Yeah, but isn’t that if you hit a wall,
another car, tree or slam into steep hill? Skidding across a field potentially
gives more distance and time doesn’t it (assuming we avoid ravines,
ditches, and the barn doors…)?
Kevin
From: Lancair Mailing
List [mailto:lml@lancaironline.net] On Behalf
Of Gary Casey
Sent: Saturday, August 11, 2007
10:26 PM
To: lml@lancaironline.net
Subject: [LML] Re: Forced landing
Just in case you want to worry even more about off-airport approach
speeds, the people that earn their keep designing crash protection in cars tell
me that crash "severity" is roughly proportional to the CUBE of
speed, not the square. Crash mathematics is a messy thing, but think of
it as requiring the energy to be absorbed in the same distance, not time.
Double the speed and you halve the time available to absorb 4 times the
energy. Going from 80kts to 100 is then almost twice as "severe."
yeah, I think about that 20 extra knots a lot.
Unfortunately
energy increases with the square of speed. For any given vehicle a
groundspeed of 100 KTS means a little over 50% more energy than a groundspeed
of 80 KTS. In other words it requires over 50% more distance to stop if
the brakes are applied at 100 KTS as it does at 80 KTS. Stopping
from 60 mph requries 4x the distance as compared to
stopping from 30 mph, under identical conditions and not including the
distance used during reaction time.
Aren't
you glad you asked?