# Avoiding Bird Strikes, I

In the old days when aircraft were made of wood and linen and men of steel, birds had no problem avoiding these low and slow aircraft. But todays machines are fast and make less noise, birds are having a lot of trouble staying out of the flight path.

Certain areas in your country might be designated as bird sanctuaries and flying in such an area at low altitude involves a higher risk of bird strike.

The pilot has the responsibility to see and avoid. But in the case of birds that could prove difficult. Most bird strikes happen between 50 and 800 feet AGL, although the risk is not zero at higher altitudes.

The impact of a bird on your windscreen, or even if it is ingested in a turbine, is enough reason for a distress or an emergency situation. As the amount of energy with a small bird is very high due to the velocity of bird and aircraft and is more than enough to create a lot of damage.

In this article we are going to discuss the effects of a bird strike, as even a small bird can have big consequences for the aircraft and those on board.

## Bird Hazards

Piston engined aircraft have an advantage compared to turbine powered types, they make more noise thus warning the birds to get out of the way. Do keep in mind that some high speed piston aircraft do not give the birds time enough to move out of the way. Think Lancair types. Higher speeds lead also to greater impact forces and possibly more serious results.

A head on collision has enough energy to create a problem for the aircraft, shattering windscreens, tearing open skins, rupturing hydraulic lines, destroying propellers, turbine blades and more.. you get the picture.

### Impact Energy

According to Newton, kinetic energy is defined as: E = 1/2 * m * v2, with m (mass) in kg, v (velocity) in meters per second and the result is in Joules or kgm2/s2.

The above was a little technical but we need it to understand why a bird strike can cause so much damage. For example: lets take a bird of 500 grams and this bird hits an airplane traveling at 90 kts (46,3 meters per second). The kinetic energy of the impact is 1/2 * 0,5 * 46,32= 536 Joules. The airplane is thus hit with an force of 536 kgm2/s2. And that will make quite a dent...

Doubling the weight of the bird doubles the impact energy, but if the airplane travels twice as fast (180 kts) the impact is quadrupled! See the results here: E = 1/2 * 0,5 * 92,62 = 2144 Joules.

Flying low at high speed gets a whole new meaning here...

## Bird Sanctuary Areas

Birds usually nest in the same place every year. These places are commonly known as bird sanctuary areas and should be avoided by aircraft as much as possible, especially when flying low. You may expect large number of our feathered friends near or at large bodies of water. It is wise to overfly these areas by at least 1000'.

### Avoiding them

Bird sanctuary areas are established in regions where birds tend to nest and raise their chicks. Some countries mark them on the VFR aeronautical maps and they usually require a minimum overfly altitude, 1000 ft or so. Best to fly even higher or circumnavigate these areas if possible.

### Maps

Bird sanctuary areas are depicted on aviation maps and there should be a section in the AIP explaining in what areas and times of year you can expect birds to migrate to and from warmer places.

### Written by EAI.

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