Accident at Ellicott City, Maryland, 23 Nov 1962

Accident narrative

On November 23, 1962, United Air Lines Flight 297, a Vickers-Armstrongs Viscount, crashed in a wooded area six miles west-southwest of Ellicott City, Maryland. The aircraft had penetrated a flock of whistling swans at 6,000 feet, resulting in a collision that destroyed the left horizontal stabilizer. All 13 passengers and four crew members were fatally injured.

**The flight**

Flight 297 was a regularly scheduled passenger service from Newark, New Jersey, to Atlanta, Georgia, with planned stops in Washington, D.C., and North Carolina. The crew consisted of a captain, a first officer, and two stewardesses. The aircraft departed Newark at 1139 on an instrument flight plan.

The flight progressed normally, and at 1214, Washington Center cleared the aircraft to descend from 10,000 to 6,000 feet. At 1219, the controller issued an advisory: "Be advised there’s been numerous reports of considerable amount of ducks and geese around this area." The crew acknowledged the report.

At 1222, Washington Approach Control established radar contact, instructed the flight to turn, and provided vectors for a final approach at Washington National Airport. The crew acknowledged and verified the altimeter setting. At 1223, approach control transmitted an additional vector to 180 degrees, but received no reply. Radar contact was lost at 1224.

Witnesses near the crash site observed the Viscount at a very low altitude, turning left on an east or southeast heading. The aircraft abruptly rolled inverted and disappeared through the trees in a near-vertical attitude. Some witnesses initially heard an unusual noise and saw shiny aircraft parts falling before the crash.

**What the investigation found**

The main wreckage struck the ground inverted at a 46-degree angle. A severe post-impact ground fire consumed much of the fuselage and wings. Investigators found that parts of the left and right horizontal stabilizers and elevators had separated in flight, falling up to half a mile from the main crash site.

All four engines were recovered and showed evidence of producing power at impact, with no signs of bird ingestion or prior malfunction. The aircraft's flight recorder showed that heading, airspeed, vertical acceleration, and altitude traces all became suddenly excursive at approximately the same time. In less than one minute, the altitude dropped from 6,000 feet to ground level, while vertical acceleration fluctuated from 1.7 positive to 3 negative G's.

Investigators found bird remains on both horizontal stabilizers, indicating two distinct strikes. A bird struck the right horizontal stabilizer with a glancing blow, causing only superficial damage. However, another bird struck the left horizontal stabilizer directly on the leading edge, 49 inches outboard of the fuselage. It penetrated the leading edge, fractured the spar web, and dented the elevator.

The Board determined that this damage weakened the structure, causing the left horizontal stabilizer and elevator to fail downward and slightly aft under normal flight loads. This failure generated a violent instantaneous nose-down pitching moment. The elevators were displaced beyond their limit, imposing a severe down load on the right horizontal stabilizer, which also failed downward and separated. This breakup rendered the aircraft uncontrollable.

A partial bird carcass was found 10 feet from the separated left stabilizer section. The U.S. Fish and Wildlife Service identified the remains as a whistling swan. The agency noted that average weights for these swans were 14 pounds for males and 11.5 pounds for females, though they are known to exceed 18 pounds.

Weather Bureau radar at Washington National Airport had tracked echoes described as "birds" or "angels" throughout the day. Additionally, a pilot flying near Beltsville at 1230 reported sighting a flock of about 50 very large white birds at 5,500 feet, within eight miles of the crash site.

**The bird strike hazard**

The Board discussed the evolving hazard of bird strikes, noting that a 1949 Civil Aeronautics Administration report had found tail strikes to be rare, with windshields being the primary vulnerability. Prior to the 1960 crash of a Lockheed Electra in Boston, no air carrier fatalities in the United States had been caused by bird strikes.

While the Boston accident involved engine ingestion during takeoff, the Board noted this Viscount accident revealed a different problem: a single bird causing immediate structural failure. The Board observed that modern aircraft designs, which feature higher climb and descent speeds and tailplanes mounted above the protection of propeller discs and wings, are more vulnerable to severe structural damage. The Board recommended expanding Federal Aviation Agency test programs to include overall protection against catastrophic structural damage from bird strikes.

**Probable cause**

The Board determines that the probable cause of this accident was "a loss of control following separation of the left horizontal stabilizer which had been weakened by a collision with a Whistling Swan."