Customer: Dan Mortensen / AmsOil
Type: single-seat, staggered tandem-wing racer
Program: 1981 Reno Air Races
Significant date: 1981
In late 1979 Burt designed an aircraft for Dan Mortensen to fit the specifications for racing biplanes. In 1980 Mortensen received sponsorship from AmsOil to build and race his prototype. The aircraft (N301LS), designated the Model 68 Biplane Racer and built by a team in Sacramento, California, was completed in August 1981.
The Model 68 was very similar to the RAF Model 54 Quickie, using the reversed stagger tandem wing concept with wheels at canard tips. It used some previously unflown airfoils, which were shown by test to be delivering over 60% chord natural laminar flow (the NLF was attained even within the prop wash). Of particular note was the use of the small horizontal T-tail. That tail was an all-flying type and was geared to operate with the canard elevator control system. This is the first use of a Horizontal tail on Rutan designed aircraft. Its purpose was to force the forward elevator to the proper positions to optimize canard airfoil camber for both the 250 mph straight aways and the 4g turns. Also, the horizontal tail fine tuned the aeroelastic effects to increase pitch stability at very high speeds. Despite the use of carbon fiber in its construction, the Model 68 was a relatively flexible airframe for a 250 mph application. The design parameters for the tail were verified by the flight tests.
The AmsOil Biplane Racer was entered in the 1981 Reno Air Races in September. Although it turned several record-exceeding laps during a heat race, it finished only third in the final race due to several pylon cuts. The pylon cuts were the result of a roll deficiency in the control system. Dan delivered N301LS to Rutan Aircraft Factory in October so they could evaluate it and help him complete its development. Except for the roll deficiency, which was caused by inadequate travel and stiffness of the controls, the Racer proved to be an excellent flying aircraft with good firm flying qualities at its 240 mph racing speed. Its takeoff and landing distances and handling were good. Dan planned to make some improvements in its engine installation and propeller to assure its racing success in the next season.
And a success it was at first. The Amsoil Racer won two National and two World speed records, which it was to hold for quite a while. Yet the aircraft's career was brief. While being flown on June 13, 1983 in Camp Douglas, Wisconsin, the experimental aircraft lost a blade of its propeller during cruise flight. The propeller had been modified to obtain more rpm. About 18 inches of one blade separated during cruise at 6,000 ft. with 2,900 rpm at 200 kts. airspeed. The engine remained attached to the aircraft by a 3/16-inch cable wrapped around it and secured to the fire wall (one of Mortensen's modifications). The aircraft was damaged in the forced landing.
The Amsoil Racer was hardly rebuilt when on September 17, took part in a Pylon Air Race during the Reno National Air Races in Sun Valley, Nevada. Unfortunately, the aircraft were approaching the first pylon in a steep left bank when, according to the pilot, another aircraft pulled in front of him. While attempting to avoid a collision at about 200 mph, and with only 35 feet of altitude, the aircraft stalled and crashed hard at 200mph, the engine, wings etc. were violently ripped off and the plane destroyed, yet the cockpit portion remained remarkably intact.
All observers thought at first that Dan Mortenson was gravely hurt after such a crash, but were pleasantly suprised when they saw him stand up, climb out and walk away uininjured, merely stunned and slightly bruised. Was it the design that saved the pilot, or just the instances of that particular crash? Perhaps both? (the cockpit was designed to withstand 22 G's, but some crashes can easily exceed that limit). The AMSoil wing was supposed to flex as it banked and change the angle of attack and reduce drag making it hold its speed around the turns, but in reality it slowed it down in the turns and eventualy caused a high speed stall destroying the plane.
Luckily Mortensen was unhurt, but the Amsoil Racer, briefly one of America's true aviation glories, was no more, and it soon vanished into oblivion. As for the 'Amsoil Racer', it was eventually put back together again after the crash and at was still hanging above a bar in the MGM Grand hotel in Reno Nevada a few years ago.
Population: 1 [N301LS]