Douglas DC-8-61 accident at Portland, Oregon, 28 Dec 1978

Accident narrative

On December 28, 1978, at about 1815 Pacific standard time, United Airlines Flight 173 crashed into a wooded, populated area of suburban Portland, Oregon, about six nautical miles southeast of Portland International Airport. The McDonnell-Douglas DC-8-61 had delayed southeast of the airport at a low altitude for about an hour while the flightcrew coped with a landing gear malfunction and prepared the passengers for a possible emergency landing. Of the 181 passengers and eight crewmembers aboard, eight passengers, the flight engineer, and a flight attendant were killed. Twenty-one passengers and two crewmembers were seriously injured. The aircraft was destroyed, but there was no fire.

### The flight

Flight 173 was a scheduled flight from John F. Kennedy International Airport in New York to Portland, with an en route stop at Denver, Colorado. The aircraft departed Denver with 46,700 pounds of fuel, which included the required fuel for the planned 2-hour, 26-minute flight to Portland, plus reserve and contingency fuel.

The crew consisted of Captain Malburn A. McBroom, who had 27,638 total flight hours; First Officer Rodrick D. Beebe, with 5,209 hours; and Second Officer/Flight Engineer Forrest E. Mendenhall, with 3,895 hours.

### Sequence of events

At 1705:47, the flight contacted Portland Approach, descending to 10,000 feet, and reported having the field in sight. As the aircraft descended through about 8,000 feet, the first officer requested 15 degrees of flaps and asked that the landing gear be lowered. The captain later stated that the gear extension was noticeably unusual, accompanied by a loud thump and a right yaw. The nose gear green light illuminated, but no other gear indicators lit up.

At 1712:20, the flight advised Portland Approach of a gear problem and stated they would maintain 5,000 feet. Approach vectored the aircraft into a holding pattern south and east of the airport. In the cockpit, the flight engineer checked the visual indicators on top of both wings, which showed the main landing gear was down and locked.

At 1740:47, the captain contacted company dispatch and maintenance personnel in San Francisco. He reported having about 7,000 pounds of fuel and stated his intention to hold for another 15 or 20 minutes to prepare the passengers for an emergency evacuation. At 1744:03, San Francisco asked if a landing at five minutes past the hour was acceptable. The captain agreed, stating he would not hurry the flight attendants.

At 1746:52, the first officer asked the flight engineer how much fuel they had. The engineer responded, "Five thousand." At 1749, the captain noted that the feed pumps were starting to blink, which indicated 5,000 pounds of fuel remained. Shortly after, the captain asked the engineer to figure another 15 minutes for the landing data card. The engineer replied, "Fifteen minutes is gonna really run us low on fuel here."

At 1751:35, the captain instructed the engineer to tell the company representative in Portland they would land with about 4,000 pounds of fuel. At 1756:53, the first officer again asked about the fuel, and the engineer reported 3,000 pounds remained.

At 1802:22, the engineer advised, "We got about three on the fuel and that's it." Two minutes later, the first officer told Approach they intended to land in about five minutes. At 1803:23, Approach asked for the amount of fuel and the number of people on board. The captain replied they had about 3,000 pounds of fuel and 172 people plus six infants.

At 1806:19, the first flight attendant entered the cockpit and reported the cabin was ready. At 1806:40, the captain said, "We're going to go in now." Almost simultaneously, the first officer said, "I think you just lost number four... better get some crossfeeds open." He then told the captain they were losing an engine. The captain asked why, and the first officer responded, "Fuel." At 1807:06, the first officer stated the engine had flamed out.

At 1807:12, the captain requested clearance for an approach, and Approach provided vectors for a visual approach to runway 28L. Over the next two minutes, the crew discussed losing the number three engine and the fuel gauges showing zero or 1,000 pounds. The engineer reported the totalizer was down to 1,000 and the number two tank was empty.

At 1813:21, the engineer stated, "We've lost two engines, guys," followed by, "We just lost two engines - one and two." The captain said, "They're all going. We can't make Troutdale." At 1813:50, the first officer declared a Mayday to Portland tower, stating the engines were flaming out and they were going down. About 1815, the aircraft crashed into trees and two unoccupied houses.

### What the investigation found

The National Transportation Safety Board found that the aircraft arrived in the Portland area with the preplanned 13,800 pounds of fuel. While holding at 5,000 feet with the landing gear down and flaps at 15 degrees, the aircraft burned fuel at a rate of about 13,209 pounds per hour. Evidence indicates that the fuel quantity indicating system accurately indicated the fuel quantity to the crew.

The investigation revealed severe corrosion in the mating threads of an attachment eyebolt on the right main landing gear retract cylinder assembly. This corrosion allowed the parts to pull apart, causing the right main landing gear to free-fall when lowered. The rapid fall disabled a microswitch, which prevented the gear-position indicators in the cockpit from illuminating. Both main landing gear were fully extended at impact.

The Board noted that the captain failed to relate the fuel remaining and the rate of fuel flow to the time and distance from the airport. His attention was directed almost entirely toward diagnosing the landing gear problem. The Board also noted that the other two flight crewmembers failed to take affirmative action to ensure the captain was fully aware of the time to fuel exhaustion.

### Probable cause

The National Transportation Safety Board determined that the probable cause of the accident was "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 Board found that contributing to the accident was "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."