The CAB Crash Report of the Phoenix

Gary Fisk passed along a copy of an article from the January 30, 1967, issue of Aviation Week and Space Technology. This article contains the verbatim accident report and is presented here in its entirety.

(Civil Aeronautics Board has completed its investigation of the crash of Phoenix P-1 N-93082 [S], an experimental aircraft built for a motion picture sequence. The crash near Winterhaven, Calif., July 8, 1965, killed the pilot, Paul Mantz, 61, who had a total of 25,100 hr. flying time, three of them in the P-1, and injured a passenger [AW&ST Jan. 16, p. 111]. The CAB report follows.)

Probable cause:
Overload failure of the fuselage structure caused by the resultant induced forces of pitchdown corrective loads and a rigid landing gear structure during an relatively hard, inadvertent touchdown.
Impaired efficiency and judgment of the pilot caused by the consumption of alcohol.

A motion picture company, making a movie about the crash of a C-82 twin-engine twin-boom aircraft in the Sahara Desert, contracted with the California aviation company to build and fly N-93082, an experimental aircraft. The aircraft was to represent a plane whcih the surviviors of the crashed C-82 constructed from the wreckage and flew to safety. The filming site was at a desert location 17 mi. west of Winterhaven, Calif., and the aircraft was operated from the Yuma, Ariz., Airport about 19 mi. from the camera site.

About 0530 PST July 8, 1965, the aircraft was preflighted in preparation for the film sequence to depict the takeoff phase of the movie flight, and at 0625, the pilot with a stunt man as passenger, departed Yuma in clear weather.

Plans for the takeoff sequence called for the pilot to make a very low pass over unprepared desert area about 150 ft. north of and parallel to an east-west oriented line of cameras. Piano wire “cats whisters” attached to the skids were intended to agitate the sandy surface and obscure the fact that the skids were not touching the ground. The desired course was designated by flag markers, and after a short run the pilot was to make a slow and “laborious” climb The pilot said if the wheels actually did touch the ground the would do so only lightly, and if he felt them touch he would bein and immediate takeoff.

The pilot’s first two passes over the flight course were too high, and he flew the third pass a a lower altitude and slower airspeed. As he approached the cameras he was advised the third pass “looked good,” and it was continued. Shortly thereafter, the aircraft touched down relatively hard and in a level flight attitude about 200 ft. northeast of the eastern-most camera. After a roll of about 24 ft. the aircraft struck a small rise of soft sand which caused it to bounce about 3 ft. above the ground. At this time the wood-fabricated aft section of the fuselage was observed to separate from the metal forward section at the two top longeron wood-to-steel longeron attachment fittings. The main wheels touched down a second time shortly thereafter, and the aircraft rolled an additonal 117 ft. before it nosed down, cartwheeled one and one-half times and came to rest with the center fuselage section inverted. The pilot was fatally injured and the passenger received serious injuries. Fire did not occur.

Investigation revealed that critical balance and control force problems were encountered during the flight testing of N-93082. The pitchdown tendency was so severe initially that takeoff speed could not be obtained, and pitchdown control forces were so high the pilot could not remove his hand from the control stick during the initial flight. To compensate for these condtions, aerodynamic down loads on the horizontal stabilizer were increased by elevating the stabilizer rear spar 2 1/4 in. and installing 60 lb. of lead ballast inside the fuselage near the tailwheel. The pilot’s control stick was lengthened to increase leverage, and a bungee was installed to lighten the heavy forward stick loads. Also due to aerodynamic problems which caused a damaging hard landing, five life-sized human dummies installed on the upper wing had to be replaced with silhouettes. Following these modifications, the pilot reported that the aircraft flew satisfactorily. He had already decided not to make any flights in the aircraft after 0900 because of the increase in temperature and associated density altitude in the area after that time.

Examination of the right landing gear revealed evidence of the previous hard landing damage. The landing gear was designed with rigid struts and in a manner which transmitted landing loads to the fuselage, essentially undampened. At the time repairs were made after the hard landing, a hard landing inspection was made.

This failed to disclose evidence of damage other than that to the right landing gear; however, a photograph of the aircraft after the hard landing indcident indicates external paint chipping at the point where the center and aft fuselage are joined.

Examinations by aeronautical and aerospace engineers of the steel-to-wood fuselage longeron fittings, where the failure occurred, showed the design and fabrication of the fittings were in accordance with good aeronautical engineering practice. They concluded that the wood longerons failed in tension due to overloads. The 60-lb. lead weight in the tail section was concluded to have contributed directly to the overload, as did the drag force transmitted to the fuselage by the landing gear when the wheels struck the rise of soft sand. The previous hard landing was considered to have possibly contributed to the failure.

Post-mortem examination of the pilot disclosed a blood alcohol value of 0.13 g/100ml. This value is within the excitement range of alcoholic influence and is considered a sufficient amount to cause impairment of a person’s judgment and physical efficiency.