smoss wrote:hold the nose entirely on the ground until 59 KIAS
If I did that in my aircraft, it would be the only wheel on the ground at that speed! Why do anything so risky when the problem is easily fixed by tightening up the wheel pivot?
Another symptom is the amount of rudder you need to hold in medium to steep turns, as gravity pivots the wheel. I flew another aircraft in formation with mine and could see this happening, before having the tightness adjusted.
smoss wrote:hold the nose entirely on the ground until 59 KIAS
If I did that in my aircraft, it would be the only wheel on the ground at that speed! Why do anything so risky when the problem is easily fixed by tightening up the wheel pivot?
wow, you must be very light. At 59 (POH rotation speed) with forward trim all 3 wheels of my plane are fully planted on the ground and stable until I pull back, whether light with just me (150 pounder) or fully loaded.
Seriously though, forcing the front wheel to stay firmly on the ground at high speed is asking for trouble - even if it's just extra maintenance costs. There's a reason why we're tought to hold it off as long as possible after landing.
It seems to me like you would be better off to lift the nose a bit early rather than hold it on extra-long. Wouldn't there be less chance for lateral nosewheel movement with the mains still firmly planted, as opposed to when all three wheels are loosing grip? I would think holding the plane down would make the nose wheel problem worse, not better.
I can't prove this - it's just my armchair theory. If the plane wasn't in annual right now, though, yesterday would have been a good day to experiment - 280@22G45, plus a 20kt wind shear at 100' AGL!
I can tell you I've tried it both ways, and how I do it now is the most consistenly neutral on takeoff. I think the difference is that when you lift the nosewheel off early, it comes off more slowly, with say a 1/2 second transition from weighted to off the ground, during which time it gets "lighter" and can shimmy or whatever, vs. when you "pop" it off the ground after Vr, it has only say a 1/100 second transition from fully weighted to 0, and just stays where it was rolling. Give it a try a few times... if it solves your problem, great, if not, keep playing.
I am wondering... Maybe giroscopic effect plays a role here? This could explain some tricks working better or worse once the pivot nut is loose (than giroscopic forces being able to move the wheel).
smoss wrote:For me, it is definitely just an issue of being aligned at takeoff with correct aileron correction for any crosswind. No crosswind - always straight in flight. Crosswind takeoff done well - straight in flight. Crosswind takeoff with not enough aileron correction, i.e. immediately drift off centerline after takeoff - always cocked and out of rudder trim for the flight. I can easily predict now right after liftoff whether it will be cocked or not.
Unlike other posters that suggested early rotation, when I bought my plane 2 years ago the guy I bought it from happened to mention the cocking nosewheel as an issue on DA40's and "instructed" me to takeoff initially with a bit of down/forward trim, hold the nose entirely on the ground until 59 KIAS, the quickly pop the nosewheel off the ground. I have done this ever since then (I takeoff with trim about 1 inch forward of center) and it works well... except for in a crappy crosswind takeoff.
Tried this yesterday in a no wind situation. Did not trim forward though but just pushed the nose down until I felt it want to porpoise. No joy---
Tech support at Diamond said that the test pilots use the rudder to swing it back into alignment. I haven't had any luck getting it perfect but with a few pushes I have had the bank angle reduce.
Pictures of my plane have the trailing edge of the wheel always out to the right when it is out of alignment. Wondering about the physics, would this cause the plane to want to swing left or right? A rudder deflection in this direction would cause a yaw to the right, or does the wind pushing on the fully exposed side force the nose left? The autopilot always holds the bank angle to the right when it is compensating which would indicate compensating for left movement. Therefore, if you bank left, would the pull of gravity alone straighten the wheel or move it more left? Has anyone tried different techniques?
Has anybody who is suffering from this problem actually tried having their wheel pivot tightened as I described on the first page of this topic? I'd love to hear the results.
Keith M wrote:Has anybody who is suffering from this problem actually tried having their wheel pivot tightened as I described on the first page of this topic? I'd love to hear the results.
Never had a problem with it for the first 150hrs and then it occurred frequently. I had it checked and the nose wheel was just below the lower acceptable range and was tightened to the max. It now happens intermittent which makes me think somewhere closer to the middle might be better.
