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Date: Thu, 15 Oct 1998 14:55:50 -0500
From: Snowbird <snbird@ibm.net>
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Subject: NTSB Reports on Midair Collisions: an Excursion
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In case anyone else is curious, I'll share my meanderings
through the NTSB data base at
    http://nasdac.faa.gov/asp/fw_ntsb.asp.

Search was conducted as follows:
Two years (1/1/94 to 12/31/96)
Report type: Accident
No restriction on category of operation.

A search on the phrase "Mid Air Collision: Yes" = 91 of 41439 accidents
Restriction to NOT ("phase of operation: 580 maneuvering" OR "phase of 
operation: 540 cruise") = 60 of 41439 accidents

Presumably 31 collision investigations involved cruise or maneuvering
flight (although note that this doesn't reveal proximity to airports).

Of the 60 collision investigations which did not involve cruise
or maneuvering flight, there were 26 duplicates, revealing 34 separate
events.

Of the 34 separate midair collision events, 8 involved towered
operations, 21 involved non-towered operations (the largest group), 
and 5 involved events away from an airport but described as other 
than cruise or maneuvering flight.  We can not conclude from this
that a midair is more likely to occur near a non-towered airport
(see below).

Of the 21 non-towered airport collisions, 4 involved IFR flight
(in VMC) or practice approaches.  3 involved actually NORDO aircraft, 
of which 2 were ultralights.  (1 midair at a towered airport involved
2 NORDO aircraft).

There was the largest number of midair collision events near
non-towered airports, but obviously we can not conclude that
a midair collision is *more likely* to occur near a non-towered
airport without knowing the relative numbers of operations at
non-towered vs. towered airports.  I haven't a clue where to find 
this info; anyone else?

Subjectively, I was impressed by several things.  

One, the large majority of the collisions at non-towered airports did 
NOT seem to involve what I would call "goofball behavior" such as the
wrong direction or altitude of patterns, aircraft in cruise flight
blasting through the airport at TPA, grossly misreporting actual
position or using conflicting runways.   There were several instances
of these of course, as well as several instances of non-standard 
pattern entries (including several practice instrument approachs). 

But the most common cause of midairs near airports was rather airplanes
flying regular patterns at TPA and even making position calls on CTAF! 
In many cases, the overtaking aircraft knew that the other aircraft was
in the pattern, even on the leg of the pattern he was about to enter,
but flew on anyway without visual contact or any attempt to check the
exact position of the other aircraft!  This was also the case in 
several accidents at towered airports.

Two, actual NORDO operations (ie non radio equipped planes) were only 
a small factor.  However, *failure to make* regular position reports
in a radio-equipped plane (which had made one or more calls, so 
presumably had a radio working) seemed to be a factor in roughly 
1/3 of the cases.

In other words, most accidents weren't caused by "jerk" behavior
or huge mistakes, but by omitting position reports or losing track
of another aircraft's position in the pattern -- mistakes I bet 
every single one of us have made at one or another time.

Three, it's really important to Just Fly the Plane.  Most of the 
planes which had midair collisions managed to land safely.  I
was impressed by this.

Four, bad wx or visibility was a factor in _very_ few of these
accidents.

Five, midair collisions are a very small percentage of all the
accidents which have NTSB reports (roughly 2%).

And last, By Durn I'll do anything to avoid studying for my
instrument written.

Hope someone else finds this interesting.

Snow"numbers geek is a compliment"bird


