Continued from the May 2022 issue…
You Can Feel Your Innards Move
After I slow to subsonic, the next check is the over-G limit function of the flight control computer. It should allow you to pull as hard as you want, as quickly as you want, and not let the jet go to more than 9 Gs plus-or-minus point four Gs. As soon as you drop to subsonic, you roll to 80 degrees of bank and quickly pull; about 25 pounds of pressure on the stick. The G-suit squeezes the crap out of you, and you push back to stay conscious. A lot of people have said to me over the years that it must be fun to pull 9 Gs. Nope, 9 Gs hurts. You can feel your innards move.
If you know anything about GLOC (G-loss of consciousness, pronounced G-lock), you know that the “onset” rate is a major factor affecting whether you black out or not. That means how quickly you go from 1 G to 9 Gs. The nerve cluster in your upper neck that makes you wake up from a dream when you think you’re falling, or makes you gasp when you feel zero-G unexpectedly, is the same one that tells your heart to beat faster when you pull Gs. The function is to increase your blood pressure allowing you to stay conscious and keep most of your vision.
This cluster, however, isn’t “designed” to react to an instant 9 Gs; there’s a delay. Thus, the G-suit and the need for your physical reaction in preparation for the Gs. This test requires an instant onset rate to verify the computer can catch the impending over-G. Not good for the human body. We lost a handful of F-16 guys because they blacked out at some point in a mission – usually due to high onset rates and ran into the rocks. The good news is you only have to hold 9 Gs for a few seconds during an FCF.
Doing the Test Naked
At the end of the max-G check, you’ve used up a bunch of energy and slowed to less than 300 KIAS. This sets you up for the next gut-check. The flight control computer has another pilot-proof feature; it shouldn’t let you stall – ever. If the F-16 is stalled, it tends to go into a “deep stall” or “deep spin.” Picture a falling leaf with the nose pitching up, then down, then up, etc. Usually unrecoverable.
The stall is so potentially dangerous they put a special switch in the cockpit called “manual pitch override,” or MPO. Pushing this switch gives you extra stabalator (stabalateron!) travel to help increase the amplitude of the pitching moment in the stall. Hopefully, the extra amplitude in the down direction will be great enough to “fall” out the bottom of the cycle and accelerate to flying speed. This part of the flight envelope was tested at Edwards in an F-16 with a spin chute attached. Today I’ll be doing the test naked (no spin chute).
When you reach the point where the flight control computer steps in to “help,” you’re supposed to get a tone in your helmet followed by something like a stick-pusher in a civilian jet. The stick in the F-16 is unaffected, but the stabalateron moves. You fly the test by pulling the jet into a 60-degree climb at low power, then watch what happens. If you maintain a constant 60-degree angle of climb using the flight path marker in the HUD, the AOA (angle of attack) increases as the speed bleeds off. As an FCF pilot, you have to let the jet go all the way to the edge of the envelope just in case that’s the point at which the computer is set. If it exceeds the critical AOA, it not only fails the FCF but you’re very close to a deep stall as well.
Falling Through 13,000 Feet
My enthusiasm for this FCF drops to zero when my AOA reaches the point where I should have heard the tone. An instant later, the nose drops, and for a split second, I think the computer has pushed it over and just failed to give me the tone. Not this time. The nose pitches back up, un-commanded. I’m in a deep stall. This test maneuver is started at 15,000 feet for air data computer testing parameters. The minimum altitude for ejection when the airplane is uncontrolled is 10,000 feet. I’m out of control and falling through 13,000 feet. The emergency procedure for out-of-control has only four steps.
First, release the controls. In the F-16, that’s pretty simple: stop applying pressure in any direction to the stick. Step two is MPO switch: override and hold. Third, stick: cycle in phase. That means try to increase the amplitude of the pitch motion in both the up and down directions. And finally: eject at minimum uncontrolled altitude. When the nose first pitched down, I had already released control pressure, and now I’m holding the MPO switch. At the second pitch-down, I glance at the altimeter to decide if I should push the stick forward or pull the ejection handle. I push forward on the stick. I’m comfortable with the capabilities of the ACES II ejection system. I’ll ride it to 10,000 feet. The nose hesitates on the down cycle, and just at the point I expect it to pitch back up, it falls through to straight down and I begin to accelerate. Almost as quickly as I entered the stall, I was out of it. Yeah, right – in dog years. It seemed like 10 minutes of falling. As the airspeed hits 200 KIAS, I start pulling back and bottom out at about 10,001 feet.
I finish up the rest of the FCF checklist and take the jet back to base with a failed AOA limiter to be entered in the maintenance log. I’ve used up 6,100 pounds of fuel in 42 minutes and another 0.7 hours goes into my logbook. Most of my F-16 time was accumulated 0.5 to 1.5 at a time. Almost all of it was very intense, fun flying – FCFs, dropping bombs and fighting against jets from the Fighter Weapon School (Top Gun) or Aggressor squadron.
Fighter time doesn’t include ground time either, only flight time. It’s not surprising that when employers look at flying time, fighter time means something different. Frank Lloyd Wright once said, “Early in life, I had to choose between honest arrogance and hypocritical humility.” The F-16 can make you arrogant – honest.
Not Vaccinated
It’s normal to finish a high-G flight wet with sweat, which I am. As I get undressed, I see the G-measles on the inside of my arms. Not something most people are vaccinated for. You get them from pulling Gs. The capillaries on the inside of your forearms and your butt a couple of inches below the beltline show them the most because that’s where the blood pools, more capillaries are close to the surface, and the blood pressure seems to be the highest. They show up as hundreds of small red dots (petechiae) – like pin pricks. You can’t feel them, but everyone that pulls Gs gets them.
General Yeager once said to me, “Maybe you’ll get higher than me.” He was talking about the altitude records he set and my just-beginning Air Force career. By the time I left Edwards Air Force base for OTS, I was convinced I wanted to be a Test Pilot. Each time I did an FCF takeoff, I thought of his words to me. I never made it to Test Pilot School and I never set any altitude records, but as the General was quoted in The Right Stuff as having said, “I had a ball!” John Gillespie Magee, Jr. said, as pilots, you and I “have done a hundred things” others have not dreamed of. Remember to look out the window while you’re flying and appreciate those hundred things.
Isn’t it magical where making a paper airplane can lead? Don’t be afraid to make paper airplanes, and don’t be afraid to throw them in class.
