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Careful, it might FLY!

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T

Tinbuzzard

The guilty will be protected by ****s

Recently, I witnessed a taxi test that became an unintentional first flight.
My friend ****, was testing a small tricycle gear homebuilt at ******* airport. The plane was basically finished, and initial high speed taxi runs showed a reluctance to rotate at a reasonable speed. We redid the W/B both empty, and with him in it as a sanity check, and found that it was nearly an inch outside the forward limit. A slightly heavier engine than standard, and a prop extension seemed to be the culprits. Incidence angles of the wing and horizontal stab were OK. We also checked the elevator travel, and adjusted it to give another 2 deg. of up.

As a temporary measure, we bolted two 5# lead blocks on either side of the aft fuselage using a hole intended for a ground handling rod. This was a good location structurally, and some tickle at the back of my mind made me use a 3/8" aircraft bolt and locknut to secure them. This put the new balance just forward of the midpoint of the allowable range.

The owner went back to the runway intending to accelerate to the point where the plane would start to get light on the nosewheel with full aft stick, and then throttle back and neutralize the controls. He didn't plan on lifting the nosewheel off the pavement at all.

He accelerated down the runway with the mighty ****** snarling out its ** horsepower. As he reached what looked like nearly flying speed, the plane had yet to show any pitch change. At the exact instant that he throttled back, the plane very abruptly rotated quite nose high and immediatly lifted off. He was moving the stick forward at the same time that he was reducing power, and as a result the plane nosed over, pogoed hard on the nosewheel, and bounced about fifteen feet in the air. He recovered with full power and held the plane level until he could do a normal climb out. The trip around the pattern and the landing were uneventful. (except for me trying to reswallow my heart as I saw him cilmbing away with the weights clearly visible on the tail)

After we both had let our pulse rates get out of the red zone, he reported that the plane handled fine in the air with no abnormal control forces. (he had previously flown another example of this design) We are now looking at the downthrust angle of the engine, (not spec'd well in the plans) and possible airflow attachment issues with the horizontal stab.

The lesson of all of this? If you are in a plane, on a runway, and push the throttle forward, you MUST assume that it will fly! Both you and the aircraft must be fully prepared for flight. A few days after the adventure, the owner found several unsafetied bolts in both aileron hinges. One had rattled loose. This has been corrected, and further testing will proceed carefully with a fully ready aircraft.
 
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