Dumping Height: Why not stall?
Joined: Oct 2003
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From: Canberra Australia
Approach Angle
Anything which increases an aircraft's drag during descent will increase the glide/approach angle.
Angle is determined by the ratio of drag to lift.
Aircraft which land / approach below their minimum drag speed, such as an unflapped delta can readily increase their glide angle by raising the nose to increase angle of attack and hence drag.
The Mirage III delta is typical. Pilots get to know that a breif haul back on the stick will result in a ready means carving off excess height. An F111 with wings swept back is even worse requiring almost full power to stay on anywhere near a reasonable glide slope. Space shuttle worse again.
But NO NO NO to stalls at low level - you will end up in a crunched heap if you persist.
Anything which increases an aircraft's drag during descent will increase the glide/approach angle.
Angle is determined by the ratio of drag to lift.
Aircraft which land / approach below their minimum drag speed, such as an unflapped delta can readily increase their glide angle by raising the nose to increase angle of attack and hence drag.
The Mirage III delta is typical. Pilots get to know that a breif haul back on the stick will result in a ready means carving off excess height. An F111 with wings swept back is even worse requiring almost full power to stay on anywhere near a reasonable glide slope. Space shuttle worse again.
But NO NO NO to stalls at low level - you will end up in a crunched heap if you persist.
Joined: Oct 2003
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From: Canberra Australia
Explanation of "Speed Instability on the Approach"
Most aircraft have a minimum total drag speed. Usually min drag speed for light aircraft is 10 to 20 kts above the stall and is the speed which gives you shallowest glide angle. Good to know it if ever you want to glide furthest in still air. Glide at speeds above or below min drag speed and the angle of glide increases.
Approach speeds are usually above min drag. Thus if you are below glide slope and inrease alpha you will go back towards intended glide slope, losing a little speed in the process. Drag is reduced down towards min drag speed and all feels natural as you regain glide slope..
High performance military aircraft often have min drag speeds well above an optimum speed for landing approach. With such aircraft below glide slope when you increase alpha the speed washes off fairly fast and the increase in drag can be large. Result is you don't get back to the desired glide slope and markedly increase the angle of descent. Pilot work load is high and many have auto throttles to keep you on speed.
Angle of glide is the cosine (I think) of drag over lift.
An F111 with wings fully swept to 72 degrees (26 degrees forward) has a min drag speed over 300 kts and a steeply rising drag below 300. Full dry power may not be enough to dig you out of the hole unless you can trade off altitude
Is that enough of an explanation?
Most aircraft have a minimum total drag speed. Usually min drag speed for light aircraft is 10 to 20 kts above the stall and is the speed which gives you shallowest glide angle. Good to know it if ever you want to glide furthest in still air. Glide at speeds above or below min drag speed and the angle of glide increases.
Approach speeds are usually above min drag. Thus if you are below glide slope and inrease alpha you will go back towards intended glide slope, losing a little speed in the process. Drag is reduced down towards min drag speed and all feels natural as you regain glide slope..
High performance military aircraft often have min drag speeds well above an optimum speed for landing approach. With such aircraft below glide slope when you increase alpha the speed washes off fairly fast and the increase in drag can be large. Result is you don't get back to the desired glide slope and markedly increase the angle of descent. Pilot work load is high and many have auto throttles to keep you on speed.
Angle of glide is the cosine (I think) of drag over lift.
An F111 with wings fully swept to 72 degrees (26 degrees forward) has a min drag speed over 300 kts and a steeply rising drag below 300. Full dry power may not be enough to dig you out of the hole unless you can trade off altitude
Is that enough of an explanation?
Joined: Aug 2001
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From: Europe
w,
Glad not to have to feel left out anymore, I at least hope that with the profane reference to your fellow fliers you did include me.
It is well known from psychology research, that those referring to others by using expressions relating to genitalia do so out of a deep frustration with their own.
May be that snippet of knowledge had escaped your attention but thought I'd be generous and share it with you so that you can avoid embarrassing yourself on these public forums in future.
Keep up the good work.
FD
Glad not to have to feel left out anymore, I at least hope that with the profane reference to your fellow fliers you did include me.
It is well known from psychology research, that those referring to others by using expressions relating to genitalia do so out of a deep frustration with their own.
May be that snippet of knowledge had escaped your attention but thought I'd be generous and share it with you so that you can avoid embarrassing yourself on these public forums in future.
Keep up the good work.
FD
Joined: Jun 2002
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From: Canada
In some types, the stall is benign. I mean really benign. You can float away all you like, and even someone who has never even flown an aircraft before will not get themselves in trouble as long as they keep pulling, keep balancing and have some rough kind of faith.
Forced landing. Too high. S-Turns are fine, sideslipping is fine, but...
Joined: Feb 2002
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From: Enniskillen
whatunion,
So for 16 years you probibly flew with hundreds of students, you flew the first four hours or so then you sat and they flew the next fifty.
I think you will find a depth of knowlege and experience on this forum that you are unlikely to find anywhere else in the aviation industry.
Some of us were never instructors but perhaps have flown more hours in many aicraft type in remote areas of the world that you might never even have heard of over the last 30 years or so.
There is more to being a pilot that the white shirt and gold bars.
So why don't you sit up and listen for a while, instead of trying to insult us, you might even learn something.
Tony
i was an instructor for 16 years so i am well used to the low hour self appointed experts
I think you will find a depth of knowlege and experience on this forum that you are unlikely to find anywhere else in the aviation industry.
Some of us were never instructors but perhaps have flown more hours in many aicraft type in remote areas of the world that you might never even have heard of over the last 30 years or so.
There is more to being a pilot that the white shirt and gold bars.
So why don't you sit up and listen for a while, instead of trying to insult us, you might even learn something.
Tony
Joined: Jun 2002
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From: Canada
Yes, hardly worth worrying about. Best to ignore the personal attacks: which of course are unwarranted, but since we all know that, they don't do any harm.
I wouldn't waste time reading the posts of anyone who can't be bothered to use correct punctuation, spelling and capitals ... just add such people to your "ignore" list.
I wouldn't waste time reading the posts of anyone who can't be bothered to use correct punctuation, spelling and capitals ... just add such people to your "ignore" list.
Thread Starter
Joined: Aug 2000
Posts: 716
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From: London
MLS - Absolutely - I'd already discounted types that are anything other than utterly stable. What I fly has a ventral fin and is very stable. No wing drop, no pitch oscillation.
As for why even raise it - just to debate, I've no idea whether it has any validity vs. S Turns or sideslipping. Just for fun I might do some tests (at a decent altitute) to compare fps.
As for why even raise it - just to debate, I've no idea whether it has any validity vs. S Turns or sideslipping. Just for fun I might do some tests (at a decent altitute) to compare fps.
Joined: Sep 2003
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From: South Norfolk, England
Interesting debate but a bit too dodgy I'd say on the approach.
However, when I was a fresh faced glider pilot, I often thought that if I lost it in cloud I'd simply spin down an out (assuming decent cloud base). My thoughts were that as spinning is a stable and safe condition for the airframe, it would be preferable to losing control and overstressing the glider in say, a spiral dive. As gliders are very benign in the spin and will recover easily ... the idea does stand up. I never used it though, and having later learnt to fly on instruments I didn't really give it further thought until now.
SS
However, when I was a fresh faced glider pilot, I often thought that if I lost it in cloud I'd simply spin down an out (assuming decent cloud base). My thoughts were that as spinning is a stable and safe condition for the airframe, it would be preferable to losing control and overstressing the glider in say, a spiral dive. As gliders are very benign in the spin and will recover easily ... the idea does stand up. I never used it though, and having later learnt to fly on instruments I didn't really give it further thought until now.
SS
Not so N, but still FG
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From: London, UK
Shortstripper: interesting point. The idea of spinning to descend through cloud has come up before, but none of us knew anyone who'd tried it. As you say, preferable to over-stressing the airframe whilst out of control in a descent. It would be psychologically disconcerting, to say the least, to start the spin above unbroken cloud, trusting (a) to the accuracy of the reported cloudbase and (b) to one's ability to remain focused whilst spinning through grey fog and so recover promptly on clearing the base. I think that, if I was stupid enough to get myself stuck above cloud (having no IMC), I would probably opt to try a straight ahead descent on instruments (telling D&D what I was up to and taking their advice) unless the instruments were broken.
Joined: Sep 2003
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From: South Norfolk, England
Yes I agree,
Like I said this was something I thought about when flying mainly old wood and fabric gliders. Machines such as Blaniks, K6/8/13's ect ect all spin very predictably and can be recovered within a turn or two at most. If the cloud base was over at least 1500 agl (pref more) I would have been happy to spin ... well, maybe "happy" is the wrong word but you know what I mean
Powered aircraft tend to spin a bit more erratically and recovery is often slower, especially after several turns. Also glider spins are very benign and you'd have to be very sensitive to become disoriented unlike a powered aeroplane. The whole point was that if you were likely to become disoriented at least a spin is a known flight state that is safe and if intentionally initiated then recovery should be pretty straight forward.
I wouldn'd seriously suggest anybody does this ... but in the context of this discussion, and bearing in mind the nature of gliders, it was something to ponder
SS
Like I said this was something I thought about when flying mainly old wood and fabric gliders. Machines such as Blaniks, K6/8/13's ect ect all spin very predictably and can be recovered within a turn or two at most. If the cloud base was over at least 1500 agl (pref more) I would have been happy to spin ... well, maybe "happy" is the wrong word but you know what I mean
Powered aircraft tend to spin a bit more erratically and recovery is often slower, especially after several turns. Also glider spins are very benign and you'd have to be very sensitive to become disoriented unlike a powered aeroplane. The whole point was that if you were likely to become disoriented at least a spin is a known flight state that is safe and if intentionally initiated then recovery should be pretty straight forward.
I wouldn'd seriously suggest anybody does this ... but in the context of this discussion, and bearing in mind the nature of gliders, it was something to ponder
SS
Joined: Aug 2002
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From: Surrey, UK.
I think that, if I was stupid enough to get myself stuck above cloud (having no IMC), I would probably opt to try a straight ahead descent on instruments (telling D&D what I was up to and taking their advice) unless the instruments were broken.
By remaining above and talking to someone on the ground you may find that there is an area within easy flying distance/time where the WX is perhaps SCT/BKN and such a perilous descent is not actually required
(A.N.C., A.N.C., I hear everyone shout, but surely part of "A" is knowing all of your available options?)
Not so N, but still FG
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From: London, UK
In the extremely hypothetical scenario I describe, I am (a) very stupid in the first place, and (b) let us assume, in need of a descent asap (perhaps low fuel and/or unbroken cloud as far as can be seen and/or pubs about to open). I suppose that this just could happen, but if I ever allowed it to happen to me in real life, I would deserve a kicking.
Last edited by FNG; 17th June 2004 at 13:36.
Joined: Apr 2004
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From: MD USA
Can I comment on a couple of points,
I have used the "high AoA" method of loosing height in a lot of different aircraft from the F-86 Sabre to the F-16 (fast jets dont much like side slip).
I have also used the "spin in method" in my old Super Cub, even I, with 50 + years and 23,500 hours still can end up looking for a big hole to get down. if I find a small hole I can put the cub in a gentle spin and down we go, just semi-recovering if things get too quick (don't tell the FAA).
I WOULD NOT SPIN IN CLOUD, STRICTLY VMC.
One more point, I was in the USAF for 30 years including a couple of scraps, and flight testing for the Feds for over 20 years, so I might just be one that does know a small bit.
I have come accross many like our friend Whatunion, being Irish and a big fella, my Mission Statement was "Please do not give me crap like this as a smack in the mouth may offend"
John Anderson.
I have used the "high AoA" method of loosing height in a lot of different aircraft from the F-86 Sabre to the F-16 (fast jets dont much like side slip).
I have also used the "spin in method" in my old Super Cub, even I, with 50 + years and 23,500 hours still can end up looking for a big hole to get down. if I find a small hole I can put the cub in a gentle spin and down we go, just semi-recovering if things get too quick (don't tell the FAA).
I WOULD NOT SPIN IN CLOUD, STRICTLY VMC.
One more point, I was in the USAF for 30 years including a couple of scraps, and flight testing for the Feds for over 20 years, so I might just be one that does know a small bit.
I have come accross many like our friend Whatunion, being Irish and a big fella, my Mission Statement was "Please do not give me crap like this as a smack in the mouth may offend"
John Anderson.
Joined: Apr 2004
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From: West London
On my keyboard (which is quite traditional) I use a finger on my left hand to press the up arrow thus enabling the fingers on my right hand to enter a letter in uppercase.
I think whatunion's problem is that one of his hands is busy doing something else. What do you think that could be???
I think whatunion's problem is that one of his hands is busy doing something else. What do you think that could be???
Joined: Aug 2002
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From: northants
Does not Xavier de Lapparent stall his aircraft to end his display?
Approach is very slow in the stall but high rate of descent, just before touchdown applies power and rolls along the runway.
The 'falling leaf' manoeuvre is also taking the aircraft to the stall, recovering, and stalling again (easier to draw than explain) to descend quickly with very little forward movement.
Approach is very slow in the stall but high rate of descent, just before touchdown applies power and rolls along the runway.
The 'falling leaf' manoeuvre is also taking the aircraft to the stall, recovering, and stalling again (easier to draw than explain) to descend quickly with very little forward movement.
Joined: May 2001
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From: 75N 16E
I suppose if you have a serious problem, you do whatever you can to get down.
I've often wondered about this, most people have done the "falling leaf" exercise at some point, where you stall and hold it stalled for say 30 seconds or more. Now if you look at the VSI you see you're only coming down at 2000ish fpm, which equates to <30 miles per hour vertical speed. Better still, your forward velocity is pretty low. Last time I simulated an EF in an Arrow, leaving the prop forward, we were coming down at 1500 fpm with a forward velocity of around 75kts.
So in the event of engine failure, without any options for a safe landing, why not stall the thing, and "float" down onto something soft, rather than hit a fence with a high forward velocity?
EA
I've often wondered about this, most people have done the "falling leaf" exercise at some point, where you stall and hold it stalled for say 30 seconds or more. Now if you look at the VSI you see you're only coming down at 2000ish fpm, which equates to <30 miles per hour vertical speed. Better still, your forward velocity is pretty low. Last time I simulated an EF in an Arrow, leaving the prop forward, we were coming down at 1500 fpm with a forward velocity of around 75kts.
So in the event of engine failure, without any options for a safe landing, why not stall the thing, and "float" down onto something soft, rather than hit a fence with a high forward velocity?
EA
Joined: Aug 2001
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From: Europe
So in the event of engine failure, without any options for a safe landing, why not stall the thing, and "float" down onto something soft, rather than hit a fence with a high forward velocity?
Few people survive a spin close to the ground. On the other hand very few people get killed when you over or undershoot your intended landing spot............
As someone mentioned on here before, you are more resilient to for aft de/accellerations than vertical ones.
I know what I'd choose.
FD