[7] The first research program undertaken at the new Ames Aeronautical Laboratory concerned the development and testing of icing protection systems for military aircraft. The need of the military services to operate their new high-performance bombers and transports year around in adverse weather led the NACA to initiate this program. This effort had begun sometime earlier at the Langley Aeronautical Laboratory with wind tunnel and flight tests. The flight activity, including personnel, was relocated to Ames in 1940. The first flight experiment at Ames was carried out on the O-47A-1, originally an Army observation aircraft (fig. 2), to obtain initial results for this program. As noted in table 1, this was the first aircraft to arrive at the laboratory and, starting in September 1940, it served for a brief time as the research aircraft for the evaluation of heated-wing deicing. The following January, icing research continued with the arrival of the Lockheed 12A Electra (fig. 3), which had been involved in this research at Langley. The deicing concept involved circulation of hot exhaust gas from the engines through the wings, and it proved to be effective. The first research publication of the Ames Aeronautical Laboratory (ref. 2) covered this work. This system was further developed to use inducted free-stream air warmed by an exhaust heat exchanger; it was then applied to the B-17 and B-24 heavy bombers (figs. 4 and 5) for wing and empennage deicing. Flight tests were carried out during the winter of 1943 at the Army Air Force Icing Research Base in Minneapolis. Results published in reference 3 for the B-17 showed that the system worked; similar performance was achieved for the B-24. With that success, the system was used on production versions of the Navy's PBY Catalina.

Following the B-17 and B-24 programs, a Curtiss C-46A Commando (fig. 6) was developed as a dedicated flight research facility and was used extensively for testing advanced deicing techniques. The aircraft employed fuselage-mounted airfoil models at one time as a part of this work. Additionally, the aircraft was equipped with instrumentation to collect data to aid in predicting icing conditions. Operations were carried out in natural icing conditions without incident. Analytical predictions of deicing system requirements were found to be conservative and, when they were met, ice buildup on the wings was prevented (ref. 4). Propeller icing experiments were also conducted and measurements were obtained that showed the propeller efficiency loss caused by ice formation. Analyses of the effects on propeller efficiency showed qualitative agreement with the flight data (ref. 5). Later on, the BTD-1 Destroyer was also the subject of a deicing study, and electrically heated "gloves" were tested on the wings and tail of the P-38J Lightning (fig. 7). Ames' original staff of pilots involved in these flight tests appears in figure 8.

[8] Reflecting the major contributions made at Ames over the duration of this program, Lew Rodert received the Collier Trophy in 1947 for his leadership of the effort, and, in 1943, Bill McAvoy received the Octave Chanute Award for flight testing in dangerous icing conditions. Other significant contributors were Larry Clousing, who, along with McAvoy flew many hazardous test flights, Carr Neel, who made significant contributions to the design of the deicing system for the C-46 and developed an instrument to measure liquid water content in flight, and Alun Jones, who also contributed to the system design. Jones wrote the summary report of the C-46 work (ref. 6) that described the analysis of heat requirements for ice protection; the design, fabrication, and installation of the system; performance tests in operational icing conditions; and the evaluation of effects on cruise performance and structural integrity of the wings. It concluded that prediction methods were now adequate, though still conservative for system design, and that thermal effects on the wing structure could be avoided with proper design approach. Interest in icing research at Ames virtually ceased by 1949 as the Flight Engineering Branch shifted emphasis to transonic studies.

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