||Why Buy A Coupe|
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
manuals, flying instruction books and, above all,
By Ed Burkhead
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
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.
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
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.
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
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
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.
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,
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
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
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
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
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
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.
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
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
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!
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
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
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
How far will your Coupe take you in an
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.