National Security: FCF

When an aircraft has undergone major maintenance such as an engine change, it needs to be test-flown to ensure that it works properly before rejoining the fleet. The Air Force calls this a “functional check flight” or FCF. There is a separate and distinct checklist that needs to be completed before certifying the jet ready for normal flight operations. Very early in my flying career as a 24-year-old lieutenant, I was put on FCF orders for the 388th TFW at Korat AB, Thailand. I continued to fly F-4 FCFs for the rest of my flight career. An FCF profile in the Phantom took about 30 minutes to complete and really began from brake release at the end of the runway. From the rear cockpit, I would call for the next test in the sequence which the pilot would perform and I would record the results on the checklist for maintenance debriefing. Some of the checklist was accomplished in the rear cockpit alone – mainly systems integration checks. FCFs were always accomplished with a “clean” aircraft meaning that no external tanks or ordinance was carried. We had inboard pylons and, other than that, there was no external drag. Internally, the F-4 carried about 12 thousand pounds of fuel. When we used half the fuel, the thrust from the two GE J-79 engines exceeded the weight of the aircraft and we could climb nearly vertically without losing speed. The highlight of the FCF was the Mach 2 run. The objective was to see the vari-ramps in front of each engine inlet extend, which began to program at Mach 1.2. Vari-ramps are necessary to sufficiently speed-up the airflow to permit high Mach numbers. Rarely during FCFs would we get much above Mach 1.8 because of drag and less than ideally tuned engines. But once I did exceed twice the speed of sound. It happened at Korat in the summer of 1972. The aircraft was a relatively new, low hour F-4E. The J-79-17 engines were really hot. We began to climb above 40,000 feet with both afterburners cooking. Passing 50,000 feet, the Mach meter exceeded 2.0. When we topped out near 52,000 feet, the Mach meter registered 2.05. On the true airspeed meter, we zipped past 1400 knots. At that point, you gently pull the throttles out of full afterburner (to avoid a compressor stall – made that mistake once) and push the aircraft over into a descent. The aircraft will begin to slow pretty quickly as you descend into thicker air. And the fuel is getting really low at that point – as fast as the airspeed increased, the fuel gauge was going in the opposite direction. Time to land. Undoubtedly, the coolest FCF I was ever involved with occurred in Germany in 1981. Two years earlier before I arrived at Spangdahlem AB, an F-4D (66-8813) survived a crash landing. The reclamation experts determined that the aircraft was repairable, so a contract was let with Messerschmitt-Bolkow-Blohm (MBB) in Ingolstadt to rebuild the jet. The repairs took a long time to happen, complicated by the arrival of a new wing damaged going under an overpass only ten miles from the factory. Finally, it was ready to fly. I joined an FCF pilot from the 480th TFS and a driver took us to Frankfurt to pick up the contracting agents. Then we drove another four hours to southeastern Germany and the MBB plant. After a thorough review of the documentation and a detailed walkthrough inspection, we strapped into the Phantom and did all of the preflight ground checks. Takeoff was smooth and we went through every FCF checklist item in detail, documenting the results. We found discrepancies, but nothing major. After landing, we recommended acceptance, so the contracting officer signed for the jet, signaling MBB that their involvement was finished. It was a big day for the workers who had put in nearly two years of labor and parts to return the jet to flyable status. Company officials wined and dined us at a local gaust haus in celebration that night. Early the next morning, we arrived at the airfield to fly the jet back home. We climbed aboard once more for the hour long flight back to Spangdahlem. Upon landing, the tower operators greeted us: “Welcome back 813.” It was a proud moment. A few years later as the head of quality assurance in the test wing at Eglin, I flew FCFs once again, but managed more of them as maintenance officer for the variety of eight different aircraft types we flew. Sometimes, I reflect on the things I did in my Air Force career and realize how fortunate and blessed I have been.