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Phil Perry

Sideslipping again. . .

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WHY OH WHY is is that some Flying instructors seem averse to teaching this useful tool, which should always be towards the top of the stuff in the toolbox of Most three axis pilots ? 

 

I was flying ( by personal invitation ) today with a friend who purchased a Evektor 'Eurostar'  ( Sport Star lookalike )  He gave up three approaches and went around three times. . .on a Runway which could comfortably accommodate a B-737 or similar Jet RPT.      I had taken this friend to the Isle of Man TT races in a borrowed Piper Arrow on Three occasions, some years ago. . .and allowed him to 'Play' with flying ( At a safe altitude ) ) it which sparked his interest in our rather esoteric hobby. . .( ? )

 

(He had bought the Eurostar, along with his Brother, who was still in basic training )  We flew to an airfield that he had never been to during his training,   The enormous runways seemed to Phase him a little, and he seemed to lose all scale and appreciation of circuit height versus what height you need to be to pull off a half decent approach and touchdown. ( ? ) 

 

He had been instructed at a very small airfield in the North of England  ( Not Ours ) where the circuit height was 600 feet. . .he had difficulty organising a 1,000 ft circuit and the Flight Service guys were getting a little pi$$ed off and tetchy with his missed approaches, on a Busy day. .. ( Yes, I KNOW they shouldn't do this )   I asked if he needed some advice and he readily agreed.  I refused to fly it for him, but showed him how to rescue his'way too high' way too Close final turn using sideslip.  He seemed quite surprised as he said that his Mentor had Never show him this technique. ( What ? )   I removed my hands and feet from the controls, which he had been 'Following Through' before the landing and said "Your Turn"

 

I am Gobsmacked that this man had passed a GST with no knowledge of Sideslipping. . .is it just the odd few Instructors /  students with a very bad memory. . . ., or is the standard of instruction slipping. . ?  ( No Pun intended )

 

Either way, I was Fecking appallled. 

 

( At least HE paid for the Breakfasts )

 

 

 

 

Edited by Phil Perry
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I agree: few pilots seem to use this useful manoeuvre regularly, if at all.  My MiniMax slips very effectively, with large area control surfaces & low momentum. So a sideslip (or more accurately, a forward slip since it is along the direction of original travel), is my preferred method of losing excess height on late final. Yet on videos posted of MiniMax flights, I've never seen this - it's always a series of S turns at increasingly low level. Which strikes me as much more potentially dangerous.

 

And the instructor who I flew with to get my hours for converting my UK licence to Australian was alarmed when I banked more than 10º to start a slip. Why? It's a very controllable regime, provided you keep speed up, with adequate margin for position error on the pitot.

 

Bruce

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I am confused by the term forward slip which I learned only recently having been side slipping for many years. Apparently side slips are only for dealing with cross winds. It is explained in this link. But I humbly disagree... Biggles always sideslipped into a short field and that wasn't about dealing with crosswinds. 

 

http://clayviation.com/2017/10/04/forward-slips-vs-side-slips/

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 Sideslipping is the only way to see over a long nose. The bigger the angle the better the effect.  It's NOT just skidding flight..

     People don't teach it , IF they don't know how to do it themselves.

    If I was asked to estimate  (guess) what % does it half right it would be about 5%. Does the 30 degree max bank angle WE have thrown into the equation apply. If so. how silly is that?  Nev

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In my recent BFR in my Savannah we put the flaps up and sideslipped reaching a max descent rate approaching 1500 ft/min. A very effective way of losing height rapidly.

 

Cheers, Neil

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 It's not just the sink rate either . It's the steep approach angle you can achieve getting the wheels planted early on a short runway at an not excessive speed. If you are forced landing you overshoot till you are sure you will get in  then wash off  the excess height.  Nev

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I was never taught to sideslip and that is going back as far as the UK in 1970’s. Taught to spin and recover, but never taught to slip. I have asked several instructors but none have ever accepted. Fortunately, with my very draggy little CH701 I can get away with just putting the nose down until I get the height I need and then the speed bleeds off really quickly as I cross the threshold. I’d still like to learn though!

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I was taught in my Savannah how to sideslip....but really it was only to get used to how my aircraft responded as I had previously done it in my early glider training....I use sideslip all the time...I love it. Such a usefull tool in the arsenal

 

 

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On 11/25/2018 at 10:26 PM, facthunter said:

 It's not just the sink rate either . It's the steep approach angle you can achieve getting the wheels planted early on a short runway at an not excessive speed. If you are forced landing you overshoot till you are sure you will get in  then wash off  the excess height.  Nev

 

Some interesting responses there gents. . .  I was wondering if this technique had bee quietly deleted from the training syllabus along with the seemingly decreasing popularity of tailwheel  U/C configuration.

My very earliest instructional flights were in a DH82A. tail skid and long nose, so that every landing required some sideslip, so it was ingrained into my psyche from an early age.  

 

I've also heard the 'Forward Slip' term too, but mainly when reading American publications, or speaking to U.S. trained pilots.

Some airframes are better than others at sideslipping of course, 'Slab' sided fuselage types seem to do it better than those with 'Stick Insect' tailbooms unless the latter are fitted with a Huge rudder surface area .

 

I agree with Nev entirely RE the forced landing situation, especially due to this steeper angle of descent produced, ( Obstacle Clearance potential ) along with NO appreciable increase in forward speed, DOES help a lot when landing into a restricted  space.

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On 11/25/2018 at 10:17 PM, Neil_S said:

In my recent BFR in my Savannah we put the flaps up and sideslipped reaching a max descent rate approaching 1500 ft/min. A very effective way of losing height rapidly.

 

Cheers, Neil

I recall ONE particular aircraft where I never found the need to use sideslipping, and that was the lovely old C-172. . . why would you need to SS with those huge barn door fowler flaps deployed to the full 40 Deg ? ?

 

I remember the Hoo Har about the 172 having it's max flap reduced to 30 Deg Max years ago following ONE accident in the USA where the pilot blamed a sudden Pitch down when slipping with full flap, but we discussed that at length on Rec Flying back in 2013 think it was . . .The pilot said that the huge flaps shielded the Elevator and caused the Pitch own. . .  Can't remember if it was proven aerodynamically that this could FEASIBLY occur . . .  but the US being very afraid of Litigation, put out a mandatory AD.    Shame really . .  darned lovely Well Sorted airframe. .  Just because some wanker got too slow on the approach. . . WE call that 'Stalling' usually. . .    ( apologies for the /sarc )

Edited by Phil Perry
Typo.

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On 11/25/2018 at 9:44 PM, pmccarthy said:

I am confused by the term forward slip which I learned only recently having been side slipping for many years. Apparently side slips are only for dealing with cross winds. It is explained in this link. But I humbly disagree... Biggles always sideslipped into a short field and that wasn't about dealing with crosswinds. 

 

http://clayviation.com/2017/10/04/forward-slips-vs-side-slips/

 

HAHA. . . Love the 'Biggles' reference PM. . . . but he was good enough to sideslip with the stick between his knees, whilst smoothing some Brylcreem into his hair, in case there were any Ladies about on the ground !

 

Most GA pilots visiting our field seem to use the 'Crabby' technique. . .  then struggle to stop on our short strips. . .I've  often wondered why they do that. . .

Yet One of the lads at Otherton  owns a PA28-140, which he Slips onto the numbers and easily turns off the strips at the middle intersection in nil wind condx. . .All down to proper training and Knowing your aeroplane. . . Ditto with the Airfield Manager and his Vans RV4. . .( Rich Git ! )

Edited by Phil Perry
2 x typo and bad grammar. . .

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5 hours ago, Phil Perry said:

...... remember the Hoo Har about the 172 having it's max flap reduced to 30 Deg Max years ago following ONE accident in the USA where the pilot blamed a sudden Pitch down when slipping with full flap, but we discussed that at length on Rec Flying back in 2013 think it was . . .The pilot said that the huge flaps shielded the Elevator and caused the Pitch own. . .  Can't remember if it was proven aerodynamically that this could FEASIBLY occur . . .  

Rich Stowell’s book on Stall/Spin Awareness has information quoted from a Cessna test pilot - yep, it will happen, different behaviour in different models .... from memory rectified in later models however the warning in the AFM may have been retained.

 

Sideslipping turn was in CASA’s Day VFR Syllabus and is still in the Part 61 MOS.

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On 11/26/2018 at 9:11 AM, facthunter said:

 Sideslipping is the only way to see over a long nose. The bigger the angle the better the effect.  It's NOT just skidding flight..

     

Definitely not skidding...

 

I routinely do a slipping turn onto final so I can see where I’m going and a 9 knot XW max means the into wind wing is usually down in the flare. The Auster has barn doors, too.

 

kaz

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7 hours ago, Phil Perry said:

 

...Some airframes are better than others at sideslipping of course, 'Slab' sided fuselage types seem to do it better than those with 'Stick Insect' tailbooms unless the latter are fitted with a Huge rudder surface area .

 

My Jodel's small rudder (with no fin) makes slipping easy. I've done some glorious slips all the way to the ground; just release pressure on the rudder at the last moment and she lines up beautifully.

I'd like to reduce approach speed as much as possible, but a very experienced Ag pilot cautioned against using flaps while slipping. I'd welcome further advice.

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  IF the plane has a lot or rearward "keel surface" THAT requires rudder to oppose it's natural tendency to weather cock straight. Doing sideslips properly is not something you just DO. You need to have precise control of airspeed and the lowest possible bottom wing and the exit should be smooth and well co-ordinated if you are combining it with a landing flare. The effectiveness of the rudder is your limiting control eventually (usually).

      You can make it a sideslipping turn by careful rudder variance which is a real neat and effective way of getting into tight places like where a  line of trees is on the  approach to final for instance. and you want to be high and inside them for safety . and use the least runway.  You probably need something like 30 hours of total time doing this stuff, including the original instruction. to be really on top of it in all situations of wind and X wind .

     I usually enter from straight and level power off, speed reducing by rolling the lower wing right down and holding the nose up with  FULL top rudder and practice getting the airspeed exactly where you want it, as you descend. The nose may be at a slightly higher pitch attitude than normal but find it out at height  not  near the ground and the airspeed may have a significant error due to the angle with the airflow. You don't want it to be overly high just safe above stall, but find the correct one by experiment for your plane. You can only do this at altitude, as for a while you may NOT control the plane that well. If it degrades into an ugly skid start all over again. Remember IF you get this mucked up the controls are completely crossed and IF you pull the stick back you are set up for an instant spin situation.

   Most Instructors will say they can DO this but you will soon find out. IF the wings stay near level go elsewhere. A different plane is DIFFERENT. You presume little and till you know what it does don't think you will just get it "right" first time because you have done it on other aeroplanes.

As to the flaps, OK ,that would be design specific and it's another factor to consider and may bite you if you get it wrong. You are unlikely to be above Vfe when you come out of the slip so I would take final flap then when lined up to land. IF you are too fast you will balloon and undo ALL of your good work.

 Generally you aim to be stable and lined up in the landing configuration at some hundred feet or so and  the slipping approach I describe is not a "normal" approach  but one you might use when actually forced landing or part of essential advanced training..Nev

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On ‎11‎/‎26‎/‎2018 at 5:44 AM, pmccarthy said:

I am confused by the term forward slip which I learned only recently having been side slipping for many years. Apparently side slips are only for dealing with cross winds. It is explained in this link. But I humbly disagree... Biggles always sideslipped into a short field and that wasn't about dealing with crosswinds. 

 

I've always understood it as:

 

A sideslip is when you are wing down into wind, but with the longitudinal axis of the aircraft aligned with a ground feature, eg a runway, a sheep track, crop stubble lines, or 4WD wheeltracks. You could conceivably use a slight sideslip in place of a crab for tracking in general flight - but it wouldn't be a popular configuration with the pax.

 

A forward slip is achieved by using rudder to maintain a crab angle to the ground feature, and lowering the inwards wing with aileron. It will dramatically increase the R-O-D, but, as discussed, comes the moment to convert it to either a nil wind/wing level landing, or, in cross-wind, a wing down/and rudder controlled fore-aft alignment with the runway. The latter requires a lot more finesse, and hence, loads of practice.

 

Skill in all slipping is fundamental in achieving requirements in emergency situations such as forced landings, short field landings, precautionary S&L, crosswind landings.

 

Do I teach it?  Always - and it wouldn't matter if the aircraft had the descent capability of a Stuka.  Electric flaps do fail. Crosswinds can be so high that full flap is inadvisable and aggressive slipping may be called for.

 

happy days,

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As you say, flying wing down would not be popular with Pax also it is inefficient aerodynamically. Crab is the logical way with a quick alignment to the runway at flare or sometimes to an into wind, wing down  landing on one wheel. This is usually limited by the engine(s) or flap trailing edge or normal wingtip on a low wing plane .

  People often say do you do slipping or crab when often the answer is a combination of BOTH. When kicking straight you must ensure the into wind wing doesn't lift and end up banking the wrong way  .This is the worst likely BAD situation you will encounter if you don't know what you are doing. You will see a lot of jets these days landing without kicking the plane straight. This puts  a high load on the undercarriage  and tyres, but keeps the Plane in the middle of the strip. I don't like it as you should be able to do better than that, even with X wind components around 40 knots, in a larger Jet Nev

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With my training to PPL standard in the early 1970's sdseslipping was not covered during my all Cessna aircraft training. Post PPL issue, with the same instructor, when I acquired Tiger and Chippie endorsements sideslipping then came strongly into play, especially the Tiger which we would slip right down into the flare, after taking into acount any crosswind so we were not arse about face. I can remember starting my Class 4 Instrument training in a C172 on a pitch black night, and having my instructor on one circuit indicating we were a bit high. I kicked in about a ball of sideslip only to experience an absolute explosion from the right seat!! Not worth repeating.

 

Buying a Victa Airtourer really did bring the benefits of sideslipping to the fore. Cleared for a full flap sideslip up to 87 knots it gave a remarkable versatility to approaches, with great control authority. I have done a fair amount of flying in Light Aircraft Championships and bemoan that a lot of the advantatages that the Airtourer posssesses are precluded, especially in the Force Landing component.

 

I recall competing inthe Australian Light Aircraft Chamionships at Jandakot where the first round of the Spot Landing Competition was conducted with a quartering tailwind. Only three arcraft scored ground points- two Airtourers and a Robin 2160- all landed off sideslips. All other aircraft went soaring past the ground markers. Bernie Saroff, my Air Judge, was far from amused and it was not until I showed him a 1964 Victa Handling Notes that he has prepared to accept that I had not gone outside the aircafts operating paramaters.

 

One consideration not mentioned thus far is the possibility in a sideslip, particlarly in a low fuel situation, so all the fuel to ends up at the wrong end of the tank, and most engines doen't run too well on air. A possibile extreme example, but who wants to invite Murphy on board?

 

I can remember many discussions as to whether to slip the garden variety Cessnas or not. Other than the references to the fuel situation, I have not noted any POHs that precule slipping, and have in my Cessna 172M ownership slipped it quite comfortably, though never aggressively. Comments on the C177 were to excercise caution, though I can not remeber too many of them falling out of the sky.

 

Poteroo's early comments are particularly pertinent, though gaining exposure to Ralph's wealth of knowledge and experience is not so easily achieveable these days. He may be in the mature category, but as a survivor of both PNG and aggie work I always appreciate his perspective.

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My PPL training also did not include side slipping or spins. I was taught power/flap stalls with a wing drop and recover (incipient spin) but never taken through a complete rotation. If I was high I was taught to do S turns to reduce height or in a 152 just put the nose down with flap & height would bleed off really fast without much increase in air speed.

 

Real spins and side slips came later when I asked about it & the CFI took me through the process & then I carried out some solo practice. Side slipping though is a very useful function to lose height quickly as in short field or high obstacles etc and everyone should be taught and practice this. It is also an essential skill flying an aircraft without flaps. As Nev said slipping with flaps can be hazardous depending on design as Vfe can be exceeded quickly

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13 hours ago, naremman said:

...Buying a Victa Airtourer really did bring the benefits of sideslipping to the fore. Cleared for a full flap sideslip up to 87 knots it gave a remarkable versatility to approaches, with great control authority...

The CT-4 is a development of the Victa and lots of them operate locally. I've read that their triangular leading edge extensions (actually fuel tanks) have improved stall performance. That's one modification I am considering to improve my Jodel's stall behaviour, but I need to hear from people who know this well.

 

image.jpeg

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Henry used to tell us that the whole wind/tunnel shook when the model stalled! The prototype had a violent uncommanded roll which was fixed by the wing fences. Seems to me that those cuffs were too large. I have a copy of the Aircruiser W/T test report.

 

I’ve used smaller wing root cuffs successfully.

 

As an example take a look at the T-34C.

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I'm forever grateful that my (early 1970's) original flying experience was in a glider where spins, spiral dives, and sideslipping were a major part of my basic training, (along with rope & winch-break straight ahead forced landings that were somewhat common).  All my glider final-approaches were set up somewhat too high, so sideslips on final were normal, then levelling the wings near flare, along with use of spoilers near touch-down.

These days, I'm happy that my Eurofox (with its full-length hanging flaperons) makes an excellent platform for well-controlled sideslipped short landings.  It is particularly helpful at unfamiliar aerodromes where there may be unseen wires, fences etc. on short final.  My natural approach instinct has a steeper angle of decent on short final, so sideslips are second nature to me, and the steep angle keeps me well away from any unknown/unseen obstacles on my approach to the threshold.  Yes, sideslips are always a natural option for me.

Edited by dsam
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