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#1
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Nimbus 4DT accident 31 July 2000 in Spain.
The Spanish authorities have now published their report on the accident to
the UK registered Nimbus 4DT which crashed on 31st July 2000 near Toledo, one of the British crew was killed. The Spanish report in English translation may be found at http://www.gliding.co.uk/accidents/r...s4dtreport.pdf (3MB). The BGA report is at http://www.gliding.co.uk/accidents/d...dentSummary=67 . If this will not open, go to http://www.gliding.co.uk/accidents/login.php , Username user, Password risingmoon. The similar accident to a Nimbus 4DM at Minden on 13th July 1999 ref: LAX99MA251 may be found at http://www.ntsb.gov/publictn/2002/AAB0206.htm brief report is at http://www.ntsb.gov/NTSB/brief.asp?e...12X19310&key=1 . W.J. (Bill) Dean (U.K.). Remove "ic" to reply. |
#2
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W.J. (Bill) Dean (U.K.). wrote:
The Spanish report in English translation may be found at http://www.gliding.co.uk/accidents/r...s4dtreport.pdf (3MB). Thanks for the link. Very educational, indeed. I think this answers the question whether spins and spiral dives should be demonstrated and recovery should be regularly trained. Stefan |
#3
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Yes, indeed. If anything, the spiral dive recovery is more critical from a
structural standpoint. A modern glider is more likely to progress to spiral dive anyway. The pilot, by his own admission, did the wrong recovery for either case. However, since the Spanish report refers heavily to the Minden report, with many similarities, I wonder if there is something peculiar about the Nimbus 4 DT. Both apparently departed into a stall and incipient spin in a strong thermal. This pilot had sufficient recent flight experience, and total time, to have developed good "survival" reflexes, including the "stick forward" manuver. He had little time in the Nimbus 4, but quite enough in the Nimbus 3 to know how to fly it. If it was purely the fault of very strong thermals, then the other gliders in common use at places like Minden would also have similar accidents. This does not seem to be the case. Obviously, I have never flown a Nimbus of any kind. I have a few hours in the Duo-Discus, but nothing larger. The Duo is certainly not malignant in any way. So my question is to those with Nimbus D experience. Is there some handling characteristic that will bite a fairly experinced and competent, but unsuspecting pilot? I am thinking that the (biennial USA) Flight Review should include spiral dive recovery routinely, in addition to the usual other "emergency" maneuvers. -- Hartley Falbaum CFIG USA "Stefan" wrote in message ... W.J. (Bill) Dean (U.K.). wrote: The Spanish report in English translation may be found at http://www.gliding.co.uk/accidents/r...s4dtreport.pdf (3MB). Thanks for the link. Very educational, indeed. I think this answers the question whether spins and spiral dives should be demonstrated and recovery should be regularly trained. Stefan |
#4
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None of these big gliders are very good at diving. I don't believe there
is anything sinister about the N4DM. They're just not built for diving. Any time the nose is well below the horizon, they will pick up speed rapidly. Don't do that. Large span gliders will fly slowly and that means that there is a large airspeed difference across their span when circling - my "little" Nimbus 2C can develop a 15 knot difference. This, plus a thermal gust, can make them roll into a spiral dive. Recognizing this and taking prompt action when it happens is actually easy once you experience it a few times. Just allow the speed to increase a bit to increase control authority, then stop the turn and then recover normal airspeed. If the glider is allowed to progress into a full spiral dive, the options narrow considerably. Only very gentle and precise control inputs will save the day. Try not to apply large aileron and elevator inputs simultaneously - bending and twisting the wing at the same time can break it. Reading the Spanish report made it seem that the pilot did not have complete control of his glider. That's a shame when it's a two seater and there are a lot of experienced pilots who would have been willing to ride with him and help him master it. Bill Daniels "HL Falbaum" wrote in message ... Yes, indeed. If anything, the spiral dive recovery is more critical from a structural standpoint. A modern glider is more likely to progress to spiral dive anyway. The pilot, by his own admission, did the wrong recovery for either case. However, since the Spanish report refers heavily to the Minden report, with many similarities, I wonder if there is something peculiar about the Nimbus 4 DT. Both apparently departed into a stall and incipient spin in a strong thermal. This pilot had sufficient recent flight experience, and total time, to have developed good "survival" reflexes, including the "stick forward" manuver. He had little time in the Nimbus 4, but quite enough in the Nimbus 3 to know how to fly it. If it was purely the fault of very strong thermals, then the other gliders in common use at places like Minden would also have similar accidents. This does not seem to be the case. Obviously, I have never flown a Nimbus of any kind. I have a few hours in the Duo-Discus, but nothing larger. The Duo is certainly not malignant in any way. So my question is to those with Nimbus D experience. Is there some handling characteristic that will bite a fairly experinced and competent, but unsuspecting pilot? I am thinking that the (biennial USA) Flight Review should include spiral dive recovery routinely, in addition to the usual other "emergency" maneuvers. -- Hartley Falbaum CFIG USA "Stefan" wrote in message ... W.J. (Bill) Dean (U.K.). wrote: The Spanish report in English translation may be found at http://www.gliding.co.uk/accidents/r...s4dtreport.pdf (3MB). Thanks for the link. Very educational, indeed. I think this answers the question whether spins and spiral dives should be demonstrated and recovery should be regularly trained. Stefan |
#5
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Neither this report nor the Minden report it references
mentions anything about the ASI installed. Were they the wrap-around types which cause the pilot to not know if the glider is in a spin or a spiral? I personally have been in a spiral in a glider, and not knowing it was a spin or spiral, have done the spin recovery. Fortunately the glider performance was low enough this wasn't a problem. To verify this, I replicated the same situation twice more on the same flight. It was surprising how little onformation I could get through windspeed noise. I was relying on the ASI, and it was ambiguously reading either 30kts or 100kts. Only after landing and seeing the GPS info did I fully believe that I was spiralling, and not spinning, even though I watched the ASI go only from 'fast' to 'really fast.' Are these gliders regularly installed with the wrap-around type ASIs? Could 1.8 seconds of confusion be a contributing factor in these cases? Of course, assume for the moment that the translation to english is awkward and the mention of 'spin' may be mistranslated... Has anyone else on this group ever looked at a wrap-around ASI and wondered what it said? Have you tried this with students, having them close their eyes and violently shake their heads and then try to recover the glider in an unusual attitude? And have them get confused? I certainly see the value of the wrap-around ASI and the added precision it allows during normal flight, but I'm not terribly fond of them for spin vs. spiral recognition. I don't trust my hearing as an airspeed indicator during stressful situations. At 22:42 20 June 2005, Stefan wrote: W.J. (Bill) Dean (U.K.). wrote: The Spanish report in English translation may be found at http://www.gliding.co.uk/accidents/r...s4dtreport.pdf (3MB). Thanks for the link. Very educational, indeed. I think this answers the question whether spins and spiral dives should be demonstrated and recovery should be regularly trained. Stefan Mark J. Boyd |
#6
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M B wrote:
Neither this report nor the Minden report it references mentions anything about the ASI installed. Were they the wrap-around types which cause the pilot to not know if the glider is in a spin or a spiral? I understand you're an instructor? I shudder at the thought that a licensed pilot, let alone an instructor would rely on the ASI to tell whether he's in a spin or a spiral. Stefan |
#7
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M B wrote:
To verify this, I replicated the same situation twice more on the same flight. It was surprising how little onformation I could get through windspeed noise. I was relying on the ASI, and it was ambiguously reading either 30kts or 100kts. Don't the controls feel differently at 30 knots and 100 knots? That should be a good clue as you begin the spin recovery. -- Change "netto" to "net" to email me directly Eric Greenwell Washington State USA |
#8
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"Eric Greenwell" wrote in message ... M B wrote: Don't the controls feel differently at 30 knots and 100 knots? That should be a good clue as you begin the spin recovery. -- Change "netto" to "net" to email me directly Eric Greenwell Washington State I am a partner in a Nimbus 3D. I have not had a lot of time in it but have flown aircraft of all kinds for 36 years including hundreds of glider and powered aerobatic hours. In order to get the Nimbus to go beyond the green arc it takes a very large amount of forward stick even with the trim all the way to the forward stop.....with flaps in -2. I absolutely disagree that it would be easy to let it get away from you and end up in a spiral with the exception of possibly entering it from a spin. The spin enty on the other hand is docile and easy to recover from. As has been pointed out, if one is clueless re incipient spins then the scenario in these 2 accidents might easily unfold. Only education, planning and practice will prevent similar accidents. Casey Lenox KC Phoenix |
#9
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KC, yup.
I wonder at the thread though. Everyone discussing recognition of a fully developed spin versus spiral dive. Years ago, Al Blackburn pointed out to me that long span gliders need to be treated gingerly at speed. His concern had to do with the application of aileron during dive recovery. While he felt that most pilots could manage the elevator to avoid structural damage, aileron asymmetry (and the resulting squatcheloid assymetry) presented a complicating factor. The longer the span, the more critical its effects. Add a partial load of water, a yaw moment, and/or spoiler caps deploying with wing bend and it's not hard to see how things might quickly get to the breaking point. |
#10
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As long as a 26m glider is certified under JAR22, there is no issue of
control inputs versus speed other than for a 15m glider. What changes drastically with a long wing is the entry into a spin or a spiral dive. The long wing makes that you can have large discrepancies of effective angle of attack along the wingspan (which can make the spin entry under g-load quite interesting). Long wings also have much more angular momentum once the spin/spiral dive is developped - it can be as much as 5 times the angular momentum of a 15m glider, and that makes that recovery will take a certain time even if correct counter procedures are undertaken. And during that time, the glider will accelerate like hell so that you are likely to operate you final recovery well beyond what's written in the flight manual. I think that training of instant recovery of a spin entry (or spiral dive entry) is mandatory if you want to fly a 25+m ship safely. But in contrary to short wings, it would be plain stupid to train the recovery of a fully developed spin/spiral dive in these ships (beyond fligh testing for certification) and that's the reason that a flight manual will usually call it illegal. Been there, done it, and don't feel that I want to get there again. -- Bert Willing ASW20 "TW" a écrit dans le message de news: ... KC, yup. I wonder at the thread though. Everyone discussing recognition of a fully developed spin versus spiral dive. Years ago, Al Blackburn pointed out to me that long span gliders need to be treated gingerly at speed. His concern had to do with the application of aileron during dive recovery. While he felt that most pilots could manage the elevator to avoid structural damage, aileron asymmetry (and the resulting squatcheloid assymetry) presented a complicating factor. The longer the span, the more critical its effects. Add a partial load of water, a yaw moment, and/or spoiler caps deploying with wing bend and it's not hard to see how things might quickly get to the breaking point. |
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