What happens if the Pax rush to the back?

[phiggsbroadband]

Just seen the report of a nose-wheel collapse at Paris, which got me thinking...
As the main-wheels on nearly every aircraft are very close to the C of G, what would happen if all the pax went to the rear of the plane? Would the nose-wheel lift off the ground?
A typical scenario would be if fumes were seen coming from the cockpit end, which caused a panic.


With light GA aircraft or gliders, I know it is very easy to put the tail onto the ground with just the weight of one person.

[awblain]

100 200-pounders (9 tons) all 10m back from the main wheels in an A320? Versus 60 tons in total. CoG without the passengers has to be nearer than about 1.5m to the main wheels for it to tip.

350 200-pounders (32 tons) all 20m back from the main wheels in a A340-600, versus 300 tons in total. CoG without the passengers has to be nearer than about 2m to the wheels for it to tip.

I'd expect the nose wheels to be at least bearing 10% of the overall weight, so
with a 12.6/32m wheelbase, neither an A320/A346 seems likely to tip. I understand rear-engined aircraft can be more teeterey.

[DaveReidUK]

The Shorts 360 was prone to tipping on its tail if the load wasn't properly balanced.

On one particularly embarrassing occasion an aircraft being delivered to a new operator did just that, when the welcoming party all decided to board the newly-arrived aircraft via the rear door at the same time. :O

[phiggsbroadband]

Thanks for the reply Awblain, I have found a document on the web which relates to the weights on the ground of the wheels on 737s (say -700s.)
which seem to suggest the front wheel takes a max of 8000 kg at a distance of about 12m from the wheels. Compared with 10m to the rear exit.....


But it also goes on to say that it is dependant upon the CofG (baggage load + fuel etc) of between 10 to 35 % MAC. For the most rearward CofG (35% MAC) then only 6% of the weight of the aircraft is on the front wheel i.e about 3600kg. This would only need about 22 displaced pax to lift it.... If my calcs are correct...


The web doc...
http://www.boeing.com/assets/pdf/commercial/airports/acaps/737sec7.pdf
See Sect 7.4.8 pp 449


(looks like this post has been moved to 'Ground and other Ops Forum')

[foxmoth]

Certainly been a few occasions when aircraft without rear engines have tipped, IIRC we had to be careful on the B757 when boarding that you did not board all at the rear first.
Looks like the 737 could have the same problem
Sterling.jpg Photo by con-pilot | Photobucket (http://s28.photobucket.com/user/con-pilot/media/Sterling.jpg.html)

[Denti]

Saw the aircraft after this incident (http://www.skybrary.aero/index.php/B738,_Stuttgart_Germany,_2005_(GND_HF)), apparently it was a pretty bad idea to seat the remaining around 90 passengers in the back of the cabin and keep their luggage in the back as well. Didn't tip on the gate, however once they set take off power it did. Damaged several meters of fuselage and took several months to repair.

[Daysleeper]

If everyone rushes to the back the aircraft centre of gravity might go beyond the rear limit and cause control difficulties or indeed loss of control.

A fair number of cargo aircraft have been lost over the years to misload or load shift in flight ending up with too much weight at the back.

And to add to the 737 report below there was a UK A320 did a similar thing on the Greek Islands, tail strike on power application.

[foxmoth]

I believe this one
http://m.youtube.com/watch?v=4Z7GkV5DqOI&desktop_uri=%2Fwatch%3Fv%3D4Z7GkV5DqOI

Was put down to the cargo shifting aft.

[albatross]

There was a F-27 accident following an engine failure in Canada years ago in which, I seem to recall, one factor noted was that the well intentioned action of the cabin crew of moving all the pax to the rear of the cabin in anticipation of a forced landing put the aircraft out of the C of G envelope to the rear. This may have contributed to the loss of control - The crew were presented with a very difficult situation due to knock on effects of the initial engine failure and the movement of the pax was mentioned as a factor.

Quebecair Flight 255 - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Quebecair_Flight_255)

[CelticRambler]

Isn't the use of a tail stand strongly recommended (if not obligatory) when boarding passengers on an ATR42 due to the risk of tipping up?

[Dan Winterland]

Aircraft crashes after crocodile on board escapes and sparks panic - Telegraph (http://www.telegraph.co.uk/news/worldnews/africaandindianocean/democraticrepublicofcongo/8078612/Aircraft-crashes-after-crocodile-on-board-escapes-and-sparks-panic.html)

[zondaracer]

A Learjet pilot who experienced a nose gear failure in the US instructed his passengers to move to the rear part of the cabin, Airplane landed and came to a stop sitting on its tail with minor damage.