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I've often wondered if most passenger airliners have a CG envelope which would allow the CG of the airplane to be pushed outside the limits if enough passengers relocated to the front or back of the airplane.

If they do passengers might be surprised to know that if for some reason a lot of people got up and crammed into the back of the plane it might become uncontrollable.

If this is the case, the mental exercise could help illustrate how important an understanding of weight and balance is. It also highlights the importance of flight attendants as part of the air crew in their need to ultimately exert control over the crowd of passengers if the situation warrants it.

As a bit of background, I once wondered if Flight 93 during the September 11th attacks might have become uncontrollable because the CG shifted when passengers moved around the airplane. Although I once speculated that this could be the case, I am no longer speculating on the subject. I just want to mention that this is the scenario which made me wonder about the answer to the actual question. Since writing the original version of the question I learned about the CVR from Flight 93 and that it was intentionally flown into terrain by the hijackers.

ryan1618
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  • I removed the speculation with a tenuous link to the question since we will never know. – Simon Aug 09 '15 at 05:53
  • @Simon Actually, we do know and the speculation in the original post was definitely incorrect. Several of the passengers and flight attendants made cell phone calls and described what was going on (and learned about the earlier crashes.) Furthermore, the black boxes were recovered and showed the control inputs and recorded the cockpit conversations. – reirab Aug 09 '15 at 06:08
  • You guys marked it a duplicate when it's not. I asked if passenger movement can move the CG out of limits, not if it would make the airplane stall. – ryan1618 Aug 09 '15 at 06:45
  • I also think just deleting a whole section of my question is out of line, Simon. – ryan1618 Aug 09 '15 at 06:47
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    @RyanBurnette It's a community curated site. If you disagree, edit it back in. the community will decide. However, we do not welcome speculation of any sort. – Simon Aug 09 '15 at 10:15
  • Alright I added the background back in stressing that I am no longer speculating about the topic. I think it's appropriate for me to say that I once speculated and it is what lead me to ask the question. – ryan1618 Aug 09 '15 at 15:16
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    questions can be marked as duplicates also if the other question is not verbatim the same, but the answers there contain the answer to the closed one (as in this case) – Federico Aug 09 '15 at 15:30
  • @Federico fair enough – ryan1618 Aug 09 '15 at 15:34
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    Respectfully, I voted to reopen the question because in my opinion this question is sufficiently different from that of the question asking if passenger movement could cause a stall. The two questions have, again in my opinion, opposing answers. Looking at just the question titles, the practical answer to this question is yes, The practical answer to the question about causing a stall is no. In both questions, of course, you can think of extreme scenarios that would reverse those answers. – Terry Aug 09 '15 at 19:33
  • @ryan1618, I think it's a very intriguing question. I'm not an expert, but as I've found answers here unsatisfying, I've given it a shot at the question this is a "duplicate" of, you might want to have a look. Short answer: yes. – Fab May 02 '17 at 20:24

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I was on a flight in an SWA B737 that was mostly empty and the flight attendants moved us all toward the front. They told us it was for balance reasons.

I don't think this was a factor on flight 93. The CVR recorded the hijackers discussing what to do about the passengers. The hijacker piloting the plane asked 'Is that it? Shall we finish it off?' Another hijacker responded, 'No. Not yet. When they all come, we finish it off.' Then a few seconds later when it sounds as if the passengers are getting through the cockpit door he asks, "Is that it? I mean, shall we put it down?" The other responded, "Yes, put it in it, and pull it down." That's somewhat odd phrasing but those are translations from Arabic. It's clear that it was intentional.

TomMcW
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  • I wasn't aware there was a CVR from flight 93. Those are chilling details. – ryan1618 Aug 09 '15 at 04:37
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    Also, while I appreciate the info about flight 93, this answer doesn't address the actual question directly. – ryan1618 Aug 09 '15 at 15:18
  • Yes, i see that your question is about passenger movement in-flight whereas my experience was pre-flight. It does illustrate that the crew was concerned about passenger location in relation to cg. – TomMcW Aug 10 '15 at 14:30
  • I've also been on a mostly empty flight, where the pilot told us to not change seat until we were in the air because it would unbalance the aircraft. – Rolf Bjarne Kvinge Aug 16 '18 at 14:42