Douglas DC-4 accident at US, 23 Jun 1969

Accident narrative

On June 23, 1969, at approximately 1542 e.d.t., Compania Dominicana de Aviacion Flight 401, a Douglas DC-4 Carvair ATL. 98 (registration HI-168), crashed shortly after takeoff from Miami International Airport. The aircraft struck power lines and buildings about one mile from the airport, coming to rest in an auto body shop. The aircraft was destroyed by impact and fire. All four occupants of the aircraft and six people on the ground were fatally injured, and 12 others on the ground received nonfatal injuries.

**The flight** Flight 401 was a scheduled cargo flight from Miami, Florida, to Santo Domingo, Dominican Republic. Aboard were the captain, first officer, a flight engineer, and a nonrevenue Dominican Republic military pilot. The captain had accumulated 13,736 pilot hours, with approximately 500 in the DC-4. The first officer had 2,333 hours, with 476 in the DC-4. Although a flight engineer is not required on the Carvair, one was assigned to the flight to assist the crew.

The flight was originally scheduled to depart on June 22, but the captain cancelled it to avoid arriving in Santo Domingo after 2000, which was contrary to company policy. On the morning of June 23, the aircraft was loaded with 15,733 pounds of cargo. The flight departed the ramp at 1316 but returned shortly after due to a high oil pressure indication (135 p.s.i.) on the No. 4 engine. Mechanics adjusted the oil pressure relief valve, and the crew reported the pressure was then within satisfactory limits.

**The accident sequence** At 1530, the flight was cleared to taxi, and at 1542:05, it was cleared for takeoff on Runway 12. During the takeoff run, witnesses observed black puffs of smoke coming from the right side of the aircraft, in the vicinity of the No. 4 engine.

Shortly after liftoff, the No. 4 propeller was feathered. As the aircraft passed the end of the runway, heavy white smoke began trailing from the No. 2 engine. The local controller advised the flight of the smoke from the No. 2 engine and cleared them to land on any runway. The flight acknowledged. The copilot radioed that they were going to land on Runway 9 Right, and the tower cleared them for a straight-in approach. This was the final transmission.

Witnesses observed the aircraft climb to a maximum altitude of approximately 300 feet with the landing gear and flaps up. The No. 4 propeller remained feathered, while the No. 2 engine windmilled, emitting black and then heavy white smoke. The aircraft turned eastward, then northward, and finally began a gradual left turn back toward the airport. As the turn continued, the aircraft steadily lost altitude until it struck buildings on N.W. 36th Street.

**What the investigation found** The aircraft was destroyed by impact and the ensuing ground fire. Examination of the flight controls, hydraulic systems, and the Nos. 1 and 3 engines revealed no evidence of pre-impact failure or malfunction.

The No. 2 engine sustained a massive failure of the internal operating components of the front row cylinders. The Nos. 6 and 8 cylinders had separated from the crankcase prior to impact. A small area of fatigue was found on the broken No. 6 master rod. The Board considered that the failure of the No. 6 master rod was most probably the initiating factor in the engine's disintegration, but the extensive physical destruction precluded a positive definition of the initial failure.

The No. 4 engine was badly burned, but examinable internal components showed no indications of operating distress. However, when the No. 4 engine's oil pressure relief valve was functionally tested after the accident, it produced oil pressure indications consistently below recommended operating limits. The Board noted it was conceivable that the oil pressure dropped during the takeoff run, activating a warning light. Because the takeoff had already been delayed by No. 4 engine oil pressure problems, the Board believed there was little doubt the crew's attention was focused on this engine when the No. 2 engine began its failure sequence.

The investigation determined the aircraft's actual gross takeoff weight was 69,710 pounds. This exceeded the maximum allowable takeoff weight of 69,200 pounds specified in the company flight manual for the existing altitude and temperature. The Board noted discrepancies in the fuel loading records, suggesting the captain had requested extra fuel to correct an asymmetrical load, though the exact distribution remained unknown.

Performance data showed that at a gross weight of 69,710 pounds with two engines inoperative, the Carvair cannot maintain level flight. Even using maximum continuous power on the two remaining engines, a descent rate of 170 feet per minute could be expected, and this performance would be further deteriorated by the drag of the windmilling No. 2 propeller and the bank angle during the turn. To maintain level flight with two engines out, the aircraft's weight would have to be 58,400 pounds. Dumping fuel to reach this weight would have taken approximately five minutes, an action the crew probably did not consider due to the risk of igniting the dumped fuel on the smoking No. 2 engine.

The Board reviewed the captain's available training records from 1963 and 1964, which indicated weakness in the knowledge and execution of emergency procedures. The Board suggested that the crew's remedial action promptly compounded the emergency, noting that the No. 4 propeller was feathered while the failing No. 2 engine was left windmilling.

**Probable cause** The Safety Board determined that the probable cause of this accident was "the confused action on the part of the crew while attempting to cope with the catastrophic failure of an engine during takeoff."