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Flaps - Infinitely Selectable? - Tom Clements, King Air Academy


Flaps - Infinitely Selectable? - Tom Clements, King Air Academy

If you are used to flying one particular King Air but then get the opportunity to fly others, you will find a surprise or two…and one of these relates to flap operation. All current-production King Airs have three-position flap systems. Where you place the flap handle is where the flaps should go and stop: Up, Approach, or Down. It is simple and easy. About the only concern is to abide by the flap limit speeds – and I prefer being 20 knots or so conservatively under the limits, when practicable – and verify that the flap indicator shows you what you expect.

Earlier model King Airs, however, have a flap system that is greatly different in the Approach to Down realm. When the flap handle on these models is placed to the center, Approach, position, what happens depends on whether you have come to the center position from the Up or from the Down position. Let me explain.

In these models, moving to Approach from Up yields the identical action as in the later models: the flaps move to Approach and stop. Coming up to Approach from Down, however, causes the flaps to stop right where they are.

If you have set 100% flaps for a normal landing but then must do a go-around, here’s an opportunity to use your Four Friends: Power, Props, Flaps, and Gear. You push the power levers forward aggressively, stopping at your normal takeoff torque or ITT setting. Next, you smoothly run the propeller levers fully forward. Since this causes the torque to drop appreciably, don’t be timid about using the full torque limit when you pushed the power levers forward, if ITT is not limiting Now it’s time to retract the flaps, and here’s where a big gotcha awaits those of you used to the newer three-position system.

If we move the flap handle up one notch, from Down to Approach, nothing happens! As I wrote above, “Coming up to Approach from Down causes the flaps to stop right where they are.” When we next retract the landing gear, the gear warning horn starts to sound (on most models), triggered by the fact that the flaps are extended greater than Approach without all three gear legs down and locked. So we have a blaring horn and a poorly-performing airplane since the flaps are still fully down. Yuck!

On these earlier models, the way to retract the flaps to Approach from Down is complicated enough that I do not recommend the single-pilot operator to do so. Instead, merely delay flap retraction a moment longer, to make certain that you are comfortably in the green arc on the airspeed indicator, then bring the flaps all the way up in one step by moving the flap handle to Up. Even for the two-pilot crew, this is a good option.

But if the two-pilot crew wants to do the “optimum” procedure, performance-wise, then power and props come first and second, flaps to Approach comes third, gear retraction comes forth, and then final flap retraction takes place last after 400 feet and Vyse are both achieved.

To get the flaps from Down to Approach, the copilot must move the handle fully to Up, watch the flap indicator, and exactly as the flaps reach the Approach setting he/she must then move the handle down one notch to Approach.

If the copilot does this too fast and returns to Approach when the flaps are a bit greater than Approach, they stop right there. This leads once again to the blaring gear horn when the gear starts coming up. On the other hand, if the copilot is too late and the flaps have reached a setting between Up and Approach when the handle returns to the center, then the flaps immediately reverse direction, move down to Approach, and automatically stop there. This does not harm the flap system in any way.

Due to the complications and potential for errors in this procedure, I prefer to make a one-step, Down to Up, flap retraction even when operating with a copilot.

On the other hand, there is one distinct advantage to the earlier-style system. Since the flaps are infinitely selectable at any position from Approach to Down, we can use a third or even a fourth flap setting when landing in visual conditions. We could stop the flaps at, say 60%, when on base leg, and then perhaps at 80% when rolling out on final, and finally going to 100% at 500 feet above touchdown. This is done by moving the handle from Approach to Down, watching the indicator, and returning to the center position when the indicator shows what we desire. Due to the dynamic braking system that the flaps have, there is no need to anticipate and move the handle back to Approach early. Some people, including me, like to use that 60% setting momentarily – it leads to less trim and pitch changes taking place all at once – but others find it more work than necessary. To each his own!

There is, however, one definite benefit of making an intermediate flap stop between Approach and Down: It forces you to watch the indicator. Remember, people, controls are not indicators. Just because the flap handle or gear handle gets repositioned, that is absolutely no guarantee that the expected action actually occurred. Flap indicator, a visual check outside, green gear lights, red lights in the gear handle…all of these are the things that confirm what is actually happening.

I’d be a richer man today if I had a dollar for every time during my years of active King Air flight training that the trainee missed the fact that the flaps and/or landing gear did not do what he or she expected. (Damn those instructor’s fingers having access to circuit breakers!) Taxiing back for takeoff after many a full-stop landing, my line was, “Well, I have good news and bad news. The good news is that you make a reasonably good no-flap landing. The bad news is that you did not realize you were making a no-flap landing!”

To close, the easiest way to know for sure which style flap system your particular King Air has is to run the flaps fully Down once before your first takeoff in this particular serial number, move the flap handle back up one notch to Approach, and observe whether they return to Approach or stay Down. If they come back to Approach, you, of course, have the newer three-position system. For those readers who want to know now, the newer system is on all C90Bs and after (not C90As), all 350s, and all 200-series after BB-1443, including B200GTs and 250s. That means that all 90s, A90s, B90s, C90s, C90-1s, E90s, F90s, F90-1s, 100s, A100s, B100s, straight 200s, 300s, and B200s prior to the 1993 year model all have infinitely selectable flaps in the range from Approach to Down. That’s a lot of airplanes!

Author: Tom Clements, King Air Academy

Image: Textron Aviation