Multiengine Aerodynamics

Question 1

What is the power-to-weight characteristic of the DA42 compared to many single-engine aircraft?

Answer 1

The DA42 uses proportionately more power to carry more weight

This is a key design feature that allows the DA42 to operate effectively at higher weights.

Question 2

How does the accelerated slipstream from the DA42’s engines affect lift?

Answer 2

It enhances lift, allowing the DA42 to carry more weight without a significant increase in wing surface area

This design feature is crucial for optimizing performance.

Question 3

What is the result of higher wing loading in aircraft?

Answer 3

Higher stall speeds and faster approach speeds

This makes handling characteristics different than those of lighter aircraft.

Question 4

What prior experience can aid a pilot’s transition to a multiengine aircraft?

Answer 4

Prior experience with complex, single-engine aircraft

Familiarity with complex systems can ease the transition.

Question 5

What advantages do multiengine aircraft have compared to single-engine aircraft?

Answer 5

Greater rate of climb, higher cruise, descent, and approach speeds

These advantages contribute to enhanced performance in various flight phases.

Question 6

Why is it important for pilots to anticipate aircraft behavior?

Answer 6

To stay ahead of the aircraft and manage the workload

Anticipation is crucial for effective flight management.

Question 7

What is a common misconception about the safety of multiengine aircraft?

Answer 7

They have a perceived safety advantage due to having two engines

This perception can be misleading as performance can diminish with engine failure.

Question 8

Can a multiengine aircraft climb or maintain altitude with one engine inoperative?

Answer 8

It may not be able to depending on aircraft weight and density altitude

Understanding this limitation is critical for safety.

Question 9

What adverse effects can result from engine failure in a multiengine aircraft?

Answer 9

Creates adverse aerodynamic effects, requiring prompt action from the pilot

Recognizing these effects is essential for effective recovery.

Question 10

What does much of the initial and recurrent multiengine training emphasize?

Answer 10

Proficiency in recognizing and managing engine failures in various phases of flight

This training is vital for ensuring pilot competence.

Question 12

What happens to the aircraft’s lateral axis during an engine failure?

Answer 12

Aircraft pitches down due to loss of accelerated slipstream over the tailplane. T-tail aircraft are less affected.

The T-tail design minimizes the impact of the loss of slipstream on the tailplane.

Question 13

What is the effect on the longitudinal axis of an aircraft during an engine failure?

Answer 13

Aircraft rolls toward the dead engine due to loss of accelerated slipstream and loss of lift.

The roll towards the dead engine can create challenges for pilots in maintaining control.

Question 14

How does an engine failure affect the vertical axis of an aircraft?

Answer 14

Aircraft yaws toward the dead engine due to loss of thrust and drag created by the wind milling prop.

The yawing motion can complicate recovery actions and requires prompt pilot response.

Question 15

What is the impact of one engine failure on total available power?

Answer 15

Reduces total available power by 50%

However, overall climb performance is reduced by 80% or more.

Question 16

How does density altitude affect effective engine horsepower?

Answer 16

Effective engine horsepower decreases with density altitude

It may not be possible to maintain altitude when an engine fails at higher altitudes.

Question 17

What may occur if an engine fails after takeoff at high density altitudes?

Answer 17

May result in a negative climb rate

This depends on density altitude and aircraft weight.

Question 18

When should single engine climb performance be calculated?

Answer 18

Before takeoff

Question 19

What does VYSE stand for?

Answer 19

Best single-engine rate of climb. Highest altitude in shortest time with critical engine inoperative

Question 20

What does VXSE stand for?

Answer 20

Best single-engine angle of climb. Highest altitude over the shortest distance across the ground with the critical engine inoperative

Question 21

What is the Single Engine Service Ceiling?

Answer 21

The maximum density altitude at which VYSE produces a 50’/minute climb with the critical engine inoperative.

Question 22

What is the Single Engine Absolute Ceiling?

Answer 22

The maximum density altitude the aircraft can attain or drift down to with the critical engine inoperative.

Question 23

What acronym can help remember the factors affecting climb performance?

Answer 23

ADd PoWer

Question 24

What does ‘A’ in the acronym ADd PoWer represent?

Answer 24

Airspeed - low airspeed reduces performance

Question 25

What does 'D' in the acronym ADd PoWer represent?

Answer 25

Drag - gear, flaps, sideslip reduce performance

Question 26

What does 'P' in the acronym ADd PoWer represent?

Answer 26

Power - low engine power reduces performance

Question 27

What does 'W' in the acronym ADd PoWer represent?

Answer 27

Weight - greater weight reduces climb performance

Question 28

What is the critical engine in multiengine aircraft?

Answer 28

The engine that most adversely affects aircraft performance when it becomes inoperative ## Footnote Critical engines are particularly relevant in aircraft without counter-rotating propellers, such as the diesel-powered DA42.

Question 29

What factors determine the critical engine?

Answer 29

The four factors are: * P-factor * Accelerated slipstream * Spiraling slipstream * Torque ## Footnote Remember the acronym PAST to recall these factors.

Question 30

True or False: The critical engine is the engine that improves aircraft performance when inoperative.

Answer 30

False ## Footnote The critical engine adversely affects performance, making it crucial to identify.

Question 31

Fill in the blank: The critical engine is determined by four factors known as _______.

Answer 31

PAST ## Footnote PAST stands for P-factor, Accelerated slipstream, Spiraling slipstream, and Torque.

Question 32

What type of aircraft commonly has a critical engine?

Answer 32

Multiengine aircraft without counter-rotating propellers ## Footnote An example is the diesel-powered DA42.

Question 33

Critical Engine Acronym

Answer 33

PAST

Question 34

What does PAST stand for

Answer 34

P -Factor, Accelerated slipstream, Spiraling slipstream, Torgue

Question 35

What is P-factor?

Answer 35

P-factor causes the right engine’s center of thrust to be farther from the longitudinal axis, giving it a greater arm ## Footnote P-factor is a phenomenon affecting the thrust produced by propellers, particularly in multi-engine aircraft.

Question 36

What happens when the left engine fails?

Answer 36

Failure of the left engine will result in more yaw ## Footnote This yawing motion is due to the asymmetrical thrust produced by the remaining engine.

Question 37

How does each engine's accelerated slipstream affect the wings?

Answer 37

Each engine’s accelerated slipstream increases lift on each wing ## Footnote The slipstream is the airflow generated by the propeller, which enhances aerodynamic performance.

Question 38

What effect does P-factor have on each wing's center of lift?

Answer 38

P-factor causes greater thrust to be produced on the right side of each propeller, putting each wing’s center of lift to the right of the engine ## Footnote This results in an imbalance in lift distribution between the wings.

Question 39

Which wing's center of lift is further from the longitudinal axis?

Answer 39

The right wing’s center of lift is further from the longitudinal axis than the left wing ## Footnote This difference in distance provides a longer arm for the right wing, increasing its lift advantage.

Question 40

What is the impact of the right engine's slipstream on the tail?

Answer 40

The slipstream from the right engine produces less negative lift on the tail ## Footnote This can affect the stability and control of the aircraft.

Question 41

What is the result of a left engine failure in terms of aircraft movement?

Answer 41

Failure of the left engine results in a greater roll into the dead engine and greater pitch downward ## Footnote This highlights the critical importance of engine performance in maintaining flight control.

Question 42

What is the effect of spiraling slipstream from the left engine?

Answer 42

Moves inward toward the longitudinal axis, enhancing rudder effectiveness ## Footnote This airflow is crucial for maintaining control during flight.

Question 43

What happens to rudder effectiveness when the left engine fails?

Answer 43

More yaw due to decreased rudder effectiveness ## Footnote This can lead to control challenges for the aircraft.

Question 44

What does the slipstream from the right engine do?

Answer 44

Moves away from the longitudinal axis and does little to enhance rudder effectiveness ## Footnote This contributes less to directional stability.

Question 45

What principle describes the relationship between actions and reactions in aviation?

Answer 45

For each action, there is an equal and opposite reaction ## Footnote This principle is essential for understanding aircraft dynamics.

Question 46

What effect does torque from the left engine have when the right engine fails?

Answer 46

Creates a roll toward the operating engine, aiding in raising the dead engine ## Footnote This helps maintain aircraft control during engine failure.

Question 47

What happens when the left engine fails in terms of torque?

Answer 47

Causes a roll toward the dead engine, resulting in decreased performance ## Footnote This can severely affect the handling characteristics of the aircraft.

Question 48

What does VMC stand for?

Answer 48

Minimum Controllable Airspeed

Question 49

What is the minimum airspeed at which directional control can be maintained?

Answer 49

VMC

Question 50

How is VMC determined?

Answer 50

By the manufacturer using IAW 14 CFR 23.2135(c)

Question 51

Does flight at VMC ensure the ability to climb or maintain altitude?

Answer 51

No

Question 52

What may happen if an aircraft operates below VMC?

Answer 52

Loss of rudder effectiveness and potential loss of aircraft control

Question 53

What is a potential consequence of operating below VMC?

Answer 53

VMC roll

Question 54

What happens to stall speed as density altitude increases?

Answer 54

Remains essentially unchanged

Question 55

What happens to VMC as density altitude increases?

Answer 55

Gradually decreases

Question 56

What factors contribute to the decrease in VMC with increasing density altitude?

Answer 56

* Reduced engine performance * Reduced propeller efficiency

Question 57

At what altitude are demonstrations of VMC in the DA42 typically conducted?

Answer 57

At or above 5000 feet MSL

Question 58

What may occur before loss of directional control during VMC demonstrations?

Answer 58

Stall warning or buffeting

Question 59

What effect does high density altitude have on non-turbocharged engine and propeller performance?

Answer 59

Reduces performance ## Footnote High density altitude leads to less engine performance, resulting in less adverse yaw and lower VMC.

Question 60

How does ground effect influence VMC?

Answer 60

Reduces induced drag and lowers VMC ## Footnote At higher altitudes, the wing will stall before VMC is reached.

Question 61

What is the impact of an engine performing below rated power on VMC?

Answer 61

Reduces yaw and lowers VMC ## Footnote Lower engine performance decreases adverse yaw.

Question 62

How does an aft center of gravity affect VMC?

Answer 62

Raises VMC ## Footnote Aft CG creates a shorter rudder arm and decreases rudder effectiveness.

Question 63

What effect does a wind-milling propeller have on VMC?

Answer 63

Raises VMC ## Footnote A wind-milling propeller creates greater drag and more adverse yaw.

Question 64

What is the effect of a feathered propeller on VMC?

Answer 64

Lowers VMC

Question 65

How do flaps in the takeoff position affect VMC?

Answer 65

May lower VMC ## Footnote DA42 aircraft are not equipped with cowl flaps.

Question 66

What is the impact of extending landing gear on VMC?

Answer 66

Lowers VMC ## Footnote It provides stabilizing, keel effect.

Question 67

What happens to VMC when landing gear is retracted?

Answer 67

Increases VMC ## Footnote While it reduces drag and increases climb performance, it also reduces stability.

Question 68

What is the effect of banking up to 5˚ into the operating engine on VMC?

Answer 68

Reduces VMC ## Footnote It uses a horizontal component of lift to decrease the amount of rudder required.

Question 69

How does increased aircraft weight affect VMC?

Answer 69

Lowers VMC ## Footnote Heavier weight increases stability and directional control but reduces climb performance.

Question 70

What is the single-engine climb gradient capability of the DA42 at 5000 foot pressure altitude?

Answer 70

1.5% ## Footnote This is with the critical engine inoperative and the operating engine at maximum power.

Question 71

What conditions must be met for the DA42 to maintain a single-engine climb?

Answer 71

Critical engine inoperative, inoperative engine propeller feathered, landing gear and flaps retracted, climb speed not less than VYSE

Question 72

What can dramatically affect an aircraft's single-engine performance?

Answer 72

Piloting technique ## Footnote Technique in handling the aircraft while operating on a single engine can lead to varying performance outcomes.

Question 73

What is sideslip in aviation?

Answer 73

Using only rudder to offset yaw created by asymmetric thrust while maintaining wings level ## Footnote This technique does not align the fuselage with the relative wind.

Question 74

What is a significant drawback of using the sideslip technique?

Answer 74

Creates a significant drag penalty ## Footnote While it may maintain heading, it reduces available climb performance.

Question 75

What is zero sideslip?

Answer 75

Rudder input to keep slip indicator displaced halfway toward the operating engine, banking up to 5˚ toward operating engine ## Footnote This technique aligns the fuselage with the relative wind.

Question 76

What does zero sideslip create to offset yaw from an inoperative engine?

Answer 76

A horizontal component of lift ## Footnote This helps in maintaining better overall performance.

Question 77

What is the benefit of zero sideslip compared to sideslip?

Answer 77

Minimizes drag and provides the best overall performance ## Footnote This technique enhances climb performance and overall aircraft handling.

Question 78

What is the optimal bank angle toward the operating engine for establishing a zero sideslip configuration in the DA42?

Answer 78

A 2 - 3˚ bank ## Footnote Establishing a zero sideslip configuration is important for effective flight control.

Question 79

What is the loss of climb performance with an engine loss

Answer 79

“Overall climb performance is reduced by 80% or more”