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Negative side of V-G Diagram?

Bluto

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How does one determine the stall line on the negative (< 0g) side of the V-G diagram? Determining the positive side is easy, since all you have to do is determine the stall speed for a given load factor. However, with a negative load factor my equation doesn't work. The equation I'm referring to is:

Vstall at a given load factor = the square root of the load factor * stall speed at 1 g.

Any theories? Thanks.
 

banned username 2

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Bluto said:
How does one determine the stall line on the negative (< 0g) side of the V-G diagram? Determining the positive side is easy, since all you have to do is determine the stall speed for a given load factor. However, with a negative load factor my equation doesn't work. The equation I'm referring to is:

Vstall at a given load factor = the square root of the load factor * stall speed at 1 g.

Any theories? Thanks.

You can't stall a plane at 0 G's, since 0 G's requires 0 lift...
 

Bluto

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um, ok...

I agree, but you can stall an airplane at < 0 g. Anyone else?
 

alimaui

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Bluto,

I am the farthest thing from a math major, but you can take the square root of a negative number (yes you can stall at negative Gs). However without my aerodynamics book in front of me (on may 5 the brain was turned off :D I would not have the slightest idea of how to explain it coherently.

I know I just posted with absolutely nothing important to say, but everyone else does it, why cant I ;)

Ali
 

DC-3TP

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I think you would need to know or determine the -1G stall speed in inverted flight and use your equation. Unfortunately that is not one of the airspeeds normally published in the POH.

If your aircraft has a VG diagram, It should show an airspeed for a given load factor either negative or positive. I hope I was able to help.
 

banned username 2

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Re: um, ok...

Bluto said:
I agree, but you can stall an airplane at < 0 g. Anyone else?

How can you technically stall an airplane at 0G when there is no lift being created so there is no lift being lost?
 

Bluto

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You can't

I never said you could stall at zero G. I only said you could stall at less than zero G. I maintain that this is true. Look at a V-G diagram. The line that extends from the 0 point downward and to the right is the stall line at negative G. Theoretically, couldn't you pitch forward fast enough that you exceeded the critical angle of attack? Of course it is possible to stall with negative G.
 

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yes you can stall at negative G's, but no Normal, Transport or Utility catagory aircraft is going to have this information in the AFM, since none are approved for flight in the negative G regime. You might find this info in an Aerobatic Catagory AFM, but then again, if you want to get anal about it, most aerobatic airplanes have a symetrical wing, which means they would stall at the same speed at +3 Gs as they would at -3 Gs...

Technically negative Gs are only relative to your relative position with the earth... roll inverted and do a "negative G push-over" and you are pulling positive G's (relative to mother Earth)...

The chart is based on G's, not negative or positive... G's are G's, the only thing that makes them negative or positive are their relation to the top of the aircraft.

You have too much time on your hands, shouldn't you be studying your EMB-145 manual???
 

Bluto

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Too much time on my hands? You got that right! :) Thanks for your input. I just thought I'd see if some of the big-brains on here could help me figure this out. I don't mean to be argumentative.
 
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