Slipping with Flaps

[Joe Moilanen]

Sounds like you passed the BFR and he flunked it...

Joe

[twlareau]

I was on down wind and decided to slip with 30 deg of flaps to make a short approach and lo and behold the dreaded nose tuck started. It was unnoticeable to my passenger but I could feel it developing. My aircraft tends to run on the nose heavy side of things. It was an interesting lesson, in my airplane you don't have to be at full flaps for the elevator to get washed out. Just passing it along.

[GAHorn]

That particular "CFI" needs to be counselled by FAA right after he exits the ER with his broken nose. A CFI has an obligation to STRESS the limitations of an airplane. The BFR stands for a flight REVIEW of items which may have become fuzzy memory in the operations of the pilot. Instead of reminding you of that hazard...he ignorantly violated the limitation, and likely made up a quick-response (crosswind B.S.) to try to cover his ignorance. He needs to be reminded more forcefully.

In a crosswind landing, will full flaps and a slip applied to reduce drift, the airplane is immediately above the touchdown. (The recommended technique is to crab to counter the crosswind until ready for touchdown, then "kick" the crab out for actual touchdown. SLIPS with full flaps in a B-model should be PROHIBITED.

And so is flying with stupid people who represent themselves as better than the aircraft limitations. I also know of a few drunks who drove....until they killed someone.

Addendum: There has recently been posted on You Tube a self-appointed “expert” who describes what he believes is the explanation of the aerodynamics of what happens to the horizontal of an airplane when flaps are deployed. (He claims the flaps create a down-wash that “pushes” the tail “down” thereby correcting the nose-heavy airplane. Unfortunately, he borrows information from a fatal accident suffered by one of Our Members to inflate an image of his expertise.
He is UN-informed and unfortunately the WWW/Internet lets these sort of things get distributed to the unwary.

The elevator/horizontal-stab Does Not rely on “downwash” from flaps to “push” the tail down to keep the nose up. If it did…then zero flaps would result in a nose-dive. Doh.

The horizontal stab of an airplane behaves like an upside-down wing. It provides Downward Lift….off-setting the nose-heaviness of a longitudinally-stabilized airplane about the C.G. (Think of a Lever and Fulcrum: The fuselage is the Lever…the Center-of-lift ..the wing… is the Fulcrum. The Tail pushes Down holding the Nose Up. The downwash of full flaps on the 170-B creates an Increase in Angle-of-Attack of the horizontal stab….bringing it very close to a stall. If a slip is then introduced, the fuselage can “blank” the downwind side of the horizontal…resulting in sudden Loss of downward-lift of the empennage … and a sudden nose-down pitching moment of the airplane. The rudder applied to support the slip…now imparts a “spin” to the airplane.
A steep nose-down with a “spin” (rotation) of the airplane can require more than a Thousand Feet of altitude for recovery. This altitude requirement doesn’t exist on short final. Slipping a B-model (and many other high-wing Cessnas) with full flaps can kill you.