Side Slipping

[Julian]

Interesting article in this months pilot regards side slipping. Iwas shown this technique during my PPL and have sed it several times to expedite decents or drop through clouds. I have never tried a turning side slip though which sounds pretty interesting!

How many teach side slipping as a part of the PPL or during club checkouts?
Do any of you hate slipping?

[MJR]

Side slipping is not universally taught in the PPL syllabus as some aircraft are unsuitable for this technique in certain configurations. For example some aircraft with large flaps will actually mask the airflow over the elevator during a side slip. It is however a useful technique for losing height in the final stages of a forced landing.

cheers

MJR:)

[Mark 1]

Agree with MJR about using it on 152/172 with flaps.

I occasionally fly a C120 (no flaps) where its a valuable part of the repetoir.

I'm surprised by the comment about dropping through cloud in a slip as it would be extremely difficult to coordinate by sole reference to instruments - T&S and airspeed I guess but botth instruments liable to errors in that configuration.

I demonstrate it during the PFL lesson as one (of many) techniques to control ROD towards low key position, but only on final approach if flaps are inoperative.

[Julian]

I was taught it in a C152 but in a clean configuration, for the past 2 years though I have mainly flown an Archer III.

I think its definitely something worth demonstrating as part of PPL even if it isnt part of syllabus and I was probably lucky in the fact that the end of every lesson I had my instructor would have a quick 'playtime' where he would show you something not normally covered (I was also lucky enough to have the same instructor all through my PPL).

Mark 1, I have only used to drop through holes in clouds before I got my IR. As you say certain instruments are prone to erroneous indications and dont think I would like to try it blind! Final descent is another place although I have heard some guys I fly with say that their instructors on club checks have had a go at them for initiating a slip at this point.

[FlyingForFun]

I was taught the side-slip during my PPL, but not the turning side-slip. The first time I saw a turning side-slip was with an instructor in the States, in a Super Cub. He demonstrated one first - in the circuit, downwind, abeam the numbers, cut power and full flaps, full right rudder, and almost-full left aileron as necessary to turn onto final. It felt like we were falling out of the sky!

Next time round, it was my turn, and I was far more gentle with the controls than the instructor. "No, not like that, like this", and the instructor pushed in full right rudder for me, and held it there, until I had the courage to use the necessary amount of aileron!

After a couple of goes, there was a twin a couple of miles out on the instrument approach. I expected ATC to have us extend downwind behind the twin. The instructor got on the radio to report "Super Cub 41E downwind, request short approach" "Super Cub 41E, short approach approved, cleared to land, number 1." What????? But, sure enough, with the aid of my new-found technique, we were on the ground and clear of the runway well before the other traffic was over the threshold.

It turns out that ATC at that airfield are very familiar with the technique, and quite often offer it to the club's taildraggers (but, as far as I can tell, only to the tail-draggers, and only to those tail-draggers operated by the that club!) Over the two months or so that I was flying out of the airport, there were about 3 or 4 occassions where ATC asked me "are you able to do a short approach?" Of course I was! I love the technique! It's just a pity that most of the noise-abatement circuits around SE England are so huge that I can't practice it more often now I'm back home.

Of course, as with all new techniques, don't try it without an instructor who's familiar with the technique, or, if you have to, at sufficient height to recover if it goes wrong, and I make no guarantees about it working on other types.

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

PS - CFI & WWW - I'm sure this thread would be of interest to the Private Flying forum - any way we can copy it over there? Or should I just post a link to it?

[Tinstaafl]

I always used to teach them in all the a/c I flew. Straight, turning or whatever. A very handy technique to add to one's toolbox of skills.

[nonradio]

If you've not been taught slipping as a student, you've been short changed.It's a v. natural flying manoeuvre and it always seems odd that it's placed in the 'special' category. A certain flying school (in Oxfordshire!) frowned upon slipping in Pa28s due to possible fuel supply probs. Shame, because an ex school instructor (ingrained in the anti slip ways) then landed long during a forced landing (engine off) and wrote off the C152. He accepts that a timely slip would have helped.....
Didn't anyone read Biggles?

[weasil]

In the US slips to landing are actually REQUIRED to be demonstrated.

And as for those who say you can't teach slips in a C152/172... not true. Slips with the flaps down are fine in a C152 and are not recommended in a 172 with full flaps. So you put in 10 degrees, slip the plane down and then drop the rest of the flaps before the flare. It works great.

Weasil

[Charlie Foxtrot India]

It's required in the PPL syllabus here.
Students need to be taught how to do it properly, and know about the correct configuration; rather than giving it a try on their own after reading about it in their Trevor Thom!!
However IMHO it's more important to be able to do a correct approach without having to resort to sideslipping, which can get the unwary into trouble with a slow and out of balance configuration which could lead to a spin at low level.

[knobbygb]

I was taught to slip very early on in my training, probably due to one of our runways having extremley tight circuits due to villages and a MATZ and inexperienced studes always ending up too high. Did one on my own for the first time the other day (pa.28 - full flaps). It makes me a bit nervous as I'm still not quite sure of how to spot any symptoms if it's about to go wrong. I'm aware that I must only do it to the left (right rudder) so that the pitot tube isn't sheilded and that the ASI will still over-read. Any more tips?

My compulsion when doing PFL's is that, in the real situation I'd much rather be too high and have to slip than be too low and, well..... Never really get to practice this on a PFL due to not really wanting to lose that much height, but I think I'd always end up too high in the real situation and would want to have practiced slipping.

Interestingley, at my club, one particular instructor is very keen on the manouver, another is quite happy to use it, while others shy away from it when I ask, saying that I'll be taught more about it later in the course. I was always under the impression it was part of the JAA syllabus. Am I wrong?

[john_tullamarine]

I suspect that the pitot story might be one of those folkloric tales of aviation ....

Long time since I have been near the little Piper so I can't recall the pitot static configuration specifically. However, generally the system (on most, if not all, aircraft) is not overly sensitive to the pitot orientation compared to static port airflow problems. In general, any aircraft in a significant slipping attitude is going to have questionable pressure indications, for which the PEC charts are not applicable ...

[Chuck Ellsworth]

Do they not teash sideslips for x/wind landings?

Cat Driver:

[Field In Sight]

There was a thread recently about side slips/forward slips

http://www.pprune.org/forums/showthread.php?s=&threadid=46374&highlight=forward+slip+side

I flew recently with a PPL who had 140hrs and had never side slipped (i.e. for xwind landing). Unfortunately on that day there was a strong xwind and lets just say an interesting landing.

My strongest leg usually determines which way the aircraft slips :D

Ironically I was told that my PPL examiner would fail me if I used a forward slip on the PFL :confused:

[Pronto]

I learned to side slip while flying gliders. The bulk of training gliders (certainly the K13 I learned on) don't have flaps. They do have airbrakes or spoilers, which will steepen the descent. However, if you've got it badly wrong and really need to steepen your approach (remember, a go 'round isn't an option) then a hearty side slip is the answer!

I haven't ever had any problems side slipping a Warrior (-151 or -161), but usually have the fuel pump on by the time I come to do it (especially true on final!) Has anyone out there had a problem, (fuel or otherwise) or is this the aviation version of an urban myth?

I usually slip to the left but only because it gives me a far better view. It so happens that the pitot is on the left wing (for J-T, the pitot is at about mid-span, just inboard of the aileron, and towards the rear of the wing).

If anyone has had a genuine problem (personally, please - not rehashed bar talk) please let us all know. I'd rather learn from your problem rather than experience it myself...

Pronto

[john_tullamarine]

Thanks .. I am now briefed on the pitot ... and the static source ?

[knobbygb]

Static source is in the same head, with a back-up inside the cabin.

Pronto, I initially assumed the left slip was because of vilibility also. With the pressure head so far out on the wing, is a right slip really likely to be a problem?

[FormationFlyer]

Well I teach sideslips to students..think its ex8.3.4 from memory... :)

PA28s....problems in sideslip?! none. If you are *that* low on fuel that you have a problem during a sideslip then you shouldnt be airborne! I think my time spent sideslipping PA28s must be several hours worth now!!!

C152 - Interesting one this - I checked the approved FM of a Cessna 152 the other day and searched without success for the mention of 'no sideslips' or 'do not sideslip with flaps down'. Oh yes the 172 has restrictions but AFAIK the C152 does not and this is an extension of an urban myth 'you cant sidelsip a cessna'....One of the reasons for the sideslip limits on the 172 AFAIK were mainly structural but as one poster did say you can upset the airflow over the elevator....

Anyone got any further info on the Cessna 152?

[nonradio]

FF: you clearly don't fly for O£T$ (or they've changed SOPs)!Pa28s slip fine, as indeed do Boeing airliners viz the Gimlet(?) Glider!
A full flap max slip in a 152 is possible (we all knew that didn't we) but I once had a little pitch instability in the form of a gentle nodding... The manual for 1980 models doesn't have a reference to 'no sideslips', only to minimum flap required during x-wind landings; flaps are not permitted during intentional spins due to excess airspeed fears during recovery not because of 'blanking' as a previous contributor implied.
Field in Sight: If true, your examiner was odd.
Slipping left or right makes no difference in my experience though witha left side pitot a slip to the right can produce slightly more fluctuation in the IAS ( I'm guessing due to turbulence off the Propwash), but fly attitude and there's really no problem; in any case initial student slipping practice often produces a nose drop and increasing airspeed!
So can we all agree: a. slipping is a good thing, b. most of the training fleet slips nicely (yes I know Ercoupes can't) and c. it can be useful in x-wind landings as Chuck says?

[inbalance]

There are sideslips and sideslips,

I think it depends on the bankangle and the fuelsystem.
I´ve tried some sideslips on our clubs PA28 yesterday. With 10 gallons of fuel in each tank. slipping with full rudder stopped the engine after 30 seconds....
Aircraft like the Piper Cub or the Citabria habe a small headertank where both maintanks are connected to. This makes their fuel system less critical to sideslips

inbalance

[foxmoth]

B757 sideslips beautifully, only tried it empty though!:D :p :cool:

[cubbuster]

I guess I was lucky - my instructor(s) both PPL and post PPL have all encouraged the use of sideslips. So I use them. The PA28 sideslips well, but, you need to watch your airspeed.

I fly a J3 Cub on a regular basis and so get to practice a lot...;) :)

[Pronto]

J-T, Sorry, I've been away. Some Warriors have their static port in the rear fuselage, between the wing and stabilator (look for the shiny round metal plate!) There is (in every Warrior I've flown) an alternative static source in the cockpit. This is activated by turning a small metal "tap" which is under the front edge of the instrument panel, just above your left knee. The whereabouts of the alternate static is usually placarded.

For Knobbygb, no problems that I'm aware of in slipping right.

P

[john_tullamarine]

.. be aware, then, that IAS values are very dependent on PEC which is very, very dependent on flow variations in the vicinity of the static source, especially for keel mounted ports. Most of us are well aware of the small Cessna phenomenon of pulling the aircraft back well into a stall and then watching the IAS disappear off the clock. This doesn't indicate that the speed is zero, only that the instrument is telling porkies ....

The alternate static source in the cockpit is for emergency use in the event of water, ice or other contamination of the the external static source or the plumbing to that source.

[The 150 driver]

Gee Whiz Julian, I hope you ment dropping down through a "gap" in the clouds instead of "in the clouds". Try this if you don't have alot of room to move. Half flap, low power setting and a steep descending turn at about 10kts above the stall, or on the buffet if you have the feel. What you end with is a tight radius turn. Try it on nice day sometime, it's good fun.

Formation Flyer, I have seen it written in the P.O.H. of the C150 to avoid prolonged unco-ordinated due to the possibility of fuel starvation. As soon as I find it again, I'll let you know.
Cheers,The 150 Driver ;)

[CaptAirProx]

Dash Q400's sideslip ok. Even with full flap and pax on board! Hostie wondered what the hell was going on tho.

[Stunty]

Gday all...

I've done plenty of sidesliping...but can someone please explain a forward slip to me? Hows that work?

Stunty

[john_tullamarine]

US terminology to distinguish between an ordinary sideslip and the sort one does on final - still a garden variety sideslip .. do a search on the term .. there was a lengthy thread several months ago ...

[Chuck Ellsworth]

A foward slip is when you move your hand from the outside of her thigh and slip around to the front. :D :D

Cat Driver:

[Tinstaafl]

"Oops! My hand 'slipped'!" heh, Chuck? ;) :D :D

[Julian]

150 Driver - yep, have a look at my previous post, dont bother with gaps now as IR rated :D

[jrussell]

Gosh, everyone should learn how to do side slips. As a Cub pilot they are standard stock for the trade. Nice to see the expression on the face of a newbie when you throw it to the stops and come down like a ruptured duck. No flaps--no problem. :D

[bcpilot]

!! I can't believe that there are actually people out there who are afraid to do sideslips!!

As for the terminology issue, it's always been a Big pet peeve of mine. Here in Canada, we have one term for forward slip (to lose altitude) and another for sideslip (to line up with the runway in a crosswind) of course, they are the same maneuvre, but 4 out of 5 instructors I have recently spoken to don't realize this. In fact, most of them didn't even realize that while "side slipping" into a x-wind, they are increasing their R of D.

While we're on the topic, I need a good definition for slip, and a good explanation for the differences between skid and slip. I'm working on a ground school course, and so far, I haven't been satisfied with any explanations I've found on the net. Most of them are either complicated or just plain wrong!

I had one that defined a skid as too much bottom rudder where a slip uses top rudder. It works unless you use so much top rudder you begin turning toward the high wing, then you have a skid again.

I can easily define them in terms of relative airflow, but for the private pilot, i would rather use a definition that is more visual and hands on, (from a "how to" point of view)

Just curious to hear how some of you demonstrate these techniques.

[Flyin'Dutch']

Hi

I dont understand the difference between a side and a forward slip either.

A slip is a slip is a slip to my simple mind, although I did like the new definition of forward slip as suggested in an earlier post on this thread.

The direction in which you move is determined by the amount of slip you apply.

Max slip is determined by effectivity of rudder.

Max effectiveness of slip is determined by airspeed.

Worse thing that can happen when going to slow is that you do a falling leaf.

You wont spin.

Never flown anything as big as some here let alone slipped it, but when slipping you should fly the attitude and forget about the ASI.

In a glider a good slip gives a negative ASI! Yes as in less than 0 kts.

Have fun and practice with a competent instructor first. :eek:

FD

BC Pilot

Sorry only just read all of your post.

Skid and Slip.

Both are uncoordinated flight

Skid too much rudder (hence the stall and spin accidents when pilots are unkeen to use enough aileron and kick the bird round the corner stall, spin and kill themselves)

Slip not enough rudder to the extent that with an intentional slip to lose height you actually have the rudder opposite to the side of the turn.

HTH

FD

[bcpilot]

Not enough rudder and too much rudder, I kinda like that! I think I'll use it...

The terms top rudder and bottom rudder or inside rudder and outside rudder are relatively new to me. has anybody used them with students? just wondering what terminology students can get their heads around easiest.

One instructor was teaching skids and slips by describing the feeling of the tail "trying to pass you on the outside" in a slip and the tail "falling inside" on a slip. Interesting, i thought. Others refer to the ball, but i don't like that. A student should be looking at his attitude in a slip, not his t & b.

As for slipping a 172 with full flaps: totally safe! Only problem is that the oscillations freak out the passengers. I avoid doing full-rudder, full flaps slips, as the placard says. I don't have a good reason for avoiding it other than the fact that is feels like those oscillations can't be good for the aircraft. But as far as performance and safety go, there's no problem.

In fact, as a student the full flap full rudder slipping turn saved me a LOT of money by allowing those "abbreviated circuits". You know, alone in the pattern, turn x-wind at 300 feet, climb on downwind, cut power abeam the threshold and slip 'er in!! You can double the number of circuits per hour!! (oh oh, here come the floggings for the poor airmanship!)

[Flyin'Dutch']

BCPilot

You are correct in so far as that sideslipping a 172 with full flaps is safe...........but in the POH of some of the later models (dont know about the R and SP) sideslipping is not allowed.

Have been told that has to do with the elevator buffet.

FD :eek:

PS: Where is the top rudder on your aircraft? I have only ever found one on most aircraft and it is usuall on the thin end at the back :p

[Chuck Ellsworth]

bcpilot:

Why would your abbreviated circuits be " poor airmanship "

From my point of view the " abbreviated circuit " should be manditory for all pilot training.

Actually the circuit you described is quite large, you should cut it in half. :D

Cat Driver:

*****************
:D The hardest thing about flying is knowing when to say no.:D

[bcpilot]

abbreviated circuits would be poor airmanship in busy airspace. They are very good practice when things are quiet, though.

So you don't like the terms "top rudder" and "bottom rudder" when referring to a banked plane? Yeah, me either. I'll use that "too much" definition that you gave me. Thanx.

[pilotbear]

Forward Slip - where you are keeping the longitudinal axis of the aircraft in line with a fixed point, flying straight in relation to the ground.
i.e. point the nose at the runway with rudder and counteract the drift with opposite aileron. This is good for a cross wind approach as you can just land on the into wind wheel without having to straighten up. (in other words a standard wing down approach)

Side Slip - your target direction is out to the side of the windscreen. i.e. you are pointing (heading) at 30 degrees to your track, or flying sideways in relation to the ground.:D

hope this makes sense:D

[bcpilot]

PILOTBEAR: it's interesting that you define slips that way because the canadian definitions are opposite what you just posted.

In Canada, what you call the slip depends entirely on your relation with the runway.

In a forward slip, you are "on the localizer" and tracking to the runway, but your longitudinal axis is misaligned. Used to lose altitude.

In a side slip, you are also either tracking in line with the runway with one wing low (only possible in x-wind)

Here's where it gets funny:

We also call it a sideslip when your longitudinal axis is in line with the runway, but you are off the centerline, and tracking to the side to get on the centerline. In this case, your track on the ground is off at an angle, as in a forward slip. The only difference is that the purpose is to change the direction of flight instead of changing the rate of descent.

This is out of the Transport Canada Flight Training Manual (which I loathe)

These definitions are tedious, stupid, and meaningless, since the aerodynamics are identical in all cases if you take away the ground. My biggest problem is that many instructors i've spoken with don't realize this fact, and often, they don't even realize that in a side slip, your rate of descent increases. I would rather term them all simply "slips", and only differentiate when teaching the slipping turn, as it is aerodynamically different.

Of course, I'm in Canada, so I will have to mention the difference in the terms, but I will stress that is is the SAME maneuvre, the only difference is the purpose.

[pilotbear]

BCpilot - actually you are correct, I also have a Canadian CPL, I flew floatplane charters in BC last year.
I always think that the definition in the FTM is the wrong way round logically but it is right as you are slipping in a forward direction in a forward slip - Thanks

I just find it easier to think of it that way round, if I am looking out of the side of the aircraft I am going sideways, If I am looking over the nose I am going forward:rolleyes:

pilotbear

[Chuck Ellsworth]

Would it not be easier to teach new pilots to use the needed control imputs to align the airplane in the direction and attitude that is desired to fly the intended path?

Rather than all this mental mastrubation on how to describe the manouver how about this.

Here is a hint.

Picture this:

Our dedicated instructor is demonstrating a X/Wind landing.

The wing is lowered sufficient for the strong 90 degree X/Wind, however the longitudinal axis of the airplane is 30 degrees off the runway heading.

As the airplane firmly contacts the runway and wipes the gear off the student asks, was that a side slip? :D :D

Tha instructor answers, I am not sure, I will post on Pprune and ask. :D :D

Cat Driver:

[Tinstaafl]

No difference aerodynamically. The problem comes when trying to relate the manoeuvre to some ground reference.

Forward slip: Crossed controls are used in such a way that the flight path remains unchanged from the previously balanced flight path.

Example: (Nil wind for convenience) A slip is flown to maintain final. Previously the a/c was maintaining its flight path parallel to its longitudinal axis. A/c is yawed 'away' & rolled 'towards' the previous flight direction. The a/c maintains its original flight path but now with a new & different heading.

Sideslip: Crossed controls are used in such a way that the flight path deviates by some angle from the previously balanced flight path.

Example: (Nil wind to maintian commonality with the forward slip example) A slip is flown to impart a lateral component to the flight path eg to correct a displacement from final. The a/c is rolled 'away' & yawed 'towards' the original flight direction. The a/c maintians its previous heading. This results in a new & different flight path but with its original heading.

[bcpilot]

Mental masturbation is the perfect word for it:

I enjoy tossing around ideas and thoughts purely for my own pleasure and interest. PPrune is a good place for this because you can either choose to discuss these things with me or skip to a different forum.

Of course, as an instructor, I would like to approach these things from a "how to" perspective. "lower the wing into the wind and hold the plane straight with rudder" is about all the private pilot needs to know about slipping into the crosswind. "dip the left wing and stop the turn with rudder" is great for losing altitude.

"create an angle between the relative wind and the longitudinal axis of the aircraft by using aileron into the wind and opposite rudder, so that the path along the ground maintains a straight track in line with the centreline of the runway, bearing in mind there may be an increased rate of descent" would be the wrong thing to say while drifting off course on short final and into the control tower.

I just want to make sure I have ALL of the detail straight in my head so I don't teach anything wrong. i've overheard too many instructors teaching theory wrong (sideslips being a prime example), and i hope I never become one of those.

Thanks for the chuckle, anyway chuck.

btw. I'm not a flight instructor, just doing the rating now, and trying to develop a system that is good. If I sound like I'm talking out of my as s sometimes, it's because I am. everything i know now is from books and conversations. This is why I'm here: to get feedback from experienced instructors. Many instructors where i work don't seem to be as interested in discussing instructional techniques... more interested in talking about the airbus they hope to fly next year. Feel free to tell me what's what if i sound full of s***.

[John Farley]

In a forward slip, you are "on the localizer" and tracking to the runway, but your longitudinal axis is misaligned.

Is that really a published definition? Because don't those words also fit staying on the localiser in a cross wind where the mislaignment is merely your drift angle?

Cheers

[carb]

I quite a enjoy a good bit of side-slip; one of the best moments in my limited flying experience was a 'game-over' type botched PFL that ended up with me hurtling over a field in a full slip towards high trees with an astonished farmer looking round at my side-ways flying aircraft. Have also used side-slipping occassionally to expedite descent when necessary, having early on in my flying training been shown how to drop through a cloud layer using in a full slip, achieving more than 2500ft/min!

But, on a PA-28-151 checkout recently, in the US, the instructor intervened when I started side-slipping during the PFL, claiming it would put too much stress on the airframe (that particular one was 30 years old, with a few cracks right enough). Could there be some truth in that, or just a myth?

I also sometimes have this nightmare that when flying something with stiff heavy controls like a Warrier, I'll suddenly feel a 'snap' and the controls will be feel full and free like never before.

[bcpilot]

farley: No, not a published definition, just my understanding of a forward slip; and no, what you're describing is not a slip at all. in Canada, we call it a crab, when the relative wind is still in line with the plane, your track is in line with the runway, but your longitudinal axis is shifted into wind.

I think the Flight training manual basically emphasizes the difference is in the PURPOSE of the slip.
Lose altitude: forward slip
Change your track (or maintain a straight track in x-wind) without changing heading: side slip

[Lemoncake]

Ok, so I used to side-slip in a 152 when I was training. Now flying a 150, so would assume that slipping with full flap (40 degree) is a no no. Any thoughts?

[john_tullamarine]

The "forward slip" thing is a US term.

There was a lengthy discussion on it in this thread (http://www.pprune.org/forums/showthread.php?s=&threadid=60806&highlight=forward+slip) some time ago.

If you go to the FAA website and have a look at some of the documents there (I gave some references in the above thread) all will be revealed ... but I still can't see what the difference is between the "forward slip" and the good old garden variety sideslip ... other than the picture outside the cockpit. Does that mean I am a dinosaur tried and true ?

[nonradio]

To some,all very confusing this 'forward' and 'side' business from over the pond!

As I see it you'd be hard pressed not to be going sideways when slipping through the air - try it with the windows open, chaps, it gets windy on one side or the other! So the term 'forward' slip is bound to be a little inaccurate as you can't actually do without the sideways bit and still be slipping.

Presumably, the term 'forward' is trying to describe a slip where the flight path and ground track coincide with the extended centreline of your runway or airstrip (since all slips that aren't turning,by definition, have a constant direction over the ground ie track - wherever that may take you.. ).

Slipping turns are simply slips that have insufficient rudder applied to prevent the machine from changing heading.

Read your Biggles:D

PS shocking that anybody could confuse crabbing with slipping...

[John Farley]

bcpilot

Sorry old son that was not me describing a crab it was you.

I just quoted exactly what you said.

What you needed to include in your words to make them a description of a forward slip was a little bit about "with the wind down the runway"