Monday, October 14, 2013

David versus Goliath – Fairey Swordfish against the Bismarck 1941



A     As an introduction I'd like to pose the following question. What did the jeeps of
the 1st Airborne Reconnaissance Squadron have in common with the Fairey Swordfish
torpedo bombers which engaged the German battleship Bismarck in 1941? Answer:
They both were armed with a single .303 cal. Vickers “K”/VGO (Vickers Gas Operated)
machine gun. In the case of the Swordfish it was its sole defensive weapon. In addition
there was a single fixed forward firing .303 cal. Vickers machine gun.

The Fairey Swordfish was an anachronism, already obsolete in 1936, when it first
entered active service with the Fleet Air Arm of the Royal Navy. For that reason, if
none other, I thought it would be an appropriate subject of a blog page. The
“Stringbag” as it soon became affectionately referred in the fleet, became
revered in naval aviation history. Due to its decisive engagement in two major
naval battles of World War II, 73 years later there are at least four restored
examples which are still fully operational. One of which is LS 326, which is
maintained by the Royal Navy Historical Flight (RNHF). What is truly amazing is
that the Fairey Aircraft Co. Ltd., tendered ten designs (three monoplanes and seven
biplanes) in response to the Royal Navy’s Specification S.9/30. Had it not been for
the Admiralty’s ultra conservatism and abject recalcitrance, the Fairey Swordfish
rather than looking like this:

Fairey Swordfish Mk I Torpedo Bomber

 might have looked like this (similar to the Blackburn Skua).

Fairey Aircraft Project 'Scheme 9 and 10', proposed
alternate design configuration for the Swordfish 

The Swordfish’s renown was resuscitated with the making of the highly successful
movie, “Sink the Bismarck” in 1960, based on the book, “Last Nine Days of the
Bismarck” by C. S. Forester. Although probably best known for that action,
Swordfish aircraft had already been blooded in a long range attack on the Italian
Fleet in the harbor of Taranto, Italy on the night of 11 – 12 November 1940. The
background as well as the epic battle itself is chronicled in the following program; https://www.youtube.com/watch?v=N59MTv4z38A&t=9s%20.


There is no question (as indicated in the video) that the planning staff of the Imperial
Japanese Navy, specifically Admiral Isoruku Yamamoto, methodically absorbed every
aspect of the Royal Navy's attack. As cited, one critical detail was to modify the running
depth of their aerial torpedoes to run shallower. However one significant element of the
Royal Navy's attack, while fully recognized by Japanese Naval planners, failed in its
execution.
    
While a section of Swordfish had successfully conducted a planned bombing attack of
the Italian Navy fuel depot complex ashore, the Imperial Japanese Navy missed a critical
opportunity leaving the entire U.S. Navy fuel supply for the Pacific theatre of operations
totally unscathed. This was due to the fact that a planned second strike focused on dock-
yards, dry-docks, POL storage tanks, and remaining ships, was cancelled.

U.S. Naval Base Pearl Harbor, note proximity of the massive
fuel tank farm immediately to the left of the main channel and
"Battleship Row", October 1941 

A close-up of the U.S. Navy Submarine Base, Pearl Harbor,
better showing the fuel tank farm, October 1941 

It has been commonly held by a majority of naval historians that the attack on
Taranto played a singularly important role in the Japanese planning of  the attack
on the U.S. Pacific Fleet at Pearl Harbor in December 1941. However, while
agreeing it played a significant role, this author believes he has provided a strong
case that a U.S. naval exercise conducted in 1932, may have actually been the
primary element. See this blog at;
http://arnhemjhttp://arnhemjim.blogspot.com/p/military-strategy.html.


Classic Three-view of the Fairey Swordfish Mk I with
principal specifications


The following four drawings are a cutaway of the Fairey Swordfish MK II and the
cockpit of the aircraft. Apologies for the redundancy however the two part cutaway,
which was due to the size of the drawing, affords both better resolution of detail and
legibility.





On 26 May 1941, 818 Squadron, Fleet Air Arm, Royal Navy was embarked in HMS Ark Royal. At 1910 hours a 15 plane strike of Fairey Swordfish torpedo bombers was launched against the German battleship Bismarck. Four of the aircraft were from 818 Squadron.

In the first flight was Fairey Swordfish 5C, Serial No. L9726 piloted and crewed by:
     T/S-Lt John William Charlton Moffat, RNVR (P)
     T/S-Lt John Dawson Miller, RNNVR (O)
     LA Albert J. Hayman, RN Jx. 151230 (TAG)

On 26 May 1941 at 2105, the 18 in. aerial torpedo released by Sub-Lieutenant J.W.C. Moffat (5C) struck the extreme port stern of the target (Bismarck). This torpedo hit permanently jammed both rudders (12 deg. to port) in the Bismarck, directly contributing to its subsequent sinking by British battleships the next day.

For this feat you would think that he would have been awarded the Distinguished Service Cross, or at the very least the Distinguished Flying Cross. Such was not to to be the case, and it was only years after that research of  records of the engagement strongly indicated that it was his torpedo that had struck the stern of the Bismarck.

T/S-Lt John William Charlton Moffat RNVR

All aircraft carried the 18 in., RNTF MK XII Torpedo, with a dual speed setting of 43 or 48 mph, 3500 yd range, 388 lb. (TNT) warhead, and dual mode detonator (contact/magnetic influence). Following  photograph shows the "business end" of the torpedo, i.e. the "whiskers" of the contact fuze. Hitting any part of the whisker detonates the warhead.

18 in. RNTF MK XII Torpedo contact fuze

The target of 818 Squadron's attack: KMS Bismarck

The Achille's Heel of the Bismarck; Stern section
with rudders and propeller shafts - the recessed
area at the ship's freeboard marks the aft end of
the heavy side armor which is yet to be applied

The following photograph is of the Bismarck's FUMo 23 radar array co-mounted with an optical 10.5 meter base rangefinder (Basisgerät BG). It is not discernible in the contemporary color photograph of the ship previously shown. Explanation, possibly not yet installed, or intentionally obscured for security reasons.  

FUMo 23 Radar and Optical Rangefinder

The primary anti-aircraft armament consisted of 16 105mm SK C/33 mounts and 16 37mm SK C/30 mounts equally divided port and starboard. In addition there were 18 20mm Flak/MG C/38 and C/30 mounts.

In addition the Bismarck’s main armament, four turrets, each containing two 380mm SK C/34 naval guns, engaged the Swordfish, albeit also unsuccessfully.

Even the Bismarck's Secondary Battery, consisting of 6  turrets of twin 150mm guns designated SK C/28, also engaged the aircraft.

105mm SK C/33 Anti-Aircraft Mount

37mm SK C/30 Anti-Aircraft Mount

During my tenure at Honeywell Marine Systems Center I had the privilege of working with Gerhard "Jerry" DeWitz, who as a young engineer had been employed by Telefunken in Germany. He was a member of the design team which developed the first generation naval radar systems installed in the pocket battleship Graf Spee. Subsequently the Bismarck, battleship Tiripitz, cruiser Prince Eugen, and battlecruisers Scharnhorst and Gneisenau received radar systems of various designs and manufacturers.  He also had an extensive knowledge of the fire control computer systems employed in these ships. Called "predictors" by the British, gunfire control computers of the day were analog machines. Rather than even incorporating radio vacuum tubes, let alone transistors or circuit boards, they were electro-mechanical, incorporating a complex series of mechanical gear trains and cams which interacted with each other to provide critical parameters for laying of the guns. They integrated inputs from both range and height-finding telescopic optical instruments, as well as radar, when available. This included continuous incremental changes necessary to lead the target in train and elevation, and adjust for changes in target acceleration and de-acceleration, relative to the motion (in 3 axes) of own ship. It is analogous to shooting skeet with multiple rifles (not even shotguns) from a moving boat. When the Germans designed the fire control computers, they incorporated a model of aerodynamic characteristics consistent with the high performance aircraft of the day. (Spitfire Mk I - 355 mph, Messerschmitt Bf109E - 348 mph at comparable altitudes). Even given the Swordfish's slow top (139 mph) and stalling speeds, and exceptional maneuverability, its performance envelope was still within the capability of what were called the "Flak directors" installed in Bismarck.

As is usually the case, no single factor allowed the attacking aircraft to escape destruction from the combined firepower of the Bismarck's primary (105mm) and secondary (37mm and 20mm) anti-aircraft defense batteries. The following combination of factors contributed an overall synergistic effect:

• The Swordfish was a particularly forgiving aircraft affording the pilots the ability to approach at wave top level resulting in intermittently "masking" their return signal to the Bismarck's radar transmissions. Analogous to "terrain masking" used in the modern era. The Bismarck's FuMO 23 radar was capable of training on a target within 6 deg. bearing accuracy, and a range accuracy of 70 meters. However its display was a simple "A" scope barely able to track a single target at a time. It did not have a PPI (Plan Position Indicator, i.e. multiple target tracking capability).

• Given their head-on final run-in to target for torpedo launch the aircraft presented a minimum radar cross-section.

• Accurate radar guided anti-aircaft gunfire requires a continuous data stream injected into the fire control computer(s). This capability was only gained in the later FuMO 231 Euklid radar.

• The Bismarck's 4 main Flak directors were to have been triaxially stabilized, however due to a high level technical/economic exchange agreement with the Soviet Union, only the forward two were. The un-stabilized aft directors also may have had inferior computers and rangefinders.

• The rear 105mm Flak guns, while upgraded still had faults, one of which were firing cut-out cams which precluded sufficient depression necessary to engage low flying targets.

• The Bismarck's anti-aircraft gunnery crews had no actual combat experience, and only limited training, particularly in firing as coordinated batteries.

• Conversely the pilots and air crews of 818 and 810 Squadrons who attacked the Bismarck, while not engaged in the attack on Taranto, were not only well trained, but greatly benefited from the lessons learned by the Swordfish aircrews of 813, 815, 819, and 824 Squadrons who were in the attack.

As a combined result of all of these factors the pilots and air crew of  818 Squadron were able to press home their torpedo attack without the loss of a single aircraft directly attributed to the Bismarck's gunfire.

In addition to the video embedded below there is an excellent National Geographic special in which surviving air crew members are interviewed and contemporary combat film footage is shown. This can be found at; http://www.youtube.com/watch?v=z-leCeiWXFo.


There is another excellent link which details a chronological plot of the series of events
leading to the sinking of the Bismarck. It can be found at; http://www.bismarck-class.dk/bismarck/bismarck_menu.html For those who happen to go there, you
will discover this is only a small segment of an extensive web site on the Bismarck.

The following drawing shows the U.S. Navy Computer Mk IA used during World War
II. In many respects it was analogous to the Norden bombsight, although quite a bit
bigger and heavier (3,150 lbs.). By the annotations you can immediately get a sense of 
the number of inputs/outputs, as well as calculations it had to make.

U.S. Navy Fire Control Computer Mk IA

A U.S. Navy Fire Control Computer ("Rangekeeper") Mk I
in operation, note number of technicians manning the device

The author has been unable to find any photographs of contemporary Kriegsmarine gun
fire control computers, let alone those specifically installed in the Bismarck. What I did
find, however, was a WWII German Army fire control computer designated the
Kommandohilfegerat 35.

German Army Fire Control Computer
designation Kommandohilfegerat 35

It bares a striking similarity to the Sperry (Kerrison) AA Predictor No.1 MK III used by
anti-aircraft artillery units of the British Army during the same time frame, as
can be seen in the following photographs.

British Army Sperry AA Predictor No.1 MK III with
 probable 3.7 in. Anti-Aircraft Gun in the background

A British Army Sperry AA Predictor No. 2 MK (Unk)
 obviously a much heavier configuration
The following link is to a contemporary Pathe News film describing to the general public (obviously in simplified terms) how a "Predictor" works;
http://www.britishpathe.com/video/predictions-while-you-wait .

For those of a technical bent and inclination the following contemporary (1941) Kriegsmarine report is available at http://www.kbismarck.com/archives/barmament.html, and provides detailed information. In addition the overall web site is excellent. There is another report on WWII German Naval Radar Systems found at;
http://dreadnoughtproject.org/friends/dickson/German%20Radar%201.pdf.

Scale model of the Fairey Swordfish Mk I accompanied by
a Royal Navy Type "C" flying helmet worn by the air crew
The oxygen mask only because it contained a microphone

This short video depicts the flight of the fully restored LS326 at a recent air show in
Great Britain. Truly a labor of love, and no little expense. Fortunately as a result of
voluntary private contributions, in a trust, there was not a hit on the Ministry of Defence
budget.



For those who may be interested in further details regarding the sinking of the Bismarck,
the following website is the obituary of CDR Peter "Roddy" Elias DSC, who wrote an eyewitness account of the battle as one of the pilots directly participating in the attacks on the battleship. The obituary includes several photographs and a page from his flight log book with entries from his engagement
of the Bismarck. Please see;
http://www.telegraph.co.uk/news/obituaries/11464533/Commander-Peter-Roddy-Elias-obituary.html#disqus_thread

1 comment:

Anonymous said...

It is also I have read a major factor that the Bismarck anti aircraft guns were designed for dive bombers & hence not able to fire either dead level, or below the Bismarck's deck. Steve elephantshampoo@gmail.com

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