Douglas DC-4 accident at Minneapolis, Minn., 18 Mar 1951 (N-95426)

Accident narrative

At approximately 11:07 a.m. on March 18, 1951, Northwest Airlines Flight 108, a Douglas DC-4 (N-95426), landed in deep snow adjacent to Runway 29-left at the Minneapolis-St. Paul International Airport. There were no injuries to the 13 passengers, one infant, or four crew members aboard, but the aircraft was substantially damaged.

### The flight

Flight 108 departed Portland, Oregon, on March 17 for Minneapolis, with scheduled stops. A routine crew change was made in Billings, Montana, where Captain Toy W. Franklin, First Officer Archie C. Keller, and two stewardesses took over the flight. Captain Franklin had 15,086 flying hours. The flight departed Fargo, North Dakota, at 0950 on an instrument flight plan. The aircraft's weight and center of gravity were within certificated limits.

En route, the crew received a Minneapolis weather report indicating a precipitation ceiling of 1,600 feet, an obscured sky, and visibility of one mile, variable with light and blowing snow. The flight contacted Minneapolis Approach Control and was cleared to the outer marker. Shortly after, the company radioed a message from a previous flight: "Reports indicate the approach lights on Runway 29-left are hard to see. Might be covered with snow."

Approach Control cleared the flight for an Instrument Landing System (ILS) approach and advised that the wind was north-northwest at 15 to 20 mph. The controller warned that there was eight to ten inches of fresh snow on the first third of the runway, though the northwest portion had been plowed and was in good condition.

At 1105, the flight reported having the field in sight. A minute later, the control tower sighted the aircraft over the end of the runway in a shallow right bank. It leveled off, entered a shallow left bank, leveled off again, and immediately touched down in deep snow to the right of Runway 29-left.

### What the investigation found

The DC-4 touched down about 600 feet northwest of the runway threshold and 96 feet to the right of the runway, in snowdrifts four to five feet deep. The nose wheel touched down 18 feet before the main wheels. The aircraft plowed through the snow in a nearly straight line for 274 feet. The nose gear collapsed and severed, and the aircraft came to rest in a nose-down, tail-high attitude. The inboard propellers, nose cap, and bottom structures were damaged. Investigators found all controls in their correct positions and the flaps down 45 degrees.

Runway 29-left was covered with eight to ten inches of fresh snow on its southeast half, making the approach end extremely difficult to recognize. High-intensity runway lights were operating at their highest intensity and marked by small red streamers, while the adjacent taxiway lights were marked by larger flags. However, Captain Franklin stated he saw no lights burning during the approach.

The high-intensity approach lighting system, located 117 feet left of the runway center line, was also operating at maximum intensity. A Notice to Airmen (NOTAM) published before the flight contained a typographical error stating the lights were 177 feet south of the center line, but Captain Franklin stated he recognized this as a discrepancy and was not confused by it.

Captain Franklin stated that he became contact at 2,100 feet near the middle marker, had the field in sight, and abandoned the ILS to continue visually. He described the airport as a "sea of snow" without contrasting features. He saw the approach-light structure slightly to the right, made shallow turns to align, and saw flag markers that he believed outlined the runway. The markers actually outlined the north edge of the runway and the south edge of the taxi-strip.

The Board assumed that blowing snow caused the pilot to momentarily lose sight of landmarks, such as the approach lights, losing his established alignment. The widely spaced flag markers may have given him a false indication that he was in line with the runway.

However, the Board noted that the captain had been warned about the unplowed runway and obscured lights by a flight that landed an hour and a half earlier. Because snow had fallen continuously since then, it should have been obvious the conditions had worsened. The Board found that the captain showed poor judgment in not executing a missed approach procedure given the adverse conditions and the aircraft's poor alignment at an extremely low altitude.

### Probable cause

The Civil Aeronautics Board determined that the probable cause of this accident was "the failure of the pilot to identify properly and align the aircraft with the assigned runway due to snow coverage and poor visibility."