Multi-Engine Airplanes

Definitions

Absolute Ceiling:

• The density altitude beyond which no further climb is possible with both engines operating at maximum power.
• The single-engine absolute ceiling is the density altitude the airplane can reach and maintain with the critical engine feathered and the other engine at maximum power.

Asymmetric Thrust: Uneven thrust created by the ascending and descending propeller blades. This condition also occurs when the thrust produced by the engines of a multi-engine airplane is uneven.

Critical Engine: The engine with the most adverse effect on controllability and climb performance of a multi-engine airplane if it fails.

Drift Down: The unavoidable descent due to the loss of an engine when above the single-engine absolute ceiling of an airplane.

Propeller Synchronization: Adjusting the propeller controls to operate the propellers in unison, eliminating the uncomfortable noise of two propellers operating at slightly different rates.

Service Ceiling:

• The maximum density altitude at which the airplane can produce a 100 FPM rate of climb with both engines operating. This ceiling assumes the aircraft is at the maximum gross weight and in the clean configuration.

• The single-engine service ceiling is reached when the single-engine best rate of climb airspeed produces a 50 FPM rate of climb. This ceiling also assumes the critical engine is inoperative with its propeller feathered.

Windmilling: The rotation of an aircraft propeller created by air flowing around it when the engine is not operating.

Zero-Sideslip: A control technique used in following an engine failure in a multi-engine aircraft where the pilot maintains an attitude that minimizes drag, alleviating the sideslip of the airplane.

V-Speeds Unique to Multi-Engine Airplanes

V_MC:

• The minimum control speed with the critical engine inoperative (Ref: 14 CFR 1.2).
• The calibrated airspeed at which, following the sudden critical loss of thrust, it is possible to maintain control of the airplane (Ref: 14 CFR 23.2135).

V_MC is marked on the airspeed indicator with a red line, as determined under specific circumstances.

V_YSE: The best rate-of-climb (or minimum rate-of-sink) speed with OEI. V_YSE is marked on the airspeed indicator with a blue line, as determined at maximum weight and sea-level altitude.

VYSE is a performance speed. VMC addresses directional control.

V_XSE: The best angle-of-climb speed with OEI.

V_SSE: The intentional one-engine inoperative (OEI) airspeed. It is considered the minimum airspeed for intentionally rendering an engine inoperative in flight for pilot training. No intentional engine failure in flight should be performed below this airspeed.

How Aircraft Manufacturers Determine V_MC

14 CFR Part 23 requires airplane manufacturers to determine V_MC, if applicable, for the most critical configurations used in takeoff and landing operations. The following configurations are generally the most critical.

Standard Day Conditions at Sea Level

Baseline Measurement: An airplane must meet performance requirements for certification in still air and standard atmospheric conditions at sea level. This is necessary to establish a standard of measurement.

Density Altitude: Increasing density altitude reduces engine performance and propeller efficiency. Therefore, V_MC decreases as altitude or temperature increases with normally aspirated engines. For turbocharged engines, V_MC remains constant up to the critical altitude.

Most Unfavorable Weight (Light)

Bank Angle: Increased weight increases the horizontal component of lift in a given bank angle, helping to offset the yawing moment caused by asymmetric thrust. As a result, less rudder pressure is needed to maintain control, and V_MC decreases.

Inertia: A heavily loaded airplane has more inertia than a lightly loaded one, giving it greater resistance to yawing, which also reduces V_MC.

Most Unfavorable CG Location (Aft)

Rudder Authority: As the CG moves aft, the moment arm of the rudder is shortened. This reduces the rudder’s leverage, giving it less authority to counteract yawing forces. Therefore, V_MC increases as the CG is moved aft.

Critical Engine Windmilling (Propeller Controls in the Takeoff Position)

V_MC increases as drag on the inoperative engine increases.

Windmilling: A windmilling propeller (low pitch–high RPM) creates more drag than a stationary or feathered propeller, resulting in the highest V_MC.

Unfeathered: When the propeller is stationary, an unfeathered position creates more drag than a feathered propeller.

Feathered: When the propeller is feathered, the blades align with the relative wind, minimizing drag. This reduction in drag lowers V_MC compared to an unfeathered or windmilling propeller.

Flaps, Gear, and Trim in the Takeoff Position

Wing Flaps: For most light twins, the takeoff flap setting is 0° of flaps. Extending the flaps increases drag behind the operative engine. This can have a stabilizing effect that may reduce V_MC.

Landing Gear: Extending the landing gear can create a keel effect that aids directional stability and decreases V_MC. V_MC increases when the landing gear is retracted.

Trim: Since the airplane is usually trimmed to a neutral position on takeoff, having the aircraft pre-trimmed as an aid to an engine failure would be “cheating.”

Up to 5° of Bank Toward the Operating Engine

Banking Toward the Operative Engine: In a bank, the horizontal component of lift helps the rudder counteract the operative engine’s thrust. When banking toward the operating engine, V_MC decreases by approximately 3 knots for every degree of bank less than 5°.

Banking Away from the Operative Engine: Banking away from the operating engine increases V_MC.

Maximum Available Takeoff Power on Each Engine

Power Imbalance: A higher power imbalance between the operating and inoperative engines results in more asymmetrical thrust, increasing V_MC.

Power Effects: Any condition that increases power on the operating engine raises V_MC, while factors like power reduction, higher altitude, increased temperature, or lower air density decrease V_MC.

Static Versus Dynamic V_MC Certification

Dynamic: In dynamic V_MC certification, test pilots cut the critical engine at gradually reduced speeds to find the minimum speed where directional control can be maintained within 20° of the original heading. This involves high power settings and quick pitch adjustments, making it too risky for typical flight training.

Static: Static V_MC certification involves maintaining straight flight with up to 5° of bank toward the operating engine. This method is safer and more closely reflects V_MC demonstrations in flight training.

Control and Performance After an Engine Failure

Directional Control

When a multi-engine aircraft experiences an engine failure and the engines are not mounted on the longitudinal axis, there are unbalanced forces and turning moments about the CG.

Pitch Down: The loss of induced airflow over the horizontal stabilizer results in less negative lift produced by the tail. Additional back pressure is required to maintain level flight.

Roll Toward the Inoperative Engine: The loss of the accelerated slipstream air over the wing of the inoperative engine results in a reduction of lift on that wing. Therefore, due to asymmetrical lift, the aircraft tends to roll toward the inoperative engine. This requires additional aileron pressure into the operative engine.

Yaw: Asymmetrical thrust requires rudder pressure toward the operating engine.

Climb Performance

The loss of one engine results in a 50% loss of power but an approximate 80% loss of climb performance. This can be verified by comparing the climb performance charts for one and two engines operating under the same atmospheric conditions.

Zero-Sideslip

Following an engine failure in flight, the airplane yaws toward the inoperative engine due to asymmetrical thrust. The rudder must be used to maintain directional control. With the rudder deflected, the airplane’s nose is misaligned with the relative wind, resulting in a sideslip. The sideslip increases drag and reduces performance.

Optimal performance is achieved in a zero-sideslip condition, which results in the fuselage being aligned with the relative wind.

How to Establish a Zero-Sideslip Condition

• Bank toward the operative engine by 2° to 3° (“raise the dead”). Less rudder force will be needed because the horizontal lift helps maintain the heading.
• “Split” the ball/brick (slip-skid indicator) toward the operative engine by half a ball width.

Yaw String Demonstration

The use of a yaw string can demonstrate zero-sideslip. A yaw string is a piece of string or yarn approximately 18″–36″ long, taped to the windshield or the nose near the windshield. In a zero-sideslip condition, the relative wind will cause the string to align with the airplane’s longitudinal axis. The string will position itself straight up the center of the windshield.

Four Factors that Make the Left Engine Critical

Asymmetrical Thrust (Yaw)

Each engine’s descending propeller blade will produce greater thrust than the ascending blade when the airplane is operated under power and at positive angles of attack.

Even though both propellers produce the same thrust, the descending blade on the right engine has a longer moment arm (greater leverage) than the left engine’s descending blade. As a result, the left engine’s failure will result in the most asymmetrical thrust.

Accelerated Slipstream (Roll and Pitch)

Asymmetrical thrust (P-Factor) results in a longer moment arm to the center of thrust of the right engine than the left engine. Therefore, the center of lift is farther out on the right wing, resulting in a greater rolling tendency with a loss of the left engine. The left engine’s failure also results in a more significant downward pitching moment due to the greater loss of negative lift produced by the tail.

Spiraling Slipstream (Yaw)

A spinning propeller produces a spiraling wind pattern that rotates in the same direction as the propeller’s rotation. The spiraling slipstream of air from the left engine strikes the vertical stabilizer from the left. This helps counteract the yaw caused by a failure of the right engine.

The right engine’s slipstream does not reach the vertical stabilizer. If the left engine fails, the right engine’s slipstream will not counteract the yaw toward the inoperative engine.

Torque (Roll)

For every action, there is an equal and opposite reaction. A propeller that rotates clockwise (right) will tend to roll the aircraft counter-clockwise (left). The airplane will tend to roll toward the inoperative engine regardless of which engine has failed.

On a multi-engine airplane with clockwise rotating propellers, the effect of torque during OEI flight will:

• Increase the tendency of the airplane to roll toward the inoperative engine (left engine failed); or
• Counteract the tendency of the airplane to roll toward the inoperative engine (right engine failed).

Factors Affecting Control and Performance

Approximate Drag Factors for Light-Twins

• Full Flaps: -275 FPM
• Windmilling Propeller: -200 FPM
• Gear Extended: -250 FPM

Critical Density Altitude

With normally aspirated engines, an increase in altitude or temperature results in reduced engine performance and propeller efficiency. This results in a lower minimum control speed (V_MC) as altitude is increased. However, the calibrated stall speed (V_S) does not decrease with altitude.

There exists an altitude where each of the following exists:

• V_MC is less than V_S (stall occurs first)
• V_MC is the same as V_S (stall and yaw coincide)
• V_MC is greater than V_S (yaw occurs first)

The density altitude where V_MC and V_S are equal is called the critical density altitude. Here, the airplane will “stall and yaw” simultaneously under a condition of asymmetrical thrust. The airplane could experience an abrupt change in attitude or enter into a spin.

Climb Requirements for Certification

The manufacturer must determine climb performance at various weights and altitudes for most multi-engine training airplanes. The airplane does not need to demonstrate climb performance. The published single-engine rate-of-climb may be a negative number.

Current Certification Rules

After a critical loss of thrust, low-speed, multi-engine airplanes with less than 6 passenger seats that do not meet single-engine crash-worthiness requirements must demonstrate a climb gradient of 1.5% at a pressure altitude of 5,000′ in the cruise configuration and out of ground effect.

Historical Certification Rules

Multi-engine aircraft weighing less than 6,000 pounds and with a V_S0 airspeed under 61 knots have no minimum performance criteria.

Multi-engine aircraft weighing more than 6,000 pounds or aircraft with a V_S0 above 61 knots must demonstrate a positive engine-out rate of climb at 5,000′ with OEI and feathered and the aircraft in a clean configuration. The single-engine rate of climb must be equal to 0.027 V_S0². For multi-engine airplanes certified after February 1991, the single-engine rate of climb is expressed as a climb gradient, which is 1.5%.

Preflight Performance Planning

In addition to the planning required for a single-engine airplane, the pilot of a multi-engine airplane should become aware of:

• Accelerate-Go Distance: The distance required to accelerate to liftoff speed, experience an engine failure, complete the takeoff, and climb to clear a 50-foot obstacle.
• Accelerate-Stop Distance: The sum of the differences necessary to accelerate from a starting point to liftoff, experience an engine failure, and come to a complete stop.

• The expected climb performance after takeoff with OEI and the landing gear retracted.
• The single-engine service ceiling.

Before taking the runway, the pilot should know if the airplane can climb following an engine failure. A safety margin should be taken into consideration. Turbulence, wind gusts, or poor technique can easily negate even a 200 FPM rate of climb.

Multi-Engine Taxi Procedures

Taxiing a multi-engine airplane generally involves the same procedures as taxiing a single-engine airplane but has some additional considerations:

• Multi-engine airplanes usually are larger and have longer wingspans than single-engine airplanes.
• Differential thrust from the engines can aid in steering.
• Increasing thrust on the upwind engine can help with directional control in crosswinds.
• The additional propeller creates a greater potential for hitting obstacles and picking up loose debris from the ground.

Multi-Engine Takeoff Procedures

Multi-engine takeoff procedures are similar to single-engine airplanes, but pilots should be aware of the following considerations.

Normal Takeoff: The manufacturer’s recommended rotation speed (V_R) or liftoff speed (V_LOF) should be used during normal operations. If the manufacturer did not publish takeoff speeds, pilots should use a minimum of V_MC plus five knots for V_R.

Crosswind Takeoff: With a crosswind, the pilot can prevent side drift by rotating more positively or at a higher speed. However, the pilot should remember that the AFM/POH performance figures were calculated at the recommended V_R or V_LOF.

Short-Field Takeoff: Just after rotation and liftoff, the airplane should be allowed to accelerate to V_X and make the initial climb over obstacles at V_X. The transition to V_Y should be made as obstacles are cleared.

Soft-Field Takeoff: Soft-field procedures would allow the airplane to become airborne before reaching V_MC. These procedures are not tested during pilot certification and should not be practiced.

Multi-Engine Climb Procedures

Climb Attitude: After leaving the ground, altitude gain is more important than achieving an excess of airspeed. Excessive speed cannot be efficiently traded for altitude in the event of an engine failure. However, excessively high climb attitudes can limit forward visibility and reduce climb performance.

Gear Retraction: The gear should be retracted after a positive rate of climb is established. It is prudent to leave the gear down until the airplane is past the point where a safe landing could be made on the remaining runway or overrun. A general recommendation is to raise the landing gear no later than V_YSE, and once the gear is up, consider it a “Go” commitment if climb performance is available.

Flap Retraction: If flaps were extended for takeoff, they should be retracted as recommended in the AFM/POH.

Initial Climb Speed: The airplane should be accelerated to and maintain V_Y until a safe maneuvering altitude, at least 400′ AGL, is obtained. Any speed above or below V_Y reduces the performance of the airplane.

En Route Climb Speed: Once a safe single-engine maneuvering altitude has been reached, the transition to an en route climb speed should be made. This speed is higher than V_Y and is usually maintained to provide better visibility, increased engine cooling, and a higher groundspeed.

Power Reduction: Power can be reduced as the transition to en route climb speed is made or as recommended in the AFM/POH.

Multi-Engine Approach and Landing Procedures

Multi-engine approach and landing procedures are similar to those of single-engine airplanes, but pilots should be aware of the following considerations.

Traffic Pattern and Approach: The traffic pattern and approach are typically flown at higher indicated airspeeds in a multi-engine airplane. The approach should be made with power. A stabilized approach is essential.

Normal Landing: If a recommended approach speed is not furnished, the speed should be no slower than V_YSE until on a short final with the landing assured, but in no case less than V_MC. A small amount of power may be carried through the roundout and touchdown to prevent high sink rates. With the high wing loading and drag from two windmilling propellers, there is minimal float. Full stall landings are generally undesirable in twins.

Crosswind Correction: The crab and sideslip (wing-low) methods are typically used in conjunction. On final, a crab angle is used to track the extended runway centerline. Before touchdown, the pilot transitions to a sideslip.

Short-Field Approach Speed: Some AFM/POHs recommend a slightly slower-than-normal approach airspeed. If no speed is published, pilots should use the normal approach speed.

How to Identify a Failed Engine

Determining which engine has failed should be primarily accomplished by observing the control inputs required to maintain straight flight. Outside visual references or the inclinometer (ball) should be used to maintain directional control.

"Dead foot, dead engine."

If the airplane is equipped with an exhaust gas temperature (EGT) gauge, it can be used to confirm an engine failure.

Gauges that should not be used to confirm an engine failure include:

• Fuel Pressure: If a fuel pump is on, fuel pressure may indicate normally on the failed engine.
• Manifold Pressure: When the throttle is moved, manifold pressure changes could be mistakenly interpreted as the engine operating normally.
• Tachometer: Before the propeller is feathered, the tachometer will indicate the RPM at which the propeller is windmilling.

• Cylinder Head Temperature (CHT): The CHT does not instantaneously change following an engine failure.

Engine Failure Before Liftoff

The pilot should reject the takeoff if an engine fails before reaching V_R or V_LOF in a small GA airplane. The abort procedure is generally the same as in a single-engine airplane but with an additional need for maintaining directional control due to asymmetrical thrust.

Common Errors for an Engine Failure Before Liftoff

• Attempting to control the aircraft with the rudder instead of aborting the takeoff
• Reducing only one throttle to idle
• Not recognizing the problem resulting in a loss of control

Engine Failure After Liftoff

The Go/No-Go Decision

In the event of an engine failure shortly after takeoff, a decision must be made to continue flight or land, even off-airport. This is called the area of decision. The position of the landing gear is a critical factor in making the decision.

If single-engine climb performance is adequate and the airplane is configured correctly, the climb may be continued. If a climb is impossible, a landing must be made in the most suitable area. Attempting to climb must be discontinued when it is not within the airplane’s capability.

Landing Gear Not Selected Up

The landing gear position is critical in deciding whether to abort or continue the takeoff. As a general rule, if the landing gear lever has not been moved into the up position, the pilot should abort the takeoff roll and use the remaining runway and overrun area to slow the airplane in the event of an engine failure.

Landing Gear Selected Up, Single-Engine Climb Performance Inadequate

If the airplane experiences an engine failure after liftoff and single-engine climb performance has been determined to be inadequate, a landing must be accomplished on whatever lies ahead. The greatest risk would be to attempt to force the airplane to climb when it is not within its performance capability. Higher engine-out landing success rates have been encountered when the airplane is landed under positive control.

Landing Gear Selected Up, Single-Engine Climb Performance Adequate

A pilot attempting a climb with OEI will experience a high workload while addressing the critical factors of directional control, climb, and configuration that determine the successful outcome of the maneuver.

Directional Control

The rudder and aileron should be used, aggressively if necessary, to counteract the yaw and rolling tendencies. At least a 5° of bank should initially be established into the operating engine to help maintain directional control. The amount of lift lost by banking up to 5° is negligible, but exceeding 5° of bank rapidly decreases climb performance. Reducing thrust on the operative engine is necessary if the yaw cannot be controlled.

Airspeed

• The airspeed must stay above V_MC at all times with OEI.
• V_YSE should be maintained for best climb performance.
• V_XSE can be maintained during the initial climb out to clear an obstacle. However, V_XSE is often close to V_MC, leaving little margin or error.

Climb

Once directional control is established and the airplane configured for climb, the bank angle should be reduced to obtain the best climb performance (zero-sideslip condition).

Configuration/Checklists

Memory items from the AFM/POH should be accomplished to establish the airplane in the optimum climb configuration. The printed copy should be reviewed as time permits.

Most procedures direct the pilot to assume V_YSE, set takeoff power, retract the flaps and landing gear, and identify, verify, and feather the failed engine.

Communicate

An emergency should be declared with ATC once workload permits. The pilot should make ATC aware of the severity of the problem and his or her intentions.

Common Errors for an Engine Failure After Liftoff

• Rushing through the checklist
• Misidentifying the failed engine
• A loss of control of the aircraft
• Failing to pitch for and maintain V_YSE
• Failing to feather the propeller on the inoperative engine

Engine Failure During Cruise Flight

An engine failure during cruise flight generally offers more time to diagnose and resolve engine problems. Generally, the initial procedures for an engine failure after takeoff can also be used for an engine failure in flight. However, the engine securing procedure, including propeller feathering, may be delayed until it is apparent that the engine will not restart.

In general, a restart attempt can be made if:

• No heavy vibration was felt before shutdown.
• No fire, smoke, or leaking fluids are visible.
• Rotation of the propeller is possible (no signs of visible damage).
• Time and altitude permit.

Drift-Down Procedure

If the airplane is above its single-engine absolute ceiling during an engine failure, it will slowly lose altitude. The descent rate is greatest immediately following the failure and decreases as the single-engine ceiling is approached.

To minimize the rate of altitude loss, the pilot should:

• Maintain V_YSE.
• Set the maximum allowable power on the operative engine.
• If a restart is impossible, secure the inoperative engine and feather the propeller.

Precautionary Shutdown

A precautionary shutdown is an engine failure with a twist. The engine is failing but not failed.

In this scenario, the PIC must determine the best course of action. To make the determination, the pilot should check the engine gauges and visually inspect the engine, if possible, for signs of fire or damage.

Considerations:

• The engine should be left running if there is any doubt as to whether it is required for further safe flight.
• Vibration, smoke, blistering paint, and large trails of oil indicate a critical situation. The affected engine should be shut down and secured.

The pilot should divert to the nearest suitable airport and declare an emergency with ATC for priority handling.

Common Errors for an Engine Failure During Cruise Flight

• Failure to follow the emergency checklist
• Failure to recognize an inoperative engine
• Hazards of improperly identifying and verifying the inoperative engine
• Failure to properly adjust engine controls and reduce drag
• Failure to establish and maintain the best engine inoperative airspeed
• Improper trim procedure

• Failure to establish and maintain proper bank for best performance
• Failure to maintain positive control while maneuvering

Single-Engine Approach and Landing

An approach and landing with OEI are essentially the same as a two-engine approach and landing. Flight in the traffic pattern with OEI should be similar to a normal traffic pattern but with the following recommendations incorporated.

• The airspeed should be held above V_YSE until a safe landing is assured.
• On the base leg, if performance is adequate, the flaps may be extended to an intermediate setting.
• The final flap setting may be delayed until the landing is assured, or the airplane may be landed with partial flaps.
• A normal, 3° glidepath to a landing is desirable on the final approach.

• VASI or other vertical path lighting aids should be utilized if available.
• Slightly steeper approaches may be acceptable, but a long, flat, low approach should be avoided.
• A single-engine go-around may not always be possible to perform due to the airplane’s weight and the density altitude.
• Anticipate the need for changes in rudder pressure during the roundout and flare.

• Rudder pressure toward the failed engine is required to counteract the drag created by the windmilling propeller.
• Yaw forces are intensified if rudder trim is used to compensate for yaw.
• It is then acceptable to turn toward the failed engine if the airspeed is adequately controlled.

Single-Engine Go-Around

For most light twins, a single-engine go-around must be avoided because:

• The risk of losing direction control is high.
• Climb performance is inadequate, especially with the landing gear or flaps extended.

As a practical rule for single-engine approaches, once the airplane is on final approach with landing gear and flaps extended, it is committed to land.

Common Errors for an Engine Failure During Approach and Landing

• Flying faster than normal because one engine is inoperative
• Not flying a stabilized approach
• Increasing or decreasing throttle without corresponding rudder inputs
• Not completing a checklist from being distracted by the emergency

Conduct of One Engine Inoperative Flight Training

Guarding the Rudder Controls

While simulating engine failures, the instructor’s foot should be positioned to prevent the opposite rudder from moving backward. If the instructor fails the left engine, his or her foot should block the right rudder from moving backward. The opposite is true for a simulated failure of the right engines. This prevents the learner from applying rudder pressure toward the inoperative engine but does not hinder the ability to apply pressure in the appropriate direction.

The following is an easy way to remember which rudder (left or right) should be blocked as a power lever is reduced (pulled).

Pull right, block left. Pull left, block right.

Altitude permitting, the instructor should give one verbal warning if the learner inputs the incorrect rudder control. If the learner does not respond to the verbal warning, the instructor should take the flight controls and return to normal operation.

Guarding of the Throttle Quadrant

The instructor must guard the throttle quadrant in critical phases of flight and while conducting OEI training. It is common for a learner to rush through a checklist and attempt to feather the propeller or cut off the wrong mixture.

Simulated Engine Failure Scenarios

Engine failures are evaluated on practical tests in four phases of flight:

• Engine failure on takeoff (simulated below 50% of V_MC)
• Engine failure after liftoff (simulated above 400′ AGL)
• Engine failure in cruise flight (above 3,000′ AGL unless otherwise specified by the aircraft manufacturer)
• Single-engine approach and landing (simulated)

Engine Failure During Takeoff (Simulated)

Instructors simulating an engine failure on takeoff must do so before the airplane obtains 50% of the V_MC airspeed. Since airspeeds this low are generally not indicated on the airspeed indicator, this failure should be simulated as soon as practicable once the takeoff roll begins.

Applying rudder pressure or dragging a brake are practical ways of simulating an engine failure or partial power loss. The correct action is to abort the takeoff by retarding both throttles to idle, applying the wheel brakes, and maintaining directional control. Any variation from these actions could result in a rapid departure from the runway. The instructor should recover immediately.

Another method of simulating an engine failure is to pull a mixture lever to CUTOFF. The instructor should increase the mixture to restore power as the learner responds correctly by moving the throttles to idle. If the learner does not respond promptly and correctly, the instructor should also cutoff the other mixture. It is better to be on the runway with two inoperative engines than in the grass.

Engine Failure After Liftoff (Simulated)

The minimum altitude for simulating an engine failure after liftoff is 400′ AGL. The failure should be simulated by reducing power with the throttle. Extreme caution must be exercised to prevent the learner from applying pressure to the wrong rudder pedal or reducing power on the operating engine.

The learner should immediately perform the proper checklist from memory while controlling the aircraft. The instructor can establish a zero-thrust setting after the failed engine has been identified, verified, and feathered (simulated).

Feathering can be simulated by moving the propeller lever slightly toward the feather position (or as appropriate if equipped with an auto-feather feature). The instructor’s hand should guard the throttle quadrant to prevent a full feather or an inadvertent mixture cutoff.

Deviations from the proper engine failure procedure must be quickly corrected to avoid a loss of control. If safety is ever in doubt, the instructor should take the flight controls and recover to a safe altitude. Later, any deficiencies in the learner’s performance can be corrected.

Engine Failure During Cruise Flight (Simulated)

Above 3,000′ AGL (or higher altitude if specified by the aircraft manufacturer), engines can be failed by either the mixture or the throttle, though the mixture is preferred. The instructor should use caution when failing engines to avoid rapid throttle movements.

Feathering for pilot flight training and testing purposes should be performed only at a safe altitude and when the aircraft is in a position where a safe landing at an established airport can be readily accomplished in the event difficulty is encountered during the engine restart process. The instructor should locate the nearest suitable airport before simulating an engine failure.

At a safe altitude, the engine with the simulated failure can be secured, which means stopping the propeller’s rotation through feathering. Securing begins when the propeller lever is moved to idle. If the aircraft drifts down to an unsafe altitude, the instructor should take over the controls to restore power.

After securing the engine, the learner should be taught to reduce power on the operating engine (if conditions permit), declare an emergency, and find a suitable place to land. This trains the learner to think through the emergency scenario and separates the engine securing from the engine restart checklist.

If the engine does not restart, the instructor must evaluate when to discontinue the restart attempt, feather the inoperative engine’s propeller, and land. This should be considered an emergency.

Engine Failure During Approach and Landing (Simulated)

An approach and landing with OEI is essentially the same as a two-engine approach and landing, but a higher-than-normal power setting is necessary on the operative engine.

To maintain stability and control, the rudder should be increased/decreased with the corresponding increase/decrease of the throttle. A rapid power increase at low airspeeds and in proximity to the ground can be very hazardous if not accompanied by a corresponding rudder input.

Single-engine go-arounds should not be practiced. During training, the instructor should brief that below 400′ AGL, the learner has both throttles available for a go-around. Both throttles should be increased together to eliminate and avoid asymmetrical thrust situations.

Conduct of Stall Training in Multi-Engine Airplanes

Full stalls in a multi-engine airplane should only be practiced with a qualified flight instructor present. Clear learning objectives and precautions should be discussed.

Asymmetrical Thrust During Stall Training

Single-engine stalls, or stalls with significantly more power on one engine than the other, should not be attempted due to the likelihood of a departure from controlled flight and possible spin entry. Similarly, simulated engine failures should not be performed during stall entry and recovery.

Precautions for Stall Recoveries

Immediate application of full power in a stalled condition has an associated risk due to the possibility of asymmetric thrust. Maximum power should be delayed until reaching a speed above V_MC.