Here is what he sent on the 747 with the JT9D engines....
[FONT=Verdana,Helvetica,Arial][SIZE=-1][FONT=ARIAL,]This very complicated water injection system could be used with the following JT9D engines on the 747 :
JT9D-3A, Dry T/O rating 43.500 lbs. Wet rating 45.000 lbs.
JT9D-7 and -7H, Dry T/O rating 45.500 lbs. Wet rating 47.000 lbs.
JT9D-7A and 7AH, Dry T/O rating 46.150 lbs. Wet rating 47.670 lbs.
JT9D-7F, Dry T/O rating 46.750 lbs. Wet rating 48.650 lbs.
On the DC10-40 :
JT9D-20, Dry T/O rating 44.500 lbs. Wet rating 47.500 lbs.
Water alone is specified and should contain no more than 10 (ppm) parts per million impurities. Use of water is limited to takeoff operation up to an altitude of 8,000 feet for D-3A, and 10,000 feet for D-7, -7H, -7A, -7AH, -7F and -20, at the minimum ambient temperatures of 32oF. Take off using both water injection and dry takeoff power is
limited to a maximum period of 5 minutes including operation with water injection for not more than 2 1/2 minutes
(JT9D-3A, -7, -7H, -7A, -7AH, -7F) and 5 minutes (JT9D-20).
On the 747-100/200 two water tanks were each built in the wing roots (left and right) and extra piping was installed for transportation of the water to the four engines (one tank for 2 engines at the same wing.) Also piping for waterfilling and draining of residual water after T/O was installed. Four high capacity water pumps were feeding the engines with water.
Each engine had an adapted fuelcontrol to cater for extra fuel when the system was activated.
System operation (747) :
- When a wet rating was needed min. 2300 kgs of water was uplifted. (standpipe level was 2450 kgs)
- During Taxi-out, just before entering the runway, the system was switched on (F/E panel), the four water pumps were momentarily giving a flow indication (four green lights), check all water low press lights out. Most frequent failure at this moment : water pumps start to operate but the water shut off vlv is still (partly) open. This is called a "steam out" or "piss out" . The relevant engine (still at idle) gets the full water flow and stops operating and has to be restarted, after switching off the waterinjection system.
When entering the runway the system is now armed.
After advancing the powerlevers at approx. 1.25 EPR the system comes in, four green water flow lights illum (pilots annunciator panel), the watershut off valves are open. Carefull monitoring of the EGT indication is crucial (one engine can suddenly revert to no water (pump failure), but still with the high (wet) fuelsetting.
After 2.30 minutesa or just before water run out (indicators on F/E panel), the system is switched off, 2.30 minutes dry rating is still available when needed.
Switching off was the most tricky part of the operation, because of the low usage of the system frequently failures occured.
The most dangerous was that the waterpumps stopped and shut off vlv's closed but one engine fuelcontrol stayed at the wet fuel rating. Before you could blinck an eye the EGT exceeded the T/O limits and an expensive boroscope check or even an engine change was required.[/FONT][/SIZE][/FONT]
Thats all I got from him on that subject. He did note that liability issues limit what the commercial carriers will do and that their flight envelopes are more limited than those of the military. None of the current carriers are using water injection to his knowledge. Looking at the figures of thrust posted for the JT9D I can see why they wouldn't want to use it. The complexity and extra weight isn't offset by the meager added thrust. In the case of turbofan engines it doesn't make as much sense.
Frank