Page 27 - Volume 13 Number 9

To prevent this coasting travel, Beech uses a Dynamic Brake Relay. It does the following: Whenever power is removed from one field winding, the other winding is now shorted to the airframe. This puts an “infinite” load on the winding that is acting as a generator. With huge resistance to rotation being provided by that winding and no longer any driving force being received by the other winding, the assembly comes to a screeching halt. It acts as if some strong mechanical brake were suddenly applied to the motor’s output shaft but it is all done by a magnetic field, not by a physical brake. Cool!
The Dynamic Brake Relay operates whenever the flaps hit a Limit Switch – Up, Down or Approach. It also activates in earlier King Airs – the ones in which the flaps may be stopped in any position between Approach and Down – when the flap handle is moved from Down to Approach while the flaps are extending between Approach and Down. The fact that the flaps will stop immediately means that when we want to put them at 60%, we can wait to move the handle from Down to Approach until we see the indicator pointing right at 60%. They won’t coast on down to 65% or more, not with our Dynamic Brake friend!
What if they do coast a bit? If this is happening, you will likely also find no free play on the flaps when you move their trailing edges up and down on the preflight
inspection since they have coasted to the ends of the tracks. The likely cause of this is a bad Dynamic Brake Relay or highly worn flap motor brushes.
Back to the motor/gearbox connection: The output shaft of the motor acts as the “worm” that rotates two shafts, “worm gears,” one rotating clockwise and the other counterclockwise, or vice versa, depending on whether Up or Down is selected. Both left and right outboard flap segments are connected to one of these shafts and the inboard segments are connected to the other shaft. Although extremely rare, if one of these shafts experiences a stripped gear such that the motor cannot drive it, then we would lose both left and right inboard or both left and right outboard flap segments ... it would never present us with an asymmetrical situation.
In 1975, a colleague of mine was delivering a factory new E90 to Beechcraft West, a Beech distributorship in Southern California, located at Van Nuys (KVNY). In those “good old days” no flight restrictions existed over the Grand Canyon so on their descent into Las Vegas for a refueling stop, they were enjoying the canyon views while descending near redline speeds over the Colorado River. As the passengers “oohed and aahed” their way in the descent while the pilot S-turned over the canyon, my friend suddenly felt the airplane balloon upward. “Oops, I think I just touched something!” said
Comprehensive support for all areas of your King Air
Paint and interior: Total and Partial Refurbishment.
Avionics: G1000 upgrades, Wi-Fi, Text, and Cabin Entertainment
Service Department: Phase Inspections, Component Overhaul, Mods and Upgrades from Advent, Blackhawk, BLR, and Raisbeck.
Prop Shop: Overhauls, Exchanges, Repairs, STC Conversions
ONE STOP, for all your King Air needs.
Yingling, the premier full service MRO/FBO in the Southern Plains. Everything you need in one stop to make your King Air beautiful, current on technology, and wheels-up ready when you are.
Interiors
Exterior Paint
Winglets
Prop Sales & Service
316.943.3246 or toll free: 800.835.0083 \[ FBO OPEN 24/7 \] http://www.yinglingaviation.com
LOCATED AT THE DWIGHT D. EISENHOWER NATIONAL AIRPORT2010 AIRPORT ROAD, WICHITA, KS 67209
Avionics
Service (Airframe and Engines)
Contact us for Equally Comprehensive support for Citations
SEPTEMBER 2019 KING AIR MAGAZINE • 25