McDonnell Douglas MD-82 accident at Flushing, New York, 2 Mar 1994

Accident narrative

On March 2, 1994, at about 1759 eastern standard time, Continental Airlines flight 795, a McDonnell Douglas MD-82, overran runway 13 following a rejected takeoff at LaGuardia Airport in Flushing, New York. The airplane continued beyond the takeoff end of the runway and came to rest balanced on top of a dike, with its nose pitched downward onto a tidal mud flat of Flushing Bay. There were 110 passengers, two flightcrew members, and four flight attendants aboard. There were no fatalities. Twenty-nine passengers sustained minor injuries during the evacuation, and the first officer sustained a minor back injury.

### The flight

Flight 795 was the return leg of a scheduled trip from Denver Stapleton International Airport to LaGuardia, with a planned return to Denver. The captain, 57, had about 23,000 total pilot hours, with 6,000 hours in the MD-80/82. The first officer, 47, had about 16,600 total pilot hours, with 2,400 hours in MD-80 series airplanes.

### The sequence of events

The airplane was deiced at the gate between 1712 and 1724 to remove light snow. The first officer called for taxi at 1731. Weather conditions included freezing temperatures, light snow, and fog, and the snowfall began to increase as the flight taxied out. At 1753, the captain asked the first officer to check the wings for icing. The first officer examined the wings from the cabin, returned to the cockpit, and stated, "Looks okay to me."

The flightcrew started the right engine at 1756:52. At 1757:02, LaGuardia Tower cleared the flight to taxi into position and hold on runway 13. The taxiways were slippery, and other departing flights reported residual snow cover on the runway. At 1757:32, the captain gave a rejected takeoff briefing, stating that if he called an abort, he would take control of the airplane and apply reverse thrust while the first officer deployed the spoilers.

Flight 795 received takeoff clearance at 1758:36. The first officer, who was at the controls, advanced the throttles and called "autothrottles on." The captain crosschecked the engine instruments to confirm takeoff power was set. The brakes were released at 1758:48, and the airplane began to accelerate.

The captain later stated that at 60 knots, the indicated airspeed appeared to stop increasing. He said the airspeed indicator increased once from 60 to 80 knots, then returned to 60 knots. He noted that the first officer's airspeed indicator also read about 60 knots. The captain stated he saw a red light flicker on the instrument panel and called "Abort" at 1759:23.

During the rejected takeoff, the captain applied maximum braking and maximum reverse thrust. He stated the brakes were ineffective and the airplane continued to slide down the runway. The airplane departed the end of the runway, and the first sounds of impact with the dike were recorded on the cockpit voice recorder (CVR) at 1759:46.

After the airplane came to rest, the captain called for the rejected takeoff and evacuation checklists. He made a public address announcement stating, "we see no fire be careful... go to the rear of the airplane... after you exit the aircraft." Some passengers and flight attendants found the message garbled or confusing. A flight attendant in the rear deployed the tailcone slide, but because the tail was high off the ground, the slide did not reach the surface. She directed passengers to move forward. Most passengers exited over the wings or through the forward doors. The emergency cabin lights went out shortly after the airplane stopped.

A Port Authority police lieutenant arrived about one and a half minutes after the alert. He banged on the cockpit window and informed the flightcrew that the right engine was still running. The crew then pulled the fire handles, shutting down the engines, and turned off the battery.

### What the investigation found

The airplane sustained substantial damage. The nose landing gear was fractured and forced backward into the forward electronic equipment bay, and the fuselage was buckled. The thrust reversers were found in the stowed position.

Investigators examined the airplane's pitot-static system, which provides airspeed indications. The pitot probes and static ports were unobstructed, and the system passed leakdown tests. However, the METER SEL & HEAT switch, which controls electrical heat to the pitot tubes, static ports, and ram air temperature (RAT) probe to prevent ice blockage, was found in the OFF position detent.

Postaccident testing demonstrated that the heating elements were fully functional when the switch was turned on. Furthermore, tests of the RAT probe confirmed it had not heated up after the nose gear collapsed, which it automatically would have done if the system had been energized. The Board concluded that the pitot tube heating elements were not energized during the takeoff roll because the selector switch was improperly positioned in the OFF detent. This lack of heat allowed ice and/or snow to block the pitot inlets, causing the system pressure to bleed off through the drain holes and resulting in the erroneous airspeed indications observed by the crew.

The Board found that the flightcrew deviated from standard operating procedures during their checklist execution. The CVR recorded the crew delaying the start of the second engine, failing to use the Delayed Engine Start checklist, missing items on other checklists, and failing to call checklists complete. While taxiing into position, the first officer called out checklist items without the captain's request and without using the required challenge and response format. The Board believed the pilots failed to conduct a prestart checklist properly, missing the step to turn on the pitot heat, and subsequently failed to observe an illuminated warning light on the annunciator panel indicating the heat was off. The 30-minute CVR did not capture the prestart checklist phase, limiting the available audio record.

An airplane performance study determined that the airplane accelerated normally during the takeoff roll. The actual indicated airspeed reached a computed maximum of 145.5 knots. The captain initiated the rejected takeoff 34 seconds after the start of the roll, at a computed airspeed of 143 knots, which was 5 knots above the V1 decision speed of 138 knots. The airplane departed the runway at 53 knots and struck the dike at 39 knots.

Calculations showed that despite the reduced braking friction on the snow-covered runway, the airplane should have stopped within the confines of the runway if the rejected takeoff had been initiated at or before V1. The Board noted that the captain's delayed response to the abnormal airspeed indications allowed the airplane to accelerate beyond a safe stopping speed.

### Probable cause

The National Transportation Safety Board determined that the probable causes of this accident were the failure of the flightcrew to comply with checklist procedures to turn on an operable pitot/static heat system, resulting in ice and/or snow blockage of the pitot tubes that produced erroneous airspeed indications, and the flightcrew's untimely response to anomalous airspeed indications with the consequent rejection of takeoff at an actual speed of 5 knots above V1.