USAF test pilot Maj. Mike Gerzanics and I were the aircrew for the airplane's first flight on 2 July 1993 in Fort Worth. We accomplished a lot in a short time. During the first two and one-half months of thirty flights, for example, we expanded the flight envelope to a stabilized angle of attack of eighty-three degrees and saw transient AOA values of well over 100 degrees. What follows are my impressions of the airplane during the envelope expansion phase of the program. The operational phase-in which the aircraft was flown in a variety of tactical engagements-is the subject of James Sergeant's accompanying article.

Maneuvering the F-16/MATV above the normal AOA limit of twenty-five degrees is effortless. The pilot simply points the nose where he wants it to point. Below 300 knots, a pitch stick input from the pilot is a pitch rate command. As the AOA gets above twenty degrees, a slight AOA signal is fed back to the tail and nozzle commands, making the airplane feel "stable," or as if the nose wants to come down. Effectively, the pilot has pitch rate reserve, or the ability to point the nose from any AOA, of up to eighty-five degrees.

If the pilot commands full aft stick in a hurry, the airplane can easily achieve AOA values over 100 degrees. The F-16/MATV demonstrated this capability near the end of our initial envelope expansion flying. After stabilizing the airplane at sixty degrees AOA, which takes only a small amount of aft stick force, I snapped the stick full aft and was able to command over thirty degrees of pitch change and near 100 degrees AOA. With a slight push forward, I could easily recapture sixty degrees or any desired pitch reference within a degree or two.

We've taken the airplane into the pure vertical without regard for how low the speed decayed and convinced ourselves that we can predictably point the nose in pitch at any airspeed. Even while falling flat on our back (at negative ninety degrees AOA), we could accurately command nose position with forward or aft stick commands. If you want lots of pitch rate, pitch attitude change, or pointing capability, the F-16/MATV can deliver.

Maj. Gerzanics demonstrated early on in our flight test program that the Russians no longer have a monopoly on the dynamic "Cobra" maneuver. The F-16/MATV is ideally suited to perform the Cobra effortlessly. The MATV will go from 200 knots level flight to beyond the vertical in about two seconds. While little airspeed is left when the airplane reaches the vertical position, its thrust keeps the flight path from falling right away. Plus, we can easily push the nose back to the horizon and start accelerating in a hurry without losing altitude.

Your standard F-16 does not exhibit much buffet when operating within the flight envelope of the normal AOA limiter, except at higher transonic Mach numbers. At specific places beyond the limiter, we encountered a noticeable and meaningful buffet. Moderate buffet begins at about forty degrees AOA and continues until fifty degrees, at which point it diminishes to near zero. The pilot should be able to use the buffet as a cue to make stick or pedal input decisions and to keep the airplane from extremely high AOAs, if these angles are not desirable. Other forms of cueing, possibly presented on the head-up display, are needed for the pilot to optimize the use of thrust-vectoring. Maj. Billie Flynn, an exchange test pilot who flew F-18s in Canada, noted this requirement after his first flight. He stressed the importance of the pilot's being able to assess the AOA and energy state quickly.

Refining the flying qualities in the roll and yaw axes proved trickier for F-16/MATV test pilots and for the control system engineers. Roll takes on a different character above about thirty degrees AOA. If the airplane were to roll solely about its own longitudinal axis, as at low AOAs, the nose would not appear to move in yaw throughout the roll. However, at higher angles, what started out as AOA would become sideslip (the yaw angle from the relative wind), then negative AOA, and so on as the roll progressed. Besides causing some pilot discomfort, this AOA/sideslip interchange produces erratic roll-rate response. So at the higher AOAs, the control system tries to force the airplane to roll about the velocity vector in response to the pilot's roll stick input and attempts to keep sideslip at zero or very small. In other words, the F-16's flight control computer attempts to coordinate a turn automatically.

Rolls at high AOAs require a couple of tradeoffs. The first involves whether to roll with the stick or pedals. As the AOA increases, the roll about the velocity vector looks more like yaw; therefore, some pilots feel that the pedal is a more intuitive controller. Above sixty degrees, a roll looks like a flat spin. The second tradeoff involves directional stability. If the system attempts to zero the sideslip too strongly, the nose appears to be yawing. If sideslip is allowed to be a little looser, the response to a roll command is not always predictable.

The F-16 loses most of its directional stability (the natural ability to keep the nose pointing into the relative wind) between thirty and fifty degrees AOA because most of the vertical tail is blanked by the fuselage at these angles. Before thrust vectoring came along, we had no way to compensate for this lack of stability since the rudder also lost effectiveness above thirty-five degrees AOA for the same reason. This situation changes with vectored thrust. We can now produce a yawing moment with the nozzle at any AOA or airspeed. So the directional stability can be augmented if the flight control system can correctly determine the amount of sideslip.

Our first attempts to maintain stabilized AOA values from about thirty-five degrees through fifty degrees, though simple in the pitch axis, were complicated by the airplane's tendency to develop random nose wandering. The resulting sideslip would then cause roll oscillations, which looked in some ways like the classical wing rock seen in many jets at higher AOAs. When we tried to counter the roll oscillations, the roll stick inputs deflected the flaperons, which are also powerful yaw devices at these AOAs. If a rapid pitch input was made, the nose would slice noticeably as the AOA went through this region. The nozzle power was always strong enough to counter this slice before it became uncontrollably large. However, the slice would still cause the plane of the pitch motion to deviate from where we wanted it. Since the nozzle had to be borrowed somewhat by the yaw axis to counter the slice, the pitch rate would decrease. While none of these motions and reactions presented a loss-of-control problem, they would likely complicate tactical tasks.

These tradeoffs, however, do not overshadow the remarkable capability of the airplane in roll and yaw axes at AOAs above the normal limiter. At forty-five degrees and below, the airplane could be rolled-with full stick or full pedal-through 360 degrees of bank angle change with no hint of departure. Above fifty degrees, that same full stick or pedal input would cause the airplane to rotate around the horizon at up to fifty degrees per second. Controllably, I would add. I performed these maneuvers many times in Lockheed's MATV simulator before flying the real thing. Even though I had great confidence in our engineering team, I didn't expect to perform these maneuvers so easily in the real thing.

We had time to make one flight control change last September to improve the flying qualities in the roll and yaw axes and to address those tradeoffs I mentioned earlier. With comments provided from all six of the test pilots who had flown the airplane, Lockheed's flight control system engineering team identified some key options to be compared in flight. We started flying the new control laws in October and settled on a combination of options that eliminated the nose slice during aggressive pulls except at higher speeds. The change improved the directional stability considerably from thirty to fifty degrees AOA. Yaw pedals became the favored controller for maneuvering above forty-five degrees AOA.

With the improved flight controls, we got to work on tactical maneuvers. We refined techniques for performing a J-Turn, which is a rapid pitch maneuver to establish AOA beyond sixty degrees followed immediately by a roll input that yaws the airplane through the desired turn angle. With pitch rates up to fifty degrees per second and yaw rates of the same magnitude, anyone can appreciate the turn rates this maneuver can achieve. We also refined a technique for the hammerhead, or buttonhook, turn. This maneuver allows the airplane to rotate nearly 270 degrees in pitch while remaining in the same spot in the sky. Most of these maneuvers and a few others were incorporated into the demonstration flights for the VIPs quoted in this article.

The MATV airplane could do what I've described here because of the incredible performance and operability of the GE F110 engine. We were prepared to encounter occasional pop stalls as the AOA surpassed sixty degrees, particularly if sideslip was present. We experienced only one pop stall throughout the program (at an aggravated sideslip and high AOA condition). And we didn't achieve this level of performance by pampering the engine. To determine whether we needed throttle movement restrictions, for example, we explored throttle transients at some extreme conditions. At seventy degrees AOA in full afterburner, we canceled the throttle to military power, waited three seconds, and reselected afterburner. No problem. The afterburner lit smoothly. So we tried it again at seventy degrees, only this time holding full pedal to generate fifty degrees per second of yaw rate. Same result.

We also didn't experience any transient airplane responses due to different thrust levels. The flight control system made throttle transients invisible to the pilot. When we started the program, we had no idea how reliable the engine would operate in afterburner with minimum airspeed and distorted inlet flows. But we understood that, for thrust vectoring to be accepted in a single-engine aircraft, engine operability had to be unquestioned. Not only has the engine met those requirements, but the wear and tear on the new nozzle has also been less than expected. The team from General Electric deserves a lot of credit for making this fighter pilot's dream machine come true.

Joe Sweeney is a Lockheed Martin test pilot and manager of flight operations in Fort Worth.