Multiengine Aerodynamics Flashcards
DA42 Concise Book Section 1
What is the power-to-weight characteristic of the DA42 compared to many single-engine aircraft?
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.
How does the accelerated slipstream from the DA42’s engines affect lift?
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.
What is the result of higher wing loading in aircraft?
Higher stall speeds and faster approach speeds
This makes handling characteristics different than those of lighter aircraft.
What prior experience can aid a pilot’s transition to a multiengine aircraft?
Prior experience with complex, single-engine aircraft
Familiarity with complex systems can ease the transition.
What advantages do multiengine aircraft have compared to single-engine aircraft?
Greater rate of climb, higher cruise, descent, and approach speeds
These advantages contribute to enhanced performance in various flight phases.
Why is it important for pilots to anticipate aircraft behavior?
To stay ahead of the aircraft and manage the workload
Anticipation is crucial for effective flight management.
What is a common misconception about the safety of multiengine aircraft?
They have a perceived safety advantage due to having two engines
This perception can be misleading as performance can diminish with engine failure.
Can a multiengine aircraft climb or maintain altitude with one engine inoperative?
It may not be able to depending on aircraft weight and density altitude
Understanding this limitation is critical for safety.
What adverse effects can result from engine failure in a multiengine aircraft?
Creates adverse aerodynamic effects, requiring prompt action from the pilot
Recognizing these effects is essential for effective recovery.
What does much of the initial and recurrent multiengine training emphasize?
Proficiency in recognizing and managing engine failures in various phases of flight
This training is vital for ensuring pilot competence.
What happens to the aircraft’s lateral axis during an engine failure?
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.
What is the effect on the longitudinal axis of an aircraft during an engine failure?
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.
How does an engine failure affect the vertical axis of an aircraft?
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.
What is the impact of one engine failure on total available power?
Reduces total available power by 50%
However, overall climb performance is reduced by 80% or more.
How does density altitude affect effective engine horsepower?
Effective engine horsepower decreases with density altitude
It may not be possible to maintain altitude when an engine fails at higher altitudes.
What may occur if an engine fails after takeoff at high density altitudes?
May result in a negative climb rate
This depends on density altitude and aircraft weight.
When should single engine climb performance be calculated?
Before takeoff
What does VYSE stand for?
Best single-engine rate of climb. Highest altitude in shortest time with critical engine inoperative
What does VXSE stand for?
Best single-engine angel of climbe. Highest altitude over the shortest distance across the ground with the critical engine inoperative
What is the Single Engine Service Ceiling?
The maximum density altitude at which VYSE produces a 50’/minute climb with the critical engine inoperative.
What is the Single Engine Absolute Ceiling?
The maximum density altitude the aircraft can attain or drift down to with the critical engine inoperative.
What acronym can help remember the factors affecting climb performance?
ADd PoWer
What does ‘A’ in the acronym ADd PoWer represent?
Airspeed - low airspeed reduces performance
What does ‘D’ in the acronym ADd PoWer represent?
Drag - gear, flaps, sideslip reduce performance
What does ‘P’ in the acronym ADd PoWer represent?
Power - low engine power reduces performance
What does ‘W’ in the acronym ADd PoWer represent?
Weight - greater weight reduces climb performance
What is the critical engine in multiengine aircraft?
The engine that most adversely affects aircraft performance when it becomes inoperative
Critical engines are particularly relevant in aircraft without counter-rotating propellers, such as the diesel-powered DA42.
What factors determine the critical engine?
The four factors are:
* P-factor
* Accelerated slipstream
* Spiraling slipstream
* Torque
Remember the acronym PAST to recall these factors.
True or False: The critical engine is the engine that improves aircraft performance when inoperative.
False
The critical engine adversely affects performance, making it crucial to identify.
Fill in the blank: The critical engine is determined by four factors known as _______.
PAST
PAST stands for P-factor, Accelerated slipstream, Spiraling slipstream, and Torque.
What type of aircraft commonly has a critical engine?
Multiengine aircraft without counter-rotating propellers
An example is the diesel-powered DA42.
Critical Engine Acronym
PAST
What does PAST stand for
P -Factor, Accelerated slipstream, Spiraling slipstream, Torgue
What is P-factor?
P-factor causes the right engine’s center of thrust to be farther from the longitudinal axis, giving it a greater arm
P-factor is a phenomenon affecting the thrust produced by propellers, particularly in multi-engine aircraft.
What happens when the left engine fails?
Failure of the left engine will result in more yaw
This yawing motion is due to the asymmetrical thrust produced by the remaining engine.
How does each engine’s accelerated slipstream affect the wings?
Each engine’s accelerated slipstream increases lift on each wing
The slipstream is the airflow generated by the propeller, which enhances aerodynamic performance.
What effect does P-factor have on each wing’s center of lift?
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
This results in an imbalance in lift distribution between the wings.
Which wing’s center of lift is further from the longitudinal axis?
The right wing’s center of lift is further from the longitudinal axis than the left wing
This difference in distance provides a longer arm for the right wing, increasing its lift advantage.
What is the impact of the right engine’s slipstream on the tail?
The slipstream from the right engine produces less negative lift on the tail
This can affect the stability and control of the aircraft.
What is the result of a left engine failure in terms of aircraft movement?
Failure of the left engine results in a greater roll into the dead engine and greater pitch downward
This highlights the critical importance of engine performance in maintaining flight control.
What is the effect of spiraling slipstream from the left engine?
Moves inward toward the longitudinal axis, enhancing rudder effectiveness
This airflow is crucial for maintaining control during flight.
What happens to rudder effectiveness when the left engine fails?
More yaw due to decreased rudder effectiveness
This can lead to control challenges for the aircraft.
What does the slipstream from the right engine do?
Moves away from the longitudinal axis and does little to enhance rudder effectiveness
This contributes less to directional stability.
What principle describes the relationship between actions and reactions in aviation?
For each action, there is an equal and opposite reaction
This principle is essential for understanding aircraft dynamics.
What effect does torque from the left engine have when the right engine fails?
Creates a roll toward the operating engine, aiding in raising the dead engine
This helps maintain aircraft control during engine failure.
What happens when the left engine fails in terms of torque?
Causes a roll toward the dead engine, resulting in decreased performance
This can severely affect the handling characteristics of the aircraft.
What does VMC stand for?
Minimum Controllable Airspeed
What is the minimum airspeed at which directional control can be maintained?
VMC
How is VMC determined?
By the manufacturer using IAW 14 CFR 23.2135(c)
Does flight at VMC ensure the ability to climb or maintain altitude?
No
What may happen if an aircraft operates below VMC?
Loss of rudder effectiveness and potential loss of aircraft control
What is a potential consequence of operating below VMC?
VMC roll
What happens to stall speed as density altitude increases?
Remains essentially unchanged
What happens to VMC as density altitude increases?
Gradually decreases
What factors contribute to the decrease in VMC with increasing density altitude?
- Reduced engine performance
- Reduced propeller efficiency
At what altitude are demonstrations of VMC in the DA42 typically conducted?
At or above 5000 feet MSL
What may occur before loss of directional control during VMC demonstrations?
Stall warning or buffeting
What effect does high density altitude have on non-turbocharged engine and propeller performance?
Reduces performance
High density altitude leads to less engine performance, resulting in less adverse yaw and lower VMC.
How does ground effect influence VMC?
Reduces induced drag and lowers VMC
At higher altitudes, the wing will stall before VMC is reached.
What is the impact of an engine performing below rated power on VMC?
Reduces yaw and lowers VMC
Lower engine performance decreases adverse yaw.
How does an aft center of gravity affect VMC?
Raises VMC
Aft CG creates a shorter rudder arm and decreases rudder effectiveness.
What effect does a wind-milling propeller have on VMC?
Raises VMC
A wind-milling propeller creates greater drag and more adverse yaw.
What is the effect of a feathered propeller on VMC?
Lowers VMC
How do flaps in the takeoff position affect VMC?
May lower VMC
DA42 aircraft are not equipped with cowl flaps.
What is the impact of extending landing gear on VMC?
Lowers VMC
It provides stabilizing, keel effect.
What happens to VMC when landing gear is retracted?
Increases VMC
While it reduces drag and increases climb performance, it also reduces stability.
What is the effect of banking up to 5˚ into the operating engine on VMC?
Reduces VMC
It uses a horizontal component of lift to decrease the amount of rudder required.
How does increased aircraft weight affect VMC?
Lowers VMC
Heavier weight increases stability and directional control but reduces climb performance.
What is the single-engine climb gradient capability of the DA42 at 5000 foot pressure altitude?
1.5%
This is with the critical engine inoperative and the operating engine at maximum power.
What conditions must be met for the DA42 to maintain a single-engine climb?
Critical engine inoperative, inoperative engine propeller feathered, landing gear and flaps retracted, climb speed not less than VYSE
What can dramatically affect an aircraft’s single-engine performance?
Piloting technique
Technique in handling the aircraft while operating on a single engine can lead to varying performance outcomes.
What is sideslip in aviation?
Using only rudder to offset yaw created by asymmetric thrust while maintaining wings level
This technique does not align the fuselage with the relative wind.
What is a significant drawback of using the sideslip technique?
Creates a significant drag penalty
While it may maintain heading, it reduces available climb performance.
What is zero sideslip?
Rudder input to keep slip indicator displaced halfway toward the operating engine, banking up to 5˚ toward operating engine
This technique aligns the fuselage with the relative wind.
What does zero sideslip create to offset yaw from an inoperative engine?
A horizontal component of lift
This helps in maintaining better overall performance.
What is the benefit of zero sideslip compared to sideslip?
Minimizes drag and provides the best overall performance
This technique enhances climb performance and overall aircraft handling.
What is the optimal bank angle toward the operating engine for establishing a zero sideslip configuration in the DA42?
A 2 - 3˚ bank
Establishing a zero sideslip configuration is important for effective flight control.
