AS-350 B2 Power Assurance Check

[JimEli]

Does the AS-350 B2 power assurance chart give you fits? I’m just back from the Eurocopter factory and while sneaking a glance over the shoulder of an engineer I jotted down the equations for the B2 power assurance check. Here they are, very simple and tidy and suitable for insertion into a spreadsheet. It's also far easier than attempting to weave a pencil through those confusing charts. Use at your own risk.

'inputs
fat -30 to +50 [outside air temperature]
pa 0 to 12000 [pressure altitude]
Q 50% to 94% [observed torque]
Nr 380 to 400 [observed rotor rpm]
Ng 91% to 98% [observed Ng]

theta = (fat + 273.16)/288.16
delta = (1.0 - (pa*0.001981/288.16))^5.256

Ng = Ng/(theta^0.475)

if SAND_FILTER_INSTALLED
kW1 = -0.4916*Ng^2 + 118.90*Ng - 6504.6
else
kW1 = -0.5240*Ng^2 + 126.83*Ng - 6939.0

kW1 = kW1*SQRT(theta)
kW1 = kW1*delta^.9733
kW2 = 0.12376*Q*Nr

if (kW1 < kW2) then
PASS
else
FAIL

[sox6]

'Jotted'? Sure you don't have one of these?
http://www.minox.org/img/minox_tlx.jpg

[maxtork]

Thats good stuff Jim! I've been asking for that formula for years but the powers that be treat it like the secret of life or something. Any chance you could get the formulas for the other aircraft as well? AS350BA? EC120?
EC145?

I already made a excel sheet with it and it seems to work well. I have to double check it's accuracy but it looks to be spot on. If anyone would like it just send me a PM with your email and I'll send it to you but bear in mind it is "for reference ONLY!!" at this point as it has not been approved by the manufacturer.

Happy New Year!

Max

[JimEli]

Actually I didn’t sneak it out of the factory, I simply reverse-engineered the chart. That thing had been giving me fits for years, so I finally tackled it. The others could be worked up in a few hours, but why would you need the 120 (145?), it’s in the VEMD?

[maxtork]

Actually the EC145 is not in the VEMD as it is in others. It is alwasy good for troubleshooting to see if the VEMD is making accurate calculations. Also it helps when you have an FDC filter where you can't use the VEMD power check.

Just curious, how did you reverse engineer the chart? If it was all linear equations I could see it but with some of it being curves is it an estimated formula? or were you able to accurately get the formula for the curves on the chart? Sorry I'm just interested as I wanted to do the same thing myself but wasn't sure how to.

Max

[JimEli]

I fed the chart data into the standard performance equations. It all fits really well. Try getting your hands on a rotorcraft flight test manual (for example, the USNavy’s FTM 106, Rotary Wing Performance). If you study my equations closely, a few things should become apparent.

[maxtork]

I'll see if I can get one thanks. I might have to get my wife and kids to take their shoes off too so I have enough fingers and toes to count though!!

Happy New Year!

Max

[bogey@6]

JimEli-- you are cool!:ok:

Your name rings a bell.. you wrote the B2 Performance application for Palm Devices. Do you have a PocketPc version available now?

bogey@6

[rotorrookie]

Has anyone made exel sheet based on these figures that Jim posted years ago?