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Old 03-06-2007, 03:10 AM   #7  
Cubdriver
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Joined APC: May 2006
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Originally Posted by ImperialxRat View Post
And don't forget that if you have a crosswind, as you start recovering from the slip, you want to transition to your crosswind correction, so that you still maintain centerline and land appropriately (left main tire touchdown first, if a left crosswind, etc)
I think you meant transfer from a forward slip to a sideslip, but if you meant do a sideslip followed by a crab that would be out of order: crab down to very short approach, kick out your crosswind correction ("kickout the crab") then touchdown inline with the runway by using a tad of sideslip and dipping the upwind wing a little bit. Not too much or you will end up going that direction. You have to gauge the wind strength and apply equal aileron deflection (up) on that side. This will have the upwind wing a tad low due to less aileron on that side and the upwind main will touchdown before the other one. A lot of control sensitivity is required, but this is the only way to put down a tailwheel airplane due to stability issues. I would say sideslip is more of an optional thing in a tricycle airplane, but it shows good technique and proper use of the pedal thingies.

You can "kick out the crab" as early as you wish on final, but it takes more effort to maintain a sideslip and the latter are only useful on touchdown. Valid reasons not to sideslip in passenger aircraft are that passengers appreciate a level ride and low wing aircraft have limited clearance under the wing in many cases, so for them a sideslip on short final will scrape an engine, causing excitement and sometimes videos.

The above descriptions of crabbing, slipping, and forward slipping seem correct to me, but no one mentioned a real problem you can get into with poorly done forward slips that occurs when you enter at an excessive airspeed. To get yourself down in a hurry you tend to want to do a forward slip, ok but this can increase airspeed so much you end up defeating the purpose and landing long due to excess speed. The solution is not to start a forward slip until a sufficiently low airspeed is obtained. Counterintuitive as it may be is that there is an upper limit on the successful application of a forward slip. If you start a forward slip at greater than about 65 knots in a C172 and use lots of forward pitch you will pick up speed like crazy. But, if you actually slow the airplane down by pitching up a few seconds before starting the manuever, say 60 kts, you can then lose lots of altitude. The plane will drop like a rock and not pick up airspeed. I am not sure why this happens aerodynamically except that maybe the lower dynamic pressure allows fuller rudder deflection in proportion to the lift factor and the drag factor stays ahead of the increase in speed due to trade of altitude. One of my better instructors watched me fumble this a few times and informed me you need to start forward slips at a lower speed.

I have seen the placard about not slipping with flaps, but it wasn't in a late model 172. By late I mean coming after the november series. More info, anyone? I always use flaps when doing forward slips because it increases drag and increases the decent angle.

-Cub

Last edited by Cubdriver; 03-06-2007 at 08:07 AM.
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