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Old 30th October 2007 | 20:52
  #6 (permalink)  
411A
 
Joined: Mar 2000
Posts: 8,571
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From: Arizona USA
Not an easy task, windriver.
For example.
Lets look at two engine types on one substantially the same airplane....the B707 long body intercontinental model.
The earlier type had P&W JT4A straight-pipe engines.
The later airplane had JT3A fan engines.
Both about the same thrust at sea level.
Yet, because the fan engine moved a much larger volume of air on takeoff, runway performance was quite good, for the time.
OTOH, the straight-pipe JT4A, not being a fan engine, suffered severly with runway performance...rolling 11000+ feet on a 12,000 foot runway was not uncommon.
And yet, up high, the straight-pipe engine was very efficient...FL370 and above
The fan powered airplane suffered greatly at these higher levels...it simpy ran out of gas (performance-wise) at these higher altitudes.
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