The de Havilland Mosquito and the heavy bombers

In the last WW2 Podcast I discovered the British de Havilland Mosquito could deliver a similar payload to Berlin, as the American B-17. I was surprised.

On the face of it the statement is true. The B-17 would carry 3,500b of bombs to Berlin and the Mosquito 4,000lbs. But the devil is in the detail, the Mosquito had to deliver its payload as either one bomb of 4,000lbs or as four 500lbs bombs. Whereas the B-17 payload would allow for a much wider variation, so was more flexible.

Another thing about the Mosquito is the survival rate of the planes and crew, an argument of speed over defence. From November 1943 to March 1944 Berlin was repeatedly bombed, the loss rate of the heavy bombers (predominantly Lancaster’s) was 5.1%, for the Mosquito it was 0.5%.

The War Office statistician, Freeman Dyson investigated the high losses on Lancaster’s [1]Lancaster: The Biography by Tony Iveson. He noted crews were less likely to survive bailing out in a Lancaster (15% chance) than a B-17 (50% chance) or the Halifax (25% chance). He suggested the very small escape hatch on the Lancaster might partly be to blame.

He also argued for smaller crews. If losses were to be accepted the fewer airmen on the plane the better. To achieve this he suggested removing the two defensive gun positions. Not only would this reduce the crew size but save enough weight and increase the Lancaster’s speed by around 50 mph.

All of which, in a round about way, made me think why did they not just build more mosquitos? It was fast, it had a decent bomb load (especially when comparing it to the American B-17) and only had a crew of two.

It was an all wood construction, though this worked for and against it when it came to production. On one hand parts could be made in workshops the length and breadth of the Empire. This made it very difficult to interrupt production. But it needed skilled wood workers, where as with other aluminium airframe planes it was much easier to train workers to do the job. With a shortage of men, women could be brought in to fill the gaps in the factories.

“The British, who can afford aluminium better than we can, knock together a beautiful wooden aircraft that every piano factory over there is building”. Hermann Göring [2]Wikipedia

I wondered how the Mosquito and Lancaster compared?

Speed Payload Range Crew No. Built
Mosquito [3]  415mph 4000lbs 1485 miles 2 7781
Lancaster [4] 200mph 22000lbs 2530 miles 7 7377
B-17 [5]  287mph 4000lbs 2000 miles 10  12731[6]Wikipedia

So if we take theoretical “thousand bomber raid” of Lancaster bombers, they could deliver a staggering 9,821 tons of explosives. It would take five thousand, five hundred Mosquito’s to deliver that amount.

One thousand Lancaster’s would have a crew of 7,000 men, five thousand, five hundred Mosquitos would need 11,000 men!

On the face of it that justifies the use of the heavy bomber by utilising fewer aircrew. But what about accuracy?

An example of the tremendous accuracy achieved by Mosquitos can be shown by comparing figures for the attacks on the V-weapons sites. The average tonnage of bombs required to destroy one of these sites by B-17 Flying Fortresses was 165; for B26 Marauders it was 182 tons and for B25 Mitchells 219 tons. The average for the Mosquito was just under 40 tons! [7]

Where does that leave us?

Perhaps it was actually best employed in the role it was so often used, as part of the RAF Pathfinder Force. Flying ahead of the main bomber stream with their speed and accuracy they were ideal at marking targets for those that followed.