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As350 Nr Calculation With Frequency Meter

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Hello supermechanics, does anyone have the info off hand for the AS350 NR and NG calculations using a frequency meter? Thanks for your help.

 

Cheers,

 

I

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Hello supermechanics, does anyone have the info off hand for the AS350 NR and NG calculations using a frequency meter? Thanks for your help.

 

Cheers,

 

I

 

From AEC Tech Club: (See para. 7)

 

350 B2

NR- NG -NP ACCURACY CHECK

FUEL CONTROL STATIC DROOP CHECK

 

A- PURPOSE: TO PROVIDE TWO METHODS OF CHECKING THE

ACCURACY OF THE NR-NG-NP INDICATION USING A 80 SERIES

FLUKE METER.(recall an accutach can also be used to read NR)

(B2 N.G. indicator can be used for the static droop check if you do not

want to splice into the N.G. system.)(the splice would be for checking the

accuracy of the N.G.tach generator only.)

 

METHOD 1

 

1- PERMENANTLY SPLICE INTO THE INDICATOR WIRES BEHIND THE

DASH AS SHOWN ON THE ATTACHED DRAWING.

2- MOUNT TEST LEAD BRACKETS USING AMP TEST JACKS

AMP P/N 164-401R & 164-401B (red and black test jacks )

 

OR METHOD 2

 

3- DISCONNECT THE INDICATOR PLUG AND CONNECT THE FLUKE

METER INTO THE APPROPRIATE PINS. (NATURALLY THE INDICATOR

WILL NOT WORK WITH THE PLUG DISCONNECTED)

 

4- RUN FLAT PITCH ON THE GROUND, PLUG IN THE FLUKE METER AND

READ THE FREQUENCY OF THE NR AND NG

 

5-USING THE ATTACHED FORMULA, DETERMINE THE NR AND NG SPEEDS

SEE ARRIEL 1D1 SERVICE LETTER (1840 / 98 / ARID / 43 )

 

6- TO CHECK THE FUEL CONTROL STATIC DROOP ON THE GROUND

PLOT THE NR-NG SPEEDS ON THE STATIC DROOP CHART PER THE

ENGINE MM CHAPT.73(along with the gov. scale reading in degrees)

 

7- TO CHECK THE NR AND NG SPEED ACCURACY IN FLIGHT,CRUISE

AT APPROX. 97% NG (B.V.CLOSED) AND TAKE THE HERTZ READINGS

AND USE THE ATTACHED FORMMULA

NR=FREQ.IN HERTZ X 2.5 = NR SPEED

NG= FREQ. IN HERTZ DIVIDED BY 140.017 X 100 = % NG

NP = FREQ. IN HERTZ DIVIDED BY 70.267 X 100 = % NP

( NP is only used to check indicator accuracy other wise it is not a requirement )

 

 

 

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NR=FREQ.IN HERTZ X 2.5 = NR SPEED

 

For the Nr, multiply by 60 to go from seconds to minutes. (Hz to RPM)

 

Divide by the 24 teeth in the phonic wheel.

 

60 divided by 24 equals 2.5

 

That's how you get to that number.

 

If you have a 350B2, you can read the Ng off the digital readout on the Ng gage.

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