Air Florida Flight 90 - Delays, Poor Decisions, Crash

Delays, Poor Decisions, Crash

The plane had trouble leaving the gate when the ground services tow motor could not get traction on the ice. For approximately 30 to 90 seconds, the crew attempted to back away from the gate using the reverse thrust of the engines, which proved futile. Boeing operations bulletins had warned against using reverse thrust in those kinds of conditions.

Eventually, a tug ground unit properly equipped with snow chains was used to push the aircraft back from the gate. After leaving the gate, the aircraft waited in a taxi line with many other aircraft for 49 minutes before reaching the takeoff runway. The pilot apparently decided not to return to the gate for reapplication of deicing, fearing that the flight's departure would be even further delayed. More snow and ice accumulated on the wings during that period, and the crew was aware of that fact when they decided to make the takeoff. Heavy snow was falling during their takeoff roll at 3:59 p.m. EST.

Even though the temperature was freezing and it was snowing, the crew did not activate the engine anti-ice system. Analysis of the cockpit voice recorder (CVR) determined that, during the departure checklist, the copilot announced and the pilot confirmed that the plane's own engine anti-icing system was turned off. This system uses heat from the engines to prevent sensors from freezing, ensuring accurate readings.

Adding to the plane's troubles was the pilots' decision to maneuver closely behind a DC-9 that was taxiing just ahead of their aircraft prior to takeoff, due to their mistaken belief that the warmth from the DC-9's engines would melt the snow and ice that had accumulated on Flight 90's wings. This action — which went specifically against flight manual recommendations for an icing situation — actually contributed to additional icing on the 737. By sitting behind the preceding aircraft, the exhaust gases melted the snow on the wings. During takeoff, instead of falling off the plane, this slush mixture then froze on the wings' leading edges and the engine inlet nose cone.

Neither pilot had much experience flying in snowy, cold weather. The captain had made only eight takeoffs and landings in snowy conditions on the 737, and the copilot had flown in snow only twice.

As it turned out, the failure to operate the plane's engine anti-icing system caused exactly what could be expected to happen: the engine pressure ratio (EPR) thrust indicators provided false high readings. While the pilots thought they had throttled up to the correct takeoff EPR of 2.04, the actual EPR was only 1.70. The aircraft traveled almost half a mile (800 m) further down the runway than is customary before liftoff was accomplished. Survivors of the crash indicated the trip over the runway was extremely rough, with one survivor saying that he feared that they would not get airborne and would "fall off the end of the runway".

As the takeoff roll began, the First Officer noted several times to the Captain that the instrument panel readings he was seeing did not seem to reflect reality (he was referring to the fact that the plane did not appear to have developed as much power as it needed for takeoff, despite the instruments indicating otherwise). The captain dismissed these concerns and let the takeoff proceed. Investigators later determined that there was plenty of time and space on the runway for the Captain to have aborted the takeoff, and criticized his refusal to listen to his first officer, who was correct that the instrument panel readings were wrong. The pilot was told not to delay because another aircraft was 2.5 miles out (4 km) on final approach to the same runway. The following is a transcript of Flight 90's cockpit voice recorder during the plane's acceleration down the runway. (CAM-1 is the captain, CAM-2 is the first officer)

15:59:32 CAM-1 Okay, your throttles.

15:59:35

15:59:49 CAM-1 Holler if you need the wipers.

15:59:51 CAM-1 It's spooled. Real cold, real cold.

15:59:58 CAM-2 God, look at that thing. That don't seem right, does it? Uh, that's not right.

16:00:09 CAM-1 Yes it is, there's eighty.

16:00:10 CAM-2 Naw, I don't think that's right. Ah, maybe it is.

16:00:21 CAM-1 Hundred and twenty.

16:00:23 CAM-2 I don't know.

16:00:31 CAM-1 Vee-one. Easy, vee-two.

As the plane became briefly airborne, the flight recorder picked up the following from the cockpit, with the sound of the stick-shaker (an instrument that warns that the plane is in danger of stalling) in the background:

16:00:39

16:00:41 TWR Palm 90 contact departure control.

16:00:45 CAM-1 Forward, forward, easy. We only want five hundred.

16:00:48 CAM-1 Come on forward....forward, just barely climb.

16:00:59 CAM-1 Stalling, we're falling!

16:01:00 CAM-2 This is it. We're going down, Larry....

16:01:01 CAM-1 I know it!

16:01:01

Although the 737 did manage to become airborne, it attained a maximum altitude of just 352 feet (107 m) before it began losing altitude. Recorders later indicated that the aircraft was airborne for just 30 seconds. At 4:01 p.m. EST it crashed into the 14th Street Bridge across the Potomac River, 0.75 nautical miles (1,390 m) from the end of the runway. The plane hit six cars and a truck on the bridge, and tore away 97 feet (30 m) of the bridge's rail and 41 feet (12 m) of the bridge's wall. The wrecked aircraft then plunged into the freezing Potomac River. It fell between two of the three spans of the bridge, between the I-395 northbound span (the Rochambeau Bridge) and the HOV north- and southbound spans, about 200 feet (61 m) offshore. All but the tail section quickly became submerged.

Of the people on board the aircraft:

• Four of the five crew members (including both pilots) died
• One crew member was seriously injured
• 70 of the 74 passengers died.

Of the motorists on the bridge involved:

• 4 sustained fatal injuries
• 1 sustained serious injuries
• 3 sustained minor injuries

Clinging to the tail section of the broken airliner with six passengers in the ice-choked Potomac River, flight attendant Kelly Duncan inflated the only flotation device they could find and passed it to one of the more severely injured passengers, Nikki Felch. Joe Stiley, assisting fellow survivor Priscilla Tirado, was trying to tow her to shore when the United States Park Police helicopter assisting in the rescue returned to try to pull them to safety.