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  #121  
Old 07-29-2012, 10:40 AM
fmiddleton fmiddleton is offline
 
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Quote:
Originally Posted by Mel View Post
So, the stall speed stays the same regardless of weight?

Interesting. At light weight the stall speed of the -14 is 5 mph higher than the -7, but at gross weight it is 2 mph lower.

How they do that?
Yes...remember that a stall occurs when the critical angle of attack is exceeded, not related to weight. My guess is that the wing profile causes your observation, but I'm not an aerodynamicist and I didn't stay at a Holiday Inn Express last night.
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  #122  
Old 07-29-2012, 10:42 AM
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skylor skylor is offline
 
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Quote:
Originally Posted by Mel View Post
So, the stall speed stays the same regardless of weight?

Interesting. At light weight the stall speed of the -14 is 5 mph higher than the -7, but at gross weight it is 2 mph lower.

How they do that?
Don't know, but I suspect one of the figures is in error. Nevertheless, these are the numbers that Van's has published in their brochure so they should be included in the comparison.
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  #123  
Old 07-29-2012, 10:47 AM
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skylor skylor is offline
 
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Quote:
Originally Posted by fmiddleton View Post
Yes...remember that a stall occurs when the critical angle of attack is exceeded, not related to weight. My guess is that the wing profile causes your observation, but I'm not an aerodynamicist and I didn't stay at a Holiday Inn Express last night.
Yes but increased weight typically requires more angle of attack at a given airspeed to produce the required lift...hence critical angle of attack should be reached at higher airspeed when at gross vs light loading. Also, this is supposed to be the same wing section as the -10 which has different gross and light load stall speeds. The -14 does have a lower gross weight wing loading than the -10.

Skylor

Last edited by skylor : 07-29-2012 at 11:01 AM.
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  #124  
Old 07-29-2012, 11:03 AM
fmiddleton fmiddleton is offline
 
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Quote:
Originally Posted by skylor View Post
Yes but increased weight typically requires more angle of attack at a given airspeed to produce the required lift...hence critical angle of attack should be reached at higher airspeed when at gross vs light loading. Also, this is supposed the be the same wing section as the -10 which has different gross and light load stall speeds. The -14 does have a lower gross weight wing loading than the -10.

Skylor
I think that works though...in this case weight is relevant with the same wing profile. Lift = Speed * Angle of Attack. Lift has to counteract the weight of the plane, and they stall at the same AoA, therefore the speed will be different. I guess this also just disproved my original assertion about weight...however, the stall AoA on the -7 and -14 is likely different.
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  #125  
Old 07-29-2012, 12:46 PM
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skylor skylor is offline
 
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Quote:
Originally Posted by fmiddleton View Post
...however, the stall AoA on the -7 and -14 is likely different.
Agreed...different airfoils, different critical AOA...but the stall AOA should be the same for the 10 and 14, at different speeds though.
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  #126  
Old 07-29-2012, 07:07 PM
Dave12 Dave12 is offline
 
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I am pretty sure one of the Van's staff said that a IO360 could be substituted for the IO390.
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  #127  
Old 07-29-2012, 10:19 PM
Sig600 Sig600 is offline
 
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It didn't look like it from the "walk around" video, but does anyone know if the -14 uses a reflexed flap position like the -10 in cruise?
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  #128  
Old 07-30-2012, 05:16 AM
rvnor rvnor is offline
 
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Default VNE ????

Anyone know the VNE???
Would be perfect with the IO408 for mogas, 218 HP
OlaM
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  #129  
Old 07-30-2012, 06:37 AM
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Walt Walt is offline
 
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Quote:
Originally Posted by Sig600 View Post
It didn't look like it from the "walk around" video, but does anyone know if the -14 uses a reflexed flap position like the -10 in cruise?
According to rep, yes.
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  #130  
Old 07-30-2012, 02:24 PM
BHunt BHunt is offline
 
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Quote:
Originally Posted by rvnor View Post
Anyone know the VNE???
Would be perfect with the IO408 for mogas, 218 HP
OlaM
That engine has a 10.5:1 compression ratio and is cleared for 91 UL. How is the 390 not approved for mogas with a 8.7:1?
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