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Valiant Tankers

Old 31st Jan 2013, 20:33
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ExNomad, that is exactly what I heard. In that respect the Valiant was just too early and too unlucky.
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Old 31st Jan 2013, 23:07
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PN: It's neither here nor there after all these years but, since you ask, there was an Argosy squadron (No 215 Sqn) based for some years at Changi, so deployment of UK or Aden based aircraft was hardly needed. As to why there was a refuelling trial with the aircraft, I've no idea, and AAR was no part of the force repertoire. "Because it was there," perhaps?
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Old 1st Feb 2013, 00:27
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The Valiant should have been scrapped in 1956

The trouble with British Aircraft pre 1956 (including the Valiant) was the double whammy of building aircraft with a design method that could not guarantee safety in a catastrophic failure [Safe Life] with materials [like DTD683] that could fail catastrophically. This fact was coupled with the fact that not all the metallurgical data was known when these aircraft entered service, for example it wasn't known until 1968 (4 years after the Valiant was scrapped) that for DTD 683, water or water vapour increased crack growth rates by a factor of 10. This was due to the Oxygen in the water rapidly oxidising the "fresh" aluminium releasing Hydrogen at high pressure which was enough to cause the crack to grow exposing more un-oxidised aluminium so producing more high pressure hydrogen and so on, in an auto-catalytic process.

Due to a lack of money cost cutting methods like using samples that had already been used in a stress test to measure fatigue strength led to an over estimation of the fatigue strength of a material by a factor of up to 100. This was due to the fact that pre-stressing these materials increased their fatigue strength. (See Section 4 para 2 of this ARC Paper). In fact this method (pre stressing) was used in a failed attempt to improve fatigue resistance.

This was aggravated by the lack of consideration for fatigue failure which was rare in the older materials.

DTD683 was known to be a troublesome material at least as early as 1951. Here is Mr Gardner of Vickers explaining the problems

structural problems | flight structural | structural efficiency | 1951 | 2503 | Flight Archive


Mr. Gardner then turned to a consideration of materials, first
touching on the newer aluminium-zinc-magnesium alloys,
D.T.D. 363 and D.T.D. 683, which, used as extrusions and
forgings, made appreciable weight-saving possible.

two difficulties had arisen: (a) distortion after machining, and
(b) variation of strength across the section. The distortion problem
with this alloy had become of general importance...

... this was an unsatisfactory aspect of the new alloy.
The second effect, which gave low core properties, was one which
needed to be known before design-values for the material were
agreed.
And Mr Black of Vickers Supermarine in 1953

light alloys | cold bending | permanent distortion | 1953 | 0935 | Flight Archive

The alloys considered were those
of specifications D.T.D. 363A and D.T.D. 683....

Mr. Black stated, the increased strength
of the materials was accompanied by a lowering of ductility as
measured by the elongation obtained from a tensile test. A low
elongation value was undoubtedly undesirable in an aircraft
material, because only small amounts of permanent distortion
could take place before a fracture occurred, and large amounts of
cold work could not be withstood without fracture.

... the alloys had a reduced capacity to
absorb permanent distortion, a low ductility and a low ratio of
fatigue strength to tensile strength ...

... a high normal stress level in use, and the result was a
greatly increased sensitivity to stress concentrations resulting
from bad design or surface notches ...

... residual internal stress would reach a high level, and was very undesirable.
So the problems were well known, but instead of giving up with the materials they soldiered on thinking the problems were 'solved' after all the Ministry of Supply told them they had to use this material and the UK Aircraft Industry was pretty arrogant about its ability to solve problems having produced war winners like the Spit' and Lanc'

But the Industry had not solved all the problems and it began to dawn in 1955 that their approach was flawed. This is well evidenced in the technical papers of the time available in the Aerade catalog. The research switches from attempts to improve fatigue resistance to research into understanding the process of crack formation, growth rates and ways to stop the failures from being catastrophic.

Airframe Fatigue 1955

On a comparative stress
basis, the new alloys such as DTD.363, 364 and 683 had no
better fatigue properties than the earlier alloys. Thus, for structures
of equal static strength, a reduction in fatigue life occurred,
and one example given by Rhode showed about a fivefold reduction
in fatigue life in transferring from 24 S-T to 75 S-T
(75 S-T is the American designation for DTD683)

The problem of working out a Safe Life was virtually impossible given the large scatter in the fatigue data

cycles | endurance limit | salt spray | 1955 | 0363 | Flight Archive
... tests on 57 specimens give lives ranging from 430,000 cycles to 117,423,000 cycles with a mean of 23,324,000; such results underline the magnitude of the problem ...
Things came to a head in 1956 with this lecture given by a Lockheed structures engineer to the RAeS
In it he delivers the "coup de grace" to Safe Life and states that DTD683 was the worst choice for fault tolerant structures

1956 | 0396 | Flight Archive

Putting this another way the big question is:

. . . . . . . . .. Laboratory (or predicted or recorded) life...
Safe Life = ------------------------------------------------------
.. . . . . . . . . . . . . . . . . . . . . ? .

On the determination of this ? factor hinges the adequacy of the
safe-life method.
Given the scatter in the data above, the nominator [Laboratory (or predicted or recorded) life] in the above equation was also largely guess work. Effectively the equation above becomes.
.. . . . . . . . . . ?
Safe Life = ----------
.. . . . . . . . . . ?

You don't need to be a mathematical genius to see the problem using an equation like that to design 'safe' aeroplanes.

All of this was made even more problematic with the publication also in 1956, of this paper in the Journal of the Institute of Metals by a Birmingham metallurgist team, which condemns DTD683 as it was too unstable (hence the wide scatter in the data).

Journal of the Institute of Metals


Mr Gardner of Vickers had noted the unstable nature of the alloy in his 1951 lecture.

The lack of stability shown both in extrusions
and forgings was an unpleasant feature in production.
DTD683 was removed from use 3 years later; 1959, 5 years before the Valiant was. Its use post 1956 was limited to components in compression, such as under-carriage components.

In 1956 several things happened many Safe Life designs built with the new alloys were either scrapped or re-designed like the Argosy or Shackleton, but not the Valiant. Also in 1956 Vickers began flying a Valiant deliberately into turbulence they measured the strains and the experiments produced the disturbing result that the Valiant fleet had a remaining Safe Life of 70 hours, later revised to 300 hours (presumably under some pressure from MoD and Whitehall Mandarins). The problem with low flying was the increased frequency of gusts that would exceed the limits on the airframe. Exceeding the limits was potentially the initiating event for a later fatigue failure, as described in the Birmingham paper and as implied by Mr Black of Vickers Supermarine in his 1953 talk.

... only small amounts of permanent distortion could take place before a fracture occurred.
Also in 1956 Macmillan said the following in a memo to PM Eden about defence expenditure.
"When the story of the aeroplanes finally comes out it will be the greatest tragedy if not scandal in our history"
1956 was the year in which the Government launched a review of the Aircraft Industry, which later resulted in the industry's restructuring. The last 6 Valiants were cancelled in 1956.

According to Flight magazine (corroborated in Eric Morgan's book) only 50 of the 104 (108) Valiants were still in service when the scrapping order came in 1965. Using the (incomplete) data available the average life of a Valiant was 7.6 years with an average of just over 300 flying hours per year each.

In todays money (price of a Valiant in 1956 = ~500,000) and using a back of the envelope calculation, the cost to the Tax payer was ~154,000 per hour of Valiant flight time, that number excludes the actual running costs such as wages, fuel etc and just uses the rough purchase cost.

That was Macmillan's "scandal". The "tragedy" was the number of fatalities in non-combat accidents, which reached a peak of nearly 1 a day in 1954.


Last edited by RIHoward; 6th Feb 2013 at 14:58.
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Old 1st Feb 2013, 08:06
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RIH, a masterly treatise, thank you.

ICM, thank you too. I just think that the Air Box didn't really get its policy head around the concept of AAR. The USAF had it so we had to have it too. Of course modifying a few bomber types rather than building dedicated tankers like the KC97/KC135 was not the way we could afford as the V-force was sucking up most of the procurement money.

Equipping the Argosy and the VC10 was probably in case of rapid long range deployment but never enough tankers to do that.
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Old 2nd Feb 2013, 18:53
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Not understanding the metallurgy bit, but if it was a matter of age and not related to flying hours or cycles, I must ask, how was XD816 kept flying so long after the rest of the Valiant's were scrapped?

My understanding, until this forum came up, was that XD816 had been a hanger queen while it was at Boscome Down, and used as the model for the fitting of HDU's. And as such it had way below the number of flying hours of the rest of the Valiant fleet.

It definitely spent at least 6 years on 214 Sqdn from Feb 59 until Feb 65.
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Old 2nd Feb 2013, 19:13
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Ian, Feb 65 was pretty close to the end date. As I said, a couple of aircraft, I thought at Pershore but it may have included Boscombe, were sub-100 hours and it was hoped that they could fly on. When they did that last, for luck, safety check they discovered that they too were fatigued.

Despite the evidence laid out by RI Howard, there had been no whispers that there were problems.

Remember these were different times. It was the height of the cold war. Virtually anything to do with the super detergent was secret and the suggestion that a third of the force was unsafe would have been top secret, or at least treated as such.

Crews knew their chances were slim but hoped that their equipment would give them the best chance. There is no way that it would be admitted down at sqn level that the aircraft were death traps.

On the hangar queen aspects, that is to be expected for aircraft being used for experimental work. If the kit is not ready the aircraft would not fly.

Last edited by Pontius Navigator; 2nd Feb 2013 at 19:15.
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Old 2nd Feb 2013, 21:25
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Just for the record, the crew that were flying the Valiant on that fateful day were not aware of how close they had come to death as they clambered out of the aircraft. On levelling off rather sharply when practising a " failure to pressurise in the climb " drill they heard a loud bang and decided to return gently to Gaydon. Those of us that were waiting at the dispersal could see that the aircraft was making like a naval version with one wing ready to fold up. One very lucky crew and the end of my Valiant captains course'
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Old 2nd Feb 2013, 23:48
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Art, was that the sortie where the spar fracture had caused the wing to 'half-fold' so much that the flap motor spline drive disconnected on that side? I heard that the crew tried to lower flap and got an immediate uncommanded roll as it deployed assymetrically, but the pilot not flying was monitoring the flap gauges and called it immediately, resulting in 'flaps up' and a safe flapless landing.

RIH, thank you for the treatise on fatigue, I shall bookmark it for ever. I remember how the work of the late Harold Parish (at Huntings before Warton, where I knew him) and Alfred Payne in Australia, testing many wings to destruction, enabled WAP Fisher and Roland Heywood at RAE to establish successfully the safety factor(s) that had to be applied to the results of major fatigue tests to define the safe service life of an aircraft - and have given us structural confidence ever since. But I had assumed that all alloys were reasonably well-behaved and produced a comforting Gaussian distribution of fatigue cycles to failure. I am surprised the Valiant lasted as long as it did, and rather pleased that my attempt to get a trip in one at Marham (as an ATC cadet, not a chance!) came to nought.
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Old 3rd Feb 2013, 02:48
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Was the spar material DTD 683. The stress office where I worked had a chunk that had not been anywhere near an aircraft, but had turned into a all by itself purely on age.
Mind you, I have seen (long time ago now) a trailing spar of a Boeing 720B in a similar "crumbling cheese like mess", quite a sobering event given I had arrived at the maintenance base on that particular aircraft only the previous day. Granted the aircraft had quite some hours accrued, even so, sobering ! I took small package of the crumbs back with me to home base; more than a few of the people there first thought I was having them on !
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Old 3rd Feb 2013, 09:57
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XD816

Re the continued flying of XD816, it was allowed to continue flying without underwing tanks & being monitored very closely, the attached picture is from Abingdon (looking at it it might just be Filton ?????) & from memory after leaving the Jubilee "get together" did one last flight around the V bomber bases (saw it overfly Marham) before ending up at Filton, I think the info is correct but always glad to be corrected PH.
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Old 3rd Feb 2013, 11:14
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I am surprised they took the underwing tanks off. When we operated them there was always a proportional quantity of fuel kept in the underwings so as to relieve the wing root stresses. That practice was nothing to do with the Valiant's problem; it was normal large aircraft husbandry.
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Old 3rd Feb 2013, 11:34
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Not all Valiants were fitted with tanks. I do however have (in a book) a picture of 816 both with and without tanks. In the with tanks fit she also had a probe.

XD816, a B(K)1 was the last Valiant flying as it was undergoing a Ministry of Technology test programme.

According to the book, 816 flew on 28 Apr 1968 in a flypast to mark the disbandment of Bomber Command.
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Old 3rd Feb 2013, 16:11
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XD816

XD816 went from 214 Sqd Marham (underwing tanks removed prior to transit flight at Marham) to Wisley 18 August 1964 for trial installation of rear spar repair scheme under KD/P/198/CB.5(c). Loaned to BAC Wisley 21 September 1964, At Wisley from 1 April 1965 - 26 November 1965 for re-spar & flight trials at that time had completed 2,012.05 flying hours & 829 landings. On 29 June 1967 passed to control of BAC (Operating) Ltd for fatigue flight trials, MOD loaned aircraft for display at Abingdon 23 April 1968, finally SOC 26 August 1970. Hope fills in the gaps, PH
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Old 3rd Feb 2013, 17:00
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The underwing tanks could take a nominal 12,500 lbs of fuel each. Somewhere in my memory cells is a project by Vickers to mount two bomb carriers underneath the wings each containing 10/1,000 lb bombs.

It would have flown a reasonable distance; that would have left it with about 45,000 lbs; about 5 hrs flying with 30 mins reserve: 1,200 nm ROA.

It would have jumped a bit letting 41,000 lbs go.
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Old 3rd Feb 2013, 17:23
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Fareastdriver,
the Herc used to 'jump a bit' when dropping a triple ULLA (ultra low level airdrop ). That was 3x 14000lbs per platform ten feet above the DZ !
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Old 6th Feb 2013, 02:41
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Fitting refuelling equipment at 214 Sqdn

Found this pic in Profile Publications Number 66 "The Vickers Valiant" published in 1966



original copyright - Profile Publications Ltd (now dissolved) 1966

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Old 6th Feb 2013, 10:14
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Zetec,

Nice pic.
You can just see the Rebecca X aerials on the black paint in front of the windscreen. XD816 was one of 4 a/c to be fitted with Rebecca X. If I can
lay my hands on my notebook, I will confirm if it was one of the 2 fitted with Eureka X. I think it was but I cannot trust my memory these days

RIHoward,

That is a well used pic that I've seen many times. I recognise the faces and I've racked my brain for names, all to no avail.

PN,

Yep the end date of the Valiant and the end date of my service were very close together

Being an ex-Boy Entrant, my demob date was my birthday, which is in March. With demob and accumulated leave, I left the gates of Marham for the last time the 1st Friday in February 1965.

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Old 6th Feb 2013, 11:15
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Originally Posted by ian16th View Post
You can just see the Rebecca X aerials on the black paint in front of the windscreen. XD816 was one ofZ 4 a/c to be fitted with Rebecca X. If I can lay my hands on my notebook, I will confirm if it was one of the 2 fitted with Eureka X.
As Rebecca was the aircraft equipment and Eureka was the corresponding ground responder, are you saying that two of the aircraft were fitted with Eureka so as to act as formation leaders?

I was on one of Trial 541 sorties in Jan 1967 on the Vulcan when we tried out the A-A Tacan for low level blind formation flying trying out a conventional bombing trial. It involved 3 Vulcans at 15 second interval on one of the Libyan low level routes. The trial seemed to go well until it was analysed.

As lead we could intermittently see the range of either of the two followers. No 2 always seemed horribly close, often as close as half a mile. OTOH Nos 2 and 3 thought we were much further ahead of them.

While the tactic was never practised the scheme for a 4 aircraft laydown cross over attack at 30 second intervals was a published tactic. Now that would have made the eyes water.
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Old 6th Feb 2013, 12:20
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As Rebecca was the aircraft equipment and Eureka was the corresponding ground responder, are you saying that two of the aircraft were fitted with Eureka so as to act as formation leaders?
In the early 1960s, on 23 Sqn (Javelin 9R) I can remember taking part in air to air Rebecca/ Eureka trials with a Valiant tanker; IIRC it worked , but I can't remember what range we achieved.
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Old 6th Feb 2013, 14:44
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PN said:
As Rebecca was the aircraft equipment and Eureka was the corresponding ground responder, are you saying that two of the aircraft were fitted with Eureka so as to act as formation leaders?
Rebecca X/Eureka X was a unique system that we trialed for AAR.

Yes, Eureka was normally the ground transponder, but the MK X was a special from Marconi. It worked around 1000 Mc/s as opposed the 200 Mc/s of the 'normal' Rebecca/Eureka/DME. Whenever we had a fault, we took the kit to the Electronic Centre and did trouble shooting to the component level, and a report went to Marconi.

If you look closely at the pic of XD816 you can see the 3 'shark fin' aerials on the black painted part of the 'bonnet'. We also spread the story that when AAR receiving, they were 'sights' for hitting the drogue.

If the a/c was fitted with the Eureka X transponder, it had a similar single sharks fin aerial on the underside of the fuselage, immediatly forward of the Orange Putter tail warning Tx/Rx. As I said earlier, I do belive that XD816 was fitted with Eureka X and I think that the aerial is just visible on the picture posted. In the picture, no Orange Putter is fitted, just a white tail cone.

I left 214 in Oct 62 for 2 years in Akrotiri and I dunno how the trials ended. I rejoined the Sqdn in Oct 64, by then the Valiant's were flying in very restricted mode or grounded and I was more interested in getting started in civilian life. The good news was that with so little work to do, I had no trouble getting time off for job interviews.

Before going to Akrotiri, I had a jolly to Vickers at Hurn, where they had fitted the rack mounts and cables. I took a Eureka X set and test equipment to Hurn and fitted it, tested it and found it worked, so as a Cpl/Tech I signed a a document that meant that the RAF paid Vickers for their work! Oh the power

As a thank you they gave me a lunch and a tour of a rather special a/c that they were servicing, a Viscount that was owned by King Hussein of Jordan. It was fitted out just a little nicer than the Valiant's.

Happy Daze.
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