Glide approaches
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I do a lot of glide approaches where I fly from. Depending on how busy they are, it's regularly advisable to keep a very tight circuit and remain in sight of the control point, 40 degree flaps help a lot.
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Shock cooling' more folk lore!!!!!!!!!!!!!
After a long full throttle climb with the added weight of a glider followed by an instant high speed descent it would be rather foolish to close the throttle in any aircraft but you do not need a placard to remind you of that or do you?
Both clubs I've towed for we run downhill at 2400 RPM and high speed, 120-140 mph in the pawnee. I fly my final with the throttle at idle, and judging by the steepness of the approach of my fellow tow pilots most of them do too. Our engines typically go to TBO, no cracking. One thing that helps them get to TBO is they are flown a boatload.
-- IFMU
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Sorry for resurrecting this thread. But it was a beautiful day today and I finally managed to get over my nerves..
At FL55, class E and a block altitude of 3000" to FL55 assigned by ATC, with an emergency field in sight, with 2000 RPM, carb heat on, fuel pump on, and maintaining 80 knots, I finally decided to pull ICO to see what would really happen. As expected, the prop windmilled. Restoring the mixture got it going almost immediately. Good.
Next test. ICO and then try to stop the prop by reducing airspeed. Deep into the stall, almost spinning, but still a windmilling prop. Restore mixture, climb back to FL55. Good. I now know that the engine will keep windmilling whatever the airspeed, unless there is a massive internal failure or unless I do something really stupid.
Try again. ICO, reduce airspeed to about 60 knots, then pull up into a half-g pushover to get the speed well below Vs without getting into a spin. Finally, the engine stops completely. Stationary prop in-flight. Funny thing is, it did not scare me one bit because there still was a lot of wind noise. Restore speed to about 80 knots, key to start position. Engine roars into life after three or four blades. Perfect.
Back to altitude, now for the real test. ICO, Pull up, half-g pushover to get the prop stopped again. Restore the mixture and now dive to see if the airspeed can get it working again. I lost a good 1500" to get to 140 knots but once I got to 140 knots: one blade, two blades and then the engine roars into life again.
So what did I learn today about the R2160? First, the engine on this particular bird will windmill until the airspeed drops below about 40 knots, well below Vs. Restoring the mixture will almost immediately bring it back to life. Second, a stationary prop only needs a small nudge of the starter button to get it windmilling again. And third, a stopped prop on this bird will need about 140 knots to get going again. That requires a 45 degree or so dive and an altitude loss of about 1500".
Of course in another aircraft the numbers will be different but this greatly boosted my confidence in this aircraft. Particularly because it doesn't have an inverted flight system but we do push negative g's in it regularly.
Haha, it is quite unnerving isn't it? Looking at it, thinking "I'm not supposed to SEE you..."
I went and did a deadstick with our CFI afterwards from overhead the field, and I don't recall that we had any problems getting it to stop? Maybe we pulled back to nearly a stall, I can't recall.
I went and did a deadstick with our CFI afterwards from overhead the field, and I don't recall that we had any problems getting it to stop? Maybe we pulled back to nearly a stall, I can't recall.
Next test. ICO and then try to stop the prop by reducing airspeed. Deep into the stall, almost spinning, but still a windmilling prop. Restore mixture, climb back to FL55. Good. I now know that the engine will keep windmilling whatever the airspeed, unless there is a massive internal failure or unless I do something really stupid.
Try again. ICO, reduce airspeed to about 60 knots, then pull up into a half-g pushover to get the speed well below Vs without getting into a spin. Finally, the engine stops completely. Stationary prop in-flight. Funny thing is, it did not scare me one bit because there still was a lot of wind noise. Restore speed to about 80 knots, key to start position. Engine roars into life after three or four blades. Perfect.
Back to altitude, now for the real test. ICO, Pull up, half-g pushover to get the prop stopped again. Restore the mixture and now dive to see if the airspeed can get it working again. I lost a good 1500" to get to 140 knots but once I got to 140 knots: one blade, two blades and then the engine roars into life again.
So what did I learn today about the R2160? First, the engine on this particular bird will windmill until the airspeed drops below about 40 knots, well below Vs. Restoring the mixture will almost immediately bring it back to life. Second, a stationary prop only needs a small nudge of the starter button to get it windmilling again. And third, a stopped prop on this bird will need about 140 knots to get going again. That requires a 45 degree or so dive and an altitude loss of about 1500".
Of course in another aircraft the numbers will be different but this greatly boosted my confidence in this aircraft. Particularly because it doesn't have an inverted flight system but we do push negative g's in it regularly.
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Of course it all gets a bit worrying when everywhere seems to have 4-6 knots of sink...
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Where's the mystery? 
A stopped prop will cause less drag than a windmilling one. An idleing engine turning the prop will cause less drag than a windmilling or stopped prop. Which ever you are faced with, you simply judge the glide angle it is giving you and fly the approach accordingly. Aircraft engines will windmill unless the speed is bled off sufficient for the tuning force of the air hitting the prop to be overcome by forces acting within the engine to resist motion. Newer engines that are still tight, or ones with higher compression ect will stop at higher airspeed than older or low compression ones. Also prop pitch/diameter will also have an effect. Certainly, if I turn off the ignition off, on my VW it will stop dead! Mind you, my max airspeed is only 70knots
I don't fly glide approaches every time, if I did in my T31 I'd be moaned at every time I went to an airfield other than my home strip. However, I prefer to be within gliding distance of the field if possible and get very peeved at the bomber circuits adopted by some (noise abatement permitting).
SS
A stopped prop will cause less drag than a windmilling one. An idleing engine turning the prop will cause less drag than a windmilling or stopped prop. Which ever you are faced with, you simply judge the glide angle it is giving you and fly the approach accordingly. Aircraft engines will windmill unless the speed is bled off sufficient for the tuning force of the air hitting the prop to be overcome by forces acting within the engine to resist motion. Newer engines that are still tight, or ones with higher compression ect will stop at higher airspeed than older or low compression ones. Also prop pitch/diameter will also have an effect. Certainly, if I turn off the ignition off, on my VW it will stop dead! Mind you, my max airspeed is only 70knots
I don't fly glide approaches every time, if I did in my T31 I'd be moaned at every time I went to an airfield other than my home strip. However, I prefer to be within gliding distance of the field if possible and get very peeved at the bomber circuits adopted by some (noise abatement permitting).
SS
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Here is my humble take on the question:
I would far rather be caught engine off when flying a tighter circuit that was conducive to glide approaches. Someone earlier quoted that 30% of
GA accidents occured on approach and the option to glide it in would be preferable to becoming stuck behind the energy curve.
The flip-side is that flying tighter circuits encourages steeper turns onto final / base leg placing more pressure on inexperienced pilots to overbank in the turn, thus making them succeptable to stall / spin incidents.
The question is, are more accidents caused but these type of errors or by engine incidents on long finals when behind the energy curve?
Any takers?
Best,
Sicknote
I would far rather be caught engine off when flying a tighter circuit that was conducive to glide approaches. Someone earlier quoted that 30% of
GA accidents occured on approach and the option to glide it in would be preferable to becoming stuck behind the energy curve.
The flip-side is that flying tighter circuits encourages steeper turns onto final / base leg placing more pressure on inexperienced pilots to overbank in the turn, thus making them succeptable to stall / spin incidents.
The question is, are more accidents caused but these type of errors or by engine incidents on long finals when behind the energy curve?
Any takers?
Best,
Sicknote
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That's an interesting point Sicknote, and has some merit. However ...
I'd wager that many who are caught in the spin off final turn though, are those used to bigger circuits and then one day (probably under pressure) find themselves having to turn tighter than they're used too and over rudder! A well banked but balanced turn, if flown properly, is far, far safer than being frightened to bank and subconciously trying "will" yourself around the turn and applying that bit too much rudder. Take a slipping turn as an example, you can have bootfuls of out of turn rudder applied, a crazy bank angle and huge amounts of sink ... but you will not stall and spin. If inexperienced pilots were taught to be less frightened of banking, but not allowed to fly out of balance when doing so, there would probably be a reduction in such accidents.
SS
I'd wager that many who are caught in the spin off final turn though, are those used to bigger circuits and then one day (probably under pressure) find themselves having to turn tighter than they're used too and over rudder! A well banked but balanced turn, if flown properly, is far, far safer than being frightened to bank and subconciously trying "will" yourself around the turn and applying that bit too much rudder. Take a slipping turn as an example, you can have bootfuls of out of turn rudder applied, a crazy bank angle and huge amounts of sink ... but you will not stall and spin. If inexperienced pilots were taught to be less frightened of banking, but not allowed to fly out of balance when doing so, there would probably be a reduction in such accidents.
SS
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The BGA instructor's "how to damage yourself spinning" scenario goes:-
a) You're a bit low in the circuit
b) Instead of modifying the circuit you continue to fly your "normal" pattern but subconsciously keep the nose a bit high (= speed decay without a noisy lump on the front of the aircraft)
c) You're now low on the final turn and start worrying about wingtip meeting trees or whatever, so you keep the bank shallow
d) But now you're not getting round the final turn quickly enough so you feed in more rudder
Then insert your final words "Oh f..." as the world rotates
PS The above is only demonstrated at a very safe height. But especially in a Puchacz it certainly gets the pupil's attention!
Ergo: - It ain't steep turns on finals that get you, it's the slow shallow ones!
a) You're a bit low in the circuit
b) Instead of modifying the circuit you continue to fly your "normal" pattern but subconsciously keep the nose a bit high (= speed decay without a noisy lump on the front of the aircraft)
c) You're now low on the final turn and start worrying about wingtip meeting trees or whatever, so you keep the bank shallow
d) But now you're not getting round the final turn quickly enough so you feed in more rudder
Then insert your final words "Oh f..." as the world rotates
PS The above is only demonstrated at a very safe height. But especially in a Puchacz it certainly gets the pupil's attention!
Ergo: - It ain't steep turns on finals that get you, it's the slow shallow ones!
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The BGA instructor's "how to damage yourself spinning" scenario goes:-
a) You're a bit low in the circuit
b) Instead of modifying the circuit you continue to fly your "normal" pattern but subconsciously keep the nose a bit high (= speed decay without a noisy lump on the front of the aircraft)
a) You're a bit low in the circuit
b) Instead of modifying the circuit you continue to fly your "normal" pattern but subconsciously keep the nose a bit high (= speed decay without a noisy lump on the front of the aircraft)
c) You're now low on the final turn and start worrying about wingtip meeting trees or whatever, so you keep the bank shallow
d) But now you're not getting round the final turn quickly enough so you feed in more rudder
Then insert your final words "Oh f..." as the world rotates
PS The above is only demonstrated at a very safe height. But especially in a Puchacz it certainly gets the pupil's attention!
Ergo: - It ain't steep turns on finals that get you, it's the slow shallow ones!
d) But now you're not getting round the final turn quickly enough so you feed in more rudder
Then insert your final words "Oh f..." as the world rotates
PS The above is only demonstrated at a very safe height. But especially in a Puchacz it certainly gets the pupil's attention!
Ergo: - It ain't steep turns on finals that get you, it's the slow shallow ones!
There is also the demo of what happens if you turn without enough airspeed after a winch launch failure that usually gets attention, even in a K21... Especially when the instructor sets it up and says 'you have'.
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I seem to recall it goes something like: Pitch into a steep climb with speed; as the airspeed decays to launch speed, pretend the wire broke, commence a pitch towards horizontal, but not to vigorous.. arrive flat at something significantly underneath regular stall speed, still flying 'cos you're at significantly <1g. Move the stick back to the regular 'level flight' position, commence a turn (no deliberate mis-coordination required)...
.. at which point the world flips and starts rotating
Puch was the first aircraft I spun that the rudder floated onto the stop and stayed there - i.e. required positive recovery rather than releasing the pro-spin controls.
Interestingly I'm currently doing powered aeros in a R2160! Not spun it yet tho..
.. at which point the world flips and starts rotating
Puch was the first aircraft I spun that the rudder floated onto the stop and stayed there - i.e. required positive recovery rather than releasing the pro-spin controls.
Interestingly I'm currently doing powered aeros in a R2160! Not spun it yet tho..
As before stated, it's the shallow turns that subconsciously get "helped" with a bit of rudder that are more likely to get you into an unexpected spin.
I've spent a few hours thermalling the Puch solo close to the stall and have no complaints with its behavior in a steep bank.
But it sure spins easy out of a shallow bank with not much back stick force and a lot of people have gotten killed that way in the Puch.
Spring checks are coming up and I plan to ask for an extra thousand feet or so to see how/if the Puch spins from a 45 degree bank.
Derek Piggott in his books somewhere mentions that a glider won't stall in a 45 degree turn because the elevator does not have the power in the angled airflow to stall the wing. Caveat that in gliders, pilot position, weight, ballast, equipment and other CG factors can yield an a/c that can vary from impossible to stall to one that's precariously close to the stall.
I've spent a few hours thermalling the Puch solo close to the stall and have no complaints with its behavior in a steep bank.
But it sure spins easy out of a shallow bank with not much back stick force and a lot of people have gotten killed that way in the Puch.
Spring checks are coming up and I plan to ask for an extra thousand feet or so to see how/if the Puch spins from a 45 degree bank.
Derek Piggott in his books somewhere mentions that a glider won't stall in a 45 degree turn because the elevator does not have the power in the angled airflow to stall the wing. Caveat that in gliders, pilot position, weight, ballast, equipment and other CG factors can yield an a/c that can vary from impossible to stall to one that's precariously close to the stall.
Last edited by RatherBeFlying; 29th Feb 2008 at 02:06.
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Interestingly I'm currently doing powered aeros in a R2160! Not spun it yet tho..
Spinning the R2160 is entirely conventional. In fact, now that I'm doing aeros in it and finally learning what those footrests are for, I find it very hard to make a nice, clean spin entry. It's as if the elevator runs out of travel before reaching a low enough speed for a nice entry. Particularly when the aircraft is comparatively light: one-up and half fuel. Even when you whack on the rudder it is really hesitating to start the spin.
Once in the spin though it's all conventional: release the pro-spin controls a little after three quarters of a turn and you are out of the spin at exactly one turn. Push to the vertical, hold one second, pull straight and you've got about 110 knots - perfect for the next figure in the sequence.
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I seem to recall it goes something like: Pitch into a steep climb with speed; as the airspeed decays to launch speed, pretend the wire broke, commence a pitch towards horizontal, but not to vigorous.. arrive flat at something significantly underneath regular stall speed, still flying 'cos you're at significantly <1g. Move the stick back to the regular 'level flight' position, commence a turn (no deliberate mis-coordination required)...
.. at which point the world flips and starts rotating
.. at which point the world flips and starts rotating
Last edited by cats_five; 29th Feb 2008 at 09:56. Reason: clarification
no body has mentioned the recent failure of a powered approach at LHR. I know that the big jets need to keep a load of power on because their jet engines don't spool up very quickly from ground idle but it does illustrate the problems that it can lead to.
Still working up to stopping the 503 on my Rans and bringing it in. No chance of a restart while airborne as the pull starter is between the pedals and behind the stick, I can't do it from inside the cockpit even while stationary on the ground. I will find out how much a stopped prop changes the glide slope.
Andrew.
Still working up to stopping the 503 on my Rans and bringing it in. No chance of a restart while airborne as the pull starter is between the pedals and behind the stick, I can't do it from inside the cockpit even while stationary on the ground. I will find out how much a stopped prop changes the glide slope.
Andrew.
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Hmmmm! I'm all for being within gliding range, but I'm not sure I'd apply that to airliners
Different kettle of fish altogether, but it would be interesting to see the captains taking wagers from the first officers as to who could chop power the furthest away and still make the threshold
Look out for slipping 747's or Airbus downwind run's with Chandelle style pull ups to land into wind whilst dumping fuel! Weeeeeeeeeeeeeoooooooooowwwwwwwwww!!!! 
SS
Different kettle of fish altogether, but it would be interesting to see the captains taking wagers from the first officers as to who could chop power the furthest away and still make the threshold
Look out for slipping 747's or Airbus downwind run's with Chandelle style pull ups to land into wind whilst dumping fuel! Weeeeeeeeeeeeeoooooooooowwwwwwwwww!!!! SS
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I heard a story from a BOAC 2nd officer a few (well a lot!) of years ago about him & his Captain discussing the feasibility of landing a VC10 without power. 2nd had then tried it at Khartoum but had had to add lots of thrust to get in. Capt had then gone into Nairobi starting at about 10 grand over the Ngong hills (Nairobi airport is at about 5 grand) and had sucessfully plonked it onto the end of the runway. Don't know if it was true though!
Of course there have been a couple of successful glide approaches from height with airbuses since!
Both a/c sustained some damage I believe, but excellent airmanship. All a question of having speed & height relative to runway.
But if you're low & slow & your 777 engines see fit not to spool up!
p.s. I believe pre-WWII the standard RAF practice was a glide approach, with drinks having to be bought in the mess for anyone having to open up on approach. With the advent of heavier monoplanes the undershoot accident rate got too high & powered approaches were mandated. Can anyone confirm?
Of course there have been a couple of successful glide approaches from height with airbuses since!
Both a/c sustained some damage I believe, but excellent airmanship. All a question of having speed & height relative to runway.
But if you're low & slow & your 777 engines see fit not to spool up!
p.s. I believe pre-WWII the standard RAF practice was a glide approach, with drinks having to be bought in the mess for anyone having to open up on approach. With the advent of heavier monoplanes the undershoot accident rate got too high & powered approaches were mandated. Can anyone confirm?
