One of the “local” airlines we took in Costa Rica weighed each passenger and his/her luggage. So, while my (oh-so-nice) team-mates got to hear my weight and laugh at it (yeah yeah I’m heavier than I look, darnit, these thighs are muscle)… I, in turn, got the last laugh when each of them had a higher “total weight” than I did
The procedure, as has been mentioned, should be the same as for overbooking: ask for volunteers, offering an incentive. One of my last flights to the US was overbooked and the guy who got left off was real happy because he was getting a free hotel room in a nicer hotel than he’d been staying in, 24 extra hours in Madrid and a nice wad of cash - and it was an 11am flight, so he could actually do something with the time and cash.
A side story, I was on a flight where I was near the front. A request was made for a passenger to go to the back during takeoff. I accepted, not being a fat person, I got a dirty look from the female flight attendant who made the request, who looking back was looking for a fat person to make that offer. After ignoring me for 2 seconds (which I assume she was hoping a fatter person would take up the offer), she accepted it. As I went back I noticed that the further back I went the fatter the passengers.
Now I have no idea when the airline sorted by weight but it was obvious, and hard feelings or not laws of physics are what they are and would have felt much safer if they made a anoucement that we need more fat people in the rear to takeoff safley.
The thing would be in parallel to the spring and would take no load. Heck, you can do it by having a thin magnetic rod attached to the bottom that goes through a tube attached to the top. Though they never actually touch you can identify displacement. Thing could probably be done for $50 plus labor (or a nice robust one for a little more). The only reasons I can come up with are that the suspension might not have enough motion from small loads due to friction (you might only be accurate within a couple hundred pounds) or that the suspension wears fast enough that it is not repeatable and would need to be calibrated after every landing.
It seems like it would be a paticularly good idea with today’s modern automatic control systems that depend heavily on knowing the stability derivatives that depend upon CG location.
Chicago Midway is a very old airport, built back in the day of prop plans with low take-off speed, and is hemmed in so that it can’t really go further expansion. This, combined with the often deleterious environmental conditions in Chicago, limits the conditions and load weights of aircraft. While I’m not familiar with the specifics of Chicago Midway, I do have some passing familiarity with take-off restrictions for military cargo aircraft from a few remote locations (Kodiak, Kwajalein, Wake) and wind and temperature conditions can be a real concern when taking off with near-rated load. Even with the built-in safety margins, if there is any doubt, they don’t fly.
Wind conditions may dictate approach vectors (i.e. north versus south). A strong tailwind from one direction can make landing and taking off in that direction hazardous, and strong crosswinds across a runway may peclude a safe landing, and the flight will be cancelled or diverted. (This happens a lot at high altitude airports where the reduced air pressure can result in mushy handling to begin with. Don’t even bother trying to fly into Flagstaff, AZ, for instance, unless the conditions are pristine.) Under normal conditions aircraft don’t require a headwind to land; however, on an aircraft carrier, most winged aircraft do require a significant headwind to land; this is achieved not by relying on the wind, but making your own; that is, turning the ship (and indeed, the entire carrier group) into the wind and steaming ahead at nearly full speed. (Launching and landing operations on a Nimitz-class supercarrier, for instance, are conducted at 25+ knots.)
I can think of a couple of reasons; one is that you’d have to retrofit this onto existing aircraft, and it would have to be robust enough to survive environmental and high impact loads, yet precise enough to measure the small fractions total mass distribution difference. (As previously noted, the live cargo weight of the plan is a small fraction of overall mass.) Another is that over time and with temperature change the suspension components will change their mechanical and response properties, which will again change readings; either you’d have to account for this somehow or the change in loading characteristic would have to be larger than these mechanical changes. A third is that if you’re going to use this system to provide critical flight data, it needs to be redundant and essentially infallible. Anyone who has played with LVDTs and strain gauges will tell you that they are in fact far from foolproof. So it would end up being either something that would require regular maintanence and calibration, or at best a backcheck against the loading plan.
Given the slim profit margins in the commerical aircraft industry, the hefty safety margins built into commerial airliners, and the cost of a development program of a landing gear/suspension program to make this sufficiently reliable (versus using essentially the same landing gear design on every airliner, which is essentially what is done now) it’s probably deemed not worth it. I wouldn’t regard it as practically infeasible, but it’s doubtful you could justify the cost when a rule-of-thumb measurement of the cargo and passenger weight should suffice. A design to do this wouldn’t be the $50 strap-on unit that flight estimates (heck, a simple stainless dowel pin per NAS spec will probably run you more than that); it would more likely add $10k+ per plane, not counting development costs, calibration, and maintanence. Mind you, that’s a pittance compared to the overall cost of the plane, but without a pressing need for it, I don’t see it happening.
An easier and cheaper solution, were it so desired, would be to have static load cells placed into the tarmac that the plane would back up onto as part of the gate egress maneuver. This would obtain an accurate estimate of weight distribution without concerns about the suspension system (you’d be measuring the entire weight of the aircraft too, not just the sprung weight), no modification to the aircraft, a robust and easily calibrated measurement device, and reduced cost (emplacement per gate rather than per aircraft). Since this isn’t done, save for vibration and dynamic testing of aircraft during development, I’d say there’s no perceived need to do so.
Planes often take off at a heavier weight than they can safely land with. On a normal flight that’s not a problem, since it will lose weight just from burning off most of the fuel. If there’s a problem and they have to land sooner, the pilot can open vents and jetison fuel to make the plane lighter. It doesn’t happen often, but it’s there if they need it.
I’d oppose any rule requiring the obese to deplane first because it seems too close to treating fat people the way black people were treated in Alabama in the 50’s. I’d be okay with a policy that offered financial incentives based on weight, such as ‘One dollar for every pound (body mass or luggage) that you take off the plane.’ Some might complain that this is reverse discrimination because fat folks would have more profit opportunity, but as I see it fat people suffer enough disadvantages already, so a little bit of increased opportunity for them wouldn’t be so bad.
Which is backed up by the rarity of crashes of commercial aircraft due to overloading and the apparent rarity* of passengers built like me being asked to take a later flight. Designers seem to use the model airplane rule of thumb “with enough power I can make a brick fly,” and at all but third-world airfields–and Flagstaff and Midway–it seems to work.
I like the scale idea, though pressure gauges on the air shocks run through a computer should work, and cheaply, if done right and that setup would also point out balance problems.
I can’t recall hearing anybody complain about it happening to them and NOBODY bitches like a fat person who refuses to accept the reality of their mass. The funny thing is that my own self-image has me weighing half what I do. Sorta anti-anorexia.
OTOH, general aviation aircraft crash because of overloading all the time. Kids, them things is made of tin-foil and balsa and most have barely enough power to lift themselves dry. Trust yer ol’ Uncle Drop, who’s had more than one friend fall out of the sky in one and more than one gen-av plane land nose-first in his company parking lot*, if God had intended us to fly He’d’ve given us 747s. Which He did so ride in one of them.
One sat in the airplane junk yard at the corner for years in the same attitude as when it was on the front page of the Chicago Tribune. I assume the sheep keeping the grass down licked Dad and Junior’s blood for the salt.
Weight would be a good tie-breaker if we assume all passengers were traveling alone.
However, if a party of 5 skinny bridesmaids volunteered to unload their luggage and take the next flight, it’d do more for the plane’s weight than kicking off 1 fatso.
Then again, you might base the decision of whom to debark based on the number of empty seats you have on the next flight. Sure, you can get rid of those 5 bridesmaids, but there’s no guarantee you’ve got room for them and all their luggage on the next plane outta Dodge.
The other problem is that some passengers planned well in advance for their flight, and others are last-minute types. Weight aside, if a passenger bought his ticket 2 months ago, he should have more of a right to expect that ticket than somebody who just rushed in and bought a ticket at the gate.
All things considered, I’d say weight is the last thing I’d consider, only if other factors are equal.
That would be the big one. They stick. It takes a lot to move an airliner strut. Often, after an airliner is let down after being on jacks, the struts will stay extended until they slowly settle down or someone goes up on the wing and jumps around a bit to settle them. There’s no way to reliably determine the weight by measuring the extension.
