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P-9 LRAACA [Long-Range Air ASW Capable Aircraft]

The P-9 was a modified civilian MD-91 proposed in 1988 for the Long-Range Air Anti-Submarine Warfare Capable Aircraft (LRAACA) competition for the next generation maritime patrol aircraft.

In May 1987, OSD directed the Navy to conduct a patrol aircraft mission requirements determination study (payload, range, speed, survivability,etc.). To complement this study and enhance the RFP, the Navy released a draft RFP to industry soliciting comments on the operational potential of commercial derivative aircraft to perform the patrol aircraft mission. In September 1987, the Navy released a final RFP, incorporating the findings of the OSD-directed study and the responses from industry. Three proposals were received and evaluation began in February 1988.

Turbofans in civil aircraft are generally divided intro three classifications, bases on by-pass ratio: low bypass (1:1), medium bypass (2 or 3:1), and high bypass (4:1 or greater). During the 1980s, GE developed the Unducted Fan UDF unducted ultrahigh bypass ratio turbofan, which eliminated the need for a gearbox to drive a large fan. This design was made possible by a new material development in titanium, light-weight stainless steel, and composite materials. The jet exhaust drives two counter-rotating turbines that are directly coupled to the fan blades. These large span fan blades, made of composite materials, have variable pitch to provide the proper blade angle of attack to meet varying aircraft speed and power requirements. Powerplants such as the UDF engine are capable of reducing specific fuel consumption another 20-30 percent below current subsonic turbofans. The propfans required high by-pass ratio of 30:1 came from dual 12- to 15-foot diameter propellers with a higher tip speed than propellers. These engine will be known as "ducted UHB" engines.

First flown in August 1986, the UDF is a pusher-type propfan with two counter-rotating rotors of eight blades each. While NASA and its contractor team were pursuing propfan technology development in one directionPropfans generate lower frequency sound pressures than do turbofans, and the supersonic blade tip speed greatly increases the acoustical energy propagated. These factors demand extensive research toward reducing community/cabin noise and designing methods of protecting against sonic metalfatigue in aircraft structures. Such research is conducted in facilities like this Douglas Aircraft anechoic chamber, where engineers use a full-scale pressurized section of a DC-9 fuselage to study structural sound transmission under conditions as close as possible to actual cruise flight.

In a cooperative General Electric/ NASA program, the UDF was extensively ground tested in 1985-86 and it demonstrated a fuel consumption rate 20 percent better than modern turbofans. Then General Electric teamed with Boeing Commercial Airplane Company to test the UDF in flight aboard a modified Boeing 727 jetliner. Flight tests began in August 1986 and continued into 1987. General Electric also built a second demonstrator engine for 1987 flight tests on a McDonnell Dougias MD-80 twinjet. The company's schedule calls for engine certification by the end of 1990 and availability for service in 1991-92.

A new propfan program, a direct offshoot of NASA propfan technology, was launched in 1986 when Allison Gas Turbine Division and Pratt & Whitney Division of United Technologies began a joint venture to pursue commercial, and possibly military, applications of the propfan. The development team includes, in addition to Allison, two other members of the NASA PTA industry group: Hamilton Standard (propfan) and Rohr Industries (nacelle).

The team built a demonstrator engine known as the Model 578-DX, a 10,000 horsepower system in which an Allison turbine drives a counterrotating pusher propfan of two six-bladed rotors. Wind tunnel tests started in 1986 and continued into 1987. The team has signed an agreement with McDonnell Douglas for flight tests on a modified MD-80 beginning in December 1987. In addition, the group is defining a production-type propfan for projected airliners of the 1990s. Targeted for a fuel consumption rate 30 percent better than the best similarly sized turbofans that will be available in the same time frame, the advanced engine will have a bypass ratio of 50-60 to one.

The Navy selected Lockheed in October 1988 to develop the LRAACA.

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Page last modified: 07-07-2011 02:34:58 ZULU