This month’s article will cause you to put on your thinking caps and consider some King Air systems questions that you probably haven’t seen or heard before. I am going to present six questions to have you ponder for as long as you need, then I will provide my answers … the correct ones, I hope! Good luck … and have fun!
The Py line – the air-filled tube connecting the Fuel Control Unit (mounted on the aft accessory case) to the Fuel Topping Governor (mounted on the nose case) – becomes entirely blocked. This renders the Fuel Topping Governor (FTG) totally inoperative. (The over-torque limiter also, for the 200-series.)
What effect will this have on your next normal flight?
How would you discover that the FTG is inoperative?
You are preparing to enter visible moisture during steady-state cruise flight with an IOAT of -20°C so you turn on Engine Anti-Ice (extend the ice vanes). Will propeller blade angle (A) Remain the same; (B) Decrease, go to finer pitch; or (C) Increase, go to coarser pitch?
After turning on Engine Anti-Ice as in the above question, what have you done to your fuel efficiency? Has Specific Range – the distance traveled while consuming 1 pound of fuel, expressed in units of nm/lb and calculated by dividing ground speed by fuel flow – (A) Remained the same; (B) Decreased; or (C) Increased?
You started the right engine first and you blew the right Current Limiter (CL) during the generator cross-start of the left engine.
When you check Generator bus (Main bus) voltage after both starts are completed and before turning on the left generator, what will they read?
Extra Credit Question: Which is the only King Air model that specifically prohibits generator cross-starts?
True or False: You must always close the cabin door, with the handle rotated to the locked position, before moving the airplane with a tug.
While descending on the final segment of a precision approach, with flaps at Approach and landing gear Down, the right engine flames out due to fuel starvation. What, if anything, must the pilot do to allow Autofeather – whose switch is in the up, Arm position – to operate?
ANSWERS:
A. Absolutely no effect whatsoever. For the FTG to be needed in flight the Primary Propeller Governor (PPG) must fail in such a manner that the propeller speed increases. Also, once the propeller levers are advanced fully forward – Power, PROPS, Flaps, Gear; remember? – then the Overspeed Governor should prevent the FTG from ever being reached. PPGs are one of the most reliable of all systems.
In the event of using Maximum Reverse and with some mis-rigging of the engine controls, then there is a chance the FTG would activate. But since this is “your next NORMAL flight” that won’t be happening.
B. Surprisingly, there is no check the pilot ever makes of the FTG. Even during the routine maintenance Phase checks it is never examined. Yes, there is a way to test it from the cockpit but that is very rarely done and merits its own discussion at a later date.
The answer is B: The blade angle will decrease slightly, moving to a finer pitch.
Since the activation of Engine Anti-Ice causes a power reduction and that in turn causes an airspeed reduction, both results would cause a fixed-pitch propeller to slow down. Hence, our Constant Speed propeller governor – the PPG – will decrease the blade angle to allow less rotational resistance and keep the propeller speed from decreasing.
If you have read “The King Air Book” you know the mind-boggling answer: (C) It has increased. Since the FCU is merely an N1 governor, it will reduce fuel flow in reaction to the thinner air that is providing less rotational resistance to the Gas Generator portion of the PT6. Airspeed will also decrease due to the decrease in power. Surprisingly, however, the reduction in airspeed is a smaller fraction than is the reduction in fuel flow. Does that make you feel any better about the loss of airspeed the Ice Vanes cause?
I need to say one more thing. Although this increase in Specific Range occurs in almost every situation, there is one exception. If you are at very high altitude while using Best Range Power instead of Normal or Maximum Cruise Power, then the loss in power caused by vane usage can send you to “the backside of the power curve” and cause Specific Range to decrease. I bet none of you routinely fly this way, right?
A. You should see normal voltage on the right Generator Bus. Some POHs state the normal range as 27.5 to 29.0 volts. The voltage regulator portion of the GCU (Generator Control Unit) should be set for 28.25 ± 0.25 volts and the gauge can have up to a 0.5 volt error and still be within specifications. This combination leads to the stated allowable range of readings.
The left Generator Bus should read slightly less, around 24 volts, since it is only “seeing” the battery’s voltage. I find that many pilots think the voltage would be zero with a failed CL. Without a generator operating – before start and after shutdown – then a failed limiter is obvious because the voltmeter reads nothing on that side. But the after start CL check … different story!
B. Although I personally do mostly generator-assisted starts, not actual cross-starts on all King Air models, the only POH that requires this is for the 200s and B200s prior to BB-1444. Beginning with 1444 a cross-start current depression system was included in the GCU but previous 200s do not have that. The load required to turn the small-core PT6 starters very rarely causes a CL failure, although it happens at times. The larger core PT6A-41s and -42s (200 and B200 engines) leads to more starter load and quite a rash of blown limiters. That’s why leaving the operating generator on while activating the opposite start switch is a No-No.
False. The King Air fuselage is strong by itself with a closed door not being necessary for added strength. Of course, it is fine to close it and there is no chance of hitting some object on the tarmac with it closed.
And by the way, I suggest not rotating the handle to the fully locked position when towing the airplane or leaving it in a secure hangar. Only move the handle to the Locked position when you plan to use your key to truly lock the door. This puts less stress and strain on the latch bolts, J-hooks and door seal … at least I think so. Just turn it far enough – maybe 45° – to keep the door from dropping open.
Autofeather can only operate when (1) the switch is in Arm; (2) both power levers are well-advanced, in the range of 90% N1 or above; (3) the torque on one side is above about 400 ft-lbs or 17%; and (4) the torque on the other side is below about 200 ft-lbs or 10%.
The power setting for a two-engine ILS or LPV won’t have the power levers advanced far enough. Thus, the first step – Power! – is to double the torque on the remaining engine by pushing BOTH power levers forward. If you push only one forward, you have moved step 5, Identify, to step 1 of the “Suspected Power Loss” drill. That’s bad!
As a piece of trivia: The bottom position of the Autofeather switch – TEST – eliminates the need for BOTH power levers to be advanced. In this scenario, holding it down would cause feathering of the flamed-out engine. But you’d still need to add power on the other side sometime!
How did you do? Did I make you think? Answering all questions correctly does not mean you are necessarily a “better” pilot. However, I strongly believe that the more we understand our airplane’s systems the easier it is to become the pilots we want to be.