LMC

[nobbyknownowt]

Does anyone have the reference to the limits for LMCs for fuel, freight and pax. I seem to think its 0 300Kg or 3 pax respectively unless you specify differently in your manual.

cheers
Nobby

[L1011effoh]

Originally Posted by nobbyknownowt

Does anyone have the reference to the limits for LMCs for fuel, freight and pax. I seem to think its 0 300Kg or 3 pax respectively unless you specify differently in your manual.
cheers
Nobby

I'm pretty sure it must be dependent on type and company policy. It's 600kg change in zfm for me, no breakdown specified.
regards

[FougaMagister]

I confirm: it's not only company-dependent, it's also type-specific. The crews should know what the max LMC is for their respective aircraft, since dispatchers handling many different a/c types and airlines during one shift might get a bit confused.

Cheers

[On-MarkBob]

It's definately mostly type specific and thus how tolerant the aircraft is to a change in load and C of G. The aircraft I fly is 2000Kgs. nominally, but you have to use your loaf! If someone just loaded 2 tonnes in the No1 or No 5 hold I think I would do a new load sheet regardless or at the very least a new drop line. You should also use a little more caution when using standard weights and compartmented load or container data. Sometimes this data can be quite away out. So cover your back, if there is a niggling of doubt do a new load sheet.

[Too Few Stripes]

In my company it's a max LMC of 500kg, BUT you cannot LMC fuel of any amount. These limits apply to both our Boeings and Airbus's.

HTH,


TFS

[nobbyknownowt]

Yes I understand its type specific etc etc, however, where does the number come from, did someone just make it up or is there a guideline somewhere that they work from?
You know something like at the extremes of trim a 3% change in SMC% is ok so calculate the weight at the front or back that wil make the 3% change and thats the LMC limit for the type!!
cheers
nobby

[On-MarkBob]

When I used to fly the A320, I spoke to a pilot at Airbus about loading. The company I used to work for at the time were trying to 'invent' their own rules, so we kind of fell out over it and I left. The Airbus Guy was really helpful over the matter. Basically, no-one knows the aircraft better than those who made it, not just because they made it but because they get feedback from all the operators. The operator can propose what they like, but to become an operating proceedure contrary to that of the manufacturer, then they would ask the manufacturer if they can do it. If the manufacturer agrees then an ammendment to the Ops manual will be drawn up and sent to the Authority for approval. If the Authority has no objection then they rubber stamp it and we then comply with the requirements of the manual. So in answer to your question, it is most likely that the manufacturer is responsible for the requirements to uphold, but in any case wherever it comes from they would have been involved at some time. Even if the Authority was the first port of call, it is doubtfull they would approve an amendment that effects the aircraft loading without first contacting the manufacturer.

[john_tullamarine]

Simpler than that, chaps.

Totally dependent on the whim of the person designing the load system and the manner in which the error analysis is done. That is, there is no reason why two similar aircraft couldn't have a (not significantly) different LMC setup.

Re loading system design in general, there is nothing sacrosanct about how things are done .. and often personal or corporate preference dictates the layout. In particular, there is no problem with raising a system materially different to that used by the OEM in the weight control manual (by whatever name known) .. I've done just that in designing trimsheets on numerous occasions .. just a matter that my philosophies differ from the OEM guys'.

Provided that the sheet is well designed, there is no problem using LMCs .. except that the stab trim is going to be a bit more in error. Then again, if we are looking at only, say, one loading station, the trimsheet lends itself to going back up to the trimline ... correcting the loading .. and then dropping back to the envelope.

As to the interaction between loading system designer, OEM, and Regulator .. that may differ between jurisdictions.

.. and please don't deify the OEM folk .. they can make as many mistakes as anyone else in the game .. in my current role, I spend a moderate amount of time arguing with both airframe and engine OEM representatives ... I don't always win the argument .. but it's always good fun. Basically, when it comes to hard design and test data, the OEM is a very valuable source of information .. but, for routine engineering work, they are just one more source for the number crunching.

[nobbyknownowt]

Fantastic, Thanks John