That was an excellent explanation - I have only had the plane for about a year
and a half. The person I bought it from said he always flew his pattern about
90 and approached touch down at about 85. I found this to work out pretty well
and have since tried to land slower and slower. I have found that it will stay
controllable at about 75 but much less and it is really going down on it's own.
I have a GPS and the speed seems to be consistent with the GPS so I don't
think that there is anything wrong with the Indicator or the Pitot system.
Maybe some of my problem is I seem to almost always have someone beside me that
weighs about 240 and so we are at near max landing weight and that must also
make landing speed greater. So far I have done a good job of keeping both the
plane and my passengers safe and happy. And I guess that is all that counts.
Along with loving every single second of being in the sky with the Coupe.
Thanks everyone for the info and the concern. Keep'em flying.. Jerry
----- Original Message -----
From: William R. Bayne
To: ety
Sent: Sunday, March 14, 2010 11:43 PM
Subject: Re: [ercoupe-tech] "Falling Out Of The Sky" at 72 mph
Jerry,
Your G model has (or should have) the "split elevator".
If the air speed indicator is accurate and if the plane is rigged correctly
it WILL NOT "fall out of the sky about 72 mph". That's well above the "high
sink rate" range. As a first step, I suggest you take a GPS aloft, slow the
bird to 73 mph indicated, and compare the two readings. The Approved Flight
Manual for Models 'E' & 'G' on p. 11 showed a "true airspeed" of 60 mph when 56
mph was indicated, 70 mph when 67 was indicated and 80 when 78 was indicated.
Landing the various coupe models at the speeds Ed stated is not rocket
science, but it does presume an accurate air speed indicator and proficiency in
accomplishing an appropriate sequence of events. In my own case, I had absolute
confidence in the Ercoupe Instruction Manual and "just did it"; but some are
more comfortable having these things demonstrated before they can proceed.
As a rule of thumb, the indicated airspeed is higher that the truth below 100
mph and lower than the truth above. For all values above "minimum speed" the
error is 3 mph or less. That's not enough to get anyone in trouble that has any
"feel" whatsoever for the aircraft in flight.
The "stall" in an Ercoupe should be a gentle drop of the nose to pick up a
few miles an hour and altitude loss should be minimal. If the yoke is moved
back too rapidly near the minimum speed, the resulting "whip stall" is much
more abrupt and more altitude is lost. This is something best worked out at
altitude and not just above the runway.
Should a low time pilot "balloon" (suddenly climb and find themselves 5-10
feet off the runway with little forward speed), immediate application of full
power restores lift to the wings with minimum loss of altitude. Hesitation,
however, will likely result in a hard landing with possible damage.
Most of us have a WW II training base with long runways within flying
distance that is now municipally owned and operated. Go there and make any
necessary arrangements to practice slow flight and touch and goes with plenty
of hard surface available.
With a 5,000' runway, practice slow flight...holding the bird one foot off
the pavement at the slowest speed possible. Before the coupe can "stall", it
will sink. So long as you can keep the bird from touching the runway surface
with the yoke at a constant speed you absolutely cannot stall while in "ground
effect" at that speed. Keep reducing that speed in two mph increments and
eventually you will be able to fly an approach arresting descent one foot off
the runway and fly the length of it without touching down.
Next time around, at that same constant speed move the yoke back a bit. If
the plane goes up, you weren't flying slow enough. If it sinks to the runway
surface, it will be your slowest, smoothest landing ever. At the moment of
touchdown, THAT is YOUR plane's "minimum speed" occurring just when you want it
to...at touchdown. Jot it down for future reference.
If you go back up to pattern altitude and establish that "minimum speed" you
will probably find that you are sinking like a stone. That's why the landing
approach is not flown at that speed in an Ercoupe. The G model has a power off
stall speed of 56 mph. The low speed warning cushion (spring) is supposed to be
felt at 60 mph.
The 415-D Approved Flight Manual on p. 10 suggests an approach speed of 75
mph and its power off stall speed is 58 mph. The manual for the E & G models
refers you to the Ercoupe instruction Manual, and it suggests approaches be
flown between 60 and 70 mph. At or near 1400# the higher value is more
appropriate.
Remember that 70 mph (true) is your "Best Rate of Climb" (see Climb Data, p.
10 of the Approved Flight Manual for Models 'E' & 'G'). At that speed, anytime
you move the yoke back gently the energy of the "excess speed" is converted
into altitude and the plane's altitude increases even as the forward speed
decreases. Your speed for "Best Angle of Climb" is even slower at full
throttle. This is simply NOT a speed range where you are tempting fate so long
as you understand how to trade speed for altitude and altitude for speed. This
is a fundamental skill all should practice, but If you are more comfortable
flying the approach at 80 mph, do so. The speed of the approach is relatively
unrelated to the speed at which touchdown takes place.
Most find it easier to establish a "stabilized approach" (constant airspeed
and engine rpm while maintaining a relatively constant rate of descent with the
yoke) until just before touchdown. When you cross the runway threshold at 5-10'
up reduce power and SLOWLY move the yoke back only as fast as does NOT make the
bird climb. The idea is to slowly increase drag with higher and higher angle of
attack holding the plane one foot off the pavement and when ALL the "excess
speed" is thus scrubbed off the plane will gently sink to a very smooth
landing. Unfortunately you may be using 4000'+ of runway to do it.
Now do this again, establishing the one-foot-off slow flight. Simultaneously
close the throttle and move the yoke back to keep the plane "balanced" at that
one foot off. Once THAT coordination is worked out, reduce engine rpm on final
(if necessary) to cross the "fence" at 70 mph. This should make it possible,
with practice, to land and make most second turnoffs WITHOUT BRAKES!
Minimum speed at the moment of touchdown is desirable because (1) the plane
can't lift off the runway again without power, (2) the wear on the tires (the
"chirp" at touchdown) is less because they have to "spin up" only to the lower
speed, and (3) brake puck and disk wear is reduced so much that once the
technique becomes "standard operating procedure" for you there will likely be
the need to land fast and hot about once a month in order that the puck remove
the accumulated rust from disuse.
Operating a properly rigged Ercoupe in this manner is "stall proof" except in
high, gusty crosswinds. For high, gusty crosswinds, add 5-10 mph to your
approach speed, but chop the power over the runway threshhold at 5-10' up and
do everything in the preceding paragraph exactly the same from that point on.
Having extra speed at or after touchdown is a PROBLEM, not "insurance". Should
a gust suddenly lift the plane off the runway, immediate throttle restores lift
to the wings and returns to the pilot the option of go-around or a smooth
landing (remaining runway permitting).
Until this level of proficiency is developed (and more than a few that will
"instruct" in a coupe don't have it to pass on), your are not master of the
Ercoupe. Until you are master there is risk. Maximum safety depends on owners
or operators reducing that risk to zero with appropriate priority.
Your metal wings reduce your useful load, but they have no meaningful effect
whatsoever on your approach speed or minimum (touchdown) speed.
Hope this helps.
William R. Bayne
.____|-(o)-|____.
(Copyright 2010)
On Mar 14, 2010, at 22:43, Jerry Ward wrote:
You guys all keep talking about landing your coupe at such slow speeds - I
have a metal wing G-model and I have trouble getting it to land under 75mph. I
sure am jealous of all of you that can land slow. If I were to try that I
would break my landing gear off. It starts to fall out of the sky about
72mph.. And I do mean fall fast. Jerry in the Great Northwest.
----- Original Message -----
From: Ed Burkhead
To: ety
Sent: Sunday, March 14, 2010 7:45 PM
Subject: FW: [ercoupe-tech] Kim's Ercoupe
Maybe this is more readable:
As I said a couple of days ago, this gave these results:
13˚ up travel 48-52 mph landing speed
415-C and 415-CD
9˚ up travel 55-60 mph landing speed
415-D and on earlier models
with 9˚ elevator limitation due
to using the 1320 pound STC
20˚ up travel 48-52 mph landing speed
415-E and all later models AND
earlier models with split elevator
installed via STC or field approval
on a form 337
