Modified Elite Elevator
Posted: Sat Feb 18, 2012 2:18 pm
I tried out my modifications to the Elite elevator spades this morning. The following information pertains to an elevator with spades aleady cut down to 4 1/4" wide. Also, the airplane is on amphib. floats.
Before modification of the spade leading edge, the cross section was per Murphy's design - i.e. rectangular with rounded corners. In this configuration, when pulsed downwards in cruise flight, the aircraft continues to pitch downwards - i.e. the airplane demonstrates negative dynamic stability in pitch, stick free. This pilot ran out of courage before the airplane ran out of forward pitching tendancy. Everything happens quite slowly, so is readily controllable hands on. In fact, pilots don't tend to notice the behaviour until it's pointed out to them.
The modification consists of changing the spade leading edge cross section to a semi circle. The resulting handling is certainly an improvement. The pitch stability is now just positively stable. When you pulse the stick forward and release it, the nose stays where it is for a second or so - it may even pitch a degree or so further down - then very slowly returns to the trimmed attitude. This takes about 17 seconds. I'd rather see it take something like 3 - 5 seconds. However, I'd say the change is well worth making. If anybody has any other ideas to further improve the situation, I'd like to hear them.
Al
Elite #587
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Before modification of the spade leading edge, the cross section was per Murphy's design - i.e. rectangular with rounded corners. In this configuration, when pulsed downwards in cruise flight, the aircraft continues to pitch downwards - i.e. the airplane demonstrates negative dynamic stability in pitch, stick free. This pilot ran out of courage before the airplane ran out of forward pitching tendancy. Everything happens quite slowly, so is readily controllable hands on. In fact, pilots don't tend to notice the behaviour until it's pointed out to them.
The modification consists of changing the spade leading edge cross section to a semi circle. The resulting handling is certainly an improvement. The pitch stability is now just positively stable. When you pulse the stick forward and release it, the nose stays where it is for a second or so - it may even pitch a degree or so further down - then very slowly returns to the trimmed attitude. This takes about 17 seconds. I'd rather see it take something like 3 - 5 seconds. However, I'd say the change is well worth making. If anybody has any other ideas to further improve the situation, I'd like to hear them.
Al
Elite #587
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