6 Unlimited Class Specifications
The following rules and specifications are for the Unlimited Class. All Common Rules apply as appropriate. The dimensions of Unlimited Class aircraft are based on the current USRA Aircraft Specification Sheets and the Unlimited Class Rules that follow.
6.2.1 All entries must be a scale representation of a full size aircraft that qualified to race in the Unlimited Class during any year at the Reno National Championship Air Races or other scheduled Unlimited races such as the Phoenix 500. (Excludes aircraft which must race in the Experimental Class).
6.2.2 Aircraft model minimums are specified in the USRA Aircraft Specification Sheets for each type of aircraft. Aircraft Specification Sheets are available from the USRA.
6.2.3 Minimum wingspan for single engine aircraft is 100 inches. (Individual aircraft are sized by specific type via Aircraft Specification Sheets).
6.2.4 Minimum wingspan for twin-engine aircraft is 112 inches (P-38 Lightning and F7F Tigercat) and 122 inches (A-26 Invader).
6.2.5 NOTE: New aircraft that qualify at Reno or other events must be submitted to the USRA for approval and development of specifications prior to racing.
6.3.1 Minimum aircraft weight is 25 lbs. (dry). Maximum aircraft weight is 55 lbs. (wet).
6.3.2 Aircraft weight may be verified at any time during a race.
6.4 Engine Specifications
6.4.1 Aircraft must be propeller driven with piston or rotary engines.
6.4.2 Engine weight on single engine aircraft may not exceed 14 lbs. Twin engine aircraft engines may not exceed 9.5 lbs. per engine. Engine weight is measured with the engine out of the aircraft in a "ready to race" mode, i.e. if you need the item to race, it must be included in the engine weight. Engine weight does not include ignition modules, batteries, wires, exhaust system, propeller, spinner, spinner back plate or prop nut. A propeller shaft extension is included, if used as part of the engine, is included in engine weight.
6.4.3 Engines must be neatly cowled where possible with no more than 50% of the cylinder head length projecting outside the cowl (measured from the centerline of the output shaft to the top of the cylinder head).
6.5 Exhaust Systems
6.5.1 Exhaust system components (headers, mufflers, tuned pipes, etc.) may not protrude from the airframe more than 30% of their total length. If the exhaust system is not greater than 8 inches, any or all of it may protrude or be exposed.
6.6 Landing Gear
6.6.1 All aircraft must use scale-like retractable or fixed main landing gear as appropriate to the aircraft modeled.
6.6.2 Landing gear must be of sufficient size and strength to permit takeoff, landing and taxi in a reliable manner.
6.6.3 Tail wheels are required to be steerable, but do not have to be retractable. Tail wheels should be installed in the scale location, but may be relocated to another reasonable location on the fuselage for ground handling and safety purposes only.
6.7 Airfoils and Planform
6.7.1 Wing and tail group airfoils suitable for model aircraft may be used. Wing and tail group planforms should follow scale planform, chord, area, etc., of the full size subject when scaled and/or as specified in the USRA Aircraft Specification Sheets.
6.7.2 Control surface dimensions may vary as long as the aircraft's outline is not affected.
6.7.3 Wingspan to fuselage ratio may not vary by more than 1 inch of wingspan and no less than the minimum for the scaled aircraft.