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

Total drag questions

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

Total drag questions

Old 27th Oct 2008, 12:50
  #81 (permalink)  
Warning Toxic!
Disgusted of Tunbridge
 
Join Date: Jan 2005
Location: Hampshire, UK
Posts: 4,011
ft, did you not replicate with
Rainboe,
todays nitpicker comment: In a vertical climb most aircraft (which have cambered wings) will in fact have a zero-lift AoA which is negative rather than zero, giving you a few additional degrees nose down relative to vertical to add to those caused by the angle of incidence.
with what I wrote in the previous post:
Originally Posted by Rainboe
In a vertical climb, AoA for all intents and purposes would be zero,meaning the fuselage would have negative pitch (ie be pointing at about 86 degrees pitch whilst plane is climbing vertically)
?

We can produce all sorts of fancy formulae (which really won't mean anything to anybody without a diagram!), but the answer will be- AoA will be in proportion to Cos climb angle. A 15 degree climb will have .97 of level flight lift- you know it, I know it- I feel it in me bones!
Rainboe is offline  
Old 27th Oct 2008, 21:02
  #82 (permalink)  
ft
 
Join Date: Oct 2000
Location: N. Europe
Posts: 436
Rainboe, yes, I was replying to you. AoA will typically be a few degrees negative in a vertical climb rather than zero, due to camber. Fuselage pitch relative to the airflow will be another few degrees more negative due to angle of incidence.

Of course this means I goofed earlier. AoA in a climb won't be given by

AoA_climb = AoA_level*L_climb/L_level

at all, even though the relationship is essentially linear.

(AoA_climb-AoA_zero_lift) = (AoA_level - AoA_zero_lift)*L_climb/L_level

should hold more or less true though!

As for diagrams, you have them earlier in this thread. In addition, this is rather obvious to a lot of people without diagrams so you're making a rather broad statement there. After all, this is only the basic T/W/D/L diagram.
ft is offline  
Old 27th Oct 2008, 23:24
  #83 (permalink)  
 
Join Date: Jan 2005
Location: France
Posts: 2,319
It seems we've now dealt with the original question, and we've all agreed lift and AoA decrease in a steady climb, even if only very little for small climb angles in a 'conventional' aircraft.

So we're now dealing with Rainboe's pet situation, a steady vertical climb.
Admittedly, at first sight we are just talking T=W+D+L, but since none of those vectors point in exactly the right direction, another diagram may be called for?

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