Conscientious Crew Forget How Much Fuel Left (Portland, 1978)

This absurd United Airlines DC-8 accident led to the introduction of a new way for pilots to work together called CRM.
United Airlines Flight 173, December 28, 1978

On December 28, 1978, a United Airlines McDonnell Douglas DC-8 with the flight number 173 was approaching Portland Airport in Oregon. The 189 people on board included the captain, the first officer, a flight engineer, a deadheading captain two weeks from retirement, and four cabin attendants. There were six infants. The ETA was 17:15, and so far everything was on schedule.

On leaving the gate at the previous stopover at Denver, there had been enough fuel for the two-hour, twenty-six-minute leg to Portland, with an additional forty-five-minute fuel reserve to meet FAA requirements and a further approximately twenty-minute fuel reserve to meet company contingency requirements. Portland Approach Control had given them clearance to make a straight-in landing on Runway 28, so they should have been landing with their fuel reserve of just over an hour intact.

As they descended through six thousand feet with the runway in sight, the first officer, who was the pilot flying (PF), requested fifteen degrees of flap and the lowering of the landing gear. The captain extended the flaps to fifteen degrees and initiated the lowering of the landing gear, which to his surprise dropped down with an unusual thump and more quickly than usual. The captain later said the first officer had noticed a simultaneous yaw to the right.

The jolt was even more noticeable to the flight attendants and passengers farther back in the aircraft. More disconcertingly, one of the landing gear indicator lights failed to show green, presenting the crew with the worrying possibility that the right-hand landing gear assembly was not properly down and locked.

Unaware of any such problem, Portland Approach told them to switch to the Portland Tower frequency for the actual landing. UA173 declined, saying they had a “gear problem” and wanted to stay with approach, maintaining a height of five thousand feet and a speed of 170 knots.

According to, one of the approach controllers in question said as recently as 1998/9 that the controller gave the captain the option of holding at six thousand feet over the Laker outer compass locator until he sorted out the problem. From there he could have made a dead-stick landing at any time onto either runway, but instead he opted to orbit twenty miles or so southeast of the airport.

Approach agreed to this request to orbit, telling them to turn left onto a heading of two hundred degrees that would take them away from the airport and out of the path of any other incoming aircraft.
They carried out various checks, even contacting the company’s San Francisco Maintenance Control Center, who could not think of anything further.

The captain then briefed the senior flight attendant about getting ready for an emergency landing and possible evacuation but did not give her a deadline or suggest any state of urgency. (He later said he assumed it would take ten or fifteen minutes, and that final preparations could be carried out as they came in to land.)

At that time, all three aircrew were fully aware of the fuel situation, since at 17:46:52 the flight engineer replied to the first officer that they had five thousand pounds of fuel left. Not only did the first officer acknowledge this, he immediately asked the captain,

What’s the fuel show now?

The captain replied,

The first officer duly repeated,

Further confirmation that there was only about five thousand pounds of fuel left was given by the fact that the inboard fuel pump lamps started to blink, as they are meant to do if the fuel level falls below five thousand pounds. At that point, the aircraft was about thirteen nautical miles south of the airport and heading away from it.

With not much time before the fuel would run out, they yet again discussed the status of the landing gear, before being interrupted by a course change and advisory from approach control.

17:50:20 Captain to flight engineer:
Give us a current card on weight. Figure about another fifteen minutes.

Flight engineer:
Fifteen minutes?

Yeah, give us three or four thousand pounds on top of zero fuel weight.

Flight engineer:
Not enough. Fifteen minutes is gonna . . . really run us low on fuel here.