Birds and Jet Engines

Since the earliest days of powered flight, airplanes and birds have on occasion run into one another. After their historic December 17, 1903 first-powered flight at Kitty Hawk, the Wright brothers, Orville and Wilbur, continued test and training flights over Huffman Prairie in Dayton, Ohio. On September 7, 1905 Wilbur was piloting and recorded that he tangled with a flock of birds (probably red-winged blackbirds), killing one, but with no ill effects to pilot or plane. The earliest fatal airplane crash attributed to a bird strike, took place seven years later on April 4, 1912. Calbraith (Cal) Perry Rodgers, flying in a Wright Flyer over Long Beach, California, ran into a flock of sea gulls, crashed the biplane into the surf and was killed. The conflict between birds and airplanes has grown greatly since these earlier times, with engineers striving to ensure the safety of crew and passengers in the event of a bird strike. Jet propulsion itself seriously increased the gravity of bird strike damage, giving birds less time in which to avoid an approaching aircraft, with the resulting higher speed impact causing much greater aircraft (and bird) damage. As many of us know, jet engines themselves are probably aircraft components most vulnerable to damage by ingested birds, composed as they are of intricate high-speed rotating parts. All commercial jet engines must comply with bird ingestion regulations established by worldwide regulatory authorities. As pointed out in an earlier GGTN article [1] , these regulations are all similar and call for demonstrations of an engine's ability to ingest birds in small, medium and large categories. Not being able to meet these regulations can have serious consequences for an engine company. For instance, while in the final stages of developing their early RB211 turbofan engine, Rolls-Royce failed certification-required bird ingestion tests, causing the bankruptcy of the company in 1971. Most jet engine bird encounters occur during takeoff. Stuart Frost, a retired Pratt & Whitney engineer gave me a first hand account of an engine bird strike he experienced while traveling on business on a flight from Dublin to London on December 7, 1985. He was sitting in seat 2A on an Aer Lingus Boeing 737, with a good view of the front of the Pratt & Whitney JT8D-9A left engine #1. After lift-off from Dublin Airport the aircraft, with 117 passengers, encountered a flock of 20-30 Black-headed gulls (about a pound …