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ACRO E-mail Archive Thread: [IAC] Accidents

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ACRO E-mail Archive Thread: [IAC] Accidents


Thread: [IAC] Accidents

Message: [IAC] Accidents

Follow-Up To: ACRO Email list (for List Members only)

From: Eric Rood <ericrood at>

Date: Fri, 16 Jul 1999 02:51:32 UTC


  A little physics 101 comes in handy here, if you think about it.
  A Formula 1 car probably has a pretty low flat plat area, so we can
assume low drag.  Next, consider that a race car is really a two
dimensional vehicle.  When you let off the gas, it slows down (lets add
friction), no surprises there.
  Now, let's look at the airplane.  Okay, a Pitts is pretty draggy, all
those flying wires and stuff hanging out in the breeze, and those fat
stubby wings don't help.  But, it is a three dimensional vehicle. Pull
back the power and you can not only maintain the same airspeed (as long as
you have altitude), you can even INCREASE your airspeed.  Pretty neat
stuff, that gravity.  9.8 m/sec/sec (32 ft/sec/sec for you non-metric folks)
  Next we move to construction.  Strength to weight is the name of the
game for both designs.  However, how many acro engines get pumped up with
single/dual turbochargers and horesepower in excess of 300 continuous? 
Not too many, huh?
  Structure.  Design to be frangible and impact absorbant.  Maybe for the
race car, but not the aircraft.  Typical aircraft design calls for a
safety factor of 1.5.  Because it only has to move in one direction, the
automotive designer can spare the increase in weight without badly
compromising the performance and provide a safety factor of at least 3.
  Where does that leave us?
  The aircraft is lighter, has less impact tolerant structure, and gains
momentum and inertia in a power off condition.
  The race car is heavier, stronger and loses momentum and inertia in a
power off condtion.
  Which would you rather ride in, though?

Eric Rood
ericrood at


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