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i want to ask this time as to "what are the areas of an aircraft that feels or suffers the most from G forces?". i am asking this in terms of structural design and physical limits of the pilot(the position and seat angle) and the plane. please try not to limit the airplane model to simple light-aircraft,try to expand it near to military Aviation and other else.

if possible, please try not to use high-falutin words since i'm having a hard time with words in English.

If you can not understand this clearly, i am sorry for my poor English and Grammar, and also i want to elaborate more, but i can't translate it properly at the moment.

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Basically 3 places on an airplane see very high concentrations of stress in a small area from in-flight G loads. In this case we'll say a single engine light aircraft.

  1. Wing root spar fittings on a cantilever wing - the bottom in tension and the top in compression. For a high wing airplane with struts, it will be the strut attachments at each end that join the strut to the fuselage and wing.
  2. The roots of the horizontal tail, same except upside down - bottom in compression and top in tension.
  3. Engine mount attachment to the firewall - top mount in tension and the bottom mount in compression.

Those are the points where flight loads from a lot of mass are concentrated at a single point or set of points during high G loading and are where the structural elements will be heaviest. For most other areas the loads are distributed over more of a large area.

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  • $\begingroup$ I think this answer would be spot on if you add “the pilot” to the top of the list. $\endgroup$ – Notts90 Dec 24 '18 at 23:28
  • $\begingroup$ Especially if he suffers from hemorrhoids! $\endgroup$ – John K Dec 25 '18 at 2:48
  • $\begingroup$ oh ok, ill change it a little bit, so that people who want to give answer might understand it more $\endgroup$ – Nightshade Dec 25 '18 at 17:31
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Wing attachment points. (spars and struts)

Not every answer requires paragraphs of postulating and philosophizing.

Reference: 115 years of heavier-than-air aviation accident reports.

In 2002 all large air tankers were grounded after two of them had wing spar failures a month apart. Both were large, 4-engine ex-military airplanes.

Five days ago the FAA proposed an AD on Piper wing spars because the wings keep falling off.

Lowell Bayles was killed in a Gee Bee racer in 1931 when the wing spar failed and the wing ripped off.

In 2012 the EASA issued an AD on the A380 because of cracking in the wing spars after they “found cracks in almost all of the planes inspected”.

This is a straightforward question with a simple answer. All airplane types and sizes have the same major mode of structural failure due to stresses imposed by the force known as "Gs".

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    $\begingroup$ Well I think it’s an answer, just not a good one. I’d recommend elaborating and adding some references if possible. $\endgroup$ – Notts90 Dec 24 '18 at 23:29
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    $\begingroup$ It is THE answer. There is the supporting structure (the wing), and the thing being supported (the fuselage). The most susceptible area is where these two are joined, which is the spars and supporting struts. Not every answer requires paragraphs of postulating and philosophizing. Reference: 115 years of heavier-than-air aviation accident reports. In 2002 all large air tankers were grounded after two of them had wing spar failures a month apart. Both were large, 4-engine ex-military airplanes. Five days ago the FAA proposed an AD on Piper wing spars because the wings keep falling off. $\endgroup$ – user36228 Dec 26 '18 at 1:01
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    $\begingroup$ Lowell Bayles was killed in a Gee Bee racer in 1931 when the wing spar failed and the wing ripped off. In 2012 the EASA issued an AD on the A380 because of cracking in the wing spars after they “found cracks in almost all of the planes inspected”. This is a straightforward question with a simple answer. All airplane types and sizes have the same major mode of structural failure due to stresses imposed by the force known as "Gs". $\endgroup$ – user36228 Dec 26 '18 at 1:01
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G forces are forces caused by the acceleration of a mass. The one acceleration all parts are subjected to all the time is gravitational acceleration, and here John K's answer gives the right direction.

However, there are other accelerations at work which might cause higher loads still. Any fast, cyclic movement will cause accelerations which can become higher than those of gravity, especially when the acceleration is vertical so gravity comes on top. Obvious candidates are:

  • Flutter: Here, certification requires the mass balance of control surfaces to withstand 24g (JAR 23.659). That does not mean that in every flutter case this acceleration is reached, but that there have been cases where a stronger mounting of the balance mass could have prevented an accident. In case of flutter, the concentrated mass of the mass balance could be ripped off if not adequately secured to the control surface, rendering it ineffective.
  • Imbalance: This could be the rotating part itself (propeller, engine) or some structural member which is excited at one of its eigenfrequencies. Especially in helicopters, some vibration and shaking is always present and will create local stresses which can easily surpass those of gravity if a part is not well balanced. Repeated, cyclic stresses will let the vibrating part accumulate creeping damage until it breaks suddenly and unexpectedly.

Excuse my use of technical terms - please copy and paste the answer into Google Translate if you need help.

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