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The tendancy to sink on final approach can be overcome by having the cabin full of birds which are flapping their wings. I note from today's paper that a Saudi airline is doing just that by carrying a large number of falcons, so it must be correct!
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Originally Posted by PaulisHome
(Post 9662396)
Meikleour
Yes. If the aircraft is moving from an airmass moving at one speed, to an airmass moving at another, then inertia is an issue in the sense that it will take time for the aircraft to accelerate to recover its desired airspeed. That's what happens as we go through wind shear on approach. Where that doesn't happen is if the aircraft stays in one airmass, whatever speed it is moving at relative to the ground. It's fairly easy to do the sums to demonstrate this, and it doesn't matter which frame of reference you use, the result is the same, though the algebra is a little trickier in one case than the other. The Bernoulli/Newton reference (for lift from a wing) is not really a good analogy. They are both ways of explaining lift that pilots use, but neither of which actually explain what's going on. (Listen to John Finnemore's Cabin Pressure for a very funny sketch on this). Newton's laws of motion are hugely accurate, at least until you get to relativistic speeds, and I don't believe we're built an aircraft like that yet. I went back and read your comment. Don't know is the answer, although if this was happening during the descent that would be entirely reasonable since you can get different winds at different heights (and then see my first paragraph above). Good points both - I stand corrected. Thinking more about it, I suspect that gusts are quite a big issue, particularly when air may not be moving horizontally, thus seriously modifying the AoA. And it's gustier closer to the ground. But you can see this effect in when thermaling a glider at a high angle of bank close to stalling speed - it's not uncommon to find the glider starting to auto-rotate as one wing hits an adverse gust. Easily fixed with some forward stick and opposite rudder, but you really need to be able to do it from feel. cats_five Sounds sensible. For those of us that do mountain flying it's entirely possible to be turning within a low few hundred feet of the ground in rather gusty conditions. But I think the key is if you'r going to put yourself in a position where a spin is possible (ie slow, gusty, turning), then being high enough to recover might be smart. So we do the low turns quickly. |
You will need to turn finals a lot higher than 500' to be able to recover a spin. The problem isn't that it's impossible to recover an incipient spin in less than 1000', it's that most people have never experienced one and so aren't spring-loaded to start the recovery, and probably go through a significant panic time before they recall some vague, distant memory of what they're supposed to do. And that WILL kill you. Which is why imo getting some spin training (and other unusual attitude stuff) is a REALLY good idea, once you have a couple of hundred hours under your belt. (It is dangerous though - it led me to a seriously expensive aerobatic habit). |
Anyway, it is not wind shear it is wind gradient, wind shear is when the wind is traveling in a different direction at a lower level, not slightly slower due to surface friction.
Landing towards high trees or a hill, you have a headwind on final and a sudden rotor generated tailwind just before you land. That's the shear. |
Next week we will discuss Schuler tuning but the net effect is a "did we land or were we shot down" landing |
The usual explanation was "the copilot landed it" (not Concorde specific). :{ "That was a very nice landing, Captain" said the ATC chap in the tower. "Not me, mate", I replied, "That was the co-pilot's landing - and yes, very good it was too!" |
You will need to turn finals a lot higher than 500' to be able to recover a spin. But in principle I agree with n5296s too. It should be entirely possible to recover from an incipient spin in much less height than that (and is). It's just that a small but non-zero stream of pilots (with spin training) get themselves into a situation where they don't. Paul |
And at the risk of confusing people, I thought I'd share the following.
Some sea birds have a rather neat trick called dynamic soaring. It uses wind gradient to stay airborne without flapping their wings. Very neat trick if you can do it. Close to the sea the wind is going slower than the wind a bit higher up. By climbing through the wind gradient, airspeed increases and they can extract energy. Then turning downwind, they descend through the gradient, increasing airspeed in the dive. Repeat doing linked semicircles and they stay airborne and move along without flapping. It has been done in a glider, but it's a bit tricky. Paul |
n5296s, re Concorde. What you describe is a wind gradient effect. As I said in my earlier post, these changes in windspeed with height near the ground (unlike a steady-state wind relative to the aircraft which has no effect) do indeed have very real effects on aeroplanes.
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Originally Posted by Right Hand Thread
(Post 9662685)
<cough!> Windsock.
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But Concorde or not, 'Ground Effect' is not wind speed change it's simply ground effect !
mike hallam |
mikehallam - very true, and particularly effective on Concorde where there is lot more wing area, and a lot closer to the ground on landing, at the back of the aeroplane rather than the front.
A Concorde captain described to me landing the beautiful white bird as easy if you maintain the attitude. But as the aeroplane flies into ground effect this acts much more at the back of the aeroplane because of the above, and tends to force the nose down just before touchdown. This must be countered by the pilot easing back just enough to prevent that nose drop and maintain a constant attitude, whereupon the main wheels, he said, will touch down in elegant style. Thus one does ease back on landing as in a conventional aeroplane, but it's not a flare, it's just to counter that ground effect... effect! |
I was taught in my PPL training back in 1981 that low and slow was an area to avoid.
Height and speed is my motto and I am still here. In my early helicopter training I was stressed to focus on the avoid curve. Helicopter Aviation |
I agree entirely Cats 5, which is why we don't fly slow in a finals turn. But in principle I agree with n5296s too. It should be entirely possible to recover from an incipient spin in much less height than that (and is). It's just that a small but non-zero stream of pilots (with spin training) get themselves into a situation where they don't. |
If you do a regular recovery as soon as you feel the stall/spin breaking away, 500' is plenty. Not, again, that I'm recommending going out and trying it at that altitude. I have read hundreds of reports where, let's say, all,perished from a loss of control/spin in, within the circuit pattern. |
Originally Posted by maxred
(Post 9663829)
Not wishing in any way to dampen a thoroughly entertaining read, but has anyone, witnessed, completed, heard of, a spin recovery, in the circuit, from 500':rolleyes:
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I am sure it is, but with respect a glider may handle differently to a powered aeroplane. I have only had one flight in a powered motor glider, so would not be qualified to confirm the above. Sounds like an interesting experience you had......
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Originally Posted by maxred
(Post 9663829)
Not wishing in any way to dampen a thoroughly entertaining read, but has anyone, witnessed, completed, heard of, a spin recovery, in the circuit, from 500':rolleyes:
I have read hundreds of reports where, let's say, all,perished from a loss of control/spin in, within the circuit pattern. .....it happened because I pulled a lot of G in a hard turn. |
I have read hundreds of reports where, let's say, all,perished from a loss of control/spin in, within the circuit pattern. If you read what I wrote, it wasn't, "it's easily survivable, anyone can do it." It was, "someone who is familiar with spin recovery should be able - in any reasonable type - to detect and recover form an incipient spin in less than 500'". I then went on to say that most low time pilots, who aren't familiar with spins, will probably panic for long enough to make the fatal difference. I experienced one incipient spin while I was training, and solo (practising power on stall recoveries). It took me a second or so to realise what was going on, and recover. At 3000' it made no difference. At pattern altitude maybe it would have. |
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Having done spinning in a Chipmunk, I was at first startled at the height the Instructor deemed safe for spinning a Tiger Moth. There are big differences between aircraft in the height needed for safe spin recovery.
And C of G will affect it. |
"I was once on final in a glider with an instructor, at 400 ft he said "I have!" And spun it losing 200 ft. "You have" he said as two Tornadoes roared overhead at 4/500 ft. I recovered it and landed, along with "what the f**k". So it is possible."
If true, I sincerely hope this instructor NEVER flew again, let alone instructed. |
Not wishing in any way to dampen a thoroughly entertaining read, but has anyone, witnessed, completed, heard of, a spin recovery, in the circuit, from 500':rolleyes: https://aviation-safety.net/wikibase/wiki.php?id=39240 Which left a lasting impression that such maneuvers are foolish |
Exactly Step. Deliberately spinning at low-level is like practicing bleeding.
Its breathtakingly stupid. In the glider example cited I don't understand the relevance of the two Tornadoes either. If the instructor's intention was to lose height quickly, a spin is not the correct manuver. I call bulldust. I was tempted to ask "what sort of glider" but then realized its a moot point, bulldust is bulldust. |
Originally Posted by Thud105
(Post 9664435)
"I was once on final in a glider with an instructor, at 400 ft he said "I have!" And spun it losing 200 ft. "You have" he said as two Tornadoes roared overhead at 4/500 ft. I recovered it and landed, along with "what the f**k". So it is possible."
If true, I sincerely hope this instructor NEVER flew again, let alone instructed. So did any other pilot in the club. He was no cowboy, and taught me and many others very well. He spun the thing as the quickest way to lose height without over speeding, go around not an option. The Tornadoes were on a collision course and hadn't seen us. Please don't jump to conclusions. It certainly was not done for fun!! The actual manoeuvre amounted to an upside down nose down rapid loss of 200ft followed by recovery. As we got to about 45deg he handed it back. It was a K13 glider. Whether you wish to call it a true spin I really couldn't say, it happened too quickly. It certainly rotated around its long axis with the nose down. Call it what you like, but bull dust it certainly wasn't. |
bulldust. |
He spun the thing as the quickest way to lose height without over speeding |
Sorry, I'm not buying it. So, you're on the approach at say 400ft and 55kt in a -13. Want to descend quickly? Full brakes and lower the nose - a 13's brakes are speed limiting. Or, as Step suggests - a very steep side-slip with full airbrake.
The whole thing sounds incredibly fraught - if not dare I say unbelievable. Upside down at 300ft, and then he handed control back........ |
Originally Posted by Thud105
(Post 9664572)
Sorry, I'm not buying it. So, you're on the approach at say 400ft and 55kt in a -13. Want to descend quickly? Full brakes and lower the nose - a 13's brakes are speed limiting.
The whole thing sounds incredibly fraught - upside down at 300ft, and then he handed control back........ After the event the instructor called Leuchars military and asked, pretty much, what the hell they were playing at. They denied all knowledge. At the weekend the two Tornado crews arrived at the gliding club, apologised profusely for an error of "cross a big lake, between two hills, down the valley and turn left". And spent the evening buying the beer. They picked the wrong two hills and flew over our airfield by mistake. I remember the incident very well even though it was '85. |
I believe the event happened. I don't believe you spun at 400ft, or were inverted at 400ft. Either event in a K-13 would, IMHO only end with a crash. Very steep side-slip with full airbrake is the most plausible scenario - IMHO of course.
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Originally Posted by Thud105
(Post 9664597)
I believe the event happened. I don't believe you spun at 400ft, or were inverted at 400ft. Either event in a K-13 would, IMHO only end with a crash. Very steep side-slip with full airbrake is the most plausible scenario - IMHO of course.
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So we're finished with the discussion about Tornado avoidance maneuvering in the K13, one way or the other?
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Well from my memories of spinning K13 - from annual check flights, were that to get it to spin you needed - for a spin to the right:
Approach the stall speed from straight and level. Before you reach stall pull the elevator full back (thus gaining altitude) and at the same time apply full left aileron to get the right wing to stall. While doing this apply full right rudder. So you entered the manoever holding the stick hard back and to the left with your right leg fully extended to hold the right rudder in. This would create a sort of flick roll entry which is most cases would then become a spin - though on some occasions if the timing of the control inputs was a little out it would instead enter a spiral dive. Recovery was the usual opposite rudder while moving the stick forward with ailerons neutral and recover from the ensuing dive. Notice I said 'while' in the preceding sentence not the usual power aircraft default of opposite rudder wait and then stick forward. If you held the stick hard back (at my CofG loading anyway) and just applied opposite rudder (left in this case) then the direction of the spin immediately reversed and you would need to apply in this example right rudder again plus stick forward to get it to come out. I hope this is of some vague interest - if anyone is remotely bothered......... |
Originally Posted by Thud105
(Post 9664730)
Well, in that case you weren't at 400ft. And I don't need to have been there to know that either spinning or being inverted at that height in a K-13 could only end in a crash, whereas you claim he then "gave it back to you." Note also that - as Step points out - to spin abruptly would require a gain in altitude.
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I remember the incident very well even though it was '85. |
I have always been quite good at recalling details, I was trained to do that in the military. I am also not guilty of elaborating on facts as I remember them.
This manoeuvre did not involve waiting for the stall, followed by what may be considered normal intentional spin entry procedures. This was a rapid application of left aileron until beyond 90deg followed by a hard pull as the rotation continued, at the point of about 45deg before returning to level and with the nose starting to rise, but still well below horizonal, control was given back to me. I continued the rest of the roll and nose levelling and then landed. Perhaps it was not a true spin in the normal sense of climbing stall, rudder, aileron or whatever, followed by opposite rudder, forward stick recovery. But, the aircraft rotated through 360deg around the long axis, lost about 200ft in the process, enough to avoid the threat. I do recall seeing the condensation around the Tornadoes dead ahead. We certainly lost the height far quicker than any normal upright manoeuvre of dive, side slip, air brakes or stalling would have produced. Please don't insult my intelligence by telling me I was not inverted but in a side slip instead. And at half a field short of the touchdown point I was not far away from 400ft. Though I am not in the habit of staring at the instruments at that point in the landing process. Edit: the Tornadoes were crewed by Americans from somewhere else. |
You must be misremembering; the US has never operated Tornado.
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This manoeuvre did not involve waiting for the stall, followed by what may be considered normal intentional spin entry procedures. This was a rapid application of left aileron until beyond 90deg followed by a hard pull as the rotation continued, It is very important for pilots to recognize and correctly react to one vs the other, in recovery. The recovery for one, applied to the other situation, could be messy. I accept that the other pilot flying the glider flew a purposeful evasive maneuver (which worked), but as I understand the description, if that pilot was asked if they had deliberately spun the glider, I doubt that answer would have been yes. |
Crash one.
Leuchars operated Lightnings until around 1969. F4 Phantoms followed for the next several decades with Tornados only becoming operational from that Airfield in April 2001. Since you mention the lake (loch) you must have been flying from the Scottish Gliding Union at Portmoak - I am left wondering who the instructor was as I must admit to never having heard of this incident. Perhaps you could PM me with the name as I do have an interest as a past CFI and safety officer at Portmoak. It is possible that the aircraft were indeed Phantoms as the Americans also operated this type within the UK and were, quite often, involved in the low flying and other military operations with the Scottish region. The usual route to/from Leuchars was to the North of Bishop Hill between that and the Ochils. Americans, unfamiliar with the area, might well have aimed for the gap between Bishop and Benarty Hills although that track would also have taken them low over Glenrothes airfield to the East of Portmoak. Leuchars were well aware of Portmoak and there was a letter of agreement between them and the Scottish Gliding Union re their circuit requirements in Easterly winds as they came close to our own circuit in those conditions. A somewhat out of context post but I am intrigued by your experience. As an aside low slow or steep turns in gliders close to the ground, especially long span ones, were never a good idea. This was not so much because of the danger of the lower wing stalling from being in the lower slow moving mass of air on turning into wind but more from the differential lift between the tips at differing airspeeds. The lower wing in slower wind speed due to wind gradient effect plus moving at lower speed than the outer wing equals a considerable amount of extra lift on the upper wing. The early long span gliders were a bit lacking in aileron effectiveness and thus might not have had powerful enough ailerons to actually level the wings for landing. |
My last dual flight before solo in a K13, Lasham, 1990 - instructor pulled off the winch launch early, 900 feet, but told me to keep the nose up into a stall, then bank to the left, which precipitated a spin - normal spin recovery, lost 400 feet with just over 1 revolution, so about 600 feet when recovered, just right for a normal circuit. He cleared me to solo after that.
FBW |
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