How many approximate 'g' can aircraft structure/aircrew withstand during flight?

Answer 1

It depends on what kind of aircraft and aircrew.

Normal category aircraft are designed to withstand 3.8G positive and 1.52G negative. Most have a lower limitation with flaps down.

Utility aircraft can go up to 4.4G positive and many aerobatic aircraft are stressed to 6G positive and 3G negative.

Some extremely aerobatic aircraft can withstand 9G positive and 9G negative.

During certification the aircraft must withstand 150% of the maximum loading for a few seconds and not have structural failure, but they are usually wrinkled and deformed after these tests.

Pilots must be fit and do special maneuvers to withstand high positive G unaided (typically tensing up lower and mid muscle groups and having the seat in a semi-reclined position. To withstand anything higher than about 5Gs, you need a G suit which uses a fluid to squeeze the lower body. Rapid of prolonged exposure to high positive G leads to tunnel-vision, grey-out, black-out, and loss of conciousness.

Negative G isn't as easy to handle because of the lack of large muscle groups in the head and the ridgidity of the chest cavity. Large amounts of negative G is accompanied by red-out and the bursting of small blood vessels.

Answer 2

That depends on the type of aircraft and the crew.

I have not personally flown F-16's, but I understand that an F-16 (and some other fighter jets) can sustain a structural loading of 8-9 g's for extended periods, but the pilot can only tolerate a few seconds of that even if they are wearing a pressure suit.

Most non-combat normal category aircaft (such as Cessna 172 and B-767) are designed to withstand a range of -2 to +5 g's for a few seconds without structural damage, but I can assure you that the crew and passengers can't handle that on a routine basis. The exact g load that the plane is capable of is specified in the Type Certificate. Planes certified for aerobatic maneuvers (eg Citabria) have higher G capability, and helicopters have less.

Most commercial pilots carrying passengers try not to exceed the range of + 0.5 to + 1.5 g's for passenger comfort, but cargo pilots have a bit more leeway, and they can safely operate between 0 and 2 g's. Commercial jets do not have 'g meters' to tell the pilot how many g's are being pulled, but g force is being recorded by most modern FDR's.

There have been cases of large commercial aircraft exceeding their structural limits, such as the Fedex DC-10 Flight 705 in 1984 which was hijacked and the China Airlines 747 Flight 006 in 1985 which stalled as a result of pilot error. Both of these aircraft managed to land safely but sustained major structural damage. As far as I know, both of these aircraft never flew again.

Answer 3

Most civilian aircraft have an g rating of +6 and -4. Aerobatic aircraft are a little high usually about +8 and -6. The MX-2 a High Performance Aerobatic plane can withstand up to +14 and-14 g's. All Military jet fighter like the F-16,15,18,22 are rated at +25 and -25, which is useless because the body can not withstand that many g's for a long peroid only about 2 seconds.

Answer 4

Depends on the particular aircraft and how old and stressed the airframe is.

As far as the occupant goes, I'm told the average human will pass out at a sustained 6G.
Ones tolerance will very, it is like weight lifting in this regard.

When I was a teen, I pulled 4G briefly in a C150 Aerobat, started to gray, and saw stars. Today I fly a Steen Skybolt and my G tolerance is very low. I need to fly more often and "G up" to rebuild my tolerance.
Karl
N400RF

Answer 5

Until they break. Either aircraft or crew or both. Limits are established for aircraft by the aircraft designers. Large safety margins are built in to achieve safety for unknown G's that might have to be experienced. 1 g is what the earth's gravity is. Most commercial aircraft are rated to 3.5 to 4 G's positive and close to 0 g in the negative.

Answer 6

General aviation airplanes can handle around 4g pretty easily.

The human body can handle varying amounts of forces depending on how they are applied.

Standing or sitting you can handle around 5g. A pilot in a pressure suit can handle about 9g. Higher amounts can be tolerated for a very short period of time. Negative g's are not as easily tolerated. -2 to -3 is the limit.

When lying down (on your back) you can handle up to around 17g for several minutes, but only 12g when lying on your stomach.

Answer 7

calnickel has my vote....good factual explanation