Page 25 - October 2022

the propeller levers fully forward before selecting reverse so, in our C90GT example, the PPG should again be set for 1,900 RPM. The FTG is now waiting to operate at 1,805 (1,900 x 0.95). Perhaps I should remind the readers here that Maximum Reverse power should not cause propeller speed to ever get this high. On the other hand, if Maximum Reverse is selected while the prop levers are not fully forward, remaining in their descent or cruise position by mistake, there is a good chance the FTG will be activated, power will be limited, and Reverse will not be nearly as powerful as you were expecting. That’s why we have that “Reverse Not Ready” annunciator light that doesn’t extinguish until the propeller levers are forward.
Here’s a rhetorical question that does not really have an answer: At what speed is the primary propeller governor operating when in feather?
Like I said, there really is no answer for that question. But would you buy the fact that it is very, very, low, well below the lowest governor speed setting? In fact, in feather with a shutdown engine the propeller should stop, right? So maybe we’re kinda, somewhat, sorta setting a PPG speed of 0 RPM, eh?
Do you see where I am going with this? What is 6% faster than zero? What is 5% slower than zero? Zero times anything is still zero, right?
So perhaps that leads to a bit of insight of why sometimes the FTG gets involved in feather even when it should not ... all those speeds come rather close together down there at the bottom end of the governor speed range.
Having read this article, the next time you do your run-up feather check, let the propeller speed stabilize as low as it will go and carefully check all of the other gauges, too. If you see a decrease in N1, leading to an increase in ITT, add that to your squawk list and have your PT6 guru set the rigging properly to eliminate that fuel topping governor interference. KA
King Air expert Tom Clements has been flying and instructing in King Airs for over 50 years and is the author of “The King Air Book” and “The King Air Book II.” He is a Gold Seal CFI and has over 23,000 total hours with more than 15,000 in King Airs. For information on ordering his books, contact Tom direct at twcaz@msn.com. Tom is actively mentoring the instructors at King Air Academy in Phoenix.
If you have a question you’d like Tom to answer, please send it to Editor Kim Blonigen at editor@blonigen.net.
Correction
Thanks to longtime Beechcraft employee (and customer*) Bob Conrad who wrote in to point out some items that needed corrected from the Hall of Fame article in the June issue of King Air magazine.
The first flight of the King Air was Jan. 20, 1964, not Jan. 24. Apparently that date has been referenced in error before. Also, the Model 80 was suggested by LeRoy Clay to put a turboprop on to form the King Air, not the Model 88.
*Bob’s first Beechcraft was a tri-gear H-18 and his last was a King Air A-100. KA
OCTOBER 2022
KING AIR MAGAZINE • 23