I know nothing of military operations but, this tweaks my interest. Why does the military need approaches of this sort? -4000fpm in a KC135 sounds like a hell of a good time! :nana2:
They were called 'high altitude penetrations' when I was flying them. You would come in and stay high until you wanted to come down and land. I guess the idea was to stay above small arms fire, etc in hostile areas and then come down quickly before the bad guys had a chance at you. I would say it was also for fuel savings but we flew the patterns then with the gear down and flaps 30 so we didn't wear out the systems (I'm not making this stuff up). Needless to say, we burned a LOT of fuel and a rough rule of thumb was 10% of your gross per hour so at 160,000lbs, we vaporized about 16,000lbs per hour.
My Ops officer took approaches and turned them into math problems and when he flew them, it looked like the airplane was programmed. This was more than 30yrs ago so we didn't have the ability to lock the autopilot into an FMS (??? flight directors were NEW)
John was quick at figuring his numbers. For example, he would use his mach number (for example 0.60) to calculate his time to travel the distance (about 6 miles per minute). Distance divided by time would give him his required VSI. And if for instance, he needed 4000fpm, he would multiply his mach (mach number times 100 equals VSI with each degree of pitch.. ie, 0.60 mach for each degree of pitch change the VSI is 600fpm). 4000fpm in this case requires the nose to lower about 6 or 7 degrees.
It takes longer to type this stuff out than it did for John to run his numbers. He would ask the nav for drift before his turn and either add it or subtract it from the bank angle for a standard rate turn and again, like I said, it all looked like it was an FMS approach before we had FMS approaches.
Add to the fact the tanker can come down like a rock. It was not unusual to drop the gear, pull the boards up to a full 60deg and at idle thrust, peg the VSI at 6000fpm. In emergency descents, we did the math and it was not unusual to have descent rates at around 10,000fpm.
None of the stuff I later flew (737, 757, 767, Airbus) had the drag capabilities of the old tanker. It is going to be hard to replace.