Aerodynamics
Thread Starter
Joined: Jun 2010
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From: Belfast
Hi
I've been reading the aerodynamics section on 'the technical pilot interview' book and it came up a few times in the answers, example;
The properties that affect an aircrafts stall speed:
Weight
a.Actual Weight
b.Load factor, g in a turn
c.Effective weight/center of gravity position
How does the stall speed vary with weight:
"The stall speed will increase with an increase in the aircraft's autual or effective weight"
Thanks
I've been reading the aerodynamics section on 'the technical pilot interview' book and it came up a few times in the answers, example;
The properties that affect an aircrafts stall speed:
Weight
a.Actual Weight
b.Load factor, g in a turn
c.Effective weight/center of gravity position
How does the stall speed vary with weight:
"The stall speed will increase with an increase in the aircraft's autual or effective weight"
Thanks
Moderator
Joined: Feb 2000
Aviation Qualifications: CPL
Posts: 14,480
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From: UK
At that level I'd say two factors.
(1) How much g you're pulling. In a 2 g turn, effective weight has doubled, so stall speed goes up with square root of weight.
(2) With CG, further aft CG reduces tail downforce, which reduces lift required from the mainplane, which reduces stall speed.
G
(1) How much g you're pulling. In a 2 g turn, effective weight has doubled, so stall speed goes up with square root of weight.
(2) With CG, further aft CG reduces tail downforce, which reduces lift required from the mainplane, which reduces stall speed.
G
Joined: Jul 2007
Posts: 1,158
Likes: 62
From: 51.50N 1W (ish)
Effective weight =
Mass x g + tail downforce.
Tail downforce, which adds to actual weight to increase lift (and hence lift co-efficient) is affected by c of g (forward c of g requires more tail downforce).
Genghis can give the long complicated answer if required...........
(edit - I see he has, although in the original post load factor was separated out, and I think that book considers effective weight as lift required in straight and level flight).
Tail downforce, which adds to actual weight to increase lift (and hence lift co-efficient) is affected by c of g (forward c of g requires more tail downforce).
Genghis can give the long complicated answer if required...........
(edit - I see he has, although in the original post load factor was separated out, and I think that book considers effective weight as lift required in straight and level flight).
Last edited by Fitter2; 17th May 2012 at 10:58.
Joined: Jul 2007
Posts: 812
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From: uk
akafrank07: Just a thought. Try reading your theory textbooks thoroughly rather than trying to bone up on typical questions. That way you will be equipped to answer ANY question! Perhaps this is too "old school" for the internet generation?!
Moderator
Joined: Feb 2000
Aviation Qualifications: CPL
Posts: 14,480
Likes: 178
From: UK
Well if you want me to get picky, stall speed goes up with (weight x load factor / MTOW)^aeroelastic coefficient.
For a rigid wing, aeroelastic coefficient is 0.5. For a non-rigid wing, the coefficient varies according to deformation with loading - a hang-glider can well be in the range 0.6-0.8.
That form of the equation is the Venton-Walters equation.
And you're unlikely to find that in many groundschool notes.
G
For a rigid wing, aeroelastic coefficient is 0.5. For a non-rigid wing, the coefficient varies according to deformation with loading - a hang-glider can well be in the range 0.6-0.8.
That form of the equation is the Venton-Walters equation.
And you're unlikely to find that in many groundschool notes.
G
Moderator
Joined: Feb 2000
Aviation Qualifications: CPL
Posts: 14,480
Likes: 178
From: UK
akafrank07: Just a thought. Try reading your theory textbooks thoroughly rather than trying to bone up on typical questions. That way you will be equipped to answer ANY question! Perhaps this is too "old school" for the internet generation?!
G
Moderator
Joined: Feb 2000
Aviation Qualifications: CPL
Posts: 14,480
Likes: 178
From: UK
