Calculating G Forces from IGC file?
Poul - Wow. That was intense. I agree that this isn't just an
exercise in the vertical component.
John - I think you are pointing me in the right direction.
I came up with this math for just the vertical component. Does this
math seem correct?
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RateofClimb (vertical speed) m/s = (BRecord_Altitude_N meters -
BRecord_Altitude_N+1 meters) / BRecord_interval*
G force = (RateofClimb_N m/sec - RateofClimb_N+1 m/sec) /
(BRecord_interval*) / (9.80665 m/sec2)
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* Typical IGC log file interval has B record entries every 4 seconds.
Yours may be different. And in the C302 if you hit the event button,
the interval always goes to 1 second.
At first glance the second division by the BRecord_Interval seems
wrong, but the BRecord_Altitude's are spaced by the BRecord_interval
AND the RateofClimb's are also spaced by the BRecord_interval.
I looked at a flight in which I remembered the vario going to +17
knots (whoop!). I calculated the G force at 8.4. Seems about right.
This gives a four second averaging so no telling what instantaneous
rates are. So for those flying a ridge where they are getting bounced
up/down repeatedly, this 4 second calculation wouldn't say much about
what you are experiencing. Makes me want to change my log rate to 1
second! Or buy a G meter!
If my math is correct (big IF) then I will publish my calculations so
anyone can plug in their B records and calculate/graph the results.
- John
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