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Creativity
-- The MRMF concept takes
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MULTI-AXIS THRUST
VECTORING
After the A-12 debacle, I was assigned to the VISTA Multi-axis Thrust Vectoring (MATV) program. This was a well managed project; and, it achieved every objective that it set out to reach. The demonstrated performance of the MATV F-16 was nothing short of outstanding. The VISTA MATV F-16 was the only aircraft in the U.S. arsenal that could outmaneuver the F-16 in those areas of the flight envelope where most air combat converges. Awards for its outstanding achievement were given to the program; and, the project was mysteriously ended. ENIGMA HIDDEN WITHIN A MYSTERY The Air Force must have its reasons to sequester the MATV technology; and, your guess is as good as mine for this decision. I would be the first to admit that the F-16 could not make good operational use of MATV; if it could, this would be most unusual. The reasons are well understood; the F-16 design is already optimized. The additional mass of the MATV installation alters the F-16 inertial properties; this would require a complete redesign of the digital flight control system. In addition, there is no beneficial tradeoff achieved by including MATV on a fighter already configured to function without it. For MATV to be a viable system on a fighter, that fighter would have to be designed from the outset to exploit MATV technology. The MRMF does that. MRMF WE WIN -- TAILS WE LOSE If MATV is going to win a place on the MRMF, it can do so by justifying its added weight. This can be achieved if the MRMF can be designed to replace conventional tail surfaces with thrust vectoring. Remember, the weight of conventional tail surfaces also includes the weight of hydraulic actuators as well as tail structure. The challenge that confronts this decision depends on how we intend to control the MRMF in the event of an engine (i.e., thrust) failure condition. The MATV system can be designed to provide stability and control when the engine is thrusting; but, we need to be able to provide for safe flight in a failed engine state.
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THE MRMF CONTROL SCHEME A tailless flying wing aircraft is designed to be stable and controllable by using wing control surfaces to act as stabilizing elements. Differential lateral drag can be applied to provide for yaw control; and, wing flaps can provide a certain degree of pitch control. Roll control is achieved by the traditional use of wing ailerons. If a fighter is to carry a variety of weapons and stores, it will require enough pitch control power to compensate for a wide range of c.g. (center of mass) conditions. It must be able to do this even with engine failure. The MRMF accommodates this requirement via a variable sweep canard system to augment the MATV pitch control when the engines are working. The canards are designed to control the aerodynamic center of the wing body configuration. This is done to assure the proper moment arm between the c.g. and the aerodynamic center. If the engine thrust fails, the canards will set the aerodynamic center so that the wing surfaces will be able to manage safe pitch control. Effective MRMF engine-out yaw control is achieved by the deployment of asymmetrical speed brakes located aft of the main landing gear housing pods located near the wing mid-span stations. The forward portions of the wing pods house the mission related avionics modules. MISSION RELATED AVIONICS MODULES 90% of all MRMF avionics are stored in two removable mission modules located forward of the main landing gear enclosures. The combined mid-wind housings are referred to as "pods"; because, they will house most of the mission specific hardware. The cone farings at the rear of each pod contain the MRMF speed brakes. The cones are segmented so that they can flare out to provide asymmetrical drag to the MRMF. Differential drag will result in a yawing moment that will be used to provide the MRMF directional stability and control when the engine thrust cannot provide these via MATV.
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"Anyone can make the simple complicated.
Creativity is making the complicated simple." Charles Mingus |
