Bob, Your information about the Coupe's airfoil is interesting and I have no information concerning it. I would address this paragraph, though.
Bob Condon wrote: > > The problem with the Ercoupe is then that the D model is fully controllable > at 1260lb but at some higher weight it can demonstrate a stall behavior which > could lead to an unpleasant low altitude stall. With rudder pedals that > stall would be more manageable, without the stall should roll off to the left > and be uncorrectable until back pressure is released and the wing resumes > flying. > First, the D model has the up travel limited to 9 degrees specifically so it'll be safe at 1400 lb.. This is to match the 415-C's characteristics at 1260 lb. and 13 degrees of up travel. I have tested the 415-D at max power (C-85) and full up elevator and found that, with coordinated rudders, I always had control. The Coupes are also certified as spin-proof with rudder pedals. Since I have rudder pedals, I also tried it with FULL left rudder (the worst condition) and right aileron. I still maintained control at 1400 lb., fully crossed controls and very high power settings. I chickened out about 200 rpm less than full power because I was getting into very squirrelly behavior. At all times, _slight_ relaxation of the up elevator restored smoothly controlled flight immediately. Rudder pedals do not make the stall more manageable -- having them gives you the opportunity to make things worse. With the rudders coordinated, you maintain BETTER control with full up elevator. It seems that Fred designed the coupe wing to mostly not stall given the up elevator travel designed into each model. As full up elevator is approached and angle of attack is increased, the fuselage/wing filet and the little bump line at the leading edge conspire to start a stall at the wing root. This stalled area progresses out from the wing root in a half-V shaped pattern. The turbulent flow over this wing-root area disturbs the flow over the tail preventing the elevator from pushing the tail down any further. So, between the limited up travel of the elevator and the deliberate stall at the wing root, the plane is prevented from making a full stall of the outboard parts of the wing. Thus, you can't lose aileron control and crop out of control. All this assumes you are flying within the weight and balance center of gravity limits. Go outside that and you are a test pilot with your and your family's lives as the wager. -- Ed Burkhead Peoria, Ill. N3802H [EMAIL PROTECTED] wrote: > > I think the group is missing the point on the elevator throw issue. The > coupe will recover from a spin as well as most other planes will given enough > time. The problem is that with the extended up elevator limits and 1400 lb > weights the coupe can demonstrate a departure stall which usually leaves too > little altitude to recover. > > A PA-28-235 with four people aboard demonstrated this maneuver at my 2000' > airport a few years ago with the classic results. The aircraft stalled at > about 50 to 75' above the end of the runway and impacted inverted on a > heading 90 degrees left of the runway heading. The PA-28 cherokee family of > planes have about as nice a stall behavior as any and should have been easily > controllable on this departure but the pilot failed to manage the situation > for several of the usual reasons. > > The problem with the Ercoupe is then that the D model is fully controllable > at 1260lb but at some higher weight it can demonstrate a stall behavior which > could lead to an unpleasant low altitude stall. With rudder pedals that > stall would be more manageable, without the stall should roll off to the left > and be uncorrectable until back pressure is released and the wing resumes > flying. > > A further problem in this direction concerns the choice of wing for the > Ercoupe. Fred chose the 43000 family wing because it and the 23000 family > were the darling of NACA at the time. These wings exhibit good low drag high > speed characteristics and good lift characteristics at high angles of attack. > The bad news is that they have poor stall characteristics because once > stalled they do not recover easily. A wing that stalls at say 50 would not > recover until the speed increased to 55 which makes stall recovery somewhat > more of an adventure. The only aircraft which use these wings are aircraft > which are never allowed to stall. The only other aircraft to use the 43000 > family was the ATR-42/72 which has had some complaints from its pilots > because of its flight behavior. > > The Ercoupe matches the performance of a C-150 on 15% less power because of > its low drag wing but it was not meant to stall and experimenting with up > elevator limits places the pilot deep into test pilot territory which is no > place to take family and friends. > > Bob Condon
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