NTSB Identification: FTW94FA082.
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Accident occurred Thursday, February 10, 1994 in SAN ANTONIO, TX
Probable Cause Approval Date: 01/11/1995
Aircraft: CESSNA 421C, registration: N741CA
Injuries: 2 Fatal,1 Serious.

NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.

SHORTLY AFTER TAKEOFF, THE PILOT REPORTED HE HAD 'A PROBLEM' AND NEEDED TO RETURN IMMEDIATELY. WITNESSES OBSERVED DARK BLACK SMOKE COMING FROM BOTH ENGINES. THE AIRPLANE COLLIDED WITH A TREE 1/2-MILE NORTHEAST OF THE RUNWAY THRESHOLD. ANALYSIS OF FUEL SAMPLES REVEALED THE PRESENCE OF APPROXIMATELY 50% JET FUEL. THE RIGHT PROPELLER WAS FOUND FEATHERED AND ENGINE DISASSEMBLY REVEALED A HOLE BURNED IN THE RIGHT ENGINE NUMBER 5 PISTON. LEFT ENGINE DISASSEMBLY REVEALED PISTON EDGES ERODED DOWN TO THE FIRST COMPRESSION RING. FUEL FILLER RESTRICTORS HAD BEEN INSTALLED IN THE AIRPLANE'S FUEL TANKS, BUT THE FUEL TRUCK DID NOT HAVE THE RESTRICTIVE MATING NOZZLE. THE FUEL TRUCK WAS OWNED BY THE FUEL VENDER AND LEASED TO THE FBO.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

IMPROPER SERVICING OF THE AIRPLANE WITH JET FUEL, WHICH RESULTED IN PREIGNITION AND/OR DETONATION AND SUBSEQUENT FAILURE OF PISTONS IN BOTH ENGINES. A FACTOR RELATED TO THE ACCIDENT WAS: THE LACK OF A RESTRICTIVE MATING NOZZLE ON THE REFUELING TRUCK.

Full narrative available

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