Heard About The Bird?
Sharing The AirSharing the air with birds is a great thing, except when aircraft and birds try to occupy the same space at the same time. Usually that is a lose-lose proposition. In flight training, bird avoidance may not seem like a high-priority item, and yet there is enough evidence to suggest that CFIs and students should have at least a passing discussion about why it's good to avoid birds.
Reportedly, a CFI and student were cruising at 1,500 feet when they were approached by a flock of 10-pound turkey buzzards. The landing lights on their Piper Warrior were turned on, and most of the flock turned sharply left and dived. But one confused avian turned right and collided with the Warrior's stabilator. There was a loud bang followed by some vibration. The instructor declared an emergency and landed uneventfully at a nearby airport. The bird was not recovered and presumably fared less well than the airplane.
Bird strikes, while not considered a big issue for light general aviation aircraft, have been responsible for some major accidents and more than 300 fatalities since the age of flight began. According to an FAA study, more than 16,000 collisions occurred during a recent seven-year period over the United States, Puerto Rico, and the U.S. Virgin Islands. Nearly 80 percent occurred less than 1,000 feet above the ground, but some high fliers have encountered flocks of birds at altitudes exceeding 20,000 feet.
Some of the physics of a bird encounter may pique your interest. An FAA flight standards district newsletter mentions that hitting a two-pound seagull - the type of bird most likely to be involved in a bird strike - at a speed of 120 mph results in an impact force of 4,800 pounds. Jets have a much bigger problem. An impact at 600 mph results in a force of more than 35 tons. Frequently, jet engines will be severely damaged or fail as the result of a strike. The U.S. Air Force suffers millions of dollars of losses each year as well as periodic fatalities caused by bird strikes involving high-speed aircraft.
The engine of a propeller-driven aircraft is seldom harmed. The danger comes from broken windshields or structural damage to wings or empennage. The danger of a bird joining you in the cockpit should not be underestimated. A firsthand account comes from a Cessna 172 pilot: "With explosive suddenness, the windshield shattered, air rushed in, and my door blew open. There was a thud against the back of my seat, and the noise rose to deafening levels. With increased drag we quickly lost airspeed and altitude."
One of the most likely places to encounter birds is the airspace around airports. Airports are occasionally located adjacent to dumps. This is considered an incompatible mix as birds are attracted in large numbers to garbage and thus pose a hazard to arriving and departing aircraft. To help, FAA has published Advisory Circular AC 150/5200-33 to provide guidance to communities and airport managers.
For pilots, the Air Force Bird Aircraft Strike Hazard Team (BASH-I'm not making this up) and FAA's Aviation News from January 1996 offer this guidance for avoiding bird strikes:
- Avoid low altitude flight as much as feasible to reduce the risk of a strike.
- Strikes are most likely in August, September, and October - particularly in migratory flyways. These tend to be the larger birds. Keep a lookout, just as you would for other flying objects.
- Dawn and dusk are the times with the highest probability of a bird encounter.
- Turn on landing or recognition lights. This helps birds see oncoming aircraft.
- Plan to climb. Birds almost invariably dive away, but there are exceptions.
- Slow down. This will allow birds more time to get out of your way and will lessen the impact force if you do hit one.
- If a collision seems likely, duck below the glareshield to avoid being hit by the bird and flying plexiglass. Advise passengers to do the same. Protect your eyes and head.
- If a collision occurs, fly the aircraft first. Assess the damage and decide whether you can make it to an airport or you should make an off-airport landing. Declare an emergency - it doesn't cost anything. Even if no damage is visible, divert to the nearest airport and have a mechanic look at the airplane. There are likely to be some aerodynamic modifications that do not have FAA approval.
For more information on bird strikes, see the FAA's bird strike page ( www.faa.gov/ arp/pdf/strkrpt.pdf ), AOPA's bird strike pamphlet (www.birdstrike.org ), and the joint FAA/USDA Web site (www.faa.gov/ arp/pdf/manfin.pdf ). Bruce Landsberg is executive director of the AOPA Air Safety Foundation.
By Bruce Landsberg