Less than 24 hours after conclusion of the rollout ceremony, F-16XL-1 (75-0749), piloted by General Dynamics F-16XL Project Pilot James A. “Spider”
McKinney, started up and taxied to the Carswell AFB main runway, adjacent to the GD factory.9 For the first flight, only full internal fuselage fuel (6,700 pounds) was carried. Two AIM-9L missiles were mounted on the wingtips (store stations 1 and 17) and four dummy AIM-120 AMRAAM missiles were carried on stations 6, 7, 11, and 12. At 10:47 a.m. local time on a sunny Texas day, after success-fully completing functional checks of the aircraft subsystems and the special test instrumentation system, McKinney executed a maximum power afterburner takeoff. During the 65-minute first flight, the aircraft reached a maximum Mach On left: F-16XL-1 photographed at the rollout ceremony at the GD Fort Worth factory on July 2, 1982. On right: Aft view of F-16XL-1 as photographed at the Fort Worth rollout ceremony on July 2, 1982. (Both images Lockheed Martin)
Harry Hillaker (front row, standing hands on hips) and members of the F-16XL design and flight-test team with the first F-16XL, at General Dynamics’ Fort Worth plant. (Lockheed Martin photograph via Robert Wetherall)
number of 0.9 at 30,000 feet, a maximum load factor of 3 g’s, and an angle of attack of 20 degrees. McKinney was reported as saying that the aircraft had a solid ride and performed as predicted, but its flight characteristics were very different from those of the standard F-16.10
During the postflight debriefing and subsequent exuberant celebration festivi-ties, an enthusiastic McKinney said that the F-16XL met or exceeded all expec-tations on the first flight with excellent aircraft handling qualities and systems operations. He reported that the aircraft had a solid feel and was comfortable to fly after only a few minutes. Shortly after the 65-minute first flight, Jim McKinney forwarded the following memo to the F-16XL development team (somewhat, but understandably, understating any issues that had been encountered).
We had an outstanding first flight of the F-16XL on Saturday, 3 July 1982. The aircraft flew like a dream and met or exceeded our goals for the first flight. The systems on the aircraft performed flawlessly and the handling qualities were superb. The F-16XL reflects a tremendous effort by everyone and especially during the past few weeks as everything started coming together. I wanted to congratulate and thank you for your efforts during this program.
The aircraft you have developed and built is a new generation of fighter aircraft and is at the forefront of aviation today. I am hon-ored to be associated with you and am confident we can succeed in the challenges ahead.11
The first flight of the F-16XL-1. This flight photograph was subsequently autographed by GD test pilot James McKinney. (Lockheed Martin)
General Dynamics Vice President and F-16XL Program Director D. Randal
“Randy” Kent quickly issued an attractive first flight certificate to all members of the F-16XL development and flight-test team. It complemented the entire development team with these inspiring words:
These are dates I’m sure we will all long remember. They represent the culmination of an extraordinary achievement by all of you who participated in the birth of this beautiful aircraft.
When we started the project in November 1980, we knew that to fly 19 months later represented a most ambitious and difficult undertaking. But, because of your dedication and personal sacrifices and those of your family, the challenge was met—indeed, we beat the schedule! I am sure you shared with me the thrill and sense of pride when F-16XL-1 took to the air on Saturday morning, 3 July.
As a result of your skill and efforts, we can now offer our country an important new defense weapon—the F-16XL Fighting Falcon.12 First Flight Pilot Report
Jim McKinney’s first flight pilot report, quoted verbatim below, provides excel-lent insight into the initial flight of what would eventually become a significant second career for the F-16XL as a NASA supersonic research test bed.
Objectives:
This was the first flight of the F-16XL. The flight was devoted to functional verification of the aerodynamic design, the checkout of existing/modified/new F-16 systems, and checkout of aircraft instrumentation.
Ground Operations:
All ground operations are straightforward and easily accomplished with minimal pilot workload. Pilot involvement in FLCS [flight control system] is minimal and requires only turning on and then off the test to accomplish a thorough checkout.
Aircraft handling during ground operations was smooth and easy to control. During the taxi test, improper nose strut servicing resulted in excessive nose bounce when taxiing over seams in the concrete
ramp. Proper servicing between the taxi test and first flight signifi-cantly reduced this tendency.
Takeoff:
Aircraft acceleration during the max A/B [afterburner] takeoff was brisk. Aircraft rotation was initiated at approximately 150 KCAS (predicted takeoff 165 KCAS). The pitch attitude changed quickly in response to the slight amount of aft stick applied, indicating a pitch sensitivity with weight on the landing gear (gains will be changed for flight 2). While pitch attitude was definitely control-lable, judicious pitch inputs were required to avoid excessive atti-tude changes. As a result, a less than optimum takeoff attiatti-tude was established and resulted in a 170-175 KCAS liftoff.
Once airborne, the initial pitch sensitivity disappeared and smooth and precise aircraft control was easily achieved. A landing gear down climb to 15,000 ft. was performed during which time this pilot gently started to get the feel of this new aircraft. Handling was pleasant and confidence in the FLCS was quickly gained.
Enroute:
A mild and brief PA [pitch axis] handling qualities evaluation was conducted prior to raising the landing gear and verified the posi-tive impressions experienced during the climb. The landing gear was cycled twice; the JFS [jet fuel starter] started and shut down, ECS [environmental control system] and instrumentation checked prior to departing overhead Carswell [Air Force Base] for the high altitude checks.
A mil [military] power climb to 30,000 feet was initiated at 350 KCAS. Climb rates were good and precise airspeed control was easily achieved. Once at 30,000 ft., stability and control blocks were performed at 0.8M [Mach] and 0.9M. Aircraft response was smooth and quick, and showed excellent handling qualities.
During ½ stick rolls, handling was pleasant; however, an obvious side slip was evident after approximately 180 deg. of roll (post-flight examination of TM [telemetry] traces shows that roll is a bit “over-coordinated” in the current control implementation. This will be corrected later in the flight test program.). At roll termination, the
sideslip immediately went to zero without an obvious overshoot.
During a slow down to 20 alpha [degrees of angle of attack], a light high frequency low amplitude airframe buffet was noted. The aircraft was very solid in all axes during the deceleration to 20 alpha which occurred at 110 KCAS. A mil power sustained turn was completed at 0.9M/30K [Mach 0.9 at an altitude of 30,000 feet]
with results that corresponded exactly to the predictions.
An idle power descent from 30K to 10K was performed to allow for a brief photo session prior to conducting a PA maneuver block.
Aircraft feel in PA was solid and the aircraft could be quickly and eas-ily trimmed at the desired AOA. During 45 deg. bank-to-bank rolls, a sideslip buildup was evident, but was not uncomfortable. Aircraft reactions to raising and lowering the landing gear were minimal. The final two times the gear was cycled prior to landing, the leading edge flap servo light illuminated and reset on the first attempt.
Landing:
A straight-in approach to landing was performed to a full stop land-ing. The aircraft was trimmed to 12-13 deg. AOA (155 KCAS) for the approach and provided a solid platform to perform the land-ing. At one mile from landing some turbulence was experienced and AOA decreased intentionally to approximately 11 deg. (165 KCAS approx.) for the final phase. A constant pitch attitude with no flare landing was performed which resulted in a smooth but faster than optimum touchdown. Concern for the pitch sensitivity noted on takeoff rotation prevented any significant aerodynamic braking attempt. Once the nose wheel was lowered to the runway, aircraft deceleration without wheel braking was not appreciable and the drag chute was deployed to keep from overheating the brakes. Deceleration from the drag chute was excellent. Aircraft directional control with the drag chute deployed (no crosswind) was no problem.13
Pitch Oscillation “Gallop” Issue
A longitudinal oscillation in the pitch axis had been briefly observed by Jim McKinney on the first flight of F-16XL-1. Its impact on aircraft flying qualities would result in an interim fix in the form of a notch-type filter that was inserted in the pitch path of the flight control computer. The notch filter reduced avail-able pitch gain by 25 percent. A prolonged investigation by the Air Force and
GD into the engineering root cause of the pitch oscillation continued well into 1985. This eventually revealed a disagreement between the analytical model of the flight control system and the actual flight control system hardware installed in the aircraft. Flight testing conducted by the Combined Test Force at Edwards AFB determined that a 2.5 Hz pitch oscillation existed in the aircraft longitudinal axis. This oscillation was encountered in the 0.9 to 0.95 Mach number range at all altitudes during 1-g flight. The amplitude or severity of the pitch oscillation increased as altitude decreased (and air density increased). The amplitude of the pitch oscillation was dependent on the specified FCS gain in the longitudinal axis. The gain turned out to be 180 degrees out of phase in the frequency range where the longitudinal oscillation existed. Pilots came to refer to this oscilla-tion as “pitch gallop,” or “lope.” It was considered a general nuisance in 1-g flight. However, as g-level was increased during simulated combat maneuvers, the severity of the oscillation also increased to the degree that it was impossible to adequately track a maneuvering target with the lead computing optical gun sight. The pitch oscillation issue led to a dedicated CTF flight-test evaluation of the F-16XL’s FCS. An inflight excitation test procedure was developed that obtained actual aircraft frequency responses using actual aircraft hardware and aerodynamics at any condition within the flight envelope. As this interesting aspect of the Air Force F-16XL flight evaluation was not completed until much later in the test program (in 1985, well after the Dual-Role Fighter source selec-tion was complete), it will be discussed in more technical detail in a later secselec-tion.14