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

AIRBUS Angle Of Attack question

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

AIRBUS Angle Of Attack question

Old 26th Feb 2007, 15:50
  #1 (permalink)  
Thread Starter
 
Join Date: Feb 2007
Location: southern part of Africa
Posts: 24
AIRBUS Angle Of Attack question

Why does it seem that the Airbus(all models) have much greater AOA on approach than its Boeing counterpart.The flare angle on touchdown also seems to be much greater than its rival. The T(MD) tail brigade seems to be similar "visually" to the Boeing and less that of Airbus.
cammron is offline  
Old 26th Feb 2007, 19:24
  #2 (permalink)  
 
Join Date: Jan 2005
Location: uk
Posts: 1,269
Disagree. B737 (classic) pitch on a 3deg ILS about 2.5 up so AoA 5.5deg. A319 pitch about 2deg so AoA about 5deg.

B737 flare to about 4-5 deg up, airbus to about 3. Can't see a great difference. If anything, airbus A319/320 has a lower pitch. Have flown both in the last 3 months.

Anyway, so what? the two aircraft wing sections aren't the same, flap design is different, etc etc, so why would one expect them to have similar alpha?

Can't see your point, I'm afraid.
Gary Lager is offline  
Old 26th Feb 2007, 21:53
  #3 (permalink)  
 
Join Date: Apr 2004
Location: England
Posts: 66
From memory, does this have anything to do with the Airbus being able to fly at less than 1.3 Vs due its fly by wire technology/protection, and the boeing flying 1.3 or more on the approach to land. Both aircraft similar LND weight so could attribute the higher Airbus pitch. Also the Airbus only has single slotted fowlers, where as the boeing has tripple, this also may be why there is a difference in approach attitude.

Mr L.
Mr Levitator is offline  
Old 26th Feb 2007, 22:40
  #4 (permalink)  
 
Join Date: Jan 2007
Location: in the mist
Posts: 557
Airbus for some reason, due to the wing design are certified to fly approaches down to 1.2Vs. That said with GSmini operating the AoA could be quite low (high HW comp). Actually depends on flap design. A321 has a different flap design to the A320 and as such flies the approach at a lower nose attitude than the A320 and A319. However, the A321 strikes it's tail at a lower att too.

B737 is generally more nose up than A320 and B777. However I think this is non manufacturer specific, more to do with basic handling and required margins.
TheGorrilla is offline  
Old 27th Feb 2007, 17:55
  #5 (permalink)  
 
Join Date: Sep 1998
Location: wherever
Age: 50
Posts: 1,609
Airbus for some reason, due to the wing design are certified to fly approaches down to 1.2Vs.
not true.

1.3VSo = 1.23 Vs1g

the referance stall speed is different but the resultant speed is the same.
FE Hoppy is offline  
Old 28th Feb 2007, 02:45
  #6 (permalink)  
 
Join Date: Sep 2002
Location: La Belle Province
Posts: 2,114
Originally Posted by FE Hoppy
not true.

1.3VSo = 1.23 Vs1g

the referance stall speed is different but the resultant speed is the same.
Well, to be more precise:

the reference stall speed is different but the resultant safety is equivalent ... since I believe at least some Airbus products are using Vsr and reduced reference speeds by means of a finding of equivalent safety, since they predate the actual adoption of Vsr by rule.

It's not necessarily true that 1.23Vsr=1.3Vso for a specific type - it all depends exactly how the cert was done.

(As indeed also applies to our products)
Mad (Flt) Scientist is offline  
Old 29th Jul 2010, 22:08
  #7 (permalink)  
 
Join Date: Sep 2004
Location: France
Age: 42
Posts: 145
Mathematically speaking 1,23 Vs1g is higher than 1.3 Vs .

VSmin = 0.94 Vs1g . So take a calculator and work it out

Vref= 1.3 Vso = 1.3 X0.94 Vs1g =1.222 Vs1g

Airbus took 1,23 Vs1g
Citation2 is offline  
Old 30th Jul 2010, 01:56
  #8 (permalink)  
 
Join Date: Feb 2010
Location: PuB near U
Posts: 46
.........how on earth u guys know so much............
ggofpac is offline  
Old 30th Jul 2010, 03:21
  #9 (permalink)  
 
Join Date: Sep 2002
Location: La Belle Province
Posts: 2,114
Originally Posted by Citation2 View Post
Mathematically speaking 1,23 Vs1g is higher than 1.3 Vs .

VSmin = 0.94 Vs1g . So take a calculator and work it out

Vref= 1.3 Vso = 1.3 X0.94 Vs1g =1.222 Vs1g

Airbus took 1,23 Vs1g
Sorry, that statement is not true for all types. The idea that Vs is about 0.94xVsr is an approximation based on looking at recent aircraft when the rule was being worked. There are aircraft where Vsr and Vs1g are much closer, and some further away.

Since FBW Airbuses in Normal Law are alpha protected, defining what Vsr actually is in terms of a "real aerodynamic stall" is quite an exercise in philosophy. You don't really get a traditional CLmax, you don't really get a Vsmin either. I believe all the FBW Airbuses have various kinds of "Special Conditions" to address the fact that the regs are written for an older techniology than now exists.
Mad (Flt) Scientist is offline  
Old 30th Jul 2010, 04:28
  #10 (permalink)  
 
Join Date: Mar 2005
Location: Down South
Age: 84
Posts: 56
have a look at one of the jungle jets in the flare. It looks way higher than either the 73 or the 320.....
squidward is offline  
Old 30th Jul 2010, 05:16
  #11 (permalink)  
 
Join Date: Feb 1998
Location: Formerly of Nam
Posts: 1,595
Cammron and squidward I think your confuseing body angle
with angle of attack. You cant visualy relate the two. Check
the body angle of a full-flapped 747 start of flare in a 45kt
h/w and the same one in zero wind - in both cases the AoA
will be the same but with difering body angles.

The wing design of the Scarebus 321 is diferent from that of
say the 800srs 737. Body angle by itself only becomes a
factor with ref to tailstrike risk.
Slasher is offline  
Old 30th Jul 2010, 07:10
  #12 (permalink)  
 
Join Date: Feb 2010
Location: PuB near U
Posts: 46
Since so many experts here. I need some help on a320. ( Pls PM me to avoid me hijacking the thread)

1) Why is it on the end of the Fuel Leak Procedure it says " for landing - Do not use reversers " ?

2) Why is it on the Fuel Filter clog Ecam it just say " Crew Awareness"? Is it that NOT important? NO mention of chances of erratic operations or flame out at all.

Pls help. Many thanks. ( PM me plz)
ggofpac is offline  
Old 30th Jul 2010, 07:47
  #13 (permalink)  
 
Join Date: Apr 2003
Location: Europe
Posts: 2,973
By far no expert answers:

1) Because you don't want to suck in/blow around any leaking fuel once you've landed.
2) The filter has a bypass, so a clogg won't flame you out.


As for the angle. There is a marked difference in pitch anyway if you compare a flaps 30 approach with a flaps 40 on a 737. And a 320 landing with flaps 3 instead of flaps full does look rather nose high, but so does any aircraft landing with reduced flaps. My guess: it's a combination of visual illusion due to different fuselage design and flap setting.
PENKO is offline  
Old 30th Jul 2010, 09:23
  #14 (permalink)  
 
Join Date: Oct 2009
Location: UK
Posts: 1,271
The 2nd most beautiful, nose up aircraft on the approach, is the TriStar L1011. She flies with an approach attitude of about 7.5 degs NU and if not correctly handled, she can come close to a tail strike on landing. (A tail "skid" projects out of the fuselage tail when the gear is extended.)

Concorde looked the best - but I have no idea of her approach attitude.
rudderrudderrat is offline  
Old 30th Jul 2010, 10:43
  #15 (permalink)  
 
Join Date: Jan 2003
Location: New Zealand
Posts: 139
22.5 Geometric AoA I heard for the concorde.
Lindstrim is offline  
Old 30th Jul 2010, 11:39
  #16 (permalink)  
 
Join Date: Jun 2009
Location: Australia
Posts: 49
I think Slasher has a point. The angle the wings are attached to the body (angle of incidence) could be confusing.
The odd time I got in the back of an old jet ie 727 or such, the floor seemed to be at a climb angle while at cruise.
Air Tourer is offline  
Old 30th Jul 2010, 20:34
  #17 (permalink)  
 
Join Date: Jul 2000
Location: My views - Not my employer!
Posts: 980
Disagree with Gary L...

High drag land flap settings...
737Cl Flap 40 deck angle - 0
A319 Flap Full deck angle - 3

Low drag land flap settings
737Cl Flap 30 deck angle - 3
A319 Flap 3 deck angle - 5
Cough 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.