[AT] OT truck tires/driveshaft?

[Chuck Bealke]

On 5/19/2014 6:28 PM, Dave Rotigel wrote:
> I'm sure we are all aware of the vibration that occurs as the landing gear on airlines is lowered in preparation for landing. Is that vibration caused due to tire imbalance, driveshaft misalignment, or the fact that the front tires are filled with nitrogen while the rear tires are filled with only air? Or could this simply be a factor of the tires back in the shop being square?
> 	Dave
>
Dave,

On the transports I worked and sometimes rode on in Uncle's Air Force 
(with gear design and parts shared with the Boeing 707), it seemed like 
the noise and vibration during and after lowering of gear came mostly 
from hydraulics and powerful air currents swirling around when the gear 
(and flaps about the same time) were lowered. These could be a little 
noisy, as Uncle did not seem as big on soundproofing for the passenger 
cabin as the airlines are.  As I recall, the tire rotation for main gear 
on our planes was easily stopped by automatic brake application after 
takeoff as an early part of the gear retraction sequence, and the much 
smaller nose gear tires stopped spinning when they made contact with 
brake pads in the nose gear wheel well. Tires were not spinning on touch 
down, though some research had been done in that direction with the 
intention of greatly improving tire life before the idea was rejected.  
Suspect that the biggest vibration producer on most landing commercial 
airplanes today is air turbulence around spoilers fully extended from 
the wing.

Chuck Bealke
Plano, Texas