United Airlines Flight 173

United Airlines Flight 173

Accident
Date	December 28, 1978
Summary	Fuel exhaustion due to pilot error (lack of situational awareness)
Site	Portland, Oregon 45.5225°N 122.499722°W / 45.5225; -122.499722
Aircraft type	McDonnell-Douglas DC-8-61
Operator	United Airlines
Registration	N8082U
Flight origin	John F. Kennedy International Airport, New York City
Stopover	Stapleton International Airport, Denver, Colorado
Destination	Portland International Airport, Portland, Oregon
Passengers	181
Crew	8
Fatalities	10
Injuries	24
Survivors	179

United Airlines Flight 173 was a scheduled flight from John F. Kennedy International Airport in New York City to Portland International Airport in Portland, Oregon, with a scheduled stop in Denver, Colorado. On December 28, 1978, the aircraft operating the route crashed in a suburban Portland neighborhood near NE 158th Avenue and E Burnside Street after running out of fuel.

Flight History

The flight crew on the day of the accident consisted of Captain Malburn McBroom, First Officer Rodrick Beebe, and Second Officer Forrest Mendenhall. Flight 173 departed from Denver about 14:47 with 189 people on board. The estimated time enroute was 2 hours and 26 minutes. The planned arrival time in Portland was 17:13. According to the automatic flight plan and monitoring system, the total amount of fuel required for the flight to Portland was 31,900 lbs. There was 46,700 lbs. of fuel on board the aircraft when it departed the gate in Denver.

Injuries

Of the crew members, 2 were killed, the flight engineer and a flight attendant, 2 sustained injuries classified by the National Transportation Safety Board (NTSB) as "serious", and 4 sustained injuries classified as "minor/none." Of the passengers, 8 died, 21 had serious injuries, and 152 had minor or no injuries.

Crash investigation and report

The NTSB investigation revealed that when the landing gear was lowered, a loud thump was heard. That unusual sound was accompanied by abnormal vibration and yaw of the aircraft. The right main landing gear retract cylinder assembly had failed due to corrosion, and that allowed the right gear to free fall. Although it was down and locked, the rapid and abnormal free fall of the gear damaged a microswitch so severely that it failed to complete the circuit to the cockpit green light that tells the pilots that gear is down and locked. It was those unusual indicators (loud noise, vibration, yaw, and no green light) which led the captain to abort the landing, so that they would have time to diagnose the problem and prepare the passengers for an emergency landing. While the decision to abort the landing was prudent, the accident occurred because the flight crew became so absorbed with diagnosing the problem that they failed to monitor their fuel state and calculate a time when they needed to return to land or risk fuel starvation.

"The Safety Board believes that this accident exemplifies a recurring problem -- a breakdown in cockpit management and teamwork during a situation involving malfunctions of aircraft systems in flight… Therefore, the Safety Board can only conclude that the flightcrew failed to relate the fuel remaining and the rate of fuel flow to the time and distance from the airport, because their attention was directed almost entirely toward diagnosing the landing gear problem."

The NTSB determined the following probable cause:

"The failure of the captain to monitor properly the aircraft's fuel state and to properly respond to the low fuel state and the crewmember's advisories regarding fuel state. This resulted in fuel exhaustion to all engines. His inattention resulted from preoccupation with a landing gear malfunction and preparations for a possible landing emergency."

The NTSB also determined the following contributing factor:

"The failure of the other two flight crewmembers either to fully comprehend the criticality of the fuel state or to successfully communicate their concern to the captain."

The fuel situation was known to be on their minds of the pilot and crew to some degree. Transcripts of cockpit recordings confirm this. Investigation: United Airlines Flight 173 . Media reports at the time suggested that there was a not-widely-known problem with fuel state gauges on that model aircraft.. The problem was not widely known in part because commercial aircraft are expected to fly with not less than a 45 minute reserve of fuel at all times. The gauge problem is addressed, though obliquely, in one of the safety board's recommendations:

"Issue an Operations Alert Bulletin to have FAA inspectors assure that crew training stresses differences in fuel-quantity measuring instruments and that crews flying with the new system are made aware of the possibility of misinterpretation of gauge readings. (Class II--Priority Action) (A-79-32)"

While the totalizer fuel gauge issue may have contributed to the crew's confusion towards the end of the flight, the NTSB report emphasized that the captain should have never allowed such a situation to develop in the first place.

Aftermath

As a result of this accident, United Airlines instituted the industry's first Crew Resource Management/Cockpit Resource Management (CRM) program for pilots, in 1980. The CRM program proved to be so successful that it is now used throughout the world.

Almost identical situation happened in 1963 with Aeroflot Tu-124, which had to ditch to Neva river due to fuel exhaustion after circling for two hours in the vicinity of Pulkovo airport, while crew troubleshot landing gear problems. Everyone on board survived the ditching.

Other aircraft accidents involving faulty landing gear indicator lights were Eastern Air Lines Flight 401, which crashed while circling around the airport at Miami, on December 29, 1972, LOT Polish Airlines Flight 007, and Scandinavian Airlines Flight 933, on January 13, 1969, which crashed into the ocean during an approach to Los Angeles International Airport. The Eastern crew became preoccupied with the nose gear indicator light problem and accidentally disconnected the autopilot, causing the aircraft to make a slow descent and crash into the Everglades. Further investigation revealed that the nose gear was down and locked. It was the same for the SAS flight, as the green light for the nose gear failed to illuminate after the landing gear was lowered. The SAS cockpit crew became so occupied with attempting to diagnose the lack of a nose gear green light that they allowed their rate of descent to increase, until that DC-8-62 crashed into the ocean, well short of the runway.

See also

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• Air safety
• Lists of accidents and incidents on commercial airliners
• List of airline flights that required gliding

External links

• Aviation Safety Network for United 173
• Accident details at planecrashinfo.com
• Photos of N8082U at Airliners.net
• Photos of Accident site at AirDisaster.com
• Airdisaster.com report