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.

But at least there was cake...

Absolutely. And a good one.

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.

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.

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.

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

One 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.

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!

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

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.

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?

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.

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?

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

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!

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.

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.

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.

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.

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.

.

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