Accident Overview
On April 17, 2015, at 0745 central daylight time, a Cessna 421B airplane, registration N421PK, experienced a loss of engine power and executed a forced landing onto a highway near Diboll, Texas. The airplane sustained substantial damage. The pilot received serious injuries, while the two passengers sustained minor injuries. The flight was operated under 14 CFR Part 91 as a personal flight, with instrument meteorological conditions prevailing and an IFR flight plan filed. The flight departed from Angelina County Airport (LFK) in Lufkin, Texas at 0737, en route to West Houston Airport (IWS) in Houston, Texas.
Pilot and Aircraft Information
The pilot, age 63, held a private pilot certificate with single-engine, multi-engine, and instrument ratings. He reported approximately 3,000 total flight hours, with 500 hours in the accident airplane make and model. The aircraft was a 1975 Cessna 421B, serial number 421B0830, a six-seat, low-wing, retractable landing gear airplane powered by two reciprocating GTSIO-520-H Continental Motors engines (375 horsepower each), each driving a three-blade, full-feathering, constant-speed McCauley propeller. The fuel system included main outboard tip tanks and inboard auxiliary tanks.
Fueling Error
The day before the accident, the pilot requested that the tip tanks be topped off. An FBO employee mistakenly identified the airplane as a similar model that used Jet A fuel and used the Jet A fuel truck. The employee noted that the nozzle on the Jet A truck was small and round, similar to the nozzle on aviation gasoline trucks, due to modifications made for fueling military helicopters. The pilot paid for the fuel and signed a receipt that indicated Jet A fuel was used. Fuel records obtained from LFK confirmed that 53 gallons of Jet A were pumped into the airplane on the day prior to the accident.
On the morning of the accident, the pilot performed a preflight inspection, sampling fuel that appeared blue (like 100LL aviation gasoline) with no water contamination. After a normal engine run-up, the flight departed. During climb out, the airplane experienced a slight vibration and degraded climb performance. At about 2,100 feet above ground level, the left engine sputtered and lost all power, followed by the right engine within 30 seconds. The pilot performed a forced landing, touching down hard in the grassy median of a highway. During the accident sequence, the wings and fuselage were damaged, and the right fuel tank ruptured. The pilot reported a strong smell of Jet A fuel at the scene.
Examination Findings
A postaccident examination of the engines revealed signs of detonation. Cylinders lacked combustion deposits, with scrape marks on cylinder walls and metal particles on piston faces. Spark plugs showed normal wear but heavy dark deposits in electrode areas. No water contamination was found in fuel strainer bowls. Notably, the airplane's fuel tank filler ports were not equipped with restrictors as required by Airworthiness Directive (AD) 87-21-02 R1, despite maintenance records indicating compliance. Two fuel placards near the filler ports read "AVGAS ONLY – grade 100LL" and "Fuel, 100/130 aviation grade min, useable 50 gal."