David Megginson wrote:
This problem has little effect on normal flight, but it matters a lot for the landing and takeoff rolls of taildraggers -- without it, they have an unrealistic tendency to nose over.I have been tied up with an upgrade to SuSe 9.1 and wanted to comment on the tail dragger set up discussion.
1. I updated CVS last night and the changes to the J3 Cub make it impossible to do a full-stall 3 point landing. 2. It is not true that a wheel landing should end with applying full down elevator. In fact, you want to be almost at zero decent rate when the mains touch and then a little forward pressure is usually required to keep the immediate slight increase in angle of attach from putting you back in the air, since you have not yet stalled.
3. In a real cub, it takes very little relative wind to keep the tail up. So in a head wind of say 10 knots, you can lift the tail with forward pressure as soon as you apply power. I have seen pilots hold the brakes, apply power and lift the tail at zero ground speed.
I really thought the way the cub was in fgfs before these changes was very realistic. I would do 4 touch and goes in the length of 29R at KSFO with all of them wheel landings. Were you really having trouble with nose overs with the cub? I have real hours hours in Stinson 108 Voyager, Taylorcraft (almost identical to the cub), Cessna 140 and 170, Luscome Silverair, Citabra, Champ, and probably other tail draggers that I have forgotten.
Also, even though it is usual to have the CG slightly ahead of the wing center of lift so the tail plane is providing negative lift in level flight, many aircraft when fully loaded have the tail plane providing some positive lift. I flew my Comanche 250 from Denver to Duluth, MN, on to DSM, and back to Denver with 4 passengers and baggage to the point that I only could fill the inboards to stay below 2900 lbs (max gross). The trim was very much different at all speeds. With just two in the front seats and no baggage, the trim for approach is much more up elevator trim than at cruise (tail plane has negative lift). But fully loaded, the trim changes very little as you slow up for approach. This could be because the CG is more aft fully loaded, so the tail plane is carrying some of the load.
I have never been totally happy with the DC3 ground handling. It has always been too slow on acceleration in bringing the tail up and it would try and fly with the tail still on the ground and if you tried to get the tail up with forward pressure, it was way too easy to get in a porpoise. Moving the CG as far forward as possible helped and increasing the horizontal stab effectiveness also helped. I had also made the length longer. The real DC3 tail came up very quickly, very similar to the cub in reality. I have not flown the fgfs DC3 since the recent changes. I will try it and then comment some more.
Good discussion, Dave P.
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