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Thread: Sideslip

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    Default Sideslip

    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.

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    Senior Member randylervold's Avatar
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    Default Re: Sideslip

    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!
    Randy Lervold

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    Senior Member Pilawt's Avatar
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    Default Re: Sideslip

    Quote Originally Posted by randylervold View Post
    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!
    Last edited by Pilawt; 05-30-2012 at 12:25 PM.
    Jeff Jacobs
    Vancouver WA / KVUO
    C-172N-180


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    Default Re: Sideslip

    Thanks for that, nice to be reassured.

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    Default Re: Sideslip

    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

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    Default Re: Sideslip

    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.
    Last edited by pwill435; 06-19-2012 at 08:18 PM.

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    Senior Member randylervold's Avatar
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    Default Re: Sideslip

    Quote Originally Posted by pwill435 View Post
    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!
    Randy Lervold

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    Default Re: Sideslip

    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

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    Default Re: Sideslip

    Quote Originally Posted by randylervold View Post
    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!
    Hi Randy ,
    Just back from Bluff Utah and Lori McNichols Mountain and Canyon Flying course which was amazing! Highly recommend it for anyone , only makes one a better pilot while having ball flying Gods Country. That said I did the course in a Husky, yes a Husky, with no seat pads in order to get my 6ft 7 frame in there and sat on metal for 4 days. Still great fun and frankly when thinking about the experience, it would have been cheating to use the CC as while the Husky was a very nice plane,( Husky owners just do not know what they are missing) I did learn more about how to fly the mountains and canyons since you really had to pay attention to density altitude , circle climb out of canyons ( CC would have gone straight out) and really manage the landings at gross for short rough strips. (Similar to our experience getting our seaplane rating,using the CC was cheating and learning energy managment in an unerpowered J3, is really better and more rewarding)
    We learned a whole new procedure for short field which involves no slipping ( I still like slipping but thought I would pass this onto the group and assume many on here may already knwo this technigue) First you load the plane to gross and write down all your indicated speeds with no flaps , 10 , 25 and 45, noting the difference between stall warning and actual buffeting. Strat flying the plane just above the buffet speed and in most planes you will now fly the aproaches with the stall warning on) Then using full flaps get used to fly stabilized approaches at the exact speed aproach speed every time. For example in the Husky that indicated aproach speed was 56mph at gross full flaps. You fly your approches at exactly that speed with some power and either increase or decrease desent rates with power only, never with ptich. EG "slow down to go down" which can easly get VERY steep and exceed 700-800fpm to get over trees or hill sides at the aproach . When you land, your kenetic energy goes into the runway vs horizonatlly down the runway with a slip or drag it in aproach. Immediatley one can shave 30% off your short field landings and it only gets better with practice.
    Now heres the fun part and a great plug for our planes. When I got home I ran the numbers on my CC and the indicated number for approach with full flaps is 21MPH. !!!!!!!! Now I know the airspeed indicator is not totally acurate due to some buffeting by the pitot tube or the angle of attack and my GPS in a no wind situation is indicating more like 30MPH , but needless to say those same landings in the CC vs the Husky were about 1/3 of the Husky immediately and coservativley, approaches were at least 26MPH slower, almost half the Husky speed.
    Just another good disciplined way to learn to land short and again I recommend such a course. They do not slip on these types of really short landings as most pilots will increase speed when slipping which will only lengthen landing distances. Regards Gary

    PS I still slip also on other types of landings because its fun

  10. #10
    Senior Member randylervold's Avatar
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    Default Re: Sideslip

    Interesting stuff Gary, makes sense.
    Randy Lervold

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