SP-3300 Flight Research at Ames, 1940-1997

 

In-Flight Thrust Reversing, Steep Approach Research

 

[43] The Navy took increased interest in low-speed flight when the introduction of jet aircraft to the aircraft carrier revealed flying qualities problems that had not been experienced with piston-powered aircraft. One concern related to the adverse effect on flightpath control of the jet engine's slow response to the pilot's throttle inputs. Following an early simulation investigation of the selection of approach speeds for landings aboard ship, an in-flight thrust reverser was evaluated as one means to allow pilots to quickly change the longitudinal component of thrust without having to change engine rpm. 25 This concept was investigated in the 40- by 80-foot wind tunnel at Ames in order to determine stability and control influences; flight tests in the F-94C aircraft then followed. The reverser installation on the F-94C can be seen in figure 91. Seth Anderson was the project leader of this work with George Cooper as project pilot. Results demonstrated an improvement in flightpath response to thrust control, an expanded descent flight envelope over a wide range of speeds, and improvements in touchdown precision (ref. 96). A demonstration flight program was arranged for Navy, Air Force, and airline pilots in order to expose them to the use of the thrust reverser in flight. Later, the thrust-reversing concept was applied to the .....

 

Figure 91. Thrust reverser on F-94C. From left to right: Air Force Major E. Sommerich, Seth Anderson, Lt. Col. Tavasti, and George Cooper.

Figure 91. Thrust reverser on F-94C. From left to right: Air Force Major E. Sommerich, Seth Anderson, Lt. Col. Tavasti, and George Cooper.

 

[44]....DC-8 commercial transport to achieve the rapid descent capability required for FAA certification.

Terminal-area approach and landing studies continued at Ames with conventional aircraft. The first CV-990 at Ames, which became the airborne science platform, Galileo I, was used for direct lift control (DLC) research in 1968. The aircraft's spoilers were coupled to the flight control system to provide better flightpath response during the approach and landing (ref. 97). Dick Bray was the research leader and Fred Drinkwater and Bob Innis participated as test pilots. This DLC system was demonstrated to engineers and pilots of the airline industry. It was eventually incorporated as part of the Lockheed L-1011 flight control system, and was instrumental in achieving excellent automatic landing performance for that aircraft.

Steep descent testing, including power-off landing approaches and demonstration of minimum lift-to-drag ratio (L/D) landings came out of the interest in the use of low L/D lifting bodies for recovery to landing from space. The question posed to the flight research organization concerned how low an aircraft's L/D could be for the aircraft to still be landed successfully. 26 Flight tests with the JF-104A Starfighter were conducted by Fred Drinkwater, who demonstrated steep approaches that were ultimately used by the space shuttle (ref. 98). These two-segment profiles consisted of a steep upper segment starting around 25,000 feet and aimed at a target a mile short of the runway, followed by a 3-degree path to the touchdown point. These profiles became widely known within the test pilot community as the "Drinkwater Approach." The CV-990 was also used for space shuttle approach and landing studies. Ames guidance and navigation expertise was tapped to develop concepts which would be used by the shuttle in this flight phase. Through Ames' efforts, supported by Sperry's Flight Control Division, a digital navigation, guidance, and autopilot system was installed in the aircraft to test the feasibility of energy-management approach concepts for an unpowered vehicle. Flight tests were carried out in 1972 on the Galileo I and, in 1975, on the second CV-990, Galileo II, by Drinkwater, with technical direction by Fred Edwards and John D. Foster, along with significant input from Gordon Hardy on the pilot's system interface. They developed the circular path geometry following reentry to intercept the final steep straight-in path and provided guidance and energy management for this path with the digital autopilot (ref. 99). Approaches were made with the engines at idle from an altitude of 40,000 feet at speeds of at least 200 knots. Results showed that, with the proper system design, safe approaches and precise landings could be achieved with an unpowered vehicle. This complete system demonstration contributed to the decision to remove air-breathing engines from the final shuttle design. 27

The second CV-990 was also equipped with a digital navigation/guidance/automatic-landing system to study energy-management landing-approach concepts for commercial jet transports. A "delayed flap" concept that reduced fuel use and approach noise was developed and flown in 1975 (ref. 100). Demonstrations of this system were [45] made for airline representatives. Drinkwater flew these tests with technical direction by John Bull, Fred Edwards, and John D. Foster. In a somewhat similar vein, noise-abatement landing approach patterns, which were explored initially on the Boeing 367-80 by Hervey Quigley, were investigated in an extensive program led by Dallas Denery and conducted by an Ames team in collaboration with American Airlines and United Airlines. The purpose of Denery's work was to develop an avionics system that would allow commercial jet transports to perform two-segment landing approaches under instrument flight conditions. 28 The tests, flown in 1971 using an American Boeing 720 and in 1973-74 on a United Boeing 727 and Douglas DC-8 aircraft with crews from the airlines, FAA, and NASA, showed the effectiveness of a two-segment descent profile in substantially reducing noise on the ground under the approach path (ref. 101).

The various aircraft are shown in figures 92-96 and are listed in table 7. Flight operations personnel in 1970 appear in figure 97.

 

TABLE 7. AIRCRAFT USED FOR IN-FLIGHT THRUST REVERSING AND STEEP APPROACH RESEARCH

.

Aircraft Name

Arrival or First Flight Date

Departure Date

.

F-94C-1 (AF 50-956 NACA 156)

July 29, 1954

November 18, 1958

JF-104A (AF 56-745A)

March 19, 1959

May 6, 1960

CV-990 (NASA 711)

April 2, 1965

April 12, 1973

CV-990 (NASA 712)

December 10, 1973

July 17, 1985

 

Figure 92. Lockheed F-94C-1 Starfire.

 

Figure 93. Lockheed JF-104A Starfighter.

Figure 93. Lockheed JF-104A Starfighter.

 

Figure 94. Convair 990 Galileo I.

Figure 94. Convair 990 Galileo I.

 

[46]

Figure 95. Convair 990 Galileo II.

 

Figure 96. United Airlines Douglas DC-8.

Figure 96. United Airlines Douglas DC-8.

 

Figure 97. Flight operations personnel circa 1970. From left to right: Bob Innis, Frank Brasmer, Fred Drinkwater, Dick Gallant, Gordon Hardy, Glen Stinnett, Jean Moorhead, George Cooper, Ron Gerdes, Dan Dugan, Jim Satterwhite.

Figure 97. Flight operations personnel circa 1970. From left to right: Bob Innis, Frank Brasmer, Fred Drinkwater, Dick Gallant, Gordon Hardy, Glen Stinnett, Jean Moorhead, George Cooper, Ron Gerdes, Dan Dugan, Jim Satterwhite.


25. George Cooper and Seth Anderson 1998: personal communication.
26. Fred Drinkwater 1998: personal communication.
27. Brent Creer 1998: personal communication.
28. Brent Creer 1998: personal communication.

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