MULT-ENGINE TRAINING & MANEUVERS MANUAL
311 Airport Drive
Smoketown, PA 17576
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This program is designed for a multi-engine add-on rating. Pilots have a choice to receive a multi-engine commercial or private, VFR or IFR rating. Not all the maneuvers in this manual are required for a VFR or private add on rating. Maneuvers that are not required for all ratings will be noted.
SECTION ONE: ENGINE-OUT AERODYNAMICS
THE PROBLEM OF ASYMMETRIC THRUST
When a multi-engine aircraft loses an engine, there will be unbalanced forces and turning moments about the center of gravity. The following directional control performance problems will result.
1) PITCH Down
The loss of induced airflow over the horizontal stabilizer results in less negative lift from
the tail and causes the nose to pitch down. To compensate for this pitch-down, additional
back pressure is required.
2) ROLL Toward The Dead Engine
The loss of airflow created by the propeller (accelerated slipstream) over the dead engine
results in a loss of lift on that wing. This loss of lift causes a roll toward the dead engine
and will require additional aileron deflection into the operating engine.
3) YAW Toward The Dead Engine
The loss of one engine will result in asymmetric thrust being produced. This will cause the
aircraft to yaw toward the dead engine and will require additional rudder pressure on the
side of the operating engine. “Dead Foot, Dead Engine”
ENGINE INOPERATIVE CLIMB PERFORMANCE
Climb performance depends on the excess power needed to overcome drag. When a multi-engine airplane loses an engine, the airplane loses 50% of its available power. This results in a loss of approximately 80% of the aircraft’s excess power and climb performance. Drag is a major factor relative to the amount of excess power available. An increase in drag (such as the loss of one engine) must be offset by additional power. This additional power is now taken from excess power, making it unavailable to aid the aircraft in a climb. When an engine is lost, maximize thrust (full power) and minimize drag (flaps and gear up, prop feathered, etc.) in order to achieve optimum single-engine climb performance. Refer to the GA-7 P.O.H., page 5-15 for the Cougar single-engine climb performance under specific pressure altitude, temperature, and weight conditions.
SINGLE ENGINE SERVICE CEILING
The single engine service ceiling is the maximum density altitude at which the single engine best rate of climb airspeed (Vyse) will produce a 50 FPM rate of climb with the critical engine inoperative.
SINGLE ENGINE ABSOLUTE CEILING
The single engine absolute ceiling is the maximum density altitude that an aircraft can attain or maintain with the critical engine inoperative. Vyse = Vxse at this altitude.
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SIDESLIP VS. ZERO SIDESLIP
During flight with one engine inoperative, pilot technique is important to maximize aircraft performance. An important technique is to establish a Zero Sideslip condition.
; Sideslip Condition
When an engine failure occurs, thrust from the operating engine yaws the aircraft. To
maintain aircraft heading with the wings level, rudder must be applied toward the
operating engine. This rudder force results in the sideslip condition by moving the nose
of the aircraft in a direction resulting in the misalignment of the fuselage and the
relative wind. This condition usually allows the pilot to maintain aircraft heading;
however, it produces a high drag condition, which significantly reduces performance.
; Zero Sideslip Condition
The solution to maintaining aircraft heading and reducing drag to improve performance
is the Zero Sideslip Condition. When the aircraft is banked into the operating engine
(usually 2-5 degrees), the bank angle creates a horizontal component of lift. The
horizontal lift component aides in counteracting the turning moment of the operating
engine, minimizing the rudder deflection required to align the longitudinal axis of the
aircraft with the relative wind. In addition to banking into the operating engine, the
appropriate amount of rudder required is indicated by the inclinometer ball being “split”
towards the operating engine side. The Zero Sideslip Condition must be flown for
optimum aircraft performance.
Vmc is the minimum airspeed at which directional control can be maintained with the critical engine inoperative. Vmc speed is marked on the airspeed indicator by a red radial line. The FAA sets guidelines that aircraft manufacturers must follow in determining Vmc speed. These guidelines are governed under FAR Part 23. They are:
1. Standard day conditions at sea level (Max engine power)
2. Maximum power on the operating engine (Max yaw)
3. Critical engine windmilling (Max drag)
4. Flaps takeoff position, landing gear up (Least stability)
5. Aft legal center of gravity (Least rudder effectiveness)
6. Up to 5 degrees of bank into the operating engine
7. Maximum takeoff weight
Note: Any change to the above criteria could result in a significant change in Vmc, although recovery procedures should be maintained within the guidelines of the P.O.H. and the FAA Flight Training handbook. The following summarizes how Vmc may be affected by the above criteria, although each aircraft is different and may be subject to different handling qualities considering the discussed conditions.
1) Standard Day Sea Level
Standard conditions yield high air density that allows the engine to produce max power. An
increase in altitude or temperature (decrease in air density) will result in reduces engine
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performance and prop efficiency. This decreases adverse yaw effect. Vmc decreases as altitude is increased.
2) Maximum Power On The Operating Engine
When the operating engine develops max power, adverse yaw is increased toward the inoperative engine. The pilot must overcome this yaw to maintain directional control. Any condition that increases power on the operating engine will increase Vmc speed. Any condition that decreases power on the operating engine (such as power reduction by the pilot, an increase in altitude, temperature, low density, or an aging engine) will decrease Vmc speed.
3) Critical Engine Windmilling
When the propeller is in a low pitch (unfeathered), it presents a large area of resistance to the relative wind. This resistance causes the engine to “windmill”. The windmilling creates a large amount of drag and results in a yawing moment into the dead engine. When the propeller is “feathered,” the blades are in a high pitch position, which aligns them with the relative wind, minimizing drag. A feathered prop will decrease drag and lower Vmc.
4) Gear up and Flaps in Takeoff Position
When the gear is extended, the gear and gear doors have a keel effect, reducing the yawing tendency and decreasing the Vmc speed. Extended flaps have a stabilizing effect that may reduce Vmc speed (increase in drag which counteracts the thrust produced by the good engine)
5) Aft Legal Center of Gravity
As the center of gravity moves aft, the moment arm between the rudder and the CG is shortened, reducing the leverage of the rudder. This reduced leverage reduces the rudder’s effectiveness and results in a higher Vmc speed.
6) Up to 5 Degrees Bank Into the Operating Engine
When the wings are level, only the rudder is used to stop the yaw produced by the good engine (sideslip condition). Banking into the operating engine creates a horizontal component of lift. With this horizontal lift component, less rudder deflection is required to overcome yaw. Vmc decreases with bank into the good engine by a factor of approximately 3 knots per degree of bank angle.
7) Maximum Takeoff Weight at Sea Level
During straight & level flight, the aircraft weight will not affect Vmc. However, in a given bank, the heavier the aircraft, the greater the horizontal component of lift and the less rudder is required. As weight increases, Vmc decreases.
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