RE: De Havilland Tiger Moth: PH Heroes

[Lowtimer]

RoverP6B said:

I believe they may also have been built at sites other than Hatfield and Cowley: I've an idea I read that both Airspeed at Christchurch and DH at Hawarden built some...

Dunno about Airspeed doing Moths, but I suppose anything's possible in wartime. They did make some Mosquitoes.

In addition to the (mainly Cowley) UK production, the Tiger Moth was produced outside the UK in Canada, Australia, NZ, Sweden, Norway and Portgual. There's a lot to be said for the tailwheel, revised undercarriage geo, and brake mods introduced in Canada, and indeed the heater and canopy if you're having to fly through the winter (though at that stage I suppose you might as well go all the way to the next level of modernity and have a Chipmunk).

[2xChevrons]

Lowtimer said:

There's a lot to be said for the tailwheel, revised undercarriage geo, and brake mods introduced in Canada, and indeed the heater and canopy if you're having to fly through the winter (though at that stage I suppose you might as well go all the way to the next level of modernity and have a Chipmunk).

I mean, that' s pretty much what the Canadians did, surely ? With the Chipmunk being a DHC design rather than from DH at Hatfield. The Canadian Moth is very much the half-way point between license-building Tiger Moths and DHC's first home-brewed design.

[Eric Mc]

Lowtimer said:

Dunno about Airspeed doing Moths, but I suppose anything's possible in wartime. They did make some Mosquitoes.

In addition to the (mainly Cowley) UK production, the Tiger Moth was produced outside the UK in Canada, Australia, NZ, Sweden, Norway and Portgual. There's a lot to be said for the tailwheel, revised undercarriage geo, and brake mods introduced in Canada, and indeed the heater and canopy if you're having to fly through the winter (though at that stage I suppose you might as well go all the way to the next level of modernity and have a Chipmunk).

Airspeed was a subsidiary of de Havilland. Arthur Hagg, who designed the Airspeed Ambassador airliner, also designed the lovely DH91 Albatros.

[Lowtimer]

2xChevrons said:

I mean, that' s pretty much what the Canadians did, surely ? With the Chipmunk being a DHC design rather than from DH at Hatfield. The Canadian Moth is very much the half-way point between license-building Tiger Moths and DHC's first home-brewed design.

Hmm... well.. there's zero commonality between the two designs apart from the basic engine, and the fact that the first Chipmunk prototype has a few ex TIger Moth instruments and minor cockpit controls scattered around it, so maybe a very small stepping stone rather than a half-way mark. Chipmunks are lovely though so any excuse to talk about them.

Fun fact, related to the "trainers should not be too easy to fly" point made earlier: the Chipmunk has a few degrees of sidethrust built into its engine mount, like a lot of piston singles, but applied the wrong way, so make the yaw-axis swing with power variations worse rather than better. The assumption was that people woud be going on via Harvard class aircraft to various big tailwheel piston-engined types in operational service. This was at best an obsolescent assumption as by then the jet age was getting into full swing, and quite soon the RAF entered its ab-initio all-jet training phase with the JP. But as a method for forcing people to use their feet properly from lesson one, it certainly works.

[Ayahuasca]

I get that if the engine has £30,000 worth of maintenance every 1,500 hours it is probably pretty reliable.

But how reliable is 80 year old wooden main spar?

[Eric Mc]

When is the last time you heard of a Tiger Moth suffering significant structural failure?

[Lowtimer]

I'm much less anxious about 80 year old wooden components than about old metal ones, because any problems with teh wooden components are much more likely to be visible to inspection using your eyes and hands, whereas problems with metal are often detectable ony with highly specialised NDT regimes. And wood, unlike metal, doesn't fatigue. So metal components tend to have hourly or duty cycle lives, whereas wood can carry on indefinitely if stored and used correctly.

So what you're looking for on a wooden aircraft structure during inspection, and especially when you are re-covering it, is things like: glue failure, insect infestation, hard-to-spot damage caused by impacts like people whacking the wings into the hangar doors and not reporting it, and damp leading to rot etc. Providing you are okay from those points of view then your wooden components carry on in service, and safely.

Poor environment leading to glue failure was the big killer of wooden aircraft after WW2. We have much better adhesives now. But you still don't leave wooden aeroplanes outside overnight, if you want them to have long and happy lives. The ability to park them outdoors is the main practical advantage of metal and composite structures.

There have been Tiger Moth wing failures in recent history but those are down to the metal components rather than the wooden ones, especially the 'lifed' metal tie-rods - more info here:
http://www.dhmothclub.co.uk/msr/78Btierodsnuts.htm...

[Lowtimer]

Eric Mc said:

When is the last time you heard of a Tiger Moth suffering significant structural failure?

2013
https://www.atsb.gov.au/publications/investigation...

Edited by Lowtimer on Friday 17th August 08:21

[aeropilot]

Ayahuasca said:

But how reliable is 80 year old wooden main spar?

I bet there aren't that many (if any?) still flying with original spars............

[Eric Mc]

Lowtimer said:

2013
https://www.atsb.gov.au/publications/investigation...

Edited by Lowtimer on Friday 17th August 08:21

One - any more?

[Lowtimer]

Yes, there were earlier tie rod failures, fortunately (as far as I know) caught before they caused fatalities.
http://www.dhmothclub.co.uk/tns/tns29.htm

For context, for all light aircraft, structural failure attributable to design or manufacturing issues is extremely rare. Breakage because of a previous external impact, or the aeroplane being overstressed by pilot error, are far more common.

[Gliaviate]

An excellent thread, thank you. When I am towing a glider trailer, the value of the machine behind the towbar normally exceeds what is in front of it by a factor of at least four to one!

[Yertis]

Lowtimer said:

But you still don't leave wooden aeroplanes outside overnight, if you want them to have long and happy lives. The ability to park them outdoors is the main practical advantage of metal and composite structures.

In the war, did they move Mosquitoes into hangers every night? Or just work on the basis that they wouldn't be lasting all that long anyway.

[eharding]

Eric Mc said:

When is the last time you heard of a Tiger Moth suffering significant structural failure?

I know a chap at Waltham who had an absolutely beautiful Tiger Moth which he flew all over the country, but which eventually suffered from having the wings fall off - granted, that was on account of him misjudging the gap between some trees at a farm strip he was visiting rather than a fatigue issue.

He was fine, apart from suffering a degree of disappointment and vexation when the aircraft came to rest and realising that a significant amount of the structure was no longer attached.

[Eric Mc]

Lowtimer said:

Yes, there were earlier tie rod failures, fortunately (as far as I know) caught before they caused fatalities.
http://www.dhmothclub.co.uk/tns/tns29.htm

For context, for all light aircraft, structural failure attributable to design or manufacturing issues is extremely rare. Breakage because of a previous external impact, or the aeroplane being overstressed by pilot error, are far more common.

Only a few weeks ago a wing broke off a PA-28 Cherokee at a flying school - with two fatalities.

[Eric Mc]

Yertis said:

In the war, did they move Mosquitoes into hangers every night? Or just work on the basis that they wouldn't be lasting all that long anyway.

In World War 2, aircraft were generally stored outside and were only hanagared for maintenance and servicing. Even some servicing was done outdoors.

Famous aviation writer Bill Gunston once said that de Havilland hardly built a design that did not have some structural issues. Although I would say that, overall, the Tiger Moth was not one of them.

[Lowtimer]

Eric Mc said:

Only a few weeks ago a wing broke off a PA-28 Cherokee at a flying school - with two fatalities.

When you know what the cause was be sure to let us know.

[Lowtimer]

Yertis said:

In the war, did they move Mosquitoes into hangers every night? Or just work on the basis that they wouldn't be lasting all that long anyway.

Not routinely during the two and a half years they served during war in the European theatre (and as you imply few individual examples served for all of that time anyway), but the smaller number in service post-war were given more considerate treatment. . The type had to be withdrawn from operations in 1944 in the Far East due to a series of structural failures caused by exposure to the weather.

The UK airworthiness authorities got into a mighty paddy in about 1957 about wooden airframes, and imposed a number of onerous conditions on ther operation. This was based on some cases of glue joint failures relating to the adhesives used pre-war and during WW2 production, and many in the vintage aviation community regard the severity of the measures as excessive and not paying adequate regard to the actual condition and life experience of individual aircraft. It led to most of the UK's wooden aeroplanes being scrapped between 1957 and the early 1960s, which is why so few of the many of the excellent Miles and Percival types survive today.

Far better adhesives have been in use since those times.

Edited by Lowtimer on Friday 17th August 18:32

[Ayahuasca]

Always thought the American equivalent looked a bit more robust. I think if I had to buy a WWII biplane trainer it would be the Boeing.



Then again, the Tiger Moth is beautiful..

[GliderRider]

On the basis that a passenger in an aeroplane must do whatever the captain requests, my father proposed to my mother at the top of a loop in this Tiger Moth. Fortunately for me, she said 'Yes'.