Ahha! the good old JT9d-3a anyone for a description of the BLEEDS system?
3.0 bleed ring.
3.5 bleed valves (x4)
4.0 bleed vavles (x2) more commonly referred to as the 15th stage.
8th stage customer bleed.
15th stage customer bleed.
7th stage bearing pressurisation bleed.
Now the above bleed valves worked in various combinations of:-
Start bleeds.
Tandem bleeds.
Surge bleeds.
Reverse bleeds.
It was not uncommon for the early engines to stall on a accel. so a 'bodie tube' was fitted between the (IIRC
) the 3.0 bleed actuator and the lower left 3.5 bleed valve controller.
JT9d-7a/ah/cn gradually improved and the 15th stage bleed valves were removed and then one of the 3.5 bleed valves went as the design of the hp compresor improved.
Even the later JT9d-7q and the -r4g2 had stall problems notibly affecting the fan. N2 reset solenoid upped the fuel flow to compensate
