Last updated: 11 July 2016, 13:03
Load limits of a De Havilland DH6



Considerable doubt has been expressed about the Squadron’s ability to mount bomb attacks on U-boats whilst at the same time having an Observer on board, due to the very limited weight-carrying capability of the DH6. It was, after all, a design originally conceived as an unarmed basic trainer. The following is an attempt to resolve the issue:

Weight limits (RAF-1A engine):Limiting value:Info Source:
Empty weight when built as a two-seater:1460 lbJackson, 1978 [1]
Maximum all-up weight:2027 lbJackson, 1978
Payload:567 lbCalculated from the above
Some 2-seat DH6 aircraft were fitted with Curtiss OX-5 engines. That variant had a lower payload limit. (Jackson, 1978)
Armament:
Bomb type carried when armed:100 lbPatrol Reports [2]
Fuel:
Fuel consumption:Max. 9 gallons/hourThe Vintage Aviator
Endurance:2¾ hoursJackson, 1978
Calculated fuel tank size:24.75 gallonsCalculated from the above, assumes no reserve
Quoted fuel tank size:26 gallonsJane’s Fighting Aircraft of World War One [3]
Specific Gravity of petrol (approx.):0.75 × that of waterThe Engineering Toolbox [4]
Weight of fuel at take-off (full tank):195 lbCalculated from the above
Shortcut / Cross-check:
Quoted disposable load apart from fuel:360 lbJane’s Fighting Aircraft of World War One [3]
Crew:
Pilot’s weight, clothed for open cockpit:(Say) 175 lbThe figure of 175 lb is the 1990 FAA standard figure for "noncombat-equipped" male military personnel travelling as passengers without hand baggage. [5]
Observer’s weight, similarly dressed:(Say) 175 lb


This appears to confirm that the Squadron’s aircraft could carry either a bomb or an Observer but not both...
Fuel + Pilot + Observer = 545 lb, leaving at most a margin of 22 lb – too little for a bomb.
Fuel + Pilot + Bomb = 470 lb, leaving at most a margin of 97 lb – too little for an Observer.
So were their missions realistic? Maybe. The deterrent effect of frequent inshore patrols caused U-boats to curtail their activities, forcing them to submerge at times when it would have been more effective to be running on the surface. This was achieved by the DH6’s mere presence, without a shot being fired or a bomb being dropped. Hence the term "scarecrow patrols". In the process, lessons were learned regarding the need for radio communication and a worthwhile strike capability, even aboard inshore spotter aircraft. Additionally, the whole DH6 operation at RAF Pembroke may have had another motive – a way of employing aircrew and mechanics most of whom were medically unfit for active service on the front line in continental Europe.[6]


Missed lessons for the future

Between the wars the RAF High Command apparently failed to appreciate that land-based aircraft could function perfectly well in an active role over the sea. No long-range maritime reconnaissance design emerged – nothing equivalent to the German Focke-Wulf Fw.200 Condor, the civilian version of which flew non-stop from Berlin to New York in 1938, or the Junkers Ju.290A-5 (theoretical range limit 6150km). Both were eclipsed by the wartime derivative of the 290, the Junkers Ju.390V2, which had a range of 9700km but never entered service with the Luftwaffe in great numbers.[7]

Between the wars, the RAF instead expanded the Flying Boat concept, most notably in the form of the Short Sunderland. The Sunderland was a robust aircraft but it suffered from three inadequacies – limited range, inability to use conventional airfields and an operational ban forbidding routine landing on the open ocean (thus it could only land on / take off from sheltered water such as lakes, major rivers or estuaries).

At the outbreak of WWII, what had by then become Coastal Command found itself with a flying boat unable to close the mid-Atlantic gap when on anti-submarine patrols, plus a motley collection of obsolescent land-based aircraft no more suited to a maritime role than the DH6 had been over 20 years previously.

Come 1940, No.255 Squadron’s historical roots in coastal patrolling were broken, its RNAS origins ignored. When the squadron re-formed in WWII it did so as a night fighter unit having no connection with Coastal Command. Poor procurement of maritime patrol aircraft was no longer 255’s concern. How different the squadron’s subsequent history might have been had the right equipment been available to facilitate a meaningful return to its roots!

Arguably no British-designed aircraft would fill the long-range patrol niche until 1951, with the arrival of the Avro Shackleton – a much-loved if rather noisy aircraft affectionately described as "10,000 loose rivets flying in close formation". It was a surprising omission, considering Britain’s heritage as a maritime nation, and an inadequacy that surfaced again with the cancellation of the BAE Systems Nimrod MRA4 project in 2010.[8]
We shall not fail or falter; we shall not weaken or tire. Neither the sudden shock of battle, nor the long-drawn trials of vigilance and exertion will wear us down. Give us the tools, and we will finish the job.

Winston Spencer Churchill,  broadcast on 9 February 1941
But without the right tools? Secure defence of the realm depends upon sound and timely procurement. One hundred years on from the start of World War One and fifty years on from Churchill’s death, it seemed that the lesson had yet to be learned. Even now, the procurement gap relating to current needs for a maritime patrol capability will not be closed until delivery of the new P-8A Poseidon aircraft announced at the Farnborough Air Show on 11 July 2016.[9]



Citations and Footnotes

Click on the ^ symbol to return to the text you were reading.

1. ^ Jackson, A.J. (1978). De Havilland Aircraft since 1909 (2nd Edition). London : Putnam, p.92.  ISBN 978-0-370-30022-1.
2. ^ TNA : AIR1/485/15/312/269 folio 100 and TNA : AIR1/419/15/245/1 folio 518. Original documents; both require a TNA Readers Ticket to view.
3. ^ Taylor, M. (1990). Jane’s Fighting Aircraft of World War One. London : Studio Editions, p.42. ISBN 1-85170-347-0. The original of this work (1919) was edited by Grey, C.G., following the early death at age 50 of John Fredrick Thomas Jane (1865–1916) after whom the Jane’s series of reference works is named. References quoted here relate to the 1990 reprint.
4. ^ The Engineering Toolbox.
5. ^ Federal Aviation Authority document AC120-27C[B] dated 25 October 1990, Section 11a. (Page 17/32 of the .pdf file).
6. ^ Phillips, A. (2010). Defending Wales. Stroud : Amberley Publishing. p.60.  ISBN 978-1-84868-845-2.
7. ^ All data regarding German aircraft from the website U-boat.net.
8. ^ Campbell, J. (2013). Royal Air Force Coastal Command. Cirencester : Memoirs Publishing. Epilogue, section 10, p.555.  ISBN 978-1-909544-73-4.
9. ^ http://www.bbc.co.uk/news/business-36763212







Copyright © 2014–2017.  All rights reserved except where otherwise stated.



Unicode logo (1896 bytes). W3C code verification logo (1894 bytes).