High angle of attack departure testing

April 1988

Our own flight test experience plus NASA spin tunnel evaluations plus a NASA test pilot's actual attempts to spin a Long-EZ have led us at RAF to believe that it was virtually impossible to get our airplanes (VariEze and Long-Ez) to depart from controlled flight and enter a classic spin. Recent flight testing conducted here at Mojave by three different test pilots on a research airframe similar in configuration to a Long-EZ, have resulted in the classic spin modes.

While opening the high angle of attack envelope, we discovered that this particular airplane would, indeed, depart and would enter steep upright spins from which it would readily recover, at least in spins of less than 2-1/2 turns. As we cautiously pushed into the unknown, we suddenly found that this plane could also go flat! That is to say, it would transition from a steep spin into a very high angle of attack, flat spin, uncommanded.

Recovery was very difficult but a combination of full recovery controls plus power was successful, at least twice. However, in one case, the engine quit due to high centrifugal forces and, although full recovery controls were put in after two turns and held in for eight more turns, this had no perceptible effect. The pilot then initiated full throw pitch control inputs, attempting to get the nose down. Control input was in phase with a slight pitch oscillation he noticed during the previous 10 turns. The oscillating inputs were successful and after 7 more turns, the airplane was recovered and landed dead stick on the Mojave runway.

This experience was quite a shock to the pilot who did not think a canard configured airplane could enter a flat spin. The chances of recovering from such a spin are usually remote. The pilot experienced some disorientation, the spin rate was as high as one turn each two seconds, or 180' of rotation per second. The rate of descent was close to 5000 feet per minute, a total of 4000 feet was lost during the 17 turn flat spin, and subsequent recovery.

What was learned from these experiences? First of all, it may be possible to depart and spin any canard configured airplane, even a plane such as a VariEze or a Long-EZ, particularly if these airplanes were not carefully and accurately built. Do not deviate from the plans. Use care to not accept any modification or variation from that configuration that has been thoroughly tested here at RAF, subtle modifications of the wing or winglets may make your aircraft dangerous. Use your absolute best effort to set canard, wing and winglet incidence correctly. Level all waterlines as closely as you can read a level. In other words, build your EZ as accurately as you are capable. Conduct a careful, accurate weight and balance, including measuring the airplane. Do not assume your airplane will be the same as the prototype. Also, your test program must include stall/departure tests of your airplane, flown with a parachute and with plenty of altitude.

Fly your airplane sanely and well within your own piloting skills and ability, and remember that flying is not necessarily a dangerous activity, but it can be terribly unforgiving of any carelessness or foolish judgment.

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