Go Back  PPRuNe Forums > Flight Deck Forums > Tech Log
Reload this Page >

FAR 25.25 Minimum Weight

Tech Log The very best in practical technical discussion on the web

FAR 25.25 Minimum Weight

Old 19th Mar 2023, 05:39
  #1 (permalink)  
Thread Starter
 
Join Date: Mar 2005
Location: N/A
Posts: 5,821
Received 341 Likes on 180 Posts
FAR 25.25 Minimum Weight

Wondering why the limit, I can understand gust loads over stressing components, anything else?

FAR 25.25(b) Minimum weight. The minimum weight (the lowest weight at which compliance with each applicable requirement of this part is shown) must be established so that it is not less than -(1) The lowest weight selected by the applicant;

(2) The design minimum weight (the lowest weight at which compliance with each structural loading condition of this part is shown); or

(3) The lowest weight at which compliance with each applicable flight requirement is shown.
megan is offline  
Old 20th Mar 2023, 10:01
  #2 (permalink)  
Moderator
 
Join Date: Apr 2001
Location: various places .....
Posts: 7,167
Received 89 Likes on 60 Posts
Took the liberty of reopening your thread, good sir, missed it first time around.

Others may add additional considerations but the first two contenders which come to mind are

(a) gust responses - the lighter the aircraft the rougher it gets.

(b) Vmca has a problem with reducing weight due to the sideways component of the (reducing) lift vector reducing. One keeps in mind the bank limitation.
john_tullamarine is online now  
Old 21st Mar 2023, 06:04
  #3 (permalink)  
Thread Starter
 
Join Date: Mar 2005
Location: N/A
Posts: 5,821
Received 341 Likes on 180 Posts
Thanks John, I cancelled the post after finding the following link which only seemed to talk about CoG and fuel loading. I thought I was somewhat out of my depth, not knowing the ins and outs of the swept wing brethren. Thought there may have been parallels when I went on a 744 twelve hour scenic, no freight, no bags, just a full load of pax, had to carry two tons of ballast to keep CoG in place.

https://www.pprune.org/archive/index.php/t-361135.html
megan is offline  
Old 21st Mar 2023, 15:34
  #4 (permalink)  
 
Join Date: Apr 2004
Location: Dorset UK
Age: 70
Posts: 1,871
Likes: 0
Received 10 Likes on 7 Posts
The A300-B4 when converted to cargo had a minimum weight that required some ballast or ballast fuel when empty. This we were told was the lowest weight that the aircraft was test flown at and therefore any lower weight was outside the certification envelope.
This limitation meant that when flying from Sharjah to Stansted empty, a fuel stop was required as around 4 tonnes of fuel was ballast. It took a little while to get ops to understand that if we could load some ballast we could do it non-stop.
dixi188 is offline  
Old 22nd Mar 2023, 11:19
  #5 (permalink)  
Moderator
 
Join Date: Apr 2001
Location: various places .....
Posts: 7,167
Received 89 Likes on 60 Posts
The Design Standards (in this case, Part 25, either FAA or EASA) talk a lot about establishing weight limits for which the requirements of the Standards are met. Or, if you prefer, to show compliance with the Standards. To answer the question would need some knowledge of any particular certification program and so on. Not necessarily a simple exercise to establish an answer for any given Type/Model.

It took a little while to get ops to understand that if we could load some ballast we could do it non-stop.

Sometimes you just have to cry a little bit - we can but try .....

Routine loading system restrictions and considerations are in a different basket. For this story, we are concerned with whatever might be the limiting certification design issues ....
john_tullamarine is online now  
Old 22nd Mar 2023, 17:18
  #6 (permalink)  
 
Join Date: Apr 2014
Location: Europe
Age: 32
Posts: 137
Likes: 0
Received 0 Likes on 0 Posts
The CG position is also relevant here.

It's possible that an empty aircraft is at the limit of the acceptable CG range. If the designer were to "allow" an even lower weight, it may have to expand the acceptable CG range and doing so has all sorts of cascading consequences.
Central Scrutinizer is offline  
Old 23rd Mar 2023, 03:27
  #7 (permalink)  
 
Join Date: Nov 2010
Age: 56
Posts: 925
Received 0 Likes on 0 Posts
Originally Posted by Central Scrutinizer
The CG position is also relevant here.

It's possible that an empty aircraft is at the limit of the acceptable CG range. If the designer were to "allow" an even lower weight, it may have to expand the acceptable CG range and doing so has all sorts of cascading consequences.
Fokker 50 needed a few hundred kilos in the back on empty flights. Also, don't see a lot of Zappa fans your age...
hans brinker is offline  
Old 23rd Mar 2023, 11:59
  #8 (permalink)  
 
Join Date: Apr 2014
Location: Europe
Age: 32
Posts: 137
Likes: 0
Received 0 Likes on 0 Posts
Originally Posted by hans brinker
Fokker 50 needed a few hundred kilos in the back on empty flights. Also, don't see a lot of Zappa fans your age...
hehehe, might need to hide my age...
Central Scrutinizer 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

Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.