Mazza wrote on Oct 7
th, 2007 at 6:15am:
okay guys here's something for the books...... when i talk about flying i mainly am referring to small acrobatic props and military jets and medium props if i'm talking about anything i'll metion what it is
In lighter nosewheel aircraft (some fighters like the Grippen are "small" but are
heavy), you really should not try to force the nose down on the rollout.
The reason has less to do with aerodynamics than with leverage.
An airplane with a nosewheel has a CG that is ahead of the main wheels. So if you force the nose down, that mass will start to pivot forward with the nosewheel as a fulcrum instead of the mains. Even if the nosewheel stops completely, that mass wants to keep coming forward. Right? It's a problem with a lighter plane because there is not enough weight to keep the tail down, but enough to start moving up around that pivot point.
So now the airplane is not keeping itself straight on the rollout as any good "trike" should when the fixed mains have touched down aligned with the runway... it's mostly on that one wheel, a wheel which can pivot.
This can be a bad thing.
Smaller trikes can easily "wheelbarrow", which often means a trip off the side of the runway, because the ailerons and rudder are useless at that speed, and the plane will not steer well with all of its weight on the nosewheel. Or even most of its weight.
Assuming the nosewheel doesn't collapse, often taking the engine mount with it... it's usually not made to take that kind of force.
Bottom line here is: the nosewheel is not the desired fulcrum.
As you roll out, you want to use "up" elevator to use as much of that weight aft of the mains as you can to keep the mains glued to the runway, balanced with the weight forward of the mains, and use the
bottom of the wings for drag until the nosewheel comes down (or is put down- some trikes need nosewheel steering earlier than others).
Or so it seems to me...
Pages: 
