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Having an engine that is as good as one's current fighter have also can help. Do we really need 4 crew members for a bomber aircraft to do it's mission (during a day), plus the gunners?
Yep, I'm referring to the B-26.
You have to remember that the British got lucky, very lucky, with the Mosquito. Expecting the same amount of "luck" with a variety of other designs may not be realistic.
I don't think 'luck' has anything to do with it.
I don't think 'luck' has anything to do with it. There was a pre-disposition at the time (contrary to what the popular view would have us all believe) within the British Air Ministry that fast bombers offered much and although the Mossie was initially not what the chaps had in mind, they certainly got it once it was demonstrated, pretty much within days of its first flight. There were a few ideas on what a fast bomber should be wihin the RAF and much discussion was done on the idea, particularly after George Volkert produced his paper on fast bombers in 1937. The thing that turned the decisions against the unarmed bit was the success, or at least the promise of the power operated gun turret and all the bomber specifications underway at the time (B.12/36, P.13/36 and so on) stipulated them for defence. Few other countries truly embraced the concept of a true fast bomber ('Speed Bomber' as Ludlow Hewitt called the armed fast bomber); the Luftwaffe did and the Ju 88, whilst not possessing the all out performance of the Mossie, proved a very competent and versatile machine that gave excellent service.
As for its design, the Mosquito was a sound, well thought out machine with little advance over contemporaries. Nothing that had not been tried before, just current technology done really well (unlike the Whirlwind!), so no luck involved at all.
As far as improved engines go, The A-20 kept pretty much the same engines after switching to the R-2600s (last few batches got 1700hp engines) B-25s had 1700hp engines all the way through, B-26s went from 1850 to 1920-2000hp engines.
Luck has to do with the way somethings developed and reputation. It sometimes took a lot of sweat, 12-14 hour days to make some of that "luck" actually pan out.
The "Luck" comes in with the Mossie actually exceeding initial performance estimates
A fitting description to many of my wife's my summer days
Again, I don't think it's luck, I think its very clever design, streamlining, drag reduction. Although I agree with you, pbehn in that the choice of Merlin was good fortune, but there really was no alternative and again, low drag came into the equation; the engine having a relatively low frontal area and possessing the power output to take advantage of the drag reduction measures applied to the airframe. Sometimes, designers just get it right, despite delays, technical difficulties and so on, so the machine, once the problems are sorted really comes into its own because its a great design to begin with. It's not luck.
I would say the most important thing for a fast bomber is that it must be fast at all altitudes. For a bomber flying at 350mph/30,000ft the defence must climb to that altitude it is difficult to vector a fighter to a plane travelling at 350mph at 30,000ft when he is climbing. By the time they are up to 30,000ft the bomber may be a huge distance away. For a bomber at low level the defence has completely different problems of finding tracking and distribution of resources.