Thursday, March 4, 2010

MX Aircraft

Well, it has been an interesting week or so at the MX Aircraft factory, North Wilkesboro, North Carolina USA. The company builds two aircraft, the two-seat MX-2 and the single-seat MXS. The race aircraft, called an MXS-R, is essentially a cosmetic development of the MXS.

The MX2 came first, derived from the Giles G-202, in the early noughties. Then the MXS came along by eliminating the front seat and shortening the fuselage. The power plant used in both models is the parallel-valve IO-540 Lycoming. MXS-R differences that can be seen are a revised cowling with circular inlets. Some also have shortened ailerons by 15-20 inches inboard to decrease roll sensitivity, drag, and improve the lift capability of the wing. Many individual smaller mods can be incorporated at the request of the customer, and as only 10 MXS's have been built thus far, they all tend to be a little different in detail. Once the aircraft is accepted by the customer they typically undergo further non-structural modification and tuning for racing. The aircraft are registered in the Experimental-Exhibition/Air Racing category, and all have been kept on the US N-registry thus far.

The structure is predominantly carbon/epoxy pre-preg vacuum bagged and oven cured. Wet-layup has been almost eliminated, as has e-glass panels, particularly on the race planes. Moulded sections are bonded together with structural adhesive and hard points incorporated for the bolted connections. The design's ultimate load is 24g, and apparently 15g has been experienced in flight! MXS-R VNE=250KTS, VA=180KTS. Continued refinement during construction has resulted in significant weight savings, resulting in MXS-R weights below the RBAR minimum, so teams now have to add ballast.

Obviously the performance of the aircraft is outstanding, but teams are mute when discussing the ultimate figures! S&L speeds in excess of 220KIAS are now common, as are extremely short take-offs. Stall speed is mid-fifties, and 25"MAP/2500rpm yielded ~200KIAS @ 3000ft in Alex McLean's old MXS-R without wheel pants and definitely not in race trim. Controls were powerful while not being unduly sensitive. Roll rate was adequate. The wing was outstanding being very forgiving with no sign of tip-stall despite provocation during rolling circles. Positive snaps were fast and the break rapid at normal speeds. More time would be needed to fully investigate, and exploit, the capabilities of this aircraft.

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