I Flew the U-2
One of Lockheed’s former chief test pilots for high altitude reconnaissance describes the joys and terrors of the U-2.
- By Linda Shiner
- Air & Space magazine, March 2012
Marine Corps Reserve Major General Kenneth Weir (ret.) flew U-2s as a Lockheed test pilot between 1966 and 1993. A Marine aviator and graduate of the U.S. Naval Test Pilot School and the U.S. Air Force Aerospace Research Pilot School, Weir accumulated more than 19,500 hours in more than 200 types and models of aircraft.
Air & Space: Once an airplane has been flying in service, as the U-2 had been when you started at Lockheed in 1966, what is the test pilot’s job at that point?
Ken Weir: The airplane’s flight envelope had been expanded by the first pilots who flew the it. After it goes operational, most of the work done by the test pilots is developing electronic systems for the airplane—the sensors, the photographic equipment, the ELINT [Electronic Signals Intelligence] systems, modifications to the autopilots, flight control systems, and things of that sort.
The TR-1 was a production re-start of the U-2R with the addition of “Super Pods” on the wings to accommodate extensive new airborne sensor systems. The Super Pods caused unforeseen structural dynamics at high Mach numbers at very high altitudes that had to be resolved. The U-2S airplane was the re-engining of all of the big U-2s with a new General Electric F118 turbofan engine. The initial flights were flown without any airstart capability until the incorporation of a hydrazine starter.
We verified the high-altitude performance of cameras that were to be used in satellites for reconnaissance. The manufacturer would develop the cameras, then we’d carry them as high as we could get them and check them out before they went into the satellite programs. Initially, the pilots weren’t allowed to look at the pictures; they kept that compartmentalized, and we were shown only some of the tracker camera film. That was mostly unclassified. The pictures from the higher resolution cameras, they kept covert. We didn’t get to enjoy what we called “our take.”
So the pilots didn’t get to see the pictures they were taking.
I’ve seen more of those pictures now in history books than I saw in the program. We did have a viewsight: There was a periscope that poked out of the bottom of the airplane, and you could get a look at where you were, so you could kind of imagine what the cameras or infrared or side-looking radars were getting.
What was it like flying missions that you couldn’t tell anybody about?
Everybody was guessing, and you couldn’t tell them, so you just let em keep on guessing. And that made it more intriguing.
You flew both the earlier, shorter-winged U-2 and the more modern variant with the very long, 105-foot wingspan.
I flew the little one and the big one. They modified the A model to put the bigger engine in it, and that was the C, the hot rod. That was a really fun airplane to fly. The Cs had a higher rate of climb; their thrust-to-weight ratio was a lot better.
They were a lot dicier airplane to fly because of the airfoil. In 1968, they built the big airplanes, and they had a much larger wing area and a different airfoil. They were a lot easier to handle at altitude; they had roll spoilers to go along with lift spoilers.
The G model was also a small airplane. That was the U-2C that was modified for carrier operations. They put a little different camber on the leading edge of the wing, and put lift spoilers on it, and a tailhook of course. And with the big engine—the J-75 non afterburning engine—it would just leap up. It would rocket to altitude. It was a fun airplane to fly also.
What was the challenge of flying the smaller airplane?
When the littler airplane got up to altitude, the margin between the climb speed and the critical Mach number and stall became very, very minor, and we were looking at plus or minus two-and-a-half knots at one particular point in the climb between the climb schedule and critical Mach and stall speed so that’s very very small. When we got the bigger airplanes, we got up to plus or minus seven-and-a-half knots of margin.
But we were saddled with trying to maintain that climb schedule for long, long periods of time, so we would never go to altitude without an autopilot. You engaged the autopilot as you were climbing out, and then you got into the climb-Mach schedule, and you engaged “Mach hold,”; you had a small Mach trim wheel so you could tweak it just a little—more Mach or less Mach. And it maintained that climb schedule. It was almost impossible to “hand-fly” it—disengage the autopilot and try and fly it up through there with the yoke.
When Francis Gary Powers (we called him “Frank”) got shot down, he was having trouble with the autopilot, and he had to descend to a lower altitude to hand fly it, and that’s when the surface-to-air missiles were able to get him.
How did it help to descend?
At lower altitudes, the airplane was more stable and there was more margin between the stall buffet and critical Mach number buffet. During the cruise phase of the mission, as you burned off fuel and the aircraft got lighter, you had a little more margin even as it gained more altitude. The envelope expanded as you got higher and higher and lighter and lighter. Then you got more margin between the Mach buffet and stall buffet. If you encountered buffet, the first thing you did was go faster. You’d assume it was stall buffet, and you wanted to go faster because if you guessed wrong and slowed down, then it would stall and quit flying altogether. It would flip over on its back, and that’s how we lost a lot of the airplanes. It stalled at altitude, it would head straight down, and the tail would snap off.
Is that why the change was made to the longer wing?