Flight/Ground Ops, Crewing and Dispatch A forum for the people who are engaged in operational control/flight dispatch/crewing and their colleagues airside in ramp dispatch, load control and ground handling, to discuss issues directly related to keeping their aircrew and aircraft operational.

FAA ATPL test: CG shift in index arms

Old 18th Apr 2012, 11:46
  #1 (permalink)  
Thread Starter
 
Join Date: Aug 2002
Location: Switzerland, Singapore
Posts: 1,306
FAA ATPL test: CG shift in index arms

I'm stuck here with these W&B questions. I figured out the MAC part, but on the index arms I'm completly confused, since there is no real explanation in the theory book:

Q:
Where is the new CG if the weight is shifted from the forward to the aft compartment under Loading Condition WS-5?

A:
-97.92, +19.15, +13.93 index arm.

The theory book only gives you the explanation:
CG (index arm) = CG (inches of the Datum) - 580

The table is the good old one from DC-9:

Loaded weight 88 300 lbs
Loaded MAC 25.5%
Weight Change 3300 lbs

Fwd Comp centroid -227.9 Index arms
Aft Comp centroid +144.9 Index arms
Lemac -30.87 Index arms

Does anyone have a how to do?

Many thanks
Dani
Dani is offline  
Old 21st Apr 2012, 13:30
  #2 (permalink)  
 
Join Date: Jun 2002
Location: GB
Posts: 22
easiest way to solve it is using the equation;

weight to be shifted / total weight = Δcg / distance the weight is shifted

you are trying to work out the difference, which is the Δcg,

Δcg = ( weight to be shifted * distance the weight is shifted ) / total weight

we know the weight to be shifted is 3300 lbs,

the distance to be shifted is from fwd hold (-227.9) to aft hold (144.9), therefore the distance between these two holds is 144.9 plus 227.9, which gives us 372.8,

and the total weight is 88300 lbs.

so now Δcg = ( 3300 * 372.8 ) / 88300

Δcg = 13.93
pavil is offline  
Old 29th Apr 2012, 17:23
  #3 (permalink)  
Thread Starter
 
Join Date: Aug 2002
Location: Switzerland, Singapore
Posts: 1,306
Clever solution, thank you very much!
Dani is offline  

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information -

Copyright 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.