Flight Testing the F-12 Series Aircraft

The airplanes were tested largely within the framework of military specifications applicable in the 1965-1966 time period and did extremely well in meeting the published requirements. The wide range of speeds and altitudes made the normal design flight profile the most logical performance testing area, with limited excursions for off-design checks. Stability and control tests included enough without stability augmentation operative to assure adequate definition of basic aerodynamic coefficients. Structural flight tests were at critical design speeds and weights. Safety chase aircraft information at high supersonic Mach numbers provided interesting results. I. Introduction T HE flight testing of Mach 3.0+ aircraft is impressively different from slower vehicles, principally due to the test environment. The low density of the atmosphere, high speed and high stagnation temperatures in the primary flight regime result in stringent demands on flying qualities and temperature tolerance and conditioning. However, the published requirements to be met were not greatly different from those of slower speed aircraft, nor were test techniques. Performance, stability and control, and structural tests were flown within the rules framework of military specifications and related documents, just the same as any new aircraft entering the inventory. Although the aircraft was optimized for the very-high very-fast range of operation and not to meet specification requirements, it did extremely well in meeting these standard requirements. For example, there was little difficulty encountered in the cold weather tests in the big hangar at Eglin AFB. It turned out that, although the airplane was built to withstand very high temperatures, it withstood very low temperatures almost equally well, with only minor procedural changes. Three aircraft were used in the Category I tests for a given model, one highly instrumented for aircraft parameters and two largely for payload systems test. The flying rate for one model is shown in Fig. 1. It is typical of those aircraft which advance the frontiers of aviation, that during the initial phase the flying rate is low while early problems are found and fixed, then picks up and remains at a much higher rate for the program duration. One model flew to 1.5 Mach number on its first flight. A not-to-scale altitude-speed envelope is shown in Fig. 2. This is to show envelope clearance in Category I, sometimes to a greater degree than intended. As a step preparatory to flight, the ejection system was qualified. Both ground and inflight tests were made, using a two-seated F-106 for the flight phase. The skunk works philosophy has been to use pressurized clothing for individual protection instead of capsules. There has been an excellent success rate with such protection, including one ejection at high Mach. The pressure suit also provided excellent protection in cases of cockpit depressurization at high altitude. There is substantial cockpit depressurization when both inlets are unstarted, resulting in virtually full inflation of the suit. With only one inlet unstarted the pressurization is much less severe.