hulksmashley said:
Agayek said:
[
That's not how it works. Any given wingspan has a maximum amount of lift it can generate. If the plane and contents together weighs more than that maximum amount of lift, it will fall.
It's a simple fact of aerodynamics, you can't make a plane that can take any weight. All you can do is make a plane and make sure people know what the weight tolerance of it is.
Craorach said:
Umm.. No?
Why do you think things like elevators, buses and even buildings have max capacities? As far as I know, there's no substance or design on earth that can "hold up however many people we want to regardless of weight".
Even less so for a plane.. you're suggesting that the designers should basically be able to create a plane that will stay in the air no matter what the weight fitted into it. Do you have any limits for this? Should every passenger and crew member be allowed to fill their pockets and luggage with the heaviest weights they can fit in?
That is not how the general process of engineering design works.
You calculate a maximum possible force that could be applied to the object/design. There are limits on this. Only so many people can fit on a plane. Only so many people can fit in a building. Only so much water can go down the river. Then you multiply this theoretical maximum value by a factor of safety. For example, the dead loads (Concrete, flooring, doors etc.) on a building get 1.4, the live loads (people) get 1.6 etc. Then you design the object to fail at this value.
So an engineer designing a plane would determine the maximum amount of weight that the completely full plane could possible carry, then you make it 40% bigger, then you design the plane to fail at that. I don't see how it could possibly be off enough to fail, just because the people are heavy. They're not adding enough additional weight to overcome any reasonable factor of safety.
I don't know. I"m not an expert yet. Maybe your right and airplane engineering design is totally different from the type of engineering design I've learned. I'm willing to admit most of my knowledge comes from learning about designing civil works, which are generally much less tolerant towards failure. I'm also wiling to admit that this knowledge comes from a classroom. I'm a month and a half away from getting my Civil Engineering degree. Maybe a full on licensed practicing professional engineer knows more. It just doesn't make any sense to me.
You're neglecting a problem very specific to aircraft design:
Fuel loads.
The maximum amount of fuel onboard an aircraft can in many designs often be 50% of the maximum weight at take-off.
(A plane can actually fly with more weight than it can take off with - not practically useful, but relevant if you do mid-air refuelling for instance.)
If the total weight of an aircraft exceeds the maximum take-off weight, it will never get off the ground.
But, since you have to take the weight of the fuel into account, you get the following:
Maximum safe takeoff weight = weight of plane + weight of cargo + weight of fuel
unfortunately, the required amount fuel is also proportional to the total weight.
So... More weight (including more fuel weight, to an extent), means higher fuel usage.
To increase the payload weight, while keeping the range the same, you first have to increase the lift. This makes the plane heavier (both heavier payload, and heavier structure). You now need more fuel to move the plane. Which means bigger fuel tanks, and more fuel. But both of these increase the weight, and then you have to increase the lift again to compensate... In a kind of endless circle until you reach the physical limits of materials and construction.
What's actually happened in many cases, is that aircraft designers have created a trade-off.
They fit aircraft with fuel tanks that, if full, contain too much fuel to get the aircraft off the ground if it also has a full payload.
So, the plane gets 3 ratings:
Maximum fuel capacity,
Maximum payload capacity,
And maximum takeoff weight.
Where the empty weight + maximum payload + maximum fuel > Maximum takeoff weight.
This gives you operational flexibility because you can trade range for payload...
But it does mean you have to calculate your payload weight, and reduce the amount of fuel you carry accordingly.
And it just so happens that the smaller the aircraft, the larger the discrepancy.
So, these kind of accidents happen not so much because the passengers are too heavy, but that the weight of the passengers hasn't been calculated properly, and too much fuel was put in.
The only way to make this impossible, is to ensure the fuel tank is so small that no possible load that fits inside the body of the aircraft could overload it.
The downside to this, is the loss of operational flexibility. It's range is now limited to whatever distance it can fly at maximum possible load. Where before you could trade these off against eachother.
(And for efficiency reasons, you only usually take the absolute minimum amount of fuel you need for a given flight. - The weight of the fuel is expensive to carry if you don't need it.)
(Although in general it does seem to show that the ratio of internal volume of an aircraft to it's lift characteristics is such that it cannot fly if it's internal volume is filled even with something below the density of water.)
Could an aircraft be designed to be impossible to overload? Maybe. But such a design would probably be unacceptably inefficient, and very problematic operationally.
If we're going to have non-racist terms, we need to at least define them first. African-American doesn't mean jack to Brits or Aussies - and we still think of Amerindians(?) as Red Indians...without knowing whether that's racist or not.
