Spotlight: Raisbeck Engineering

About Raisbeck Engineering

Raisbeck Engineering continues the tradition of its founder, James D. Raisbeck. It is dedicated to improving personal, business and corporate aircrafts by positively affecting the performance, productivity, safety and comfort. Raisbeck does this through infusion of advanced technology with currently flying fleets

Raisbeck Performance Systems for the entire Hawker Beechcraft King Air family, as well as Bombardier’s Model 31 and 35/36 Learjet aircraft, are certified worldwide.

Raisbeck’s designs have been incorporated into OEM production aircraft since 1973. Raisbeck Performance Systems for King Airs are factory installed or optional equipment on Beechcraft 250, 350, B200GT and C90GTx production lines. They are also sold and installed by Hawker Beechcraft Service Centers and Raisbeck Authorized Dealers around the globe. For more information on Raisbeck Engineering, visit their website:

Raisbeck is dedicated to customer support, and has provided King Air Nation with helpful Q & A about the Raisbeck King Air propellers.

Troubleshooting your Raisbeck King Air Systems

Q: ”We operate a King Air 200 with Raisbeck propellers. On short final, the airplane sometimes ‘yazals’ as we reduce power. What’s going on?”

A: Your problem is most likely due to asymmetric propeller low-pitch stop settings. As you reduce both airspeed and power during approach to landing, your props can come “off the governor” at different airspeeds. This is not dangerous and is easily corrected. But it sure gets your attention!

The hydraulic low-pitch stops on your Raisbeck Propellers are set by rigging the propeller pitch stop-nuts. This is accomplished after statically measuring the engine torque at 1800 RPM with the propeller governors selected to full-increase RPM. The required torque value is a function both of airport altitude and outside air temperature. This torque setting is called out in both the Raisbeck Installation and Maintenance manuals.

While the per-engine torque setting has a generous tolerance (40 foot-pounds), the differential between left and right propellers is much tighter (within 20 foot-pounds).

When the torque differential between the left and right engines exceeds 20 foot-pounds, they will come “off the governor” at different airspeeds.

Thus, while you are decelerating and simultaneously pulling off power on short final or during landing flare, the windmilling drag of the two propellers will be momentarily different and cause your disconcerting “yazal.” It’s in the book (on our Web site, Maintenance Manual 85-120).

Aaron Jo-Nes is also available to discuss this and other troubleshooting topics by e-mail or phone at Raisbeck Engineering. [email protected]

Happy Flying!

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