discontent, when Piper installed the 180 hp 0-360 Lycoming in the Cherokee airframe creating the Cherokee PA-28-180 for which Cessna had no equivalent model, the additional 20 hp gave it even better performance over the 172. (Figures below supplied by Piper and Cessna*)

*Just a note about manufacturer’s published performance figures: Of course, there is always the temptation to, let’s say out of politeness, “exaggerate” these numbers. However, the FAA does not permit this practice to go too far as pilots must be able to rely on accurate published performance numbers so that they may, among other things, safely plan cross-country flights. All official aircraft POHs must be certified as containing information which is based upon real-world testing and which is as accurate as possible. To get around this, manufacturers have been known to publish performance numbers, particularly in advertisements, that were obtained when the aeroplane was loaded at less (sometimes much less) than MGW.

Versatility is one of the many charms of the Cherokee’s basic airframe and it has been effortlessly adapted

	Cherokee 160	Cherokee 180	Cessna 172C
Max. speed at sea level	120 kts (138 mph)	132 kts (151.8 mph)	120 kts (138 mph)
Cruise75% power at 7,000’	115 kts (132.25 mph)	124 kts (142.6 mph)	114 kts (131 mph)
Rate of Climb @ gross	700 fpm	750 fpm	700 fpm
weight - sea level	700 fpm	750 fpm	700 fpm
weight - sea level
Stall – flaps down power off	48 kts (55.2 mph)	50 kts (57.5 mph)	45 kts (51.75 mph)
Takeoff: ground roll	740’	720’	825’
over 50’	1,700’	1,620’	1,830’
Landing: ground roll	550’	600’	690’
over 50’	890’	1,150’	1,140’
Service ceiling (100 fpm climb)	15,000’	16,000’	14,550’
Useful load	990 lbs.	1,170 lbs.	990 lbs.

Note: The Cherokee 160 and 180’s performance reports were made while being tested at MGW. We cannot confirm that Cessna 172 was similarly tested at its MGW. Also, note that the Cherokee 180’s excellent performance was measured while it was carrying 180 lbs. more useful load than either the Cherokee 160 or the Cessna 172.

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Lycoming 0-320 B2B

1963 Piper PA-28-180

to engines of varying power, from 150 to 300 horsepower, with little airframe modification being required.

Piper Aviation and its brilliant engineering team had accomplished what it had set out to do, to provide a real choice in the GA market between the new Piper aeroplane and the Cessna 172. As William T. Piper, with his hand ever firmly on the aviation public’s pulse had predicted it would be, the introduction of the Cherokee was greeted most enthusiastically, which enthusiasm has not and shows no sign of waning.

THE CHOICE

Fitting neatly between the Cessna 172 and 182, when it was introduced in 1963 the Piper Cherokee 180 filled a niche that had long wanted filling. Accordingly, it became and remains on*e of GA’s most popular aeroplanes. In both its latest incarnation, the PA-28-181 Archer TX and LX, and in the many PA-28-161 Warriors which have had a 180 hp Lycoming engine replacement,* the combination of the Cherokee airframe and a 180 hp engine truly is the magic touch, the Goldilocks aeroplane indeed.

The first difference that one notices regarding the Cherokee vs. the 172, putting all of the performance

* Just a word about Warrior engine upgrades, it is this writer’s understanding that the popular Sykes STC (Arch-Warrior SA2946SO) and the few others that exist which permit and regulate the installation of a 180 hp Lycoming 0-360, and which also require the installation of a larger propeller on the Warrior airframe, curiously do not include a concurrent increase in he Warrior’s MGW (maximum gross weight), making the choice to do this expensive, PITA upgrade somewhat dubious. Better to just sell the Warrior and buy a good Archer.

numbers aside for a moment, is obvious — the wing. 172s have a high wing, Cherokee’s, a low one. As mentioned, the pilot and passengers of a high wing aeroplane have and almost entirely unobstructed downward view which is excellent for sightseeing and which facilitates navigational orientation. The problem with most high - wing aeroplanes (excepting those few highwing designs where the pilot sits well-forward of the wing) is that the wing obstructs visibility whilst in a turn. This may not be much of a problem enroute when few turns are made and the sky is mostly clear of traffic; however, when in the pattern at a busy airport, the problem becomes clear.

In a high-wing aeroplane, even though a pilot may be properly diligent in checking that the sky is clear prior to making a turn, once in the turn he or she is blind to all that may be to the inside of the turn. Additionally, for the duration of the turn, short of lifting the wing and stopping the turn to re-clear the sky, the pilot has no way to know if another aeroplane has entered that area.

A lowwing aeroplane has no such problem in the pattern. The insideturn wing politely gets right out of the way in the direction of the turn, granting the pilot an unobstructed view of where he or she is flying. As to downward visibility, the low wing does not obstruct the view nearly as much a one might think. In all of the many, many hours that this writer has spent flying low wing aeroplanes, there has never been an instance that comes to mind when a want of downward visibility was an issue.

Another difference between the high-wing 172 and the low-wing Cherokee is ground effect during takeoff and landing. Ground Effect is that property of aerodynamics which causes a “bubble” of lifting air to form under a wing when it is flying within approximately at ½ of its span from an incompressible, solid surface which, of course, includes water. Because of its proximity to the ground a low-wing aeroplane will usually create stronger ground effect than a high-wing aeroplane, and when descending to the runway, it will be felt sooner as well. During takeoff as well, all else being equal, the pilot of a low-wing aeroplane will most often feel the onset of lift more readily than the pilot of a high wing aeroplane. Of course, the pilot of the low wing (or any) aeroplane must be cautious and not try to climb out too soon on the ground effect bubble, but must wait until the aeroplane has accelerated to its proper airspeed before climbing further.

On takeoff, at neutral trim the Cherokee will not (unless somewhat aft loaded) lift off by itself as will the Cessna 172. Some affirmative, but gentle aft yoke at the appropriate airspeed, approximately 50-55 knots (57.5 63.25 mph) depending upon gross weight, will be necessary to rotate and lift off. This is because the Cherokee normally sits at a level or slightly negative Alpha during the initial takeoff run. Also, and for the same reason, in neutral wind conditions, minimum right rudder input to

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AN AEROPLANE FOR THE REST OF US

Fuelling a Piper

Cherokee

Checking fuel level in Cessna 172 left tank

Piper Cherokee with left cowling open for engine inspection during walkaround (both sides open similarly)

Some Piper Cherokees offer large doors on both sides of the cowling while others offer

the entire top cowling to be easily removed.

offset P-factor is required during the takeoff run.

The Cherokee’s roll rate, particularly with a rectangular wing, is faster than that of most other GA aeroplanes. At the commencement of a turn the rectangular wing produces little or no adverse yaw, less in any event than does the semi-tapered Cherokee wing and definitely less than does a Cessna 172. Overall, the Hershey Bar wing Cherokee feels more maneouverable and sprightly than the 172, and very like a sport aeroplane.

When landing a Cherokee the onset of ground effect can be clearly felt and may enable very gentle and satisfying touchdowns. While a gentle landing may certainly also be made in a Cessna 172, in this regard the Cherokee is more consistent and seems to require less finesse.

When the wind blows strong the Cherokee has an obvious advantage over the Cessna 172 whilst on the ground. As mentioned, the Cherokee’s vertical centre of gravity (C. G. v) is much closer to the ground than that of the Cessna 172. Also, the Cessna’s wing sitting up above is more likely to catch the wind than the Cherokee’s low wing. Accordingly, the Cherokee naturally sits on the ground more firmly and stably and is less prone to be tipped over by a mighty blast than is the 172. Additionally and most significantly, as mentioned, the 172’s wide undercarriage is only 83% as wide as the Cherokee’s undercarriage which also handicaps it when attempting tight turns whist taxiing.

Not only does the Cherokee’s wider undercarriage permit easier and tighter turns, it is far more stable than the 172 in a fast turn. Additionally, the high-wing Cessna 172 is more vulnerable to crosswinds on takeoff than is the Cherokee. This writer recalls being almost tipped up onto the downwind wheel in a Cessna 172, when a sudden powerful crosswind gust struck the aeroplane during takeoff. This writer recalls that the Cherokee in similar winds just tends to shrug off such a gust and takes off with little problem. Our good friend Darryl knows something about dangerous cross winds in a Cessna 172.

The Cherokee’s stall and departed flight characteristics are far gentler than that of the Cessna 172. As mentioned, the Cherokee does not break much if at all at the stall while the 172 has a most definite and vigorous break. While neither the Cherokee nor the Cessna 172 may be legally spun whilst at normal category, at any weight the Cessna 172 is far more likely to inadvertently spin out of even a mildly a crosscontrolled stall than is a Cherokee.

More practically, because of its low wing it is much easier to look into and fill the Cherokee’s fuel tanks than the Cessna 172’s tanks which require a somewhat awkward and tenuous step up and climb to check the fuel quantity. On the other hand, it is far more awkward to stoop down low under the Cherokee’s wing to check and to drain the wing tank’s sumps prior to takeoff than to do the same under the high wing of a Cessna 172. Also, where the Cherokee allows a complete visual inspection of the entire engine and its components during

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+ 74 hidden pages

A2A Piper Cherokee 180 User Manual

CONTENTS

PIPER CHEROKEE PA-28-180 AN AEROPLANE FOR THE REST OF US