# B G-forces exposed during maximum perfomance Takeoff (Heli)

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1. Jul 29, 2017

### Chris_L

Hello Folks

I'd like to know if anyone of you guys know how to calculate the gforces in a glider (in this case helicopter) during maximum performance acceleration? Tonight I had a very serious discousion with a relative of mine who doubt that it's possible to accelerate from 0 to 140 kts within 3 seconds. His argument was that it's unplausible due to too much g-forces. I have to admit that I counldn't seat on the "jump seat" but I could glimpse at the MFD (artificial horizon) of the "captain" during this maneuver. I could see that we climbed to aproximatly 500 fts. agl (above ground level) within 5 seconds. There after the PIC (pilot in comand) dived 30° to 35° nose down for aproximatly 3 seconds to accelerate from 0 to 140 kts (~260 kmh). Right now I'd like to know tow things. First of all why I couldn't feel any sort of acceleration at all and secondly what would be the exact formular behind it (please with detailed eplanations). To be honest it was the same feeling which I had during the acceleration in a glider. By the way my body where afected with lateral g-forces while my head has been exposed to transvesre g-forces during the last second.

I'd like to thank everyone of you in advance for your replies.

Best Wishes

Chris_L

PS.: First of all I want to say that I'm not a native English speaker and secondly due to my school system I never could take serious physics lessons so please bear with me and thirdly I don't know if this question would be either an basic or advanced question.

Last edited by a moderator: Jul 29, 2017
2. Jul 29, 2017

### Staff: Mentor

Why do you use the impractical US units then?

Accelerating horizontally from 0 to 260 km/h (72 m/s) in 3 seconds would lead to an acceleration of at least ~2.5 g (vertically relative to the helicopter frame). You get a similar value for climbing to 170 meters in 5 seconds. That would certainly be notable.

Accelerating downwards (actively) would make a 2 g acceleration possible with a 1 g experience, but I guess that's not what happened.

Where do the time estimates come from?

3. Jul 29, 2017

### Chris_L

To answer you first question. Here in Germany there is a law in aviation. As soon as the airframe has an engine we have to fly with fts and kts while flying gliders we can fly with meters and kmh. The reason why engine driven airplanes or helicopter has to fly with fts and kts is to make it even e. g. the ATC instructs the pilot during the aproach phase to reduce to 210 kts and to descent to 3000ft. It would be a complete mess if the Controler had to switch between fts, meters, knots, kmh and miles.

Secondly I'm a drummer and I have the time down. So therefore I'm pretty confident that I got the time down right.

Thrid we had to climb to at least 500 fts. I could see this on the a. m. artificial horizon which has an radar altimiter which is equiped on all modern airplanes and also helicopters. During this maneuver we decended from 500 fts to aproximatly 300 fts.