Safety mods. to airworthy warbirds? A hypothesis.

Quote:
Originally Posted by TonyT
That is modifications, NOT construction techniques which is how the Airframe is put together.

ok then, Spitfires assembled with AN rivets, does that count?

I can only speak of the ones I know, and they use British hardware in repairs and construction. End of the day legally speaking, if the rivets have been replaced with none approved AN items the Aircraft is unairworthy……

for more information see

http://www.caa.co.uk/docs/33/20100607Draft4.pdf

Have you ever thought why there is no aircraft manufacturing [Airbus/helicopter sub contracting excepted] in the UK????

The world has moved on from the CAA ideas on most things…

Airbus actually fought through the changes that brought about EASA and in a way rightly so.
At the time a 737 operated in the US might not have been acceptable in different Countries across the world as certain items on the aircraft would be not approved in those Countries, the brake packs that have operated for hundreds of thousands of hours in the US fleets may not have been accepted in say the UK, necessitating a design change for the UK, like wise Germany might have not accepted a aircon pack design, France a seat design, Holland a toilet design….
This was clearly stupid and would have meant Airbus designing and producing several different items for different nations and when these were sold to other countries they would need to be replaced or modified to meet that counties legal requiremnts, clearly a common standard of A320 A330 etc needed to be adopted to allow Airbus to compete, hence EASA…….. After all a German Aircraft would fly in UK airspace and vise versa, and neither would fall out of the sky considering they both had different specs……………That is the good bit.

Bad part of of all this was that to Standardise all European Countries into one agency you need to standardise the quality of the countries aviation authorities.. sounds simple, BUT to bring all countries up to say the German or UK CAA standards ( some of the best in the world at the time) is hard to do in a time period, so all of the countries were dumbed down to the lowest standard with the hope that they would all rise together…….. might sound good, but I sat amending manuals and throwing out literally books full of Airworthiness directives that had been written to address safety issues……. not what one would call a clever move really, however we are still here and they haven’t been dropping out of the sky like flies, so it appears to have worked…. which brings me back to

I am not saying that the CAA approach is ideal in all circumstances but from their point of view it is probably the most expedient particularly as vintage aircraft represent a very small part of the CAA workload.

Actually if you remove EASA work from the equation, most of the pure CAA work in Annex 2 aircraft is actually Warbirds and Vintage types, as we as said above no longer tend to build new aircraft, so we no longer have design authority for any new types as such in the UK which would fall under the CAA’s remit.

WJ244 you hit the nail in one 🙂

Fascinating discussion.

I think it is entirely correct that any national aviation agency should want proper paperwork and testing or stress calculations for any structural mod. It is all very well beefing up an apparent weak area but this can simply move the problem elsewhere.
I know this is from the car world but it is a good example.
Some (if not all) Lotus Elans have problems because there is a rubber coupling in the drive train which came from a standard production car (Ford I think). A combination of increased power output from the uprated engines and the fact that Elan owners tended to drive harder than the average family saloon driver meant that the rubber coupling had to be replaced regularly so someone designed a beefed up joint. This cured the problem but then owners found that it was comparatively easy to tie knots in the half shafts if they were a bit over enthusiastic so someone made up bigger diameter halfshafts which meant that they then cracked the axle mounts. A beefed up the axle mount kit was made and some owners then found they were cracking rear axle castings. Solution -drive with a slightly lighter right foot!
Not such a serious chain of events on the ground but if this had happened on an aircraft the implications could have been far more serious.

Yes, on the other rolled over low back Griffon (NH799), Frame 11 stayed intact and stopped the pilot suffering a fatal accident.

I suspect the Swedish accident had more to do with a soft runway, where Frame 11 dug in and sank, than the issue with the tail giving way. Possibly both.

Every accident is different; you cant legislate to prevent every one of them!

Bruce

That is modifications, NOT construction techniques which is how the Airframe is put together.

ok then, Spitfires assembled with AN rivets, does that count?

Spitfires do have a rollover bar.It,s called Frame 11.

If you want to build aircraft that are safer with better flying characteristics than the original why bother to rebuild ‘original’ aircraft at all?? Surely the idea is to build something that replicates the original rather than build something that looks like but has no feeling of what the original would have been like??

Have you ever thought why there is no aircraft manufacturing [Airbus/helicopter sub contracting excepted] in the UK????

The world has moved on from the CAA ideas on most things…

It was purely paperwork, there was nothing wrong with the work that was done from a safety standpoint. Those guys aren’t in the business of doing shoddy, substandard work. Basically the CAA were just pissed they weren’t consulted & didn’t get to charge a heap of money for bits of paper with stamps & signatures on them.

….apparently

Yes, no paperwork to substantiate the work that had been done during their history…….. Hence unairworthy, that is basics 101 and unforgivable, has squat to do with

didn’t get to charge a heap of money for bits of paper with stamps & signatures on them.

without tracibility you do not know item lives or what is on the aircraft, that is a serious failing from “a safety standpoint” if you cannot trust the paperwork to reflect the state of play of the Aircraft and any lifed components, what can you trust? ….
Err as for the CAA, wasn’t it something about the Company calling them in about others and it backfiring, that was the rumour.

& that’s where the US is streets ahead of the UK because we have Experimental & Restricted category etc. That’s how you get to fly around in something like a Bearcat that has air conditioning from a Chevy Suburban to keep the pilot cool. Hasn’t been installed in the Tigercat yet tho.

That is modifications, NOT construction techniques which is how the Airframe is put together.

Take the fleet grounded at a famous Warbird base, that was due to materials issues I believe, with no paperwork existing to back up the work both sides of the pond either and in my eyes was the right thing to do.

It was purely paperwork, there was nothing wrong with the work that was done from a safety standpoint. Those guys aren’t in the business of doing shoddy, substandard work. Basically the CAA were just pissed they weren’t consulted & didn’t get to charge a heap of money for bits of paper with stamps & signatures on them.

….apparently 😉

You mention construction techniques, I can not think of ANY aircraft that will allow you to deviate from the original manufacturers laid down methods.

Comments Welcome 🙂

& that’s where the US is streets ahead of the UK because we have Experimental & Restricted category etc. That’s how you get to fly around in something like a Bearcat that has air conditioning from a Chevy Suburban to keep the pilot cool. Hasn’t been installed in the Tigercat yet tho.

and an accident involving a Sea Fury had a similar effect when the cockpit structure couldn’t keep the a/c high enough from the ground when it turned turtle.

Actually the problem there was asthetics not design, in Service the Sea Fury had a roll over bar behind the seat to prevent this type of tragedy, unfortunately most owners chose to remove them, thus the accident was waiting to happen.

From the AAIB report

It is understood that prior to its import into the UK from the USA, this aircraft had been modified to
remove protective structures installed by the manufacturer immediately behind the pilot’s station,
and which historically have provided pilots with a measure of protection during turn-over type
accidents. This was apparently done in order make space available for the installation of a jump
seat behind the pilot, within the original canopy glazing, allowing a passenger to be carried. A
similarly modified aircraft suffered a fatal landing accident in similar circumstances in the United
States during 1996. However, in both accidents, the aircraft came to rest inverted on unprepared
surfaces and the effectiveness of such a protective structure in these circumstances is not proven.

http://www.aaib.gov.uk/cms_resources.cfm?file=/dft_avsafety_pdf_500974.pdf

So it may or may not have been survivable.

Taking fuel tanks as an example, at what point would it be acceptable to install self sealing tanks to reduce the risk of fire during an accident.

Most Warbirds have them……….. most Civi light Aircraft do not, but again how many Warbirds have been destroyed by being engulfed in fire….. yes in crashes they do, but to be totally honest, the G-forces incurred in the impact would probably have you knocking on the Pearly Gates long before the tanks rupture, and self sealing tanks are designed to seal the likes of rounds going through them, not 200 ft of tarmac.

Should an independent aviation body be established that has the ability to asses the merits of design alternatives with a view to reducing bureaucracy and improving the latent safety of historic types?

NO.. how the hell does adding another layer of bureaucracy reduce it….. end of the day the CAA laid down in Parliament by an act of law are responsible for Annex 2 aircraft.
You keep mentioning safety of historic types, where is there a problem? If you were to do a percentage of GA to fleet numbers and also Warbirds, I bet the Warbirds would have a lower accident rate.

Are safety authorities guilty of maintaining lower safety standards than can be economically achieved, in a bid to save themselves the bother of trying to understand whether a modification would be beneficial?

CAA involvement with Warbirds I would say from personal experience is higher than with GA. I as a C certing Engineer inspect, rebuild Aircraft, recommend ARC renewals and issue them without any physical involvement as such from the CAA bar my annual audit and with the Aircraft only being in theory looked at by the CAA every 9 years or so, it is done on trust, experience and myself being audited. On the other hand, Warbirds the CAA are involved and informed with everything.

UK regs appear to require such faithful replication of original construction and materials that it seems to exclude the benefits of modern knowledge, materials and construction techniques.

Again not true, Modern materials do get substituted in some cases where the original metal for example is no longer produced, but again this is strictly controlled as it needs to be or you would start going down the road of materials used not being up to the job… there is a lot of stress and design work that has to be done to satisfy the CAA before a material can be substituted……
I know the linen issue, but that is a lot to do with cost cutting at the end of the day and again, what next?, allowing one unapproved fabric material to be used, you would end up having someone doping on grannies surplus curtains, an extreme example I know, but one which I hope shows my take on the reasoning behind the decision.
If a proper mod was put through it may of been accepted as a replacement, but then again the original fabric is still available. True if it was available Mitchell may well of used it, but it wasn’t and he didn’t.
Take the fleet grounded at a famous Warbird base, that was due to materials issues I believe, with no paperwork existing to back up the work both sides of the pond either and in my eyes was the right thing to do.
You mention construction techniques, I can not think of ANY aircraft that will allow you to deviate from the original manufacturers laid down methods.

Comments Welcome 🙂

That is quite an emphatic reply. Care to elaborate?

That whole “irish linen” instead of Stitz farce for starters, Disc brakes on T6’s & Stearmans etc for another example..

I suspect that one of the problems may be the modern “sue everyone” culture so anyone who authorises modifications to the design of any vintage aircraft may well be the first in the firing line for court actions in the event of any mishap which injures people or damages property.
There is also the expense of testing modifications to ensure that they are safe.
I am not saying that the CAA approach is ideal in all circumstances but from their point of view it is probably the most expedient particularly as vintage aircraft represent a very small part of the CAA workload.

That is quite an emphatic reply. Care to elaborate?

Are safety authorities guilty of maintaining lower safety standards than can be economically achieved?

Yes.