De Havilland Swallow - T-tail and bent wings

Kerrillc · February 02, 2011, 11:35:31 PM

I saw the Gloster Ghoul thread and saw the words DH 108 Swallow and then

I remembered THIS!

I am thinking either T-Tail or bending the wingtips, around 3 foot as per the Ghouls wings. In anyone's opinion does this sound feasible? I note that the instructions state categorically the wings should be 90 degrees to the fuselage, i.e. no dihedral. One does tend to wonder if this was the reason why the 108 was so dangerous. Does anyone in the group have any theories?

I have Eric Brown's autobiography "Wings On My Sleeve" and I read with interest his comments on the 108. But then again this is What If so anything can happen.

Cheers

Kerrill

kitnut617 · February 03, 2011, 06:22:49 AM

I've got one of those too, Kerrillc. My idea is to make a 'proof-of-concept' Sea Vixen out of it. If I was to do another I think a T-Tail would be the way to go though.

I've read somewhere that the design was to explore information captured from Messerschmitt about the Me.163, but it also said the accidents of the DH.108 was more to do with a structural deficiency not the design idea itself. The accidents happened when the aircraft went into an outside loop and the wings would just fold up. At least that's what I remember reading.

rickshaw · February 03, 2011, 07:02:16 AM

Quote from: kitnut617 on February 03, 2011, 06:22:49 AM
I've got one of those too, Kerrillc. My idea is to make a 'proof-of-concept' Sea Vixen out of it. If I was to do another I think a T-Tail would be the way to go though.

I've read somewhere that the design was to explore information captured from Messerschmitt about the Me.163, but it also said the accidents of the DH.108 was more to do with a structural deficiency not the design idea itself. The accidents happened when the aircraft went into an outside loop and the wings would just fold up. At least that's what I remember reading.

I thought Geoffrey de Havilland lost his life when he attempted a dive he couldn't pull out of in the Swallow?

Quote
While being used to evaluate handling characteristics at high-speed, on 27 September 1946 TG306 suffered a catastrophic structural failure that occurred in a dive from 10,000 ft (3,050 m) at Mach 0.9 and crashed in the Thames Estuary. The pilot, Geoffrey de Havilland Jr., was killed in the accident. Early wind tunnel testing had pointed to potentially dangerous flight behaviours, but pitch oscillation at high-speed had been unexpected. The subsequent accident investigation centred on a structural failure that occurred as air built up at Mach 0.9, pitching the aircraft into a shock stall that placed tremendous loads on the fuselage and wings. The main spar cracked at the roots with the wings immediately folding backwards.[7]

[Source: - http://en.wikipedia.org/wiki/De_Havilland_DH_108 ]

kitnut617 · February 03, 2011, 07:09:22 AM

Quote from: rickshaw on February 03, 2011, 07:02:16 AM
I thought Geoffrey de Havilland lost his life when he attempted a dive he couldn't pull out of in the Swallow?

Quote
While being used to evaluate handling characteristics at high-speed, on 27 September 1946 TG306 suffered a catastrophic structural failure that occurred in a dive from 10,000 ft (3,050 m) at Mach 0.9 and crashed in the Thames Estuary. The pilot, Geoffrey de Havilland Jr., was killed in the accident. Early wind tunnel testing had pointed to potentially dangerous flight behaviours, but pitch oscillation at high-speed had been unexpected. The subsequent accident investigation centred on a structural failure that occurred as air built up at Mach 0.9, pitching the aircraft into a shock stall that placed tremendous loads on the fuselage and wings. The main spar cracked at the roots with the wings immediately folding backwards.[7]
[Source: - http://en.wikipedia.org/wiki/De_Havilland_DH_108 ]

Yes, but during the investigation, they found that the wing failures had started at the top of the spars, not at the bottom which would have been the clue if he was trying to pull out of a dive. I think the maneuver is called a 'bunt' or something like that.

Doc Yo · February 03, 2011, 08:12:03 AM

I like both t-tails and bent/cranked wings, but I think the latter would be more elegant on the Swallow. If
you wanted to be really ambitious, you could crank the wings up at the root as well...say Professor Hill
came out of retirement...

PR19_Kit · February 03, 2011, 04:22:32 PM

Quote from: kitnut617 on February 03, 2011, 07:09:22 AM
Yes, but during the investigation, they found that the wing failures had started at the top of the spars, not at the bottom which would have been the clue if he was trying to pull out of a dive. I think the maneuver is called a 'bunt' or something like that.

Wasn't this one of the first instances of 'Mach Tuck' where the aircraft trims more and more nose down as it approaches sonic speed?

When it's not counteracted, either by stick movement or aerodynamic tweaks to the airframe in the first place, the result is exactly a 'bunt', an outside loop, or part of one anyway. When the G loadings exceed the design limits plus any safety factor, something has to give. In this case it was the wing structure.

kitnut617 · February 03, 2011, 05:36:06 PM

Quote from: PR19_Kit on February 03, 2011, 04:22:32 PM
Wasn't this one of the first instances of 'Mach Tuck' where the aircraft trims more and more nose down as it approaches sonic speed?

I think you're right Kit

Old Wombat · February 04, 2011, 06:40:15 AM

Do both, can't hurt.

Kerrillc · February 04, 2011, 07:12:36 AM

Okay I'm going to go for it!!

Kerrillc · February 13, 2011, 07:50:12 AM

Well I have started the preparations for the Swallow (I am refering to the variant as the DH108-B) I forsee much sanding and fettling in the future. I have been contemplating the wing mounting for the dihedral, so I can see the way to get the look I want.

I should have started this sooner but real life has got in the way with a vengeance!

I have also found that the white metal undercarriage legs are missing, wheels yes, front leg and wheel yes, port and starboard legs no.

Looks like this one's going to be in flying mode.

Cheers

Kerrill

pyro-manic · February 13, 2011, 08:17:56 AM

Vampire or Venom legs would work, I think? Someone (not me, unfortunately) will have spares, I'm sure.

kitnut617 · February 13, 2011, 08:21:45 AM

Quote from: Kerrillc on February 13, 2011, 07:50:12 AM

I have also found that the white metal undercarriage legs are missing, wheels yes, front leg and wheel yes, port and starboard legs no.

Cheers

Kerrill

You could try contacting Whirlybirds, their 2010 catalogue which I got from Telford, shows that it's available and it is the same kit.

Kerrillc · February 13, 2011, 08:29:44 AM

Ok Kitnut, thanks, I will do that quickly

Kerrillc · February 26, 2011, 01:57:58 AM

Just spoke to Whirlybird, I know I should have done it sooner but my working life has been interrupting my whif life!

Anyway I spoke to Mr Evans (not sure which one) and what a smashing chap, he's fairly certain he has some of the undercarriage legs and will send them to me. Deserves a mention in the Great Traders thread I think!

But I have a few things to deal with so its all a bit build interrupted, much to my discomfort, darn it!

Kerrill