View Full Version : Self weighing capability / 767-300ER
skyhaze
25th Jan 2010, 22:59
Hi all,
I believe some (all?) AB aircraft are able to calculate their own weight once in the air.
I'd like to know if any Boeing aircraft have this capability as well, I'm specifically interested in the 767-300ER. Also, if so, then how precise are these calculations?
Many thanks.
Avenger
25th Jan 2010, 23:27
No.. Its a theoretical weight based on the figures put in the FMS before engine start. Zero Fuel Weight, Fuel Uplift etc. Remember we use standard pax weights and actual baggage weights, but we dont weigh carry-on luggage or the actual potatable water/ catering as these are taken from the tabulated DOMs, so at best it's a fairly accurate estimate.
Based on computed take off weight less the weight of the fuel consumed, (which is a fairly accurate figure). I guess on the 767 ER with about 200 pax, assuming you are 10kgs out on each pax weight, the figure is accurate +/- 2000 to 3000 KGs but with 136T Landing weight, we don't care!
mrdeux
25th Jan 2010, 23:33
The AB(380) uses the 'Weight and balance backup computer', which itself uses altitude, mach, alpha, elevator and trimmable tail position. It's used if both fuel quantity management systems fail, and supposedly provides data used to compute the flight control laws and to provide a warning against excessively aft cg.
767? No, why would it? It has real flight controls.
jettison valve
29th Jan 2010, 18:21
I agree with mrdeux.
The same goes for A330/A340. It^s calculated by the FE part of the FMGECs, if I remember correctly.
REgards, J.V.
Colin Oskopi
1st Feb 2010, 08:45
It is the FE and it not only can calculate the weight but the c of g as well using stab, thrust, angle of attack, altitude and config so long as you are flap zero and above roughly F140. That is an Airbus.
The Boeing I don't know, even the new ones still have some catching up on the 20 year old Airbus.
kuobin
1st Feb 2010, 11:06
Long before ,There were onboard weight and balance computer installed on B742 and early version of B744 ,they can figure out their own weight on ground, They use strain gauge type sensor to measure tiny amount of bend of wheel axle, but since those system were very unstable in windy condition ,eventually they all been deactivated.:)
eventually they all been deactivated.
I saw one which seemed to be working on an Atlas freighter a few weeks ago :ok: