Engine failure video

[double_barrel]

I thought his may be of interest

Youtubers are lining-up to say what a hero the pilot was, but It seems to show a very badly handled engine fail within easy reach of a runway. Any comments? Any suggestions on options after she found herself over the threshold and WAY too high and fast? Other than don't come in too high and fast.

https://www.youtube.com/watch?v=rCLGtYESESs

[HOVIS]

Not a pilot here.
Apart from the bounce, what exactly is wrong?

[double_barrel]

Not a pilot here.
Apart from the bounce, what exactly is wrong?

The approach was WAY too high and fast with the result that she came within a hair's breadth of wrapping it round a tree. She could easily have dumped a lot of energy before she reached the threshold. I don't know, but I'm guessing there's a good chance she could have made that approach her downwind leg and landed in the other direction. Once over the runway with full flaps, it was never going to be pretty, but even then she could have something - anything - rather than float on by. I have never had an engine fail for real, but even a lowly PPL like me has done many practice engine-out approaches and landings. That was horrible.

[172_driver]

That was horrible.

Harsh judgement. She walked away alive.

And it looks like the plane can be used again... (after the engine is fixed, that is).

[henra]

I thought his may be of interest
Youtubers are lining-up to say what a hero the pilot was, but It seems to show a very badly handled engine fail within easy reach of a runway. Any comments?

Aircraft still in one piece and without a scratch. Crew could walk away. Aircraft + Crew can be re-used.
NTSB Database and graveyards are full of examples with completely different outcomes. 'nuff said.

OK, Armchair Chuck Yeagers can pontificate what marks for style they give for this one. I'm only impressed by things which people actually have done/achieved not so much by people who theoretize how they would have done better..
The difference between theory and practice is bigger in practice than in theory.

[double_barrel]

Aircraft still in one piece and without a scratch. Crew could walk away. Aircraft + Crew can be re-used.


Fair enough. But it looked very close to a disastrous outcome, anything to learn here?

[havick]

I thought his may be of interest

Youtubers are lining-up to say what a hero the pilot was, but It seems to show a very badly handled engine fail within easy reach of a runway. Any comments? Any suggestions on options after she found herself over the threshold and WAY too high and fast? Other than don't come in too high and fast.

https://www.youtube.com/watch?v=rCLGtYESESs

have you personally put down a real engine failure in a single before?

[double_barrel]

have you personally put down a real engine failure in a single before?

Sigh. No I have not, as I said above.

OK, it was brilliant. No lessons here.

[pilotmike]

I agree the judgements are too harsh. Two people walked away and the plane is un-bent. A perfect result. Some small areas for improvement - if God forbid, she suffers another - but hey, a great end result.

Never forget, real engine failures are WAY harder than simulated ones. Please remember, double_barrel, the plane comes down quicker and has a lot less glide range than simulated ones with the engine at idle. In almost any position the prop stops, there is likely to be disrupted airflow to the wing, hence increased stall speed is a further issue. And that is likely to affect just 1 wing only, further increasing the potential danger. So obviously it is extremely wise to carry a few knots extra. I know this because I have taught 100s of simulated failures, and handled 3 for real. They are very, very different situations. And the pulse is usually much higher on a real one, knowing that you can't simply apply power and go around if it looks bad. She kept her own emotions and the plane apparently under perfect control. Well done to her!

Compared to the alternatives of panicking then stalling, hoping that you might make it downwind (as you suggested) then spinning in on the final 180 degree turn, undershooting and crashing, overshooting and crashing, bending the undercarriage, flipping it over, ground looping, or any other of the many, many ways to cock it up, her outcome was way better than any of them.

Incidentally, can you tell us all how much height a 172 with the engine stopped, with the prop disrupting flow to the wings, with full flap, flying say 5 knots faster than usual to compensate for increased stall speed will lose in a perfectly balanced and perfectly executed 180 degree turn like yours would be? And how much extra height would be lost if it is wasn't quite perfectly balanced and perfectly executed, like yours?

Perhaps you'd be good enough to send in a video of your first REAL engine-out landing, and we'll collectively comment on it, ridicule it, full it apart, and generally criticise it - assuming you survive it and aren't too embarrassed by any damage or injuries sustained so as to not want it in the public domain? No? I thought not!

But PLEASE, don't be tempted into trying any 180 degree turns at low level with the engine out, unless you really know what you're doing. Just take my word for that one. She clearly made some good decisions and choices when her engine failed.

[henra]

Fair enough. But it looked very close to a disastrous outcome, anything to learn here?
No, not close to a disastrous outcome. At worst close to dinging the thing a tiny bit. For a disastrous outcome it would have taken an attempted 180. Graveyards are full of 180 attempts following engine problems. After continued VFR into IMC one of the big killers in GA. Therefore I give her highest marks in judgement. Could she have made it more beautifully? With a fine tuned and not fu*ked up side slip probably yes. But remember: When the fan quits any energy you dissipated is gone and not available any more as your asset. Therefore again: Good judgement to keep a bit energy excess (although obviously the excess energy was a bit on the high side).

[Dorf]

I thought his may be of interest

Any suggestions on options after she found herself over the threshold and WAY too high and fast? Other than don't come in too high and fast.



Um, at that point I think her alternative was crash in the trees. You do understand that If your engine doesn't work you can't go around, right?

[henra]

But PLEASE, don't be tempted into trying any 180 degree turns at low level with the engine out, unless you really know what you're doing.

I would even rather delete that part. There are many very experienced high time pilots who were highly regarded and considered to know what they are doing who died trying this.

[Nightstop]

I nursed a SLAC PA28 Piper Cherokee back into Southend UK from a training flight near Abberton Reservoir with a rough running engine in ‘76. I really didn’t know if we’d make it that far. I deliberately came in high, in case the engine failed completely. Landed OK. A piston had failed. The Boss wasn’t happy, ungrateful or what!

[RatherBeFlying]

NS, the Boss would be happier with a write-off than an expensive engine repair job (not covered by insurance) :p

[kghjfg]

Looks good to me.

In an engine out situation you really don’t want to try and stretch the glide.

I too have never had a real one, I know people who have, and apparently they are nothing like a PFL.

I’d much rather be this little bit too high, in fact I was taught it’s fine to run off the end of the field at low speed, but you really don’t want to be hitting the hedge before the threshold at best glide speed.

double_barrel

IMHO, The learning point is, it’s better to arrive high and go into trees on the ground at low speed than it is to arrive low and hit something before the threshold at high speed.

[CHfour]

I've done quite a bit of para dropping with short circuits on similar aircraft and think people are being far too harsh here. I don't think she had anything like enough energy for a downwind join to the reciprocal runway. The only criticism from me would be that an aggressive bit of side slipping on short finals would have got her nicely on profile. I know some say never side slip with full flap but it actually works a treat as long as you remember to kick it off in time! IMHO a good job!

[Maoraigh1]

Impressingly calm. Landing looked O.K. My only experience of engine failures have been vapour look and card ice on take-off, with a long runway to land ahead. Elevator and rudder feel different without propwash. Were there high trees at the approach end also?

[pilotmike]

Card ice - the very worst kind. Trumps all others. Plays tricks on you. You're on the button with that one. Good call! Pleased you raised it.

[West Coast]

Fair enough. But it looked very close to a disastrous outcome, anything to learn here?

At my airline and many others after each flight, after arriving at the gate/stand a debrief is conducted and I give the CFI the benefit of the doubt that she and her student did exactly that. During the debrief we also acknowledge the positives, and an engine failure (of your only engine) with no damage and no injuries is positively the best outcome.

Walk a mile….

[ChrisVJ]

When I learned to fly 56 years ago all my practice forced landing on the airfield came in close over the fence and all were deemed satisfactory.

When I had an overheating engine on downwind leg 45 years later I aimed for the same and was lucky to be able to restart for a "blip" of engine to get me in. Later a more experienced pilot told me I should have aimed "a third of the way down the runway" for an engine out landing. Did not occur to me in the (over-)heat of the moment. Should be taught as standard practice.

[First_Principal]

I'm with those that consider this a positive result. Far too many variables we don't know about to comment further on the approach...

... however I didn't hear a 'mayday' or 'pan pan' call? Maybe she did call it out but wasn't part of the clip, or perhaps it's not what you do wherever this is, but that's something drilled into me - not just to use if needed, but to react to if I hear it. Not sure the word 'emergency' would penetrate quite so immediately as 'mayday' repeated 3 x etc.

Whatever, I'd be happy to shake her hand for doing a good job in the circumstances she was presented with :ok:

[finestkind]

No, not close to a disastrous outcome. At worst close to dinging the thing a tiny bit. For a disastrous outcome it would have taken an attempted 180. Graveyards are full of 180 attempts following engine problems. After continued VFR into IMC one of the big killers in GA. Therefore I give her highest marks in judgement. Could she have made it more beautifully? With a fine tuned and not fu*ked up side slip probably yes. But remember: When the fan quits any energy you dissipated is gone and not available any more as your asset. Therefore again: Good judgement to keep a bit energy excess (although obviously the excess energy was a bit on the high side).

Maybe I am missing something here with talk about a 180 being dangerous. No argument if low level (having practised numerous in various aircraft and yes to nail it is great but chances of doing so very unlikely). But did I miss something in the clip as is that not what happened at height to return to the reciprocal ?

[Edgington]

They walked away and didn't do any damage with that landing.

Facts are she was high and fast. However you can't judge as to why or what they should have done better as you don't have all the facts. Where were they when the engine failed, how high? Have you had a look at the area surrounding the airfield? Doesn't look they had any other real options other than return, depending on many things you might choose a tailwind.

We actually did AOC work on a C172, from an airfield where there were no options in case of an engine failure. Only way to get the CAA to allow us to operate from there was by doing turnbacks, often having to take a tailwind on landing.

[ScepticalOptomist]

Are you kidding me double_barrel? Nothing wrong with a well handled emergency. Excellent job by the pilot.

The lesson I hope you learn is a little bit of knowledge or experience - which is all you have - is very dangerous.

As others have posted, 180 degree turns etc have killed many experienced aviators.

Armchair experts like yourself denigrating another pilot after a successful emergency are the bane of aviation worldwide.

[Switchbait]

No one hurt, airplane undamaged, good result.

Lessons to learn… only bit of advice I could add here is, maybe a short side slip would have gotten her into a better touch down zone point earlier. If you aren’t familiar with side slipping on final to lose height, whilst maintaining the centreline, I suggest you go out and learn/practice it.

[radeng]

What I find so amazing is the bloody awful radio audio quality. The Maritime Radio Service would never accept that What we radio engineers would describe as "six parts distortion and 4 parts abortion"...

Even radio amateurs and CBers can do better than that...

[Pilot DAR]

If you aren’t familiar with side slipping on final to lose height, whilst maintaining the centreline, I suggest you go out and learn/practice it.

I second that, it's saved an imperfect forced approach for me a couple of times. Yes, a 172 can be safely slipped with flaps extended....

For me, four complete engine failure landings, and two more where I had power available, but elected a power idle from cruise flight forced landing ('could have gone around, but did not).

[RickNRoll]

I nursed a SLAC PA28 Piper Cherokee back into Southend UK from a training flight near Abberton Reservoir with a rough running engine in ‘76. I really didn’t know if we’d make it that far. I deliberately came in high, in case the engine failed completely. Landed OK. A piston had failed. The Boss wasn’t happy, ungrateful or what!
That would be human nature. You would tend to be too high than too low. Too low you can't ever get back up again. Guessing here, she knew she was too high as well when she came in.

[megan]

Any landing you can walk away from is a good one, if you're able to use the aircraft again that's a bonus. Her approach was over a residential area in a thickly forested area, absolutely no way an undershoot would have turned out well, perhaps she kept height in hand for possible wind shear, some thing a regulatory check pilot gentle chided 30 hour me for on a check ride for a scholarship in a C150 where I planted a simulated engine failure virtually on the numbers of an airport, the forest would shield the runway from ambient wind. Bar a grilling who knows her thoughts. Sure she may have side slipped of the excess height, but if she was happy with the way things were progressing then why? Why didn't she side slip? She may have been conscious of the cautionary note in the flight manual about side slipping with more that 20°, flap and not wished to experiment if it was to be her first time. Her judgement proved to be impeccable as the results show. I'm sure she would have gone away and thought it through as to how she could have done things different, she has ticked a box that not a lot of people get to do and is far richer for the experience. Some folk could win the lottery and still complain the pool wasn't big enough.Steep slips should be avoided with flap settings greater than 20° due to a slight tendency for the elevator to oscillate under certain combinations of airspeed, sideslip angle, and center of gravity loadings.

[m0nkfish]

Of course there will be lessons, we are always learning all the time! In a real emergency though it is the result that counts, and this seems to be a great result (no injuries, aircraft safely on the ground, and in fact on a runway which is a big bonus). I doff my hat to the pilot for her calm and clear radio communication as well.

I think the biggest lesson to learn here though is for you Double Barrel. Coming onto a flying forum and starting to pick holes in what clearly is a great bit of airmanship is, in my humble opinion, very poor form. I'm surprised you've not already deleted the thread because its just made you look like a bit of a plonker.

[double_barrel]

Blimey folk. I think you are all being a bit harsh on me here. I make no claim to be a sky god; I am possibly the least experienced PPL on here. But I was really hoping for some thoughts on how the margins of error could have been increased in this incident. It looks scary to me. I can't tell how high or far she was when she started her descent, but in practice engine outs I would have been very heavily criticized by my instructor for that. I do believe a better planned approach would have been safer, am I evil for asking for thoughts on that? Of course I make no claim that I could have done better. In my GFT, I was criticized by the examiner for not landing on the numbers in a practice engine fail, which I felt was a bit harsh. And most especially, I was hoping for thoughts on how to handle the situation when absolutely committed to land, but still high, with 40deg flaps and the runway disappearing behind me. To repeat. I don't claim I would have done better. I am innocently asking why a much more experienced instructor did not do better. If the group opinion here is, that under pressure and in a real emergency, that's a good job - fine, I accept that. But please don't rip into me for asking you opinions! I did look horrible to me, but I am very willing to listen and learn.

I second that, it's saved an imperfect forced approach for me a couple of times. Yes, a 172 can be safely slipped with flaps extended.....

Thanks, that's the sort of input I was hoping for,

[Ollie Onion]

For sure they were a bit high and landed long, but given the trees around the runway I would have rather landed long than fallen short into the trees. What I find most interesting is in every part of the video and description the Instructor is referred to as ‘The Female Pilot’. End of the day it was a good job.

Personally whenever I have practiced forced landings and for one I did for real from the downwind I always start with my aiming point in the middle of the available strip that way I can bring it back with a bit of side slip or if I am a bit low I know I have a bit of margin. I have seen the result of someone falling short into trees so at this airfield As I say I would have preferred to be long. Perhaps we could argue that a bit of side slip towards the end may have increased the safety margin but it may have also been a case of at 300’ the assessment was that they would comfortably stop.

Have a look at the airfield data here: http://www.airnav.com/airport/3n6

lot’s of mentions of tree obstacles.

[Bames]

I agree the judgements are too harsh. Two people walked away and the plane is un-bent. A perfect result. Some small areas for improvement - if God forbid, she suffers another - but hey, a great end result.

Never forget, real engine failures are WAY harder than simulated ones. Please remember, double_barrel, the plane comes down quicker and has a lot less glide range than simulated ones with the engine at idle. In almost any position the prop stops, there is likely to be disrupted airflow to the wing, hence increased stall speed is a further issue. And that is likely to affect just 1 wing only, further increasing the potential danger. So obviously it is extremely wise to carry a few knots extra. I know this because I have taught 100s of simulated failures, and handled 3 for real. They are very, very different situations. And the pulse is usually much higher on a real one, knowing that you can't simply apply power and go around if it looks bad. She kept her own emotions and the plane apparently under perfect control. Well done to her!

Compared to the alternatives of panicking then stalling, hoping that you might make it downwind (as you suggested) then spinning in on the final 180 degree turn, undershooting and crashing, overshooting and crashing, bending the undercarriage, flipping it over, ground looping, or any other of the many, many ways to cock it up, her outcome was way better than any of them.

Incidentally, can you tell us all how much height a 172 with the engine stopped, with the prop disrupting flow to the wings, with full flap, flying say 5 knots faster than usual to compensate for increased stall speed will lose in a perfectly balanced and perfectly executed 180 degree turn like yours would be? And how much extra height would be lost if it is wasn't quite perfectly balanced and perfectly executed, like yours?

Perhaps you'd be good enough to send in a video of your first REAL engine-out landing, and we'll collectively comment on it, ridicule it, full it apart, and generally criticise it - assuming you survive it and aren't too embarrassed by any damage or injuries sustained so as to not want it in the public domain? No? I thought not!

But PLEASE, don't be tempted into trying any 180 degree turns at low level with the engine out, unless you really know what you're doing. Just take my word for that one. She clearly made some good decisions and choices when her engine failed.

Sorry, but I have to disagree. A windmillimg propeller creates a lot more drag than a stopped one. If you actually have an engine failure and want to extend your glide try to reduce speed enough to stop the propeller from windmilling. And there is absolutely no need to "compensate for increased stall speed". Check the definition of stall speed, plus the slipstream from produced by a windmilling propeller of an engine running on idle power has zero effect anyway. Otherwise I have to agree that she saved the aircraft, well done.

[Auxtank]

Looks good to me.

In an engine out situation you really don’t want to try and stretch the glide.

I too have never had a real one, I know people who have, and apparently they are nothing like a PFL.

I’d much rather be this little bit too high, in fact I was taught it’s fine to run off the end of the field at low speed, but you really don’t want to be hitting the hedge before the threshold at best glide speed.

double_barrel

IMHO, The learning point is, it’s better to arrive high and go into trees on the ground at low speed than it is to arrive low and hit something before the threshold at high speed.

Where's the "Like" button - if I could find I'd hit it.

[LOMCEVAK]

double barrel,

Some thoughts from me. If you have an engine failure and turn to point at the airfield on a track that is roughly aligned with the runway the first decision is whether or not you have the energy (airspeed and height) to make a downwind 'low key' position such that you can make a finals turn to land on the into wind/take-off runway. If you do not have sufficient energy for that option then you must land straight on the downwind runway or land off airfield. There are some considerations and practicalities in these cases but please note that these are generic and are not all are applicable to this incident.

There is a tendency with the downwind/low key option of using an aim point to focus on the runway threshold or even 1/3 into the runway whereas what is required is an aim point which, worst case, allows a touchdown with just sufficient runway remaining to stop. In many cases this is well past the midpoint of the runway and unless the pilot has thought about and practised this it is not an intuitive pattern. Sadly, a frequent result of attempting such a pattern is that energy is too low and a stall during the finals turn occurs. The Red Arrows accident at Valley in 2018 is a case in point.

For the straight in approach, if high/excessive energy exists there are three potential ways of losing energy, although it may not be feasible to use all of them in a given aircraft type. First, sideslip to generate drag, and if this is feasible it is often the best option. Secondly, aggressive 'S' turns but there is a definite stall potential in doing this unless the pilot is very experienced, especially on type, and has a good understanding of the accelerated stall characteristics of the aircraft type. Thirdly, diving to increase speed such that the increase in zero lift drag causes a significant energy loss and then a prolonged flare to hold off to a normal touchdown speed, although this relies on an aircraft that has high zero lift drag anyhow and does not apply to many light aircraft. In this straight-in situation there is also the possibility of having insufficient energy to make the runway in which case an early decision must be made to pick a field for an off-airfield forced landing.

In the case of the video that you have posted, we must be careful in interpreting the energy state because upon the camera lens characteristics. The upper and lower views give a different impression of flightpath angle so it is difficult to judge the energy state of the aircraft versus range from the runway. Also, the tailwind component would have affected the flightpath and this has not been quoted. However, I would doubt if a downwind/low key option was an option. I don't know the characteristics of a C172 but I doubt if the option of diving to lose energy was worthwhile. Very few pilots have practised hard 'S' turning so it would have been unwise to attempt this if not practised. The decision on sideslipping or not may have been driven by many factors, such as Flight Manual advice and familiarity, but the key is that the approach and touchdown point must be judged with respect to the far end of the runway and not the threshold and if there is one point to take away from this incident then perhaps that is it. It appears to me that the judgement here was correct because the outcome was very successful.

My experience of single-engined aircraft engine failures is on types that are considerably heavier and faster than the C172 but the principles were the same. However, the one that sticks in my mind is when a friend suffered a catastrophic crankshaft failure, could see a suitable runway so turned towards it but decided too late that he could not reach it, turned hard to avoid the woods short of the runway, stalled, crashed and was killed. And I had flown that aircraft on the previous sortie and went to the crash site with the accident investigation team the next day. Some things stay with you very vividly for ever.

I hope that this has been useful.

[ShyTorque]

I doubt that many instructors are very experienced at downwind, real engine out landings. Seems to me that she did the job very adequately, even if it wasn’t a “text book” approach to a point 1/3rd of the way up the runway. The site was surrounded by tall trees so there possibly was no option other than to make the landing downwind.

I recall my fixed wing CPL flight test (over 25 years ago, with Dai Heather-Hayes). During the PFL, being far more used to helicopter glide angles, I arrived over the runway with a lot of extra height, but managed to lose it using an S turn and side slipping and made a decent landing. I was a bit embarrassed because I was very aware, but in the debrief Dai simply said that I had arrived “in a very advantageous way”.

[CallumJohn]

The approach was WAY too high and fast with the result that she came within a hair's breadth of wrapping it round a tree. She could easily have dumped a lot of energy before she reached the threshold. I don't know, but I'm guessing there's a good chance she could have made that approach her downwind leg and landed in the other direction. Once over the runway with full flaps, it was never going to be pretty, but even then she could have something - anything - rather than float on by. I have never had an engine fail for real, but even a lowly PPL like me has done many practice engine-out approaches and landings. That was horrible.
Honestly if this is a new student I wouldn't be so hard on them, they did a good job with their experience.

[CallumJohn]

The approach was WAY too high and fast with the result that she came within a hair's breadth of wrapping it round a tree. She could easily have dumped a lot of energy before she reached the threshold. I don't know, but I'm guessing there's a good chance she could have made that approach her downwind leg and landed in the other direction. Once over the runway with full flaps, it was never going to be pretty, but even then she could have something - anything - rather than float on by. I have never had an engine fail for real, but even a lowly PPL like me has done many practice engine-out approaches and landings. That was horrible.
ohp, watched the video and if the "She" they were referring to is the trainer and not the trainee, then yeah definitely it's screwed up.

[pilotmike]

Sorry, but I have to disagree. A windmillimg propeller creates a lot more drag than a stopped one. If you actually have an engine failure and want to extend your glide try to reduce speed enough to stop the propeller from windmilling. And there is absolutely no need to "compensate for increased stall speed". Check the definition of stall speed, plus the slipstream from produced by a windmilling propeller of an engine running on idle power has zero effect anyway. Otherwise I have to agree that she saved the aircraft, well done.
Why are you disagreeing? What I actually stated was "In almost any position the prop stops, there is likely to be disrupted airflow to the wing, hence increased stall speed is a further issue" . This is factually correct. So there is nothing to disagree with. I never compared the drag of a genuine windmilling propeller (ie. driving a completely failed engine which is producing ZERO power whatsoever) to a stationary propeller. However in your example of an engine / propeller at idle, almost certainly the stationary propeller creates more drag, and definitely it increases stall speed if it disrupts airflow over the wing at all, which is almost inevitable.

Regarding your false claim that "And there is absolutely no need to "compensate for increased stall speed"", you are mistaken. Of course a stopped propeller disrupting airflow to the wing will increase the stall speed! Any disruption to airflow to a wing will reduce the lift it produces for any given angle of attack & airspeed combination. Therefore the increased angle of attack required for any given airspeed will be closer to stalling. THAT is the relevant definition of stalling and its relationship to stall speed, as in this example. What alternative "definition of stall speed" were you suggesting I should be checking? Please let us know, I'd love to hear it.

It seems you are confused by this.

To make it very clear and simple for you, take an extreme example which proves the general case: if you progressively disrupt the airflow to let's say 50% of the wing, more, 60%... more , say to 90% of a wing, do you honestly believe the stall characteristics of that wing remain identical to the undisturbed case? You are trying to claim that in all these cases, the wing flies as normal and still stalls at exactly the same airspeed, and that "there is absolutely no need to "compensate for increased stall speed" for any wing with disturbed airflow, which is completely wrong. That is dangerously flawed advice, potentially very dangerous.

As for your further comments " plus the slipstream from produced by a windmilling propeller of an engine running on idle power has zero effect anyway" this is so muddled and unclear as to make zero sense. Whichever way, and whatever you intended to say, trust me, the difference between the flight characteristics with an engine at idle and a stopped propeller are significantly different. For you to claim otherwise proves you have never experience a stopped propeller, unlike some of us who can tell for definite that it does - significantly.

So, disagree all you like, but I recommend you check a few facts and try to understand the physics and fundamentals of stalls and stalling before criticising pilots, flying instructors, who clearly understand aerodynamics rather better than you. Some of the misconceptions you hold are potentially quite dangerous in flight, especially in emergency situations such as total engine failure.

May we enquire your flying instructing experience, and where you claim to find these aeronautical myths from, which you then try to correct flying instructors about, please? But please stop the potentially dangerous claims of absolutely no need to "compensate for increased stall speed" for cases of total engine failure; you could cost people's lives if they make the mistake of believing your myths and misunderstandings.

[punkalouver]

Overall, a very successful outcome due the the pilots actions. Let’s face it, plenty of us have misjudged our own practice engine out scenarios.

I find this non-analyzing belief of you must land straight ahead after an engine failure to be a dangerous mindset. Who knows what is straight ahead.

This incident took place at the Old Bridge Airport. Take a look on google earth on the landing options around there, it is not good. How about turning toward the airport. It seems to have worked out well.

The video is a great example of how a slip should be used to one’s advantage instead of accepting a long landing(if safe to do so on aircraft type). In fact, it should be planned for as an option on every engine out scenario for similar types.

In general, aim for one third down the landing location which gives you some margin in case you find yourself low on energy(reduces the odds of not reaching the runway) and then enter a forward slip in if too high.

In this case, a good slip would have been useful to prevent a long but otherwise successful landing that was slightly downwind……and a tailwind can easily cause a long landing.

An aggressive slip should also be considered for an engine failure on takeoff when some runway is left ahead of you and the options beyond the runway are poor. There may be several variables to consider but on many small aircraft, one can lower the nose, initiate an aggressive slip and have a successful landing possibly with a partial but relatively low speed runway overrun rather than a relatively high speed touchdown in a much riskier area.

[old,not bold]

I've had 3 engine failures in an SEP, 1 in an Auster and 2 in a Prentice. The Prentice failures resulted from magneto failure while flying in cloud in Italy, and from an engine fire just after take-off in Baghdad. In both I was extremely lucky to get away with it, mainly because the training and culture at Sleap in the early '60s was superb. We practised forced landings, stopping the propeller, spot landings without engine, and similar, usually competitively to add interest.

The Auster incident is relevant to the Impossible Turn. The club had a rule that before a first solo, the CFI would take the student on a check flight, usually a couple of circuits. On my check ride, at about 300ft the engine stopped suddenly. As I pushed the nose down to land ahead among some trees there was a shout of "I have control" and Les executed a diving turn to port, levelled off and landed downwind on the grass. He was an ex-RAF fighter pilot, Spitfire and Hurricane, I believe. The chances of surviving the procedure in the book, ie landing in the trees, were about 50/50.

For years afterwards I campaigned to have the basic training requirement changed to including teaching and practice about calculating for every take-off, with all the variables of weight, wind, temperature etc,, the height from which the turn can be made safely by a pilot who has been taught the manoeuvre, A letter to Flight magazine headed "The Impossible Turn" saying this started a heated and often acrimonious correspondence, in the early '70s.

When the dogma came into being, nearly every airfield was surrounded by fields offering fairly safe landings. But from WWII onwards this changed so that by the '60s a "straight-ahead crash" would be on housing or otherwise built up areas. However, the reliability of modern engines has reduced the risk of a properly maintained and managed piston engine failing to almost zero, so this is probably an academic discussion.

Unless, of course, you still fly behind an old-fashioned engine like a Cirrus or Gipsy Queen. And if you do, you probably know how and when to make the Impossible Turn, should you need to.

[Local Variation]

Overall……a very successful outcome due the the pilots actions. Let’s face it, plenty of us have misjudged our own practice engine out scenarios.

I find this non-analyzing belief of you must land straight ahead after an engine failure to be a dangerous mindset. Who knows what is straight ahead.

This incident took place at the Old Bridge Airport. Take a look on google earth on the landing options around there……not good. How about turning toward the airport. It seems to have worked out well.

The video is a great example of how a side slip should be used to one’s advantage instead of accepting a long landing(if safe to do so on aircraft type). In fact, it should be planned for as an option on every engine out scenario. In general, aim for one third down the landing location which gives you some margin in case you find yourself low on energy(reduces the odds of not reaching the runway) and the sideslip in if too high.

In this case, a good sideslip would have been useful to prevent a long but otherwise successful landing that was slightly downwind……and a tailwind can easily cause a long landing.

An aggressive sideslip should also be considered for an engine failure on takeoff when some runway is left ahead of you and the options beyond the runway are poor. There may be several variables to consider but on many small aircraft, one can lower the nose, initiate an aggressive sideslip and have a successful landing possibly with partial but relatively low speed runway overrun rather than a relatively high speed touchdown in a much riskier area.

This 100%.

I would also suggest to locate places to put it down in and around your home airfield, as statistically that has a higher rate of probability for location of engine failure.

To demonstrate this, a checkout with the CFI went as follows. Take off to the East, EFATO, leave to the North and go to the training area for PFL and general handling. All as expected, but.....

EFATO fine, climbing away. Through 500ft turning North. At around 900ft, CFI took control and closed the throttle. Engine Failure.

What? Really? Here? Yes really! Is this EFATO # 2 or PFL? Confused.com. Time is ticking and I'm not managing the situation. Response was it doesn't matter you are already low and going down, where are you going? Too far away from the field to return (airport size pattern).

It just so happened a very small field was off the starboard wingtip and that was the only option. And my position was right base for this short narrow field strip descending through 700ft. In their......you must be joking. No in their. And in we went and I would have got in. Years of experience has got me in their.

That was a huge learning and very real. EFATO followed by immediate PFL. Climbing away, through 1500ft, I joked that you're not going to quickly close the throttle again are you? Why not was the response.

Upto that point I hadn't considered engine failure in this area. We normally depart to the West where there is ample space to put it down.

All this bearing in mind that many many years ago, during PPL training we had a full on real engine fail at 600ft right above the M1 one sunny Sunday afternoon. We got it down, yet that experience still didn't stop the startle wtf effect of that checkride.

Continue to practice post PPL. Know your local area intimately. Don't make PFL drills easy for yourself. Learn slideslip and for me, don't practice rigidly to the scripted technique you were taught.

Another CFI with aerobatics showed me how to get it down very quickly if high going in using what I felt as abrupt aggressive slideslip compared to my technique. Fantastic skills and great learning.

[megan]

Might it not be possible that the instructor allowed the student to fly the aircraft with her just keeping a watching brief? Making judgement without the pertinent detail I think is some what foolish.A windmillimg propeller creates a lot more drag than a stopped oneYou're correct Bames. Also, a stopped propeller on a 172 is not going to affect the stall speed.


https://cimg3.ibsrv.net/gimg/pprune.org-vbulletin/1088x315/c_ba3b6585bad972e3e5370e44dd13f769215ab7d6.png

[B2N2]

Lets go a different direction with this, whoever posted the video stated “total engine failure”.
We don’t know that to be correct.
That could have been a partial engine failure with a non responsive engine.
Broken throttle cable, clogged injectors if this was a later model SP, many options.
It the prop was windmilling you’d expect a steeper glide.
It may not have necessarily been the instructor at the controls. If the field was easily made why not let the student gain the full experience and fly?
Why should this have been a spot landing on the opposite threshold?
How many hours did the instructor have on type, make or model?
Last but not least, you don’t get a year older on your birthday you get a day older.
The difference between being a student and an instructor is one flight with an examiner.
Lets not judge too harshly here as we don’t know the experience level.
All turned out well enough.
He who cast the first stone better be without sin.
Nobody bothered to give me a familiarization flight at my first CFI job so first flight, first student, I promptly got lost and spend the majority of the flight teaching basic maneuvers till I came across the airport again.

[Cloud Cutter]

Why are you disagreeing? What I actually stated was "In almost any position the prop stops, there is likely to be disrupted airflow to the wing, hence increased stall speed is a further issue" . This is factually correct. So there is nothing to disagree with. I never compared the drag of a genuine windmilling propeller (ie. driving a completely failed engine which is producing ZERO power whatsoever) to a stationary propeller. However in your example of an engine / propeller at idle, almost certainly the stationary propeller creates more drag, and definitely it increases stall speed if it disrupts airflow over the wing at all, which is almost inevitable.

Regarding your false claim that "And there is absolutely no need to "compensate for increased stall speed"", you are mistaken. Of course a stopped propeller disrupting airflow to the wing will increase the stall speed! Any disruption to airflow to a wing will reduce the lift it produces for any given angle of attack & airspeed combination. Therefore the increased angle of attack required for any given airspeed will be closer to stalling. THAT is the relevant definition of stalling and its relationship to stall speed, as in this example. What alternative "definition of stall speed" were you suggesting I should be checking? Please let us know, I'd love to hear it.

It seems you are confused by this.

To make it very clear and simple for you, take an extreme example which proves the general case: if you progressively disrupt the airflow to let's say 50% of the wing, more, 60%... more , say to 90% of a wing, do you honestly believe the stall characteristics of that wing remain identical to the undisturbed case? You are trying to claim that in all these cases, the wing flies as normal and still stalls at exactly the same airspeed, and that "there is absolutely no need to "compensate for increased stall speed" for any wing with disturbed airflow, which is completely wrong. That is dangerously flawed advice, potentially very dangerous.

As for your further comments " plus the slipstream from produced by a windmilling propeller of an engine running on idle power has zero effect anyway" this is so muddled and unclear as to make zero sense. Whichever way, and whatever you intended to say, trust me, the difference between the flight characteristics with an engine at idle and a stopped propeller are significantly different. For you to claim otherwise proves you have never experience a stopped propeller, unlike some of us who can tell for definite that it does - significantly.

So, disagree all you like, but I recommend you check a few facts and try to understand the physics and fundamentals of stalls and stalling before criticising pilots, flying instructors, who clearly understand aerodynamics rather better than you. Some of the misconceptions you hold are potentially quite dangerous in flight, especially in emergency situations such as total engine failure.

May we enquire your flying instructing experience, and where you claim to find these aeronautical myths from, which you then try to correct flying instructors about, please? But please stop the potentially dangerous claims of absolutely no need to "compensate for increased stall speed" for cases of total engine failure; you could cost people's lives if they make the mistake of believing your myths and misunderstandings.

:rolleyes: pilotmike, I think it's you who's a bit confused, buddy. A stopped prop is almost as good as a feathered prop. A windmilling prop creates negative thrust (i.e. additional drag). No need to compensate for increased stall speed in a 172 with an engine out.

[Heston]

You folk do make me laugh! Talk about over analysis.
Ive had three engine failures in SEPs where I've landed on the runway - one downwind like in the video.
She was more than two miles out for goodness sake. She got back to the runway. She could see she could get it in. So she did.
Bloody well done.
Anything else you want to say about it is needless BS.

[BFSGrad]

I think the error of the topic originator was to evaluate (i.e., “horrible”) an emergency, engine-out landing using routine-landing criteria. As to whether there are to be lessons learned? Of course there are. But don’t offer up the false choice of (1) brilliant, nothing to be learned, or (2) horrible, much to be learned. There’s a third choice: good enough but still plenty to be learned.

A very long time ago during a BFR in a 172, my CFI pulled the power, simulating the standard engine failure. Though within sight of an airport, our altitude was in that gray area where it appeared we were too high for a straight in and too low for a pattern to the opposite direction (crafty CFI, eh?). I chose the straight-in, dropping full flaps and aggressively (rudder at the stop) forward slipping, and the 172 proceeded to drop like a stone. The CFI allowed the simulated emergency to proceed all the way to landing and we touched down at proper landing speed half way down a 5000 ft runway. I thought we were going to overshoot but stuck to my plan given that (simulated) I had no other option.

I was fortunate to have a CFI during my primary flight training that insisted on forward slip proficiency from his students.

[Heston]

I'm sure the participants had plenty to learn. But not us with just what we see on the video (well she should have used the M word on every radio call, as someone else has said).

When this happens for real the thought process goes like this
Damn! How do we get down ok? (pause)Umm ok that's the plan then
(more pause) is this going to work? Yep, still looking ok. Right carry on then and don't mess it up
(Repeat this a few times) wow! We're down and we're alive

Note there is no thought given to whether there's a theoretically better thing to do once you've made your plan. All attention is on making a success of the one you've chosen.
And no worrying about what the video will look like or what those guys on the internet will say.

[FIC101]

I thought his may be of interest

Youtubers are lining-up to say what a hero the pilot was, but It seems to show a very badly handled engine fail within easy reach of a runway. Any comments? Any suggestions on options after she found herself over the threshold and WAY too high and fast? Other than don't come in too high and fast.



If this was a candidate on a PPL skill test I would award a pass because the pilot succesfully concluded the flight without damage or injury and achieved the aim which is to land safely after an engine malfunction. However in the debrief and with the candidates permission, I would have added. From a 2 mile final it would have been possible to consider, I emphasise consider, altering the glide path of the aircraft by
1. Slipping, Cessna warn of elevator oscillation above 20 degrees of flap
2. S turning
3. Diving the height off with flaps full just slower than the flap limiting speed.
Do not consider any of the above unless you have been taught the proper procedures

Its important to declare an emergency using the standard recognised international phraseology, EG Mayday or Pan Pan Pan. A fire truck can only attend the scene if the driver knows of the emergency and making the proper call leaves no doubt about your situation and the need for urgency. Fire is the major concern and being unable to vacate the aircraft without assistance. Seconds count if an aircraft goes on fire after impact

I got the impression that the pilot merely accepted the final glide path without trying to modify it, this is a common mistake. However we do not know the full circumstances and the ground track of the aircraft, my comments therefore are based on an element of supposition

On a FI AOC I would have expressed dissatisfaction that the instructor candidate didn’t employ any of the 3 above methods to bring the touchdown point closer to the landing runway threshold as being a flying instructor, not only should they be able to do this but teach it also. With a tailwind the initial aiming point and final touchdown point becomes more important.

The fact that the emergency wasn’t declared properly by a mayday or pan pan pan call is a very disappointing omission by a flight instructor.

Whether the propeller was windmilling or not is not relevant, the best glide speed gives adequate protection above the stall speed for a safe approach and landing, windmilling or static. Providing the engine hasn’t seized or is restricted the prop should windmill at Vmd anyway.

If there was a handling or speed problem with a seized propeller it would be mentioned in the C172 manual, it isn’t.

[LOMCEVAK]

You folk do make me laugh! Talk about over analysis.
Ive had three engine failures in SEPs where I've landed on the runway - one downwind like in the video.
She was more than two miles out for goodness sake. She got back to the runway. She could see she could get it in. So she did.
Bloody well done.
Anything else you want to say about it is needless BS.
Heston, I think that many reading some of the comments on this thread will learn something, even if the points are not totally relevant to this incident. Let's consider this incident as a trigger for debate.

I have been a witness at an inquest after the front seat pilot died in an attempted forced landing following an engine failure; the instructor lived. There were some witnesses who said that the accident was caused by not formulating a single plan early and sticking to it rather than assessing the situation continuously and adjusting accordingly. I said that I felt strongly that a continuous re-appraisal was the best way to operate but that is a personal opinion, albeit one that has worked for me so far. .

[Heston]

Heston, I think that many reading some of the comments on this thread will learn something, even if the points are not totally relevant to this incident. Let's consider this incident as a trigger for debate.

I have been a witness at an inquest after the front seat pilot died in an attempted forced landing following an engine failure; the instructor lived. There were some witnesses who said that the accident was caused by not formulating a single plan early and sticking to it rather than assessing the situation continuously and adjusting accordingly. I said that I felt strongly that a continuous re-appraisal was the best way to operate but that is a personal opinion, albeit one that has worked for me so far. .
Yes. Good points.
What I meant about the plan and sticking to it was that if it's clearly going to work and as you continue to fly it and appraise it it is still going to work, then you stick with it. What you don't do half way through is think. " I can see now that I should have done something else that might have been better, so I'll change my plan."
Sticking to your original plan even when you can see it's not going to work is not what I meant. You need to change plan. But now you've lost time and have fewer options...
KISS works

[bobward]

When I was training I had a rough running engine on departure from our local airport. Having around ten hours dual at that point I didn't really know enough to be very 'concerned'.
The instructor took over for a minute or two, checking things over, then handed back control to me. We flew a wide circuit (the pattern being over a largish city), with enough height to
be able to land clear. On final we were 500 feet above circuit height: the advice being that we would have enough height to glide in if the engine gave up.

As we rolled out on final we were surprised to see how many fire trucks and ambulances were waiting for us. Apparently the local plan didn't consider the size of the aircraft in trouble,
and just scrambled the lot. A normal landing ensued with no major problems.

What impressed me then, and still does now, is how my instructor assessed the situation and then let me get on with it. I've no doubt that if I'd started to panic he'd have taken over.
Instead it ended up as a huge confidence booster to a newish student. So, if you're reading this Geoff, thanks mate!

For me, having read all your comments above, I think that unless you've been there and done it just congratulate the pilot for what they did. There but for fortune etc.

[Cloud Cutter]

For me, having read all your comments above, I think that unless you've been there and done it just congratulate the pilot for what they did. There but for fortune etc.

Damn right, and I'd just add try not to school everyone else unless you know what you're talking about! It's embarrassing 🤕

[FullWings]

Like others, I think this was a real emergency, handled without damage to aircraft or occupants. Was it perfect? I don’t know but that’s not the point - the outcome was way over on the side of satisfactory.

It looks like a quite heavily forested area, and if I was doing a glide approach for real I would be aiming well into the field, as going off the runway at low speed is a much better outcome than hitting whatever is in the undershoot at flying speed. Yes, there are ways to adjust your glide path one you are *sure* you’re going to make it but given the stress of the situation and the result it’s icing on the cake, really. For those saying they looked a bit fast (groundspeed), they were landing downwind as it seems it was the only option, so they would, wouldn’t they?

Job well done IMHO.

[B2N2]

Let’s not forget one important ingredient: Human Factors.
Doesn’t matter how well you do in training the first time somebody shoots at you in anger changes your perspectives.
Same with the first time your only engine sounds like it’s hacking up a lung.
People deal in different ways when their life is literally dependent on what they do for the next couple minutes.
Some freeze, some stay cool till they get home then fall apart and some just try and stumble their way through it the best they can.
Training is always different from that very first time dealing with the real thing.
Lets face it, most GA proficiency checks are done cookie cutter style, designated practice areas and they do their best to distract you from seeing that really big field under the right wing when they pull the power.
Go around at 500’ because of low flying restrictions and noise and off to the clubhouse they go.
So it’s fairly arrogant to state how good you are in a training environment if you don’t know how difficult the real thing is.
Its like being a black belt in no contact Karate.

[Maoraigh1]

How much runway was left when the aircraft stopped? She might be regularly landing far up the runway. I do so, if told to vacate at the end. If you can land on a 400m runway you can land 400m from the end, using runway markings for your threshold.
Unlike a Pa28 or 38, she could not be sure of flaps after an engine failure as vibration at failure might affect battery connections.
From her voice, there was no hassle. Very impressed.

[RVF750]

I'm lucky enough to have benefited from the David Coulson GFT party trick. it's true, once the prop stops, (and he threw the key in the back!) it really wasn't a great deal like a PFL! I did manage to park it by the clubhouse though as instructed. They don't make them like him any more.

[Heston]

Let’s not forget one important ingredient: Human Factors....

People deal in different ways when their life is literally dependent on what they do for the next couple minutes....

Training is always different from that very first time dealing with the real thing.


Ain't that the truth?

[Big Pistons Forever]

I'

The Auster incident is relevant to the Impossible Turn. The club had a rule that before a first solo, the CFI would take the student on a check flight, usually a couple of circuits. On my check ride, at about 300ft the engine stopped suddenly. As I pushed the nose down to land ahead among some trees there was a shout of "I have control" and Les executed a diving turn to port, levelled off and landed downwind on the grass. He was an ex-RAF fighter pilot, Spitfire and Hurricane, I believe. The chances of surviving the procedure in the book, ie landing in the trees, were about 50/50.
.

The actual accident record for forced landings in trees is almost 100 % survivability if the airplane was under control. The fatal accidents where the airplane hit trees are when the aircraft was not in controlled flight. The low altitude turnback is almost binary. You either make it or you lose control in the turn and the resultant stall spin is almost always fatal. Transport Canada did a study on this issue. They determine that a turn back is 8 times more likely to result in a fatal accident over a glide straight ahead. The key to surviving a light airplane crash is aircraft control. If you hit at gliding speed with the wings level and in a level or slightly nose up attitude you will survive pretty much regardless of what you hit.

I would suggest that this was a well flown emergency and the disparaging comments in some of the posts are out of line. I have 2 comments

1) This is a good example of the value of prefacing all emergency radio calls with Mayday. If she had she would probably not have to have a distracting call to the other airplane

2) I would be vey interested in finding out why the engine failed. Since between 2/3 and 3/4 of all engine failures are directly caused by the actions or in inactions of the pilot, I predict that this was in fact the case in this incident.

[FIC101]

Of course it’s easy to say that this was ‘well done’ as everyone seems to agree but surely the most important thing to consider after every flight is, “what mistakes did I make and how can avoid them next time”. Or, “is there anything I could have done better”? Backslapping is positive and of course more sociably acceptable but it’s not the best way of improving performance, that’s of course if you want to improve your performance!

[henra]

Of course it’s easy to say that this was ‘well done’ as everyone seems to agree but surely the most important thing to consider after every flight is, “what mistakes did I make and how can avoid them next time”. Or, “is there anything I could have done better”? Backslapping is positive and of course more sociably acceptable but it’s not the best way of improving performance, that’s of course if you want to improve your performance!
And this is why many here -after acknowledging the good judgement- suggested that a carefully executed sideslip, after having made sure that sufficient energy is available to reach the runway even if the engine completely quits, would have been the icing on the cake.

[Heston]

But at least there was cake...

[henra]

But at least there was cake...
Absolutely. And a good one.

[double_barrel]

Well. Thanks all. You may be surprised to hear that I don't regret starting this thread, even if it made me look like a prat.

Next time, I would be less willing to criticize, even though criticism does not imply that I think I could have done better. In fact, as soon as I saw the video, I had a nightmare vision of me frozen at the controls, having come in high, seeing the runway rapidly disappearing and not having the brain bandwidth to do anything about it. Discussions like this might help me to visualize sideslipping to save the day. I have used sideslipping, without flaps and early in the approach in practice engine fails, but I don't trust that I would have had the mental ability to pull that trick out of the box with flaps down and 50 feet above the runway.

Thanks!

[Heston]

Well. Thanks all. You may be surprised to hear that I don't regret starting this thread, even if it made me look like a prat.

Next time, I would be less willing to criticize, even though criticism does not imply that I think I could have done better. In fact, as soon as I saw the video, I had a nightmare vision of me frozen at the controls, having come in high, seeing the runway rapidly disappearing and not having the brain bandwidth to do anything about it. Discussions like this might help me to visualize sideslipping to save the day. I have used sideslipping, without flaps and early in the approach in practice engine fails, but I don't trust that I would have had the mental ability to pull that trick out of the box with flaps down and 50 feet above the runway.

Thanks!

Yeah you would do it, trust me. As long as the concept of sideslipping on approach is familiar to you you'd do it. Maybe not with finesse, but you don't need finesse, you need to be safe.

[172_driver]

How about this one - slow below best glide speed to steepen the approach angle!?

Never taught it to my students. But tried it a few times on my own and worked like magic.
Discuss.

[LOMCEVAK]

How about this one - slow below best glide speed to steepen the approach angle!?

Never taught it to my students. But tried it a few times on my own and worked like magic.
Discuss.
As you found out, it works but there are a couple of traps to be wary of. First, your margin from the stall is reduced so if you flare from this speed you may stall. Associated with that, when you flare your speed will reduce and as you are below min drag speed your rate of descent will increase and you can get a heavy landing. However, if at a suitable height you dive to regain the best glide speed before you flare then it can work well, and I suspect that this is what you did? But it can go wrong and result in a heavy landing or stall.

[Pilot DAR]

How about this one - slow below best glide speed to steepen the approach angle!?

No.

My "no" is supported by the fact that this is not an approved training nor operational procedure anywhere. And, as correctly mentioned, it puts the plane is a regime of flight where it will be necessary to accelerate it before it can be safely flared for a landing. Doing this would be similarly unsafe as a prolonged climb at Vx, where there is no obstacle to clear. If the engine stops, you have to just up precious altitude gliding to accelerate to best glide speed (or probably a little faster) so you can successfully flare to arrest your rate of descent. Speed is safety!

A review of the concept of a "height/velocity" or "Avoid" curve for a helicopter, and how that actually applies to an airplane as well will support this understanding.

[Sam Asama]

Doesn’t matter how well you do in training the first time somebody shoots at you in anger changes your perspectives....
...So it’s fairly arrogant to state how good you are in a training environment if you don’t know how difficult the real thing is.
Its like being a black belt in no contact Karate.

Thanks B2N2! The above would be a good wall poster in so many places.

[megan]

Well. Thanks all. You may be surprised to hear that I don't regret starting this thread, even if it made me look like a pratOne thing you ain't db is a prat, raising the subject is a learning exercise in that it generates discussion, it's a bit like the quote "there is no such thing as a stupid question". Although I had military training on the T-34 and T-28 side slipping was not part of repertoire the taught, though it was in my previous civil life. Overshooting badly on a simulated engine failure into a thinly treed paddock one day in the T-28 it didn't even enter my mind to try side slipping, may have got a wrap across the knuckles from the instructor and a lecture on spinning or snap rolls.

[Mogwi]

How about this one - slow below best glide speed to steepen the approach angle!?

Never taught it to my students. But tried it a few times on my own and worked like magic.
Discuss.

This is something that I demonstrate in my current steed of choice (1938 Tiger Moth). It is possible to sit high on base leg at 40kts until the picture/height looks right, then make a dirty dive to Vmd and turn finals. It does require practice and judgement and I prefer to use S turns and aggressive side slip. The only advantage is that it is a less dynamic environment and the touchdown zone can easily be kept in constant view throughout.

Ex-helicopter pilots seem to like it!

Mog

PS Stall is c35kts!

[lsh]

Once the aircraft has let you down - in this case with engine failure - the sole aim thereafter is to preserve life.
The aeroplane surviving intact is a welcome bonus.
It is good to analyse these things - learning takes place.

lsh

[172_driver]

As you found out, it works but there are a couple of traps to be wary of. First, your margin from the stall is reduced so if you flare from this speed you may stall. Associated with that, when you flare your speed will reduce and as you are below min drag speed your rate of descent will increase and you can get a heavy landing. However, if at a suitable height you dive to regain the best glide speed before you flare then it can work well, and I suspect that this is what you did? But it can go wrong and result in a heavy landing or stall.

At say 50 kts and full flaps in a C172, you sit comfortably well above a known stall speed. On the other hand in a full fwd slip with full flaps I am not really sure as to where I've got my airflow limits.
As for the flare, a slow transition back to normal flare speed. Or a seat of the pants flare from a lower speed. Either works if you're one with your airplane. A bad idea probably for a new inexperienced student.

My "no" is supported by the fact that this is not an approved training nor operational procedure anywhere. And, as correctly mentioned, it puts the plane is a regime of flight where it will be necessary to accelerate it before it can be safely flared for a landing.

You're right that I have never worked (or been taught) at any training facility which trains that concept, or even discuss it. Is there such a thing though as "approved training method" or is it just a 'norm' ? Where I am from training facilities are not as tighly regulated as airlines, no school I've been to (US and European) has an authority approved FCOM or SOP. Hence I am wondering if you could call it "approved". If so, by whom?

It is possible to sit high on base leg at 40kts until the picture/height looks right, then make a dirty dive to Vmd and turn finals. It does require practice and judgement and I prefer to use S turns and aggressive side slip.

That's what I quite liked about it, you could just sit there in peace waiting for the "right view". Instead of messing about with a slip, which is dynamic and more demanding. An S-turn similairly, more things to process in your mind at the same time.
Been many years no since I even touched an SEP, so I might not be the best to comment. However, proper energy management is a very rewarding thing in airliner. Maybe the reason why I take good interest in this thread.

[Rozy1]

A lot of talk about slipping.
I’m thinking a forward slip is what’s used to lose energy if high and fast. Is something different taught in the UK or wherever?

[Pilot DAR]

At say 50 kts and full flaps in a C172, you sit comfortably well above a known stall speed

Well, you sit ten knots faster than the POH (172S) speed, so well above...? Above, okay.

I am wondering if you could call it "approved". If so, by whom?

Firstly, the POH (Flight Manual) is FAA approved, and describes the techniques and speeds for flying the airplane. If something you're doing in the plane is different than what the POH says, it's not approved.

I'm less expert at who approves training curriculums, but I'm certain that the national authority does - they won't issue a license to a candidate who has not been recommended against the training standards. Instructors must train students to the curriculum, and not in contravention of the airplane POH. But that's the legality, it's the physics of power idle/off flight in power planes which is more important:

Again, referencing the 172S, yes, you can sit high on the approach, full flaps, descending under control at 50 KIAS, with power idle (or a failed engine) so power is not being considered any more. Cessna tells you that for that phase of flight, you should be flying at 65 KIAS (incidentally, Cessna also tells us that "maximum glide" will be achieved at 68 KIAS - flaps up, I'm sure). I don't have information for full flaps glide, but I'm sure we'll all agree that it's much less distance per altitude than flaps up. So you're going down more steeply, and at a slower airspeed than the POH values. That's okay, as long as you can recover it to a zero rate of descent when you need to. It is a pilot's ultimate goal to arrive back to earth at a zero rate of descent! As you are descending (at a steady rate, we'll presume), you are going to have to accelerate upward from that descent path to momentarily arrest your rate of descent to zero (to prevent impact). Accelerating takes energy, and all the energy you have to work with is airspeed only, as the engine is not available to you for power. So Cessna tells you you should be at 65 KIAS, but you've chosen to fly at 50 KIAS, and stall is at 40 KIAS. When you see the ground getting really close, you're going to pull, to achieve that zero rate of descent which will allow the plane to be reused. Cessna has demonstrated that from 65 KIAS, a pilot of average skill can exchange that 25 knot excess airpseed into a zero RoD before the stall. Oh, by the way, from that steeper descent angle, it will require a greater acceleration upward (G) than normal to flare. Slightly greater G requirement means that stall speed goes up when you pull. Cessna test pilots have learned the same lesson I've learned during flight testing, that the ten knot excess speed above stall on approach is just not enough.

Or... you glide the proper speed as per the POH. If you're too high/fast, slip. You can slip at any speed, modulate it from a little slip to more, and recover in a second, with no change in speed. And, if you're wanting to add drag to get down faster, fly a higher airspeed, drag increases as a square of the speed. And, sideslips are approved in the flight manual, and the training material.

Flying slow approaches, or simply flying slowly at low altitude should make your Spidey senses tingle. Some of the scariest flight testing I have done has been demonstrating a landing from a sudden power loss at 50 feet (a design requirement) from speeds slower than "normal" for the plane (Vy). If you want to safely prove this to yourself, do the following: Climb up into your practice area, at least as high as you'd practice stalls from. Choose a "hard deck" altitude several thousand feet up - a round number altitude will make it easier. Stabilize a slow cruise flight 150 feet higher than that hard deck altitude, at the glide speed and flap setting you'd like to evaluate. Close the throttle rapidly, and enter a glide at your proposed speed. As you approach the hard deck as indicated on your altimeter, pull to arrest your descent momentarily at that altitude, prepared to recover a gentle stall there if it does. Were you able to pause the altimeter pointer at that altitude? If so, it's probably a good speed. If you pulled and stalled, dropping through that altitude, it was too slow, you did not retain enough reserve energy in the plane, to spend arresting the descent before you hit.

From observations I have made during testing, I believe that Cessna's lawyers had a role in choosing the climb and glide speeds for their airplanes - probably Cessna's lawyers have learned the hard way!

[172_driver]

Pilot DAR,

As you mentioned it, I had to check Vso for the Cessna I had in mind - 172R. Vso is 33 kts. Then I checked the 172S. Vso is 40 kts. I thought it was the same airframe with a slightly higher power engine and climb optimised propeller?

As for the rest I am humble to your experience in flight testing. My suggestion of slowing below best glide to steepen the approach angle was not to maintain it until flare. Rather to realise that energy management by speed is another tool in the toolbox. Use it until back on profile, until you've got the right picture back. I have seen some pretty scary forward slips as the pilot doesn't lower the nose to match the increased drag. That manoeuvre in itself introduces some risks.

[FIC101]

Well. Thanks all. You may be surprised to hear that I don't regret starting this thread, even if it made me look like a prat.

Next time, I would be less willing to criticize, even though criticism does not imply that I think I could have done better. In fact, as soon as I saw the video, I had a nightmare vision of me frozen at the controls, having come in high, seeing the runway rapidly disappearing and not having the brain bandwidth to do anything about it. Discussions like this might help me to visualize sideslipping to save the day. I have used sideslipping, without flaps and early in the approach in practice engine fails, but I don't trust that I would have had the mental ability to pull that trick out of the box with flaps down and 50 feet above the runway.

Thanks!

The most important thing DB is what have you learned from the above posts and what would YOU do now you have had the wisdom from others. You may have heard that old saying, There are old pilots and there are bold pilots but there are no old bold pilots. Ask yourself from the advice you have received who do you categorise as potentially the old and the bold. Most of my bold friends, whose attitude I can detect in some of the posts above, never made it to be being old pilots. It’s great to be a hero and and an ace but the safest pilots usually get to come home every night.

[Pilot DAR]

172R. Vso is 33 kts. Then I checked the 172S. Vso is 40 kts

Yes, I agree with you! The POH charts tell us that the 172S is 100 pounds heavier than the 172R. Aside from the weight change, I doubt that the engine and prop affect the stall speed. Interesting though, as stall speeds are accurate in CAS rather than IAS, note that there only 1 knot difference in KCAS stall speeds in that configuration between the two 172's!

I've done lots of stall testing in many models of Cessnas, including lots of mods like STOL kits, floats and external loads, and some AoA system set ups. CAS becomes a pretty important factor, when you're really getting down to the precision of the stall speed. That's why the POH says that KIAS values are approximate.

Rather to realise that energy management by speed is another tool in the toolbox.

Yes, it is. I don't deny that what you suggest works. But, I opine that it's a tool which the approving authorities have decided has a risk to benefit ratio which is not worth it. There things I have found airplanes will do, but probably shouldn't. I have written a number of flight manual supplements for modified planes in which I have restricted or prohibited certain things, because they lacked a suitable margin of safety, and just were not necessary. Often, this was based upon my having done it. An example of this, was that during my flight testing of a C 182Q, which was now equipped with a STOL kit, wing extensions, amphibious floats, and a gross weight increase, among a number of other mods. During testing, I let it get too slow on final approach (like 65 KIAS) power off. I got that really unsettling feeling, added power and sped it up. I then flew a number of intentional power off approaches to establish a suitable glide speed, and settled on 80 KIAS. This is an increase from the 70 KIAS for the original configuration. That speed left a margin for error and average pilot skill. I had to train the new owner in it, and with that glide speed, training went fine.

For myself, I find that if there is to be a judgement error during a forced landing, I'd rather see it to be fast/high than slow/low. As the original video shows us, you're better to go off the end at low speed, than crash short (and maybe out of control) at flight speed. My third forced landing (an EFATO) had me a little fast and high - surprise factor, delayed proper action. I came to a stop in the adjoining field about ten feet from the far end fence with full flaps, nose up elevator and brakes applied. No damage, not my proudest airmanship, but better than tangled in the trees at the approach end - and, should it have not worked out, I could state to the insurance company that I had done exactly what the POH and my training had said to do.

[sagan]

Just a quick note re side slipping Cessna's with full flap.
Had an instructor demonstrate a fairly vigorous side slip in a 150. This was over 35 years ago and was to show me how to 'fix up' a stuffed practice forced landing into some paddock.
Lost control at around 200ft, flick rolled and ended up near enough inverted.
After he recovered and during the awkward flight of shame back home I asked what happened...
'No idea' was the reply....
Later on figured out he stalled the fin. It was nasty.

.

[Pilot DAR]

Lost control at around 200ft, flick rolled and ended up near enough inverted.

:hmm: rolled near inverted at 200 feet in a 150?

[punkalouver]

How about this one - slow below best glide speed to steepen the approach angle!?

Never taught it to my students. But tried it a few times on my own and worked like magic.
Discuss.

I wouldn't recommend this technique as a standard procedure. One need only ask themself how many times have they been doing a practice engine out scenario where they discovered that they were no longer at their best glide speed which they had been targeting. All this because they were busy doing a cause check or busy doing a shutdown procedure or busy assessing how their positioning with their chosen landing area was working out, etc. There are plety of distractions during this procedure and speed is inevitable going to end up off target sometimes. Best to have a fair bit of margin above the stall to account for this.

[Heston]

Posters on this thread seem to me to be about 50/50 split between knowledgeable, helpful folk and Walts/trolls. Folk with a bit of experience can tell the difference, but I do worry about any body else reading it.
ATB

[sablatnic]

Later on figured out he stalled the fin. It was nasty.

.

We lost several photo flying KZ 7s in the 60s for that reason.
You are low and slow, kick the rudder to get a strut out of the photo, the fin stalls and the rudder locks out. On the 7 the only way out of this was a full stall.

[Pilot DAR]

the fin stalls and the rudder locks out

I have no experience, and therefore no comment about the KZ 7. Over the years, and with different flight test programs, I have found that a very few airplanes can be flown to this extreme condition. Certain Cessna 180/185's can get there, particularly as floatplanes. I've done it in a King Air B200, for which it is a know characteristic, and a certification special condition. In the case of these types, recovery can be accomplished with appropriate use of the rudder - it just was not a positively state as other types. But, the rudder did not "lock", or it would not be certified. In both cases, this was powered flight, idle power flight was more benign. The turbine DC-3 will exhibit unfavourable rudder forces with very large rudder deflections, which is alarming. The DC-3 was certified before today's more modern standards - I consider it an exception, for which competent training is pretty important. I have slipped 172's with flaps extended, and experienced the burble in pitch which is warned as an "avoid". Again, manageable within normal pilot skills, as long as you just keep flying it. I have never made any version of a 150 loose positive directional stability, and I have the most experience on them.

During testing of a modified Cessna Grand Caravan last winter, the authority required that I demonstrate a stall to the break from a 75% power climbing 30 degree bank turn in each direction, with full rudder applied in each case. (Yes, this is about a spin entry). The airplane handled it just fine, no rudder lock, benign recovery attitudes.

I find a sideslip to be a very useful tool for descent control, and have done it in many types with no difficulty nor alarm, though no, I would avoid it in a DC-3!

[double_barrel]

... I have slipped 172's with flaps extended, and experienced the burble in pitch which is warned as an "avoid".

Can you elaborate ?

[Pilot DAR]

The position out the wing (the wing station) of the outboard end of the flap corresponds poorly with the outboard end of the horizontal stabilizer. In a slip, the wake off the outboard end of the flap can impinge on the H stab, and blanket part of it, and perhaps induce some elevator motion, which will create unexpected momentary pitch control forces, and some pitching. It's more surprising than a real problem, but it is a thing. It varies with models of the 172, some are worse than others, but it was the cause of the "avoid slips" placard common to most 172's. It's also a thing with C 170B's. It's worthy of understanding, and an imperfection with the design, but it did pass certification, and is manageable. C 150/152 don't suffer, as their flaps don't reach as far out the wing. 18x don't seem bothered by it (I've tried all of them!).

[punkalouver]

Posters on this thread seem to me to be about 50/50 split between knowledgeable, helpful folk and Walts/trolls. Folk with a bit of experience can tell the difference, but I do worry about any body else reading it.
ATB
Why don’t you assist the people you worry about by telling them who the trolls are.



Well back in this thread, I mentioned the potential importance of using a slip(yes it is a forward slip) when appropriate..

I was well aware that there are occasional rare cases of aircraft types that one wants to avoid using this procedure(such as the C170B with ‘barn door’ flaps), a type I used to fly. That is why I stated in that post “if safe to do so in aircraft type”, which in my opinion would be most of the light single engine propeller types(and the 767-200 for those who know the story).

You may have to dig around to find out how a particular type behaves. A type club can be very useful as that is where I learned about C170B handling characteristics in a slip, which can be deadly due to stalling the horizontal stab.

[double_barrel]

The position out the wing (the wing station) of the outboard end of the flap corresponds poorly with the outboard end of the horizontal stabilizer. In a slip, the wake off the outboard end of the flap can impinge on the H stab, and blanket part of it, and perhaps induce some elevator motion, which will create unexpected momentary pitch control forces, and some pitching. It's more surprising than a real problem, but it is a thing. It varies with models of the 172, some are worse than others, but it was the cause of the "avoid slips" placard common to most 172's. It's also a thing with C 170B's. It's worthy of understanding, and an imperfection with the design, but it did pass certification, and is manageable. C 150/152 don't suffer, as their flaps don't reach as far out the wing. 18x don't seem bothered by it (I've tried all of them!).

Ah. Thanks. It's good to finally have an explanation for that placard and a warning of what to expect if it's ignored.

[old,not bold]

I seem to remember that a C152 would go down like a lift with full flap, IAS about 5 KT above full flap stall speed, idle power, and side-slipped as hard as possible. Total control was retained throughout. I have no idea what the rate or angle of descent was, but it seemed very steep indeed, especially with a good headwind.

[Rozy1]

Just a quick note re side slipping Cessna's with full flap.
Had an instructor demonstrate a fairly vigorous side slip in a 150. This was over 35 years ago and was to show me how to 'fix up' a stuffed practice forced landing into some paddock.
Lost control at around 200ft, flick rolled and ended up near enough inverted.
After he recovered and during the awkward flight of shame back home I asked what happened...
'No idea' was the reply....
Later on figured out he stalled the fin. It was nasty.

.
I’m thinking the instructor showed you a forward slip.


https://cimg0.ibsrv.net/gimg/pprune.org-vbulletin/2000x1124/629c9b4e_64f3_419f_85f9_740233a75b60_5d66201e0b461dd26133c82 66ad02bcbc98325ba.png

[Maoraigh1]

From the handling, I see side and forward slip as just names. I got my PPL on an aircraft without flaps or airbrakes. Most of my flying has been on an aircraft with airbrakes, not flaps. I can stop a slip without taking my hand off the throttle, so I seldom used the airbrakes. Only recently did I encounter the term "forward slip".
The distinction is like that between "Stop:sign-braking" and "Red-light-braking" which I don't think driving instructor has ever taught. :)

[excrab]

I’m thinking the instructor showed you a forward slip.


https://cimg0.ibsrv.net/gimg/pprune.org-vbulletin/2000x1124/629c9b4e_64f3_419f_85f9_740233a75b60_5d66201e0b461dd26133c82 66ad02bcbc98325ba.png
is there a difference ? All the aircraft and its fin knows is the relative airflow, which in both diagrams would be 180 degrees to the flight path, and have the same effect on the aircraft, except one is from the left and one from the right. The path over the ground is irrelevant to aerodynamics.

[Rozy1]

Yes, there is a difference! Can you not see the picture?

Hint- look at the ground path and the angle between said ground path and the leading edge of the wing.

[FIC101]

Sitting at 10 knots above the stall on the approach? Your operating outside the normal envelope of the aircrafts operation, it’s called Loss of Control
( I)

And this is why many here -after acknowledging the good judgement- suggested that a carefully executed sideslip, after having made sure that sufficient energy is available to reach the runway even if the engine completely quits, would have been the icing on the cake.

Slipping is only one option. S Turns and diving the height off are two other ways of varying the glide path and should be easily accomplished by any FI.

[megan]

Had an instructor demonstrate a fairly vigorous side slip in a 150. This was over 35 years ago and was to show me how to 'fix up' a stuffed practice forced landing into some paddock.
Lost control at around 200ft, flick rolled and ended up near enough inverted.
After he recovered and during the awkward flight of shame back home I asked what happened...
'No idea' was the reply....
Later on figured out he stalled the fin. It was nasty.Rather than stalling the fin I'd suggest you got too slow and stalled, where upon the aircraft snap rolled., An instructor with student in similar circumstances in a 152 said recovery took 500'.

One author has said in a typical Cessna 152/172/182, depending on the amount of slip, the airspeed can easily be off by 20%, which means the energy is off by 40%. This is enough to cause real trouble. Location of the static source induces errors.

[Rozy1]

From the handling, I see side and forward slip as just names. I got my PPL on an aircraft without flaps or airbrakes. Most of my flying has been on an aircraft with airbrakes, not flaps. I can stop a slip without taking my hand off the throttle, so I seldom used the airbrakes. Only recently did I encounter the term "forward slip".
The distinction is like that between "Stop:sign-braking" and "Red-light-braking" which I don't think driving instructor has ever taught. :)


Yes they are names, but there is a difference. I think most people, even pilots, intuitively think of the slip as a side slip because the side of the airplane is headed towards the runway, not the spinner/longitudinal axis. Just my guess as to why so many get it backwards.

A lot in aviation is taught incorrectly. Like two molecules leaving the leading edge, then because of a rendezvous they have set up at the trailing edge, the one on the top of the wing goes faster. I have heard lift described thusly from more pilots than I care to admit.

[visibility3miles]

A miss is as good as a mile.

Any landing you can walk away from is a good landing.

Any landing that you can fly away from is a great landing.

Nobody panicked even if they didn’t nail the landing.

Once you become a glider, your options are limited, and although all private pilots train for engine out emergencies, it’s hard to get over the instinct that altitude is good.

Once upon a time, a man spun in and landed his single engine plane inverted in a field, with his family onboard, near where I lived because he thought that it was better to press on regardless at the edge of an approaching hurricane rather than sit it out and await better weather the following day.

The plane looked pretty good, aside from being upside down and somewhat crunched. No survivors.

[visibility3miles]

Forward slip vs side slip versus crab landing…

If you land with your landing gear at an angle to the runway, you risk the sideways force collapsing them under the plane.

Always best to land with the plane aligned with the runway.

I have landed with strong steady crosswinds in a forward slip on approach according to the above diagram, which I was told was a crab landing, then switched to a side slip in order to keep the landing wheels aligned directly with the runway, albeit with plenty of rudder which meant that the upwind wheel touched down first, and the other main touching down second when speed/lift dropped sufficiently.

I have also done S turns on approach if I wanted to burn off speed/time/landing distance, but only when there was another plane ahead of me on the runway/approach.

Yes, this pair could have done S turns/weave back and forth to burn off speed/distance, but they may not have had the time/leisure to think it through and it may not have reduced their altitude fast enough.

[visibility3miles]

Also, in terms of “slips” when you are not trying to land…

If you want to go from point A to point B in a crosswind, you will be pointing into the wind in order to maintain heading to your destination, so you will be flying “sideways” relative” to the ground.

It reduces your net speed over the ground, which increases your fuel consumption for a given flight, but otherwise crosswinds are only a major problem when you try to land.

Hat, coat, door…

[Rozy1]

Wind correction angle is not a slip.

[megan]

If something you're doing in the plane is different than what the POH says, it's not approvedGood advice from DAR. Cessna 172H POH - Slips are prohibited in full flap approaches because of a downward pitch encountered under certain combinations of airspeed and sideslip angle. (Presumably 30° is OK as full flap is 40°)

172S on the other hand says - Steep slips should be avoided with flap settings greater than 20° due to a slight tendency for the elevator to oscillate under certain combinations of airspeed, sideslip angle, and center of gravity loadings.

Why? Quote from a DAR post elsewhere, source "Cessna, Wings for the World" by Cessna test pilot William Thompson.With the advent of large slotted flaps in the C-170, C-180, and C-172 we encountered a nose down pitch in forward slips with the wing flaps deflected. In some cases it was severe enough to lift the pilot against his seatbelt if he was slow in checking the motion. For this reason a caution note was added in most of the owner's manuals under "landings" reading "slips should be avoided with flap settings greater than 30(degrees) due to a downward pitch encountered under certain combinations of airspeed, sideslip angle, and center of gravity loadings"......Although not stated in the owner's manuals, we privately encouraged flight instructors to explore these effects at high altitude, and to pass the information to their students.......When the larger dorsal fin was adopted on the 1972 C-172L, this sideslip pitch phenomenon was eliminated, but the cautionary placard was retained.So if you fly an A to K model 172 you could be in for a surprise.

Difference in dorsal fin.

172K
https://cimg1.ibsrv.net/gimg/pprune.org-vbulletin/1024x613/c_5dc8ba1633ce498fb8273922391ba07782aedcd1.jpg

172L
https://cimg3.ibsrv.net/gimg/pprune.org-vbulletin/750x536/c1_98c844651f2d5d70112ddcf621ed199fed0eccfe.jpg

[double_barrel]

One author has said in a typical Cessna 152/172/182, depending on the amount of slip, the airspeed can easily be off by 20%, which means the energy is off by 40%. This is enough to cause real trouble. Location of the static source induces errors.

Does it follow that it's more conservative to side-slip to the right if your static port is on the left of the aircraft? ie presenting the static port to the airstream will result in the IAS being lowered rather than raised ?

[Piper.Classique]

Doesn't the Cessna single engine fleet have a static port each side?
Also there are reasons to slip one way or another, wind direction, direction of engine rotation for example. The trick is to "ahem" use the correct attitude for the airspeed you want.

[megan]

Doesn't the Cessna single engine fleet have a static port each sideThe ones I'm aware of have only a single port on the left side.

db, with the Cessna and its left side static port I'd expect that a slip to the left would have the port seeing increased pressure, slip to the right reduced pressure. The question then becomes what does the pitot see? An academic paper says,When the inclination of the flow exceeds about 15-20 degrees, significant errors will result due to the friction and boundary layer separation effects that occur. In these situations, the pressures sensed at the Pitot-static tube ports do not represent the desired stagnation pressure and static pressure. This is due to the fact that the Pitot-static probe is not a directional device, and so in unknown flow situations, a departure from the ideal uni-directional flow can result in very significant errors—errors which may be unknown to the observer due to lack of knowledge of the true flow direction.The summation of all the effects you need to become a test pilot.

[Pilot DAR]

Cessna 150/152's have the static port on the left fuselage side only. All other Cessna's I'm aware of have at least two static ports, left and right, interconnected. Newer Cessnas with G1000 have four static ports. Any flying you do which causes an angle off approaching 20 degrees for the pitot tube or static port introduce noticeable errors. Interconnected static ports greatly reduce the effect on the static side of the instruments. Very specialized or swiveling pitot tubes reduce this effect for airspeed readings, but are generally not worth the trouble and expense.


https://cimg4.ibsrv.net/gimg/pprune.org-vbulletin/800x600/swivelling_pitot_1_1179313fc45d1f9416ea371ed4b1d741770fe3fa. jpg

[mikehallam]

Quite apart from discussing what the pitot 'sees' when side slipping and what forward speed pressure sensing it feeds to the ASI.compared to actual speed (during a sideway slip).
{I have my own pet theoriy !]

[Prop swinger]

Yes, there is a difference! Can you not see the picture?

Hint- look at the ground path and the angle between said ground path and the leading edge of the wing.
Sorry, but differentiating between forward slip & side slip is meaningless; even when forward slipping I'll aim to track towards a particular ground feature. Your diagram above is deliberately deceptive, the forward slip omits any wind effect & is clearly right rudder, left wing down, the side slip is left rudder, right wing down. What does the diagram mean by "flight path"? The forward slip part suggests that "flight path" = "heading before applying the rudder" but if we apply that definition to the side slip part then the heading before applying the rudder would be directly into wind, in which case the ground track/path would also be directly into wind. Adding some left rudder and right wing down won't change that. That is a very, very poor diagram.

Lets imagine I'm flying towards an airfield, there's a crosswind from the left so I have adjusted my heading so that my ground track is straight torwards my destination. When I start my descent I realise that I have left it too late & will be too high so I decide to add some extra drag by feeding in some right rudder, using left wing down to maintain my track towards the airfield. This is what you would call a forward slip. Fortunately the runway in use is aligned with my direction of travel, my descending forward slip is taking me down the extended centreline of the runway. It's a quiet airfield, I make the usual radio calls announcing I'll be joining straight in on to final approach & continue my right rudder, left wing down flight all the way down final, through the roundout & hold off until touchdown.

At what point did the forward slip magically transform into a side slip?

[Rozy1]

Sorry, but differentiating between forward slip & side slip is meaningless; even when forward slipping I'll aim to track towards a particular ground feature. Your diagram above is deliberately deceptive, the forward slip omits any wind effect & is clearly right rudder, left wing down, the side slip is left rudder, right wing down. What does the diagram mean by "flight path"? The forward slip part suggests that "flight path" = "heading before applying the rudder" but if we apply that definition to the side slip part then the heading before applying the rudder would be directly into wind, in which case the ground track/path would also be directly into wind. Adding some left rudder and right wing down won't change that. That is a very, very poor diagram.

Lets imagine I'm flying towards an airfield, there's a crosswind from the left so I have adjusted my heading so that my ground track is straight torwards my destination. When I start my descent I realise that I have left it too late & will be too high so I decide to add some extra drag by feeding in some right rudder, using left wing down to maintain my track towards the airfield. This is what you would call a forward slip. Fortunately the runway in use is aligned with my direction of travel, my descending forward slip is taking me down the extended centreline of the runway. It's a quiet airfield, I make the usual radio calls announcing I'll be joining straight in on to final approach & continue my right rudder, left wing down flight all the way down final, through the roundout & hold off until touchdown.

At what point did the forward slip magically transform into a side slip?

That is not my diagram. Prove your point with documentation.

I am not arguing that in both you don’t cross control the same way. They do serve two different purposes and are semantically different, otherwise there wouldn’t be two different names. If you can’t understand this I don’t know what to say.

Deliberately deceptive? Seriously?

Maybe the FAA’s diagram is better:

https://cimg8.ibsrv.net/gimg/pprune.org-vbulletin/2000x1504/3ba7e776_cb82_4f65_932d_f6c580426559_08112a0f5e993c6e8267e01 80d585ff692ddaea3.png
https://cimg2.ibsrv.net/gimg/pprune.org-vbulletin/2000x1504/39914aa2_b65a_4d61_96a7_48abaaa7fd35_aa9a1397082e7536187caf5 7ac368fe7619a1fb9.png

https://cimg3.ibsrv.net/gimg/pprune.org-vbulletin/1616x1155/3c1d4b1e_2e10_4254_b641_3c1c817d89fe_153c901538196de9d4f646b 2b10f05c395d73b46.jpeg

[20driver]

I have landed at Old Bridge a few times and like a lot of airports in NJ there are tall trees around. The trees get taller every year and the neighbors can object to getting them cut down so the impact can creep up on you. The tree line can also create some interesting wind patterns. Where I was based at Somerset it could be tricky when landing on 12. That end of the runway was in a box canyon of trees and the wind made a vortex. As you came over the trees the wind was often very different than the wind sock at mid field.
The result was keeping a bit high and fast on a long final was a good idea. I did my PPL in a 172 based in the area and was always shown to use S turns to bleed off speed and I did so frequently. It worked very well. Keep the nose pushed down and watch the runway picture. We did practice some slipping as well but I can't remember any limits on flaps. I do remember it was a very effective way to dump altitude in a hurry. It felt uncomfortable the first few times. A good skill to practice.
I can't find if it says how far from the airport and what height they were at when the engine quit. Does anyone know?
Was the plane based there?

[Fly-by-Wife]

From the FAA airplane flying handbook: A sideslip is entered by lowering a wing and applying just enough opposite rudder to prevent a turn.
From the FAA airplane flying handbook:In a forward slip, ... the wing on one side is lowered by use of the ailerons. Simultaneously, sufficient opposite rudder is used to yaw the airplane’s nose in the opposite direction such that the airplane remains on its original flightpath.

Technically, there is no difference between a forward slip and a sideslip, in that they both require crossed controls. However, the purpose of each is different, in that the intention of the forward slip is to lose altitude without increasing airspeed while maintaining ground track and flightpath, even though the nose of the aircraft will no longer point in the direction of the flightpath, while the intention of the sideslip is to maintain aircraft heading and flight path, relying on a countering crosswind to maintain ground track - essential in landing to ensure that the nose is pointing straight down the runway, i.e. aircraft heading is aligned with flightpath to avoid drift and lateral loading on the undercarriage.

This is the "wing down" method of crosswind landing, as opposed to the "crab" method, where there is no crossed control, and the nose is pointed into wind so that the ground track is aligned with the runway - with the nose yawed to align with the runway just before touchdown. I've always been a crab man myself, but I'm a Cancerian, so it was written in the stars. ;)

[jonkster]

From the FAA airplane flying handbook:
From the FAA airplane flying handbook:

Technically, there is no difference between a forward slip and a sideslip, in that they both require crossed controls. However, the purpose of each is different, in that the intention of the forward slip is to lose altitude without increasing airspeed while maintaining ground track and flightpath, even though the nose of the aircraft will no longer point in the direction of the flightpath, while the intention of the sideslip is to maintain aircraft heading and flight path, relying on a countering crosswind to maintain ground track - essential in landing to ensure that the nose is pointing straight down the runway, i.e. aircraft heading is aligned with flightpath to avoid drift and lateral loading on the undercarriage.

so what do you call it if you are high on final and are crabbing to maintain centreline and then decide to enter a sideslip to drop some excess height and in doing so align the aircraft's nose parallel to the centreline? a side forward slip maybe? :)

It is probably just me but I struggle to see the need to give a sideslip 2 different names when it is the same manoeuvre with identical control inputs. You can use it to lose height without speed or lose speed without gaining height or to assist an observer look out the window or whatever.

[Pilot DAR]

It is probably just me but I struggle to see the need to give a sideslip 2 different names when it is the same manoeuvre with identical control inputs. You can use it to lose height without speed or lose speed without gaining height or to assist an observer look out the window or whatever.

It's not just you, me too! I want to go there, but will cross control it and point it over there for a time, to best achieve that. The arrows and terms are of less consequence, if it was safe, and worked as intended!

[megan]

Cessna 150/152's have the static port on the left fuselage side only. All other Cessna's I'm aware of have at least two static ports, left and right, interconnectedA check of the manuals I have 150, 152, 172 have single port, 182, 206, 210, 207 have dual. With the plethora of versions of a particular model Cessna built it would pay to check the particular aircraft you're about to hire.

[172_driver]

A check of the manuals I have 150, 152, 172 have single port,

Too easy. Quite sure the Cutlass (172RG) has two ports ;)

[double_barrel]

The 172M I fly has one, on the left. Which is why I was speculating that pointing the nose right of track might lead to reduced IAS due to increased static pressure, while perhaps the pitot would be less sensitive to direction. Although of course I'm sure it's not as simple as that and I would be foolish to do anything other than be aware the IAS will have increased error in a slip.

(just musing, just a thought experiment. Please don't haul me over the coals for inventing my own POH)

[Pilot DAR]

I'm sure it's not as simple as that and I would be foolish to do anything other than be aware the IAS will have increased error in a slip.

True, but still wise of you DB. I stand corrected that some 172's have only one port, and your observation, and reason for awareness are wise. That being said, when I slip, which is often, I'll fly with a reserve of speed anyway, so a possible position error will be less significant.

[mikehallam]

How much "extra speed" then ?
And surely being a test pilot you'd have already checked at safe height various non straght ahead slow flight ASI readings to determine if your guess is near the mark or even valid ?
And what about the sideways air across the forward facing pitot effects ??

[Prop swinger]

That is not my diagram. Prove your point with documentation.

I am not arguing that in both you don’t cross control the same way. They do serve two different purposes and are semantically different, otherwise there wouldn’t be two different names. If you can’t understand this I don’t know what to say.

Deliberately deceptive? Seriously?

Maybe the FAA’s diagram is better:
No, it isn't. It is just as hilariously deliberately deceptive as your previous diagram. In order to induce an artificial difference between the two supposedly different slips the FAA diagram omits the crosswind in the second picture and therefore has the aircraft flying an entirely different heading before slipping.

The FAA's fig 9-13 must have a crosswind from the left. That is the only way that the aircraft can be flying into the relative wind, ie direction of flight through the air, and still be tracking down the runway. In co-ordinated flight the aircraft heading would be directly into the relative wind, the pilot then feeds in some right rudder and left wing down and the heading is now aligned with the track over the ground. Fig 9-14 deliberately omits any crosswind, in order to track down the runway the aircraft is flying down the runway. If the crosswind implicit in fig 9-13 was added to fig 9-14 then to track down the runway the aircraft would have to fly slightly into wind to compensate for the crosswind, in other words the airflow/relative wind would come from the left of the runway, as in fig 9-13. When the pilot adds some right rudder and left wing down to 'forward' slip fig 9-14 would look identical to fig 9-13.

To put it bluntly, the difference between the two images in the FAA handbook is not that the aircraft is flying two distinct, different manoeuvres but that one image includes the effect of a crosswind, the other image does not. That's it. They are only semantically different because someone chooses to make them so, it reminds me of the asinine distinction between gliders and sailplanes that some US glider pilots like to make. If you want to carry on making the distinction, help yourself, but don't come on to an international forum and start lecturing people "that's not a sideslip, that's a forward slip" and expect not to be laughed at.

[Pilot DAR]

How much "extra speed" then ?

Qualitative, rather than quantitative. I'm certainly not slipping to fly slowly, so if the slip is achieving what I want it to, that's good enough for me.

checked at safe height various non straght ahead slow flight ASI readings

The safe height for this is desk height, before flight, as it's a review of the flight manual position error correction table, for the intended speeds - but knowing that if the airplane has any aerodynamic modifications, the position error correction table in the original flight manual is probably no longer correct. Once you're airborne, there is no way to know the difference IAS to CAS unless the aircraft is instrumented for it.

Yes, I have tested a number of aircraft with the swiveling pitot static head (photo posted earlier in this thread). That is one of the few ways to gather position error data for an aircraft. On my 150, I was able to measure IAS to CAS errors as much as 19 MPH in high AoA and slips. I've used it on a number of modified aircraft. It's particularly useful on helicopters during autorotation, where there is no other means to determine position error. There's also a GPS method, usable in precise level flight, but hardly useful in high AoA, or power idle flight.

[mikehallam]

Thank you DAR,

But what is your experience/opinion on slow slipping finals ASI when the PITOT has the airstream skiddig partially sideways acrtoss it. And as a corollary what that means for wing lift at that configuaration & velocity ?

[Pilot DAR]

My experience has been that I have done full pedal slips to a first wheel touchdown on several types. This results in an angry tire screeching down the tarmac, unless you do it to wet grass, or better yet, ice. I will consider IAS as I do this, and allow IAS to decay as I flare, considering the possibility of a wing drop. But if you're 6 inches off the surface, a wing drop is less critical, it's just an uneven landing. That said, I do not promote slipping an airplane into the flare, unless you're really familiar with how that type stalls in the slip. I've done a lot of that testing too, as it is considered "spin resistance" testing. That is a compromise with the Flight Test department to not have to demonstrate fully developed spins for a modified plane (particularly external loads). Spinning a Cessna floatplane with a canoe tied to the float struts is un nerving!

I have never flown a plane that I would not slip, though I have flown a few where I would not be keen to slip to really high angles (DC-3/King Air B200). Other types (C 150/PA-18 the most forgiving) I would happily fully slip as needed.

[jonkster]

For most light GA aircraft, where you would use slip to steepen a glide (eg in a glide situation posed by the original video), I would think you would not need to be particularly concerned by airspeed inaccuracies.

If the slip is being used to steepen a glide approach, so as to hit an aim point, surely you would not be trying to maintain a set glide speed, More likely, if high on approach, I suspect you would be pushing the stick forward rather than pulling back and not be worried much about what the ASI was saying, rather you would be trying to avoid overshooting the aim point.

And if you were pulling back - say to avoid undershooting the aim point - you probably would not be using sideslip.

In that situation ASI inaccuracies due position errors, would seem to me to be of small import.

my 2c

[Rozy1]

No, it isn't. It is just as hilariously deliberately deceptive as your previous diagram. In order to induce an artificial difference between the two supposedly different slips the FAA diagram omits the crosswind in the second picture and therefore has the aircraft flying an entirely different heading before slipping.

The FAA's fig 9-13 must have a crosswind from the left. That is the only way that the aircraft can be flying into the relative wind, ie direction of flight through the air, and still be tracking down the runway. In co-ordinated flight the aircraft heading would be directly into the relative wind, the pilot then feeds in some right rudder and left wing down and the heading is now aligned with the track over the ground. Fig 9-14 deliberately omits any crosswind, in order to track down the runway the aircraft is flying down the runway. If the crosswind implicit in fig 9-13 was added to fig 9-14 then to track down the runway the aircraft would have to fly slightly into wind to compensate for the crosswind, in other words the airflow/relative wind would come from the left of the runway, as in fig 9-13. When the pilot adds some right rudder and left wing down to 'forward' slip fig 9-14 would look identical to fig 9-13.

To put it bluntly, the difference between the two images in the FAA handbook is not that the aircraft is flying two distinct, different manoeuvres but that one image includes the effect of a crosswind, the other image does not. That's it. They are only semantically different because someone chooses to make them so, it reminds me of the asinine distinction between gliders and sailplanes that some US glider pilots like to make. If you want to carry on making the distinction, help yourself, but don't come on to an international forum and start lecturing people "that's not a sideslip, that's a forward slip" and expect not to be laughed at.

I’m not lecturing anyone. Sorry if I hurt your feelings, but you’ll have to take it up with the FAA. They are making the distinction.

The crosswind or lack thereof is the difference. We are in agreement that the maneuver is the same.

Btw, no one’s laughing, and you have provided nothing from any source to say that the two names are incorrect either. Ease up on the caffeine maybe.

[Flyingmac]

Just read the video comments. 1st prize goes to this one.


https://yt3.ggpht.com/ytc/AKedOLTxAw3NS2z96L163WbUgqW3PgdWP1ZZH3ck7hvo=s88-c-k-c0x00ffffff-no-rj (https://www.youtube.com/channel/UCbVVVJ1Q7BpIkknzNLFYvHw)Ozgrade3 Australia (https://www.youtube.com/channel/UCbVVVJ1Q7BpIkknzNLFYvHw)11 days ago
Sorry people, as a 5000 hr flight instructor I have to strongly disagree. The approach was appalling. To be that high on profile in an aircraft with gobs of drag available from the flaps is very very poor. No side slip or anything used to get on the ground at the 1/3 touchdown aimpoint on the runway is unforgivable. It's easy to achieve if you have the right technique. You can make the Cessna descend like a bag of sand. To be landing that far into the runway, like at the very end is incompetent. I have taught this scanario hundreds of times, both in the Cessna and Warrior which has lots less drag available. I imagne a proficiency check and remedial training with the Chief Instructor of her flying school will be on the cards. This was not well handled in any way

[parkfell]

The tailwind at the surface of 7knots was a significant contributory factor to this deep landing.
If ‘sight angle’ & then ‘shapes’ appearing on the windscreen were used, then the initial 1/3 aiming point would have been achieved, followed by further ‘fine tuning’ to bring the touch point towards the start of the runway. The greater groundspeed & gliding range were ignored. Judicial sideslip was clearly called for.
If however the instructor hasn’t been taught such techniques during the various training courses, it is hardly surprising that this close shave occurs.
Bottom line: Quality training of the potential instructor is absolutely vital. Otherwise, how are their perspective students going to benefit.
Call me old fashioned…

[LOMCEVAK]

I have followed the discussions over sideslipping with great interest. I have been flying for almost 50 years, mainly in the UK, with much of this time being involved in flight test and instruction and I had never before heard the phrase 'forward slip'! So, a few thoughts from my background on these discussions.

'Sideslip' is defined as the angle between the relative airflow and the aircraft's longitudinal axis. The manoeuvres flown on an approach involving the use of sideslip to generate drag are 'steady heading sideslips', a phrase that is used for a specific flight test technique but also is valid in this context. A rudder input generates a sideslip angle and a yaw rate ,and the yaw rate is reduced to zero (ie. a constant or steady heading) by the use of bank angle in the opposite sense to the applied rudder. Note that all of the discussion here is relative to the aircraft as the frame of reference and its motion with respect to the airmass. The flightpath vector of the aircraft can then be resolved with the wind vector to generate a velocity with respect to earth axes ie. where it is tracking over the ground. The pilot can control the path over the ground by varying the rudder input or bank angle in order to turn the aircraft and when the desired track is achieved he can re-establish the sideslip and bank angles to maintain the desired path with zero yaw rate/on a constant heading. Aerodynamically, this is a single case. What has been discussed in many of the earlier posts is just the difference between the frames of reference ie. the air mass or the ground. In my opinion, the use of the phrase 'forward slip' only serves to cause confusion.

[Pilot DAR]

In my opinion, the use of the phrase 'forward slip' only serves to cause confusion.

I agree, and appreciate Lomcevak's good review of the definition.

In my opinion. an airplane flies through air, either straight, or a little sideways. If it's deliberately sideways, it's a slip (or skid). If the air mass, through which the plane is flying is moving relative to the ground, that's a different thing, and doesn't change what the pilot is controlling the airplane to do - it's either flying forward, or being slipped.(flying a little sideways), so just call it a sideslip, and then be assured that the pilot is still flying the plane relative to the surface also and trust that they will compensate for that too!

[punkalouver]

I have followed the discussions over sideslipping with great interest. I have been flying for almost 50 years, mainly in the UK, with much of this time being involved in flight test and instruction and I had never before heard the phrase 'forward slip'! So, a few thoughts from my background on these discussions.

In my opinion, the use of the phrase 'forward slip' only serves to cause confusion.

If you google forward slip aircraft, you will find an explanation of what it is and the difference between a forward slip and a sideslip. Pilots should be familiar with both terms and the difference between them. Admittedly, some posts here(including mine which have now been corrected) used the incorrect terminology(sideslip instead of forward slip).

Here is what the FAA has to say about it(if you scroll down)

Activities, Courses, Seminars & Webinars - ALC_Content - FAA - FAASTeam - FAASafety.gov (https://www.faasafety.gov/gslac/ALC/course_content.aspx?cID=34&sID=164&preview=true)

[Maoraigh1]

If you, an instrument qualified and current, were in the RHS, with a hood on, could you tell if the pilot was doing a side slip or a forward slip?

[jonkster]

Pilots should be familiar with both terms and the difference between them.

I am struggling to see why the terminology is so important.

I had never heard of the term "forward slip" until quite recently and am not getting what extra value making the distinction is.

In fact there are obvious situations where you seem to be doing both!

Just teach people how to sideslip - no need to make it over complicated. It is an easy technique to teach. If people want to give it a different name depending on how the aircraft is oriented to the ground, fine, but what value does it add? How does it help?

Happy to be shown the value if I am missing something - maybe I have been doing it wrong for decades.

[punkalouver]

I am struggling to see why the terminology is so important.

I had never heard of the term "forward slip" until quite recently and am not getting what extra value making the distinction is.

Happy to be shown the value if I am missing something - maybe I have been doing it wrong for decades.

Probably just have not known the proper terminology for the two different maneuvers for decades. No big deal as long as you know the different techniques.

Bottom line for newbies: Be able to perform and do a proper slip if required in the type of scenario that was in the video.

[megan]

Flyingmac, how dare you ;), the guy is an expert, he even tells us so.There was no wind, you can see it on the METAR. Even with a tailwind, applying aileron and opposite rudder while lowing the nose would have made the Cessna decend like a bag of sand tossed out the window. I have 3000 hrs in the PA28 series and about 2000 hrs in C172, 400 hrs in BE76 and PA44. I am a Grade 1 ME IFR instructor (grade 1 is th highest level of instructor rating in Australia). I train other instructors.Trust what I say. I am an expert in the field.The one thing wrong with any attempted analysis of the long landing is we don't know the details, how's this for a scenario, engine failure, instructor knows they can make the field, to instill confidence in the student the instructor allows student to make the force landing, whilst keeping a watching brief as things progress. Though overshooting the desired touch down the instructor is confident in a successful completion. Outcome, student debriefed on how things could have been done better, side slipping, S turning on final, a big pat on the back to restore students perhaps flagging confidence in airborne petrol powered contrivances. Having the opportunity to get things wrong in controlled conditions is one of lifes greatest lessons, after you have the license in hand you have no one to hold the other.

[LOMCEVAK]

If you google forward slip aircraft, you will find an explanation of what it is and the difference between a forward slip and a sideslip. Pilots should be familiar with both terms and the difference between them. Admittedly, some posts here(including mine which have now been corrected) used the incorrect terminology(sideslip instead of forward slip).

Here is what the FAA has to say about it(if you scroll down)

Activities, Courses, Seminars & Webinars - ALC_Content - FAA - FAASTeam - FAASafety.gov (https://www.faasafety.gov/gslac/ALC/course_content.aspx?cID=34&sID=164&preview=true)
I have to say that I think that the FAA document does not explain this very clearly. The two pictures are identical except that they are orientated differently on the page which surely causes confusion to an inquisitive mind. The paper also implies that bank angle is the prime parameter here with rudder then used as required as the secondary input. I believe that when teaching about sideslip (and I use that word in the aerodynamic sense that I defined in a previous post) it is important to stress that rudder is the primary control input and that is what determines the sideslip angle. Lateral control input to vary bank angle is the secondary control input which determines the subsequent turn rate/heading/ground track. In practical terms both inputs are made simultaneously but this emphasis really helps to understand the mechanism. All that is then needed is to understand the manoeuvres where sideslip is used. First, full rudder to generate drag and lose energy. Secondly, in a wing-down crosswind landing to generate a sideslip angle which equals the drift angle such that the aircraft is pointing straight down the runway at touchdown; this will invariably require less than full rudder pedal. Thirdly, in an aircraft with a high pitch attitude on the approach such that the runway and touchdown point cannot be seen sideslip can be used such that the nose is not pointing down the runway on the approach such that the threshold can then be seen. Again, this typically will not require full rudder pedal and the sideslip will be removed before touchdown. As for the term 'forward slip', is this used on both sides of the Atlantic? I think that it is a very ambiguous and meaningless phrase and I wonder why the phrase 'wing down crosswind landing' is not used instead, which is what I and my colleagues have always used and is much clearer?

[FlightDetent]

I am CEE trained. For the old Soviet-realm counties, the training was pretty much unified. Completely identical understanding to what LOMCEVAK posted, not only in the last piece but also higher up.

We called it just slip, to describe the aerodynamical state (ball off-centre). From the handling point, it is a cross-controlled flight.

The FAA seem to build separate names for the different use cases, have two discriminate manoeuvres described in the book. Well, it's 2 use cases after all, so why not. (the quoted description explaining why one is different from the other had me scratch my head until the point of losing interest).

​​​​​

[Pilot DAR]

instructor knows they can make the field, to instill confidence in the student the instructor allows student to make the force landing, whilst keeping a watching brief as things progress.

An excellent point. I've been happy to do this for a student, and certainly the recipient during my life long training. Another aspect is that it's also good "crew resource management" (such as it is with a student as the other crew member). The more experienced pilot can actually do a few other important things, while monitoring, rather than assuming all the workload.

I am a Grade 1 ME IFR instructor (grade 1 is th highest level of instructor rating in Australia). I train other instructors.Trust what I say. I am an expert in the field.

About 45 years ago, I though I was an expert in a tiny, unimportant field of interest. I told someone that. I was wrong, and they promptly told me. I have never used that word to refer to my skills since - because I'm not, I'm still learning, even from people here.

I had a test flight to fly on a club airplane following an unusual repair. Their rules say that I have to take an instructor with me, as they're calling it a checkout flight. No problem... They send a proud ('cause he tells me) Class 1 to ride with me. After I have completed all my testing, and the plane is fine, I ask if there's anything he wants to see for my "checkout". He says, well.... your really have done everything already..... except a practice forced approach. I arrive to the circuit, it's empty, and I announce a practice forced approach over the runway intersections. I run my cause checks, and commit to a landing, as I have a suitable runway. As I slip in around base and final, I announce that I will clear at the intersection (which mean aiming a little further down the runway than would be normal), and that's where I roll off. As I taxi in, he asked "how did you do that!?". I explained. He asked if I'd teach him how to do that. Um, I probably shouldn't, I'm not an instructor, and I don't work here.....

[jonkster]

As for the term 'forward slip', is this used on both sides of the Atlantic?

The first time I heard it on this side of the Pacific was from a student who had been reading US material and promptly got tied in knots trying to demonstrate the difference.

I may be wrong but think it was never used here until the rise of the internet saw more US material become available.

[LOMCEVAK]

The first time I heard it on this side of the Pacific was from a student who had been reading US material and promptly got tied in knots trying to demonstrate the difference.

I may be wrong but think it was never used here until the rise of the internet saw more US material become available.
'Two nations divided by a common language'

[BFSGrad]

I am struggling to see why the terminology is so important.

I had never heard of the term "forward slip" until quite recently and am not getting what extra value making the distinction is.

In fact there are obvious situations where you seem to be doing both!

Just teach people how to sideslip - no need to make it over complicated. It is an easy technique to teach. If people want to give it a different name depending on how the aircraft is oriented to the ground, fine, but what value does it add? How does it help?

Happy to be shown the value if I am missing something - maybe I have been doing it wrong for decades.
Boils down to this for U.S. pilots: forward and side slip are terms used by the FAA. It's in the FAA handbooks and it's in the FAA airman certification standards. These terms are used by U.S CFIs and DPEs. If you want to get an FAA license, you need to speak and understand the FAA language.

[Ridger]

Illuminating thread in many ways. I've taken away two key points:

Practise slipping in case I ever have the luxury of being too high on approach following an engine failure
Carry enough cash to ensure whoever films my efforts doesn't upload the footage anywhere...

[Big Pistons Forever]

If you have an engine failure it is far, far better to be too high than too low. It may not be that obvious that in fact you are not really high at all particularly if there is a wind gradient. This summer I was on approach to the runway in the club glider (PW5) and was sure I was way high without really watching for a definite overshoot (i.e. touch down point moving down in the windshield/canopy). In this case it turned out that after the application of spoiler when I actually started paying attention the touchdown point was going up fast :uhoh:
I ended up fully closing the spoilers to regain the correct approach path. This is essentially equivalent to going to full power on final in a powered airplane....not good. :=

The bottom line is if you are too high you go off the end of the runway or hit something at a relatively low speed. If you are too low you will probably hit something not on the ground and at flying speed greatly increasing you risk of serious injury or death

That being said I encourage all my students to mix things up after they got their license. Traffic permitting try a gliding approach high and close in. Try a long straight in starting the final approach path at cruise speed and slowing down progressively on final, and yes practice slipping, not only could it help you if things go badly but it will improve your crosswind landings.

[Booglebox]

Much better to go into the hedge at the end of the runway at 20kts then into the hedge at the beginning of the runway at 60kts...

[oggers]

Oh, by the way, from that steeper descent angle, it will require a greater acceleration upward (G) than normal to flare. Slightly greater G requirement means that stall speed goes up when you pull. Cessna test pilots have learned the same lesson I've learned during flight testing, that the ten knot excess speed above stall on approach is just not enough.

A steeper descent angle does not require a greater acceleration to flare. The guy is talking about a steeper descent resulting from lower airspeed to begin with and I'm quite sure about this because it's in all the textbooks - centripetal acceleration = v²/r. Therefore, load factor in the flare is closely approximated with the formula 1 + v²/rg. The load factor reduces as a function of v². Or, for the same load factor you can flare lower with a tighter arc.

Note, I am not saying the margin has not been reduced. What I am saying is your explanation is wrong. It does not follow that the steeper descent angle requires “greater upward G”. That is not the problem. The problem is you have less kinetic energy available for the flare, which becomes a limit in the power off case. As the angles are quite small, the energy you are going to use up can be approximated with D x r x approach gradient, where D is the average drag. So increasing the gradient obviously eats into the energy margin. Your load factor results in a shorter radius (and this wins out over the extra induced drag) so you can save some energy (within the limit of CLmax) by increasing load factor. So in one sense, the steeper angle may lead you to increase load factor – assuming you have a margin to begin with - but that is to shorten the radius to save energy. Nonetheless, in the scenario given, of reduced airspeed, the steeper descent angle does not “require greater acceleration upward”. This stands to reason when you simply consider the fact that you have a lower vertical velocity to start with.

FWIW I think 172 driver's suggestion of reducing the airspeed below best glide is a subtle and efficient way of controlling the glide ratio in the engine out scenario. It's one option to get back to the nominal glide path. I would not be messing about with it on short final, nobody is saying is saying you should persist with some low airspeed like 1.1 Vso right into the flare.

[pilotmike]

A steeper descent angle does not require a greater acceleration to flare.Newtonian mechanics teaches from v = a * t , that for a flare performed in a fixed time, the additional acceleration (above standard 1g) is proportional to the vertical speed to be arrested, which in turn is almost exactly proportional to glide angle (because x = sin(x) for small x).

Similarly, if the flare is performed from the same height, then a = v * v / (2 * S) shows that the acceleration goes up as the square of the descent speed - or descent angle, for small angles.

This supports Pilot DAR’s statement that a greater acceleration is required from a steeper glide angle.

[Pilot DAR]

Thanks for the math, it exceeds my math skills. An element for consideration is "...flare performed in a fixed time...". If you're descending at a slower airspeed than recommended for the the airplane, It will slow more quickly as the nose is raised to flare - so the time available to flare will be less. If the pilot is highly skilled, it may work, but it otherwise eats into the margins which most pilots need to do a nice landing. It can be the unexpected slowing in a slightly misjudged flare, which leads the pilot to add a last moment burst of power - if it's available....

The key takeaway is that by gliding at a slower than recommended speed, you are reducing your room for error on several sides at the flare. To achieve an acceptable landing, you'll have to judge your flare altitude with greater precision, as once you begin the flare, you won't have reserve energy to pause it to correct for being too high. And this leads to having to perform the flare all the way through to touchdown as one well judged transition.

The increase in G at flare for a slower than recommended speed is as I said, slight. But, that slight increase one of several elements which result in a reduced margin for error. When you combine reduced margins, the effect is multiplied. On the face of it, if you choose to approach the surface power off with less energy (speed) than recommended, the need for pilot skill increases exponentially. Once you try this non recommended technique at altitude, you'll realize that it's a skill not worth building, when simply flying good power idle approach and landings as recommended is a more appropriate skill to build.

[Pugilistic Animus]

Probably just have not known the proper terminology for the two different maneuvers for decades. No big deal as long as you know the different techniques.

Bottom line for newbies: Be able to perform and do a proper slip if required in the type of scenario that was in the video.

I found that training for slips it is good to have the students go right to the practical slip limit, in order to impart confidence in the maneuver...Of course, it not only works for landing, but side slip can also be used to do an emergency decent for fire or smoke.

[Pilot DAR]

but side slip can also be used to do an emergency decent for fire or smoke.

Not only can be used, is recommended!

[Teddy Robinson]

Gentle reminder from my recollection of Cessna high wing series 150 /172 is that slips with flaps extended were not approved, or perhaps this has changed ?

[Pugilistic Animus]

Quite a while ago I crunched some numbers using very generous speeds and sink rates for demonstrating the impossible turn and the calculations showed numerically that I would still crash
I was trying to find it here on pprune but so far can't...

[Pilot DAR]

Cessna high wing series 150 /172 is that slips with flaps extended were not approved

C150/152 have no restriction regarding slips.

Some earlier 172's have an "avoid slips with flap extended" placard, but it's not unapproved. The 172N is an example. Though it also has an amplified procedure under "Crosswind Landing" which says:

When landing in a strong crosswind, use the minimum flap setting required for the field length. If flap settings greater than 20 (degrees) are used in sideslips with full rudder deflection, some elevator oscillation may be felt at normal approach speeds. However, this does not affect control of the airplane. Although the crab or combination method of drift correction may be used, the wing low method gives the best control. .....

The wing low method would be the beginning of a slidslip.

Other 172 models have notes which vary in this regard, but none prohibit slips with flaps extended, or the plane would not be certifiable. For the 172S, it's a recommended procedure for a wing fire in Emergency Procedures.

All Cessnas can be slipped with the flaps retracted, which is a good starting point if you want down, flaps can be extended later.

[megan]

Some earlier 172's have an "avoid slips with flap extended" placard, but it's not unapproved........Other 172 models have notes which vary in this regard, but none prohibit slips with flaps extended, or the plane would not be certifiableCessna 172H POH - Slips are prohibited in full flap approaches because of a downward pitch encountered under certain combinations of airspeed and sideslip angle.

My guess is this prohibit clause with 40° flap may have been why later models no longer had 40° selectable.

[Pilot DAR]

Yes, Megan, for the 172H, you're right. Though, the note about crosswind landing technique is pretty similar to the one I quoted from the later model 172, so a little inconsistant. That said, the POH for the 172H was written prior to the "GAMA" format (around 1977), where the terminology of "approved", "avoid" and "prohibited" were standardized.

The 172H was certified to the following:

(2) The static lateral stability, as shown by the tendency to raise the low wing in a side-slip, for all flap positions and symmetrical power conditions, shall:
(i) Be positive at the maximum permissible speed.
(ii) Not be negative at a speed equal to 1.2 Vs1.
(3) In straight steady sideslips (unaccelerated forward slips) the aileron and rudder control movements and forces shall increase steadily, but not necessarily in constant proportion, as the angle of sideslip is increased; the rate of increase of the movements and forces shall lie between satisfactory limits up to sideslip angles considered appropriate to the operation of the type. At greater angles, up to that at which the full rudder control is employed or a rudder pedal force of 150 pounds is obtained, the rudder pedal forces shall not reverse and an increased rudder deflection shall produce increased angles of sideslip. Sufficient bank shall accompany sideslipping to indicate adequately any departure from a steady unyawed flight.
(4) Any short period oscillation occurring between stalling speed and maximum permissible speed shall be heavily damped with the primary controls (i)

The present FAA requirement for this reads:

(1) In straight, steady slips at 1.2 VS1 for any landing gear and flap position appropriate to the takeoff, climb, cruise, approach, and landing configurations, and for any symmetrical power conditions up to 50 percent of maximum continuous power, the aileron and rudder control movements and forces must increase steadily, but not necessarily in constant proportion, as the angle of sideslip is increased up to the maximum appropriate to the type of airplane.(2) At larger slip angles, up to the angle at which the full rudder or aileron control is used or a control force limit contained in Sec. 23.143 is reached, the aileron and rudder control movements and forces may not reverse as the angle of sideslip is increased.

(3) Rapid entry into, and recovery from, a maximum sideslip considered appropriate for the airplane may not result in uncontrollable flight characteristics.


I think that this often quoted and discussed "limitation" for certain 172's comes as a result of varying interpretations and phraseology over the decades.

Ultimately, if the model of airplane you're flying says something's "prohibited" it is. Otherwise, "Avoid" is a caution, not a prohibition.

[Pugilistic Animus]

Not only can be used, is recommended!
Lol...yes indeed

[Pugilistic Animus]

Yes they are names, but there is a difference. I think most people, even pilots, intuitively think of the slip as a side slip because the side of the airplane is headed towards the runway, not the spinner/longitudinal axis. Just my guess as to why so many get it backwards.

A lot in aviation is taught incorrectly. Like two molecules leaving the leading edge, then because of a rendezvous they have set up at the trailing edge, the one on the top of the wing goes faster. I have heard lift described thusly from more pilots than I care to admit.

I can guarantee you that's not how I would explain it:E

[double_barrel]

I can guarantee you that's not how I would explain it:E

I'm sorry, but I have to flag-up yet another quote from the brilliant radio 4 series, Cabin Pressure. When Arthur asks how an aircraft stays in the air, Martin tries that explanation:


MARTIN: .... Listen carefully, Arthur. The wing is curved on top but flat on the bottom. When it meets the air, it's split in two. The air that goes over the top has further to go, so it has to go faster to keep up with the air underneath, that reduces pressures above the wing, giving us a lift.
ARTHUR: Ah, fantastic! Thanks, Skipper. I, I totally get it now.
MARTIN: You are welcome.
ARTHUR: Except, why does it have to?
MARTIN: Why does it what what?
ARTHUR: Why does the air on the top have to keep up the air at the bottom? Why don't they just..split up?
DOUGLAS: For the sake of the kids?

[treadigraph]

Speaking of Old Bridge Airport, here's another incident - well, accident actually - from three days ago...

https://youtu.be/46Xt2dbbk8I

[First_Principal]

Speaking of Old Bridge Airport, here's another incident - well, accident actually - from three days ago...


Same machine as the previous video :-(

Interesting software in use to have the camera auto-track the incoming aircraft...

[Rozy1]

I can guarantee you that's not how I would explain it:E
Good on ya mate. You know what you’re doing.

[Pugilistic Animus]

Good on ya mate. You know what you’re doing.
I try, Rozy1, I really try...thank you

[punkalouver]

Speaking of Old Bridge Airport, here's another incident - well, accident actually - from three days ago...

https://youtu.be/46Xt2dbbk8I

I don’t normally pay too much attention(as in try to analyze) student accidents as I just put it down to someone who basically doesn’t know how to fly an airplane.

Once the pilot has met a standard, such as a private licence, I seem to take more interest.

I know……bad attitude on my part and I shouldn’t think that way as there is always something to learn. And not all pilots need a license.

Anyways, I suspect this is a case of the student freezing at the controls with a gross over-reaction of full aft control column input trying to ‘get out of there’.

[FlightDetent]

There was a case of an older graduate from my school when the trajectory looked identical. Terribly with 3 casualties, the pilot's chair slid back resulting in a pull on the yoke and his inability to recover the excess pitch.

[megan]

the pilot's chair slid back resulting in a pull on the yoke and his inability to recover the excess pitchA gotcha on Cessnas and some other types. Make sure the pin is in the hole, used to do so by rocking the seat back and forward.

https://www.atsb.gov.au/publications/investigation_reports/2001/aair/aair200104684/

[punkalouver]

A gotcha on Cessnas and some other types. Make sure the pin is in the hole, used to do so by rocking the seat back and forward.

https://www.atsb.gov.au/publications/investigation_reports/2001/aair/aair200104684/

Correct. I always give an aggressive, multiple push and pulls fore and aft on the seat. I have heard the spring loaded seat locking unit snap in place while doing this.