Refer to figure.
1. Find the Outside Air Temperature (OAT)
Since the OAT is given as an ISA deviation, we first need to calculate the OAT by applying the deviation to the ISA temperature at the given altitude (8500 ft in this case).

• The lapse rate at which temperature decreases is approximately 2ºC/1000 ft up to 36 080 ft (tropopause).
• ISA temperature at 8500 ft: +15ºC – (2ºC x 8.5) = -2ºC
• Hence, OAT at 8500 ft: ISA temp + ISA dev = -2ºC + 2ºC = 0ºC

2. Find the RPM from the graph
Follow these steps to determine the engine speed (RPM):

1. Enter the graph from the bottom left at an “OUTSIDE AIR TEMPERATURE” of 0°C.
2. Move vertically upward to the “PRESSURE ALTITUDE” of 8500 ft. Since 8500 ft is not directly shown, estimate it midway between 8000 ft and 9000 ft.
3. Move horizontally to the right until you reach a “PERCENT POWER” of 65%.
4. From there, come down and read an “ENGINE SPEED” of approx. 2490 RPM.