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ROFCIBC, know any KC-97 guys back in your day?
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Lot's of them. I started flying KC135s in 1967 and there were still KC97s being used. In the mid 70s the Guard units that had them converted to KC135s.
My first aircraft commander, a guy by the name of Joe Tucker had just converted from KC97s to 135s in 1968. Last week I ran into the first crew navigator, who I hadn't seen since 1968. He too had just converted from the KC97. Had a pilot training buddy, Jim McGuirk who flew them in the Ohio ANG out of Lockbourne AFB, later Rickenbacker in Columbus.
Barksdale still had a KC97 they used to haul folks around. Had the boom removed. I remember flying up to Little Rock AFB for my first recurrent altitude chamber on it back in 1969.
You mentioned the water system of the KC135.
The whole idea was that the extra thrust of the water augmentation was going to let you increase your gross weight to a point where even if you lost and engine at V1, you could takeoff, and accelerate to get the flaps up before the water quit. And I mean they had this planned to the second! BOOM! engine goes at V1, rotate, liftoff, gear up, climb to acceleration altitude, (might be as low as 180 feet AGL), struggle to flap retract speed, retract them, and just as they reach zero degrees, POW! the water runs out.
Now think about this. Here you are, on three engines, maybe 250,000 pounds, 180 feet above the ground, at flaps up speed, maybe 20 knots above V2 speed! Is aviation great or what? But remember this was a theoretical, designed by some slide rule (back then) dork (now a computer geek) who never flew and was sitting at a desk with a ground speed of zero! Yeah, uh huh!
When they first built them it was a left/right system. That is there were two electric boost pumps (the mother of all boost pumps!) in the water tank, one forward, one aft. Forward one fed the left side engines, aft one the right side. As you got down to the end of the water (2 minutes, 5280 pounds) the acceleration made the remaining water go to the back of the tank, hence the front pump ran dry first and the water ran out on the left engines first.
Made the airplane yaw left. Just about the time you made a correction, WHAM! the other side ran out. Called the “Eyaaahhhhaaaaa!” maneuver! Sometime in the 70s they redid the plumbing so the two electric boost pumps were and inboard/outboard system.
Funny thing about those electric pumps. They used nearly all the available electrical power the three engine driven generators could make. If you lost a generator, you lost water! Bummer. Also you couldn't turn on the air conditioning pack (only had one) until after the water ran out. Made for some miserably hot takeoffs!
When you advanced the throttles each engine had a air driven (bleed air) pump that really moved the water. Face it 670 gallons in two minutes is MOVING water. About 80% was tossed into the front of the engine and the remaining 20% went into the burner cans. Whole idea was to make the air more dense (wet air is that way) hence you could stuff more fuel in and get more power. The cooling effect of the water was a secondary, albeit minor part.
All in all it was a very reliable system. Never lost water on a single engine in 14 years of flying the water wagon. Once the water "kicked in" it was a good system.
After takeoff you hit a drain valve to completely empty the tank so it wouldn't freeze at altitude. This created a “gotcha” that more than one poor copilot got bit with. As you rolled out for takeoff the copilot started the pumps, using a switch on a panel just in front of his left knee. Watched the two boost pump lights go out, then checked the generator loads. The “gotcha” was that the dump switch was about four inches to the right of the “start” switch. Once the dump valve opened, it could only be closed on the ground through and external panel below the tank. I’ve seen a few takeoffs where the plane was dumping water on the takeoff roll! You still had water for the engines, just not the full two minutes as you were dumping some of it as you took off! The decision to press or abort all depended on just how heavy you were. If you were maxed out…you aborted as the loss of the full two minutes of water, in the event of an engine failure was bad juju! Really BAD juju! If you were not that heavy, or heading of on a weekend cross country to sunny Florida, you pressed on as the copilot was buying the beers when you got there!
When it got down to 40F you had to heat the water. Had major league electric water heaters in the tank, that used external power or the on board APU to work. Had to get it up to 100F. If the temp got down to 20F or less, you dumped water as the engines produced the same thrust as when you used water.
I still have a patch that says,
"KC135...Built When Man Thought He Could Burn Water!"
And another,
“KC135…Turns Fuel and Water Into Noise and Smoke!”
Interesting side light. Although it looked dirty and nasty a water takeoff actually left less particulate matter in the air. Due to the higher density of the smoke the particulate matter fell out of the air much more than the smoke of a "dry" takeoff. Didn't help the poor saps under the takeoff path much, but did give the endangered species birds better air to breathe!
So much for Water Wagon 101! Last time you'll ever ask about that!
