Kabul C-17 - MAUW

[tartare]

A technical question for you all if I may.
Do heavy aircraft such as airliners or the C-17 use the weight on wheels sensors to measure the actual all up weight of the aircraft in real time, and then display that figure on the flight computer, EFIS thingey in the middle of the instrument pedestal?
Would the Commander of Reach 871 have been able to watch a scrolling figure of the weight of his jet increasing by the second as people rushed up the ramp?
Or would he just rely on coms from his loadie saying `we've got roughly 800 pax on board boss' (they thought it was 800 rather than 600 at first) and do a quick mental calculation to get his MAUW on the spot?
Average pax = 200lbs, x 800 = 160,000lbs of human cargo.
The C-17 can carry one M1 Abrahms - weighing in at around 140,000lbs...

[Genghis the Engineer]

No, WoW sensors are basically yes/no devices that tell the computers if the aeroplane is airborne or not, they don't actually measure the weight.

Calculations are done by dispatchers and/or crew for any large aircraft to determine the TOW.

Attempts have been made to design devices that determine weight, but it's basically futile because any wind whatsoever will muck up the numbers through lift on the wings.

G

[TURIN]

Some of the more modern aircraft are able to use wow sensors and other devices to calculate CofG and give an indication, but as far as I know total weight cannot be calculated.

[Mogwi]

Yes, 747-400 would tell you AUW and CofG but it wasn’t used for performance as “standard weights” were used for the load sheet. Made little difference as I seem to remember that it was something like 10tons/knot on take-off speed.

Mog

[tartare]

No, WoW sensors are basically yes/no devices that tell the computers if the aeroplane is airborne or not, they don't actually measure the weight.

Calculations are done by dispatchers and/or crew for any large aircraft to determine the TOW.

Attempts have been made to design devices that determine weight, but it's basically futile because any wind whatsoever will muck up the numbers through lift on the wings.

G
Indeed - hadn't thought of that.
Thank you all.

[Sleeve Wing]

tartare;11098281]
Average pax = 200lbs, x 800 = 160,000lbs of human cargo.


Perhaps a little pessimistic, tartare ?
I seem to remember that Average passenger nominal weights were something like - Males 85Kg, Females 70Kg, Children 25Kg and babes-in-arms ignored.
Surely this would make the Pax load (human cargo) more realistic and thus, in the C17 case, more possible?
Turin. WRT your suggestion that only modern aircraft had CG sensors, the DC9 of 50 years ago had a trim sensor on the noseleg which could give an automatic CG indication for the takeoff trim setting. Always confirmed from the loadsheet though. :ok:

[1208]

the vanguard had sensors to determine weight, in the cargo aircraft I worked on they were never consulted by the crew They just used the load sheets given to them.

[wiggy]

Yes, 747-400 would tell you AUW and CofG but it wasn’t used for performance as “standard weights” were used for the load sheet. Made little difference as I seem to remember that it was something like 10tons/knot on take-off speed.

Mog

Must have been a customer option, Mog, ours didn’t have a facility to measure AUW.

[B2N2]

Considering these are not overindulging Westerners rather people trying to survive the average weights would be closer to 150-160lbs for a pax weight of 120-128,000 lbs which is well within the 160,000lbs useful load of the C17.

[tdracer]

747-400F and 747-8F have an optional aircraft weight measurement system that can be used for determining dispatch.
No idea how many operators have it or actually use it as the primary indication of takeoff weight and CG.

[Shackeng]

https://www.sawe.org/papers/0506

We had this fitted to a 707 I was flying in the ME some years ago. AFAICT it seemed fairly accurate. If I recall correctly it provided wt and C of G, which as we had no idea what our employer (Sheikh) had put on, was, apart from eyeballing, was what we used for calculations.

[bitsleftover66]

A technical question for you all if I may.
Do heavy aircraft such as airliners or the C-17 use the weight on wheels sensors to measure the actual all up weight of the aircraft in real time, and then display that figure on the flight computer, EFIS thingey in the middle of the instrument pedestal?
Would the Commander of Reach 871 have been able to watch a scrolling figure of the weight of his jet increasing by the second as people rushed up the ramp?
Or would he just rely on coms from his loadie saying `we've got roughly 800 pax on board boss' (they thought it was 800 rather than 600 at first) and do a quick mental calculation to get his MAUW on the spot?
Average pax = 200lbs, x 800 = 160,000lbs of human cargo.
The C-17 can carry one M1 Abrahms - weighing in at around 140,000lbs...


Nope, the WOW switches are basically dumb switches that have a binary output, weight on or off, nothing in between. Under normal operations, freight would be weighed and PAX estimated using a standard formula. Under these kind of operations, I would think emergency authorisations would be in place based on relative risk. As you stated correctly, the C-17 can easily lift an Abrams tank and more (the C of G being the main limit on that baby), 6,7 or 800 people with more headroom than first class was well within the aircrafts lift capability.