Weight equation is giving me hard time: Weight = (V / 1,278)2 x A x

[Analucius]

Hi,

Trying to find a min flying weight from this Eq:

Weight = (V / 1,278)2 x A x Cl (where Cl=0.9 , V=6 m/s A=0.72 m^2)

This equation yelds no result in mathcad. What am I doing wrong?

Thanks Morten

 

[GregLocock]

You've missed the exponentiation operator out. It should be v^2

also that 1.278 has units, if you are using those in mathcad.

I imagine the original equation was

1/2*airdensity*v^2*CL*A







Cheers

Greg Locock

 

[Analucius]

Hi Greg,

Thanks for your input. I have now removed all units in the sheet and still no answer. My definitions seems alright - but I get not result when doing the Wmin=

Very odd.

Another thing I need the area in dm^2 not in m^2 How would I go about that?

Any ideas?

morten

 

[IRstuff]

What do you mean by "no result?" Mathcad is unlike Matlab, so you have to specifically ask for an answer, e.g.:

Weight:1/2*airdensity*v^2*CL*A
Weight=

When you hit return on the second equation, Mathcad should display Weight=90000 or whatever.

dm is a non-standard unit in Mathcad, so at the top of the sheet, define dm:0.1m

then you can use dm as any other regular unit. Be careful not to redefine built-in units, as that can have disastrous effects on other dependent units in your calculations.

TTFN