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Why Buy A Coupe

Disclaimer: We have no professional or expert qualifications of any kind.
It's fully up to you to check any information you find here with
standard aviation industry sources such as aircraft maintenance
manuals, flying instruction books and, above all, FAA regulations!

By Ed Burkhead
(copyright reserved)

This article was originally prepared in response to letters from prospective Coupe buyers who wanted to know the safety history, problems to look for, model information and everything else in which a prospective buyer would be interested. It does not try to be a complete source, though.

See Stanley Thomas' excellent book The Ercoupe. (Due to copyright issues, this is out of print and hard to find.) You can also search for The Ercoupe on the used market from several sources.  In addition, the Univair book Specification, A.D. notes, S.T.C.s, (Univair product number ESS, $17.00) is a critical reference book that every Coupe owner or would-be owner should have.

Strong recommendation

Over the years, I've seen several new Coupers buy planes with major problems. A pre-purchase inspection would have prevented financial catastrophe for most of these people.  Several years ago, with good advisors, I made a pre-purchase inspection checklist to make a try at preventing these problems.  I'd personally urge buyers to take this list to your own mechanic and talk over what you want to do during your own pre-purchase inspection.  Personally, I wouldn't buy any plane without it.  I'm donating this to the public section to assist all potential Coupers.  It was written as a service to the club, however, and I urge you to join and stay a member of the EOC -- the EOC is our mutual assistance society and we need you.  Pre-purchase inspection

Quick history
This plane is a member of the family of planes known as Ercoupe or Aircoupe. The Ercoupe was designed between 1936 and 1940, with the first flight of the prototype in 1937. Before WW2, 112 were built and approximately 5,000 were made immediately after the war. About 400 more were built between 1958 and 1969. The original name was derived from the name of the company, ERCO, which stood for Engineering and Research Corporation. When later companies manufactured the plane, it was called the Aircoupe.

Designed by Fred Weick and a small team, the Ercoupe was the first plane to incorporate much of the original research that Weick performed as the assistant chief of the NACA aerodynamics division. These new features include the inability to be held in a spin, the tricycle landing gear to improve landing and take-off safety, the fully cowled engine, and a control system in which the rudders are linked to the ailerons to simplify controlling the airplane. All these features were invented by Fred Weick and his team.

Basic flying characteristics are the same as modern aircraft with one exception. In the Ercoupes with linked rudders/ailerons, in a cross-wind, the airplane is landed in a wing-level crab. Though the main landing gear is sturdy, it is not abnormally strong and certainly doesn't "swivel." Yet, due to the natural geometry of a tricycle with a swiveling nose wheel, the airplane immediately lines up with the direction of travel after touchdown. Two-control Ercoupes fly with a demonstrated cross-wind component of 25 mph. Some Coupers regularly fly with even stronger cross-winds.

Engine comparison
The planes with 75 hp engines have pretty good performance. They will generally fly between 98 and 106 miles an hour, depending on the pitch of the propeller. This is a good benefit of the airplane's designer being the time-period's leading authority on propellers.

When comparing the following figures with your own plane (or the one you are about to buy) consider these factors: The propeller pitch will greatly affect the cruise speed and climb performance. For every inch of steeper pitch, there will be about two miles per hour gain in speed until you reach the point (very quickly) when the engine doesn't have the horsepower to spin the prop up to speed. As speed increases, horsepower required increases almost linearly until a certain speed is reached where much more power is required to effect each new increment in speed. The speed at which this occurs depends on the shape of the object being pushed through the fluid, in this case, the air-frame through air.

At some point, a steeper pitched prop will result in less thrust than would be obtained with a flatter pitched propeller. Probably before this point is reached, the climb performance will be nonexistent -- climbing is done at slower speeds where the steeper pitched prop is even more inefficient!

Ercoupes with the 85 hp engine get better take-off and climb performance, and will cruise a bit faster, and will use a little bit more fuel than 75 hp planes. But there's not a lot of difference. Cruising speeds with the 85 hp engine range from 104-112 mph.

Most of the 85 hp engines in service in C and D models have been converted from 75 hp engines. This was done (as allowed in type certificate A-787 note 4) per Continental Service Bulletin M47-16 dated June 7, 1948. Mostly, this requires changing the carburetor fuel jet to allow more fuel flow, remarking the oil dip-stick to show 4.5 quarts as full, adding a couple of engine baffles to take care of increased heat production, and changing the propeller so it conforms to the requirements of the new engine. The details are in the Ercoupe's Aircraft Specification A-787 and the other documents mentioned.

There is some performance gain -- about 2-3 mph according to Paul Prentice's book Fly-About Adventures and the Ercoupe.

 The Forney Aircoupes have the C-90 engine with a well matched propeller. They always out climb my C-85 which has a climb propeller and they have to throttle back quite a bit for me to stay with them in cruise. Cruising speeds probably run from about 106-114 mph (again according to Paul). The Alon Aircoupes, with their sleek bubble windshield and 90 hp engine often claim cruising speeds up to 124 mph.

With the O-200 engine, climb improves again, but cruising speeds drop down because of the propeller that was STCed with the engine conversion. In the absence of definitive data, estimate cruising speeds to be about 108 mph. Someone who'd like to research alternate propeller lengths and pitches (and fight with the FAA for approval) may be able to trade some of that climb for somewhat better cruising performance.

Remember that, for each airframe, there is a natural "maximum" speed determined by the shape and drag. To get to that speed, it doesn't take much increase in power. To go faster than that speed, it takes a lot more power. So, putting a much bigger engine on a plane will make it climb much better and yet it may not fly much faster.

Different models
Which models are dogs, which are the best? I'd say that none of the models are dogs. The later models were most popular among aficionados until the Sport Pilot regulations came along. The pretty bubble canopy on the Alons may increase the top speed, but they have a window-open max speed of 100 mph. The slide-down side window canopy on the older model allows windows-down open-cockpit flying at any speed. (I personally prefer this feature.)

A difference that may be important to you is gross weight and airplane weight. The "C" and "CD" models only allow a gross weight of 1,260 lbs. (1320 with the increased gross weight STC)  In the early planes of the model, the weight of the airplane was low, the useful load was around 450 lbs, the fuel tanks about three gallons (total) smaller than in later models and the weight left over for pilot, passenger and luggage was reasonable. The planes had minimal instrumentation and equipment.

As the months and years went by, the planes got heavier -- starters, batteries, gyro instruments, radios and more were installed. Useful load shrank with full fuel to where many planes could only carry one person, legally.

Beginning with the D model in early 1947, serial number 4424 through 4499, 1,400 lbs gross weight was allowed -- a big improvement. This entailed limiting the elevator to 9 instead of the previous 13 due to inadequate stability in the condition of full power, full gross weight, and full up elevator at 13.

The 9 limitation on the D model's elevator did not allow as slow a landing speed and this was thought to be less desirable. Therefore, beginning with serial number 4500, in about April of 1947, the plane came off the line as the CD model with all the D's improvements but with the elevator restrictor bolt in the 13 hole and allowing only 1,260 lbs gross weight. According to the type certificate A-787, the plane could be converted to be a D model, allowing it the 1,400 lb gross weight, if the owner desired.

The E and G models had the split elevator, 85 hp engines and were allowed 1,400 lbs gross weight. The split elevator allowed the slipstream to flow through the split without much affecting the elevator. This allowed slow flight similar to the C model but with little change in trim between zero and maximum engine power. The F model, a fuel injected variant, was not marketed. The E model was introduced in 1948 and the G "Club-Air" and H models were introduced in 1949.

The H model was stripped down with only a 75 hp engine, no starter, radio, lights, battery or generator. Only seven were produced and these may have been converted to add those features back in.

The early Forney F-1 Aircoupes were certified to carry 1,400 lb. gross weight.  Beginning with Forney F-1A, serial number 5715, the gross weight was increased to 1,450 lbs. (Note: Forney F-1, serial number 5611-5714 can be upgraded to be F-1A according to Aircraft Specification A-787, note 5.)

A popular "folk wisdom" is that the Coupe will fly with anything that you can fit into it. This is belied by the occasional event such as when our club president, Jack Harkness, and Jimmy Funk died when they tried a high, hot take-off at high gross weight. I have personal maximums for the gross weight with which I'll fly. Remember, if you fly above legal gross weight, you probably have no insurance and you are a test pilot in an unproved airplane.

For perspective, most Coupes weigh around 850-950 lbs. Mine hasn't been weighed recently but is supposed to weigh 890 lbs.  Some owners of C and CD models are removing unneeded items to reduce the aircraft weight so they can carry greater loads under the Sport Pilot rules.

Serial numbers 113-812 were mostly constructed the same as the pre-war planes except that a 75 hp engine was used and a starter, generator and battery were added.

Pre-WW2 Ercoupes used a cast aluminum alloy main landing gear and Hayes wheels. Post war planes, serial numbers 113-812, used a welded steel landing gear. Numbers 813 and up used forged aluminum parts and Goodyear wheels and brakes with 6.00 x 6 tires. Alon introduced a spring-steel main gear that was simpler and almost maintenance-free. However, it was stiffer when taxiing on rough ground (the old-style main gear was still offered as an option).

Early Coupes used an elevator trim system that included a crank on the instrument panel to change bungee tension on the control column. Later models used an aerodynamic trim tab on the elevator which worked better and provided a backup aerodynamic control of the elevator in case of control cable breakage. Still later models increased the area of the trim tab. The aerodynamic tab is desirable and is available as a kit from Skyport http://ercoupeparts.com 

On later models of Ercoupe, the throttle and trim were on a quadrant at the bottom center of the instrument panel. Later manufacturers dropped this feature.

Forney built the plane from 1956-1960. The biggest change in the Forney Aircoupe was the introduction of the Continental C-90 engine and a well matched propeller, giving improved performance. They also, according to Stanley G. Thomas, in his book The Ercoupe, replaced the fabric covering of the outer wing panels with metal, installed the bubble windshield and larger rear windows of a more rectangular shape, installed bucket seats, modernized the instrument panel and replaced the rubber doughnut cushions in the main landing gear with Belleville springs.

Keeping the split-elevator, Forney improved it by adding a pre-loaded spring to the elevator control system that would give the feeling of a stop at 60 mph (about 13) yet allow the pilot to pull through the spring to get the low speed landing with 20 of up-travel.

Forney also initiated the double-fork nose gear which has been retrofitted to many earlier Coupes. The earlier, single-fork nose gear was more susceptible to shimmy than the double-fork. However, if your plane has no shimmy problem, just keep it in good repair, there's no need to change. Forney also added large rear windows.

The F-1A Forney Trainer allowed an increase in gross weight to 1,450 lbs (up from 1,400 lbs).

Air Products Co., then manufactured F-1A Forney Trainers at Carlsbad, New Mexico between 1960 and 1962.

The Alon Aircoupe, built from about 1964-1968, incorporated a sliding-back bubble canopy and a greatly improved instrument panel with the ability to easily add radios. The Alon Aircoupe had three-controls standard (configured like standard aircraft with rudder pedals controlling the nose wheel). The two-control arrangement was offered as an option. Alon also lowered the window sills to allow easier entry. The early Alons had a glass bubble canopy with no sun-shade over the top allowing unrestricted visibility during turns. The later Alons (perhaps starting at the beginning of the A-2A had a sun-shade built into the canopy greatly restricting upward visibility yet keeping the occupants cooler.

Mooney bought the rights to the design and redesigned the tail to be the single Mooney-style. The new Mooney M-10 Cadet was designed to be spinable. It kept the Ercoupe fuselage and wing, the C-90 engine and the later variant of the Alon canopy.

 The type certificate and parts manufacturing authority for the Coupes are now owned by Univair of Boulder, Colorado.

Popular upgrades
Modifications that are popular are the 1320 pound gross weight increase for the 415-C and 415-CD models, available through an STC (contact Skyport),
the large baggage compartment, Cleveland brakes (I personally consider this a high priority), instruments, radios, lorans, paint, wheel pants, and the "split" elevator (for improved handling) for any model (if you can get it approved through the FAA (check with Skyport to see if an upgrade kit and/or STC is available).

According to an FAA specialist I talked to at Oshkosh, an airframe may be converted to be a different model only if it is explicitly allowed in the type certificate.

The conversion of Ercoupes serial number 113-4423 and 4500-4868 to be model D is explicitly allowed by Aircraft Specification A-787. (Numbers 4424-4499 are already D models.)  Due to the increased value of the Sport Pilot eligible models, conversion from C to D is now rare.

Caution:  A 415-C or 415-CD which was converted to be a 415-D (or any later model) at any time in its history can never be flown by a Sport Pilot acting as pilot in command, even if that plane is re-converted back to its original model (which is legal but futile).

The FAA specialist also said that an aircraft may be converted to be "like model x," meaning that all things necessary have been done to make that plane a model x even though it can't really be a model x. In other words, while you can convert your C, CD or D to be "like model E," it isn't really a model E. But for all practical purposes, you still get the increased safety of the split-elevator. Talk to your Flight Services District Office representatives (after first talking to local mechanics to find out which specialists normally approve changes and which ones normally reject changes).

Both C and D models are eligible for conversion to 85 hp engines. For model C, see A-718, section Engines and Engine Accessories, paragraph 110. For model D, see A-787, note 4. Conversion of model D Ercoupes can be done to a Continental O-200, 100 hp engine by paying for use of Skyport's STC (supplemental type certificate) and, of course, doing the FAA paperwork. Conversion to the O-200 for other models and other engine conversions would require that you persuade the local FAA representative to sign off on a onetime STC.

Response to question about airworthiness of Coupes
There was at least one airframe failure due to hidden damage to the wing (near the joint between the main spar and the tapering tip spar). This was addressed in Univair Service Bulletin #27 requiring installation of four inspection ports in the wing so this could be checked.

The few in flight airframe failures have mostly (?all?) been in aircraft which have been doing aerobatics or been engaged in high speed flight.  In spite of the legality of aerobatics in a 415-C, these aircraft were not designed for aerobatics and you have a very good chance of killing yourself and your passenger if you do aerobatics in them.  Personally, I'd include dives and high speed passes (above - wild guess - 125 mph) in that unless you know, absolutely, that your control system is rigged properly with no excess play.

There have been a number of airframes grounded because of corrosion near the wing attachment points and on the main spar center section. These problems are repairable though, in the case of the spar center section, repair can be expensive (i.e. complete replacement of the spar center section if the corrosion is bad enough).

One fatal accident may have involved aileron flutter and it's possible that internal aileron corrosion may have been involved.  It's also possible that there was excessive play in the control system, beyond that which is permitted, and the aircraft may have been performing a high speed buzz job and pull up.  The final accident report isn't in, yet, as of July 2009.  Inspecting the ailerons and the control system play is not difficult and should be a part of every inspection.

The wing spar attachment points (both on the wing side and the center section side) have the problem of dissimilar metals being joined -- this acts as a battery causing electrical current flow which encourages corrosion. There may be an interaction with sitting outside and having either rain moisture or mouse urine present. Most of our planes are NOT showing the problem -- and it can be readily inspected.

Acidic mouse urine may eventually ground a bunch of planes for major repairs. Paying hangar fees can be the economical route to avoid costly repairs. Corrosion found during normal repairs led to the "Swiss Cheese" AD requiring 16 inspection holes on the underside of each wing and the center section AD requiring more inspection holes and careful inspection of the center section. Do not buy and do not fly a Coupe that does not have these holes and the accompanying inspections!  This is especially true of Ercoupes with metalized wings! The worst corrosion problems have been found on metalized wings. Because of this care, we haven't had any planes lost to wing or center section corrosion to my knowledge. There's nothing special about Coupes in this, expect to see something similar in the other old planes as their fleets approach the same age.

Any plane you buy should be carefully inspected for main and rear spar corrosion as specified in the ADs.  If there's no corrosion now and you take proper care of the aircraft with the specified regular inspections, you shouldn't have any corrosion crisis.

Most other problems are common to all planes of the era. There are some things that have been discovered over the last 63+ years and have been addressed by service bulletin or airworthiness directive. If your plane has these items correctly complied with, it should be a quite safe airplane. Overall, we have a very safe airplane.

Few Coupes seem to have accumulated a very high number of flight hours -- not many were owned for extended periods by training or rental operations. I've yet to knowingly see a Coupe with more than 3,600 hours. If your prospective Coupe has over this number of hours, please watch for (and keep the club posted on) any fatigue related problems.

Cross country travel
Are Coupes suitable for travel? I've been to the Atlantic Ocean, the Pacific, the Canadian border, Florida, and a lot of places in between. It's as good for cross country as any 100-108 mph plane.

It is better than most if you have a Coupe with no rudder pedals because you have much more leg room. It is also better than most because, with any Coupe, you may be able to handle more crosswind component than with many other planes -- that's really useful on cross country trips. It is far better than most planes for cross countries because, wherever you land, people are interested in the Coupes!

Prices
When you buy your Coupe, expect to pay $20,000-$25,000 for a plane in excellent condition. $15,000-$20,000 may get you a perfect plane, if you get lucky, but most will have a value reducer like a mid-time engine or bad paint. Eight to ten thousand dollars may get you a fix-it-up before flying airplane.

For any condition, add $8,000-$10,000 for a Sport Pilot eligible 415-C or 415-CD.

It would be ideal to buy a plane that has been restored by one of the owners, A&P or AIs who restores Coupes as a hobby or professionally. If you buy one that hasn't been recently restored, (or even if it has) have it inspected carefully.

Learning to fly in a Coupe?
You certainly can. And you can do all of your flying in it right up to the test. However, recently there've been some pilots getting licenses restricted to the abilities of the plane they used in their check ride. I'd say you could do 85% of your training in a two-control Coupe then finish up the last 10-15 hours in a Cessna or Piper and ace your check ride to get an unlimited license. In practice, changing from being a good two-control pilot to being a good three-control pilot isn't a big deal.

How far will your Coupe take you in an aviation career?
Pretty far, with one caveat. A Coupe is an airplane. It has a couple advantages -- it can't spin or ground-loop, it's well behaved and it handles cross winds better than most planes.

If you are going to go professional, I'd suggest getting a Coupe with rudder pedals. The one problem you might encounter (this is the caveat), is that you might apply for a job with someone who doesn't really know anything about Coupes but who heard misinformation in the hangar, decades ago. That person might not respect your 1,000 hours of Coupe time as much as he would Cessna 150 time. (Brain damaged, I know, but it is possible.) On the other hand, you might run into one of many former (or current) Coupe owners or fliers and get the job automatically because of your demonstrated superior judgment in being a Coupe owner.

An aside: Fred Weick told me that he expected to sell a lot of the Coupes with rudder pedals. They are an OK part of the design. If you find the ideal plane, and it has no pedals, you should be able to buy a kit for less than $1,000. They are available, I think, from Univair and Skyport and from people who might want to remove them from their planes so they can have simpler controls and more leg-room. Put out an advertisement offering to pay the expense of removing them from the seller's plane and you may get several responses.

The Coupe can make a good instrument platform, I'm told by very experienced instrument pilots. It would be a good plane for building time in your logbook.

How long will you want to keep your Coupe?
That one is easy -- forever. Sure, as you get rich you'll want to get a Cherokee-6 or a Cessna P-210 or an Aero Commander or Citation -- but you'll still want to keep your Coupe for the sheer fun-of-flying. That's just the way it is.

Good luck in finding a Coupe -- we'll look forward to seeing you often.

 
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