Re: Fuel flow test
Posted: Wed Dec 04, 2019 11:56 am
SonexFactoryTech wrote:We are not sure the intent of Wes' comment.
Hi Kerry,
I was in the middle of responding to Mike. I opened another instance of the SonexBuilders to check on a previous post and saw you response.
This is as far as I got :-)
Like I said, I just finished the FF test and so had/have many of the same questions you have.
Here is my take on it:
1) I'm sure Kerry is right.
2) My tests results were just OK, not stellar. The miniature fuel valve used on my Onex has a smaller orifice than the valve typically used on the Sonex/Waiex. You may be using a similar fuel valve.
3) There are simply too many variables for Sonex LLC to be able to quote a a deck angle for the test.
Examples:
What engine are you using? What is the compression ratio of the engine? How heavy did you build your aircraft? What Prop are you using? The list is endless.
Notice I used the word couldn't, not wouldn't. I was going to point out many of the things you pointed out, but you are so much better at it :-) Anyway, my only intent is to keep the discussion going because Mike has a test he has to perform and needs a number for deck angle. I'm trying to help.
Here's how I came up with a deck angle. I simply estimated a rate of climb and a speed at which that climb would be achieved. If you divide the rate of climb by the speed at which you expect to achieve that ROC, you have the sine of the angle of climb. If you take the arcsin of that number you have the angle of climb.
I used the estimated angle of climb for the deck angle number. This is only an estimate and ignores the angle of incidence and angle of attack of the wing but ..., that is exactly why the test has built in fudge factors of 1.5 x FF and 5 Deg. deck angle.
For my estimate I used an optimistic ROC and a slow climb speed so I would remain on the conservative side.
Example:
Estimated ROC: 1000 Ft. Per Min
Estimated speed for 1000 Ft. Per Min. ROC: 60 MPH (5280 Ft. Per. Min)
Sine ROC = 1000/5280 = 0.1893939
Arcsin 0.1893939 = 10.91 Deg. climb angle.
I rounded that up to 11 deg, added 5 deg and that's how I ended up with 16 deg.
Anyway, that's how I came up with my number for deck angle.
YMMV,
Wes