1972 Puerto Rico DC-7 crash

Causes

The NTSB concluded that after a failure of one engine the plane had inadequate power to maintain altitude during a turn (suggesting that the pilot could not dump fuel fast enough to achieve a weight-to-power ratio that allowed level flight). After a few miles, the plane flew into the ocean on a moonless night. The lack of a horizon possibly prevented the pilot from realizing the altitude loss from only 100 feet over the ocean, which would have indicated a need to prepare for a water landing with reduced engine power on splashdown (the engines appear to have been at full power, and fuselage damage indicated an aircraft at higher speed).

An unexplored scenario is that, following an engine loss, the pilot began fuel dumping to lighten the aircraft. The prop wash dispersed the fuel, and given the low elevation, formed a thermobaric weapon that was ignited by the burning engine. The resulting air burst destroyed the aircraft. The DC-7 contained fuel-dumping facilities. A hazard of fuel dumping is ignition of the fuel, and precautions are taken to eliminate all sources of ignition, and also to prevent turbulence that mixes the fuel with air. Aircraft do not typically explode on impact, and in this case the plane would have been more or less in level controlled flight into the water. An air burst explains the explosion heard after an engine fire was seen, as well as the heavy destruction of the fuselage.

A scenario considered by investigators but later dismissed involved a load shift on turning, which careened the plane into a wing strike with water, cartwheeling the plane along the surface. Two engines were found several hundred feet directly ahead of the wing, indicating a level entry into the water.

The cause of the crash could not be determined precisely because of the difficulties encountered while attempting to recover the wreckage. Probable causes were attributed to lean detonation, poor maintenance, excessive wear in engine components, engine damage from a previous taxiing accident that was not repaired, an uncertified co-pilot, an uncertified flight engineer, a 4,000-pound fuel overload and inadequate crew preparation in correcting these issues.

Complete power loss—complete engine failure/flameout - 1 engine (No. 2)

Partial power loss—partial loss of power - 1 engine (No. 3) (presumably because of a lack of adequate power for three engines)

Power plant (failed because of engine damage from sudden stoppage during a taxiway accident on December 2, 1972)

engine structure: No. 2 master and connecting rods

engine structure: No. 2 cylinder assembly

engine structure: No. 2 piston, piston rings

Miscellaneous acts and conditions, No. 3 excessive-wear/play (unable to develop full power)

Personnel: inadequate maintenance, servicing and inspection

Pilot: inadequate pre-flight preparation and planning

Operational supervisory personnel: deficiency, company-maintained equipment, services, regulation

Improperly loaded aircraft weight and/or center of gravity (over maximum weight by 4,193 lb)

Aircraft contact with the water

Flight engineer unqualified (later court proceedings found there was no evidence that Matias was acting as flight engineer, despite sitting in the flight engineer's seat)