If all the passengers ran to the back of a 'plane...
Discussion
Depending on the aircraft type and number of people, it would not be a matter of space at the rear of the aircraft, but of weight, and could result in a non retrievable condition.
The further aft away from the C of G. the less number of people (weight) would be required to destabilize the aircraft, so even a relatively small number of people doing this could put the aircraft in a non recoverable attitude.
If the passengers stayed at the rear the aircraft (even assuming the elevators were sufficient to counter the weight shift, which would not be the case) the aircraft would enter a nose high attitude so steep, the passengers at the rear would not be able to move forward through the cabin if they wanted to, even using the sides of the seats as a ladder.
The further aft away from the C of G. the less number of people (weight) would be required to destabilize the aircraft, so even a relatively small number of people doing this could put the aircraft in a non recoverable attitude.
If the passengers stayed at the rear the aircraft (even assuming the elevators were sufficient to counter the weight shift, which would not be the case) the aircraft would enter a nose high attitude so steep, the passengers at the rear would not be able to move forward through the cabin if they wanted to, even using the sides of the seats as a ladder.
I learnt a valuable lesson about tail tipping on the ground, having flown back from France in a Cessna 182 with a rear cabin full of wine.
When we arrived back in the UK, we both got out of the front seats only to discover that without our weight (and the weight of the fuel we'd burned en route) it was not enough to offset the weight aft. I should add that the weight and balance was fine in the air, just not so good once the two well built company directors had got out of the aircraft! Luckily, no damage was done.
When we arrived back in the UK, we both got out of the front seats only to discover that without our weight (and the weight of the fuel we'd burned en route) it was not enough to offset the weight aft. I should add that the weight and balance was fine in the air, just not so good once the two well built company directors had got out of the aircraft! Luckily, no damage was done.
Pan Pan Pan said:
Depending on the aircraft type and number of people, it would not be a matter of space at the rear of the aircraft, but of weight, and could result in a non retrievable condition.
The further aft away from the C of G. the less number of people (weight) would be required to destabilize the aircraft, so even a relatively small number of people doing this could put the aircraft in a non recoverable attitude.
If the passengers stayed at the rear the aircraft (even assuming the elevators were sufficient to counter the weight shift, which would not be the case) the aircraft would enter a nose high attitude so steep, the passengers at the rear would not be able to move forward through the cabin if they wanted to, even using the sides of the seats as a ladder.
The further aft away from the C of G. the less number of people (weight) would be required to destabilize the aircraft, so even a relatively small number of people doing this could put the aircraft in a non recoverable attitude.
If the passengers stayed at the rear the aircraft (even assuming the elevators were sufficient to counter the weight shift, which would not be the case) the aircraft would enter a nose high attitude so steep, the passengers at the rear would not be able to move forward through the cabin if they wanted to, even using the sides of the seats as a ladder.
Given that most people are capable of climbing a vertical ladder, why would they not be able to move forward through the cabin using the sides of the seats as a ladder? Surely it would have to be accelerating vertically at one hell of a speed for that to be the case?
Weirdly on an internal flight last week myself and one other seated in the wingbox area were asked to move to the rear seat rows prior to take off. I could understand myself having over 100Kgs would help with trim, but the other one to move was a tiny asian lady possibly 30Kgs wet.
I do wonder about risks with trim, especially if you have say a rugby club sat in the rear, with say the chess club sat upfront. I don't recall seeing anything in previous partners crew training manual about identifying that scenario?
I do wonder about risks with trim, especially if you have say a rugby club sat in the rear, with say the chess club sat upfront. I don't recall seeing anything in previous partners crew training manual about identifying that scenario?
Kermit power said:
Pan Pan Pan said:
Depending on the aircraft type and number of people, it would not be a matter of space at the rear of the aircraft, but of weight, and could result in a non retrievable condition.
The further aft away from the C of G. the less number of people (weight) would be required to destabilize the aircraft, so even a relatively small number of people doing this could put the aircraft in a non recoverable attitude.
If the passengers stayed at the rear the aircraft (even assuming the elevators were sufficient to counter the weight shift, which would not be the case) the aircraft would enter a nose high attitude so steep, the passengers at the rear would not be able to move forward through the cabin if they wanted to, even using the sides of the seats as a ladder.
The further aft away from the C of G. the less number of people (weight) would be required to destabilize the aircraft, so even a relatively small number of people doing this could put the aircraft in a non recoverable attitude.
If the passengers stayed at the rear the aircraft (even assuming the elevators were sufficient to counter the weight shift, which would not be the case) the aircraft would enter a nose high attitude so steep, the passengers at the rear would not be able to move forward through the cabin if they wanted to, even using the sides of the seats as a ladder.
Given that most people are capable of climbing a vertical ladder, why would they not be able to move forward through the cabin using the sides of the seats as a ladder? Surely it would have to be accelerating vertically at one hell of a speed for that to be the case?
Even if the passengers consisted entirely of fit young athletes, there would only be room for a small number to climb on the sides of the seats. The floor and overhead would give relatively few points of purchase for anyone trying to climb forward through a cabin at a steep, (if not completely vertical) orientation.
But significantly this is just nonsense, because an aircraft in this condition would have no more than a few seconds in which to correct its pitch angle, How many times have you seen fit young athletes free climb 60 to 80 feet in 3 or 4 seconds on something that is shaking owing to pre stall buffet?
It hopefully would never happen, but the most likely result would be a stall, but without the nose drop which occurs in an aircraft with correct/normal weight distribution. With a lot of weight at the rear, it is more likely a tail slide would occur, which would rip the control surfaces off the aircraft (The control surfaces are not designed, or built to cope with high airflow from the wrong direction) after which, what was left of the aircraft would descend at a high rate into the ground.
Simpo Two said:
In practice I don't think everyone could 'go to the back' because there wouldn't be room for them all.
It would not be a matter of the `number' of people, but of the weight of those moving to the rear of the aircraft, and whatever distance the distance aft of the c of G they are able to reach. So a relatively small number of people moving to the very rear of the aircraft could be enough to de stabilize the aircraft.No idea how this translates to real aircraft but RC aircraft usually have the CoG located a third of the way back on the wing. Moving it as far forward as the leading edge or as far back as the trailing edge makes the plane pretty much uncontrollable. Too far forward and the controls become really sluggish, too far back and it becomes twitchy as hell.
In fact I seem to remember planes like the Eurofighter have the CoG way back to make them more agile and a computer to sort out the inherent instability.
In fact I seem to remember planes like the Eurofighter have the CoG way back to make them more agile and a computer to sort out the inherent instability.
scubadude said:
m1dg3 said:
In fact I seem to remember planes like the Eurofighter have the CoG way back to make them more agile and a computer to sort out the inherent instability.
Yeah... and computers never go wrong...Not if say some other computer systems in the plane fail then it automatically enters a deep dive of death.
Isnt this more of a problem on the ground, in the air the lift of the wing and the tail stabilise the plane, it will make a difference but I dont think it would cause the plane to point skywards and stall, the back of the plane isnt the absolute rear, everyone would be between the wing and the tail, and 150 tonnes of people take up a lot of space, passengers can be dense, but they arent that dense so it wouldnt be like a 150 tonne weight hanging off the tip of the tail, some of that load is meant to be there anyway, i.e. the rear ten rows into which they would all have to clamber.
There is 20 tonnes or so of fuel in the middle of the plane, two massive engines, cargo, luggage etc, also, this wouldn't happen instantly like the Bagram cargo shifting, it would take time and be during level flight based on the question so wouldn't the flight computer just compensate or the pilot notice it and push forward on the stick to counteract ?
Scary thought, the Airbus model 911 !
There is 20 tonnes or so of fuel in the middle of the plane, two massive engines, cargo, luggage etc, also, this wouldn't happen instantly like the Bagram cargo shifting, it would take time and be during level flight based on the question so wouldn't the flight computer just compensate or the pilot notice it and push forward on the stick to counteract ?
Scary thought, the Airbus model 911 !
J4CKO said:
Isnt this more of a problem on the ground, in the air the lift of the wing and the tail stabilise the plane, it will make a difference but I dont think it would cause the plane to point skywards and stall, the back of the plane isnt the absolute rear, everyone would be between the wing and the tail, and 150 tonnes of people take up a lot of space, passengers can be dense, but they arent that dense so it wouldnt be like a 150 tonne weight hanging off the tip of the tail, some of that load is meant to be there anyway, i.e. the rear ten rows into which they would all have to clamber.
There is 20 tonnes or so of fuel in the middle of the plane, two massive engines, cargo, luggage etc, also, this wouldn't happen instantly like the Bagram cargo shifting, it would take time and be during level flight based on the question so wouldn't the flight computer just compensate or the pilot notice it and push forward on the stick to counteract ?
Scary thought, the Airbus model 911 !
I think your right. I've heard cabin crew let people move around on smaller plans after takeoff - but they are told to return to their allocated seats for landing.There is 20 tonnes or so of fuel in the middle of the plane, two massive engines, cargo, luggage etc, also, this wouldn't happen instantly like the Bagram cargo shifting, it would take time and be during level flight based on the question so wouldn't the flight computer just compensate or the pilot notice it and push forward on the stick to counteract ?
Scary thought, the Airbus model 911 !
I recall getting a sleazy flight with only a handful of people before they allocated the seats. They simply asked us to spread ourselves around and not all sit at the front.
m1dg3 said:
No idea how this translates to real aircraft but RC aircraft usually have the CoG located a third of the way back on the wing. Moving it as far forward as the leading edge or as far back as the trailing edge makes the plane pretty much uncontrollable.
In engineering/aerodynamic terms an RC aircraft is a real aircraft so translates pretty closely. The aircraft is basically balanced on the wing while flying so the C of G is somewhere on it. Look at a Tiger Moth. One seat between the wings and one behind them. When flown single handed it's always the rear seat that's occupied, the front seat is near enough on the C of G so you can have it occupied or not without upsetting the balance.I'll just leave this here as explains a few things
http://youtu.be/P_0R0eWOKns
Swept wing jets same principle but Cp is further aft due design and Mach Crit.
http://youtu.be/P_0R0eWOKns
Swept wing jets same principle but Cp is further aft due design and Mach Crit.
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