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I've just reached my destination after 33 hours going from one European hub to another. A journey which usually takes a max of 6 from leaving my house!

On the final leg of the journey, after boarding, the pilot asked for volunteers to leave the plane as they were too heavy to take off.

They had flown a 50 min flight from my final destination to where I was and, without fuelling, were turning around to go back. They were adamant that the plane was too heavy and (with a print out from one of the flight computers in hand) were asking for 27 people to leave the flight.

Is this possible? Because the MTOW of the aircraft is greater than the max landing weight, how could they have landed under max landing weight but now be too heavy to take off?

Maybe they flew with no passengers, but exceeded MTOW after adding more passengers and luggage?

Any suggestions for question re-phrasing or additional clarity are greatly appreciated.

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  • $\begingroup$ Can you give us the flight number and day? Or do you remember the type of aircraft? Also, are you sure they did not refuel? $\endgroup$
    – Bianfable
    Feb 11, 2020 at 16:48
  • $\begingroup$ How many passengers were there in total? 27 people isn't that many. But to your question, maybe this flight is limited by runway length or altitude so take off weight is lower than typical. $\endgroup$
    – user3528438
    Feb 11, 2020 at 16:51
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    $\begingroup$ Sure. To answer both questions in one post: LH2327, today (11.2.20) A320 Neo. I'd guess at somewhere around 120 people (two full bus loads). they definitely didn't refuel. They said they filled the plane in Munich the day before to give the plane more balast to cope with the storm winds. Departing Vienna I wouldn't have thought runway length would come into it. $\endgroup$
    – Phil Shackleton
    Feb 11, 2020 at 17:14
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    $\begingroup$ " They said they filled the plane in Munich the day before to give the plane more balast to cope with the storm winds" -- this is worthy of another question. Is this possible? What would be the benefit of more weight, in the context of strong wind? To increase the span loading and thus decrease the wing-bending stresses at the wing roots during gusts? To keep the plane from blowing over on the ground? Feel free to adapt any part of this comment into another question. $\endgroup$
    – quiet flyer
    Feb 11, 2020 at 18:46
  • $\begingroup$ It's a good question @quietflyer. I'm presuming increased stability but not sure. $\endgroup$
    – Phil Shackleton
    Feb 12, 2020 at 7:50

3 Answers 3

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The aircraft you flew on was D-AIUX, a Lufthansa Airbus A320-214. On 10 February it was scheduled to fly from Munich to London, but the flight was cancelled due to the storm:

Schedule (flightradar24.com)

If the aircraft was fueled for this flight the day before, it would need:

  • 3.13 kg/km x 944 km = 2.95 t of fuel for the trip
  • about 1.5 t of reserve fuel

After actually flying the 356 km to Vienna, it would have burned about 1.11 t of fuel, resulting in a total weight of:

  • 42.6 t OEW (Operating Empty Weight)
  • 3.34 t of fuel remaining
  • +any payload

The MTOW (Maximum TakeOff Weight) is 78 t, which would therefore still leave 32.06 t for payload, but the maximum payload is 19.9 t for the A320. So this cannot be the limiting factor.

It was noted that the runway could limit the takeoff. Your flight departed from runway 29, which is 3500 m long:

Departure in Vienna
(flightradar24.com)

The A320 only needs 2100 m at MTOW for takeoff, so this was also not the limiting factor.

You said "they filled the plane in Munich the day before to give the plane more balast to cope with the storm winds", which is not a procedure I am familiar with. Increasing the aircraft weight will increase its inertia and therefore make it less susceptible to wind gusts. Let us assume they completely filled all fuel tanks in Munich.

The A320 has a fuel capacity of up to 27,200 l. Multiplying that with the density of Jet A-1 (0.804 kg/l at 15°C), gives about 21.87 t. This would make the total weight before payload at Vienna 63.36 t, therefore leaving 14.64 t for payload. Now this is lower than the maximum of 19.9 t. Using standard passenger weights in Winter of 195 lbs = 88.5 kg, this would allow 165 passengers. The A320 exit limit is 195 passengers. It is therefore possible that some passengers had to leave the plane to get below MTOW.

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  • $\begingroup$ Awesome, thanks. I guess I could have low balled the number of people off, I was upfront so it was hard to judge and no one called the numbers out up front when we were discussing it. The filling of the plane with fuel thing might have been a red herring, one of the stewards said it, although they hinted it was to keep it more firmly planted on the ground during the storm, not to affect flight performance in any way. $\endgroup$
    – Phil Shackleton
    Feb 11, 2020 at 21:53
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    $\begingroup$ @PhilShackleton Ah, that's interesting. Airliners don't have tie downs and are usually parked outside, but I've never heard of an airliner blown away in a storm :p $\endgroup$
    – Bianfable
    Feb 11, 2020 at 21:58
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    $\begingroup$ @Bianfable, usually what happens is the airplane weathervanes around into the wind, rather than getting blown away outright. There are a few videos of this sort of thing floating around on YouTube. $\endgroup$
    – Mark
    Feb 12, 2020 at 1:01
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    $\begingroup$ @PhilShackleton MLW (Maximum Landing Weight) of the A320 is 66t, so that scenario would not have left much room for passengers, only 2.64 t or 29 standard passengers. $\endgroup$
    – Bianfable
    Feb 12, 2020 at 7:29
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    $\begingroup$ @Bianfable It can happen. Some aircraft are more vulnerable to it than others of course. youtube.com/watch?v=nWriy_XGXfc shows a tornado playing with 737s, the winds from the storm that blew over Europe last weekend were similar in strength... youtube.com/watch?v=nrl3ex7w6nA and another 737 sliding around on icy tarmac in strong winds while parked. Notice the luggage handler trying to push it back :) $\endgroup$
    – jwenting
    Feb 12, 2020 at 7:56
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Yes it is. While waiting for a delayed departure from Dusseldorf some years ago, the ambient air temperature rose enough during the delay to reduce the density of the air enough that the plane was overweight for takeoff. They fixed the problem by pumping fuel out of the plane to bring it back within max limits.

We then hit headwinds on the flight to LAX and were forced to make an unscheduled stop in Winnipeg to refuel the plane because had the flight continued, it would have been burning its minimum reserves prior to arrival.

No one on that flight was very happy.

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    $\begingroup$ It always bugs me when people are dissatisfied when their safety is being put first... $\endgroup$
    – Jpe61
    Feb 11, 2020 at 20:23
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    $\begingroup$ It didn't bug me, I'm just inquisitive. I offered to disembark and arrived in Munich via train before the flight which the volunteers were offered landed. Considering the circumstances I was a happy customer. It's more seeking more knowledge than questioning their course of action, they clearly did the right thing, I just want to know more. I'd have asked the pilot, but he was a bit busy. $\endgroup$
    – Phil Shackleton
    Feb 11, 2020 at 21:58
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That doesn't sound so much like that aircraft was over fueled but simply exceeding another metric called maximum zero fuel weight or possibly the maximum ramp weight. Refueling is not required to exceed this, if the aircraft is overbooked or has a particularly heavy load of passengers and/or cargo. I suspect this was the motivation on the part of the flight crew to make the decision they did.

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