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MikeInTx 03-05-2007 08:19 AM

Foward slips to landing
 
Hello everyone - I am 2 flights away from my PPL!

Foward slips to landings seems to be the last skill that is dogging me a bit.

I've been up w/2 different instructors and each explained it to me differently, and it seemed like when we actually slipped to land, THEY were the ones doing the flying.

Any tips, hints, pieces of advice, characteristics to look for/avoid would be very much appreciated.

Thanks everyone!

Mike

FL600 03-05-2007 08:36 AM

These are my FAVORITE!

I just remember, left aileron, right rudder....you should be lining up with the runway out your side window. There is a "v" in mine in the corner, and I use that as my visual to follow my track all the way down.

I straighten out right before roundout and flare.....

I was afraid of cross controlling with these when i first did them - just watch your a/s.

I would also go up and just practice a TON of short approaches with these!

Congrats on your upcoming checkride!

MHM

CubCAPTAIN 03-05-2007 10:04 PM

Quote:

Originally Posted by MikeInTx (Post 128621)
Hello everyone - I am 2 flights away from my PPL!

Foward slips to landings seems to be the last skill that is dogging me a bit.

I've been up w/2 different instructors and each explained it to me differently, and it seemed like when we actually slipped to land, THEY were the ones doing the flying.

Any tips, hints, pieces of advice, characteristics to look for/avoid would be very much appreciated.

Thanks everyone!

Mike


Make sure you are putting the wing down into the wind. Dipping your wing downwind results in a less effective slip and is not safe in a crosswind; when you transition from forward slip to side-slip, you want to have that wing already down into the wind.

A good simple way to break it down when you start out is:
1)The amount of rudder deflection in the forward slip controls the rate of descent (more rudder=greater sink) The second half of the rudder deflection usually has a lot more effect than the first half.
2)Aileron input controls drift from side to side (aka helps you keep it on the centerline)
This is obviously a simplified way to think about a forward slip, as the rudder and aileron do not operate independently in a slip (for example: if you are slipping left wing down and the airplane is drifting left, you can correct by reducing left aileron and adding right rudder), but its a good way to start to think about it.

Also, remember that most airspeed indicators are not accurate when the aircraft is in a forward slip. Keep the same pitch attitude in the slip as you had before starting it, and your airspeed should remain safe. A lot of people drop the nose considerably when slipping because they are trying to lose altitude. The increased airspeed will usually result in using as much runway as if you hadn;t slipped in the first place.

Hopefully that makes sense

ImperialxRat 03-05-2007 11:13 PM

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)

They really are a lot of fun.

de727ups 03-05-2007 11:55 PM

One other thing from looking at your avtar, Mike, is some Cessna's have a placard saying "avoid slips with flaps extended". I guess you could still practice them but understand the reason for he limitation and it's application for the checkride.

mistarose 03-05-2007 11:58 PM

When at a safe altitude line the nose up with a reference point, now bank the airplane in either direction but use just enough rudder to keep the nose of the aircraft pointing at the reference. Now slowly remove the aileron input towards the other direction while slowly removing rudder and applying opposite rudder as needed to do the same.

This will get you comfortable with the sideward forces and awkwardness of the forward slip. It may also improve your crosswind technique. I believe these are called "dutch rolls."

Cubdriver 03-06-2007 03:10 AM

Quote:

Originally Posted by ImperialxRat (Post 129073)
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

CubCAPTAIN 03-06-2007 05:48 AM

The "Avoid Slips with Flaps Extended" placard is there to prevent you from stalling the horizontal stab, resulting in an aggressive pitch-down close to the ground which obviously you don't want. However I have never felt this happen even with full flaps and a full rudder slip. Go up and try it at a couple thousand feet. I bet if you got slow it would. Has anyone else had it happen? The previous post about airspeed in a forward slip is right. If you start at to high speed, the airplane won't want to come down.

Also remember that the slip can be used for emergency altitude loss during a forced landing. Use is anywhere in the landing pattern if you are really high. On base, lower the wing towards the runway and hold it with opposite rudder. To turn final, just swap rudders. Once the turn is complete, put the opposite rudder back in.

When you are ready to take the forward slip out, all you have to do is relax the rudder you are holding until the nose is straight down the runway. I teach people to count to three while they slowly neutralize the rudder. This makes a nice smooth transition that won't make your passengers puke, if they haven;t already.:D

sigep_nm 03-06-2007 06:17 AM

Quote:

Originally Posted by CubCAPTAIN (Post 129103)
The "Avoid Slips with Flaps Extended" placard is there to prevent you from stalling the horizontal stab, resulting in an aggressive pitch-down close to the ground which obviously you don't want. However I have never felt this happen even with full flaps and a full rudder slip. Go up and try it at a couple thousand feet. I bet if you got slow it would. Has anyone else had it happen? The previous post about airspeed in a forward slip is right. If you start at to high speed, the airplane won't want to come down.

Also remember that the slip can be used for emergency altitude loss during a forced landing. Use is anywhere in the landing pattern if you are really high. On base, lower the wing towards the runway and hold it with opposite rudder. To turn final, just swap rudders. Once the turn is complete, put the opposite rudder back in.

When you are ready to take the forward slip out, all you have to do is relax the rudder you are holding until the nose is straight down the runway. I teach people to count to three while they slowly neutralize the rudder. This makes a nice smooth transition that won't make your passengers puke, if they haven;t already.:D

So you are recommeding to a new private pilot to go become a test pilot by disregarding a placard in the aircraft? I suppose he should maybe go spin an arrow too.

VTcharter 03-06-2007 06:48 AM

The do not slip with flaps placard normally indicates that you may not slip with FULL flaps, but does not limit slipping with partial flap extension. The reason is that the full flap extension, up to 40 degree on some 172's, can effectively blank out airflow over the tail in a slip and cause a tail stall, as earlier stated. Check the POH; I believe that the limitation was for full flap only, but this is from the dark corners of my mind, as it has been a while since I have flown a 172.


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