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Factors affecting Vmc
Hey I'm just looking for some information regarding the factors that affect Vmc from all the wisdom of this forum.
Thanks. |
Let's see if I can remember from my ME training days...
Worst case is heavy, critical engine failed(usually the left), gear up, aft CG, good engine operating at high power...may be forgetting a thing or two. |
Increases your VMC speed...........Landing gear up, unfavorable c.g., flaps up, takeoff power set, windmilling prop, banking more than 5 degrees into the operative engine, hitting VMC out of ground effect.
Decreases your VMC speed..........Gear down, forward stable c.g., flaps down, banking equal or less than 5 degrees into the operative engine, low power, feathered prop, hitting VMC in ground effect. Simple way to remember, if its more stable, VMC will be lower, less stable, VMC is higher......................... |
I would like to mention something about the flaps. I have NO authoritive basis for this, so take it as is (I'm sure someone will be along to correct me anyways :D). I think those depend on the plane whether they help or hurt Vmc. I have heard that on the Seminole, they help by making it more stable. On the Baron, they hurt Vmc because they blanket the airflow to the rudder. Again, I have no real evidence of that, so if someone could give a bit more insight, I will have learned something new today.
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The memory aid I used was 4 engine, 4 congifuration, 2 weight, 2 pilot input...
4 engine: - Critical engine inop - Prop on critical engine windmilling (unless autofeather installed) - Takeoff or max avail. power - Sea Level 4 Configuration - Gear up - Flaps in T/O position - Cowl flaps in T/O position - Max sea level gross weight 2 Weight - Max sea level gross weight - Most unfavorable CG (usually aft) 2 Pilot Input - Airplane airborne and ground effect negligible - Up to 5 degrees of bank towards operative engine Other members explain how these change Vcm, but this memory aid helped me. Good luck. |
Those are the 10 items that are used to determine VMC under Part 23.
Good memory aid!!! |
Originally Posted by etflies
(Post 212663)
The memory aid I used was 4 engine, 4 congifuration, 2 weight, 2 pilot input...
4 engine: - Critical engine inop - Prop on critical engine windmilling (unless autofeather installed) - Takeoff or max avail. power - Seal Level 4 Configuration - Gear up - Flaps in T/O position - Cowl flaps in T/O position - Max seal level gross weight 2 Weight - Max sea level gross weight - Most unfavorable CG (usually aft) 2 Pilot Input - Airplane airborn and ground effect negligible - Up to 5 degrees of bank towards operative engine Other members explain how these change Vcm, but this memory aid helped me. Good luck. |
Originally Posted by etflies
(Post 212663)
The memory aid I used was 4 engine, 4 congifuration, 2 weight, 2 pilot input...
4 engine: - Critical engine inop - Prop on critical engine windmilling (unless autofeather installed) - Takeoff or max avail. power - Seal Level 4 Configuration - Gear up - Flaps in T/O position - Cowl flaps in T/O position - Max seal level gross weight 2 Weight - Max sea level gross weight - Most unfavorable CG (usually aft) 2 Pilot Input - Airplane airborn and ground effect negligible - Up to 5 degrees of bank towards operative engine Other members explain how these change Vcm, but this memory aid helped me. Good luck. Also Vmc decreases as weight increases. Single Engine performance decreases with an increase of weight, but Vmc actually decreases. |
Originally Posted by XcalibeR
(Post 212624)
I would like to mention something about the flaps. I have NO authoritive basis for this, so take it as is (I'm sure someone will be along to correct me anyways :D). I think those depend on the plane whether they help or hurt Vmc. I have heard that on the Seminole, they help by making it more stable. On the Baron, they hurt Vmc because they blanket the airflow to the rudder. Again, I have no real evidence of that, so if someone could give a bit more insight, I will have learned something new today.
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Vmc
Since I'm currently stuck in Las Vegas at ATP's CFI’s school and I’ve been over this more times than I can count. All I can add is this,
SMACFUM- The conditions that affect VMC, Sea level pressure-increases VMC Max power on the operating engine-Increases VMC Aft legal C.G-Increases VMC Critical engine Wind milling-Increases VMC Flaps/gear down-decreases VMC Up to 5 degrees of bank into operating engine-Decreases VMC Most unfavorable weight-A lighter airplane has a higher VMC than heavier airplane YUM-YUM |
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