Originally Posted by
sandiego89
Is there a ground handling reason why the nose wheel or tire (tyre for my UK friends ) is smaller than the main gear tire(s) on most conventional tricycle aircraft?.........Any handling reasons?
Actually - most of the time it is the other 'way around. The light, small nose gear
creates handling problems. Not unlike small light
tailwheels, except different types of problems. But in both cases, the weight and drag reduction is considered worth the (hopefully minor) ground control problems.
For nosewheel:
-
less friction grip for steering - pilot often needs to apply nose-down elevator during taxi and early TO run to insure a firm nose-wheel grip and steerability. Until speed is high enough for rudder steering.
-
wheelbarrowing. Touching down and rolling
only on the nose gear due to excessive speed and need for low angle of attack to settle to the runway. (Cue photos of DHC-4 Caribou doing this intentionally - bad technique otherwise)
-
porpoising subsequent to a wheelbarrow landing. Downward inertia of aircraft pushes main gear down to surface, thereby reducing nose-down attitude and increasing AoA/lift just when it is not needed. A "bounce" due not just to gear springiness but also the positive change in AoA and lift. Can become a phugoid with poorly-timed pilot reactions and corrections (PIOs) - bouncy-bouncy-bouncy-CRUNCH.
-
Special TO/Landing techniques needed for soft-field/rough-field TOs and landings (grass / gravel / dirt runways). Effectively, using
full nose-up elevator to lift the vulnerable nose wheel out of the grass and off the surface:
1) On takeoff, ASAP, and until the plane can lift off at very low speed in ground effect, and then accelerate free of the surface to full flying speed while remaining just .5m or so above the surface.
2) On landing, holding the nosewheel off the surface until slowing to the slowest speed possible. Both require delicate and carefully-judged use of the elevator, and because the nosewheel steering is intentionally unavailable except in the very slowest parts of the TO/landing rolls, can be tricky in crosswinds.
Nevertheless, worth it to reduce the weight, weight & balance, and drag penalties.