Sideslip

[pwill435]

Are there any limitations or personal experiences to sideslipping in regard to flap settings? Is slipping with full flap OK? Also is the ASI a useful guide when slipping or should we just maintain attitude? I cannot find reference to any of this in the POH.

[randylervold]

CC11s (Carbon Cub, Sport Cub) slip just fine with full flaps, and you can really get them to come down nicely in a full rudder slip. I've seen a 1,200 fpm descent in such a slip and it is very controllable so you can fine tune your descent profile as needs dictate. There may well be some ASI error but from what I've seen it is minimal. Just keep it in the normal final approach speed range and slip away!

[Pilawt]

CC11s (Carbon Cub, Sport Cub) slip just fine with full flaps, and you can really get them to come down nicely in a full rudder slip.

I did that just this morning in my Sport Cub! For a nice, short approach from downwind abeam the numbers I just crank it all the way around 180 degrees in the slip, modulating the amount of slip as needed for the desired glide path. Fun!

I do notice a very mild "pitch pumping" in the stick in a slip with more than one notch of flap. This is probably from the vortex of the outboard end of the wing-down flap grazing the outboard end of the elevator. No biggie, it's just the airplane talking to me.

Some pilots believe slips with flaps are inherently bad, that they somehow "blank the tail". No and no. The grain of truth that gave rise to the mythology stems from the experiences of Cessna test pilots during development of the C-170 and C-172. Here's what former Cessna Manager of Aerodynamics and Flight Test William Thompson said in his book, Cessna - Wings for The World: The Single-Engine Development Story:

With the advent of the large slotted flaps in the C-170, C-180, and C-172 we encountered a nose down pitch in forward slips with the wing flaps deflected. In some cases it was severe enough to lift the pilot against his seat belt if he was slow in checking the motion. For this reason a caution note was placed in most of the owner’s manuals under “Landings” reading “Slips should be avoided with flap settings greater than 30 deg. due to a downward pitch encountered under certain combinations of airspeed, side-slip angle, and center of gravity loadings”. Since wing-low drift correction in crosswind landings is normally performed with a minimum flap setting (for better rudder control) this limitation did not apply to that maneuver. The cause of the pitching motion is the transition of a strong wing downwash over the tail in straight flight to a lessened downwash angle over part of the horizontal tail caused by the influence of a relative “upwash increment” from the upturned aileron in slipping flight. Although not stated in the owner’s manuals, we privately encouraged flight instructors to explore these effects at high altitude, and to pass on the information to their students. This phenomenon was elusive and sometimes hard to duplicate, but it was thought that a pilot should be aware of its existence and know how to counteract it if it occurs close to the ground.

I've never heard of the pitch-down phenomenon ever occurring in any airplane other than a C-172 earlier than 1972. The '72 Skyhawk introduced a larger dorsal fin that apparently solved the problem. The old C-172 owners manuals did say that slips with full flap were "prohibited," but the TCDS (which is the legal authority) only says "should be avoided."

But that does not apply to our Cubs, and as Randy says, slip away!

[pwill435]

Thanks for that, nice to be reassured.

[seastar]

I've been slipping my CC with full flaps since I've had it -- glad to hear it's OK.
"I" have also been slipping. Gets worse every year LOL
Bill

[Centmont]

Please forgive the hijack...Geo...sorry about the loss of your friend. You, more than anyone I know, enjoys each day to its fullest. May it be so for a long, long, time.

The landing Gary describes is the landing I was taught from the very beginning by one of Montana's best old bush pilots... He would take me to altitude and fly with full flaps trying to stay in that narrow zone where the wing is partially stalled. You come right down and under control. That said, it is still enormous fun to slip in the upwind to base to final turn, then use Gary's landing on final. Accurate speed control is the key to any short controlled landing... Great post Gary...good discussion. R

[couleeone]

Never know Gary, that is on my bucket list to visit friends in Florida!

[pwill435]

The slipping is proceeding exceptionally well, great fun. Now my question is what minimum IAS are people using in the slip? This is for getting into tight fields.

[randylervold]

Now my question is what minimum IAS are people using in the slip? This is for getting into tight fields.

Minimum IAS would be just above stall speed. Really, since the gross weight stall speed when flying straight is 31 mph you can slip right down to maybe 35 mph, though please be very careful at those low airspeeds close the ground. Since stall speed is 31 mph I have no problem slipping down to 1.3 Vso or 40.3 mph. Of course wind shear, CG configuration, and flying weight all come to bear on this and must be considered, along with a reasonable margin for error as with all phases of flight. You will find the CC11 is very controllable right down to the stall and can be slipped right down to roundout and flare. Heck, when you cross control into a crosswind you're landing in a slip.

Have fun and be safe!

[seastar]

if you have an executive Glass panel it's fun to hear it start screaming "sink rate, pull up, pull up" when in a max performance slip.
You can get down in a big hurry. I use the slip capability all the time.
Bill