Side-slipping in light aircraft
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Side-slipping in light aircraft
Can anyone give me some advice about sideslipping to lose height in the approach? Some instructors I've had are dead against it, some encourage it - in the same aircraft mind. I can't find anything in the flight manuals to prohibit it, although I seem to recall something from the Cessna manual saying it was 'not recommended with use of flap.'
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Read your POH. If the POH doesn't prohibit it, go ahead and try it with your instructor. Then keep it in your bag of tricks for the few times when it comes in handy. It was the only way to land some of the vintage aircraft like Tiger Moths that didn't have flaps, but these days is rarely used, particularly on approach when it requires a little more attention. But there will be a time when you'll pull it out and it is a good technique to know.
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POH is the way to go, but also even if allowed for the type aircraft, keep in mind how much fuel is in your tanks, fuel selectors, etc. One consideration is getting air into the fuel lines downstream of the tanks, hence possible engine cough.
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You mentioned Cessna. If you're talking 150 or 172 I've done it many, many times with no problems and it works great for losing a lot of altitude quickly. On my checkride it was one of the maneuvers the examiner asked me to perform. Unless you've practiced it PLEASE don't do it solo until you've done it with a CFI with you.
Slipping the 172
My instruction here in the States has it as a mandatory to learn.
Its a brilliant way to quickly adjust your height in a controlled manner, it also gives you respect for the somewhat counter-intuitive opposite use of rudder and aileron. The key is maintaining your final approach speed and not allowing it to pick up at all, or at the very worst 5kts.
And yeah - have an instructor with you the first time you do it, because your natural instinct is to NOT let the aeroplane do these kinds of things.
Disclaimer: all I have just said may be totally bogus, as I am only 40hrs worth of a pilot.
Yeah ... right!
Woomera
Its a brilliant way to quickly adjust your height in a controlled manner, it also gives you respect for the somewhat counter-intuitive opposite use of rudder and aileron. The key is maintaining your final approach speed and not allowing it to pick up at all, or at the very worst 5kts.
And yeah - have an instructor with you the first time you do it, because your natural instinct is to NOT let the aeroplane do these kinds of things.
Disclaimer: all I have just said may be totally bogus, as I am only 40hrs worth of a pilot.
Yeah ... right!
Woomera
Last edited by Woomera; 25th Aug 2005 at 05:48.
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Some thoughts -
(a) the flight manual is part of the POH. If the OEM recommends against or prohibits the technique, then there is probably a good reason for that recommendation or prohibition.
(b) there are a number of possible concerns, principally
(i) airflow doing strange things either (typically) in a high wing or with the tailplane .. keep in mind that, if strange things occur at the tail, one could be faced with a significant nose down pitching moment just when one might not want that to occur.
(ii) fuel system problems .. uncovering tank openings in a low fuel state for instance.
However, on those aircraft which don't have any undue vices in an approach sideslip, the technique works a treat for major profile control .. albeit that passengers might not like the sensation.
(a) the flight manual is part of the POH. If the OEM recommends against or prohibits the technique, then there is probably a good reason for that recommendation or prohibition.
(b) there are a number of possible concerns, principally
(i) airflow doing strange things either (typically) in a high wing or with the tailplane .. keep in mind that, if strange things occur at the tail, one could be faced with a significant nose down pitching moment just when one might not want that to occur.
(ii) fuel system problems .. uncovering tank openings in a low fuel state for instance.
However, on those aircraft which don't have any undue vices in an approach sideslip, the technique works a treat for major profile control .. albeit that passengers might not like the sensation.
every landing you do in a X-wind requires a degree of slip. it is not rocket science. do not be afraid to use it. there is a nose down moment when cessna 100 series are slipped with full flap, in my experience, but not too bad. learn to use slips to your advantage, as said before, they are a good thing to have in your bag of tricks. skids are the thing to avoid at all costs at low level.
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Don't have a Citabria POH with me now .... but I think it recommends against slipping with full flap. No idea about Cessnas.
As some have said it's a great way to lose height if needed on approach. But it isn't something to go out and try yourself. Get some instruction and take it from there. Don't get talked out of doing it by inadequate instructors. If the aircraft can do it SO SHOULD YOU!
Once you've got slipping on approach sorted out, another challenge is to slip through a 180 degree turn with the aim of being at a certain planned position at the end of the turn. Practice left and right.
Good luck
As some have said it's a great way to lose height if needed on approach. But it isn't something to go out and try yourself. Get some instruction and take it from there. Don't get talked out of doing it by inadequate instructors. If the aircraft can do it SO SHOULD YOU!
Once you've got slipping on approach sorted out, another challenge is to slip through a 180 degree turn with the aim of being at a certain planned position at the end of the turn. Practice left and right.
Good luck
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You are not meant to side slip a 172 with flap down because it apparently blankets the elevator, and it (the elevator) could stall. So I am told.
I slip 172s all the time however and as long as you check forward its not a problem. You just have to make sure you don't get too fast, otherwise an overshoot may occur.
If your going to slip a 172 with the flap up, make sure you side slip it to below profile then there will be plently of opportunity to slow it up again.
Always intersting to watch a pitts special land - side slipping nearly all the way to the ground.
I slip 172s all the time however and as long as you check forward its not a problem. You just have to make sure you don't get too fast, otherwise an overshoot may occur.
If your going to slip a 172 with the flap up, make sure you side slip it to below profile then there will be plently of opportunity to slow it up again.
Always intersting to watch a pitts special land - side slipping nearly all the way to the ground.
Ah, Oz remembers trying to tell his hands and feet to do what the nice instructor wanted. Oz remembers confusion on changing from crab to wing down into wind on x/wind training. Oz has brainwave! Oz will set up wing down into wind early to make it easy for feeble brain to tell hands and feet do the thing that nice instructor wanted......Oz learns valuable lesson about "side slip" too close to ground. Oz now knows correct methods for x/wind landings.
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You can slip the citabria with full flap, just not as aggressive as if you had only 1/2 notches, They're quite small flaps and the only issue is really damaging the guide rails or indeed the fabric flaps themselves, which in a forced landing is not relevant, so in that event slip the buggery out of her to get in.
I prefer to fly tight circuits and certainly a good 80% of my landings contain slips of some sort, even in a 182, I just can't feel comfortable with those flat 3 deg approaches. - maybe I need more practice in the circuit
I think as a general rule, if you are in a slip the same side as the pitot then the airspeed will slightly over read, if you are slipping away from the pitot wing (relative to the airflow), then the airspeed will slightly under read, so typically I add 5 or so kts to the approach speed, so I can get quite sharp at 65/70kts (based on looking for a final over the fence of 60kts - this margin also covers you for under-read/overread if you get confussed and bewildered). - or is it the other way around ?
If you allow the speed to decay in the slip and if you have full flaps and you are heavy, then your downward momentum cannot be arrested and you'll bleed all the speed trying to level out, so I'm been advised by people far far more experienced than I to ease out of the slip by 100 agl, and be balanced and sorted by 50(ish).
anyone notice the little "push" of airspeed after coming out of a slip ? apparently It has to do with the workload of the "fast" wing outweighing the deficit of the upper-slip wing and that energy is converted to speed (kinetic), so you get a little increase (which can be fun) in speed if you are not expecting it.
I love slips! They are fun and they give you confidence in case of a forced landing - which we'd be foolish not to consider
I prefer to fly tight circuits and certainly a good 80% of my landings contain slips of some sort, even in a 182, I just can't feel comfortable with those flat 3 deg approaches. - maybe I need more practice in the circuit
I think as a general rule, if you are in a slip the same side as the pitot then the airspeed will slightly over read, if you are slipping away from the pitot wing (relative to the airflow), then the airspeed will slightly under read, so typically I add 5 or so kts to the approach speed, so I can get quite sharp at 65/70kts (based on looking for a final over the fence of 60kts - this margin also covers you for under-read/overread if you get confussed and bewildered). - or is it the other way around ?
If you allow the speed to decay in the slip and if you have full flaps and you are heavy, then your downward momentum cannot be arrested and you'll bleed all the speed trying to level out, so I'm been advised by people far far more experienced than I to ease out of the slip by 100 agl, and be balanced and sorted by 50(ish).
anyone notice the little "push" of airspeed after coming out of a slip ? apparently It has to do with the workload of the "fast" wing outweighing the deficit of the upper-slip wing and that energy is converted to speed (kinetic), so you get a little increase (which can be fun) in speed if you are not expecting it.
I love slips! They are fun and they give you confidence in case of a forced landing - which we'd be foolish not to consider
Last edited by 7gcbc; 25th Aug 2005 at 11:47.
Unless your a/c has a balanced pair of static ports then I suspect airspeed indications are most likely to be affected by the changed pressure around the single static port.
Apart from that I'd expect a pitot system to under read due the misaligned airstream. Would it be any worse than any misalignment caused by pitching manouevres? Who knows?
Apart from that I'd expect a pitot system to under read due the misaligned airstream. Would it be any worse than any misalignment caused by pitching manouevres? Who knows?
Last edited by Tinstaafl; 25th Aug 2005 at 18:00.
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Really its a matter of why would need to sideslip a flapped plane? They dont handle nice anyway all crossed up.
In a Pitts I used to cross the controls up ever so slightly so as to sight down the left of the fuse on approach. The Pitts being a bag of squirrels near the ground I dont think I d want to side slip one and cock it up
Just my two bobs worth I think a lot of you young fellas are getting mixed about a time that went out with button up boots and biplanes.
In a Pitts I used to cross the controls up ever so slightly so as to sight down the left of the fuse on approach. The Pitts being a bag of squirrels near the ground I dont think I d want to side slip one and cock it up
Just my two bobs worth I think a lot of you young fellas are getting mixed about a time that went out with button up boots and biplanes.
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Really its a matter of why would need to sideslip a flapped plane?
Even in a Pitts a sideslip is not really necessary. I used to just do a curved approach, that kept the runway visible till the flair. The only times I'd slip is if I had to extend downwind for some reason, had botched the approach, or wanted to demonstrate one to a passenger.
The times that a slip is very useful is if you've had an engine failure. You can aim for the middle of the runway or field, and then use a very controlled slip to move your aim point to your desired position.
The times that a slip is very useful is if you've had an engine failure. You can aim for the middle of the runway or field, and then use a very controlled slip to move your aim point to your desired position.
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quote:
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Really its a matter of why would need to sideslip a flapped plane?
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perhaps because its just possibly a little more fun than a drag-em-in 3 deg approach placing all your faith in the donkey ?
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Really its a matter of why would need to sideslip a flapped plane?
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perhaps because its just possibly a little more fun than a drag-em-in 3 deg approach placing all your faith in the donkey ?