Slipping with Flaps

[hilltop170]

Another thing to remember is the restriction on slipping is with FULL flaps. Less than full flaps is not restricted and I have never heard of anyone having a problem with less than full flaps.

Max flaps available on later 172s and 182s was reduced from 40 degrees to 30 degrees to eliminate the restriction on slipping.

[170C]

I have heard about not slipping with full (40 deg) flaps for years and I have read my 1956 Cessna 172 Owner's Manual/Businessliner numerous times although I didn't remember the caution about slipping with full flaps. So today I looked again and sure enough on page 32 under LANDING it states in the second sentence, "Slips are prohibited in full flap approaches because of a downward pitch encountered under certain combinations of airspeed and sideslip angle>" Quotation marks are mine. There is nothing in the text to draw ones attention to the statement. Its not bold, underlined or in capital letters. Easy to overlook I have likely been lucky thus far

[blueldr]

Many years ago I met a fellow from southern California named Bob Dentice at a fly in at Porterville, California. He had a rather odd looking tailwheel Cessna airplane on which I was pretty well stumped to identify. It had a "square" tail and set of cowling cheek bumps for a Lycoming engine, but there were no patches to indicate that the landing gear had been moved forward as is done on a C-172. He got a kick out of my identification dilemma and explained that he had "grafted" the tail from a wrecked C-175 on the wrecked C-170B. Took him two years to get it approved. He claimed that it absolutely would not get the violent pitch down of the stock C-170B on a maximum slip with full flaps. Of course, the C-175 tail is totally different and somewhat larger.

[GAHorn]

Another thing to remember is the restriction on slipping is with FULL flaps. Less than full flaps is not restricted and I have never heard of anyone having a problem with less than full flaps.

Max flaps available on later 172s and 182s was reduced from 40 degrees to 30 degrees to eliminate the restriction on slipping.

I believe the reduced flap settings for later 172 aircraft was for the purpose of increased gross weight....not for handling characteristics (which was only a happy coincidence.) The rear window necessitated a less-robust rear doorpost and associated structure, which in-turn neared the structural limits of full-flap stresses placed upon the doorposts of later aircraft when full flaps were applied at the increased gross weights. (The balked landing climb requirement also came into play but that was resolved with more horsepower...adding still more stress to the flaps/doorpost.)

[akclimber]

I was having a BFR yesterday and on one of the landings I was a bit high on short final so the CFI says to do a slip - I say can't it's prohibited with full flaps - he says watch - and grabs the yoke and stomps on the rudder - I in turn fight the controls and end up doing less than full on aggressive slip. I then tell him about this accident and he says since we had an 8 knot x-wind and were slipping with the wing down on the windward side, we wouldn't blanket the elevator. This in turn implies that slipping away from the wind or possibly in no wind will this tail stall occur.

[pdb]

How does the airplane know its in a crosswind?

I may be wrong but his reply strikes me as nonsense and his actions dangerous.

[johneeb]

I was having a BFR yesterday and on one of the landings I was a bit high on short final so the CFI says to do a slip - I say can't it's prohibited with full flaps - he says watch - and grabs the yoke and stomps on the rudder - I in turn fight the controls and end up doing less than full on aggressive slip. I then tell him about this accident and he says since we had an 8 knot x-wind and were slipping with the wing down on the windward side, we wouldn't blanket the elevator. This in turn implies that slipping away from the wind or possibly in no wind will this tail stall occur.

You had better find a new Check Airmen!

[bagarre]

I was having a BFR yesterday and on one of the landings I was a bit high on short final so the CFI says to do a slip - I say can't it's prohibited with full flaps - he says watch - and grabs the yoke and stomps on the rudder - I in turn fight the controls and end up doing less than full on aggressive slip. I then tell him about this accident and he says since we had an 8 knot x-wind and were slipping with the wing down on the windward side, we wouldn't blanket the elevator. This in turn implies that slipping away from the wind or possibly in no wind will this tail stall occur.

"Watch this...." Famous last words as I'd never fly with that jerk again.

Your CFI is an idiot.

[Bramlett]

I was having a BFR yesterday and on one of the landings I was a bit high on short final so the CFI says to do a slip - I say can't it's prohibited with full flaps - he says watch - and grabs the yoke and stomps on the rudder - I in turn fight the controls and end up doing less than full on aggressive slip. I then tell him about this accident and he says since we had an 8 knot x-wind and were slipping with the wing down on the windward side, we wouldn't blanket the elevator. This in turn implies that slipping away from the wind or possibly in no wind will this tail stall occur.

A smack across the bridge of his nose was in order. When you land you can fire him and proceed to finish the ass whipping.

[KG]

I'm curious.. .... what is the experience level of your CFI?

[cessna170bdriver]

..."Watch this...." Famous last words as I'd never fly with that jerk again.

Your CFI is an idiot.

Did he ask you to hold his beer?...

[akclimber]

The CFI is actually very experienced, having ran a part 135 air taxi up in Alaska for a while.
Has lots of float, ski, tundra tire time in Cessnas, Cubs, and Champs, and he is a very good bush pilot.
He is a little cavalier as his action demonstrates, and obviously not familiar with the full flap slip in the 170B. I do have to stress to him that how dangerous that move was.

Also regarding the comment as to how the airplane knows it's in a crosswind. I would venture to say that when maintaining runway centerline the airflow over the wings and tail would be different in a crosswind.

[pdb]

Also regarding the comment as to how the airplane knows it's in a crosswind. I would venture to say that when maintaining runway centerline the airflow over the wings and tail would be different in a crosswind.

Aerodynamically, slip is a slip and the crosswind makes no difference in the air.

[daedaluscan]

Also regarding the comment as to how the airplane knows it's in a crosswind. I would venture to say that when maintaining runway centerline the airflow over the wings and tail would be different in a crosswind.

As I see it the actual slip is different to maintain the centreline to accommodate the crosswind, but the airplane is completely unaware of the movement of the mass of air in which it is flying unless it is gusty.

[Bruce Fenstermacher]

The CFI is actually very experienced, having ran a part 135 air taxi up in Alaska for a while.
Has lots of float, ski, tundra tire time in Cessnas, Cubs, and Champs, and he is a very good bush pilot.
He is a little cavalier as his action demonstrates, and obviously not familiar with the full flap slip in the 170B. I do have to stress to him that how dangerous that move was.

Your CFI MAY have the experience and knowledge to understand when he can get away with a full flap slip in a 170B. But I believe it just as likely he is naive when it comes to the elevator stall and how quick it can put you in a place you don't want to be.

I think you need to discuss this with him and simply state that you do not wish to push the edges of the full flap slip envelope as Cessna warns against it. If he can not abide by your wishes he really is not the CFI for you regardless of his reputation or experience.