weighing an airplane on a scale (for weight & balance)

[J777Fly]

For commercial aircraft, (passenger/cargo jets and props), by regulation, how often are they weighed on aircraft scales for weight and balance purposes?
And is this normally done in house by technicians or outsourced to commercial contractors?
And how long does take process take?

[JJink]

Originally Posted by J777Fly

For commercial aircraft, (passenger/cargo jets and props), by regulation, how often are they weighed on aircraft scales for weight and balance purposes?
And is this normally done in house by technicians or outsourced to commercial contractors?
And how long does take process take?

Here in US there is no requirement to weight an aircraft periodically but usually it is done when you are in doubt or after some major repairs, alterations, and modifications (or even a paint job) to find the new empty weight and more importantly the new CG. You can outsource it but normally it is done by the maintenance crew. The procedure will be in the Maintenance Manual.
here is a little more info

http://www.weighing-systems.com/Tech...tweighing.html

[sefro]

For on demand:
Sec. 135.185

Empty weight and center of gravity: Currency requirement.

(a) No person may operate a multiengine aircraft unless the current empty weight and center of gravity are calculated from values established by actual weighing of the aircraft within the preceding 36 calendar months.
(b) Paragraph (a) of this section does not apply to--
(1) Aircraft issued an original airworthiness certificate within the preceding 36 calendar months; and
(2) Aircraft operated under a weight and balance system approved in the operations specifications of the certificate holder.

I Cannot find one for part 121 or scheduled airlines but I am pretty sure that they have similar requirements. It is also correct that aircraft operating under part 91 do not require any updates on weighing except after major alterations where the weight additions cannot be accurately tracked.
Seth

[JJink]

Originally Posted by sefro

For on demand:
Sec. 135.185

Empty weight and center of gravity: Currency requirement.

(a) No person may operate a multiengine aircraft unless the current empty weight and center of gravity are calculated from values established by actual weighing of the aircraft within the preceding 36 calendar months.
(b) Paragraph (a) of this section does not apply to--
(1) Aircraft issued an original airworthiness certificate within the preceding 36 calendar months; and
(2) Aircraft operated under a weight and balance system approved in the operations specifications of the certificate holder.

I Cannot find one for part 121 or scheduled airlines but I am pretty sure that they have similar requirements. It is also correct that aircraft operating under part 91 do not require any updates on weighing except after major alterations where the weight additions cannot be accurately tracked.
Seth

Good call on that 36 calender months requirment. Never really had to do that but it is there. Here is the actual AC 120-27D


http://74.125.113.132/search?q=cache...&ct=clnk&gl=us

[Berkut]

Originally Posted by J777Fly

For commercial aircraft, (passenger/cargo jets and props), by regulation, how often are they weighed on aircraft scales for weight and balance purposes?

I can't recall exactly, it was something like 36 months though. It was specified in our approved manual.

And is this normally done in house by technicians or outsourced to commercial contractors?

Ours were in house. It's one of the simpler tasks.

And how long does take process take?

Couple of hours.

[v1valarob]

I always wonder how incorrect our weight calculations are. You have so many variables from the dust, sand, sodas, napkins, cups, amount of waste on the lav, magazines in the seats, etc.

Then you have the times where we have been literally 1lb under MTOW. Chances are in reality we are over the MTOW #. Im guessing some genius engineer has figured out all of this though.

[Berkut]

Originally Posted by v1valarob

I always wonder how incorrect our weight calculations are. You have so many variables from the dust, sand, sodas, napkins, cups, amount of waste on the lav, magazines in the seats, etc.

There are procedures for readying the airplane to be weighed. Usually fuel and lav tanks are emptied, oil and hydraulic reservoirs are filled, the cabin is cleaned and any non-aircraft stuff like magazines and drinks are removed. Of course, you can never get all the dust and coins and other trash out, but the results are fairly repeatable between weighings.

[JJink]

To find the new empty weight of an aircraft, the weighing procedures must be followed to the letter.

Normally the aircraft is defueled down to unusable fuel, all systems are serviced full (from O2 to engine oil), all required equipments installed, aircraft is cleaned off of all the bird crap and other grimes (whatever remains will become part of the new EW), all panels installed and all protective covers removed.

Regardless of the method of weighing used (jack cells or weighing platforms) the aircraft is then leveled. exact procedures to be followed for each aircraft will be in detail in the respective aircrat maintenance manual.

The Aircraft is weighted inside a hanger with the doors close (a slight breeze across the wings will lower the empty weight). Minimum of three readings are taken and then averaged. The new CG is calculated, the weight and balance sheet updated, and a proper logbook entry is made.

[trafficinsight]

to be honest with you I've never understood why it's not a requirement to weigh part 91 airplanes at least, like, once every 10 years or so...

[Roger, Roger]

Originally Posted by trafficinsight

to be honest with you I've never understood why it's not a requirement to weigh part 91 airplanes at least, like, once every 10 years or so...

Yeah...especially after you've seen the results of actually weighing them. At the old Flite Skool we did that and lost like 20 lbs of useful load on a Lance.

[trafficinsight]

Originally Posted by Roger, Roger

Yeah...especially after you've seen the results of actually weighing them. At the old Flite Skool we did that and lost like 20 lbs of useful load on a Lance.

That's about normal from what I've seen, airplanes, like people, just tend to gain weight over time .

There's one 172 I've flown that next time it's in for annual it's definitely getting weighed. I took the boss' neice, nephew and brother for a ride in it and though we were in C.G. and close to, but not over max gross, it scared the hell out of me. I've been close to gross before and even at gross without issues, but anemic doesn't even begin to describe this. Comparing the numbers later, it had 100lbs more useful load than any other 172 we have... I find that highly suspect. Rounding and math errors over 35 years can really make a difference!