On 2010-08-30 4:02 PM, William R. Bayne wrote:
Don's trim system is discussed at length in Ercoupe Service Memorandum
No. 19 of 4/26/46 (date from ESM No. 38). It says: "...the natural
trim speed in a glide with the controls and trim device disconnected
is now approximately 70 mph, a speed at which the airplane can be
maneuvered to a satisfactory landing by throttle alone".
That statement concerns me.
When the aerodynamic trim tab is in line with the upper surface of the
elevator, the trim speed on my Coupe was well in excess of 110 mph -
*/not/* 70 mph. So, how could the natural trim be 70 mph with no
aerodynamic trim tab and no control cables?
To trim any Coupe I've seen to 60 or less mph, the aerodynamic trim tab
must be quite a bit down, on the order of 40-60 degrees down. The
downward trim tab raises the elevator. The raised elevator pushes down
the tail and increases the angle of attack of the wings which gives you
the correct trim for low airspeeds.
Something is not tracking in the discussion of what happens with no
control cables and no aerodynamic trim tab, it seems to me.
Ed
