Boeing 707-131B accident at US, 16 Jan 1974

Accident narrative

About 0135 p.d.t. on January 16, 1974, the nose landing gear of Trans World Airlines Flight 701, a Boeing 707-131B, collapsed upon touchdown after a night visual approach to runway 6R at the Los Angeles International Airport. A postcrash fire destroyed the fuselage. Of the 58 passengers and seven crewmembers on board, eight passengers were injured during the emergency evacuation. There were no fatalities.

### The flight

Flight 701 was a scheduled nonstop flight from John F. Kennedy International Airport in New York. The flight was routine until the Los Angeles area. At 0127, the flightcrew advised approach control that the airport was in sight and the flight was cleared for a visual approach to runway 6R.

An American Airlines flight immediately ahead of Flight 701 reported to the local controller that they had entered a thin stratus layer about 200 feet above the airport, which greatly reduced forward visibility. At 0129, the local controller relayed this to the approach controller, but Flight 701 was not advised of these conditions.

Flight 701 contacted the local controller and was cleared to land. The controller advised that the runway visual range (RVR) for runway 6R was 5,500 feet.

The first officer flew the approach manually by visual reference. The captain stated that at 500 feet, he called out an airspeed of 160 kn and a sink rate of 400 to 1,000 feet per minute, advising the first officer that the aircraft was slightly below the glide slope. The first officer initiated corrective action.

The captain stated that just after crossing the runway threshold, the aircraft entered a patch of shallow ground fog and lost all outside visual reference. The first officer said he was just about to flare the aircraft for landing when they lost visual reference, so he maintained the existing attitude until touchdown. The crew stated that the touchdown felt like a very firm three-point landing, and that the aircraft rolled out of the fog almost immediately.

### What the investigation found

Runway tire marks contradicted the crew's belief that all three landing gears touched down simultaneously, confirming instead that the nose wheel touched down first. The flight data recorder showed that in the nine seconds before touchdown, the aircraft's average rate of descent was 1,400 feet per minute, and the vertical acceleration recorded a 4.60 g load upon touchdown. The Board noted this indicated an unchecked high sink rate and a resultant hard landing, and that the approach should have been discontinued.

The hard landing caused the nose gear to collapse rearward and upward, pushing the passenger cabin floor upward and jamming the cockpit door closed. The flightcrew had to exit via the cockpit side windows and could not assist in the passenger evacuation. Eight passengers were injured jumping, falling, or being pushed from the evacuation slides and wings.

The Board believed the fire in the nose wheel well was ignited by friction generated between the nose wheel tires and the runway surface. The fire was sustained by pressurized hydraulic fluid from two fractured nose wheel steering hydraulic lines. Firefighting personnel arrived six minutes after the accident but were unable to extinguish the fire before it spread to the passenger cabin, partly because the fire's location in the collapsed wheel well prevented them from placing extinguishing agents directly on the source.

The investigation found that the RVR transmissometer for runway 6R was located too far down the runway to measure visibility at the glide slope touchdown point. The fog had moved slowly eastward and reached the transmissometer about three minutes after the accident.

Additionally, the cockpit voice recorder had malfunctioned due to a broken drivebelt on a previous flight. The Board noted that the crew should have detected this failure during their preflight checks.

### Probable cause

The National Transportation Safety Board determined that the probable cause of the accident was "the continuation of a visual approach after the flightcrew lost outside visual reference because of a low cloud and fog encounter."