Accident Overview
On September 15, 2022, at about 1202 Pacific daylight time, a Beech M35 airplane, registration N9876R, was substantially damaged when it was involved in an accident near Henderson, Nevada. The flight instructor and pilot receiving instruction were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 instructional flight.
Flight Details
The flight instructor reported that they planned to fly from their home airport in Camarillo, California, to satisfy an insurance requirement. The airplane was equipped with six fuel tanks: two main, two auxiliary, and two wingtip tanks. The instructor visually checked the main and auxiliary tanks by opening the fuel caps and verified the wingtip tank quantities via window gauges. During preflight, the left main tank (25-gallon capacity) showed 3/4 full, and the right main tank (25-gallon capacity) showed full. Only the main tanks were used during the flight.
According to the instructor, they departed about 1005 and climbed to 7,500 ft mean sea level. About 40 minutes into the flight and 45 minutes before landing, they switched to the right main tank and the digital fuel gauge indicated FULL. About 25 minutes later, the gauge still indicated FULL. The instructor and pilot discussed the abnormality, attributing it to a faulty sensor, but concluded the tank had sufficient fuel to complete the flight. About 15 minutes later, during a straight-in approach to runway 35L, the pilot noticed low altitude, added power, but received no engine response. The pilot informed the instructor while advancing the throttle to full open. The instructor selected the left main tank on the fuel selector to restore power, unsuccessfully, and the airplane continued to descend.
The airplane touched down in dirt, impacted a berm, and came to rest on a road about 0.2 nautical miles south of the runway. Both pilots co-owned the airplane, purchased together in July 2022.
Postaccident Examination
The airplane sustained substantial damage to the fuselage and left wing. A Federal Aviation Administration inspector observed fuel levels about one hour after the accident: the left main tank (25 gallons total) was 1/2 full; the right main tank (25 gallons total) was empty.
An examination of the fuel system found the right main fuel tank bladder had collapsed. No blockages were found in fuel lines, and the right main tank vent was clear. When the right main tank was pressurized, no leaks were observed at the fuel cap. A test of the right main tank fuel quantity measurement system revealed it reported ½ to ¾ full regardless of the float sensor position in the fuel bladder. No visible breaches were observed in the right main tank.
JPI Data
The airplane was equipped with a JPI 930 engine monitoring system. Data from the accident flight showed the airplane departed about 1037 with manifold pressure at 23 inches Hg and engine speed about 2,500 rpm. The right main fuel level indicated 22 gallons at departure and remained between 18 and 22 gallons throughout. The left tank fuel level was about 17 gallons at departure and indicated between 8 and 12 gallons when tanks were switched about 45 minutes before landing. Fuel flow was about 22 gph during cruise from about 1050 to 1141, then decreased to about 17 gph until engine power loss. At 1202:26, fuel flow decreased from about 15 gph to 0 gph, accompanied by a rapid reduction in exhaust gas temperature (EGT) from about 1,200–1,400° F to about 800–1,000° F. Manifold pressure increased to about 25 inches Hg and rpm decreased from 2,500 to 1,800. In the next 30 seconds, EGTs further decreased to about 250° F, manifold pressure increased to about 28 inches Hg, and engine speed decreased to about 1,000 rpm.