F-14 Test

A total of 19 aircraft were assigned to the F-14A flight test program, with each assigned a unique set of flight trials. The first aircraft had been intended for envelope expansion flights and high-speed testing. Since it was necessary to conduct these tests early in the program, the uncompleted twelfth airframe (BuNo 157991) was completed in record time, renumbered “1X” and assigned the tasks originally sched­uled for the ill-fated first aircraft.

Early flight tests revealed a minor buffeting when the flaps were lowered. Investigations showed that turbulent airflow through a gap between the spoilers and the wing flaps was impinging on the horizontal stabilizers and causing the problem. The correction was to move the spoilers slightly further aft, eliminat­ing the gap. The only truly serious anomaly encountered during flight test was an engine intake buzz and a tendency for the TF30 engines to stall at high angles of attack. The intake buzz was corrected by a partial redesign, but the TF30 problems would contin­ue to haunt the Tomcat, as they had the F-111.

Flight testing of tine F-14 used Grumman’s automated teleme­try system (ATS). The aircraft flew in a corridor of the Atlantic coastal air-defense identification zone (ADIZ) located off Long Island and around 100 miles in length. The ATS allowed aircraft under test to send data directly to ground sta­tions which could analyze the data in real-time. Using the ATS, engineers were able to sit at ground-based consoles and monitor the progress of each test flight. If something of interest happened, the engineers could ask the pilot to deviate from the planned test profile to get more data. Airborne telemetry was received by a ground station located at Terry Hill, about three miles from the Calverton Plant 7. The use of ATS, along with extensive in-flight refueling during test flights, is estimated to have saved 18 months during the flight test program.

In all, the following results were realized dur­ing the F-14A’s early flight test program:

  • atop speed in excess of Mach 2.40;
  • flown to 90° angle-of-attack without a departure from controlled flight:
  • capable of sink rates in excess of 24 fps without structural damage;
  • capable of-1-9.5 g and-5.5 g through a major portion of the flight envelope;
  • the ability to fly 500 nm, operate in maximum afterburner for two minutes, then return to the point of takeoff;
  • the ability to fly full aft stick while indi­cating 0 KIAS, at 41° AOA; and,
  • the aircraft could be safely landed with the wings at 68° sweep (full back).

One problem which quickly became obvi­ous on the prototypes was a reflection off the inside of the windscreen. An electrically con­ductive coating on the Inner layer of the wind­screen was used to heat and defrost the glass. If the surface to which this conductive coating was applied had been parallel to both outer windscreen surfaces, the reflection problem would probably have been insignificant. How­ever, the inner coated surface was not parallel to either of the outer surfaces, and the rays that it reflected were not parallel to the rays from the outer surfaces, thus resulting in the generation of spurious images. The inner conductive coat­ing was removed, and the spurious images went away. A forced air defrosting system was installed to keep the inner surface frost free.

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