Plane too Heavy

[AvNavCom]

I have wondered many times if newer transport aircraft have load cells in their landing gear so that they can for sure know what the weight and balance is when they close the doors. Seems like a no-brainer to just do that!

I've long wondered the same thing. If my dumb ass can go to a big-box store and buy a half-pound bathroom scale which will measure my weight, bone density, body composition, mood, sleepiness, and a solid guess at what I ate last night, you'd think it wouldn't be too much of a technological ask to have a reliable way to measure weight at each of the three landing gear points and do a bit of math for total weight and distribution. If I were the engineer, as soon as the aircraft got out of limits, the nose would start flashing like Rudolph's and an 'awuuga' siren would go off so everyone can point and laugh.

 

[dmspilot]

I thought most take off limits that affect passengers are due to heat with the associated reduced engine performance (single engine performance really). Is that correct?

Tim

That's rare as most airports where it gets that hot or have high DA also have long runways. At the regional we usually hit MLDW or MZFW. MLDW comes in to play especially when weather requires alternate airport(s), due to the extra fuel. It can also be a factor if the destination runway is short and has less than good braking action. I can't remember a single time I've been limited by MTOW.

 

[tspear]

That's rare as most airports where it gets that hot or have high DA also have long runways. At the regional we usually hit MLDW or MZFW. MLDW comes in to play especially when weather requires alternate airport(s), due to the extra fuel. It can also be a factor if the destination runway is short and has less than good braking action. I can't remember a single time I've been limited by MTOW.

Out of PHX, Vegas and Denver (of all places) I have been on regional jets that needed to remove people and fly with a few empty seats in an August heat wave. Since the flights were short duration (e.g. an hour or so), I always assumed it was something other MTOW, MZFW, MLDW. Since performance degrades with heat, my assumption when it is 115+ degrees out in PHX, it was single engine performance limitations. Hence my question.

Tim

 

[dmspilot]

Out of PHX, Vegas and Denver (of all places) I have been on regional jets that needed to remove people and fly with a few empty seats in an August heat wave. Since the flights were short duration (e.g. an hour or so), I always assumed it was something other MTOW, MZFW, MLDW. Since performance degrades with heat, my assumption when it is 115+ degrees out in PHX, it was single engine performance limitations. Hence my question.

Tim

Sorry, I said MTOW but I was thinking of PMRTW - Planned Maximum Runway Takeoff Weight. That's the number that would reflect the scenario you describe.

I don't fly in the southwest that much, it certainly can happen there as you said, though the other limitations I mentioned are more common.

 

[midwestpa24]

I've long wondered the same thing. If my dumb ass can go to a big-box store and buy a half-pound bathroom scale which will measure my weight, bone density, body composition, mood, sleepiness, and a solid guess at what I ate last night, you'd think it wouldn't be too much of a technological ask to have a reliable way to measure weight at each of the three landing gear points and do a bit of math for total weight and distribution. If I were the engineer, as soon as the aircraft got out of limits, the nose would start flashing like Rudolph's and an 'awuuga' siren would go off so everyone can point and laugh.

I used to think so too. It seems to be a simple solution.

But like so many things aviation, it's never that simple. The device would have to be regularly inspected, calibrated, and certified. Would you be able to MEL the weight sensors, or ground the aircraft if they show fault. You have to remember, we are talking Part 121 operations. Even a broken lav latch can ground an airplane. The manufacturers and operators aren't likely to add anything to an aircraft that doesn't directly save or make them money unless the FAA requires it.

 

[Larry in TN]

I thought most take off limits that affect passengers are due to heat with the associated reduced engine performance (single engine performance really). Is that correct?

That would be a takeoff performance limit but that rarely applies unless the runway is short, field elevation is high, and/or the temperature is hot.

The aircraft's max structural takeoff weight is usually not the limiting factor unless the flight is near the max range of the airplane.

Most commonly, takeoff is limited by the max landing weight. i.e. if you carried more weight you'd be too heavy to land when you arrived at the destination.

If my dumb ass can go to a big-box store and buy a half-pound bathroom scale which will measure my weight, bone density, body composition, mood, sleepiness, and a solid guess at what I ate last night, you'd think it wouldn't be too much of a technological ask to have a reliable way to measure weight at each of the three landing gear points and do a bit of math for total weight and distribution.

How are you going to account for the affect of the wind blowing over the airplane's lifting surfaces as you try to take a weight reading?

Bottom line, what problem are you trying to solve with the implementation of an expensive, possibly temperamental, system that adds weight to each and every flight? How often does the lack of such a system cause a problem in the real world?

 

[35 AoA]

Bottom line, what problem are you trying to solve with the implementation of an expensive, possibly temperamental, system that adds weight to each and every flight? How often does the lack of such a system cause a problem in the real world?

Agreed. We "measure" (by that, I mean the performance calculations, not necessarily the actual weight measurements) with a micrometer and cut with an axe in this biz I've noticed. Temp goes up 3 degrees from what was planned in the TPR, run new numbers, and v speeds might go up a knot or something. Can I reliably rotate at Vr +/-0 knots? Of course not. Bob and Martha in the back weighing in at 220 and 250 lbs aren't stopping the plane from flying. Even being off by a few thousand pounds, isn't gonna stop this train from climbing. Not saying to be cavalier with safety, but I'm saying that the fudge factor is enormous, even if we don't treat it that way.

 

[Mikey52]

And most airlines artificially limit their landing weight because landing fees are calculated by max landing weight. And most structural landing weights are limited by maintenance cost. In most cases the airplane can physically land at a higher weight but instead of say 10,000 cycles on a gear set at x weight, it might be reduced to 8000 cycles at x + 10,000 lbs. So the number of times that the increased weight is needed doesn't justify the increased costs.

 

[Kinder]

Agreed. We "measure" (by that, I mean the performance calculations, not necessarily the actual weight measurements) with a micrometer and cut with an axe in this biz I've noticed. Temp goes up 3 degrees from what was planned in the TPR, run new numbers, and v speeds might go up a knot or something. Can I reliably rotate at Vr +/-0 knots? Of course not. Bob and Martha in the back weighing in at 220 and 250 lbs aren't stopping the plane from flying. Even being off by a few thousand pounds, isn't gonna stop this train from climbing. Not saying to be cavalier with safety, but I'm saying that the fudge factor is enormous, even if we don't treat it that way.

Yes! The average weight is too low, the FAA knows this and the airlines know it too. So everyone looks the other way while the airlines fly overweight but the “numbers” say they are legal.

 

[Larry in TN]

And most airlines artificially limit their landing weight because landing fees are calculated by max landing weight.

I've flown for six airlines and all six used the manufacturer's maximum certificated landing weight. That is also what is used for the calculation of landing fees.

And most structural landing weights are limited by maintenance cost. In most cases the airplane can physically land at a higher weight

Max structural landing weight is a function of certification rules. The certification standard is that the airplane must withstand touchdown at 600fpm at max landing weight and 360fpm at max structural takeoff weight. 360fpm is still a pretty firm touchdown but a landing above MLW still requires a logbook write up and overweight landing inspection.

 

[tspear]

Yes! The average weight is too low, the FAA knows this and the airlines know it too. So everyone looks the other way while the airlines fly overweight but the “numbers” say they are legal.

Curious why you think so. I recall just a few years ago the "viral" video for a couple airlines "caught" weighing passengers. Airline representatives stated the scales are hidden as people enter/exit the gate/jetway, no one at the terminal can see the readouts, and this is required by the FAA.

How often the weights are updated, is again specified by the FAA.

Tim

 

[EdFred]

I'm 75% of that number...but that's as God intended. A lot of folks are way way over that.

I've been asked if I'm doing drugs or have cancer if I get below 195. I can't imagine how emaciated I would look at 150.

 

[Salty]

The ocd monkey in my brain asked me to ask you if you would edit the thread title and add the missing o

 

[luvflyin]

The ocd monkey in my brain asked me to ask you if you would edit the thread title and add the missing o

if it’s not two much work. How dew I do it

EDIT: ok, I did it

 

[Brad W]

I've been asked if I'm doing drugs or have cancer if I get below 195. I can't imagine how emaciated I would look at 150.

yeah I went through that too. People in our society are used to looking at the overweight and obese.

But part of my problem was that I didn't know what I've since learned. I didn't have good knowledge or guidance when I lost my weight, and in the process, lost it a little too fast and lost muscle mass along with the fat. I ended up with a case of "Ozempic face", even though I never took that drug. That 'look' is the root of a lot of these mistaken diagnoses of diseases or addictions.

Honestly, once I passed that weight as a growing kid, I NEVER would have thought I'd ever be <160# or have any reason to ever be in that range, but it turns out that's smack dab right in the middle of my suggested BMI range!

 

[EdFred]

yeah I went through that too. People in our society are used to looking at the overweight and obese.

But part of my problem was that I didn't know what I've since learned. I didn't have good knowledge or guidance when I lost my weight, and in the process, lost it a little too fast and lost muscle mass along with the fat. I ended up with a case of "Ozempic face", even though I never took that drug. That 'look' is the root of a lot of these mistaken diagnoses of diseases or addictions.

Honestly, once I passed that weight as a growing kid, I NEVER would have thought I'd ever be <160# or have any reason to ever be in that range, but it turns out that's smack dab right in the middle of my suggested BMI range!

The lowest I could get down to was 178. And I looked BAD. Like albino Ethiopian. At 200 I have no stomach. I'm also 6'3.

 

[Brad W]

I'm also 6'3.

That'll do it.
I'm 6 inches shorter, so what works for me would not work for you