Mosquito - the alternative strategic bomber

[Ross Sharp]

De Havilland Mosquito

Any objections ?

The de Havilland Mosquito is an aircraft I am currently heavily involved with. As Director of Engineering and Airframe Compliance, The People's Mosquito Ltd (a Registered Charity, No 1165309), we are converting the remains of an NF.36 to an FB.VI (wing ribs are being cut in New Zealand, as we speak, see The People's Mosquito).

It is quite true that the loss rate/per sortie was vastly improved compared to the Lancaster ('Bomber' Harris stated that the cost of a Lancaster and the training of its crew, could be recouped in terms of damage to the enemy in THREE sorties - provided they dropped their bomb on the target on the third sortie!) Yes, the bomb load options were as laid out earlier in this string (although I would have prefered to travel on 'Platforms 1, 2 or 3' to the Big City in the comfort of a pressurised Mk. XVI with its two-stage Merlins, than the earlier B. Mk IV).

The value of the LNSF was not just in its low loss rate, or its bomb load, or even the smaller crew numbers, but the fact that it could operate when the Main Force could not, due to weather conditions. Not only that, but the superb low-level marking techniques by our friends in No 627 Sqn (please go on our website to see them in action, in COLOUR) meant that the Lancasters of No 5 Group were turned into a precision night bomber force in the later stages of the war (627 could mark the four corners of a football field for you). However, you would still need a proportion of heavy bombers (Harris wanted an all-Lancaster Main Force by 1946) to carry large loads, including the Tallboy and Grand Slam, or the 8,000 HC or 12,000 HC blast bombs. If you could find enough good Canadian Yellow Spruce (and only one tree in 10 is good enough for the main spar) and enough balsa wood (it took a whole Ecuadorian forest, as it is), then I would have gone with a 60/40 mix 'heavies' and Mossies; please remember that the superannuated Stirlings, and the Hastings, also supported the Resistance movements throughout Europe and were excellent heavy glider tugs, etc.

We have chosen to restore RL249 as an FB.VI, but a bit of 'badge engineering' and some care additions/subtractions will allow us to change her into an FB.40, T.27, T.III, FB.XVIII, prototype Sea Mosquito and many other versions. The potential colour schemes and individual markings run into the hundreds

Please watch out for our stand at major U.K. air shows (we were at RIAT, Cosby, Sunderland, Cosford and Duxford this year) and consider supporting us, either by purchasing an item from our online store, or, even better, joining our new People's Mosquito Club bit.ly/TPMClub The Club has its own newsletter, its own website with exclusive articles on Mosquitoes, Club 'swag' (the badge is rather tasteful) and no less than five forum strings. All in all, good value at £25 a year!

There, commercial over......

Cheers

Ross Sharp
The People's Mosquito

 

[Deleted member 68059]

This may help.

(Img #3 is hard to see but is dated 2nd Sep 1943 - all images from Ministry of Aircraft Production archives)

 

[stona]

I'd like to know which department/who wrote the third document. It contains some assertions that would have been vigorously challenged by Bomber Command. At the very least it takes a very simplistic view of bomb loads (what would the 4000lb Mosquito load comprise?) and the average Lancaster load given for the first half of 1943 does not reflect the 'Usual Bomb Load' for aircraft of any UK based Groups, nor does it reflect the average Lancaster bomb load for the entire war.
Someone was obviously hoping to promote the Mosquito as a potential strategic bomber (and other roles) for use in the PTO, but without knowing who it is difficult to understand their reasons for doing so.

Nothing ever came of this, which is probably self explanatory! I wonder if someone was trying to flog the Mosquito to the Americans?

I notice one of the performance tables bears a stamp for R N Liptrot, presumably the same one who originated P.13/36 and one of the early supporters of a four engine 'Manchester'.

Cheers

Steve

 

[Deleted member 68059]

Oops.... sorry how do you delete posts...ugh

 

[Deleted member 68059]

Like many documents, the signature at the end of that letter (which is 4 pages long) is utterly illegible, but I attach the front cover
so you get the general idea, and the 2nd page of the same letter.

I cannot quantify simplistic, but I would mention that the rest of the letter indicates (at least at the time) it would appear this was indeed a very serious high level discussion. Many of the notes later on (regarding other issues) are from Sir Charles Portal, so its fairly big time people talking.

Whoever C.H. S..... is - he was also very involved with "highball" (the bouncing bomb for the Mosquito), as he has signed several others (equally illegibly)
regarding that later on. (But its definetly not C.H. Medhurst... which would have been the obvious choice)

 

[tomo pauk]

Thank you for the docs, Calum.
BTW - I'm still very much interested in that book...

 

[stona]

There was from time to time serious discussion about extending the role of The Mosquito force. This became most strident immediately after the Battle of Berlin, when even Harris to doubt whether the offensive could be maintained by 'the existing methods and types of heavy bombers.'
It was much too late (and would have been even two years earlier) to change the front line composition of Bomber Command, but it did raise questions about the all heavy bomber policy of the RAF adopted years earlier. Of the 2,034 Mosquito bombing sorties (excluding Serrate and reconnaissance sorties) to Berlin during the battle, just 10 (0.4%) failed to return, though 89 (4.3%) were damaged. Here, once again, we have the benefit of hindsight not available to those making the policy decisions in the immediate pre-war period.

Webster and Frankland hit the nail on the head in the official history when they wrote.

"Though the value of Mosquito bombers was out of all proportion to their numbers, it was, nevertheless, strictly limited by the fact that they were so few. It was not until March 1944 that the Mosquito bomber components showed signs of expansion, and in that month the average number of these aircraft available with crews for operations was no more than fifty eight. Meanwhile, the Wellington component was disappearing so that in the Battle of Berlin the ideal dating back to 1936, of an 'all heavy' bomber force found its ultimate expression, if not its vindication."

There was never any suggestion that the Mosquito would operate at low level or by day, at least not as routine, just that equipped with the latest versions of the navigational aids it would operate as a night bomber. In this role it would, as it did historically, suffer far lower losses than the heavy bombers. It could never have delivered the devastation of the successful area raids, or the more precise raids undertaken from time to time. The often repeated suggestion that it could carry half the load of a Lancaster (on similar missions) is nonsense.

Cheers

Steve

 

[Timppa]

The often repeated suggestion that it could carry half the load of a Lancaster (on similar missions) is nonsense.

Mosquito had the proven capability to carry 4,000 lbs to Berlin from the start (Mark B.IV mod).
The figures of the average Lancaster bomb load to this distance I have seen quoted is about 7,500 lbs.

 

[stona]

The first raid with Mosquitoes carrying a 4000lb cookie took place on 23rd February 1944 carried out by three modified Mk.IVs with 4000 pounders, backed up by another aircraft with 4 x 500lb bombs, all following six 105 Squadron Mosquitoes which marked the target (Dusseldorf). Throughout the last six months of 1943 Mosquitoes raided Berlin with a maximum load of 6 x 500lb bombs (two carried externally), a respectable 3,000lbs. This was above the average carried by the type throughout the war, but early versions could not manage anything like this load.

The possibility of carrying a 4000lb bomb, eventually General Purpose, Medium Capacity and High Capacity versions would all be shoe horned in, was first raised in April 1943. It was not a straight forward adaptation and it wasn't until 9th October 1943 that a decision was made to modify all Mk. IVs and Mk. IXs in service and that all Mk. IXs and Mk. XVIs in production would be built with the capacity to carry the larger bombs. This NEVER happened.
In January 1944 Boscombe Down provisionally passed the Mk. IV for service, but only with the large elevator horn balance, rear camera removed and 60lb ballast in the nose. Stability problems were never solved on the Mk. IV and this is why very few Mk. IVs or Mk. IXs were modified.
It was only the B. Mk. XVI which, having been designed from the outset to carry a 4000lb bomb, did so successfully and in numbers. Operations with this aircraft didn't begin until March 1944.

It wasn't until November 12th 1941 that the possibility of carrying the often quoted 4 x 500lb bombs was even investigated. This was to be for a proposed B. Mk. VB version. This load wouldn't fit in the bomb bay of the Mosquito which had been designed for a 1,000lb load (2 x 500lb or 4 x 250lb bombs). It was only after experiments with telescopic fins on the bombs that the short finned versions were adopted. The extra load led to instability problems and a new tailplane with a 10 degree dihedral was designed to mitigate these, longer nacelles were also developed.

Lancaster Marks varied, as did the distance of their operational airfields from Berlin, but most could a 12,000lb load to Berlin. The Mk.I and Mk.III could both carry 14,000lbs for 1,660 miles. Not all did for reasons already mentioned. The average bomb load carried by Lancasters and Mosquitoes throughout the war I have already given in this thread, the Lancaster's is nearly 5 times that of the Mosquito, at least in part because the Mosquito did not have the ability to carry the 4,000lb so often referred to until the last year of the war.

Average figures must be carefully examined. For example, the average bomb load for ALL RAF bombers for 1943 was 6,903 lbs and for 1944 8,250 lbs. Sometimes I wonder if these figures get attached to particular aircraft in some way. Incidentally, both these figures are more than twice those for the bombers of the USAAF the same periods (3,220 lbs and 3,980 lbs, whatever the theoretical maximum loads of the B-17, B-24, etc. might have been).

Cheers

Steve

 

[tomo pauk]

Whether we agree or don't agree with the original premise, this turned out to be an excellent thread.

 

[stona]

[QUOTE="Snowygrouch, post: 1287619, Many of the notes later on (regarding other issues) are from Sir Charles Portal, so its fairly big time people talking...

Whoever C.H. S..... is - he was also very involved with "highball" (the bouncing bomb for the Mosquito), as he has signed several others (equally illegibly)
[/QUOTE]

I'm sure you know your Portals, but there was an Admiral Portal (Charles Portal's brother) involved with 'Highball' in the Pacific. It was this Admiral Sir Reginald Portal who informed No. 618 Squadron, on 29th June 1945, that it was about to be disbanded. The weapons were destroyed by an order of 10th July, rattling windows and causing considerable alarm to the usually unflappable citizens of Sydney
Cheers
Steve

 

[GrauGeist]

I'm not sure if this has been addressed before and if it has, my apologies, but what was the performance penalty on the Mosquito when at max. load?

In otherwords, was it under risk of being caught by standard Luftwaffe interceptors (Bf109, Fw190, etc.) until it dropped it's load?

 

[Hop]

Yes, a cookie was a bomb to blow off roof tiles it had most effect when it exploded above ground, such a bomb would have almost no effect on the important parts of a refinery, if you see the remains of German cities they were burned to the ground but the brick structure ws standing, a steel structure would be unaffected.

To wreck a refinery you need a huge blast to destroy or undermine the pressure vessels which take months to construct or repair, damaging pipework and instruments can be rectified in days.

The cookie was very effective against structure and machinery.

From the USSBS, describing attacks on refineries:

Blast walls and reinforced concrete "dog houses" were useless against 4,000-lb. bombs, but prevented serious damage from near misses by 1,000-lb. bombs and were effective against even direct hits of 500-lb. and smaller bombs. But the utility systems were vulnerable, and the oil attacks were therefore successful.

and

Vital process installations were so effectively protected by blast walls and reinforced concrete "dog houses" that essential, hard-to-replace equipment was seldom destroyed by the munitions generally employed. In a few instances, of which the Bottrop-Welheim (Ruhroel) hydrogenation plant is the most striking example, this destruction was accomplished. In two raids, 27 September and 31 October 1944, the RAF hit the high-pressure compressor house with three 4,000-lb. and eight 1,000-lb. bombs. The seven heavy compressors and boosters, through which was funneled every cubic foot of the hydrogen required for the process, were completely destroyed. The plant could not operate until new compressors were installed. This meant a twelve-month shutdown if new compressors had to be built and a delay of three months of replacements had to be "lifted" from another plant. The four subsequent attacks were unnecessary. The results may be compared with those at Leuna, which, after being hit by 1,643 tons of bombs in 22 attacks, could have reached 70 percent of normal production capacity within a few months without the importation of any new heavy equipment.

 

[Shortround6]

The Mosquito as a strategic bomber replacement for the 4 engine bombers requires several time line shifts.
It also requires a change in bombing tactics/techniques that may or may not have been as effective as what was used.

The Early Mosquito was limited to the 1000lb bomb load. The documents provided by Snowygrouch show this even in reference to planned/proposed versions using Merlin 60 engines as of July 25th 1941. By May of 1942 the bomb load had gone to 2000lb inside the bay using the shortened 500lbs and a further 500-1000lbs under wing. Or even six 250lb bombs. Not sure if this was due to supply or doctrine or a combination of both. Documents show estimated performance with a Melrin 61 type (power level) engine as the Mosquito could not use Merlin 61s due to the radiator placement (difference was minor).
An early Mosquito (service use in 1940 or early 1941) would not have had Merlin XX engines (Hooker supercharger) and would either have had shorter range or been limited in bomb load even if short fin bombs were available.
And it doesn't matter what kind of airplane is dropping the bombs, the RAF in 1940-41 couldn't find the right city on too many of it's missions at night so there would have no change in effectiviness, in fact one might argue that it would have been less on the occasions the right city was found as finding even a large factory was still very difficult and dropping less bombs would not have helped. (and in 1940-41 the Bombers in use were pretty much Wellingtons and Whitleys which were much closer in price to the Mosquito).

An awful lot is made of the 4000lb cookie and average bomb weights. The Mosquito's bomb bay was much more limited by volume than by weight (even with the bulged doors) and a lot of times the average weight of the 4 engine bomber loads is skewed by their large use of incendiaries. The Incendiaries having a larger volume to weight ratio. This varies a bit by type/s of incendiaries but what was the Mosquito's ability to carry incendiaries or small bombs?

Could a Mosquito fit four of those incendiary bundles in it's bomb bay? The Lancaster could hold 15 without the big bomb.
the Halifax wasn't far behind.

Up to six small bomb carriers in the wing bays in addition to the bomb bay.

Pictures from an Oct 1944 raid.

By the time the Mosquito had demonstrated it's capability (say mid 1943) for even a 3000lb bomb load. it would have taken well over a year to change production around. Maybe two years.

Lets not forget that the Specification for the Manchester called for a CRUISING speed of 275mph. What they got was a plane that had a TOP SPEED of 265mph and cruising speed much lower. Unfortunately high speed and short field performance where conflicting requirements, even if you ditched the gun turrets a 1937-39 bomber trying to use existing RAF airfields has a real problem with airfoils, wing size, and even the size/weight of it's landing gear (large engine nacelle needed) all affecting the drag over an optimized high speed design, making an "early" Mosquito even more unlikely.

 

[wuzak]

The Early Mosquito was limited to the 1000lb bomb load. The documents provided by Snowygrouch show this even in reference to planned/proposed versions using Merlin 60 engines as of July 25th 1941. By May of 1942 the bomb load had gone to 2000lb inside the bay using the shortened 500lbs and a further 500-1000lbs under wing.

The under wing stores came later with the universal wing for the FB VI.

I don't believe any Mosquito bomber went into operation service with the 1,000lb restriction. By the time they went into service they had the 2,000lb restriction.

Testing later in 1942 even included a load of one 1,000lb GP and two 500lb MC.

An awful lot is made of the 4000lb cookie and average bomb weights. The Mosquito's bomb bay was much more limited by volume than by weight (even with the bulged doors) and a lot of times the average weight of the 4 engine bomber loads is skewed by their large use of incendiaries. The Incendiaries having a larger volume to weight ratio. This varies a bit by type/s of incendiaries but what was the Mosquito's ability to carry incendiaries or small bombs?
Could a Mosquito fit four of those incendiary bundles in it's bomb bay? The Lancaster could hold 15 without the big bomb.
the Halifax wasn't far behind.

The Mosquito B.IV/B.XX could carry four 160lb or 250lb Small Bomb Containers internally, but only two of the larger 500lb SBCs - these were on the forward stations (last of the internal stations to release). I would have to check, but I believe two 500lb MC bombs could be carried on the rear racks at the same time as carrying the 500lb SBC. They could also be carried on the wing racks.

Canadian built Mosquito MK XX VB328 was checked for its bombing installation and found to be be the same as the IX.

Tests conducted were with standard bombs - 500lb MC/GP and 250lb GP/SAP, 500lb SAP as well as the 250lb SBC. It was noted that the 500lb SBC could only be fiteed to the forward carriers, as when fitted to the rear they fouled the hydraulic door mechanism. It was noted, from prior experience, that 4 of the 160lb SBC could be carried, though they didn't have any to test.

Incendiaries didn't just come in small bombs. They also had sizes similar to the GP bombs. I believe they also had a 4,000lb IB. I will have to check when I get home.

 

[stona]

Bomber Command dropped almost exclusively 4lb and 30lb incendiaries.
There was some debate about the relative effectiveness of the two, but the 4lb incendiary in its various forms was used almost exclusively from 1943, on area raids, until the end of the war.
The 250lb incendiary bomb was converted into a TI bomb. The 500lb (phosphorus) incendiary bomb was used by Mosquitoes according to some sources.

During the war Bomber Command dropped 80,000,000 4lb incendiaries and just 3,000,000 30lb incendiaries. 7,000 250lb incendiaries were dropped and IF Mosquitoes did indeed drop the 500lb version I can find no record of it.

The load in the Lancaster bomb bay above was code named 'Usual'. It is a typical blast and incendiary load designed for an area raid. Other aircraft would drop some HE loads to interfere with flak, fire fighting efforts and hopefully to fracture gas and water mains.

The Mosquito couldn't carry enough bombs to carry out some of the missions assigned to the heavy bombers. I have already mentioned the problem of incapacitating and keeping out of action selective targets, like those of the oil and transport plans. I also mentioned the sheer weight of bombs dropped in support of ground troops following the invasion.

Obviously the Mosquito was not suitable to carry out area type raids. The weight of bombs required was beyond that of even a force of hundreds of the type. There is no saying that precise targets could be hit, at night, and from altitude by a Mosquito anymore than a Lancaster.
Dresden is an outstanding example of the concentration of bombing in space and time to achieve a really successful area raid.

The first wave, comprising 5 Group (244 aircraft) dropped 881.1 tons of bombs on the centre of the city in 15 minutes (between 22.13 and 22.28). 57% by weight were HE and 43% incendiary. This would have been enough, but then a second wave arrived.

8 Group (60 aircraft including master bomber, markers and illuminators) bombed from 01.21 to 01.45 and dropped another 135.7 tons of bombs, including 10 tons of TIs and 550 Illuminators (Christmas Trees)

1 Group (248 aircraft) bombed from 01.23 to 01.52 and dropped 387.3 tons of high explosive and 558.3 tons of incendiaries. (219,933 4lb stick incendiaries, 28,467 4lb incendiaries with explosive charge, 70,266 4lb incendiaries 'bundled' in clusters, No. 14 cluster was 158 x 4lb incendiaries, a No. 15 cluster was 104 of the same.)

3 Group (151 aircraft) bombed from 01.25 to 01.55 and dropped 234.8 tons of high explosive and 233.0 tons of incendiaries.

6 Group (65 aircraft) bombed from 01.27 to 01.45 and dropped 216.8 tons of high explosive.

Total number of 4000lb cookies dropped, maximum load of a Mosquito, was 356. 2,647 tons of ordnance fell on the city in the two waves. The idea was to devastate the city in support of the Soviet offensive. It succeeded in that. What could a force of even several hundred Mosquitoes have achieved? They might have attempted to attack the railway station and other rail and transport infrastructure, but who knows if they would have hit it.

It is, as I intimated elsewhere, not fair to compare the Lancaster and Mosquito as strategic bombers. The Mosquito was not designed to be one, nor could it fulfill that role, whereas the Lancaster was and did. The Mosquito had many other strengths, and performed outstandingly in various other roles.

Cheers

Steve

 

[stona]

I don't believe any Mosquito bomber went into operation service with the 1,000lb restriction. By the time they went into service they had the 2,000lb restriction.

That is correct. The first bomber version (B. Mk. IV) had a 2,000lb bomb load with 539 gallons of fuel.
The largely unsuccessful 'cookie' conversion could carry the 4,000lb bomb, but reduced fuel capacity to 497 gallons (and operational radius to 535 miles.)
Cheers
Steve

 

[Shortround6]

That is correct. The first bomber version (B. Mk. IV) had a 2,000lb bomb load with 539 gallons of fuel.
The largely unsuccessful 'cookie' conversion could carry the 4,000lb bomb, but reduced fuel capacity to 497 gallons (and operational radius to 535 miles.)
Cheers
Steve

Thank you.
I was going by the documents in Snowygrouch's posts, not as what was in service but but what was planned or intended at earlier than service dates as an check on when or if a change in direction could have been made. The loads listed for the MK V bomber and MK VI fighter bomber

going by the date on the bottom 13-5-42 would seem to indicate that at around that time the wing stations were planned at 250lbs each and the internal bomb stations were planned for 250lb bombs. Work being done on the 500lb bombs with telescoping fins? Since no Mosquito ever flew using either Merlin XX (Merlin 21,23,and 25 differed in detail from the XX but not in performance) or Merlin 61 engines this would be estimated performance using those engines as a reference point.
In the Spring of 1942 a 2500lb bomb load would hardly be looked at as a substitute for a strategic bomber in planning for future production (1-2 years ahead)

 

[stona]

The cookie was very effective against structure and machinery.

Does the report refer to 'cookies' that is High Capacity bombs? Not all 4,000lb bombs were 'cookies'.

The 4,000lb High Capacity bomb was specified in September 1940 and sometimes referred to as a 'mine-bomb'. I have seen it referred to as a 'mine' in Bomber Command Squadron ORBs even in early 1945.

The original specification included requirements that,
i) It could be carried by a Wellington
ii) It was for the attack of ships in shallow waters, harbours, canals and land targets such as oil plants [which were top of targeting lists at this time]
iv) To be released from 1,500 feet without breaking up
v) Instantaneous and delay fusing
vi) Capability to be used as a magnetic mine, with a magnetic fusing system.

I don't know that it was used for these objectives, I can't find any evidence for it being used as a magnetic mine. It was soon discovered that the blast complemented other ordnance dropped as Bomber Command developed its tactics for area raids, and in this sense pbehn is correct. For incendiaries to be most effective it is important that they lodge inside buildings, roof spaces, etc. Blowing in windows and blowing off roof tiles with high capacity bombs greatly increased the chances for this happening.
It was a bonus that the blast from a 4,000lb High Capacity bomb was calculated to destroy 3.2 acres per ton dropped, much better than the 0.56 acres per ton of the 1,000lb GP bomb. This acreage destroyed was for typical city areas, housing, shops and small businesses.

Cheers

Steve

 

[stona]

The Mark V bomber (B. Mk. V) was a projected project and the wing stations were indeed planned for two x 250 lb bombs or 2 x 50 gallon fuel tanks. Various versions were projected (the redoubtable W4057 served as a prototype for these among many others) but none were built. As far as I know the planned engine was the Merlin 21.

The F.B.VI was built and did could carry 4 x 250lb bombs, two externally, as well as a bewildering array of other ordnance in various configurations.

Cheers

Steve