03-07-1999 Ask Mike! Archive
So how many G's can my plane take?

Given that I fly a Cessna 172, I really don't have a need for a g meter. However, I have on occasion been bounced around pretty good in some clouds and have often wondered, just how much stress can my airplane safely handle?

Thanks, John

John:

The human body is an amazing thing; but unless you are a body builder or fitness fanatic, your aircraft can handle much more than you can.  Consider what a "G" is.  It is the force of gravity.  Under the typical FAA standard conditions, it's what your body weighs.  Accelerated positive, most typical general aviation aircraft are stressed to +4.5 Gs.  On the negative side, -1.5 Gs.  If you weigh, say, 200 pounds, +4.5 would be the equivalent of a 1000 pound put on your lap; I dare say you would be bruised and a bit nauseous.  To get to -1.5 G, you need to first go to 0 G, or complete weightlessness.  That's the light in the seat, but no pressure on the seatbelt thing, then you would end up with the 300 pound pull on your seat belt.

An accelerometer is not standard instrumentation except in aerobatic aircraft.  It's not a bad idea to get some aerobatic training, say, for your next flight review, and that will accomplish two things: 

1. You will be able to equate that feeling in your stomach with a number.
2. Being able to perform basic maneuvers assists in sharpening hand-eye coordination, and knowing what your limits are, assists in quicker decision making.

Please, keep in mind, after this training, you won't be nik-named Bob Hoover; stick to approved maneuvers as listed in your basic Aircraft Flight Manual.

Gear Green,
Mike