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

B777 folding wing

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

B777 folding wing

Old 23rd Feb 2018, 19:08
  #1 (permalink)  
Thread Starter
 
Join Date: Aug 2013
Location: PA
Age: 59
Posts: 30
Likes: 0
Received 0 Likes on 0 Posts
B777 folding wing

Not as dramatic as I had expected...

https://dms.licdn.com/playback/C5105...C0ooNAZfocXmyo
underfire is offline  
Old 23rd Feb 2018, 19:24
  #2 (permalink)  
 
Join Date: Jun 2002
Location: Geneva, Switzerland
Age: 58
Posts: 1,899
Received 2 Likes on 2 Posts
I might have missed something but how does the composite build of the wing minimize drag (as per the linked video)? Or is this a reference to something different?

It would seem that this folding wing precludes any wing tips, which seem quite fashionable these days. Any performance disadvantages?
atakacs is offline  
Old 23rd Feb 2018, 20:21
  #3 (permalink)  
 
Join Date: Dec 2012
Location: N/A
Posts: 72
Likes: 0
Received 0 Likes on 0 Posts
The modern wing on Boeing wide body aircraft does not have winglets. These A/C (B787, B747-800) do have raked(?) wingtips which substitute the winglets. According to Boeing there is no performance disadvantage.
LW20 is offline  
Old 23rd Feb 2018, 20:58
  #4 (permalink)  
 
Join Date: Feb 2002
Location: US
Posts: 108
Likes: 0
Received 0 Likes on 0 Posts
What about deicing the tips?! Wouldn't there be a significant risk of ice/snow/slush getting stuck in the mechanism? Any thoughts?
KingAir1978 is offline  
Old 23rd Feb 2018, 20:59
  #5 (permalink)  
 
Join Date: Dec 2017
Location: C120
Posts: 1
Likes: 0
Received 0 Likes on 0 Posts
Not after de-icing.
Looking forward to this. So are lamp posts and edges of buildings.
As said, the wing's perfect as it is - without winglets - not needed - it's just so damn big.
Jimbo2Papa is offline  
Old 23rd Feb 2018, 21:02
  #6 (permalink)  
 
Join Date: Mar 2014
Location: WA STATE
Age: 78
Posts: 0
Likes: 0
Received 0 Likes on 0 Posts
The original 777 was planned to have folding wingtips ( circa 1992-93 ), but at that time for a variety of reasons, the folding tip was dropped. at about that same time, winglets for 737 buisness jet was aborning, mainly for" looks" to differentiate from ' commerical' 737. Sort of like executive perks like chrome hubcaps. The agreement was that as long as it did not degrade performance and looked neat, winglets would be an option. Internal battles with certain aerotypes who were pushing a new wing for 737 at a horrendous cost eventualĄ resulted in a series of flight tests with winglets. And the results were such that they eventually became ( long story short) an option for new commercial 737. meanwhile back at the ranch, raked wingtips were aborning. And for long range commecial routes, the raked tips were perhaps a bit better than the winglets. But apparantly a significant redesign of the metal 777 wing would be needed to accomodate the raked tips.

Along comes the all ( mostly) composite wing, and along with better control via layup and molds of wing contours and smoothness, the raked wingtip could be accomodated- and because of airport clearances, the folding tip became practical again.
CONSO is offline  
Old 23rd Feb 2018, 22:02
  #7 (permalink)  
Thread Starter
 
Join Date: Aug 2013
Location: PA
Age: 59
Posts: 30
Likes: 0
Received 0 Likes on 0 Posts
Yes, I remember that option, but it was far more of the wing, 21 feet, that folded up. It was actually an option that no one purchased.

This folding wingtip seems like quite a bit of mechanism for the small portion that actually folds. One would think that this extra stiffness at the joint, at this part of the wing would not be helpful...
underfire is offline  
Old 23rd Feb 2018, 23:09
  #8 (permalink)  
 
Join Date: Jul 2013
Location: Everett, WA
Age: 68
Posts: 4,306
Received 136 Likes on 67 Posts
But apparantly a significant redesign of the metal 777 wing would be needed to accomodate the raked tips.
The 777-300ER/200LR have raked wing tips (the original 777 didn't). For the 777X, the wing span is long enough that it wouldn't fit in the same gates as the current 777, so the decision was made to go with the folding wing tip.
The folding wingtip offered on the original 777 was inboard of some of the movable aero surfaces - that caused major headaches. No moveable surfaces on the foldable surface on the 777X.
The Boeing Aero types claim the raked wing tip is more effective than winglets, but it necessarily increases the wing span - that would be bad news for the 737 for the gate size they often use, so they stayed with winglets to get the aero improvement with nearly the same span.
tdracer is online now  
Old 25th Feb 2018, 20:48
  #9 (permalink)  
 
Join Date: Jul 2012
Location: Around FL380
Age: 38
Posts: 107
Likes: 0
Received 0 Likes on 0 Posts
I think that the military 737 also comes with raked wing tip (span obviously longer) as it’s not limited to normal gates as to the commercial ones.
imriozer is offline  
Old 25th Feb 2018, 22:56
  #10 (permalink)  
 
Join Date: Dec 2009
Location: Southwater
Age: 73
Posts: 0
Likes: 0
Received 1 Like on 1 Post
Folding wingtips. XB-70 anyone?
RedhillPhil is offline  
Old 26th Feb 2018, 00:15
  #11 (permalink)  
 
Join Date: Nov 2015
Location: Mordor
Posts: 1,315
Received 45 Likes on 24 Posts
That was for trapping wave-lift at mach 3 while also addressing the transonic CP shift to reduce supersonic trim drag - doing what concord did by pumping fuel but addressing the fin area issue as well.
PDR1 is offline  
Old 26th Feb 2018, 03:46
  #12 (permalink)  
 
Join Date: Jul 2013
Location: Everett, WA
Age: 68
Posts: 4,306
Received 136 Likes on 67 Posts
PDR
According to a book I read on the XB-70, the wave-lift was intentional "miss information". The primary reason was that drooping the wings dramatically improved directional stability at cruise Mach speeds (although I wouldn't be surprised if did provide wave-lift benefit - at least according to that book it wasn't the primary reason.)
tdracer is online now  
Old 26th Feb 2018, 15:38
  #13 (permalink)  
Thread Starter
 
Join Date: Aug 2013
Location: PA
Age: 59
Posts: 30
Likes: 0
Received 0 Likes on 0 Posts
OT: a great video
underfire is offline  
Old 26th Feb 2018, 19:34
  #14 (permalink)  
 
Join Date: Nov 2005
Location: Potomac Heights
Posts: 470
Likes: 0
Received 0 Likes on 0 Posts
Seemed like an incredibly smooth landing to have blowouts. Was it at far higher than designed speeds? Or just crappy tires?
SeenItAll is offline  
Old 26th Feb 2018, 20:15
  #15 (permalink)  
 
Join Date: Sep 2016
Location: USA
Posts: 795
Likes: 0
Received 0 Likes on 0 Posts
Here's a comment on that video from someone who seems to know what he's talking about:

-Unknown to anyone, a wire in a junction box was accidentally pinched under the cover causing a short to ground.
-After takeoff, the landing gear was selected up but the hydraulics shut off because the shorted wire.
-When the hydraulic pump shut down the pressure was lost
and air loads on the unlocked gear caused it to drift rearwards into the door.
-the nose wheel tire was cut by the gear door.
-engineers on the ground gave instructions to the pilots where and how to jump a relay in the cockpit
to get the hydraulic pump started.
-Copilot use a paperclip and jumped terminals on a relay as instructed.
-Hydraulic pump started and pilot selected gear down, and the gear went back to down and locked.
-Aircraft landed normally but the anti skid system malfunctioned and locked some of the wheels
Vessbot 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.