Too much law? May we discuss a flying technique?
 

Air law has been somewhat prominent in recent discussions here and, of course, it's an important subject, but may we talk about some aspect of aircraft handling that has not been done over recently? I suggest that we overshoot away from landings, but what about something like side-slipping? How many people are or are not taught how to do it? How many people regard it as part of their everyday skill set? If possible, can we avoid concentrating exclusively on the wisdom or unwisdom of slipping in C172s with the flaps down, although by all means go on about that if it gets your cookies. What else? Lowering flaps in the final turn? Fireproof shreddies? Cup holders?

Learnt forward and side slipping when flying gliders ... second nature now.

C172 ... I've slipped it OK with full flap but like you I don't really want to go there as the subject has been done to death!

SS

It was only when I expressly asked for some extra crosswind landing instruction, post PPL, that I was taught anything about side-slipping and some uses for it.

Since having that training, I'm convinced that confidence has improved more rapidly since it gives and extra technique for use in various circumstances. I.e. a backup on occasion.

In the light of this, I'd have thought s/s should form part of the PPL syllabus.

Ooh, side-slipping - Fun! Depending on the aircraft, of course.

I got my PPL on a PA28, and my instructor taught me to side-slip. Have never had any problems, and it can be a very useful technique.

Then I switched to a PA18, and one of my instructors taught my to side-slip properly (doesn't count unless you are using full rudder.... and preferably whilst turning in the opposite direction to that in which you've applied the rudder). Had a go at doing the same in a PA28 once, and it wasn't quite so comfortable as the PA18.

Then had a chance to fly a couple of aircraft like the Great Lakes, Pitts S2B and Tiger Moth where knowing how to side-slip is not just useful (and fun) but pretty much essential.

My Europa is not a nice aircraft to side-slip - it likes to pick up speed, and will very quickly go above Vfe with the flaps down unless you keep an eye on it. I try to practice regularly, but it's not something to do close to the ground unless you're in practice.

And finally there's the C172 - the ones I fly warn against side-slipping with full flaps in the POH, so I've never tried it.

The moral of the story? From my limited experience, it seems to depend very much on the type of aircraft you fly. Some can't do it, some can but only if you're careful or only up to a certain point. Others are brilliant at side-slipping. Definitely something that you should get someone to show you if you fly a suitable aircraft, though, IMHO.

FFF
------------

I've never sideslipped a 172 either.


But it strikes me that there are two possible reasons for such a prohibition. One is that it creates a handling problem, most likely longitudinal or directional instability (I saw both on a prototype once when sideslipping with full flaps, quite exciting). The other is that there is a combined rudder / aileron / flap (probably the last two) stress case which is considered hazardous to the airframe and therefore was prohibited.

Now if shortstripper has found no handling problem in sideslipping a 172....

G

I was taught to do it properly during taildragger difference training on an aircraft without flaps, so again it was pretty much essential. Until then it had not really been taught very well, i.e. I hadn't learned to do it. :)

I fly a Rallye 100 into 320 M of grass, over trees from one end. In zero wind I "MUST" side-slip to get down in order to leave a reasonable margin to stop.

It goes back to the thread on "real pilots", For some reason young instructors in the main don't teach side-slipping, many new PPLs don't know about it nor when to use it.

If you must come in "high" over trees etc, or you "end up" too high on approach, you want to loose as much height as possible while travelling the least forward distance.

Therefore if you are still high while flying at minimum approach speed then you must "make" the aircraft fly less efficiently to increase the rate of "sink", side-slipping is the safest way to do this.

The C172 with 40 degree flaps should not be sideslipped with "full" flap. This is not because the aircraft will fall apart, but because the vertical fin could stall due to the disturbed airflow over the fin and rudder at a slow speed. As you already may have input full aileron, the aircraft could roll unexpectedly and perhaps through 90 degrees before you are able to recover. (not something you would want to happen close to the ground).

To side-slip without full flap in a 172 with 40 degree flap, will not give you any advantage over just using full flap and keep the speed at min approach speed.

Go out and learn to fly cross controls, find a good old "cub" pilot to go with you.

Tony

Quote:

In the light of this, I'd have thought s/s should form part of the PPL syllabus.

It is. Part of Exercise 8.

R

PPL syllabus, by Tony R

20 hours in a can, 172 or PA28
5 hours in a Glider
5 hours in a Cub
2 hours Aeros ( Cap10 or something similar)
5 hours instrument (at least one ILS to 500 feet FOR REAL)
2 Hours in something fast and complex
1 flight in a multi engine
1 or more parachute jump to finish

After which you can go and learn to find your way around.

Tony

I was always told that you NEVER side-slip with flaps down... especially not full flaps. I can't find anything about it in all the flying books I own, but it seems sensible to me.

Westy

P.S. side-slipping a PA18 is sooo much fun!! :p

Why would that be then?

FD

Depends totaly on the aircraft - read the POH

Most aircraft are Ok to slip with full flap. and in most aircraft if you don't use full flap your side-slip will make little difference to your approach, so why bother.

Re the flaps and as per my ATPL course: When side-slipping, if flaps are deployed then the mean lift point moves in board towards the root. This reduces the stabilsing leverage and makes the aircraft unstable. Propeller wash has a similar effect. Apparently, low-wing aircraft are also generally unstable in the side-slip. High wing and swept wing aircraft are the most stable. If you draw a picture it is instantly possible to see the AoA differences and imagine how the airflows overthe fuselage and onto the wings. Intersting stuff.

However, I don't have the courage to try side-slipping for real without being taught. Where can I go in the Surrey/Hampshire area to learn how to do these kind of things?

I would suggest taking any type of light single you fly, take it high, preferably with an instructor or experienced safety pilot, and glide down, slipping it even as far as full rudder deflection in each direction. Note to avoid spinning and killing yourself - KEEP THE SPEED UP, and treat the ASI with caution (it may under-read).

Tried this recently with a high-hour "student" (was retraining from lots of experience stateside - I learnt there under a very good instructor, why can't they all teach what he taught me? Why is there so much bad training of Europeans out there, when much of the FAA training is quite good?) who really had never been shown the sideslip. Very useful exercise, especially in a Robin 200 (tiny flaps, maximum 20 degrees).

High-wing - if you can get to the other side of Hampshire I'd be delighted to show you.

TonyR

I could show you what can be done by way of angle of descent with sideslip but little flap.

I've never asked Mr Cessna why side slipping with full flaps on the 172s I've flown is prohibited, but it certainly is not allowed in the POH.

There is a view amongst some jocks with much more experience than me that the 172 can stall with a very big wing drop and enter into a spin when slipping with full flaps if the airspeed is allowed to decay , but as I say, I've always followed the rules.

Having slipped PA28s extensively, its a great way to lose height rapidly and anyone who hasn't learned it would do well to spend some time with an instructor - the best thing is as soon as you remove the cross controls, the aircraft flies completely normally again, not pitch up or down as experienced when latering the flap settings in some aircraft.

That's interesting, as I was taught side slipping at the same place that DJRAD wasn't. It was shown to me in more than one lesson, infact I remember coming in a bit high on a dual circuit once or twice during lessons, so sideways we went :)

I also remember one of the comments which was said in jest, "OOOoooooo flash ba5tard"

The thing that I should practice more is getting out of it without coming off the centre line of the runway, as I tend to find that I always let off either more foot than stick and go all over the place.

Something like that anyway.

HWD. You know where you can come to in surrey to be tought!

As for the cessna slip with full flap:-

1 )Think about the relative airflow in that condition

2) Think about what will happen to the airflow that passes over (and under) the wing (Into the slip)

3) Think about which control surfaces will be masked by aforementioned wing & flap

4) You have your answer!

Send Clowns. The ASI may Under or Over read depending on the direction of slip (Assuming only one static vent).

As mentioned by a pevious poster. The sideslip is part of the JAA syllabus (as it always was with the CAA syllabus).

May I ask what is the purpose of side slipping, in the context of PPL training?

I know the ald argument about crab v. sideways landings, but apart from that.

I'd read about side slipping and already crabbed and attempted wing down landings (they just dont feel natural!)

I was doing an approach and my instructor said (quite rightly) you're obviously too high here, so do something about it.

A bootful of left rudder and a twist of the yoke adjusted the vertical hold nicely (2 reds 2 whites). Controls to centre brought us back onto a normal descent. I think it took my instructor by surprise.

Pity I forgot to do it at Gloucestershire on my QXC as I sailed over the runway at about 500ft with full flap, throttle off and me bashing the dash with a kneepad shouting 'Down Boy !! Land dammit'. After go around I stopped short of the gravel trap (marked satisfactory) .

Must try it on a PA 28 next time I'm looking down at the threshold from on high.

I reckon it's better than just winding on the flap and wishing you had spoilers.

Send Clowns,

Thanks! You're in Bournmouth right? I would like to get out and about to meet fellow Pruners anyway so you better be careful as I might take you up on that :ok:

SilverFox,

True, true. Thing is until this thread I never actually considered that one of your chaps could show me this stuff in a 152, with flaps the size of a small Pacific atol it hardly needs it. Thought it was the stuff of Cubs, Austers and Tigers (don't ask why) :) Wonder if the ol' AA5 is any good at this stuff :D

Well welll! Mr Clowns here in the private forum. Well, I bid good day to you sir despite some previous skirmishes elsewhere. :ok:

I've been mucking around with some sideslips, but not in the usual sense. Basically messrs. Cassidy* has advised in his great book that the right way to enter a comp. turn is to rotate longitudanly(?) then put the turn in, i.e. roll (no yaw please) then bank.

Can I just say this is an arse to do in a low powered mount. I can get the Robin over to, maybe, 30 degrees with full opposite boot before it's going to turn whether you like it or not.

Is the 'correct' comp technique assuming Pitts or better or am I doing something wrong? Stik? Anyone?

* Much respect.

Send Clowns,

You stated you could teach me "what can be done by way of angle of descent with sideslip but little flap".

Also you stated "KEEP THE SPEED UP"

I fly into very short strips every week and the reason I sideslip is to "decend steeply over the shortest distance"

I must fly the aircraft at the minimum approach speed to achieve this, and the minimum speed is achived with full flap on most a/c with few exceptions.

I have 53 aircraft type logged and most fly the same.

HWD, you state "Apparently, low-wing aircraft are also generally unstable in the side-slip"

This is just NOT TRUE

Tony

TonyR,

My mistake, I should have written low wing configurations are more unstable rather than low wing aircraft. As aircraft designers, one would assume, have sought to combat that!

According to my notes:

For low wing aircraft, the principle being that the airflow over the fuselage generates an upflow of air over the lee wing (outside wing) increasing the lift of that wing and hence increasing the angle of bank (which is the definition of unstable) rather than decreasing it (the definition of stable).

However, dihedral directly combats this effect by reducing the angle of attack of the lee wing. Swept wings provide a stabilising influence too, to do with amount of wing directly presented to the airflow.

Apologies for my rather anal contribution to this thread but I like these discussions because they add a dimension of realism to my studies.

Just before anyone gets in the club a/c and goes sideslipping, this should not be practiced on your own at low level, but it is a good way to get to know more about your a/c.

Many of you are already doing it when crosswind landing!

Your last post was well pointed out there TonyR. With full flaps some of the club a/c do have a tendency to bite. They side slip beautifully.......to a point. Unfortunately that point suddenly appears and at the kind of heights we are talking about on final, there is rarely enough time, height or power to do much about it.

I spent several years flying the 172 and only the 172. I side slipped a lot especially in situations where there was a quick loss of height required late on. An example would be the northerly runway at Popham where the trees can keep you quite high above the threshld especially on a war an dcalm day where you can anticipate plenty of float.

I did once go up to 4000 ft and try out some side slipping with 30 degrees and then 40 degrees of flap. The stall was reasonably predictable with 30 degrees, with 40 degrees it was a killer. The trouble with practicing at this height is that you do not get the visual effect of the onset of the stall and the sudden height loss. Only the VSI tells you what is happening in terms of "falling" and at this point, you are working to get it straight and level again, not glancing at instruments.

I now have a flapless Luscombe and have learned a lot more about side slipping. My view is that the final approach on flapless a/c does tend to be slightly flatter than the approach associated with an a/c with flaps. Speed control is paramount to avoid floating down the runway and tiny side slip inputs are invaluable to maintain the correct speed over the threshold. I feel that too many people see sideslipping as a "quick way to lose unwanted height". They boot rudder and opposite stick, lose 150 feet and then continue a normal approach after they have settled the a/c.

Sideslipping can be used all the way down if required. We all know that descent must be controlled by power and speed by pitch. There comes a point in the descent where your 6th sense tells you that these inputs alone will not bring you neatly over the threshold.

At this point I tend to gently ease in a sideslip (always right rudder and left stick for obvious visibility reasons) and then hold it for a second. The sideslip seems to need a second or two to develop and there is much skill in balancing both inputs to avoid "overyaw" or "wingdrop". If the input is not sufficient, the pressures can be increased gently until the correct descent rate is felt.

I often find the nose can lift involuntarily during the sideslip but the ASI still reads a healthy number. This is where I am always extra cautious, especially when stopping the slip. If the nose isn't lowered when the control inputs are cancelled this can leave the a/c perilously close to the stall especially when it is slightly "wallowing" after the sideslip has been cancelled and it is re-balancing itself.

I do hope this hasn't all seemed like a load of drivel. I wouldn't be writing all this if the sun was shining and I could be flying!

Hoping to get to Popham later if the cloud lifts, the wind is slightly from the North. Time for some side slipping over those trees !:ok:

Side slipping is fun, its great to see how fast you can come down :D Its good fun going out and experimenting with what your aircraft is capable of.

Another important thing to prcatice, which probably isn't practiced enough is slow flight, for example flying a 172 straight and level at 50kts or less. My standard of flying improved dramatically when I did the CPL, before this I would have classed myself as an average pilot, who could fly, but not particularly beautifully. During my training, me and my very good instructor used to do a lot of "exploring the envelope", very slow flight, accellerated stalls, cross controlled stalls, all sorts of stuff. We used to push it, he used to tell me to "go for it, if we spin, we'll recover".

As a PPL I had picked up loads of terrible habits, like looking at the instruments too much during stalling exercises "to keep the ball centered", so a lot of my training involved covering up all of the instruments (except oil guages) and flying by "the seat of the pants". Bloody excellent, it taught me a hell of a lot, especially when flying as slow as possible, with no reference to the ASI, but just "feeling" the aircraft, or stalling while watching the wing tip.

Good fun.
EA:D

I echo Monocock's sentiments. Get used to a Luscombe and your skills will improve. Sideslipping down from the trees on 03 at Popham is a very useful skill and very good with a crosswind as it straightens everything out for you.

So everything suddenly went quiet and the only tenable field is short and awkward with a crosswind and obstacles on the approach. Being confident with this skill could be a lifesaver.

Apart from helping you with sideslipping the Luscombe will also improve your approaches by making you nail the right speed.

Sideslipped a 172 all the way down to the runway last year on my BFR in the US last year after the instructor gave me a PFL with flap failure. It was very well behaved but my right leg muscles were getting tired. I imagine the prohibition in slipping them with full flap is because the turbulent airflow off the trailing barn door is running spanwise and screwing up the effectiveness of that aileron.

Mike

TonyR,
Now I'm confused. Please explain.

Mike,
I was taught to do tight S turns to get into a field without flap. I have used this techique when, on a couple of I occasions, I was too after getting a straight in approach (sometimes hard to judge without the preceeding circuit).

I've been checking some of my flight training books about doing forward slips and flaps. Here's what Kerschner's Flight Instructor's Manual says:

He goes on to explain how to do it and, as I also learned, tells that you apply aileron first and then the rudder.

Interesting how the views about it varies.

Glider plane training comes in handy when learning to slip :p

Westy

P.S. I'll continue checking my other books..... ;)

That is interesting...

I suppose I have always entered the rudder input first to enable me to look ahead better before pushing the stick over.

I shall try your method later on Westy.

If this is the last post you ever read from me, you'll know that it wasn't very successful

:ouch: :ooh:

Lots of interesting stuff but some rather off the ball answers!

Send Clowns ... I'm sure your "keep the speed up" bit was simply to try and add a safety margin, but it's really misplaced over-cautiousness. It's actually very difficult to spin from a side or forward slip. Two main reasons, but don't take this a wholly true as there may well be exceptions! ... Most aircraft will tend to run out of rudder authority before you reach stall and will naturally start to turn back into trim. You will by then of course be VERY near stalling so it won't take much to tip the balence but you'd be a fool to miss the signs. Also, unlike skidding manouvers, you are in a pretty safe configuration as the inner wing (relative to airflow) has a better "bite" of the airflow unlike outer wing which would cause that wing to stall first. As the slightest easing of rudder pressure will swing the outer wing back into relative airflow faster than the inner wing it will very quickly take hold again. I'm probably not very good at explaining this, so go up to height and try it. I was taught to completely ignor ASI when slipping but this was basically because a glider has a pot pitot which is VERY inaccurate in the slip. The habit stuck though and I find it's easier to go by attitude and feel. To slip effectively though, you will tend to find you need a slightly higher nose up attitude than when you fly "in flow" to keep the same airspeed. It can seem a bit scary until you get used to it but there's no point in letting the nose drop in a slip because you will loose all that short landing advantage by the ensuing float.

I note of caution ... some homebuilds and I guess some factory types don't have the strongest of sternposts. Slipping is OK at slow speed, but not at all appropriate at too high a speed as stressing will be high!

C172 slipped very well. I was with an instructor at the time and he was under the impression that what he called a myth was to do with elevator blanking. I hadn't read the POH and I guess if I had I may have not been so enthusiastic. However, it slipped beautifully, came down very quickly, which in itself is dodgy as all that downward momentum takes some checking! To be honest with those very powerful barn door flaps, the one aeroplane you really don't need to slip IS a 172 :\

SS

IO 540 asked:

May I ask what is the purpose of side slipping, in the context of PPL training?

I guess that in simple terms it is another very potent weapon in one's flying arsenal.

For finessing landings it is absolutely essential - I am not talking about bringing a PA31 with eight friends in the back into 6 000' of billiard table smooth tarmac, where throttle and flaps can effect the same seamless transition from aircraft to ground vehicle.

What I mean is judging your touchdown point very accurately in an aircraft with no flaps or with u/s flaps.

When will this be useful?

Well several scenarios spring to mind;

1 forced flapless landing into a confined space
2 landing into a short strip
3 landing something hot and fast (sports biplanes?)
4 3 pt landing something with very poor forward vision (C195)
5 wishing to land and avoid hay bales and cowpats on a farm strip!

Of the two aircraft that I own, if I was not competent at side-slipping then I'd never get them down!

Paulo - the comp turn is a low K factor, however if you do exactly what Uncle (aka The Master) says in his book you will generally score quite high. Having never flown a Robin I can not really comment on technique but are you sure that you are not being too energetic with your feet?


Stik

Side-slipping
 

Its been enlightening (as always) reading everyone's responses on side-slipping (good thread FNG).

7 hrs into my tailwheel conversion, apart from being a much poorer tailwheel student than I hoped to be (!), its been interesting to learn how poor my side-slipping skills are. I also find it slightly intimidating to do it on finals when relatively close to the ground.

I'm sure all this will sort itself out with practice, but its certainly proving to be an interesting learning experience!

Stik - who's the Uncle?

ChiSau, (cantonese for toilet!)

Uncle is an old nickname of Alan Cassidy, multi times winner of the BAeA Unlimited Championship, after his last victory in 03, it was suggested by the competition director that he be referred to as The Master, an appelation reserved for Neil Williams!

Cassidy's book was mentioned in Paulo's post on p2.

Stik

IO540

Or even forces flaps down landing into an adeqate length field.
How do you do your engine out landings without the extra tool of side slipping to adjust your touch down point?

HWD

I was talking about flying using "cross controls" during a crosswind landing, most people do it naturally.

Using s turns can mess up your approach, sideslipping keeps you on a constant visual picture during final.

If PPls were also taught how to fly at minimum drag speed, with power, then most approaches would not need side slipping.

Why do most people fly their final approach 20 knots faster than necessary?

Don't worry, I suspect most of us find that! I did :O

This is all good stuff, and no one has asked if it's legal, which makes it even better. Bit disappointed that we didn't get on to cup holders, but you can't have everything. Mmmmmmmm, side-slipping...yesss. Could be a life-saver, I reckon, if trying to force land, with or without flaps. When I last did a PFL in a Bulldog, I ended up rather too high on final (those who have flown the lead-lined sack of heavy things that this aircraft becomes without power may share my surprise at this), but a bit of side slipping sorted that out.

If you fly as badly as me then you would be an expert at sidesliping too! You know, too high, too fast! Whooooa get this beast down:uhoh: A good sideslip on shot final makes it even seem like I know what I'm doing.:mad: :ok: :E