Guy Norris/LOS ANGELES
NASA, THE US Air Force, McDonnell Douglas (MDC) and Pratt & Whitney plan to accelerate the F-15 ACTIVE thrust-vectoring programme to bring forward demonstration of a tailless aircraft, dubbed the F-15 MANX, boosting the likelihood that MDC will offer a stealthy, tailless derivative of the F-15E to meet South Korea's F-X fighter requirement.
The team had planned to reduce the size of the ACTIVE F-15'svertical tails in stages as it gained confidence with the multi-axis thrust-vector control system, but Air Force ACTIVE/MANX programme manager Maj Bruce DeWitt confirms that a decision has been made that the risk associated with proceeding directly to a fully tailless configuration is "non-considerable".
MDC is considering offering South Korea a stealthy, tailless F-15 derivative to meet competition for the F-X programme from the Lockheed Martin/Boeing F-22 and Sukhoi Su-37, both of which have thrust-vectoring. The company declines to comment, saying only that the F-15 offered to South Korea is likely to have "remarkable changes". Thrust-vectoring was an option on the F-15U offered unsuccessfully to the United Arab Emirates, but not coupled with a tailless configuration.
MDC says that affordability is the key to any F-15 derivatives, that it is "playing the trades" of performance and cost, and that "the aircraft that emerges over the next year or so will be different to today's E".
MDC, which says that thrust-vectoring is a "very exciting technology", wants to keep the F-15's price reasonable "while reaching out in capability."
De Witt says that to produce the F-15 MANX configuration, the ACTIVE F-15's foreplanes would be removed and the tailplanes canted upwards slightly for increased stability in case of a dual engine failure. "We want to prove the maturity of integrated propulsion-control and we want to show the full-envelope performance benefits of propulsion control. We're not just talking about high angle-of-attack here - we are talking supersonic drag reduction," he says.
"We are going to introduce the inner-loop propulsion control laws into the [ACTIVE] aircraft as the next step, and that's necessary for MANX," DeWitt says. "MANX is the next logical step. We're working on getting approval for that phase right now, though the programme is already being funded. We're hoping to accelerate funding to provide earlier results."
He says that given an "unconstrained" budget, MANX flights could be conducted in mid-1998. "We don't think that needs additional approval.". Tentative South Korean air force planning calls for the F-X to be selected in 1998, with the first of an initial batch of 60 aircraft to enter service in 2002 (Flight International, 30 October-5 November, P9). MDC is also trying to interest the USAF is an advanced F-15E derivative, possibly to meet its Replacement Interdictor Aircraft (RIA) requirement for a successor to the F-15E and Lockheed Martin F-117, to enter service after 2010.
Alternatively, a stealthy F-15 derivative could be offered as an interim aircraft, enabling the RIA requirement to be delayed until after the Joint Strike Fighter (JSF), due to enter service around 2010 as a Lockheed Martin F-16 replacement, is well into production.
DeWitt is careful to distance the F-15 MANX effort from the F-22 programme. "We don't see this as a competing aircraft. It's just a research testbed," he cautions. According to DeWitt, the Air Force felt it had a chance, with the F-15 MANX, "...to show the huge benefits of tailless technology. This is technology that will be incorporated into future fighter demonstrators, not just JSF, but beyond that," he says.
Additional reporting by Graham Warwick
Source: Flight International
