'Wooden Wonder'
Why the de Havilland Mosquito could not replace the heavies
When de Havilland’s Mosquito prototype W4050 first took to the skies, it seemed as though the elusive promise of the ‘Schnellbomber’ had at last been realised.
Here was a machine which, despite being twin engined and weighing more than double the weight of a Spitfire, was faster than the legendary Supermarine fighter. De Havilland had resisted the calls of the establishment to add armament for self-defence, recognising the ever decreasing returns of adding armament that increased weight, which reduced top speed, only to add still more defences to counter for reducing speed.
The Mosquito was a ‘pure' ship in many respects. With her lightweight construction and fantastic power from twin Rolls-Royce Merlin engines, she would simply approach and depart the target at such speed that enemy fighters would be unable to catch her.
Losses among the fleet reflect the success of this simple premise. Of all Bomber Command types, the Mosquito enjoyed the lowest loss rate per sortie by a considerable margin, clocking in at just under one per cent on average. Compare that with the vaunted Lancaster, at between two and three per cent, and the Halifax and Wellington which saw even higher rates.
The difference reflects of course the approach in how missions were flown - and this is exactly the point often made in hindsight:
Instead of filling the skies with heavy bombers that carried between eight and ten men into harm's way, couldn’t the job have been done with thousands of Mosquitos? And it’s not just Bomber Command that are usually pointed to, but particularly the daytime campaign fought by the United States Army Air Forces’ Eighth Air Force.
Considering the latter, the first misconception that needs addressing is payload.
The argument usually goes along the lines of ‘the Mosquito could carry more than a B-17, and further’. To really get into that, we need to look at the missions flown by the eighth in more detail and also the configurations of both aircraft.
It’s in those configurations - or combat load outs as we might say today - that the comparison quickly becomes a grey area. Even the newest aviation students understand the relationship between payload and range, and that is important to consider here.
The very first mission by B-17s in occupied Europe was on 17th August 1942, when twelve aircraft from the 97th Bomb Group attacked marshalling yards near Rouen. Each bomber carried between two and three thousand pounds of ordnance - well short of the six thousand pounds that could be carried on shorter range missions.
But incredibly the B-17E could - if necessary - carry a maximum of an impressive twenty thousand, eight hundred pounds of bombs with the addition of external stores. Such a load out would limit the raid to an extremely short range, and so in practice numbers were much more modest to achieve the distances needed for deep penetration. For example:
At a four thousand pound load, the B-17E could haul its ordnance around 2,000 miles. For a B-17F carrying six thousand pounds, that distance falls by around 35% to 1,300 miles. Probably one of the best known B-17 deep penetration raids - the first Schweinfurt raid on 17th August 1943 - saw aircraft carry between four and five thousand pounds each; different Bomb Groups often had differing load outs. That mission saw the target attacked at a distance of around 400 miles from the British coast, requiring aircraft to fly around a thousand miles total distance once we factor in climbing and assembly.
So let’s hang our hat on something - a benchmark of a payload of five thousand pounds over a total distance of one thousand miles.
Time to bring in the Mosquito - to try and keep the comparison as accurate as possible, we’ll pick a variant in wide use at the time of the Schweinfurt raid - the B Mark IV, which served among units such as 2 Group and the Pathfinder units of 8 Group.
The standard load out for a Mark IV in August 1943 was around two thousand pounds, carrying four five hundred pound bombs - a recent improvement from four two hundred and fifty pound bombs. Also of note and introduced four months earlier was the conversion of some Mark IVs to carry the four thousand pound ‘Cookie’, but this was not a ‘mainstream’ configuration at the time so to keep the field level, we will stick with a two thousand pound payload.
Sources vary considerably on operational range for the Mark IV at this weight, but even the worst case of near twelve hundred miles puts Schweinfurt easily in striking distance.
And so for our comparative Schweinfurt missions we have B-17s at a payload of five thousand pounds each, and Mosquito B Mark IVs at two thousand pounds each. That is just the first of many points for us to examine and compare, there is much more to follow!
230 aircraft were despatched by the eighth on 17th August 1943. That constituted a total payload effort against the target - for our purposes - of one million, one hundred and fifty thousand pounds. A quick bit of arithmetic tells us we would need to launch 575 Mosquito B Mark IVs to achieve the same.
It’s no surprise that we need almost three times the fleet to lift the same payload - but that does at least put paid to the old quote ‘the Mosquito could carry the payload of a B-17’. Even the ‘cookie carrier’ Mark IVs could not transport five thousand pounds on that day in the war.
But, there's much more to examine.
The human cost is - of course - a huge factor in this discussion.
Each B-17 represented ten men in harm’s way, while a Mosquito was crewed by just two - the pilot and navigator. So on our Schweinfurt missions the eighth is putting 2,300 men into the air, while our 575 Mosquitos carry 1,150 men aloft - exactly half of the commitment.
Perhaps an instructive way to further examine that is to look at the loss rate for the actual first Schweinfurt raid.
36 of the 230 B-17s launched were lost. That represents a tragic - and unsustainable - rate of nearly sixteen per cent; some 360 airmen either killed, captured or on the run in enemy territory.
It’s a fair assumption that our Mosquito raid of 575 aircraft would have suffered a lower rate of loss - the rate of loss for the B-17 was for instance particularly high in 1943, but we also know instinctively that a Mosquito is going to be able to better evade fighters and flak than a B-17 can.
However - let’s examine worst case and assume the Reich has a good day, inflicting the same rate of loss. In that case, sixteen per cent attrition equals 92 aircraft, and 184 airmen killed, captured or missing. That’s half the cost in human lives.
If we take the Mosquito’s historical loss rate though of under one per cent, our mass attack of nearly six hundred aircraft might see losses of only five or six machines. But this is where it gets tricky - the Mosquito was not being used in this way at the time.
Nuisance raids in autumn 1943 - as they were then called - saw losses somewhere close to two percent. That again is impressive, but not itself representative of a massed formation of over six hundred aircraft arriving over a particularly heavily defended target. Nuisance raids were usually a few dozen aircraft, or even less.
So can we say anything categorically about the human cost?
Only that it would certainly have been less had the Mosquito carried the burden of strategic bombing. If our fictional Mosquito raid encountered the same attrition as the actual B-17 raid, around 180 airmen would have lived that otherwise would not have, for the same payload delivered. In actual fact many more would likely have survived.
On the face of it then it seems a no-brainer. The Mosquito advocates win the day.
But context is key.
We must put ourselves in the minds of the planners.
The Second World War was as much a struggle of economies as it was political systems. It was the economy of warfare that drove the success of types like the Lancaster - carrying the maximum possible payload per aircraft over the greatest possible distance.
Production capacity then is as important a consideration as anything else in the minds of those leading on the implementation of strategy, particularly in an existential conflict. Something we just can’t relate to today.
Comparing the production cost of a Flying Fortress against a Mosquito is a tough ask - not least because production techniques themselves improved throughout the war, considerably so in the case of the former - and then there is the obvious difference in material used.
For example, the hours needed to produce a B-17 fell dramatically from 35,400 at the Seattle plant in 1943 to just 18,600 - around half the previous total - in 1944. Direct comparison between the types and the national industries is tough, but there is some compelling evidence:
If we look at Mosquito production against British heavies, a 1944 Air Ministry document puts Mosquito cost at around 40 per cent of that needed to build a Lancaster (450 ‘man months’ vs 1,160), where a ‘man month’ is 195 man hours.
To further inform, a 1942 Air Ministry data point gives just over 74,000 hours of effort as the total to produce the 201st Lancaster Mark I. Halifax and Wellington ratios in this memo line up with the 1944 document, so the two sources can be reasonably compared.
We have a good indication then that a Mosquito cost 40 per cent of the effort of a Lancaster to produce, and that this ratio was broadly consistent 1942-1944. Some other data points support this - in 1945 post-war sales in France sought 15,000 pounds for a Mosquito FB.VI against 37 to 40 thousand for a Lancaster Mark I.
Applying 40 per cent then to those Lancaster hours reported gives around 29,000 hours of effort for the Mosquito. We can as a result say with some degree of confidence that in fact, evidence indicates the economic cost of producing B-17s and Mosquitos was in fact broadly in the same range, perhaps even cheaper for the former later in 1944. Unsurprisingly perhaps give the incredible economic might of the USA that was unleashed by the conflict.
So, with the mind of a planner, we return to the Schweinfurt scenario.
In late 1943 we have a heavy that costs about the same to produce as a twin engined fighter-bomber, and therefore using our 575 B Mark IVs represents a near tripling of the economic cost to mount the raid.
It’s a cold analysis of economics against human life - but I’d suggest that’s what the Second World War frequently was. Let’s not forget that those additional production hours were needed for other weapons and equipment; ships, tanks and aircraft.
The wooden construction of the Mosquito is also potentially a bit of a ‘red herring’ - Air Ministry records again show that the production cost was comparable to the all-metal Bristol Beaufighter, so the use of wood was more about the availability of strategic materials than any perceived saving in cost.
There are other considerations to employing three times the number of aircraft to get the job done.
The Short Stirling’s famously constrained wingspan was born of an Air Ministry concern that Britain would run out of airfield real estate, and if types like the Mosquito really did replace the heavies like the B-17, B-24 and Lancaster those fears could easily be realised. De Havilland’s design had around half the wingspan of a B-17 or Lancaster, not a third, so that requirement to multiply the number of airframes by three - even more to rival Lancaster tonnage - would be quite impactful in terms of hangar space and airfield size.
OK - so where does this all leave us?
I think first to try and conclude we have to treat the two campaigns separately - as indeed they very much were in methods and objectives.
Turning first to Bomber Command’s night campaign of area bombing - the question is tonnage.
With its four thousand pound capacity, the B Mark IV could not hope to match the Lancaster with its fourteen thousand pounds and more capacity, or even the thirteen thousand pounds of the Halifax. Anywhere between four and seven Mosquitos would be needed to carry that same load dependent upon configuration, and seven Mosquitos equalled the production effort of almost three Lancasters.
And the make up within that tonnage is important too - heavies carried a combination of cookies and incendiaries to achieve their effects, so a Mosquito force would need to do the same. No single aircraft could carry the combination.
And even four Mosquitos to replace a Lancaster involves sending eight men aloft in place of seven, negating to some extent the advantages of favourable loss rates. If you need five or more Mosquitos to replace a Lancaster load out, you have definitely completely eliminated the advantage of higher survivability.
Considering the Eighth Air Force’s daylight campaign, the question is more one of industrial capacity.
Looking again to our Schweinfurt example, you need 575 Mark IVs to deliver the effect of 230 B-17s. But this time, come late 1943, the production cost of the two aircraft is possibly within the margin of error. So for planners, the proposal would be to expend almost three times the production effort to deliver the same tonnage to the target. And Merlin engines were not exactly growing on trees either.
Even in Bomber Command’s case too, because you need so many airframes, per ton of bombs dropped a Mosquito force was a much more expensive proposition. Scaling up Mosquito production would also present huge challenges - while the use of wood products was a coup in strategic resources, the skilled labour needed for assembly was not as simple to access in quantity.
The counter argument of the human cost in either campaign is compelling to us today in hindsight, but in reality it would be the industrial burdens of the time that would drive the planners - particularly in an existential conflict. Especially since the best way to save lives was to end the war as soon as possible, and the best way to do that was to have as many aircraft as possible deliver as much ordnance as possible.
There is one additional point to consider I think:
Under Operation POINT BLANK, the Eighth Air Force’s campaign was as much about drawing the Luftwaffe into battle as it was about hitting strategic targets. This meant that the bombers and their escorts were of equal importance in the plan.
If the relatively cumbersome heavies are replaced with an aircraft that can outrun enemy fighters, the decisive aerial battles of 1943 and 1944 likely do not happen. Precision attacks are possibly more practical and deliver greater success, but the Jagdwaffe could well survive as a potent force to continue contesting aerial superiority, jeopardising the conduct of D-Day in mid-1944.
The 'wooden wonder’ then, was a wonder no doubt - but I don’t subscribe to the idea that it could have taken on the the burden of the strategic bombing campaign for either service, during day or night.
As always, what’s more important than agreeing is that we all explore and understand the facts behind our arguments. That will always keep the conversation alive, and therefore the memory of these courageous airmen.
Be sure to let me know your own views!
