Saturday, May 22, 2010

Mid-Air Collisions Are Too Rare to Worry About or It is a Big Sky!

Alfred E. Neumann
625 words
How often do mid-air collisions occur?  I went to the  Nall Report on the AOPA's web site to see the most recent General Aviation statistics available for 2007. The Nall Report on General Aviation accident statistics only covers fixed-wing general aviation aircraft weighing 12,500 pounds or less. It says there were only 10 in all of 2007!

Surprisingly these 10 mid-air collisions involving 20 different aircraft with 21 pilots and passengers resulted in only 4 deaths. Two of the mid-air collisions were by four aircraft involved in formation flight.

The fact mid-air collisions may be survivable is rarely written or talked about. In 2007, there were a total of 17 survivors from six different mid-airs involving 12 aircraft!

My flight career took of in January of 1961 when I first soloed a Piper PA-12 Super Cruiser as a member of the Kent State University Flying Club.  I began to fly for Trans World Airlines in 1964. First as a co-pilot on the Lockheed Constellation and finally as a Boeing 747 captain.  Along the way  I accumulated a lot of flight time over the next 50 years.

In that 50 year period of time, I never experienced a close call from a mid-air collision. Why?

The continental United States is comprised of 3 million square miles.  If the airspace to a level of 10 miles is available to be used by all aircraft the available amount of airspace is 30 million cubic miles.  This is a heck of a lot of airspace or another way of saying it is to say: "It is a big sky!"

Now how many aircraft are using the big sky at the same time?  Today, it is possible to obtain the answer from a web site that counts  aircraft in the air called  I just went to the web site and right now (Sunday, May 22, 2010 at 7:30 PM there are 3,672 airborne aircraft including 205 which are operating under Visual Flight Rules (VFR).

The highest number of aircraft that are in the air at the same time counted by FlightAware is 5,650.

Assuming the aircraft were distributed in only half the available airspace or 15 million cubic miles it would mean each aircraft has approximately 3,000 cubic miles or a space 20 miles long, 20 miles wide and 7 miles high.

This is the primary reason for the lack of mid-air collisions. The Big Sky!

What role does Air Traffic Control play in mid-air collision prevention?

Another little talked about and written about is the possibility that it might play a negative role meaning ATC procedures may actually contribute to the mid-air collision issue.  

ATC will normally assign aircraft to fly along an established airway such as Victor 210 separating us by altitude,  lateral and longitudinal separations and watched over by radar. If either an air traffic controller or a pilot makes a mistake in the altitude flown or assigned, a mid-air collision is much more likely to happen due to the traffic being compacted by the present system. 

In the real world, it means they are actually packing us closer together than if random flight paths were being flown by each aircraft. Normal vertical separation between Instrument Flight Rules (IFR) aircraft is just 1,000 feet. The normal vertical separation between IFR traffic and Visual Flight Rules (VFR) traffic is just 500 feet.  

As a result of being aware of these facts, I will admit to not ever being overly concerned about mid-air collisions while I am flying my airplane.
What level of mid-air collision concern to you experience while flying your plane?

By the way, there is a matter of certainty about a comet hitting the earth at some point in the future and wiping out all life forms.
Do you worry much about it happening?

"What me worry?"


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