Effects of Aerobatic Maneuvers on Gyros

 

Manufacturers have come to the conclusion that as long as gyros are free or uncaged during these manoeuvres, aerobatics or the g-loads connected with them won't significantly impair or decrease the life of running gyros. Due to the huge angular momentum of the spinning mass and the ensuing quadrature forces, locking the gyros in a caged position during these movements may harm the spin bearings and/or gimbal bearings. The ideal strategy is to leave the gyro free while performing aerobatic tricks and use caging to reset it as necessary while flying straight and level.

The rotor of a directional gyro can be easily raised into a horizontal plane and aligned with the magnetic compass using the gyro's caging capability. The heading card may begin to spin while doing aerobatic manoeuvres; in this case, the pilot should pull the caging knob to stop the spinning. He should pull the caging knob and line up the heading card with his magnetic compass once he is back in level, straight flight.

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Standard Horizon Gyros without a Caging Feature: These gyros have 360 degrees of roll freedom and roughly +/- 85 degrees of pitch mobility. During full loops, erection and the appropriate pitch and roll information are maintained through controlled precession. The Horizon Gyro will maintain its erection (spin axis aligned to the dynamic vertical) and offer accurate pitch and roll references for the majority of aerobatic manoeuvres. The Horizon Gyro may, however, be susceptible to specific moves that could result in it losing its vertical reference and even "spinning out." The main drawback to this situation is that it could take 10 to 20 minutes of level flight before the Horizon Gyro is fully built and supplying accurate pitch and roll data.

With caging added to the Horizon Gyro, the pilot can return to level flight (*using the earth's horizon as a reference) and pull the caging knob to instantly align the gyro rotor with a vertical reference if the gyro tumbles during an acrobatic performance. Depending on how successfully the pilot aligns his aircraft with level flight during the caging procedure, the gyro indication may be a few degrees off, but the pilot will still have valuable pitch and roll information, and a tiny inaccuracy will be corrected by the internal erecting system in 2 or 3 minutes.

*Only perform aerobatic movements in VFR flight with a clearly visible earth horizon as a point of reference.

I'm Jerry Bishop, a private pilot who has owned and restored a number of classic aeroplanes. I have 45 years of experience designing aviation instrumentation (gyros, vacuum pumps, and engine instruments). Visit Pilot One [http://www.pilotone.com] for a bit, then head to Jerry's Hanger for tales, images, and information for pilots. I enjoy reading online about aeroplanes.

 

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