Blenheim as a torpedo bomber?

fastmongrel said:

I think there is a great What If to be written about the RFC and RNAS staying seperate and equal services.

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But then then one would be part of the RN and one part of the Army and there would be no independent air Service at all !

It was only by amalgamating both that the RAF was created, the FAA being part of the RAF until it was removed from the RAF and handed to the Admiralty shortly before the war. This when their Lordships first tried to get control of Coastal Command and its shore based assets.
There was never an independent naval air service, it was always under either the Air Ministry or Admiralty. I don't see how it could ever have existed independently.
Cheers
Steve

stona said:

But then then one would be part of the RN and one part of the Army and there would be no independent air Service at all !


Cheers
Steve

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Thats exactly what I find so intruiging, how would things have developed with an RFC and an RNAS. Maybe things would have developed on similar lines to the US air services or the RFC becomes like the Luftwaffe a service designed to support the Army and protect the Home country while the RNAS takes over responsibility for Heavy bombers and Empire defence. The possibilities are endless and I wish I had the time, the knowledge and the writing skill to explore some what ifs.

You could write a book on it!
Who would control a strategic bombing force? The Army or the Navy? The first such force came into existence in the RAF, but IIRC the RNAS had a go at it (in a 1917/18 context) first.
Cheers
Steve

fastmongrel said:

I think there is a great What If to be written about the RFC and RNAS staying seperate and equal services.

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Yep, although its arguable that with thinking in the 20s and 30s the way it was, would the thought processes of the Admiralty staff been made with any more foresight that they were.

Back to a Blenheim with carrying a torpedo for a moment, I suspect the actual path taken of designing a whole new aeroplane to do so was the right one; The Blenheim would have required too much structural modification to allow it to happen. Firstly, the Beaufort wasn't Just a modified Blenheim; they had virtually no structure in common; the control yoke was the same, but little else - the same spectacle control yoke was also used in the Beaufighter. Also, just lengthening the tail wheel strut doesn't make a torpedo bomber. Where on the Blenheim's structure are you going to mount the attachment brackets? Forward or aft of the bomb bay doors? Either way the aircraft's C of G is going to be seriously compromised without altering the bomb bay design. This is where the Hampden was ideal; little structural change was required to carry a torpedo internally (I'll get back to that).

Also, while the Blenheim might have been capable of carrying the equivalent weight of a torpedo, it wasn't carrying it as a single mass. How would that affect the aerodynamics? Would it actually be able to fly with a torpedo and what would its handling be like on release? it'd probably porpoise like, well, a porpoise. Those puny little Mercurys weren't going to be able to do much. Bigger engines were required.

As for the Hampden, it proved useful but slow; modifying it required little change to its existing structure; the lower rear gun cupola was made smaller, which gave the impression of an alteration to the depth of the bomb bay doors, but these remained the same as on bomber variants. Issues arose with the decision to carry torpedoes with detachable fins; the torpedo could no longer be carried internally and therefore the bomb bay doors remained open in flight. The fins extended aft of the torpedo's prop and in the Hampden sat over the revised gun cupola. There were handling difficulties with the Hampden as a torpedo bomber however, which did cause the loss of examples carrying out torpedo training; the Canadians lost at least one during training in Patricia Bay. I can't elaborate further on its service as a TB, as I'm away from home.

A better aeroplane was required. Thank Bristol for the Beaufighter.

the RNAS had a go at it (in a 1917/18 context) first.

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They more than had a go at it; the first strategic air strikes of the Great War were made by RNAS aircraft, as early as 1914. Also, the big Handley page bomber, the HP O/100 was built to a requirement stipulated by Cdre Murray Sueter, Director of the Air Department of the Admiralty a year later.

The Hampden required a little more modification to fit the torpedo, at least one of the frames was altered and the reinforced hard point to mount the torpedo installed, but essentially I agree.
Cheers
Steve

yep, Steve, I'm aware of that, but the Blenheim would have required a lot more than reinforcing hardpoints in the bomb bay and altering a frame or two. I remember reading that the Hampden's bomb bay floor level was altered as a result of the doors no longer sitting flush with the rear cupola; but I cannot believe that extensive modification was carried out.

Yeah, that old chestnut still does the rounds! The bomb bay was not itself modified, only the frame at the rear of the bomb bay was reduced in height and had either a 12" cut out or a concave bottom, depending who you believe, to accommodate the back of the torpedo. The rear cupola was reduced in height by 12" to clear the 'Monoplane Air Tail' (MAT). It didn't move fore or aft. The glazing seems to have changed to accommodate this too. A heavy duty carrier to mount the torpedo was fitted to the roof of the bomb bay.
You will know, but for those that don't, the main body of the torpedo was carried , partially exposed, within the length of the bomb bay. The breakaway MAT sat behind the bomb bay area and cleared the reduced gondola by 3" (on a good day).
All in all, as you first said, it was a relatively simple conversion. Had the bomb bay itself had to be substantially modified, or even the gunners cupola moved, it would not have been and I wonder if it would ever have been done.
Cheers
Steve

Yep, thought it was a stretch, Steve. Would like to see the RAF Museum example when its done.

The RAF Museum's Beaufort and torpedo with fins.

nuuumannn said:

Yep, thought it was a stretch, Steve. Would like to see the RAF Museum example when its done.

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Still being 'resurrected' at Cosford but I will certainly be in the queue to see it too

Cheers

Steve

It might not have been a that great trick to hang a torpedo underneath a Blenheim, as in bolt the bomb bay doors shut after cutting appropriate holes in them to clear struts/mounts for the torpedo. This does affect both range and speed compared to putting the torpedo inside the airplane and with the limited power British engines of the late 30s needing all the help they could get to get an aircraft up to a decent speed. However most any monoplane would have had a huge advantage on speed/range over the Vildebeest.

There is no real technical reason that some sort of half-a**ed torpedo bomber could not have made using the Blenheim as a base.
The MK IV was supposed to have an all up weight of 14,400lbs. They were using MK Vs at up to 17,000lbs all up. I don't what was modified to allow the MK V to operate at that weight but I would guess the modifications were minor.

Such a torpedo bomber would neither the speed or range of the Beaufort (or perhaps even the Botha

A much better Blenheim than the MK IV could have been built using existing parts ( in the sense that nothing needed to be "invented" rather than finding production capacity) even in 1939.

The real what if comes in the already mentioned political struggles (read inter-service and intra-service rivalry/s).

Prying any "remotely usable" bomber away from bomber command in 1938-39-40-41 was difficult if not impossible depending on the year.
"Remotely usable" being anything that could fly from Britain to the German border, drop several 500lb bombs and return to Britain if not attacked by the Germans. Being a bit facetious here to get the point across.

Had extra production been available to build 400-600 more twin engine aircraft then Bomber Command would have been foaming at the mouth like a rabid dog trying to get them too.

In hindsight we know that bomber command accomplished almost exactly squat (nothing) in 1939-40 and parts of 1941 so any diversion of assets stood a good chance of improving something---anything over what was done.
What is hard to understand is the refusal to consider these diversions (splitting) of assets (aircraft/crews/ground crews) at the time given both the experiences of WW I and the lack of proof of results at the time. How long did it take before photo recon missions were started to assess bomb damage (or lack of it) by bomber command?
Or the fact that next to nobody was willing to point out that the emperor had no clothes?
The British had ONE night bomber squadron in 1937-38 (please correct this) flying bi-planes and this squadron rarely flew (let alone practice bomb) at night in order to reduce accidents.
It is one thing to plane your doctrine/strategy on an unproven concept. It is another thing to base it on a doctrine/strategy that hasn't even been really trained for, practiced or trialed in exercises.

One of the few things bomber command did get right was the rapid shift from daylight bombing to night bombing after Wellingtons and Hampdens were shown to be incapable of penetrating German "air space" without unacceptable losses in the fall of 1939.

The Mk XII Torpedo weighed 1,548 lbs. The carrier, accessories etc later fitted to the Beaufort was about 150lbs so this Blenheim is going to need to lift about 1,700lbs. I believe this is more than the maximum bomb load allowed for a Blenheim IV.
The Mk XII was also 16'3" long without a MAT. Not sure where that goes on a Blenheim either. There's no point in ditching a load of fuel to allow the extra lift, even if it is possible. Any land based torpedo bomber is going to need all the range it can get.
Coastal Command's request for three Blenheim IVs for trials, which was anyway declined, was for trials as General Reconnaissance aircraft, not a torpedo bomber.



The post above makes some good points. Bomber Command embarked on a steep learning curve during the war, but unlike Coastal Command it didn't really start that in 1939.
All the 'Western Air Plans' which the RAF was supposed to implement on the outbreak of war were based on erroneous assumptions. Plans 1,4 and 5 included detailed planning of Bomber Command's role. None of them included any means of helping Poland whose nearest point was 700 miles from Bomber Command's UK air fields.

Cheers

Steve

I am not sure the weight of the torpedo is all that big a problem.
The MK I Blenheim went from 8100lbs tare and 12,500lbs all-up to the MK IV, 9790lbs tare and 13,500 (or 14,400lbs depending on source) to the MK V (type 160) at 11,000lbs tare and 17,000lbs all up.
Trading fuel in the outer wing tanks (94 imp gallons each) for the weight of torpedo might very well even things out too.
Plenty of carrier based torpedo bombers traded fuel for torpedo weight when switching from recon missions to torpedo strike missions.
Just filling the outer tanks 1/2 full saves 700lbs.
The Blenheim suffered from being under-powered for most of it's career. When first introduced it was certainly as good (or better) than some contemporaries (foreign) but as time went on the contemporaries got better engines and props. The Blenheim got 100 octane fuel but was stuck with pretty much the same power plant to the end of it's days. Put that together with being shuffled off to the tropics (North Africa and the Far East) where the hot temperatures sapped engine power, prop bite and wing lift (and tropical filters did what ?) and it is little wonder that the bomb load of the Blenheim was never officially increased. Also please note that a fair proportion of the weight increases in the later models went to increase protection (both armor and protected tanks) and increase defensive guns/heavier gun mounts/turrets and other operational equipment.

We might also recall that fuselage/nose was modified when going to Mk IV, and then again for the Mk V. These modifications added the weight.
The Mercury engines wer not the latest thing, still the Blenheim have had better power to weight ratio than Beaufort with Tauruses, along with more favorable wing loading.

The Finns managed to lift 800kg according to some sources, but in what condition they were flying (fuel, armament etc) I don't know.

The British loading plans I've seen show either 4 x 250lb or 2 x 500lb bombs. The 1,000lbs maybe what would fit internally, not a maximum load.

One thing is certain, a torpedo could not have been carried internally and the effect on the Blenheim's less than stellar performance of hanging one externally can only be guessed at.

Cheers

Steve

For the best description of the Blenheim bomb load arrangements (and guns) I have seen so far (Better ones may be available) see:

Blenheim armament

I don't believe anyone here has suggested putting the torpedo inside the plane and while inside torpedoes were quite the rage in the late 30s carrying torpedoes on the outside seems to have worked for the He 111, the Italian SP-79, the Japanese GM3 and some other aircraft.

Ju 88 also carried torpedoes externally, so did in Soviet service the A-20 and Il-4.

The speed figures I have, thanks to Neil Stirling:
Mk.I - 285 mph @ 15000 ft
Mk.IV (bomber, 3 forward firing guns, 2 guns in upper turret) - 266 @ 11800
Mk.IV (fighter, tray with 4 .303s, 2 guns in turret) - 260 @ 12000 ft
Mk.V ('Bisley') - 263 @ 13000 ft; 244 @ 6000

Beaufort I (Taurus engine) - 247 @ 5000, 236 @ 5000
Hampden (1 torpedo, mean weight) - 220-233 mph

We can expect at least 240 mph for a Blenheim + torpedo?

Hello Stona
thanks for the Blenheim armament link!

On FiAF Blenheims, see my messages #5, #10 and #12. From the info in the last one can calculate that most of the six Blenheims of the Bomber Sqn 48 participating that mission carried 860 kg (1896 lb) bombs. Only differences to the RAF Blenheims were that FiAF Blenheims had 2 wing mgs and IIRC always only one turret mg and again IIRC our short noses had extra tankage when compared to the RAF Mk. Is. And of course different bomb carriers.

Juha

There is no real technical reason that some sort of half-a**ed torpedo bomber could not have made using the Blenheim as a base.

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Sure, then again, anything could be done to make the Blenheim better or more varied in its roles, question is, why bother? In 1939 the Beaufort flew for the first time and was clearly the RAF's preference - it was bigger, more powerful and could carry a heavier load than the Blenheim - it was purpose built for the role. Any time after 1939, when the storm clouds gathered, the Blenheim was found wanting in performance and load lifting ability. Modifying it would be a waste of time and effort when the best option would be to concentrate on the development of the Beaufort and Beaufighter. The Beaufighter, which, admittedly was not available in large numbers in 1939 - '40 was altogether more suited to the role as it became the RAF's premier torpedo bomber in Coastal Command strike squadrons by the end of the war. The Mosquito made a poor torpedo bomber.

It would have been nice to concentrate on better types, but in 1941, when the first real anti-shipping campaign got underway, Coastal Command was operating 13 Squadrons of which 7 were equipped with Blenheims (2 on loan from Bomber Command), 4 with Hudsons and only 2 with Beauforts. These came under No 18 Group operating from the east coast.
In March '41 when German successes against British shipping in the North West Approaches caused a redistribution of Coastal Command's anti-shipping assets and 4 squadrons were transferred to the North West, the gap created was filled by even more Blenheims from Bomber Command's 2 Group.
This led to yet another spat between the two Commands.In May 1941 it became apparent that the two Commands were not coordinating their operations so that some areas had overlapping patrols whilst others had none. The two AOCs-in-C were asked to establish a division of responsibility to avoid this but the ensuing disagreement became a major row over the proper function of the two Commands.
Peirse claimed on Bomber Command's behalf that ALL bombing, whether against ships or on land should be under Bomber Command control. He wrote.

"Experience has shown abundantly that two separate forces cannot run an offensive against shipping in the same area. The anti-shipping technique is complicated and must be directed by one hand. It is moreover a bombing technique."

His crews might have substituted 'suicidal' for 'successful' for the low level technique, but no one asked them.
In return Joubert argued that the fact No. 2 Group's Blenheims had adapted themselves so well to attacking moving targets at sea using an aircraft already deemed redundant for the purposes of the main bomber offensive was a good reason to hand them over to Coastal Command. With an eye for the influential bomber advocates on the Air Staff, he concluded.

"It is agreed that the attack on shipping can be one of the roles of Bomber Command but it should be a very minor one and subject to the diversion of aircraft to the main role, which is the attack on military and industrial objectives within Germany."

The referee for this match was once again the Chief of Air Staff, Portal. He refused to get embroiled in the arguments and simply divided responsibilities on geographical grounds. Bomber Command got the area from Cherbourg to the Dutch Frisian island of Texel, Coastal Command the rest.

Why is this important? The answer comes in one word, range. I have read that the Finnish Blenheims only carried the heavy loads for 300Kms, a 600Km round trip plus a reserve. If you dig out your old Atlases and look at where Coastal Command's Blenheims (the bulk of its force) were to operate in 1941 you will see that this might be a problem.
For example, to fly from a North Eastern base across the North Sea to the Norwegian coast is at least 400 miles. Once there the aircraft had to fly a patrol line before returning. From a South Western base to the Bay of Biscay is a similar distance.
If a fully equipped Blenheim can lift 700-800kg with a sufficient fuel load then it might be viable for such operations, otherwise it is, as it historically was, a non starter as a torpedo bomber.

Cheers

Steve

stona said:

...1933. A series of trials for different techniques. High altitude 'precision' bombing by three aircraft from 9,000ft, high altitude 'pattern bombing' up to 16,000ft by a whole squadron, dive bombing with release at 1,500ft and bombing ahead of the ship with a buoyant ('B') bomb were all tried. Dive bombing was most accurate with a 38% hit rate.

1934. Similar trials at which despite the repeated success of dive bombing the RAF chose 'pattern bombing' by a whole squadron as the standard method for attacking shipping....

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Not very surprising, also IJNAF made the same conclusion for their land based medium bombers and used it in 1941-42.