Mosquito - the alternative strategic bomber

Occasionally the very bright people pulled some real clangers. Like the Blackburn Botha.
It doesn't take a retrospectroscope to figure out that increasing the empty weight of a MK IV Blenheim by about 20% and the max loaded weight by about 25% while increasing the power by only 15% or less was going to lead to an under powered aircraft. Compared to the MK Blenheim the Botha increased over 40% in loaded weight.
Sleeve valves are only going to do so much on an engine with the same bore and stroke.
Poor vision for recon should have been caught at the mock up stage, that is why they build mock-ups, to catch 3 dimensional problems that might not show up on flat plans, like vision from cockpit/s or observation windows.

evaluating operational results is a lot harder as we often do NOT have all the facts or we are trying to compare things that are not actually alike (low altitude bombing vs high altitude)

parsifal said:

It was designed as a recon machine upon which a number of secondary roles were added, and then added and then added again.

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It was designed as bomber, with the roles of fighter and reconnaissance being "added" or being required at almost the same time. Out of the first order for 50 aircraft the exact mix of how many went to each role was shifted about several times before the first production plane ever flew.

There were only about 1700 Mosquito bombers built and the majority of those were from around the Spring/summer of 1943 on (several hundred completed after VE day.) Most, if not all of the ones from the Spring/summer of 1943 having two stage Merlin's which did wonders for the performance and survivability, something like 1000 of the bomber mosquitoes had the two stage engines. However one wonders how well a Lancaster with two stage engines and a pressure cabin for the pilot/Forward crew would have performed??

Dropping 4000lb cookies from over 30,000ft is hardly a substitute for what the Lancasters and Halifaxes were doing.
Not disparaging the Mosquito crews, ANY pilot or crewman flying wartime missions deserves full respect no matter what the location/mission.

Now with enough "forward vision" the stick to the old ways AIr Marshals might have been able to increase production of two stage Merlins enough to make much larger numbers available from mid 1943 on to power a much increased Mosquito bomber fleet (or Lancasters with two stage engines to go along with different tactics.)

There were only 3 squadrons of Mosquito bombers operational (?) in 1942, 105 Squadron from Nov 1941 although first combat was May of 1942. August saw 109 Squadron equip with Mosquitoes but 109 squadron was primarly tasked with radar development and electronic and navigation equipment development and tactical implementation. No 139 Squadron was equipped with Mosquito Bombers in Oct 1942. It was these two squadrons that performed the bulk of Mosquito bomber (as opposed to Mosquito fighter bomber) day missions.
Despite being highly publicized were these raids enough to change RAF bombing policy on?
By July 1943 Both squadrons were being re-equipped with later version Mosquitoes with two stage superchargers and had been transferred to No 8 pathfinder group.

The two stage engines in the later Mosquitoes could make about the same power at 21,000ft as the engines in a Lancaster could make at 11,000ft. and had about 220 hp (15%) more at low altitudes.

parsifal said:

Whatever arguments about the mosquito, it has the runs on the board to show that conceptually at least it could operate by day or night, at high, medium or low altitudes. It might as a type have needed some modification in the design to increase range, or bombload, or engine power. we should not be arguing that the mosquito was designed for the purpose we are now considering. it wasn't. It was designed as a recon machine upon which a number of secondary roles were added, and then added and then added again.

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The Mosquito was designed as a high speed, unarmed light bomber. The PR role was a secondary one, though the first RAF orders were for this role.

I have no doubt that the Mosquito could have provided a more useful contribution to the strategic bombing effort than it already did. The limiting factor was, as mentioned previously, the numbers of available bomber variants. And that was because of the other roles it was required to fill.

I never felt that the Mosquito could replace the Lancaster. My view was that it could have acted as a replacement or supplement to the B-17 during the daylight campaign.

One raid that I thought may be possible for the Mosquito would be the first Schweinfurt raid. The range is just about within the Mosquito's capability at low altitude.

The 200+ B-17s hit the actual target buildings with 80 1000lb bombs.

The Mosquito couldn't carry 2 x 1000lb MC at that point, and 2 x 1000lb GP bombs would have half the explosive charge of the US bombs. So they would need to use 2 x 500lb MC for each US 1000lb GP bomb to have the equivalent explosive charge. The Mosquito could carry 4 of the 500lb MC.

So, to get the same explosive charge on the factory buildings you would need 160 hits with the 500lb MC - which means 40 Mosquitoes at 100% accuracy.

But let's say that they have 50% accuracy. That would require 80 Mosquitoes.

Factoring a high loss rate of 20% (similar to what the USAAF had) you would need 100 bomber Mosquitoes. Which probably weren't available to Bomber Command at the time.

The USAAF lost most of theirs to fighters. This occurred during several hours of fighting as the bombers entered and withdrew from the target area. In the Mosquito case it is likely that would occur on only one of the legs.

Losses would probably be mostly to flak. Mosquito attacks could not be solely low level attacks, as that would have the defenders adapting quickly. The attack altitudes would, this, need to be varied so that one type of attack cannot be expected.

There is another downside to low level attacks, as demonstrated in the Shell House raid. While the first wave scored nearly 100% hits, one of the later aircraft hit a building and crashed away from the target. The following waves then proceeded to bomb the crash site, being confused by the smoke.

Shortround6 said:

There were only about 1700 Mosquito bombers built and the majority of those were from around the Spring/summer of 1943 on (several hundred completed after VE day.) Most, if not all of the ones from the Spring/summer of 1943 having two stage Merlin's which did wonders for the performance and survivability, something like 1000 of the bomber mosquitoes had the two stage engines. However one wonders how well a Lancaster with two stage engines and a pressure cabin for the pilot/Forward crew would have performed??

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313mph @ 18,300ft for the Lancaster MK VI @ 65,000lb MTOW. Still over 300mph @ 22,000ft. Service ceiling 27,000ft.

Maximum cruise speed 279mph @ 23,900ft.

http://www.wwiiaircraftperformance.org/Lancaster/jb675-level-speeds.jpg

http://www.wwiiaircraftperformance.org/Lancaster/Lancaster_VI_JB675_Performance.pdf

Shortround6 said:

However one wonders how well a Lancaster with two stage engines and a pressure cabin for the pilot/Forward crew would have performed??

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They thought about it, but expediency meant that the largest number as quickly as possible was what was needed, rather than developing a new variant so soon. The Lincoln was the next Lanc variant to go into production.

The problem for Mosquito operators is what Wuzak identified, not enough aircraft to go round for all those who wanted them. Production in Canada helped, but demand was still greater than supply.

The one problem I see with this scenario is that the Americans are not going to put their bombers to waste in favour of a British aircraft and nor is the RAF, especially since it had invested so much already in larger aircraft. Bigger bomb loads in greater amounts was what Bomber Command wanted and heavies like the Lanc and Halifax gave that, despite their weaknesses.

As an aside, Volkert's memorandum on bombing policy in 1937 described an unarmed bomber based on P.13/36 (that gave the Manchester and Halifax) parameters. Maximum bomb load was 8,000lb and it was powered by two Vultures.

The interesting part was that he did not think that precision attacks would be possible and that attacks against population centres would be the approach. The unarmed bomber, he reasoned, would be able to do this more efficiently than the armed bomber, its higher speed helping to reduce losses while carrying the same/similar bomb load.

wuzak said:

I have no doubt that the Mosquito could have provided a more useful contribution to the strategic bombing effort than it already did. The limiting factor was, as mentioned previously, the numbers of available bomber variants. And that was because of the other roles it was required to fill.

I never felt that the Mosquito could replace the Lancaster. My view was that it could have acted as a replacement or supplement to the B-17 during the daylight campaign.

One raid that I thought may be possible for the Mosquito would be the first Schweinfurt raid. The range is just about within the Mosquito's capability at low altitude.

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The numbers available were not limited by supply of materials as is often touted. DeHavilland at least is clear in his statements about that. The delivery dates are also heavily skewed by the hostility the air ministry showed towards it. As a design, the DH98 was ready for production as early as October 1938, but it would take until 1940 before it began to enter production and then only at a trickle. There were no real hitches in the production of the type (it was actually faster to build than a standard Blenheim turreted bomber) , just official opposition to it as a concept. the original type was designed to meet a specification of carrying 3000 lb bombload a minimum of 1500 miles. the Mosquito , even the early marks could achieve this easily. but the opposition to it as a bomber remained, and most of the early marks were completed as either unarmed recon versions or night fighters. Geoffrey DeHavilland had a bewildering array of variants he was willing to build from the start, so if the production was entered from an early stage rather than dithered about so that the crowning achievement of the Manchester could be built instead, the type could have been shown to fulfil many of the roles that it did.

Imagine if the type had started production in early 1939. It would have been entering squadron service by about June 1939. I believe its capabilities as a type would have forced BC to completely rethink its tactics. The great unknown is how the LW would react. their existing fighters, built around the Me 109 and Me 110 would immediately be shown to be inadequate, lacking both the speed an range to deal with the new bomber. Im tempted to think along the lines of an early introduction of the Me262 but that was still years away in 1939. For the moment Im just going to leave that an open question.

turning now to Schweinfurt/Regensburg option. The first thing that strikes me is that the assumption that losses for the Mosquito being the higher than a B-17 equipped force. I think that is incorrect. Historically the raid was a strike by 376 bombers of sixteen bomb groups against German heavy industry well beyond the range of escorting fighters. 60 bombers lost and 95 damaged, about 58 beyond economic repair.

The lead attack was the Regensburg group, which lost 24 bombers, and at least 60 damaged, 15 of the lost bombers were lost on the inbound leg. 126 of the 144 bombers released bombs over the target. The attack was late, and slow in delivery, giving the defenders plenty of time to get into position, land, refuel and be ready for the next attack.

If this element of the attack substituted Mosquito BXVIs for the B-17gs, instead of the approach speed being 180 mph, or less, it could have been 350mph for a hi approach. to increase bomb hits I would adopt a Hi-Lo-Med mission profile. Flak was noticeably low over Regensburg so losses to flak firing at an aircraft that within the target would be belting along at over 400 mph would be minimal. My guess is that for this strike element, losses might be 2-10 a/c, depending on how well it was delivered and the amount of advanced warning the LW received. One difficulty was that le mays group was tasked to stage through to Algeria after the hit, this would not be possible for the Mosquito hypothetical.

The main attack on Schweinfurt followed the same route basically as Le Mays Group. The organization and disposition of this force left a lot to be desired, and the increasing cloud cover forced the bombers to come in at sub-optimal altitudes. You cant lay this at the feet of the B-17 as a type, but you can say that because of the higher approach speed of the mosquito, the cloud would have been higher at the time of the approach (the cloud was descending as the day wore on) , the mosquito force would be far less constrained by cloud....they would have attacked higher and faster.

This time delay and altitude constraints is very significant to loss rates. The time lag allowed more than 300 defending fighters to be concentrated over or before the target. The time taken in the attacks also allowed many of the early intercepts to attack, land, refuel/rearm and hit the stream on the way out. Moreover at least two gruppen were able to use effectively the new unguided air to air rockets firing them into the tight defensive patterns the B-17s were using.

I am sure there are people here that have a better handle on the details of the battle compared to me, but from what I do know, it was a very bloody affair. Some 22 being shot down and a further 15 or so heavily damaged within the target area . The lead wing of 57 a/c was followed 15 mins later the other wings as they began their runs in. The lead group took many of the losses because the inbound approach was so slow, allowing the germans to be perfectly positioned for their attacks. Only 3 B-17s were brought down by flak, though many were damaged. 183 bombers managed to drop 950000 lbs of ordinance on the target. a total of 30 or so bombers were brought down or damaged within the target area. more time was lost as the bombers were forced to regroup over Meningen. they needed to stay together, as their primary defences, their turreted guns needed massed firepower to keep the losses low. Unfortunately this delay was used to good effect by their enemies.

The americans were again attacked as they retreated toward Brussels then home. At approximately 15:30 German fighters renewed their attacks, concentrating now on damaged bombers. Between 16:20 and 17:00 a covering force of 93 P-47s and 95 Spitfires arrived to provide withdrawal support, claiming 21 fighters shot down, but eight more bombers were lost before the force reached the North Sea, where three more crash-landed. The Schweinfurt force lost a total of 36 bombers and close to 60 damaged.

how might a Mosquito equipped force have fared in this scenario? It would both approach and leave faster, with no loiter time. Only head on attacks by the LW would be effective, and the numbers of fighters able to deploy might be half that achieved historically. We would need to model that battle to get a good idea of potential losses, but with half the number of defenders, only effective through half the attack angles, and no losses outside the target area you might suffer 5-10 Mosquito losses plus the 3, maybe 4 to flak There will be endless debates about how these losses might pan out, but I don't think it unreasonable to claim losses in the region of maybe 10 a/c lost . in exchange for that a force of say 550-600 Mosquitoes (roughly what I think the americans might potentially be able to put into the air) each carrying a 2000lb warload, might drop as much as 1,100,000 lbs of ordinance on the target. A critical point of argument might be the number of mosquito substitutes, but remember, my position is based on a premise of a 1938 entry into production and a 1939 entry into service, and probably a licence production agreement with the Americans. instead of building 7000 mosquitoes, 30000 would be nearer the total.

The problem there parsifal is that the Merlin 76/77, or even the 72/73 used for the IX and early XVIs, was not available at the time of Schweinfurt. Well, the 72/73 was just coming into production with the IX.

With an extra two years, there will be any number of nearly as good alternatives to choose from

Now we are into pure 'what iffery?'

The Mosquito was never planned to be in service before 1942, the stop/start prototype wasn't started until early 1940. Bowyer covers the early developments that led to the Mosquito, Contract 69990 for fifty bomber-reconnaissance aircraft was issued on 1st March 1940 to Specification B.1/40.

With the fall of Paris in June 1940 a plan of the month before was implemented. Production now concentrated on the Hurricane, Spitfire, Wellington, Whitley and Blenheim, research and development was to be concentrated on these five types. Any other work might be applied to second priority types, the Stirling, Manchester and Halifax, but not the Mosquito. This was not due to any innate hostility to the Mosquito. This was a rationalisation of resources in Britain's darkest hours, and the fact that the Mosquito, which existed only as a partially completed prototype and which was not expected to be in service for at least another 18 months was passed over seems perfectly reasonable, even with the hindsight that the decision makers did not have.

De Havilland, understandably, pleaded for the Mosquito to be allotted at least second priority status. Beaverbrook's right hand man (Patrick Hennessy) replied that it might be considered if fifty aircraft could be supplied in 1941. C.G. Long, de Havilland's chief development engineer went to London and showed Beaverbrook the material schedule for the Mosquito, showing that demands on the light metal industry would be light, high strength castings totalling 250 lb largely replaced forgings (only 30 lb) and machining was minimised; for instance a simple compression rubber undercarriage leg was used rather than an orthodox oleopneumatic leg.
On 11th July de Havilland promised fifty aircraft in 1941. On 12th July Hennessy re-instated the Mosquito project, with the proviso that it should not interfere with production of Tiger Moth and Oxford trainers (vital to RAF Training Command) or the repair of Hurricanes and Merlin engines which the company had recently undertaken (equally vital as the Battle of Britain began).

The Luftwaffe also had a hand in delaying the Mosquito. In the first two weeks of September 1940 the plants at Hatfield and Salisbury Hall lost 84,309 man hours to air raids. On 3rd October a hit and run raid by a single Ju 88 killed 21 de Havilland workers and wounded 70 more. About 80% of the raw materials and much work in progress for the Mosquito was lost.

If we are going to 'what if ?' let's at least stay within historical facts. The Mosquito prototype was delayed for about one month. It was never going to be in service, in numbers, years earlier. There was no innate resistance to the type at the Air Ministry, in fact, following the re-instatement, on 18th July, a letter asked that a fighter prototype also be developed. There was some unease about the concept of an unarmed bomber in 1940, but then there was unease about all sorts of other concepts too.

W4050 first flew on 25th November 1940. On 29th December a show was put on, at Langley, for Beaverbrook and assorted other VIPs (including the Hon. C D Howe, Canadian Minister of Munitions and Supply). Other aircraft showcased were the Hawker Tornado (Vulture), Gloster F9/37 (Peregrines), Philips and Powis fighter (Merlin), Short Stirling (Hercules) and Handley Page Halifax (Merlins). The D.H.98 made a good impression and such was the 'resistance' at the Air Ministry that the very next day Grp. Cpt. H E Forrow (MAP overseer at Hatfield) told de Havilland that another 150 Mosquitoes were to be ordered and that additional floor space, materials and sub-contracting capacity were to be sought, with a view to further 'substantial orders'.
On 11th January 1941 de Havilland were told to build a reconnaissance prototype and to finish the remaining 47 aircraft of order 69990 as 19 reconnaissance and 28 fighters (prototype ordered the previous July) but NO bombers. Bombers were likely to feature in the next order, and development flying was to continue with all three roles in mind.
The Air Ministry, far from resisting the development of the type, clearly saw it as an aircraft with potential in at least three different roles. It would eventually fulfill more than this, but we can hardly blame them for not anticipating this after one prototype had flown.

Cheers

Steve

The Mosquito MK XVI didn't fly until Jan 1st 1944 about 4 1/2 months after Schweinfurt, The MK IX with two stage Merlins first flew in March 24th 1943. Pretty much the same performance but lack of pressure cabin meant it was rougher on the crew than the XVI. Getting hundreds built and out to operational squadrons in 5 months????
These engines were rated 18lb boost as built (and developed) and boosted to 21lbs and sometimes 25lbs in service. Claiming that some other mark of engine could have done the Job months or year or more earlier may not be anywhere near as easy at it seems. The Original 2 stage engine, the Merlin 60 was limited to 9lb of boost and the Merlin 61 & 62 were limited to 15lbs. Granted all (except perhaps the 60) could cruise at the same limit 2650rpm and 7lbs boost.

The early proposal for the Mosquito (or the official requirement) was not for a plane to carry 3000lb for 1500miles but a plane to carry 1000lbs for 1500miles, speed not given in the book I was reading. Since the first ten production Mosquito bombers had a max bomb load of 1000lbs I believe the 3000lb number is in error. This is where the early (1939/40) production/service use of the Mosquito falls apart.
The 1938-39-40 engines and propellers and fuel were nowhere near as good as the 1941-42 single stage engines/props/fuel.
At best you can get the Merlin X engines as used in the Whitley and modify the cooling system to fit the Mosquito. However this means 1065hp for take off instead of 1280hp from even a Merlin 21, it means 1130hp at 5250ft instead of 1460hp at 6,250 in low gear and 1010hp at 17,750ft instead of 1430hp at 11,000ft (16lb boost) and more importantly 1185hp at 18,500ft (9lb) in high gear.

While a 1939 Mosquito would obviously be much better performing than a Blenheim, it would also be much worse than a 1942 Mosquito. In 1939 you have 87 octane fuel and the Propeller situation is questionable. Most Battles got 2 postition props but some bombers got constant speed. Even some of the constant speed props had rather restricted pitch ranges. Nobody was getting feathering props.
Blenheims went to carrying 100 octane in the outer tanks and 87 octane in the inner so they could use the 100 for take-off and combat and cruise on the 87 octane, most other bombers stayed with 87 octane until well into 1940.

A 1939 Mosquito with Merlin X engines, if was to keep the same power to weight ratio (for take-off and climb) as the Mosquito B IV would be limited to around 17900lbs and since the tare weight was about 13,400lbs for a B IV either you accept lower performance (and the 1939 fields were usually shorter than 1942 fields). or you accept less payload and less range. 500imp gallons is about 3600lbs, crew 400lbs, 360lbs oil (15imp per engine), bomb load is one 250lb bomb??? Granted a 1938 Mosquito might not have had armor or self sealing tanks but that sure doesn't help the loss the ratio.
Yes they would have run heavier and or cut fuel load but you don't get 1942 Mosquito Performance in 1939/40 anymore than you get Spitfire V performance in 1939. And a Spitfire V with belt fed cannon was carrying about 350lbs more guns and ammo than a Spitfire MK I.

A 1940/41 Mosquito is out of the question. The only de Havilland aircraft, flying in anything like the time frame to make this would have been the D.H. 91 'Albatross' airliner, first flight 20th May 1937 (ignoring the almost exact contemporary 'Moth Minor').
The D.H.91 might have been a remarkable aircraft (the mail carrier had a 6,000lb payload and could fly to Berlin and back at 11,000ft) but it used four engines and P.13/36 called for 'a twin engined medium bomber for worldwide use'.

Here is a very abridged time line of the development of the Mosquito concept.

April 1938. A twin engine (Merlin) Albatross estimate is made, with Hercules and Sabre comparisons.

27th July 1938. De Havilland write that the specification cannot be met on two Merlins. If speed was paramount then only half the specified load of 4,000 lb could be carried. If load was paramount then a larger slower aircraft could be built. Note that we are at the end of July 1938 and the concept of the Mosquito is still to be developed.

October 1938. De Havilland and C C Walker pitch the idea of a fast unarmed bomber to the Air Ministry for the first time. It arouses little interest. Why would it? The RAF has the Blenheim, Whitley, Hampden and Wellington in production, all metal and armed bombers. The de Havilland proposal ran contrary to the general scheme on which the RAF was being expanded and it came from a company with virtually no experience of working with the Air Ministry.
Crucially there was also a prevalent view in the Air Ministry that the Germans would develop ever faster fighters (as the British themselves intended to do) and this might leave an unarmed bomber in a precarious position.

De Havilland looked at various specifications and worked up options for some over the next 12 months. None were equivalent to what would become the Mosquito. They even looked at an adaptation of the D.H. 95 and also worked on Specification B.18/38, which became the Albermarle, but to no effect. The concept of an unarmed fast bomber had little support until the outbreak of the war. The closest we come to what would become the Mosquito was a small, unarmed, twin Merlin aircraft to carry 1,000 lbs of bombs 1,500 miles. This was one of three options (including a twin Griffon version) presented shortly after the outbreak of war, in September 1939.

22nd November 1939,. Conference with the Air Member for Development (Freeman). He supports the case for an unarmed reconnaissance-bomber version, though there is still some pressure for a third crew member.

12 December 1939. Despite efforts by some to abandon the project Freeman again argues the case for the two man, twin Merlin, aircraft. It was the reconnaissance role which kept the project alive, but bomber and fighter variants were not excluded.

29th December. Mock up conference. Specification B.1/40 drawn up on this basis.

1st March 1940. Contract issued for 50 aircraft, including prototype.

I just can't see, given this timeline, that a Mosquito carrying even 1,000 lbs of bombs could have been available in 1940/41.

Cheers

Steve

It s certainly a what if, but its a what if because of the entrenched opposition to the basic concept that instead preferred a bomber with heavy lift and defensive armament.

The alternatives were never seriously considered.

De Havilland claimed he could have production of the DH 98 perhaps an earlier permutation of it, from October 1938, I believe him.

What stopped it was not any major technical difficulties. but rather disinterest and downright prejudice. such prejudice was ferocious at times. So the design languished from September 1938 to March 1940. It took from March to November, 8 months, for the bomber prototype to be made ready for production, and a further 6 months to get the pru version ready. the pru role was the only one the air ministry was interested in at that time, and then only very grudgingly

I think it reasonable to undertake some what iffery for this debate. we are looking at the possibilities of the mosquito as the primary bomber in place of the Manchester/Halifax . That would pre-suppose that somehow the preconceptions that dogged the raf in that period as to how a bomber might be are overcome. It was perfectly feasible from a technical standpoint according to DH, but not from a political or doctrinal. Without such a doctrinal shift it is certainly not possible to even consider the possibility of a mosquito (or a mosquito equivalent)as replacing the slow, heavily defended bomber that the RAF finished up settling on in the finish.

stona said:

I just can't see, given this timeline, that a Mosquito carrying even 1,000 lbs of bombs could have been available in 1940/41.

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Given that time line it couldn't but even changing the time line to DH being given the go ahead in July of 1938 means they are planning the aircraft around Merlin X engines, 87 octane fuel (Rolls did announce power levels using 100 octane at the 1938 Paris air show but nobody knew when 100 octane would be available in service quantities, and 1938 100 octane may not have been the same as 1940 100 octane, 1940 100 octane was NOT the same as 1942 100/130) and the RAF preferred less than optimum propellers.
Since a Merlin X weighed within a few dozen pounds of a Merlin XX series engine there is no weight saving their and except perhaps on the props no weight savings much of anywhere else.
A Merlin X is pretty much a Merlin III with a two speed supercharger so it is subject to pretty much the limitations of a Merlin III.
Like Climb rating of 2600rpm instead of 2850rpm used on the later engines.
A Mosquito using such engines might be able to cruise at around 310-315mph using max weak mixture (assuming it is within a few MPH Of a Spitfire with the same basic engine [same supercharger although different ratio and same basic structure/crankcase/cylinder blocks)])

Now compare it to some of the early A-20s (R-2600 versions) which could hit 340-350mph at around 12,000ft top speed and cruise at a touch over 300mph at max cruise (rich). Granted the A-20s had the operational radius of a thrown rock with a parachute attached but the A-20s were hardly invulnerable due to speed (or guns) and their bomb load was more in the 1000-1500lb range (they got better later).

I would also note that the Halifax MK II (Merlin XX engines) had a ceiling 3,000ft higher than a Halifax MK I (Merlin X ) despite being 1000lbs heavier and fitted with that big egg shaped top turret (MK 1s had no top turret). Halifax II could also take-off and reach 50ft in 200yds less distance than the Halifax I despite the extra 1000lbs.

Now perhaps DH was right and it was possible to build the Mosquito airframe in 1939-40, would the resulting aircraft using the engines available ( and I mean actually existing, not available in a production sense, first 75 Halifax's got Merlin X engines) and props and fuel have actually performed combat missions as some people seem to think.
The Mosquito was a fairly tight design. 1000lbs of fuel is around 130-135IMP gallons so cutting gross weight by even 1000lbs for the lower powered engines means either a considerable cut in range or cutting the bomb load in 1/2 compared to a B IV at 21,462lbs. gross.
Light weight was 15,318lbs so you have 6144lb to play with. Crew is about 400lbs 536 IMP gallons is about 3900lbs depending on conversion so even a standard Mosquito bomber is just over max with full fuel, crew and 2000lbs of bombs.

Let's see what the Soviets managed in 1941 with Pe-2, that have had on disposition two M-105 engines of 1100 CV (1085 HP) for take off, and 1000 Cv at 13000 ft:
- max bomb load 2200 lbs
- normal bomb load 1320 lbs
- max speed (clean, at altitude) 340 mph
- max range (not radius) 745 miles
- internal fuel max 310 imp gals
- can dive bomb
- has machine guns (but not too many and not of great firepower)
- restricted bomb bay

The gun-less DH bomber of 1940 with two Merlin X engines should've been in the ballpark IMO, minus guns and dive bombing capability. So not much of a startegic bomber, but still useful when compared with what was available.

In 1940 Germany has the early Ju 88, with a better payload vs. range capability, but slower.

parsifal said:

De Havilland claimed he could have production of the DH 98 perhaps an earlier permutation of it, from October 1938, I believe him..

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He had a very selective memory, because the concept that led to the Mosquito didn't exist in 1937 (I'm giving them a year for development). The Albatross only flew in May 1937 and it was from this that, eventually, the Mosquito was derived.

The unarmed bomber concept languished for about one year, essentially 1938-1939, and the prejudice as you call it was founded on the fear that the Germans would develop ever faster fighters leaving such a machine vulnerable in the future. Such reservations were expressed in various development meetings of the time. Today we would say it was not future proof. It was Freeman that saved the project, arguing in the meeting I cited above for a high speed, unarmed, reconnaissance aircraft.

There was ZERO chance of having a high speed bomber with anything approaching the performance of what we now call the Mosquito in 1938 or even 1940, it was pure hubris from de Havilland.

I'd like to see some evidence of 'downright prejudice' against the Mosquito. There were arguments against the unarmed fast bomber concept, but these were always reasoned and based on genuine fears that this would not be the way to go. We have the benefit of hindsight, the decision makers at the time did not. Slower self defending bombers may have been a more conservative option, but they were also the safer option at the time.
Did any other air force adopt an unarmed bomber in the 1930s?

Cheers

Steve

The fast bomber concept got a big boost during the Spanish civil war and with the introduction of the first monoplane retracting landing gear bombers.
For the British the Blenheim and the Gladiator were first issued to squadrons within 1-2 months of each other. The Hurricane entered service almost 9 months later (with 4 aircraft issued to the first squadron.) The Spitfire was issued to it's first service squadron about 9 months after that or 17-18 months after the Blenheim.
A fast bomber, either unarmed or with light armament (1-3 rifle caliber MGs) might have a "window" of opportunity to operate with near immunity vs enemy fighters of a number of months but it is always going to be easier to build a faster fighter using the same level of technology . So the unarmed or lightly armed bomber will come to grief at some point.
Now the heavily armed bomber didn't really work either but that doesn't automatically mean the unarmed bomber was the correct answer.

Think of Mosquitoes trying to do daylight raids against defense of P-51 Mustangs. Both planes using essentially the same engine and fuel or similar level of technology.
We have the luxury of knowing the Germans never got ( or capitalized on) high performance fuels and two stage superchargers. Nobody was 100% sure what the Germans might to might not introduce into service 6 to 18 months in the future at any given time during the war.

Quoting Bowyer.

"In a second letter, sent July 27 [1938] they [de Havilland] concluded that the specification could not be met on two Merlins...

'A good bomber could be produced using Merlins' (here is the first twinkle of the idea that became the Mosquito) 'but to meet this specification double the power would be needed.' ...

A two Merlin compromise bomber was arrived at on 11th August, with a top speed of 260 mph and a range of 1,500 miles."

If de Havilland were considering a two Merlin bomber with that level of performance in August 1938 it is patently impossible that anything resembling a Mosquito could have been in production two months later. There were not even any drawings for it in August, it was simply an internal company project, being discussed (in the letters) with Freeman.
I don't know when de Havilland made the claim, but I suggest it is influenced by hindsight. He must have been referring to the August 'compromise bomber' a compromise he, or at least his team at Hatfield, disliked and certainly had no intention of building.

It is obvious that a bomber with a maximum speed of 260 mph can't operate unarmed at a time when fighters capable of much higher speeds were already in or entering service. There is no conceivable reason that the Air Ministry would have supported such a project.

In October 1938, when de Havilland suggests a form of Mosquito might be in production, the company was proposing a twin Merlin Albatross retaining wooden construction, armed, with a top speed of 300 mph.
It isn't until more than a year later that a twin Merlin aircraft with a top speeds of 419 and 409 mph were being proposed. The Ministry was understandably sceptical of these figures, several other recent aircraft had failed to live up to expectation, and de Havilland was not a company which had previously done much business with the Ministry.

Cheers

Steve

There are arguments for and against the unarmed bomber, the arguments against seem to be well made excepting that this philosophy ended with 2000 Fairey Battles being ordered. How on earth could a Fairey Battle ever defend itself? Similarly the UKs main bombers at the outbreak of the war were completely unable to defend themselves in daylight either alone or in groups and any one with any sense could see that. They couldnt attack in daylight and they couldnt hit anything at night. The UKs strategic bombers in 1939/42 had a strategy that was no more than an aspiration.

The time lines and correspondence quoted show that the mosquito could not have ever come into being before it did simply because their client was obsessed with defensive armament maximum possible bomb load and more aircrew.

Here is a fantasy scenario. The Air Ministry is concerned about over optimistic proposals for aircraft and so commission De Havilland and A N other to produce two racers both with two Merlin engines one carrying 2000LBs and the other 4000LBs capable of 1500miles range. Contracts and first flights orders into production follow in line with the Spitfire the Fairey Battle is cancelled resulting in 500 twin engined fighter bomber/night fighters and 500 bombers in service in 1940.

Shortround6 said:

Think of Mosquitoes trying to do daylight raids against defense of P-51 Mustangs. Both planes using essentially the same engine and fuel or similar level of technology.
We have the luxury of knowing the Germans never got ( or capitalized on) high performance fuels and two stage superchargers. Nobody was 100% sure what the Germans might to might not introduce into service 6 to 18 months in the future at any given time during the war.

Click to expand...

The problem with the allied strategic bomber effort was the strategy was frequently obvious, when the defender knows your target and you are travelling towards it at 180MPH at best then the defender has an advantage. A Mustang has a speed advantage when he gets to the bombers altitude but not before, if an intruder is doing 300MPH or more that is 5 miles a minute, in the time taken to track an intruder, scramble an interceptor and vector it to altitude the intruder is in a completely different area of the sky.