Go Back  PPRuNe Forums > Aircrew Forums > Military Aviation
Reload this Page >

C5 and An-124 wings straighten in flight?

Military Aviation A forum for the professionals who fly military hardware. Also for the backroom boys and girls who support the flying and maintain the equipment, and without whom nothing would ever leave the ground. All armies, navies and air forces of the world equally welcome here.

C5 and An-124 wings straighten in flight?

Old 22nd Mar 2019, 13:06
  #1 (permalink)  
Thread Starter
 
Join Date: Mar 2019
Location: Zurich
Posts: 3
C5 and An-124 wings straighten in flight?

I see this every time C5 Galaxy or An-124 are on the tarmac - their wings are drooped significantly. Do they stay like that in flight or do they straighten out as they generate lift? I tried looking for videos on youtube but couldn't find the definitive answer. Could someone help, please?
ProPax is offline  
Old 22nd Mar 2019, 15:31
  #2 (permalink)  
ICM
 
Join Date: May 2008
Location: Bishops Stortford, UK
Age: 79
Posts: 416
I will happily give way to an aerodynamicist on this but, for what it's worth, and based on my time with the C-141 that also had drooped wings on the ground, they certainly straightened out as lift increased. And the effect of the weight of fuel in the wings should also be considered. I could touch the wingtip on the ramp before departure on a flight of four or more hours whereas, after landing, that wingtip would be way out of reach.
ICM is offline  
Old 22nd Mar 2019, 15:44
  #3 (permalink)  
 
Join Date: Mar 2005
Location: Kammbronn
Posts: 2,021
Originally Posted by ProPax View Post
I see this every time C5 Galaxy or An-124 are on the tarmac - their wings are drooped significantly. Do they stay like that in flight or do they straighten out as they generate lift? I tried looking for videos on youtube but couldn't find the definitive answer. Could someone help, please?
You should look for video of helicopter blades in flight.
diginagain is offline  
Old 22nd Mar 2019, 17:29
  #4 (permalink)  
 
Join Date: Apr 2004
Location: Richard Burtonville, South Wales.
Posts: 1,900
Don't they keep the weight in the wings for a while to avoid the single loud clap before the wings fall off? Wing relieving load or summat?

And is it BS that the BUFF has a call of, 'wings airborne' on the takeoff roll?

CG
charliegolf is offline  
Old 22nd Mar 2019, 17:53
  #5 (permalink)  
 
Join Date: Apr 2010
Location: Sneaking up on the Runway and leaping out to grab it unawares
Age: 58
Posts: 684
Originally Posted by charliegolf View Post
Don't they keep the weight in the wings for a while to avoid the single loud clap before the wings fall off? Wing relieving load or summat?
We certainly did on the C-130. At high fuel loads you'd use the AUX tank (wing shoulder tank) fuel before the EXT tank fuel; the latter providing the wing bending relief.

ExAscoteer is offline  
Old 22nd Mar 2019, 18:06
  #6 (permalink)  
 
Join Date: Aug 2009
Location: Denmark
Age: 65
Posts: 345
Gliders do it too:
sablatnic is offline  
Old 22nd Mar 2019, 22:25
  #7 (permalink)  
 
Join Date: Dec 2002
Location: Dorset,UK
Posts: 399
Smile

sablatnic
looks like an overdose of dihedral :-)
Compass Call is offline  
Old 22nd Mar 2019, 22:40
  #8 (permalink)  
 
Join Date: Feb 2006
Location: Hanging off the end of a thread
Posts: 17,735
NutLoose is offline  
Old 22nd Mar 2019, 22:46
  #9 (permalink)  
 
Join Date: Feb 2006
Location: Hanging off the end of a thread
Posts: 17,735
NutLoose is offline  
Old 24th Mar 2019, 10:53
  #10 (permalink)  
Thread Starter
 
Join Date: Mar 2019
Location: Zurich
Posts: 3
Originally Posted by ICM View Post
I will happily give way to an aerodynamicist on this but, for what it's worth, and based on my time with the C-141 that also had drooped wings on the ground, they certainly straightened out as lift increased. And the effect of the weight of fuel in the wings should also be considered. I could touch the wingtip on the ramp before departure on a flight of four or more hours whereas, after landing, that wingtip would be way out of reach.
Oh, I forgot about that pair! C-141 and its Soviet counterpart Il-76/78.

Doesn't that affect fatigue? That wing weighs tons, literally, and it moves several meters, it seems, with the changes in its own weight. I remember reading that B-52 (?) or some other long-winged bomber was flapping its wings in flight so much that fatigue cracks formed before it even landed. I may be wrong or exhaggerating... a bit.
ProPax is offline  
Old 24th Mar 2019, 23:20
  #11 (permalink)  
 
Join Date: Feb 2008
Location: Midwest US
Age: 64
Posts: 62
I was a Loadmaster on the C-5A some time ago. I do recall one takeoff when I was seated in an aft-facing seat in the aft flight deck and noticed that the wing was just visible at the bottom of the window at the beginning of the takeoff roll. By the time we were airborne, the entire window was filled with wing as observed from the same eyepoint.

TWB
twb3 is offline  
Old 25th Mar 2019, 12:09
  #12 (permalink)  
Thread Starter
 
Join Date: Mar 2019
Location: Zurich
Posts: 3
Originally Posted by twb3 View Post
I was a Loadmaster on the C-5A some time ago.
A totally unrelated question. (I just never met a loadmaster.) If a loadmaster thinks the load is unsafe but the captain still wants to go, who wins? Is there an official separation of duties and "final word"?

ProPax is offline  
Old 25th Mar 2019, 15:36
  #13 (permalink)  
 
Join Date: Nov 2007
Location: Who knows where this week.......
Posts: 139
Captain always wins, clue is in the title.

But I suspect he will be going without his Loadmaster.

Or his other crew.

In all seriousness, after 30 years, I have never known one captain go against safety-related advice from any crew member. And when the Nav left the aircraft with me, he didn't go flying either.
isaneng is offline  
Old 25th Mar 2019, 15:37
  #14 (permalink)  
 
Join Date: Nov 2007
Location: Who knows where this week.......
Posts: 139
Proof read before hitting 'Post' Isaneng you donkey. Apologies,'I have only ever known............'
isaneng is offline  
Old 26th Mar 2019, 14:51
  #15 (permalink)  
 
Join Date: Apr 2008
Location: uk
Posts: 655
Gliders do it too:
Clearly that glider had used up all it's fuel
oxenos is offline  
Old 26th Mar 2019, 17:35
  #16 (permalink)  
 
Join Date: Aug 2014
Location: New Braunfels, TX
Age: 66
Posts: 1,954
All large aircraft wings bend upward during flight, both those with anhedral (like C-5, C-141, C-17, Il-76, An-124 and other military airlifters.) and those with dihedral (the vast majority of airliners.) And yes, that results in fatigue, but is accounted for in the design. The structural weight added to a wing to prevent fatigue failure is much much much less than the weight that would be need to be added to make the wing rigid in flight. Composite wing aircraft flex even more because composites (almost) don't fatigue. Witness that glider wing.
KenV is offline  
Old 26th Mar 2019, 18:25
  #17 (permalink)  
 
Join Date: Dec 2001
Location: FL, USA
Posts: 2,492
There is a very specific purpose to that design anhedral.
It reduces spiral stability aka enhances maneuverability.
The high wing and low center of gravity combined cause some dihedral effect.
So a beast this big wonít get out of its own way without anhedral. Thatís basically the not so scientific explanation.



B2N2 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.