The following HTML text is provided to enhance online
readability. Many aspects of typography translate only awkwardly to HTML.
Please use the page image
as the authoritative form to ensure accuracy.
Improving the Efficiency of Engines for Large Nonfighter Aircraft
not meet environmental regulations of most of the developed world and is much less fuel efficient than current engines.
The third consideration is that with the exception of the B-52H, all of the other TF33-powered weapons systems are KC-135/B-707 variants or derivatives. Given that the KC-135Rs have been reengined and the E-8 JSTARS re-engining is now in progress, a significant fraction of the nonrecurring engineering costs may be shared among platforms rather than duplicated.
The fourth consideration is that the Air Force maintains a significant engineering and overhaul capability to support its fleet of 2,300 relatively high maintenance TF33 engines. So long as a significant number of TF33s remain in the inventory, the Air Force must retain some overhaul capability. Should all of the TF33s be retired, however, then the $800 million inventory can be disposed of and the more than 188 personnel and 82,000 sq ft of support real estate can be suitably redeployed for other Air Force needs. For these nonnegligible savings to be fully realized, all TF33 engines have to be removed from the inventory. If, for example, all of the KC-135/B-707 variants are re-engined, this may strengthen the case for the B-52.
Taken together, these considerations strongly suggest that TF33-powered aircraft should be considered as a group rather than subjected to the traditional approach—i.e., airframe by airframe studies. In this case, the whole of the savings from re-engining all TF33 aircraft may considerably exceed the sum of re-engining the individual platform types.
The following sections discuss re-engining for each of the current platform types.
E-8 JSTARS WEAPONS SYSTEMS
Throughout the development history of JSTARS a number of engine options have been studied. By re-engining the JSTARS E-8C aircraft, the government will benefit from substantial reductions in fuel burn and other costs of ownership, while enhancing all operational requirements with a new installation that more than meets all environmental requirements.1 However, in each case the conclusions were similar to those for the other platforms that had conducted business case analyses on payback—i.e., the payback period is too long to recoup the significant upfront nonrecurring engineering (NRE) and acquisition costs.
From its inception the JSTARS platform was structured around Boeing 707 aircraft that were being operated by the Air Force, foreign governments, and commercial carriers. The program utilized Boeing 707-320C (Air Force designation C-18) series aircraft obtained in the commercial marketplace as they were being phased out by the major and secondary commercial carriers. The 707-320C aircraft had received its Federal Aviation Administration (FAA) certification in April 1963. At the time the aircraft were procured from the used market, there were only limited engine options offered for them. The original Boeing 707-320 aircraft design goals were to provide an aircraft whose aeronautical performance was optimized for long-range flight, making it the first truly intercontinental jet aircraft. The Boeing 707 had adequate thrust to meet the needs of a commercial operator carrying large loads between distant points on the globe. The engines available for the aircraft back in the 1960s had 18,000 lb thrust in the JT3D-3 or -3B commercial configuration or 19,000 lb thrust in the -7 variant. It should be noted that the wing structure of a Boeing 707-320 series aircraft is nearly identical to the wing structure of an AWACS that is currently operating with a 21,000 lb thrust engine. However, the long radar aperture along the bottom fuselage of the aircraft results in problems with aircraft lateral stability, which is aggravated by increased
On January 18, 2007, the Air Force announced that it had selected the Pratt & Whitney (P&W) JT8D-219 engine to re-engine the entire Joint STARS fleet (Northrop Grumman, 2007).