Tiger down off Straddie
Kharon,
thanks for posting those links to the tiger moth manuals interesting reading!
You must assume that there is no redundancy with the flying wires. They weren't in the habit of adding an extra flying wire here or there for good luck even though it might appear like that in some of these older types.
this quote from section 1 page 1 of the tiger manual you linked to
"in normal flight flying loads are taken by two cables on each side forming a triangle between the upper ends of the interplane struts and fittings on the lower longerons at the front spar of the bottom plane. "
i.e the flying loads are taken by wires that connect the top of the interplane struts to the root of the bottom wing. So essentially they act in much the same way struts on a Cessna 172 do and they are most likely just as critical to the structural integrity of the wing as they are on a Cessna 172.
The Tiger Moth is a solid safe and time proven design. But it is a product of a very different era. "No worries she's built like brick sh*t house mate" is indicative of a potentially dangerous misconception many people have about these machines. it's not built like a brick sh*t house it's built like a light aircraft. It was the 82 aircraft design produced by DH in a 25 - 30 year period. They learnt structural design by trial and error, lots of static testing and a few dead test pilots. by 1935 they could produce safe and efficient structures that were comparable to the all metal cessnas that came along 15 years later (and are the backbone of GA to this day).
im skeptical of statements such as this
where did this come from?
The tiger is a safe aircraft but it shure as hell is no pitts special. Unless british aerospace produce an original stress report stating this or their own analysis which suggests this (which i doubt they have) you cannot accept this. Anyway British Aerospace no longer holds the type certificate for DH moth types. DH technical support does.
thanks for posting those links to the tiger moth manuals interesting reading!
Quote:
SvW # 70 –"Including the ends of the flying wires.
The inter-plane struts and their fittings must be the weakest points as most connect through a single bolt (from memory)".
There's a good start – I wondered what level of redundancy there is; i.e. how much of the 'bracing' can be lost before a wing 'breaks'. With apologies to the 'wizards' it looks as though there are 6 bracing wires; 2 flying, 2 landing and 2 inter-plane (cross bracing). The 'flying wires' attached to 6 'hard' points, the cross bracing to four within the inter-plane struts. That's 10 hard points in all, here the mathematics get difficult (for me) it's not possible to determine the ratio of load between the 'lift' bracing and 'landing' bracing, but the manuals indicate a higher percentage on the lift side during flight (which makes sense). So, the puzzle is, if a 'weak' point fitting had let go what is the gross effect?. To loose one of a possible four cross brace fitting is within the realms of probability, but would that cause the wing to break. The loss of one of a possible six flying wire fittings would be a more serious matter (mathematically speaking). I expect the ATSB will, in due course, provide the right answers, if at all possible. Previous reports into Tiger accidents have been very good, the 1998 one - ATSB 199800648 - in particular. They were careful then to examine all the possibilities.
SvW # 70 –"Including the ends of the flying wires.
The inter-plane struts and their fittings must be the weakest points as most connect through a single bolt (from memory)".
There's a good start – I wondered what level of redundancy there is; i.e. how much of the 'bracing' can be lost before a wing 'breaks'. With apologies to the 'wizards' it looks as though there are 6 bracing wires; 2 flying, 2 landing and 2 inter-plane (cross bracing). The 'flying wires' attached to 6 'hard' points, the cross bracing to four within the inter-plane struts. That's 10 hard points in all, here the mathematics get difficult (for me) it's not possible to determine the ratio of load between the 'lift' bracing and 'landing' bracing, but the manuals indicate a higher percentage on the lift side during flight (which makes sense). So, the puzzle is, if a 'weak' point fitting had let go what is the gross effect?. To loose one of a possible four cross brace fitting is within the realms of probability, but would that cause the wing to break. The loss of one of a possible six flying wire fittings would be a more serious matter (mathematically speaking). I expect the ATSB will, in due course, provide the right answers, if at all possible. Previous reports into Tiger accidents have been very good, the 1998 one - ATSB 199800648 - in particular. They were careful then to examine all the possibilities.
this quote from section 1 page 1 of the tiger manual you linked to
"in normal flight flying loads are taken by two cables on each side forming a triangle between the upper ends of the interplane struts and fittings on the lower longerons at the front spar of the bottom plane. "
i.e the flying loads are taken by wires that connect the top of the interplane struts to the root of the bottom wing. So essentially they act in much the same way struts on a Cessna 172 do and they are most likely just as critical to the structural integrity of the wing as they are on a Cessna 172.
The Tiger Moth is a solid safe and time proven design. But it is a product of a very different era. "No worries she's built like brick sh*t house mate" is indicative of a potentially dangerous misconception many people have about these machines. it's not built like a brick sh*t house it's built like a light aircraft. It was the 82 aircraft design produced by DH in a 25 - 30 year period. They learnt structural design by trial and error, lots of static testing and a few dead test pilots. by 1935 they could produce safe and efficient structures that were comparable to the all metal cessnas that came along 15 years later (and are the backbone of GA to this day).
im skeptical of statements such as this
I found this interesting quote from an earlier report link, "The aircraft was stressed to withstand maximum loads of approximately 7.5g (acceleration due to earth gravity). Information from the manufacturer indicated that even with the reinforcing doubler delaminated and ineffective, the aircraft was designed to withstand manoeuvre loads of about 5g."
The tiger is a safe aircraft but it shure as hell is no pitts special. Unless british aerospace produce an original stress report stating this or their own analysis which suggests this (which i doubt they have) you cannot accept this. Anyway British Aerospace no longer holds the type certificate for DH moth types. DH technical support does.
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Unless british aerospace produce an original stress report stating this or their own analysis which suggests this (which i doubt they have) you cannot accept this. Anyway British Aerospace no longer holds the type certificate for DH moth types. DH technical support does.
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gods do you guys misunderstand things.
when a tiggie is flying the wing loads are borne by the flying wires alone.
the other wires actually go slack in flight.
two wires in parallel and one fails results in a sudden doubling of the load in the remaining wire which often fails it as well.
there is really no redundancy. if they work you live. if they fail the aircraft crashes and more than likely you die.
struts and flying wires are really the most important structural components on an aircraft.
when a tiggie is flying the wing loads are borne by the flying wires alone.
the other wires actually go slack in flight.
two wires in parallel and one fails results in a sudden doubling of the load in the remaining wire which often fails it as well.
there is really no redundancy. if they work you live. if they fail the aircraft crashes and more than likely you die.
struts and flying wires are really the most important structural components on an aircraft.
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god do you guys misunderstand things.
when a tiggie is flying the wing loads are borne by the flying wires alone.
the other wires actually go slack in flight.
two wires in parallel and one fails results in a sudden doubling of the load in the remaining wire which often fails it as well.
there is really no redundancy. if they work you live. if they fail the aircraft crashes and more than likely you die.
struts and flying wires are really the most important structural components on an aircraft.
when a tiggie is flying the wing loads are borne by the flying wires alone.
the other wires actually go slack in flight.
two wires in parallel and one fails results in a sudden doubling of the load in the remaining wire which often fails it as well.
there is really no redundancy. if they work you live. if they fail the aircraft crashes and more than likely you die.
struts and flying wires are really the most important structural components on an aircraft.
Then there are the incidence wires which I guess prevent twisting movements and also the unseen bracing wires between the forward and aft spars on each wing(or is it mainplane)to prevent fore and aft movement between struts.
And there are I believe four metal compression struts between the forward and aft spars in each wing keeping the proper spacing of spars and therefore shape of the wing.
And then there are the interplane struts which when sitting on the ground have the lower wing(which is supported by the landing wires) holding up the upper wing and while in flight(with the flying wires now providing the support for the upper wing) keeping the lower wing from moving up into the upper wing.
And then there is a double set of bracing wires forming the usual X-shape in front of the pilot. They are an excellent reference for staying straight for touchdown by aligning them. But I suspect the real reason for them being there is to help prevent rotational movement of the whole wing box structure as a complete unit.
Subject to any welcome corrections of course.
Maybe this will clarify things? A very relevant article appeared in the December 2013 issue of Rag & Tube, the magazine of the Antique Aeroplane Association of Australia. It was written by Mark Miller, Chief Engineer of de Havilland Support Ltd in the UK - from personal experience he's a good guy, friendly and very helpful. I would also argue that he knows about as much as there is to know about de Havilland designs. He's also very "hands on", having restored a truly immaculate DH.84 dragon.
The main thrust of the article is DHSL's concern about the amount of erroneous information floating around about dH designs, and that people may well take short cuts not being fully aware of the implications. In general the Tiger Moth features primarily here, although the Chipmunk gets a few mentions too...
It was written before the VH-TSG accident, and contains this gem:
"And the Tiger Moth, did you know, actually falls short of contemporary strength requirements for the Aerobatic Category! It was accepted at +5g/-3g (with 50% in hand before ultimate failure) only on the premise that there is limited scope to impose exceedances on such a high drag and low speed airframe."
There is also a discussion on biplane load paths:
The main thrust of the article is DHSL's concern about the amount of erroneous information floating around about dH designs, and that people may well take short cuts not being fully aware of the implications. In general the Tiger Moth features primarily here, although the Chipmunk gets a few mentions too...
It was written before the VH-TSG accident, and contains this gem:
"And the Tiger Moth, did you know, actually falls short of contemporary strength requirements for the Aerobatic Category! It was accepted at +5g/-3g (with 50% in hand before ultimate failure) only on the premise that there is limited scope to impose exceedances on such a high drag and low speed airframe."
There is also a discussion on biplane load paths:
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Wonder if the Tiger Moth was operating as Airwork/Charter or under the Warbird regulations?
I've seen a few Tigers with what appeared to be rotten vertical outer timber struts. Looking at the diagram above this vertical strut seems to be more critical than I thought.
Might be time to retire these old planes from carrying members of the public.
I've seen a few Tigers with what appeared to be rotten vertical outer timber struts. Looking at the diagram above this vertical strut seems to be more critical than I thought.
Might be time to retire these old planes from carrying members of the public.
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Troll alert!
But for those with an interest in things old but new, I found this link most entertaining.
Home - Flight School - More Abou
Home - Flight School - More Abou
Just WHY do you say so, Mr P005??
I have had the spars in my top wings inspected recently, as part of a '15 year inspection plan', including the use of a borescope to inspect the holes drilled thru for the 'slats' activation rods, and they look like brand new still!
The spars were painted with a two pack marine standard varnish on original installation, in Dec 1998, and they are certified by my LAME 'as good as new still'.
Those 'rotten' vertical interplane wooden struts are made from the finest spruce money can buy - don't ask how I know that - and I keep them sanded and varnished with the same two pack marine stuff.
They may LOOK a bit 'untidy' in between coatings due to weather affected 'flaky' varnish, but once that is sanded off and inspected, you might be suprised.....
And, yes, mine does carry members of the public....a bit more often this Summer I hope...
Cheerrsss
I have had the spars in my top wings inspected recently, as part of a '15 year inspection plan', including the use of a borescope to inspect the holes drilled thru for the 'slats' activation rods, and they look like brand new still!
The spars were painted with a two pack marine standard varnish on original installation, in Dec 1998, and they are certified by my LAME 'as good as new still'.
Those 'rotten' vertical interplane wooden struts are made from the finest spruce money can buy - don't ask how I know that - and I keep them sanded and varnished with the same two pack marine stuff.
They may LOOK a bit 'untidy' in between coatings due to weather affected 'flaky' varnish, but once that is sanded off and inspected, you might be suprised.....
And, yes, mine does carry members of the public....a bit more often this Summer I hope...
Cheerrsss
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Don't encourage him. He's not qualified to tell a rotten strut from a new one.
It might be time to retire "old" peter. Doesn't know whether he's pulling or pushing. In unison, he's a 336 "Mixmaster". The gear knob confuses him on the 337.
It might be time to retire "old" peter. Doesn't know whether he's pulling or pushing. In unison, he's a 336 "Mixmaster". The gear knob confuses him on the 337.
Might be time to retire these old planes from carrying members of the public.
Check the ATSB website - 15 incidents/accidents involving Tiger Moths in the last 43 years, with three involving an in-flight break-up (VH-TSG that we're talking about, VH-AJG on 16.2.2002 and VH-TMK on 28.2.1998) - of all of these VH-TSG is the ONLY commercial fatality in all of that period. Famously of little comfort to the victims, but the statistic surely speaks for itself.
Wouldn't it be better to await the investigation? Was the cause specific to VH-TSG, perhaps involving it's operational and maintenance history, or was it a generic "fault" involving all DH-82's? Even in the latter case and there isn't a simple (structural) rectification, there are far less dramatic precautions that could be taken, rather than an outright ban...
No hysterics and punishing innocent parties please, let's await the facts.
I flew with Mark Miller (and his father) at Duxford in their restored DH89 Rapide, painted up in WWII colours of Scottish Airways (G-AGJG). They very kindly offered me a jolly when I was exploring the hangars during one of my many visits during layovers. We slowly rattled about the English countryside checking out a couple of disused airfields. Very enjoyable afternoon followed by a cup of tea in the canteen. The aeroplane was immaculate, looked brand new. As an Aeronautical Engineer/pilot and total 'DH enthusiast' I was astounded by his wealth of knowledge in all things de Havilland.
Shame such expertise is not part of this investigation. (Maybe it should be).
Shame such expertise is not part of this investigation. (Maybe it should be).
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Dora-9 - 15 incidents and 3 in flight failures is a lot considering how many Tigers were flying during that period of time.
The reason Tigers are still flying is the "grand father" clauses in the certification. I can't imagine they's get a Type Certificate these days.
The performance of these planes is marginal, and there is not a lot of room for error flying two-up on a hot day.
The reason Tigers are still flying is the "grand father" clauses in the certification. I can't imagine they's get a Type Certificate these days.
The performance of these planes is marginal, and there is not a lot of room for error flying two-up on a hot day.
Re 'and there is not a lot of room for error flying two-up on a hot day.'
Hence the skills required laddie, ....'tis all about the skills.....
"Tis often said its easy to fly a 'Tiger', but rather difficult to fly it 'well".....
Amen.
Thanks JR..
And Mr 'D'..
Hence the skills required laddie, ....'tis all about the skills.....
"Tis often said its easy to fly a 'Tiger', but rather difficult to fly it 'well".....
Amen.
Thanks JR..
And Mr 'D'..
I Agree with you By GEorge,
but the CASA money men may not be able to afford to bring out an expert from DH Support.
I do not think they contacted DH Support during the Dragon investigation the results of which have just been published.
Regarding that investigation I did not think that the Dragon had a cross feed from both tanks.
but the CASA money men may not be able to afford to bring out an expert from DH Support.
I do not think they contacted DH Support during the Dragon investigation the results of which have just been published.
Regarding that investigation I did not think that the Dragon had a cross feed from both tanks.
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A tiger - by the tale ?
Sensible informative stuff much appreciated, there's fair bit to chew on. Just thinking out loud; Scion mentions bringing a wizards wizard in to have a look-see and the costs involved. Couple of points, we waste that sort of money everyday on taxi's and lunches and expenses, so in the great scheme of things, why not wisely spend a few more bucks. These aircraft are used commercially, BUT if the ATSB only come up with yet another of their widely published, world infamous, version of a half arsed job and another (gods forbid), similar tragedy occurs, then the money not spent will morph into a little more than just a few heads in various buckets.
Anyway – still on the Tigers trail I went looking for the original RAF specification against which DH built the beast. No luck in detail, but Wikipedia was by far the most interesting and informative. The links are below.
BAM Specs-1920. BAM Specs-Gen.
Dora 9 thanks for the article it confirms my 'coaster' calculations of 'how' the thing works, it's really very clever and proven reliable over (anyone's guess) how many tiger hours have been logged over the decades of service, in different climates both operational and meteorological. There is no case for restricting today's operations, but there is a real need to prevent knee jerk reactions and idiot calls to remove the wee beasty from service.
Anyway – still on the Tigers trail I went looking for the original RAF specification against which DH built the beast. No luck in detail, but Wikipedia was by far the most interesting and informative. The links are below.
BAM Specs-1920. BAM Specs-Gen.
Dora 9 thanks for the article it confirms my 'coaster' calculations of 'how' the thing works, it's really very clever and proven reliable over (anyone's guess) how many tiger hours have been logged over the decades of service, in different climates both operational and meteorological. There is no case for restricting today's operations, but there is a real need to prevent knee jerk reactions and idiot calls to remove the wee beasty from service.
Last edited by Kharon; 5th Jan 2014 at 22:26.
There is no case for restricting today's operations, but there is a real need to prevent knee jerk reactions and idiot calls to remove the wee beasty from service.
Dora-9 - 15 incidents and 3 in flight failures is a lot considering how many Tigers were flying during that period of time.
And then we have this brainless gem from you:
The performance of these planes is marginal, and there is not a lot of room for error flying two-up on a hot day.
And what, pray, do you think that "low performance" had to do with the Stradbroke Island accident? Or are you simply on an anti old aeroplanes vendetta?
Jack, Frank, Griffo - I apologize, I should never have responded and given this character oxygen in the first place.
By George! You had me worried about my aircraft recognition skills - on my last visit to Duxford (2013), Mike was the very proud owner of a DH-84 Dragon (I looked again, it really was a Dragon). Maybe the Rapide you went in was his from earlier?