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Old 31st Jan 2009, 16:21
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Join Date: Mar 2000
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So how did it work before the B707?
Comet excepted, there were no jet transports prior to the 707, so the reference to mach number crossover was not a consideration in the climb.

However, of one looks closely at the limitations for some 4-engine piston transports, there will be a reference to maximum mach number, which could be a consideration during descent.
This was investigated during original flight test (with a mach meter fitted) however the aircraft, when delivered, had the mach meter removed.
Instead, the Vne was listed as a sliding scale, dependant on altitude...IE: the higher the altitude (beyond a certain point), the lower the Vne.

Mach number effects were a definite consideration on two specific 4-engine piston types, the DC-7 and the L1649 Constellation, as these two aircraft were designed for long range high(er) altitude, high(er) speed flight.
Specifically for descent, both of these types were fitted with 'speed brakes'...although not the type you might think....the main landing gear could be lowered (independantly of the nose gear, which remained retracted) for speed reduction.
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