Primarily for general aviation discussion, but other aviation topics are also welcome.
By rusty eagle
#1884348
I've only had two engine failures, one on circuit and one on final. In both cases I put the nose down and flew by the feel of a positive airflow then washed off the excess speed on round out.

I appreciate thoughts on this:

If I have a field in sight I want to ensure that I get to it and should fly at best glide angle. When I'm confident that my aiming point halfway into the field can be reached and I'm at base about 1000', I'd want to ensure that I've got enough excess airspeed for any wind gradient or gusts and then fly the approach, side slipping as required.
#1884357
In an engine failure situation you should aim to fly at best glide speed - ie aircraft glides the furthest with least loss of height - because lift/drag ratio is highest. The corresponding speed Vmd should easily have sufficient margin for any wind gusts or turbulence on approach.
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By David Wood
FLYER Club Member  FLYER Club Member
#1884359
rusty eagle wrote:II'd want to ensure that I've got enough excess airspeed for any wind gradient or gusts and then fly the approach, side slipping as required.

Excess airspeed isn't the answer there. Appropriate glide angle (perspective) is. My view is that you should always keep the airspeed to Vmd as Matt suggests for the reasons that he states.
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By Ibra
#1884360
I think there are zillions way to over complicate this but if you nail a sensible speed in 1.2VS-1.4VS region, keeping wing level bellow 300ft and aiming for the best spot you can have into wind while keeping constant aspect, it will do just fine !

You have gusts & wind gradient margins built into your aiming point and approach angle & glide speed, then use flaps & side-slip to burn that excess energy...

I keep min sink vs best glide, MacCready ring with weight & wind...to gliding competitions (goal is to fly it next day, no surprise element) and forced landing training (goal is perfection, no surprise element), in real life the aircraft belong to insurers (goal is to walk away after bang, surprise !)

Of course if 10ft headwind exceeds Vbg, you won't make the field and you won't have gust margins but your ground speed is zero, so who cares :lol:
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By Dodo
FLYER Club Member  FLYER Club Member
#1884361
When the time comes to touchdown in the unprepared, possibly soft and possibly short field that your aircraft has chosen to arrive in, wouldn't you want to be carrying as little excess speed as possible?

(posts crossed with Ibra)
#1884365
Yes, best glide speed.
But don't over-focus on speed. Set the aeroplane up for best glide, and TRIM for it, as your first action. After that an occasional glance at the ASI is good but you're going to be busy doing other stuff, so you don't want to have to spend a lot of mental capacity on keeping the speed right (but nevertheless it does need to be).
If flying a bit faster means your glide is so degraded that you won't make your chosen field then you should have chosen a closer field. You need to be taking decisions that will be as easy as possible to follow through with.
In theory you should fly a bit faster into a head wind and a bit slower in a tail wind, but ignore that because it's too complicated to be part of a forced landing.
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#1884366
MattL wrote:In an engine failure situation you should aim to fly at best glide speed - ie aircraft glides the furthest with least loss of height - because lift/drag ratio is highest. The corresponding speed Vmd should easily have sufficient margin for any wind gusts or turbulence on approach.


In gliders I've encountered curlover from trees/hedges in a strong crosswind which rolled me nearly 30 degrees. I'd been anticipating that and so had quite a margin above best glide, which was very welcome indeed because it gave me more aileron authority to level the wings again. Not sure whether the effect is so bad in a light aircraft, others will know.

If the field is short then ideally you approach at minimum energy to stop before the hedge. But in gusty or turbulent conditions I want more speed for better control. It's a trade off, but hitting the hedge slowly is always better than hitting the ground fast!
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By MichaelP
FLYER Club Member  FLYER Club Member
#1884384
1. Trim for best glide and turn towards your field.

“Always have a field in mind”, or at least somewhere where you have the best chance of not getting hurt.

When gliding for range, increase the speed if gliding into wind. You can reduce the speed when gliding downwind if you know the speed at which you have minimum sink.

Learning to glide is an asset in this situation.
If I remember correctly, we used 45 KIAS in a K13 for minimum sink, hope for a thermal... But when the field was made we increased to 55 KIAS for best penetration.
We always want good penetration!

In the old days, we were taught to turn downwind if we didn’t have a field in mind... I always try to have a field in mind, track it in my brain as the flight proceeds until the next opportunity arises.

If it’s a problem you might sort out, staying in the air is an advantage, so don’t hurry to the ground unless you are on fire.

Running put of fuel is often the cause, nothing more to be done.
A rough running engine might be rectified on one mag or applying the carburettor heat, opening the throttle, and leaning the mixture (unless it’s already a ‘lean cut’).
A broken engine is best shut down. A lost prop blade, or broken crankshaft will need a pitch up, off with the mags, slow down to stop the prop while reducing the g to avoid a stall. Sometimes we do the reverse of lowering the nose in order to keep the engine bolted to the airframe. The nose weight is useful in a glider. (Been there, done that!).

One thing I demonstrate and teach, is to do the reverse thing to your instinct when coming up short of your field, that is to lower the nose and speed up.
Three things.
1. This enables a controlled crash. Be in control through the crash rather than lose control in a stall.
2. You penetrate windshear sooner and end up gliding into a reduced headwind.
3. You may get into surface affect and this increases you float, hop the hedge and maybe you’re lucky.

What I find missing in instruction these days is the importance of “Point of zero movement”, that point that is not shifting in the windscreen, the aiming point and the reference point for your glide attitude.
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#1884413
'Learning to glide is an asset in this situation.
If I remember correctly, we used 45 KIAS in a K13 for minimum sink, hope for a thermal... But when the field was made we increased to 55 KIAS for best penetration.
We always want good penetration!'

That's what I remember from decades ago, flying the draggy Slingsby Swallow. Penetration is vital!
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By Genghis the Engineer
FLYER Club Member  FLYER Club Member
#1884415
Best glide speed is only useful whilst finding a field. Once you're set up on the target field, trimmed at final approach speed is a much better place to be. Of course in some aeroplanes they're about the same anyhow, but not all.

And then aim to use an adjustable constant aspect turn to your target touchdown point, as that will enable corrections to be made whilst maintaining the right trim condition.

G

(Considerably more than 2 engine failures, all but one of them without aircraft damage, plus many years obsessive practice).
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#1884416
The AX2000 microlight had/has a best glide speed of I think 45mph (and the glide performance of a television set) and you needed to increase that by at least 10mph on the approach in order to have enough airflow over the control surfaces to flare properly ;)
Hence it was important to be very sure of your field - because you had to stuff the nose down to get that extra speed.
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