When do too many minor changes require a completely new design?

T. A. Gardner

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Another set of great examples are some of the German aircraft design programs of WW 2 like the Ar 240 or the Bomber B program. You have aircraft that are 10 to 20 prototypes into development with new wings, new engines, redesigned totally new tail surfaces, etc. At some point early on, the RLM should have said, "Stop!" but they didn't.
 

robunos

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At some point early on, the RLM should have said, "Stop!" but they didn't.

To be fair, in the case of the 'Bomber B' (Junkers Ju288), it was the RLM that caused the problem.
It wasn't until the Ju288 prototypes has been designed, built, and flown that the RLM changed the specification, increasing the crew from three to four.
Then the specified engine, the Jumo 222, proved to be a failure, and the backup BMW 801 series was now not powerful enough, due to the weight increase caused by the crew increase, which forced a further change to the DB 610 . . .

cheers,
Robin.
 

T. A. Gardner

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At some point early on, the RLM should have said, "Stop!" but they didn't.

To be fair, in the case of the 'Bomber B' (Junkers Ju288), it was the RLM that caused the problem.
It wasn't until the Ju288 prototypes has been designed, built, and flown that the RLM changed the specification, increasing the crew from three to four.
Then the specified engine, the Jumo 222, proved to be a failure, and the backup BMW 801 series was now not powerful enough, due to the weight increase caused by the crew increase, which forced a further change to the DB 610 . . .

cheers,
Robin.
It wasn't just the Ju 288. The Fw 191 was specified as all-electric, and ran into all sorts of issues. Interestingly, the bomber that actually ended up meeting the spec--a day late and a dollar short-- was the Hs 130 that originally wasn't even part of the program.
 

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