Constant Speed Props / Manifold Pressure

ALSO SEE:

• Engines / Powerplants
• Multiengine / High Performance / Complex

In General:

• Constant-speed props, adjustable-pitch, adjustable-speed, variable-speed, etc., are called that because you can adjust the RPM and the governor keeps it at that RPM.
• The blue knob (standard color) adjusts the pitch, which in turn adjusts the RPM.
• The black knob (standard) increases/decreases power but the governor tries to maintain the RPM.
• When full forward, the prop gives the highest RPM, but also acts like a brake.
• When full aft, the prop is taking bigger ‘bites’ out of the relative wind.
• IMPORTANT: if your engine fails and you need to glide, pull the prop aft - it’s less drag.
• How a constant speed propeller works.
• How a Piper Seminole constant speed propeller works.

Emergencies:

• First and foremost - always follow your POH
• Need to glide?  Pull the prop full aft when able.  This creates less drag.
• "The Drill"
• PITCH - for blue line
• Mixture (for altitude - it's not binarily forward)
• Props - forward
• Throttles - forward
• Flaps - set
• Gear - up
• Identify AND SLAP your leg
• Verify and pull the throttle back
• Feather
• Mixture - as appropriate
• Engine failure checklist

Governor check:

• I have never seen this described in any POH, but it's a great idea.  After you cycle the prop, pull the prop back until there's a noticeable change (about 100 RPM).  Then gently push up the throttle.  The RPM will increase, but if the governor is working, it should quickly roll back to the starting RPM.  Courtesy:  Steve Jackson

Manifold Pressure:

• Manifold Pressure Sucks (article by AVweb's John Deakin).
• When we talk about RPM and MP (manifold pressure) we drop the zeros off the RPM.  In other words, if we cruise at “22 squared”, we mean 2200 RPM and 22 inches of MP.  Or “21 over 19” would be 2100 RPM and 19 MP.  It’s ‘over’ because we keep the RPM over (or above) the MP.
  

Propeller check:

• The age-old word of mouth (WOM) is to cycle the prop three times.  No POH prescribes it, but it's not a bad idea.  You can watch the RPM, manifold pressure and oil pressure for each cycle.  Additionally, it warms up the oil that drives the propeller change.

Sayings / Expressions / Memory aids:

• Always keep Prop above Throttle (unless POH allows differently).
• When we talk about RPM and MP (manifold pressure) we drop the zeros off the RPM.  In other words, if we cruise at “22 squared”, we mean 2200 RPM and 22 inches of MP.  Or “21 over 19” would be 2100 RPM and 19 MP.  It’s ‘over’ because we keep the RPM over (or above) the MP.
• Blue Sky / Black Earth
• When you add power (go up), you increase propeller first, throttle next
• When you decrease power (go down), you pull the throttle first
• If configuration is Throttle, Prop, Mixture (left to right)
• Gather power up (mixture, prop, throttle)
• Push Power Away (throttle, prop, mixture)
• Pull Power In (mixture, prop, throttle)
• Throw Power Away (throttle, prop, mixture)
• Throttle Back, Power Up
• Reduce the throttle first, Push the Power (Prop) up first

Takeoff:

• Why do we use high RPM for takeoff with a constant speed propeller? (vid)

More info...

• A graphical approach (youtube)

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