said, it was at the limit of it's potential.
The last -7R engines were significantly different when compared with the -3's: Improved fan/case, compressor (from the -7Q on it had 16 stages), combustion chamber & turbine blades (single crystal), different materials, different seals.
Sub-systems were also greatly improved, especially the compressor control, fuel metering and case cooling systems.
From a throttle bar in the cockpit, turbine reversers and water injection to an electronic engine control. The list goes on.
|Quoting Thrust (Thread starter):|
how many 747s that carried the original JT9D-3s were retrofitted with the JT9D-7As
Probably most of them had there original -3 engines upgraded to -7 and subsequent upratings to -7A, F & J.
Most of the -7A's I saw were originally built as -3.
|Quoting 747classic (Reply 4):|
AFAIK both nacelles can still be used on all subtypes of the first JT-9D series, produced under Type Certificate Certificate E20EA and the installed nacelle type is not an indicator for the installed subtype of JT-9D engine on that aircraft.
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