Monday, January 25, 2010

Chapter 26: Electric Jet

The versatility of the F-16 is shown by this F-16D of the Edwards Test fleet. The mission flown by the author was in an F-16B with a clean aircraft carrying only Sidewinders on the wingtips. 87-0392 has two external tanks, HARM, AMRAAM and Sidewinder missiles, and a targeting pod on the inlet. Lockheed Martin

At 40,000 feet the sky was impossibly blue as our F-16B headed south over the Mojave Desert. The view from under the bubble canopy was awesome. We were arrowing across the sky, a snow-white condensation trail marking our track across the heavens. Off to our right the snow-capped Sierra Nevada marked the backbone of California. In front lay the expanse of the Mojave Desert, backed by the San Gabriel mountains. Nearer to hand, dotted about the desert, lay the dry lakebeds used as emergency landing sites back in the rocket flying days of the X-research craft.

Close below under our nose were Cuddeback and Harper Dry Lakes. Further away lay the expanses of Rosamond and Rogers Dry Lakes, the latter bordered by the cluster of tiny dots of the huge hangars at Edwards AFB, where we had taken off less than an hour previously.

In the front seat of the diminutive jet fighter was John Fergione, Chief of Flight Operations at Edwards AFB for Lockheed Martin, builders of the F-16. Now, with the throttle eased forward to the Military Power detent, we were accelerating. It was still quiet in the cockpit and uncannily smooth. Cabin altitude was 15,000 feet and the doll’s eye of my oxygen flow indicator blinked rhythmically in time with my breathing. The ACES II ejection seat in the F-16 was reclined thirty degrees. Primarily designed that way to increase the g-tolerance of the pilot, the result was a very relaxing posture, unlike more upright seats in other jets I had flown.

At Mach .86 there was a barely perceptible shudder as the airflow started to go supersonic over our wings. We watched our Machmeters creep upwards. At Mach .98 my Machmeter needle hesitated as the airflow piling up in front of the aircraft increased the drag. Fergione eased the nose down a fraction. We continued to watch the instruments intently. At 39,000 feet and Mach .95 the altimeter needle quivered, swung crazily and settled down again as the shockwave eased back over the static ports. Simultaneously the Machmeter swung up to Mach 1.05. It was an event marked only by its lack of drama.

We were supersonic, still in dry power, and the F-16 was not even breathing hard. If the throttle was fully forward, at the full afterburner position, the F-16 could zip out to better than Mach 2.0 but naturally would gulp fuel at a horrendous rate in the process of doing so.

I could not help thinking that it was only a few decades ago that Chuck Yeager had gone supersonic for the first time in the Bell X-1 in this very same patch of sky. In those days it needed a B-29 mother ship, a gaggle of chase planes, rocket power and a big step into the unknown to accomplish supersonic flight. We had just done it in a routine manner.

We continued descending, accelerating to Mach 1.2 as we neared the lower edge of our reserved airspace. Fergione throttled back into subsonic flight for me to fly a few maneuvers. By now our double boom from the shockwaves was heading off towards Edwards to rattle the windows and the hangar doors, just as similar sonic booms had cracked across the field periodically before we took off.

Another assignment had sent me on this visit to the F-16 Combined Test Force at Edwards. Operated, as the title implied, by a mix of USAF and contractor personnel, the CTF had given me an opportunity to fly on a mission which would take us through the low-level route north of Edwards before climbing up to the supersonic corridor for a brief look at supersonic flight. Then I would be given an opportunity to look at the handling of the F-16. This was the newest fighter operated by the US Air Force. It was a rare privilege to fly this fighter.

After I was fitted out with flight gear in the flight equipment section, (with the technician taking great care in lacing and tweaking the g-suit to fit my legs and lower body like the proverbial glove, and selecting and testing my oxygen mask and helmet) we had walked out to our gray-painted F-16B parked on the bustling flightline outside the CTF. The ramp was crowded with single-and two-seat F-16s. Some F-16s were tasked with testing of LANTIRN pods on low-level night missions. Another F-16, spin chute cantilevered out on a tubular framework behind the tail, was busy with high angle-of-attack investigations. Others were scheduled for performance testing with the new F-110 engine.

Our callsign today would be ZOOM 76. While John Fergione pre-flighted the ship I climbed the ladder and slid into the rear cockpit. Pushing my feet forward in the tunnels to the rudder pedals, I connected up the sidestraps, lap strap and chest strap linking me to the ACES II ejection seat. Then I carefully checked that the vitally important g-suit was correctly plugged in. As I donned my helmet and mask, Fergione climbed into the front seat. Leaning forward I adjusted my rudder pedals and got ready for business.

The canopy, a single-piece made of a three-quarter inch thick monolithic polycarbonate transparency, for bird strike resistance, sighed down and locked. On the F-16 the conventional windscreen and canopy were combined, eliminating the usual canopy bow which obstructed the forward view on earlier fighters. The resulting visibility was superb. There was a price to pay. Fergione had briefed that if we had to eject, I would go first, and my ejection would start a sequence which would eject the canopy, myself, then Fergione, in that order. I resolved not to eject unless things really looked serious.
The canopy rails were low down to either side, further improving the view. The hefty throttle, with multiple switches, was on the left hand cockpit wall, while the sidestick was on the right hand wall.

Our Jet Fuel Starter (JFS) whistled into life. At twenty-five percent rpm the engine lit up with a rumble, with the generator coming on line a few seconds later. The Inertial Navigation System (INS) was aligning as we checked our caution lights around both cockpits. The INS held up to ten waypoints, gave our present position, presented steering information on the Head Up Display (HUD) and also calculated the wind speed and direction. It was certainly better than following railroad tracks.

The F-16 was an unstable fly-by-wire aircraft, known as the Electric Jet to its pilots. Consequently an exhaustive flight controls automatic checkout was necessary before we could fly. We were still waiting for the INS to align when over the radio Edwards Tower cleared ZOOM 76 for the AMBER route for the low-level portion of our mission.

In the rear cockpit I had in addition to the normal flight instruments and CRT incorporating a moving map display, a HUD repeater which could be switched to show the radar display. This was currently showing a green-tinted video picture of the outside world, namely the hangar and the groundcrew walking on the ramp. I fiddled with the controls of this display. By the time I had adjusted the brightness to my liking, the INS platform was aligned and we were ready to go.

We taxied out and I checked my g-suit by pushing a button at the rear of the left hand console. The suit inflated, putting my legs and abdomen in a vice-like grip until I released the button. There was no doubt that the suit was working. With the tremendous agility of this fighter, F-16 pilots could lose consciousness if the g-suit became disconnected during hard maneuvers and the g-suit was an essential part of keeping the pilot away from the deadly occurrence of g-LOC (g-Induced loss of consciousness.)

Our groundcrew had by now piled into a van and had followed us out to the head of the runway, where they scurried about under the craft, checking the security of panels and giving us a final visual check. With a final thumbs up from the crew chief, we contacted Edwards Tower and ZOOM 76 was cleared onto the runway for takeoff. We armed our seats. I reminded myself of the numbers that Fergione had quoted at the briefing. We were loaded with just over 5,000lbs of fuel. This put our takeoff weight at around 23,000lb. Our F-100 engine provided 25,000lbs of thrust, enough to launch us vertically. This promised to be a spectacular takeoff.

Brakes could not hold the F-16 above eighty per cent rpm because the anti-skid system would automatically release. So Fergione set the throttle to eighty per cent and as the engine wound up he released the brakes. We started accelerating down the runway and as he advanced the throttle to military power, the rpm swung up to 100 per cent.
“We have five stages of burner. You can feel them all,” Fergione said conversationally, advancing the throttle smoothly into the afterburner range. “The last one is the biggest.”
As we accelerated, my helmet was forced back against the headrest and there was a jolt as each of the five stages of afterburner lit-up in sequence:
There was no mistaking that last one.

With all that thrust we were by now accelerating like an arrow from a bow. Before we had reached the first thousand-foot marker board at the side of the runway we were rotating at 120 knots, with the wheels off the ground at 135 knots. The gear retracted and by the end of the 15,000 ft runway the airspeed was climbing through 450 knots. It was a breathtaking start to the flight.

We came out of afterburner and climbed towards twenty thousand feet at 450 knots. I took control of the aircraft and started getting used to the sidestick control of the F-16. Some time earlier I had flown the variable-stability Learjet rigged to simulate an early F-16 flight control system. That system had been actuated by force sensors alone. With no feedback from any motion of the stick, I had found it difficult to fly precisely. Other pilots had reported the same experience. But now, in the real F-16 the sidestick on the right hand console gave me about a quarter of an inch of movement, although primarily still a force-sensing device. It was surprisingly natural. An armrest supported my right forearm. Use of a sidestick certainly freed up a lot of panel space in front of the pilot. The cockpit was small but adequate, almost like the Grob sailplane, although price and performance of this aircraft were multiplied many times over that of the Grob.

I cautiously tried out gentle turns to left and right, getting used to the sensitive flight controls, then leveled off at twenty thousand feet as we headed north-west over Mojave and Tehachapi, into the mountains. Now it was time to descend, and Fergione took control and we spiraled down in a 4g turn, my g-suit squeezing, to enter the south end of the Amber low level route. At 420 knots we headed north, our clear visors down on our helmets to guard against possible bird strikes. Initially we headed north over the foothills of the Sierra Nevada which rose to 8,000 feet ahead of us.

The ride was smooth and the ground streamed past below. Lake Isabella slid past to our right. On the HUD Repeater I was intently watching my display. A pitch ladder occupied center screen, with speed presented on the left hand side. Our heading of 350 degrees was lower on the display with altitude indicated on the right. A circular symbol on the HUD showed the position of our next waypoint. Most importantly, at the moment, the velocity vector symbol, showing our projected flight path, was perched just over the next saw-toothed ridge.

As we flew north the wooded ridges in turn flashed past just underneath us. We reached our first waypoint, a cluster of radio towers on a ridge. The waypoint symbol on the display slid off to the right, pointing to the next waypoint. Our right wing went down and we banked hard to the right until the symbol centered again in the HUD. The ride was still smooth and we were now up to 440 knots. As we headed north the ground was rising. Signs of civilization were restricted to the occasional dirt road. Patches of snow were visible beneath the trees. The ridges, running east to west , became steeper and more and more spectacular as we hurdled over each one.

Waypoint 2 was a Forestry Service observation post. I looked down to see a lonely cabin located on a beetling crag, reached by a tortuous path etched across the face of the bluff.
Looking forward again I became aware of the snow-covered bulk of Mount Whitney off to our left. The mountains were rugged up here in the Sierras. We were heading north-east when turbulence started to buffet the plane. It was a washboard type of roughness, not the usual isolated jolts of convective heating. It felt as if the wind was rising. We climbed a few hundred feet but found no relief from the hard-edged jolting.

Between two ridges off to our right, Owens Lake slid into view. Stained red and white by the minerals in the water, it had the look of a surrealistic painting. The turbulence was getting worse and I was alternately jolted hard against my straps, and then back into the seat. It was difficult to breathe under these conditions.

Our flight planned path now led us down across the Owens Valley itself, with the sheer wall of mountains looming off our left wingtip. We could see that the weather was deteriorating to the north where a series of lenticular clouds barred the valley ahead of us. This celestial staircase climbed to maybe thirty thousand feet today and was the fabled Sierra Wave which was so useful for sailplanes to reach those extreme altitudes. The rotor system associated with the mountain lee waves was the cause of the turbulence that was battering us today. In between jolts I could not help thinking ” If only I was in a sailplane today…” But of course this day was reserved for more serious business.

We overflew our next waypoint, then banked hard right, now heading east across the valley towards the opposite sheer mountain wall. As a last veil of cloud drifted back above us the turbulence was suddenly switched off. Still heading for the wall of rock looming in front, Fergione pulled back on the stick, the nose came up and the velocity vector on my display rose to hover over the mountain ridge. Climbing more than a mile in a few seconds, we crested the ridge at ten thousand feet, banked right and flashed down the barren eastern slopes into Saline Valley.
As the F-16 dropped two miles in a few seconds my ears started complaining until I held my nose through the oxygen mask, blew hard and equalized the pressure. Leveling just over the dry lakebed we headed south with our shadow speeding just off to my left across the scrub-covered plain. Glaring white patches of dry lakebed flashed past and we climbed slightly to avoid a jagged outcrop of rock barring our path. Then we pitched down, and I floated against my straps momentarily, before we bottomed out, now hugging the lakebed and heading for our target.
It was an exhilarating ride. Operationally, this low altitude and high speed minimized exposure to enemy defenses, but the unremitting concentration of even keeping track of our position was very exhausting.

At the southern end of the valley this lunar landscape ended in another wall of mountains. We bored on until the rock wall was high above us, then Fergione smoothly pulled the nose up and we easily outclimbed the rising ground as the jagged ridges rose beneath us. Seconds later, our trajectory peaking at 7,000 feet, we flashed across the desolate ridge and plunged down into Panamint Valley.

I recognized this place, This is where I had flown with the Wild Weasels. Yes, there was the solitary road snaking across the awesome immensity of the dry plain, coming from Death Valley across the mountains to the East. Moments after we flashed across the road a glaring white lakebed blurred beneath our nose. It was incongruously quiet in the cockpit. Then a dirt road flashed diagonally beneath us. I caught a glimpse of a white RV trailing a plume of dust behind him. It was too bad. At this speed we were barely a second behind our noise. The driver might with luck have seen us in his rear-view mirror, giving him a split-second warning, before the thunderclap of sound hit him…

Three miles to the target. I could see it coming up on the HUD, under the target cross. There…in a split second, my mind recorded images…a cluster of buildings…a radar dish revolving…parked cars around the radar station…then we were fleeing across the valley floor, trailing our banner of sound.

At the southern end of Panamint Valley, we again were heading straight for the mountains, but this time Fergione pulled the nose of the F-16 up and kept it pointing towards the vertical. The F-16 stood on its tail and kept climbing out of the low-level corridor, aiming for 40,000 feet and our supersonic run.

Once our supersonic run was complete, remembering that the F-16 was a fighter after all, I took control of the jet while we searched for targets. Reaching forward I switched my display from HUD to RADAR mode. Our radar was sensitive enough to pick up trucks on the Antelope Valley freeway. However as we looked for aircraft targets our respective screens remained blank for a moment. Then our ATC controller warned us of two aircraft heading for us. We searched with the radar, varying the elevation of the beam using a throttle-mounted switch.

Suddenly, there they were, two targets coming towards us, head-on but lower than our F-16. The computer-generated targets had symbols showing aspect angle and target speed. Moments later we had a visual on them, a pair of white F-4 Phantoms from the test fleet at Edwards, maneuvering in their own block of airspace beneath us. Our Sidewinder missiles would easily have destroyed these bogies, or we could have gone after them with our built-in 20mm cannon in our left wing root. We pulled round after them. In the sun and ten thousand feet higher than the Phantoms we were in a perfect position for a bounce, but we reluctantly had to let them go on their way.

Decelerating and letting down to 15,000 feet enabled us to look at the low-speed handling of the F-16. Throttled back, I used the throttle-mounted speedbrake switch and we slowed to two hundred knots. I cleaned up and we continued slowing initially to 180 knots. I was watching intently the altitude and the angle of attack. By 130 knots we were at twenty units angle of attack. At 100 knots the nose was pointing skywards with much of the lift coming from the leading edge extensions either side of the cockpit. At this unusual flight condition we were definitely in the hands of the flight computer, another reason for the soubriquet of “Electric Jet” Above fifteen units of AoA the computer limited our roll rate. No matter how hard I pulled back on the side-stick, the F-16 was limited to a maximum of twenty-five AoA. Pushing the rudder pedals at this flight condition had no effect as the rudder was automatically phased out at high AoA to prevent the F-16 departing in yaw and entering a spin. Fergione then demonstrated the roll control at low speed by accelerating to 150 knots, then rolling the F-16 through 360 degrees with no problems. I was impressed.

Then he handed control of the aircraft back to me. We accelerated to a more normal fighting speed of 350 knots. I started with an aileron roll to the left. Light pressure on the sidestick got us rolling smoothly to the left. I reversed the pressure and the roll stopped after one complete revolution. Then I repeated the roll to the right. My first attempt at rolling using a sidestick gave a noticeable difference in feel between left and right rolls, like the difference between forehand and backhand in tennis. It felt very unnatural to me at first. The F-16 flight control system was set up for full control deflection in roll using only a 17lb force. With only wrist action available, that was a reasonable figure.

Progressing to four and eight-point rolls, I was now getting used to the sidestick, although the harmony between the light roll forces and heavier pitch forces took a little getting used to.
Next came a loop, where I pulled 4g in a huge arc, topping out at 25,000 feet. This was sheer fun and the F-16 was not even working hard. Hard turns were similarly easy, giving tremendous agility and the ability to reverse direction in an instant. My g-suit was constantly inflating and deflating. However I slackened off on my pull when I saw Fergione’s helmet start to slide down behind his headrest, warning me that the g was getting too high. I could easily have pulled to the 9g limit with a 25 lb pull and the F-16 would not have complained.

We were now heading eastbound and were down to our BINGO fuel of 1,200lbs, so to reverse direction I pulled up into an Immelmann turn, pulling an easy 4.5g, until the horizon floated back down to the nose, rolling out from inverted on a westerly heading for Edwards.
“ZOOM 76. Continue your descent. We have a B-1B climbing out towards you. One o’clock at three miles” said the controller. I continued letting down towards Edwards and the distinctive white landmark of Rogers Dry Lake, getting a visual sighting on the dark arrow-like shape of the huge bomber, already two thousand feet above us as it sailed past. I leveled at pattern altitude some fifteen hundred feet over the high desert.

We overflew the dry lakebed, offset to the right of the main 22 runway and I entered the break at 300 knots, throttled back and airbrakes out, turning through 180 degrees to level out on the downwind leg. Fergione took over for a touch-and-go landing.
Three green lights winked on the panel as the gear locked down.

The F-16 curved round in a steep descending turn onto finals. As we came round onto final approach it became apparent that there was a strong crosswind from the right. We were crabbed slightly against the crosswind down final approach, then without fuss we were down, although the narrow-track gear meant that judicious use of aileron and rudder was needed to keep straight in the crosswind.

We had briefed for a touch-and-go and so the throttle went forward to the Military Power detent and the F-16 leaped off the ground again. The red light in the gear handle winked out as the doors closed. Fergione curved us round in a tight turn over South Base, setting us up for our final landing.

Gear down, we started on our descending turn on finals. Then something unexpected. The MASTER CAUTION light on the coaming started to flash and the audio warning sounded.
“That’s the forward fuel,” said Fergione,” It’s normal at these fuel states.” I glanced down. Sure enough the FORWARD FUEL light on the right hand console was illuminated, showing that we were down to 250lb in the forward tank group.

In deference to the gusty conditions, Fergione flew the approach at eleven units AoA, rather faster than the thirteen units of AoA in the flight manual. He explained that the thirteen unit approach equated to a speed of 133 knots at this fuel weight but could result in a certain amount of wallowing on the approach in gusty conditions. This approach worked as advertised. We touched and Fergione kept the nose up for aerodynamic braking throughout our landing run until the speed dropped down to eighty knots.

The F-16 was an impressive fighter in a small package. Smaller by far than the huge F-15 Eagle, it could give a very good account of itself and had amassed an amazing number of kills in combat. For myself, it was a very productive and enjoyable flight, one which had shown to good effect the latest fighter in US Air Force service.

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