By Lionel Alford
I had an opportunity to fly a T-6A as part of flight testing. The T-6 makes its own oxygen through an OBOGS. An OBOGS uses compressed atmosphere from the engine to separate oxygen from nitrogen and other elements in the atmosphere. The oxygen comes out about 95% pure and goes to the pilots for breathing. I like OBOGS systems because they provide the oxygen at some slight positive pressure. This makes breathing easier with an oxygen mask. In most fighter and trainer type military aircraft, you use an oxygen mask all the time connected to your helmet.
The testing we were accomplishing was a certification of a new OBOGS for the T-6 aircraft. I was lucky to be able to get a flight. The problem was part of the flight was to stress the pilots and the OBOGS. The way we planned to do this was to hold 5 to 6 Gs continuously for at least 30 seconds. That may not sound like much time, but when you are at 5 to 6 times your body weight for 30 seconds, that’s like an eternity. I wasn’t sure it could be done, or how difficult it would be.
We wore fast pants (a G suit) for the test. When you are used to pulling Gs, 4 Gs isn’t anything. We had been accomplishing stall testing at 4 Gs and some of those points could last as long as 1 minute. When we go above 4 Gs for test, I like to have my crews wear fast pants for safety. In military training, you usually wear your speed jeans (fast pants, G suit) for every flight.
Well, we set up in the Military Operating Area (MOA) for our points–all those including the high G points. Part of the testing was to the maximum altitude of the aircraft at 31,000 feet and aerobatics. We planned to do the high G point as the next to last because we had a low level point to get back to base. I started the aircraft in a dive to 285 KIAS and pulled on the Gs in a spiraling descent, and then I held about 5.7 Gs while the guy in the back timed the run. We made between 5 and 6 Gs for 37 seconds and we still had plenty of altitude and airspeed left over. What a great aircraft. I don’t recommend trying to hold 5 to 6 Gs for an extended period, but the aircraft can do it easily–and the OBOGS can keep up to the pilot’s need for oxygen no matter what you might try to do with the aircraft.