How many G's on a 737?

[flapsforty]

Had a bit of a scare during a climb-out this week.
All kinds of metallic voices issued from the cockpit and it felt like we were dropping from the sky instead of climbing.
FA on the crew seat next to me started crying and so did some of the pax. On top of the ones that shouted.

So I figured it was time for some reassuring PA and did a spiel about how Boeing company in Seattle makes these really strong airplanes and how the 737 tolerates more G's than do any of us. Threw in a joke and had everybody grinning and rather relieved for what was a very bumpy ride.

Wondered to myself later how many G's a 737-800 actually can survive? Not a very important question, I know, but I'm curious..............
Anyone?

[Techman]

Normally airliners are certified to -1 to +2.5 when in clean config.
And 0 to +2.0 when dirty. Up to these limits no structual damage will/should occur.

I have seen an airliner, of similar size to a 737, that had been subjected to +4.5 G's, It was somewhat bent out of shape, but amazingly flew one more sector and everybody survived (except the licence of the engineer who released it).

So I guess the answer to your question would be....A LOT.

[McD]

Well done, Flaps, on reassuring your pax and keeping the situation under control with good PAs and humour. :)

About your question ... others have provided you the correct numbers, but you have to use those numbers in context. A range of +2.5g to -1.0g may not seem like a lot, but they are actually quite sufficient for the turbulence that your aircraft should ever encounter in flight. For instance, moderate turbulence, even though it may "feel" severe to persons in the cabin, will probably only put a force of about +1.5g on the aircraft. (That's not an exact number in every case, but it's a good approximation.)

Humans properly strapped into an appropriate aircraft can sustain forces of more than +10G. However, your quote, "... the 737 tolerates more G's than do any of us" could still be accurate if used in the context that the 737 will sustain the Gs of the turbulence much better (and receive less damage) than a non-seatbelted person. And, it's also fair to say that commercial aircraft can sustain the Gs of any turbulence likely to be encountered during flight (assuming good design, maintenance, etc. of the aircraft).

Here's a fairly informative website with turbulence definitions.
http://www.casa.gov.au/airsafe/trip/turbulen.htm

After reading the definitions, scroll to the bottom part: "Turbulence Related Incidents" and read about passengers who were injured inside, even though the aircraft sustained no (apparent) damage.

[john_tullamarine]

Just a few minor additions to the above ...

(a) the loads quoted are "proof" loads (more correctly proof load factors) .... which are the normal design standard expected acceleration loads to be experienced in flight and the maximum loads to which a pilot may intentionally expose the aircraft. It is all a bit of a statistical thing and these loading levels are not expected to be reached more than on the odd occasion. In this region of loading, the aircraft will bend and twist but return to the original shape when the loads are removed. The derivation of these minimum design loads accounts for

(i) the minimum design standard loads and, if higher,

(ii) any loads which the aircraft might realistically experience due to its particular design or flight characteristics. A longish aircraft might have a higher vertical load, for instance, to cover pitching capabilities and the resulting loads in the ends of the wee beastie.

(b) the structure is designed for, and tested to, a minimum 50 percent overload ("ultimate" load). In this region (proof to ultimate) the aircraft will/may experience minor structural damage but may not let go in a big way. During structural testing the normal requirement is for the structure to demonstrate that it can sustain the ultimate loading distribution for at least a three (3) second period.

(c) above the ultimate load factor is not a good place to be and catastrophic events might (and do) happen without too much warning. I can recall an accident some years ago wherein a hapless pilot apparently was emulating the feats of a well known ancient US pilot in a well known high wing cabin class twin when the said high wings, not surprisingly according to the subsequent analysis, departed from their respective fuselage attachments ...... whereupon the fuselage and its hapless passenger become a ballistic entity..... for a short while.

(d) while the loading spectrum a particular aircraft might experience historically may not be enough to break it as the timeline goes along, the effect on fatigue life is very significant. The structural design fatigue people make assumptions as to how the aircraft is likely to be used and the life cycle loading spectra to which it is likely to be exposed. These assumptions are then factored with a healthy padding margin and the sums done on cumulative fatigue damage ....... if an operator permits an individual aircraft to be operated in a manner significantly, and less conservatively different to, the manufacturer's assumptions, however ... all bets are OFF .... along with the wings or tail in due course ....

(e) the load factors which the human body can sustain vary significantly according to the body axis orientation of the load. Negative G is the most critical due to considerations of intra-cranial blood pressure and such like. Fore and aft loading is the least critical and, I believe, ultimately is limited by major blood vessel tearout strengths (I have seen figures up around 35G for aorta tearout ?) ... perhaps one of our medico contributors can elaborate with more technical competence ?

The current seat design standards reflect, to some extent, the practical physiological limits ....

[lomapaseo]

>Had a bit of a scare during a climb-out this week.
All kinds of metallic voices issued from the cockpit and it felt like we were dropping from the sky instead of climbing.
FA on the crew seat next to me started crying and so did some of the pax. On top of the ones that shouted.
<

I agree with the answers above about G's . and I'm not all that concern about upset passengers shouting. However I'm a lot more concerned as a passengerr behind the cockpit door about FA's crying and the sound of metallic voices from the cockpit in concert with the G's.

Turbulence is one thing and certainly within the experience of FA's, but was there something even more sinister going on?

[john_tullamarine]

On the subject of upset FAs .... I recall a period of very bad turbulence some years ago in Australia over the Strait. I was FO to an absolutely lovely chap with whom to crew (fondly known later as Captain Birdseed to those from that period) in the mighty F27 dogwhistle ....

We were on an out and return from Melbourne .... and got back home about 3-4 days later ... every time we saw Melbourne it was deemed more prudent to go somewhere else.

The point of the tale, though, is that the junior FA had only just been checked out to line .... and was, not to put too fine a line on it .... somewhere between terrified and quite considerably terrified ... as were we ... but it would have been poor form to show it ....

The senior, being a stalwart with much experience, looked after the cabin .. while we kept the younger girl in the jumpseat .... all she wanted to do was get home and never see another aeroplane again as long as she lived ... I think that, after this sequence, her colleagues talked her out of such a significant career change

..... and the pax were subject to more than a few "cheer up" PAs during the various flights it took for us to actually get back home .....

(I really must stop waffling on in reminiscences ....)

[flapsforty]

Thank you kindly for all the information.
Part of what keeps working in the cabin fun & rewarding over many years is learning more...........

Lomapaseo, where to start after reading your post? You are "concerned" as a passenger after reading my description? I am sorry to hear that, since the occurence wasn't all that unusual in cases where the turbulence not only feels heavy in the cabin but is afterwards cofirmed as being somewhat serious by the pilots.
As you can read in the post above mine.
(and no, as far as I am aware, nothing sinister had been going on. Wind shear is what the pliots told us over beers in Munich that evening :) )

Another little story to illustrate this.
6 or 7 years ago I was on board a 747-300 on it's way from Europe to Vancouver. Long distance, double cockpit crew.
Above Greenland I sat down for a wee chat with the captain, who was sitting in the upperdeck pax cabin for his rest period.
Suddenly the FSB sign came on and the unusual PA "CAbin Crew take your seats" emitted forcefully from the cockpit. Followed by a rollercoaster ride of epic proportions.
The captain grabbed my arm and never let it go, mumbling "Oh My God" for every dive, twist and upsurge we suffered.
The bruises on that arm stayed with me for weeks.

After it had all quieted down, we had 4 injured pax downstairs and a very sweaty smelling cockpit.
The lads had been unable to read their gauges and unable to control the aircraft. With he captain back in the cockpit, and both FE's very busy looking at old fashioned microchup readers, it was decided to land in Montreal for severe turbulence inspection.

The above to illustrate that reactions to turbulence can vary from person to person. And when you're strapped into a seat and can't do anything about the situation, emotions might take over.
These same emotions usually get swept under the rug as soon as action is required.
The captain in this story got back into his role as soon as he entered the cockpit and took command decisively and competently.
The FA next to me 3 days ago did a great job of lovingly calming all the scared kids on our flight once we were released from our crew seats.

It is exactly exchanges like this one which can improve all of our lives. I will print out the page that McD links to, and put it in her mail box next week. So that next time she will be a bit less scared perhaps.

[Herod]

For what it's worth, a 747 has been known to sustain 5g and still keep flying, albeit with bits missing. Likewise a 727 has sustained 6g and been in a fit state to land. Since your aircraft was presumably not overstressed, it was below 2.5g, although it probably felt a lot more. So the answer to you question is; a lot more than is ever likely to be encountered.