And Dora…..what on earth would you know about these :} :ok:

Well, that means we've only just got started, and we have another 50 pages of unbelievably wild, and wilder speculation, to go yet - until the ATSB final report appears, in perhaps 18 mths time. :)

Jaba:

Written as the outmaneuveree!

I blame Stalls and Spins.
 

Got home only to discover been banished from the houseboat kitchen. I decided to use the time to try and learn a bit more about Tigers, the net is great, but there is a load of useless information to wade through; I expect the trick is knowing what to search for. Even so, it's a great tool. I found the following most instructive – DH82 – and – Avilogs. Most DH 82 buffs will be all over it, but for a layman, they helped a great deal.

The geometry of the DH 82 flight load management is a testament to the KISS principal. I was fascinated with the amount of repair detail provided for the metal parts of the airframe, compared to the timber parts described in the -Avilogs - 1947 Maintenance and repair sections. It was also interesting to note the 'terminology' used, the term 'see' rather than 'check' for example.

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.

Cherry picked from ATSB 199800648, (simply to assist head scratching and muttering).

The notion of a sudden load transfer combined with a loss of 'bracing' creating enough force to break a wing claimed to be within ::  7g to :: 5 g is intriguing.

Enough; time to mount my cunning plan to steal mince pies, cream and any loose choccy frogs the dogs didn't get. MC y'all.

Good point on the wires themselves. Here is an airworthiness bulletin from CASA. A little bit of oil on the wires can prevent corrosion, especially if you are near salt water. I would think that oil or grease in the extensive threaded areas of these wires is a good idea. I believe that moly disulfide grease could be a preferred type.



http://www.casa.gov.au/wcmswr/_asset...awb/02/012.pdf

"Several in-flight failures of stainless steel streamline wires have occurred with various de Havilland aircraft in recent years. Fracture of streamline wires reduces the structural integrity of an aircraft and may result in widespread structural failure."

Well written Mr K,

However, there was much 'local' discussion at the time of the VH-TMK crash re the 'slats' induced problem, or the 'delamination' of the spar due to the 'casein' glue failure...

From the same report -
'Engineering analysis by British Aerospace determined that slats deploying during a looping manoeuvre would not cause a serviceable wing to fail.'

I'm sure that more than one of us has watched those slats 'working' at various speeds / attitudes / turns etc, and marvelled at their efficiency.

Cheers;)

Folks,
The DH82 ( and the Chipmunk) were both designed to RAF requirements, not civil standards.
Structurally, they were accepted "as is" for original civil certification (let's not argue about anti-spin strakes)
Tootle pip!!

"I'm sure that more than one of us has watched those slats 'working' at various speeds / attitudes / turns etc, and marvelled at their efficiency."

This.

environment
 

I live near Luskingtyre where a lot of Tigers are flown and rebuilt. Not uncommon to have them doing aeros overhead the house and I attend "Lunch with the Tigers" regularly. Enjoy it immensely and hope this accident does not effect the good times everyone there enjoy.
Some interesting comments about how and possibly why but I can't help but think of the importance of the environment this Tiger had been operated in over it's working life.
Flown hard and only possibly maintained to a profit driven cost and not maybe the usual passion a Tiger receives and in an exceptionally SALTY atmosphere. Sure will be interesting to read the final report.


GoPro cameras mounted to helmets. As a skydiver I own one just like everyone else. Compromising helmet integrity? Not with the stick on mounts. I could understand maybe potential distraction. Seen several jumpers have incidents caused by being to distracted in their camera that's why we have minimum jump numbers to use one. As for police using them, why not? They can use mobile phones and txt legally so why not mount a camera on their helmet. Not surprised that insurance companies will want them mandatory for both driving and flying sooner or later. As usual CASA is the problem.
FH

Leady,

Fair point regarding the DH.82, but the Chipmunk Mk.21 was built "ground-up" as a civil aircraft, and certified in the UK, from December 1950 to September 1951, as an aerobatic category aircraft.

Also, at the risk of nit-picking, in reality they're spin-recovery strakes. If they actually achieve anything is another issue!

Sure, but a glancing blow the mount will snap, albeit with a potential twist or snap motion to the wearers neck,
But if the impact to the helmet is at 90 degrees the mount, it translates all the energy to the 2sq cm small surface area of the mount. (assuming the impact is not with a pointy object)
Also there is the increased risk of the protrusion fouling cables and restricting emergency egress.
Whilst these circumstances are highly unlikely to occur we should move toward integrated and certificated mounts like those for night vision kit.

Apart from heavy cameras used by skydivers, I don't know of any cases where helmet mounted cameras have adversely affected the wearer.
I developed the first ever TV "hat cam" in 1985, they have come a long way since then!

Mickjoebill

IMO, the attachment of Go-Pro mounts will probably feature a lot lower in investigators sights, than the investigation of the circumstances regarding previous accidents to the aircraft, and how the repairs to those previous accidents were carried out.
I understand that VH-TSG has had a chequered history and cannot be positively identified as to its true provenance.
Who knows what has actually happened to this aircraft, as regards repair from many decades ago, if it's true provenance cannot be identified?
It appears that VH-TSG could also have been used for ag spraying, with possible resultant chemical spray effect on airframe components being added to the investigators list.

VH-TSG

I believe VH-TSG was also involved in an accident as recently as 12 yrs ago. I cannot find any ATSB report relating to that incident, but no doubt, available repair records from any incidents involving VH-TSG will be scrutinised.
One would trust that the potential for the vastly increased likelihood of corrosion in metal components that are buried in wood - when used in a humid coastal environment, such as TSG was being operated in - was also understood by the owner/operator.

a 30 year history of being aerobatted as often as 3 times a day wont come into it of course. it will be some mysterious metallurgical fault.

...much to the misery of all the other owners with totally different usage histories.

Interesting post One track, the links make for interesting reading, Cheers.

Did a little scratching about, nothing serious just enough to get a better handle on the subject and there appears to be many more tales (across the fleet) of first class repairs and careful restoration than anecdotes of 'dodgy' repairs. The only ugly story was one where 'Bog' (motor body filler) was used to hold together a critical, deeply hidden timber repair; but even in that case the bodge job had withstood the test of time and was discovered the rectified by 'honest' diligent maintenance folk.

One of the more 'interesting' tales is related to 'boxed' ex factory spare parts being used to construct a whole aircraft, which when you think about it is not such a bad thing. I expect there would be some 'legal' issues to cause irritation, but the aircraft from an operational perspective at least would literally be brand new, out of the box.

I also had some tales of 'retired' ag aircraft finding their way back into service, but there is no evidence to support the 45 year old tale.

Interesting sidebar to this element; it seems that before 'new age' materials were used, the 'old' fabric needed to be peeled off and replaced every few years, as part of this process the timber could be thoroughly inspected. I'm told the modern fabric lasts much, much longer than Irish linen which precludes the more frequent 'involuntary' inspections.

Can anyone provide an update on how much of the aircraft was recovered ?, must be a hellish job trying to find all the pieces; Murphy's law being as it is.

It's the way of the world, you know the old joke – "but shag one bloody sheep..etc.."

one of my Austers was used for crop spraying for about a year.
far from causing lots of hidden corrosion issues it was actually the making of the old girl.
when they gave up on ag spraying with the old girl the lame stripped back the entire underside, sorted it out and put new fabric on.
when I came to bead blast the entire airframe about 10 years ago there was not one skerrick of corrosion on the underside tubes of the aircraft.

crop dusting around Colleambally in about 1965-8
redone about 1968
beadblasted and found to have zero corrosion 2000

so dont write off a tiggy that has been used for ag spraying. it may not have harmed it at all.

An extremely unfortunate accident. I know all posters here feel for the pilot and passenger involved - a very sad departure of very young lives.
Thanks to ATSB for a quick prelim report gained from the go pro evidence. Let's hope that evidence can be expanded on as soon as possible to give us an understanding of the cause of the structural failure of the wing.
As a tiger owner and friend of many other owners I can say unequivocally that we maintain our machines to what we believe is the highest standard. We accept that these are old machines and that expert knowledge is required to maintain them - that knowledge does still exist and as far as I know we all access that pool.
That such a robust, albeit old, aircraft can fail in this fashion is a concern. That there has been only 2 structural failures in the past 40 or so years, although somewhat comforting, does not lessen that concern.
Then again, many spam cans have also failed unexpectedly.
I am sure that all DH 82 owners are on double the lookout during future maintenance until the ultimate cause of this structural failure is determined.

No offence meant; I only was curious about why DCA felt the need to retire apparently serviceable airframes from agricultural operations; seemed a strange thing to me. As you say, repairs and rectification would return the aircraft to service, no permanent harm done. Reading back through the old 1947 manual there are 'fixes' for just about every metal part, so even if the dreaded corrosion had taken hold, it seems that it could be very quickly and painlessly sorted.

I agree with Chairman though, there is a deep pool of expert knowledge available - world wide, it's impressive to find such dedication and freely available knowledge on tap to doting owners. I'd risk a choccy frog and bet that the canny 'Tiger' wizards have some ideas on what happened and are only waiting on hard data to confirm them. Lets hope the ATSB manages to do this sad event justice. HNY all.

No DH 82 permitted to do aerial agricultural work after December 31 1965 due to their high accident rate and availability of more modern aircraft.

Based on the information available for the Tiger Moth I fly, I tell people that the only part of the aircraft that I can guarantee is original is the dataplate. Who knows what happened in the old days prior to its initial restoration which was by a spotty operator with several Moths.

I remember visiting a Tiger Moth restorer and among his many items were several dataplates, all future Tiger Moths if an appropriate fuselage can be found.

Praise indeed.
 

Given that the same 'piano factory' designed and built the 'Tiger', which has, despite some 'operational abuse' survived the test of time. Given that the inherent simplicity and 'toughness' of the design made it 'easy' to repair. Given that 'in the old days' the engineers were, by nature, no less interested in doing the 'right thing'. I am left wondering: allowing for the passage of time, the different operator interests, multiple inspections and 'rebuild' phases of the 'modern' Tiger, could even the most slip shod workmanship of the past affect today's tiger, in such a dramatic manner?

The Grandfathers axe argument has real merit.