If It Hurts So Much, Why Would You Do It?
On January 9, 1998, at 19:25 local time, a Boeing 727-200 departed Houston, Texas. While climbing through 6000 ft. the crew heard a loud bang followed by intense vibration in the airframe. The noise level in the flight deck became so high that communication among the flight crew was almost impossible. The reasons for the noise and vibration are as follows: The No. 1 engine had lost a number of fan blades, resulting in violent vibrations that caused the cowling doors to become unlatched. The No. 2 engine also lost fan blades, and the No. 3 engine had a damaged pylon. The radome had been destroyed and departed the aircraft along with the radar antenna. The pressure bulkhead was penetrated, and the leading edges of both wings were damaged. The Kruger flap on the right wing was punctured, as was the wing adjacent to the flap. The right inboard slat and the wing area adjacent to the slat suffered the same fate. The first officer’s pitot tube was torn from the aircraft, rendering his airspeed indicator unusable. Overall, there was about $5,000,000 damage to the aircraft.
The cause of the incident was the aircraft’s collision with a flock of migrating snow geese, a situation that occurs far too often in North America these days, likely because of burgeoning populations of some species of waterfowl. However, the extent of the damage to the aircraft was probably greater than to be expected because of the high-speed departure trial that the aircraft was involved in. The Federal Aviation Administration (FAA) does not allow aircraft to fly above 250 kt. below 10,000 ft. mean sea level (MSL) in the United States, but trials were being conducted at the George Bush Intercontinental Airport (IAH) allowing aircraft to exceed 250 kt. on departure to test for gains in efficiency. At the time of impact, the B727 was flying at 280 kt. and still accelerating. The captain concluded that the high-speed departure program was "not a good idea." The outcome of the incident may not have been so favourable except for the fact that he had two second officers on board, providing a four-person flight crew to work through the check lists.
A discussion on the nuances of airworthiness requirements and speed restrictions below 10,000 ft. would fill several
Aviation Safety Letter newsletters, but suffice it to say that the impact force resulting from a bird strike increases with the square of speed, and every 10 kt. of increased speed results in considerably greater damage. Whether or not efficiencies are gained by high-speed departures is debatable, and, furthermore, aircraft components such as engines, windshields, and leading edge devices are not designed to withstand high-speed impacts with large birds. In Canada, the
Canadian Aviation Regulations (CARs) allow aircraft to exceed 250 kt. below 10,000 ft. above sea level (ASL) on departure or in accordance with a special flight operations certificate. Since most bird activity occurs below 10,000 ft. and high-speed departures likely keep you in that airspace longer, why would you want to exceed 250 kt. when the only advantage might be a few minutes of time saved? Is it worth the risk to yourself, your passengers, and your aircraft?
For additional information, please contact: Bruce MacKinnon, Wildlife Control Specialist, Transport Canada, Aerodrome Safety Branch, Phone: (613) 990-0515; Fax: (613) 990-0508; E-mail:
mackinb@tc.gc.ca
