Fact or fiction?

[Little Bird]

Anyone heard about powering on a helicopter when under tow so as to not ruin the gyro instruments?

Thanks!

 

[Eric Hunt]

Yup. Having the (older) gyro instruments spinning at normal revs apparently reduces bearing damage as you roll over the bumps.

 

Not sure if the new solid state stuff needs it, probably not.

[Little Bird]

Well there you go. This is my 5th company and first I've heard of it. Thanks Eric.

[avbug]

The gyro instruments need to be fully spun up before moving, if that's the intent. Aircraft are moved all the time without powering the gyro instruments, and on aircraft that use vacuum power, it's not practical or possible to spin them up to move the aircraft.

 

Aircraft that sit on the flight line and move in the wind do more damage to ruby bearings and other balance surfaces for the gimbals than normal operation with the gyros spinning.

[Rupert]

Gyros run on inertia for a long time after shutdown. As the gyros slow down, they can really bang around if moved prior to full gyro stop. So, if moving an older steam gauge helicopter within a few minutes after shutdown, power up the gyros. Moving the helicopter will not damage full-spinning and/or non-spinning gyros; only slow-spinning gyros. Does not apply to helicopters with modern instruments. Do what your employer says.

[avbug]

Moving a helicopter, or any aircraft, with the gyros at rest will cause wear; anything which causes any motion on the ruby bearings will cause wear, and increased precession. If an aircraft is bounced around for lengthy periods, whether on the ramp in wind for some aircraft, or in transit, or otherwise, wear is allowed to occur on other than an erect gyro, performance of the gyro will be degraded due to wear at the bearing points and increased precession.