Lookin for a lil help on critical engine factors and descriptions. Im flying a Piper Seminole. This is the list and descriptions off my list. Any critiques of these would help.
Critical Engine Inop and Windmilling
-The critical engine inop and windmilling causes dead weight and parasitic drag which raises Vmc. Because the dead engine is not operating the opposite engine has to work even harder to maintin sufficient lift for flight at a given altitude. The drag is caused not just by the bulk of the engine/cowling but also by the windmilling prop, the prop should be feathered so it can become streamline with the relative wind, thus reducing drag.
Rearward CG
-CG location is plays a major role in the controlability of the aircraft. With a rearward CG the arm to the vertical stabilizer is smaller which means more rudder use is needed to maintain directional control, thus increasing Vmc. With a forward CG the arm to the vertical stabilizer is larger giving more leverage to the rudder to maintain directional control, thus decreasing Vmc. (think of it as prying a door open with a pen vs a crowbar)
Most Unfavorable Take-Off Weight
-Weight is plays a role with manueverability. The most unfavorable take-off weight would be a light setting. The less weight the aircraft has the higher Vmc will be due to the fact that the aircraft will be able to pitch and role the aircraft easier than a heavier setting. The heavier the setting the lower Vmc will be. (Think of what would be easier to move, a smart car or a semi truck)
Landing Gear Retracted
-The landing gear plays a role due to retracted or extended effects. With the gear retracted the aircraft is flush with the relative wind, giving no help with maintaining directional control, thus raising Vmc. With the gear extending, Vmc lowers due to Kheel effect. Kheel effect is the effect of the gear acting as miniature surfaces against the relative wind. The surfaces want to become streamline with the relative wind giving a bit of help along the vertical axis, thus lowering Vmc. (the only problem with the gear extended is that it increases parasitic drag reducing performance. If in flight, the gear should be retracted due to the fact that only a handful help is being given, yet a bucket full of drag is being produced)
Operation Engine
-This pertains to how much power/lift is being produced. The more power the engine is producing the higher Vmc is because of pitch and roll tendencies. The more power and lift you have the stronger these tendencies become, thus raising Vmc. The less power being produced lowers Vmc because the pitch and roll tendencies along with less lift are less. This can be usually be determined by altitude. The lower the altitude gives the engine more usuable air to produce more power. The higher the altitude the less usuable air the the engine can use to produce power.
Flaps in the Take-Off Position
-The Seminole's take-off position is 0 degrees. The more lift that is produced the higher Vmc will be due to the pitch and roll tendcies during takeoff. Flap settings such as 10 and 25 degrees increase lift more than drag, increasing Vmc. At full flaps, 40 degrees, more drag than lift is produced decreasing Vmc. (40 flaps should never be used for take-off....DUH) If engine failure is encountered flaps should be set to 0 degrees.
Trimmed for Take-Off
-Trim for take-off should be neutral. If rudder trim is used for take-off, this will increase Vmc due to the decrease in the camber line of the stabilizer. Trimmed rudder decreases the effective surface area of the airfoil. (these tabs are a good portion of the airfoil, keep them neutral)
Airborne or in Ground Effect
-If the aircraft is airborne Vmc will be higher because of the greater Angle of Attack (increasing P-Factor) need to supply sufficient lift. Wingtip vorticies are also greater airborne because they are not reflecting off the ground. In ground effect a lower AOA is needed to produce sufficient lift, thus lowering Vmc.
Cowl Flaps
-Cowl flaps can be debated but as far as I am concerned the are drag. More drag on the inop engine, raises Vmc.
Eliminate Sideslip
-A while back, pilots used rudder as the only means of maintaining directional control but with only rudder, sideslip would occur. If the aircraft is in a sideslip, the relative wind no longer flowing over the front of the aircraft. Instead the relative wind be pounding against the side of the inop engine reducing airflow over the operating side and reducing rudder effectiveness, thus increasing Vmc. To eliminate the sideslip we bank toward the operating engine no more than 5 degrees causing the relative wind to become more streamline over the aircraft, which will lower Vmc.
I know temperature also plays a role in Vmc but that also pertains to how much power is being produced (which i covered) If anyone has some add ons, please post! Thanks to anyone that reads it all, its alot but its checkride material.
Critical Engine Inop and Windmilling
-The critical engine inop and windmilling causes dead weight and parasitic drag which raises Vmc. Because the dead engine is not operating the opposite engine has to work even harder to maintin sufficient lift for flight at a given altitude. The drag is caused not just by the bulk of the engine/cowling but also by the windmilling prop, the prop should be feathered so it can become streamline with the relative wind, thus reducing drag.
Rearward CG
-CG location is plays a major role in the controlability of the aircraft. With a rearward CG the arm to the vertical stabilizer is smaller which means more rudder use is needed to maintain directional control, thus increasing Vmc. With a forward CG the arm to the vertical stabilizer is larger giving more leverage to the rudder to maintain directional control, thus decreasing Vmc. (think of it as prying a door open with a pen vs a crowbar)
Most Unfavorable Take-Off Weight
-Weight is plays a role with manueverability. The most unfavorable take-off weight would be a light setting. The less weight the aircraft has the higher Vmc will be due to the fact that the aircraft will be able to pitch and role the aircraft easier than a heavier setting. The heavier the setting the lower Vmc will be. (Think of what would be easier to move, a smart car or a semi truck)
Landing Gear Retracted
-The landing gear plays a role due to retracted or extended effects. With the gear retracted the aircraft is flush with the relative wind, giving no help with maintaining directional control, thus raising Vmc. With the gear extending, Vmc lowers due to Kheel effect. Kheel effect is the effect of the gear acting as miniature surfaces against the relative wind. The surfaces want to become streamline with the relative wind giving a bit of help along the vertical axis, thus lowering Vmc. (the only problem with the gear extended is that it increases parasitic drag reducing performance. If in flight, the gear should be retracted due to the fact that only a handful help is being given, yet a bucket full of drag is being produced)
Operation Engine
-This pertains to how much power/lift is being produced. The more power the engine is producing the higher Vmc is because of pitch and roll tendencies. The more power and lift you have the stronger these tendencies become, thus raising Vmc. The less power being produced lowers Vmc because the pitch and roll tendencies along with less lift are less. This can be usually be determined by altitude. The lower the altitude gives the engine more usuable air to produce more power. The higher the altitude the less usuable air the the engine can use to produce power.
Flaps in the Take-Off Position
-The Seminole's take-off position is 0 degrees. The more lift that is produced the higher Vmc will be due to the pitch and roll tendcies during takeoff. Flap settings such as 10 and 25 degrees increase lift more than drag, increasing Vmc. At full flaps, 40 degrees, more drag than lift is produced decreasing Vmc. (40 flaps should never be used for take-off....DUH) If engine failure is encountered flaps should be set to 0 degrees.
Trimmed for Take-Off
-Trim for take-off should be neutral. If rudder trim is used for take-off, this will increase Vmc due to the decrease in the camber line of the stabilizer. Trimmed rudder decreases the effective surface area of the airfoil. (these tabs are a good portion of the airfoil, keep them neutral)
Airborne or in Ground Effect
-If the aircraft is airborne Vmc will be higher because of the greater Angle of Attack (increasing P-Factor) need to supply sufficient lift. Wingtip vorticies are also greater airborne because they are not reflecting off the ground. In ground effect a lower AOA is needed to produce sufficient lift, thus lowering Vmc.
Cowl Flaps
-Cowl flaps can be debated but as far as I am concerned the are drag. More drag on the inop engine, raises Vmc.
Eliminate Sideslip
-A while back, pilots used rudder as the only means of maintaining directional control but with only rudder, sideslip would occur. If the aircraft is in a sideslip, the relative wind no longer flowing over the front of the aircraft. Instead the relative wind be pounding against the side of the inop engine reducing airflow over the operating side and reducing rudder effectiveness, thus increasing Vmc. To eliminate the sideslip we bank toward the operating engine no more than 5 degrees causing the relative wind to become more streamline over the aircraft, which will lower Vmc.
I know temperature also plays a role in Vmc but that also pertains to how much power is being produced (which i covered) If anyone has some add ons, please post! Thanks to anyone that reads it all, its alot but its checkride material.
