Douglas DC-4 accident at Miami, Florida, 14 Sept 1951

Accident narrative

On September 14, 1951, Eastern Air Lines Flight 635W, a Douglas DC-4, suffered a landing gear retraction while rolling out after a normal touchdown at Miami International Airport in Florida. The aircraft settled onto its fuselage and slid to a stop. None of the 20 adult passengers, one infant, or three crew members were injured, though the aircraft was substantially damaged.

**The flight**

Flight 635W originated in Boston, Massachusetts, on September 13, with a final destination of Miami. Following a routine aircraft and crew change in New York, the flight was operated by Captain A. C. McDonough, Copilot J. F. Reubert, and Flight Attendant R. K. Quinn. Captain McDonough had approximately 12,872 flying hours, including 2,145 in DC-4 equipment, while Copilot Reubert had 2,451 hours, with 336 in the DC-4.

The aircraft departed Jacksonville, Florida, at a gross takeoff weight of 54,671 pounds, well within the maximum allowable limit of 65,705 pounds. The captain and copilot alternated flying duties. Copilot Reubert flew the final segment from the vicinity of Vero Beach to Miami, while Captain McDonough occupied the left seat and performed copilot duties.

**The approach and landing**

Nearing Fort Lauderdale, the crew cancelled their Instrument Flight Rules flight plan and proceeded under Visual Flight Rules. The weather at Miami was clear, with an unlimited ceiling, 12 miles of visibility, and a three-mile-per-hour north-northwest wind.

The flight was cleared to land on Miami's Runway 9L. At 1,200 feet, the crew completed the "in range" check and lowered the flaps to 15 degrees. On the downwind leg at 800 feet, they completed the "before landing" check and extended the flaps to 30 degrees, leaving the landing gear for the final approach.

Turning on final, the copilot called for the landing gear. The captain stated he placed the gear lever in the full down position, observed the red warning light go out and the three green indicator lights come on, and verified normal hydraulic pressure. Because they had been flying in darkness, the warning light dimming switch was set to dim; the captain stated he moved it to bright and again observed the three green lights. He called out, "Gear down and locked, three green lights, mixtures rich, you are cleared to land."

Full flaps were extended at 400 feet, and the aircraft made a normal touchdown on its main landing gear wheels approximately 200 feet past the approach end of the runway. After traveling a considerable distance, the landing gear was observed to retract. The DC-4 settled onto its fuselage bottom and slid. A flash fire in the number three engine nacelle was quickly extinguished by the captain using a portable carbon dioxide bottle and by airport fire equipment. The passengers evacuated in an orderly manner.

**What the investigation found**

Investigators found the aircraft resting near the center of the 7,364-foot runway, 3,290 feet from the approach end. The first marks on the runway were gouges from the inboard propellers, beginning 1,856 feet from the threshold. Marks from the outboard propellers followed 25 feet later, and fuselage contact marks began nine feet beyond that. The landing gear was found in an almost fully retracted position.

In the cockpit, the landing gear lever was found in the down position with the solenoid safety pin in the safe lock position. The flap lever and indicator were full down. Hydraulic and emergency brake pressures registered normally.

When the aircraft was raised, the nose gear fell free and locked. The main landing gear retract struts had bent actuating cylinder rods, which had retracted about five inches into their cylinders. When the hydraulic system was connected to an external power source, the nose gear operated normally. The main gear rods extended and retracted normally until stopped by their bent portions. After the damaged rods and drag links were replaced with new parts, all three landing gears functioned normally under pressure. The hydraulic system was clear, the pumps functioned normally, and the warning horn operated as designed.

The DC-4 landing gear system is designed so that the weight of the aircraft holds the main gear in the extended and locked position. Furthermore, when the right main shock strut is compressed by the aircraft's weight, a safety switch engages a latch that locks the landing gear control lever in the down position.

The crew stated that the gear lever was placed down prior to landing and was not moved again. However, the Board noted that for the gear to retract on its own under these conditions, numerous simultaneous malfunctions would have to occur. Because the crew observed the green warning lights and the system functioned properly during post-accident tests, the Board assumed the gear was down and locked before touchdown.

The Board concluded it was probable that the landing gear control lever was inadvertently moved upward instead of the flap control lever after landing. This must have occurred while wing lift was still present and there was insufficient weight on the landing gear strut to actuate the safety latch, a conclusion the Board found substantiated by the partially retracted actuating cylinder rods.

**Probable cause**

The Civil Aeronautics Board determined that "the probable cause of this accident was the inadvertent moving of the landing gear control lever upward during the landing roll, causing the landing gear to retract."