92.131—Smoke, data analysis.
The following procedure shall be used to analyze the smoke test data:
(a)
Locate each throttle notch test mode, or percent rated power setting test mode. Each test mode starts when the throttle is placed in the mode and ends when the throttle is moved to the succeeding mode. The start of the first idle mode corresponds to the start of the test sequence.
(i)
The highest reading occurring more than two minutes after the notch change (excluding peaks lasting less than 5 seconds, caused by such random events as the cycling of an air compressor) if opacity measurements are recorded graphically; or
(ii)
The average of the second by second values between 120 and 180 seconds after the notch change if opacity measurements are recorded digitally.
(c)
(1)
The values determined in paragraph (b) of this section shall be normalized by the following equation:
Code of Federal Regulations
Where:
Nn is the normalized percent opacity, Nm is the average measured percent opacity (peak or steady-state), and L is actual distance in meters from the point at which the light beam enters the exhaust plume to the point at which the light beam leaves the exhaust plume.
(2)
The normalized opacity values determined in paragraph (c)(1) of this section are the values that are compared to the standards of subpart A of this part for determination of compliance.
(d)
This smoke trace analysis may be performed by direct analysis of the recorder traces, or by computer analysis of data collected by automatic data collection equipment.