Folding wings on British bombers

[Elmas]

From what I've read, the wingspan of British bombers was limited by the request of the Air Ministry that they could be serviced into existing hangars, and this somewhat limited their performance.

But, considering that recovering in hangars during the war was just every now and then, and most of servicing was made in open air, couldn't folding wings be installed, with not an unduly high effort and weight added, considering that at the tips bending moments and shear forces are quite limited?

I never understood why this was never done.

 

[A4K]

Not a techy, but I would imagine it would have had quite an impact on performance and bombload.

 

[KiwiBiggles]

The story about the wingspan of the Stirling being limited by hangar door size is a myth. In fact the standard RAF hangar at the time had a door width of 112 ft, 13 ft more than the Stirling span. And the Stirling specification called for outdoor servicing anyway (as was standard with British bombers).

 

[vikingBerserker]

It would also add additional weight.

 

[Shortround6]

This is actually one of the great myths of WWII aviation. Some RAF hangers had 120ft doors and the 100ft limit was an arbitrary limit imposed by the treasury dept. in an effort to keep plane size and thus cost down.
However once you designed a wing, making anything but the most minor modifications called for doing a whole crap load of new calculations and tests. The Halifax did get an extra 5ft 10 in on the MK III version but when you read the pilots notes there was a bit of fiddling with which fuel tanks got filled first depending on bomb-load and in some cases max bomb load meant the inner most tanks did not get filled in order to spread the load on both the Lancaster and Halifax (haven't read the Stirling manual).

SO it was the bean counters you had to convince, not the hanger makers or the aircraft manufacturers

 

[Robert Porter]

A young girl was watching her mother making a meatloaf, just prior to placing it into the oven she chopped off 2 inches from one end and set it aside. The young girl asked her Mom why she did that. The Mother replied, you know I have no real idea, it was something my Mother always did. So they called Grandma and asked her why she always chopped 2 inches off her meatloaf before baking it. She replied, I don't honestly know, my Mom always did that. So they called Great Grandma and asked her why she chopped 2 inches off her meatloaf before baking it. She replied because it would not fit in the small oven I had otherwise.

Moral of the story, sometimes things get repeated or carried on long after the necessity is gone.

 

[Shortround6]

HP V/1500

Wing Span 126ft, granted the wings folded.

Fairey Hendon

Wing Span 101 ft 9 in.

While the requirement/s for new bombers included servicing the aircraft in the open the idea of building all the new hangers that could not accommodated existing or future aircraft (within reason) would seem particularly short sighted.

 

[Elmas]

Of course, while you can easily clip wings (Spitfire, Zero…), a longer one with folding tips must be conceived, calculated and built with the whole airplane, generally, and it is not a modification that could be retrofitted ( but there are some bright examples to the contrary…)

The 100' door I think could have been the lower average of the British hangar: Military, from Napoleon to Mac Namara, from F-111 to F-35, always have been fascinated from standardization…

I can't really see why a folding wing like that the Grumman engineers designed for the Hellcat could not be fitted to the tips of a Lancaster, well outside the outer nacelles.

KISS! (Keep It Simple, Stupid!) was Kelly Johnson's motto and certainly a rule to follow when an airplane design is on the drawing board, but tell it to a crew who is struggling to climb those 1000' wich is the difference beetween to be shot down or to return safely home…

Reason can be simple: nobody tought to a similar solution and, if anyone tougth to it, was probably considered too expensive…

 

[stona]

The question of the 100' limit dates back to at least 1933 and the Fairey Hendon. A Wing Commander Williams, the Flying Operations 1 (FO1), reported that he saw difficulties with the Hendon's 101' 9" wingspan as it would not fit the RAF's 100' hangars. He suggested a redesign of the Hendon to a 97' wingspan. Air Commodore Mills, the Director of Organisation and Staff Duties (DOSD) pointed out that type 'A'hangars actually had 120' door openings, but that the small clearance which would be achieved at each wing tip (with a 97' span) for the old 100' hangars would be "insufficient for taking large aircraft through a doorway." His comment underlines the absurdity of claims that a 100' span limit was introduced with a view to getting large aircraft into hangar with a door opening of exactly the same size. The Deputy Chief of the Air Staff, then Ludlow-Hewitt, commented that he had seen a Hendon put on a "skate" and pushed sideways into a hangar with an 85' doorway, and suggested further investigation of this technique.

The 100' limit was introduced in 1936 simply to stop the aircraft getting too large. It was not an economic initiative. It was the result of concerns arising from the difficulty in handling two large transports built to C.16/28, which were deemed to unwieldy for ground handling.
Financially the Air Ministry worked on a bomb lift per pound (sterling) , for example in the ideal Bomber programme the equation was bomb lift per £20 million.
Once the bombers' targets were obviously going to be in Germany, rather than France which is a lot closer, an increase in size was accepted as inevitable.

The 100' limit was restated in the discussion of the B.1/35 bomber specification.

For the two 1936 bomber specifications (B.12/36 and P.13/36) hangar size was not an issue as the first paragraph of both specifications stated that

"Since it will be required to operate from bases anywhere in the world the aircraft must possess good facilities for maintenance in the open."

B.12/36 further specified that the engines must be easily and quickly replaceable "in the field."

Even more obviously in contradiction to any limit, even on ground handling, in October 1936 the Air Staff proposed that a development of the B.12/36 heavy bomber, with a wingspan not limited to 100' be included in the 1937 Experimental Aircraft Programme.

The myth of the 100' span probably dates to comments made by Barnes, in his book (1960s?) that Short Bros. wanted a 112' wingspan for the Stirling but that

"Unfortunately, before ordering any prototypes the Air Ministry stipulated that the span must not exceed 100', in order to conform to existing hangar dimensions."

This is certainly based on the preview of the requirement, though the final forms sent to Short Bros. included the same. The mention of hangars seems to have been the company's' interpretation, seen by Barnes, as the company sought, later, to justify the poor performance of the Stirling, particularly its low ceiling.

In their response to B.12/36 Short Bros designed a 99' wing with an aspect ratio of 6.71.
Mitchell, for the Supermarine types 316-318 designed first a 93' wing with an aspect ratio 6.97, later increased to 97' with a ratio of 6.93. Mitchell did not feel it necessary to exploit the full span limit set by the Ministry, despite a limitation on span potentially preventing a designer achieving an aspect ration high enough for the required ceiling and range (span squared is the critical parameter).

The major failing of the Stirling was nothing to do with the span limit and everything to do with a huge increase in weight as the design developed, even though the requirement to stress for catapult launch was removed in May 1938. In 1940, when the question of increasing the fuel capacity of the Stirling was being considered, it had grown so heavy that it was found that increasing the fuel capacity

"had no operational advantage since even with no bombs the weight of the aircraft plus normal military equipment exceeded the anticipated practicable operational all up weight."

One final thought. The Lancaster had a wingspan of just 102'.

Cheers

Steve

 

[Shortround6]

Some requirements were paid more attention to than others.

and of course ground crews could improvise.

Working on a Stirling in the US in modern times would have a bevy of OSHA inspectors kneedeep in paper work for a week.
Spark plug change anyone?
Engine swap without a really big crane?

 

[stona]

You were always going to need a big crane to lower an engine from 20 odd feet above the ground. The point was to make the engine itself a sort of modular 'power egg' assembly that could be quickly and easily changed.
The same applied to other components of the aircraft. The 'Nightbombers' film shows the use of a crane to change the rear turret on a Lancaster.

Cheers

Steve

 

[KiwiBiggles]

Is that a postwar photo? The rear turret appears to have 2 50s rather than the usual 4 30s.

 

[Airframes]

The original film was made by W.Cdr Coussins in 1944. The Squadron concerned, based at Hemswell, Lincolnshire, where in the process of having the new .50 cal rear turret fitted.
The film was originally screened on British TV in the late 1970s or early '80's, and is now available on DVD, and well worth watching for the wealth of detail and unique colour footage of Lancaster Ops.

 

[A4K]

Would definitely agree there...great film. Downloadable on the net too (of course).

 

[dogsbody]

Is that a postwar photo? The rear turret appears to have 2 50s rather than the usual 4 30s.

It's a Rose-Rice turret.

Rose turret - Wikipedia

WWII Aviation Novels - Caird Publications > Scrap Book > Rose Turret


Chris

 

[Graeme]

The myth of the 100' span probably dates to comments made by Barnes, in his book (1960s?) that Short Bros. wanted a 112' wingspan for the Stirling but that

"Unfortunately, before ordering any prototypes the Air Ministry stipulated that the span must not exceed 100', in order to conform to existing hangar dimensions."

And sadly repeated in the revised 1989 edition...

 

[stona]

As far as I know the first direct link between hangar door entry width and wingspan was made by Barnes, but I might be wrong. It may even have been a common misconception both at the time and when Barnes first wrote it. It is quite possible that in the RAF those who didn't know better made an erroneous connection between a wingspan limit and the size of the hangars on their aerodromes.
Short Bros. may even have made the connection deliberately in the face of the poor performance of the Stirling, Barnes would have had access to the companies records, but this is just conjecture. Unfortunately for the company the wingspan was not the root cause of the poor performance.
There is not really any excuse to continue repeating it when there is plenty of evidence that no such connection existed.
Cheers
Steve

 

[stona]

In sympathy with Barnes, when the then FO1 (Maund) saw the Handley Page prototype to C.16/28, with its 115' wingspan, he did suggest that it would give problems with ground handling, transport of spares and hangars. He also commented

"As these machines are required exclusively for use abroad where facilities are limited, these difficulties become accentuated."

Still the wingspan relationship to hangar size was not the reason for the limit imposed in subsequent Air Ministry specifications, I very much doubt that there was much large hangarage available at most overseas aerodromes, but it obviously was a concern to Maund, looking at a huge biplane with a 115' span.
The fact remains that whilst the 100' limit still applied to the 1936 bomber specifications it was lifted in 1937.

The problem with the Stirling wingspan has a convoluted history. Short Bros. were not initially invited to tender for B.12/36. Only Armstrong Whitworth, Bristol, Vickers and Handley Page were invited to tender, in July 1936. Shorts were only included when it was found that they already had a design on the drawing board which met many of the requirements of B.12/36, though this design had a 112' wingspan. Shorts indicated that they had ample design facilities to cope with the project and also production facilities as they amalgamated with Harland and Wolff. The initial Dagger powered Short submission, in September 1936, still retained the wider wingspan which did not meet the specification and was criticised for this among other failings. It wasn't until April 1937 that a much revised design was submitted, this time with a 102' wingspan (the same as the Lancaster would have) and it was this design which was selected as a back up to the Supermarine bomber. The reduction to 99' something (I haven't looked it up) came later but by this time the 100' limit had been more or less abandoned.

Cheers

Steve

 

[Robert Porter]

Just to clarify, is an "invitation to tender" similar to what we in the states call an RFP or Request for Proposal? From the reading I have done during the lead up to the war there were many times when a company submitted proposals even though they had not been invited to do so, with varying results. Sometimes their submissions were straight out thrown away, other times they actually got a hearing, and in a very few cases they won the proposal. I would guess that it was the same or similar in the UK?

 

[stona]

I think the two systems, US and British, were very similar.
In the case of the Stirling the firms I listed were initially invited to tender, followed by Short Bros. Boulton Paul were told that they would also be invited to submit their ideas later, though they didn't eventually tender.
The specification was then widely circulated in the aircraft industry, mainly for information, only the companies invited to tender were expected to respond.
In October 1936 the various tenders from the five companies, including Short Bros. were considered by the Air Ministry. Only Short Bros. and Supermarine offered entirely new designs, all the others based their tender on existing types (Wellington, Blenheim, Whitley).
Cheers
Steve

Edit: Supermarine tendered under the Vickers request. Vickers Armstrongs had taken over Supermarine in 1928.