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

737NG questions

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

737NG questions

Old 30th Jul 2014, 17:12
  #1 (permalink)  
Thread Starter
 
Join Date: Jan 2000
Location: Not where I want to be!
Posts: 116
Likes: 0
Received 0 Likes on 0 Posts
737NG questions

Hi All,

I was asked two questions today and I didn't know the answer. I did a search on here but to no avail. So can you help?

1. On the 737NG why does the Airspeed Indicator on the speed tape show 45kts when stopped on the ground?

2. Why are the wings on the 737NG set at a sweep angle of 25 degrees rather than 27 degrees?

I even google searched this and no joy!

I look forward to your responses.

Many thanks.

Last edited by Busbar; 30th Jul 2014 at 17:12. Reason: typo error
Busbar is offline  
Old 30th Jul 2014, 18:05
  #2 (permalink)  
 
Join Date: Jun 2003
Location: The Netherlands
Posts: 246
Likes: 0
Received 0 Likes on 0 Posts
737NG questions

RYR interview? The answer to your last question should have been: "because the engineers deemed 25 degrees to be the optimal".
Puzzled by the first one though.
JeroenC is offline  
Old 30th Jul 2014, 18:10
  #3 (permalink)  
 
Join Date: Sep 2010
Location: England
Posts: 1,955
Likes: 0
Received 0 Likes on 0 Posts
Super critical wings.
Lord Spandex Masher is offline  
Old 30th Jul 2014, 18:35
  #4 (permalink)  
Per Ardua ad Astraeus
 
Join Date: Mar 2000
Location: UK
Posts: 18,579
Likes: 0
Received 0 Likes on 0 Posts
Puzzled by the first one though.
- because it does? It is generally thought that, Air France excluded, pilots will not try to fly conventional swept wing aircraft at less that 45kts.
BOAC is offline  
Old 30th Jul 2014, 18:43
  #5 (permalink)  
 
Join Date: Jul 2013
Location: Everett, WA
Age: 68
Posts: 4,357
Received 157 Likes on 75 Posts
Airspeed isn't valid below a certain value (the difference between total and static pressure is too small to be dependably resolved). Some Air Data Computers use 30 knots (that's what's used on 747/767 that I work), presumably on the 737 they use 45 knots.


When they went to the NG, Boeing didn't do a complete redesign the 737 wing, they did a 'reloft' where they changed the aerodynamic profile but not the basic structure. Since the 737 wing dates back to the 'short haul' airplane concept of the 1960s, there really wasn't much they could do to the wing sweep within the design constraints of keeping the same basic wing structure.
tdracer is offline  
Old 30th Jul 2014, 19:20
  #6 (permalink)  
Thread Starter
 
Join Date: Jan 2000
Location: Not where I want to be!
Posts: 116
Likes: 0
Received 0 Likes on 0 Posts
Many thanks folks!
Busbar is offline  
Old 31st Jul 2014, 07:04
  #7 (permalink)  
 
Join Date: Feb 2005
Location: Past the rabbit proof fence
Posts: 242
Likes: 0
Received 0 Likes on 0 Posts
Don't know why 45kts but maintenance manual for classic used to refer to 45 kts indication of serviceable air data computer.
aveng is offline  
Old 1st Aug 2014, 04:18
  #8 (permalink)  
 
Join Date: Aug 2009
Location: GPS L INVALID
Posts: 578
Likes: 0
Received 0 Likes on 0 Posts
I was told (always a bad way to start a sentence) that the NG wing was redesigned to allow for a higher cruise mach number - while the NG is obviously cruising somewhat faster than the classics supposedly Boeing wanted to raise MMO as well over its current 0.82. The problem this posed was that this would have required a complete airframe recertification... If this is true this would explain the relative speed instability of the NG in cruise - it definitely wants to fly at lower AOA!
STBYRUD is online now  

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.