Creativity -- MRMF STOL technology


MRMF STOL PERFORMANCE

We now address an area of fighter design that is at the heart of every configuration--the lifting elements.  There was a time when this only meant "wing design"; but, an enlightened understanding of "lift" now includes all the elements that contribute to the lifting ability of a fighter.

It is here where the design of the MRMF really departs from conventional thinking; the main reason being that the MRMF wing is designed to produce double the lift of conventional wing designs. The MRMF wing-body lifting system is designed to produce lift at angles of attack far beyond the normal operating range.  It does this employing dynamic boundary layer control, DBLC, a "creative" scheme for wing stall suppression.

Because this scheme is unique, and vital to the MRMF mission profiles, the mechanization of MRMF DBLC STOL technology is maintained privately as proprietary information. It will suffice to say that the MRMF is capable of carrying 14,000 - 16,000 pounds of deployable stores at speeds as low as 100 knots equivalent airspeed (EAS).  It can do so with a total configuration weight of only 56,000 pounds, while carrying 20,000 pounds of internal fuel.

The MRMF can takeoff and land from a 2,000 foot road and deploy its stores 1,000 nautical miles from its launching site without refueling.  The MRMF can carry two 4,000 pound ALCM cruise missiles and launch them 1,000 miles from home base.  It can do high altitude reconnaissance at 60,000 feet and remain there for half the day.

UNRESOLVED WING DESIGN ISSUES

Flying at extreme angles of attack has it problems. An aircraft that uses only wing lift for takeoff and landing must rotate its wing to an angle where enough wing lift is produced. For the MRMF, this angle is higher than conventional fighter angles of attack. While vectored thrust can be used to assist in lifting the fighter, the engine also must be rotated somewhat in order to achieve high thrusting angles.

The British have devised a ramped aircraft carrier deck to support Harrier STOL takeoff with heavy stores.  The Harrier is rotated as it rolls up the ramped end of the flight deck; and, this allows the engine thrust line to be quickly changed to support more weight at launch. My experience with the F-8 Crusader would suggest the use of variable wing incidence to achieve high angles of attack without fuselage rotation.  This calls for a "high wing" configuration, much like the Harrier.  This is a viable option for the MRMF.  Conventional high wing designs reduce the effectiveness of a vertical tail; but, obviously, this is a non-issue for the MRMF.

MRMF SUPERSONIC CAPABILITY

Equipped with an F-110 class engine, having 33,000 pounds of thrust, the MRMF should be capable of supersonic flight when all external stores are deployed. The absence of tail surfaces is only a concern where supersonic directional stability is concerned. With a high bandwidth MATV system, this should be manageable. Engine-out recovery from supersonic flight needs to be managed by both the variable sweep canards and the asymmetric wing pod speed brakes.

The variable sweep canards play an important role in supersonic flight; they help maintain a reasonable "static margin" as the MRMF makes the transition between subsonic and supersonic speeds.  The wing aerodynamic center (a.c.) generally moves aft, going from subsonic to supersonic conditions. To help maintain overall vehicle balance, the canards need to be moved to lower sweep angles, exposing more surface area to the supersonic airflow.  This is used to maintain the vehicle a.c., offsetting the wing effects.

The forebody of the MRMF has an ogive cross-section with the horizontal stretch being about twice that of the vertical depth. This is good design, and is an important feature of the F-16; it is, in large part,  responsible for the excellent stability exhibited by the F-16 family of fighters. The forebody canards support this feature.

The ogive forebody of the MRMF accommodates the installation and mechanization of the variable sweep canard control surfaces.  Currently, both canards move in a symmetric fashion; this condition would suggest the use of only one actuator for the canard system.

MRMF WING ACTUATOR SYSTEM

The MRMF has both inboard flaperons and outer panel ailerons.  Since there are currently two outer panels, the aileron actuators are integral to the outer panels. All actuators on the MRMF are electrohydraulic in make. Two actuators are required for the two flaperons, two for the outer panel ailerons, two for the outer panel leaded edge flaps, two for the two main landing gear and two for the two wing pod speed brakes.  One actuator is required for the variable sweep canards and one for the nose gear; and, if variable wing incidence is to be employed, there will also be one actuator required to raise the wing (which must be repositioned high).

MATV ACTUATOR SYSTEM

The actuators which operate the engine thrust vectoring system are an integral part of the propulsion system; and, the supply technology is subject to that used by the engine for inlet and compressor guide vane control.

"Creativity is inventing, experimenting, growing, taking risks, breaking rules, making mistakes, and having fun."
Mary Lou Cook