PPRuNe Forums - View Single Post - LMC
Thread: LMC
View Single Post
Old 9th Jan 2002, 05:54
  #8 (permalink)  
john_tullamarine
Moderator
 
Join Date: Apr 2001
Location: various places .....
Posts: 7,197
Received 111 Likes on 71 Posts
Post

Not quite as simple as that, good people.

The trim sheet (or whatever loading system is used) designer makes a number of assumptions which will differ between designers and between trim sheets devised by the one designer.

If the published trim sheet CG envelope replicates the AFM data (which is just about never the case) then the effect of LMCs can be judged by a simple correction working of the sheet.

However, the more general case is that the sheet envelope will be compressed for a variety of reasons and the extent of the compression will not be evident to the user.

Therefore, presuming that the sheet has been executed in the prescribed manner, it is not at all a straightforward matter to assess the effect of LMCs on the CG unless you know what considerations went into the design.

The following rules (however enshrined in your paperwork and manuals) must be adopted without any flexibility -

(a) complete the sheet in accordance with the prescribed instructions

(b) process LMC assessments strictly in accordance with the prescribed instructions.

(c) the specific numbers etc associated with one sheet have no relationship with those associated with a different sheet. This is sacrosanct. I have seen many and significant errors over the years which have arisen from the "but that is the way we do it on the other aircraft" mentality.

(d) if your particular airline has generated a sheet different to the manufacturer's data, then the recommendations and directions for use of the manufacturer's loading system contained within the manufacturer's manual may not be relevant to your company's data. That is ... use the instructions relevant to the particular system being used ...

[ 09 January 2002: Message edited by: john_tullamarine ]</p>
john_tullamarine is offline