What are the odds???

[Del Rykert]

And what happens to the odds when you see three mid-airs in one year spread over only 5 contests. Course the two years after that black year and the couple before were none noted. Made some of us stop practice flying with two planes in air.
 
        Del

  ----- Original Message ----- 
  From: David Flynt 
  To: discussion at nsrca.org 
  Sent: Saturday, August 02, 2003 3:56 PM
  Subject: RE: What are the odds???


  I'll take a crack at the question.  Maybe if we put our heads together we can determine the actual odds.  Let's speculate that one flight out of every 2000 results in a mid-air collision, so long as there is at least one other plane in the air.  Now, let's enumerate the common type of model airplanes that can fly off a paved runway.  There are 1) pattern planes, 2) trainers 3) 40 - 120 size sport planes, 4) scale planes, 5) pylon racers.  Most planes are in the 2) and 3) category, but to keep the numbers simple, let's say there are an equal distribution of each type.  A further simplification is that each plane category shares the airspace equally, which will certainly skew the calculation.  For example, I would argue that it is more common for two or more pattern planes to be in the air at the same time, than it would for a pattern plane and a trainer to be in the air at the same time.

  Ok, so now, out of every flight that occurs at your field, lets say that 1 of every two flights has at least two planes in the air.  The result then is, on any given flight for two trainers to collide, 1/2000 * 1/5 * 1/2 = 1 in 20000.  The results for two pattern planes would be the same.  Now for two trainers to collide on day one, followed by two pattern planes to collide on day two, might be a little tricky to calculate.  I don't think that it is simply 1/20000 * 1/20000.  It should be the same odds of "What is the probablility of any two randomly chosen people have a birthday one day before the other".  I think that the answer is 1/365 * average number of flights per day, say 10.


  So I think the odds are rougly 1/20000 * 1/20000 * 1/365 * 10  = 1 chance in 14,600,000,000 flights that occur at your field.  And you can be sure that your field will never see that many flights.  For comparison, McDonald's has sold about 7 times as many hamburgers.

  My intuition says that my assumptions and math must be way off, because with odds that low, the scenario you describe would be near impossible to observe.  Any math wizards out there have a better answer?

  A more interesting question to me is, how offten do pattern planes collide at contests?  I can control mid-airs outside of contests, but we are all subject to the odds of a mid air if we participate in a contest.  Let's say there are 10 mid-airs out of all the 8 NSRCA districts each year.    And lets say there are 7 contests per district on average.  Then that is 56 contests.  Then the odds of having one mid air in a contest is 1 in 56.  Now if there are 20 pilots average per contest, then your chance of mid-air is 1/(56 * 10) = one chance in 560 contest attendances (I think).

  David Flynt


    -----Original Message-----
    From: discussion-request at nsrca.org [mailto:discussion-request at nsrca.org]On Behalf Of FlyFutabaGuy at aol.com
    Sent: Saturday, August 02, 2003 1:36 PM
    To: discussion at nsrca.org
    Subject: What are the odds???


    Yesterday, during our annual fun day for the ARC (association of retarded citizens) fun day. I was coming in to land the trainer I was flying the kids on, and I mid-aired Gordon Anderson, who was also flying a trainer. Luckily I got mine back, Gordon's was a little lift impaired with 1/2 a wing and didn't get his out of the flat spin.. This was the first mid-air I have ever seen... Today, practicing pattern, my dad took his Olympian off, and on the procedure turn mid-aired with Dennis Cone, another local pattern pilot. Both planes destroyed.... WHAT ARE THE ODDS??? think we should take a week off to let the curse wear off??

    -Brett Bowen
    District 8 Advanced 
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.f3a.us/pipermail/nsrca-discussion/attachments/20030803/34168f9f/attachment.html