Side-slipping
Joined: Aug 2001
Posts: 2,414
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From: Europe
J,
So if I read that back you say that the wing where the AOA at the tip is reduced due to the aileron being moved upwards will stall first. In this scenario the lower wing.
That is not my experience nor the way I understand the aerodynamics to work.
It is my understanding that on a conventional designed aircraft (with dihydral) due to the increased angle of attack (as a result of the relative wind over the wing and the downward aileron on this side) the high wing will stall first.
FD
So if I read that back you say that the wing where the AOA at the tip is reduced due to the aileron being moved upwards will stall first. In this scenario the lower wing.
That is not my experience nor the way I understand the aerodynamics to work.
It is my understanding that on a conventional designed aircraft (with dihydral) due to the increased angle of attack (as a result of the relative wind over the wing and the downward aileron on this side) the high wing will stall first.
FD
Joined: Dec 1999
Posts: 3,077
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From: Oop North, UK
"Dutch"
I think you have read JFs post wrong, in his example he has LEFT rudder and right aileron, ie. you would have the right wing down in a sideslip and you would roll LEFT ie towards the UPPER wing.
(correct me if i am wrong please John) as you say yourself.
Possibly oversimplifying it - rudder Left- spin left, rudder right - spin right. Not ALWAYS true, but for our purposes I would suggest true enough. (And ALWAYS CHECK the spin direction if unsure for recovery - assuming you have the height
)
I think you have read JFs post wrong, in his example he has LEFT rudder and right aileron, ie. you would have the right wing down in a sideslip and you would roll LEFT ie towards the UPPER wing.
(correct me if i am wrong please John) as you say yourself.
Possibly oversimplifying it - rudder Left- spin left, rudder right - spin right. Not ALWAYS true, but for our purposes I would suggest true enough. (And ALWAYS CHECK the spin direction if unsure for recovery - assuming you have the height
)
Joined: Aug 2001
Posts: 2,414
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From: Europe
F,
So keep the full rudder in left and pick the lower right wing up with the aileron?
That is indeed not how I read JF's post.
Is that how it was meant to read?
FD
he has LEFT rudder and right aileron, ie. you would have the right wing down in a sideslip and you would roll LEFT ie towards the UPPER wing.
That is indeed not how I read JF's post.
Is that how it was meant to read?
FD
Joined: Dec 1999
Posts: 3,077
Likes: 1
From: Oop North, UK
I don't know how you sideslip but I always seem to end up with TOP rudder so left rudder means right wing down - but maybe you do it differently
Johns post actually says
If you try this I think you will find the nose does not stop moving left UNTIL you have some right wing down (think about this-if you keep wings level and left rudder you will still turn left. If you are still banked left with left rudder then the nose will swing towards the ground)
Johns post actually says
use the ailerons to the right until the nose stops moving left round the horizon and the aircraft stops rolling left.
Joined: Aug 2001
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From: Europe
Agree with that.
Left rudder means right wing down if you want to slip.
But tell me what in your experience will happen if you manage to slow down so much that you stall in that situation. Which wing will drop? The right (lower wing) or the left (higher wing)
FD
Left rudder means right wing down if you want to slip.
But tell me what in your experience will happen if you manage to slow down so much that you stall in that situation. Which wing will drop? The right (lower wing) or the left (higher wing)
FD
Joined: Aug 2001
Posts: 2,414
Likes: 2
From: Europe
Nope,
He wrote:
FD
He wrote:
This means putting down the left aileron and the right one up.
This aileron action markedly increases the angle of attack of the left wing tip.
This aileron action also reduces the angle of attack of the right tip.
Please be very careful before believing that under these conditions the right wing will always stall first on all aircraft
This aileron action markedly increases the angle of attack of the left wing tip.
This aileron action also reduces the angle of attack of the right tip.
Please be very careful before believing that under these conditions the right wing will always stall first on all aircraft
Joined: Jul 2000
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From: Abingdon, Oxfordshire, U.K.
A year or two back, I was curious to see the effect of flying too slow in a sideslip so I tried it in the Skylark. She certainly did not do anything dramatic (she's a real Lady, mind), there was no 'flick into a spin' or anything like that. As I remember, it was just like approaching the stall but with more buffet and general airframe shaking. I think she tended to run out of control to the point where it was difficult to keep the slip on.
I suggest you all go out and try it, at a suitable height, of course.
I don't know if it has been mentioned earlier but sideslips don't work all that well if the speed is too high. Normal approach speed is about it. Any higher and you just won't get the sideways attitude.
Mike W
I suggest you all go out and try it, at a suitable height, of course.
I don't know if it has been mentioned earlier but sideslips don't work all that well if the speed is too high. Normal approach speed is about it. Any higher and you just won't get the sideways attitude.
Mike W
Joined: Feb 2002
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From: Enniskillen
I don't know where this is all going, perhaps there are too many of us telling each other how much we all know.
I would like to go back to "why does the average PPL in a light aircraft need to side slip"
I was taught sideslipping as a 17 year old SPPL in various aircraft as a way of loosing height in the least forward distance.
I still use side slipping for the same reason today (30 years later)
Example: PA28 (any model)
You are down wind at a height of 1000 ft, you expect to turn base and fly a 2 1/2 mile final, decending at about 500 fpm at 70 knots,
ATC request you "to keep it tight" and you turn on final at just under 1 mile, but are still at 800 feet, even with with full flap you are not sinking fast enough. If you put the nose down you will speed up and never get in.
This is where it is useful to side slip, to loose the excess height and still land at or near the start of the runway.
Done properly at the correct speed (ie.normal approach speed or slightly less) you will not damage the a/c nor will you spin or loose control in any other way.
Tony R
I would like to go back to "why does the average PPL in a light aircraft need to side slip"
I was taught sideslipping as a 17 year old SPPL in various aircraft as a way of loosing height in the least forward distance.
I still use side slipping for the same reason today (30 years later)
Example: PA28 (any model)
You are down wind at a height of 1000 ft, you expect to turn base and fly a 2 1/2 mile final, decending at about 500 fpm at 70 knots,
ATC request you "to keep it tight" and you turn on final at just under 1 mile, but are still at 800 feet, even with with full flap you are not sinking fast enough. If you put the nose down you will speed up and never get in.
This is where it is useful to side slip, to loose the excess height and still land at or near the start of the runway.
Done properly at the correct speed (ie.normal approach speed or slightly less) you will not damage the a/c nor will you spin or loose control in any other way.
Tony R
Joined: Dec 2001
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From: At work
I was shown sideslipping in a '152 at my last check ride, pretty impressive too, did it with full flap, went down like a brick, intresting noises too at 85kt! What used to worry me a bit is the side loads on the tail, but I'm sure they're well accounted for. I'll have to try it a bit more next I fly (don't know when
)
)
Joined: Sep 2003
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From: South Norfolk, England
SM
Not really. Slipping is not supposed to be a high speed manouver and it does indeed put some strain on the tailplane and sternpost. Besides which, what is the point of slipping at higher speeds? ... OK, I guess if you're in combat there might be a need 
JF
Thanks for that answer of yours! ... trust a test pilot to make it sound so complicated
I reckon I'd better shut up now as my brain is getting sore with all this thought on what to me is a dark science ... aerodynamics
SS
What used to worry me a bit is the side loads on the tail, but I'm sure they're well accounted for.
JF
Thanks for that answer of yours! ... trust a test pilot to make it sound so complicated
I reckon I'd better shut up now as my brain is getting sore with all this thought on what to me is a dark science ... aerodynamics SS
Last edited by shortstripper; 8th May 2004 at 07:33.
Joined: Apr 2002
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From: Who cares? ;-)
here again a quote from one of my many training books (I left out non essential sentences):
The Slip
The purpose of the "forward slip" is to dissipate altitude without causing airspeed to increase, e.g., airplanes without flaps. In planning the slip, take into cosideration wind direction. Slip into the wind.
Establish normal glide.
Establish slightly less than normal glide speed
Use of elevator: Control speed should be slightly less than normal glide speed.
Use of aileron: Principal control to maintain desired bank. Remember steepness of bank affects angle of descent.
Use of rudder: rudder is used in opposite direction of slip. Another use of the rudder is to keep the airplane from turning and to control the rate of turn.
Maintain original flight path
Note:
check manufacturer's recommendation for use of wing flaps extended during slips
recovery: allow enough altitude for safe recovery. Raise the low wing and release rudder pressure simultaneously to keep the airplane aligned with the runway. Assume normal glide before touchdown. Riase low wing with ailerons. Reduce rudder pressure.
That all coincides with the way I learned it.....
Westy
edited for spelling
The Slip
The purpose of the "forward slip" is to dissipate altitude without causing airspeed to increase, e.g., airplanes without flaps. In planning the slip, take into cosideration wind direction. Slip into the wind.
Establish normal glide.
Establish slightly less than normal glide speed
Use of elevator: Control speed should be slightly less than normal glide speed.
Use of aileron: Principal control to maintain desired bank. Remember steepness of bank affects angle of descent.
Use of rudder: rudder is used in opposite direction of slip. Another use of the rudder is to keep the airplane from turning and to control the rate of turn.
Maintain original flight path
Note:
check manufacturer's recommendation for use of wing flaps extended during slips
recovery: allow enough altitude for safe recovery. Raise the low wing and release rudder pressure simultaneously to keep the airplane aligned with the runway. Assume normal glide before touchdown. Riase low wing with ailerons. Reduce rudder pressure.
That all coincides with the way I learned it.....
Westy
edited for spelling
Last edited by WestWind1950; 8th May 2004 at 11:10.
Joined: Feb 2002
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From: Enniskillen
It is not a good idea to sideslip too fast in any aicraft, 85 knots is too fast in a 152. You could damage the aircraft
Anyway there is no point in slipping fast it defeats the purpose.
Tony
Anyway there is no point in slipping fast it defeats the purpose.
The purpose of the "forward slip" is to dissipae altitude without causing airspeed to increase,
Joined: Dec 2001
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From: At work
Thats what I thought, I must add that the instructor was showing a way of loosing as much height as possible in the event of the a/c being on fire preparing for a forced landing. I'd prefer to stick to slower speeds for slipping though.
Jet Blast Rat
Joined: Jan 2001
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From: Sarfend-on-Sea
Ah, I think we have the source, of misunderstanding, Mr Shortstripper. I was intending to convey the possibility of a spin in sideslip if the speed reduced and reached the (slightly increased) stall speed. I think you were reading it as an entry into spin as per the spinning exercise - at a high stall speed caused by pulling full elevator. In a sideslip if you keep the speed at normal approacjh speed or above, then you will keep flying. The danger is in an unreliable ASI and in allowing distraction and a low initial speed to bring the aircraft to the stall, hence my warning (remember I am telling people, not demonstrating this with me to keep a student out of trouble) to keep speed up. Wouldn't want to tempt any of our friends here into lethal situations 
