What exactly is the meaning of the bottom of the green arc? People have given different answers. Some say this is the prop governor range. Some say carb heat should be used when operating below the green arc. Some say fuel pump should be turned on. Cowl flaps should be closed etc.. POH is of no help here because it just says green arc is the recommended operating range. What do you guys say?
Meaning of green arc for RPM and MP
- Thread starter apilotb
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It just means "normal operating range." Most of the others, like turn on carb heat on a Cessna when below the green, are mostly non-POH techniques gleaned from experience.
Example The POH says, "Carburetor Heat -- ON (apply full heat before reducing power)" in the 172P checklists. People have learned that "reducing power" enough where it is an issue is not reducing from climb to cruise, but when going below the green arc before descending.
Example The POH says, "Carburetor Heat -- ON (apply full heat before reducing power)" in the 172P checklists. People have learned that "reducing power" enough where it is an issue is not reducing from climb to cruise, but when going below the green arc before descending.
WillFly4Food
Pre-takeoff checklist
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WillFly4Food
In 172s and 182s, I was taught to use carb heat even for some situations where you’re still in the green. For example, if you want 90 kts approach speed in a 172, 2100-2200 rpm will usually deliver, and you’re in the green. But you also want to be using heat. Those aircraft are ice makers.
I’ve understood the MP and RPM green zones to simply represent the range of engine power settings that can be used without any time limits.
I’ve understood the MP and RPM green zones to simply represent the range of engine power settings that can be used without any time limits.
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Bob Gardner
Engine operating time limits are in the front of the POH under Operating limitations, not in the general information section.
John Myers
Pre-takeoff checklist
In our plane the bottom of the green arc is the minimum power at which the turbochargers will supply adequate pressurization air. This is probably a fictitious number because however well it was sealed at the factory, it's not that now. Maybe they built in a buffer.
Clip4
Touchdown! Greaser!
In your 182 RG, once you are below 15” the governor is no longer controlling the RPM. Below this point, throttle will control RPM.
In all aircraft, the green arc on the tach is the normal operating range.