Performance Flashcards
What is the primary role of horsepower in helicopter performance?
It is the metric used to measure the helicopter’s performance- it’s ability to hover, climb, and maneuver.
How does altitude affect horsepower output?
Higher altitudes reduce air density, causing lower oxygen levels available for combustion and diminished horsepower.
Why does warmer air reduce engine performance?
Warmer air is less dense, lowering the available oxygen per engine stroke and reducing horsepower.
How does humidity impact helicopter performance?
Humid air is less dense, providing less oxygen for combustion and reducing engine power output.
What does ‘hover ceiling’ mean?
The maximum altitude at which a helicopter can maintain a hover. Determined for IGE and OGE.
Define ‘In Ground Effect’ (IGE) hovering.
Hovering within one rotor diameter of the ground, which enhances lift by reducing induced flow and minimizing tip vortices.
Define ‘Out of Ground Effect’ (OGE) hovering.
Hovering more than one rotor diameter from the ground, requiring more power there is more induced flow through the rotor blades and rotor tip vortices are able to grow larger.
How does weight affect hover ceiling?
Heavier loads reduce hover ceiling, requiring more power to hover at a given altitude.
What is the relationship between altitude and hovering?
At higher altitudes, the air is less dense, restricting the aircraft’s ability to hover at a certain point. A pilot must calculate hover ceilings to determine what altitude they can successfully hover at.
What is climb rate in helicopter performance?
The vertical speed at which a helicopter ascends, influenced by engine power, rotor efficiency, and air density.
How does high-density altitude affect climb rate?
It reduces lift efficiency and power output, decreasing climb rate.
How does atmospheric pressure affect performance?
Lower pressure decreases air density, reducing performance, while higher pressure increases it.
How does thermal expansion due to warm temperatures affect performance?
Warm air expands, reducing density and therefore reduces performance; cool air is denser and therefore enhances performance.
Describe the effect of humidity on air density.
When there is high humidity, the water molecules are displacing oxygen molecules and therefore decreasing air density, reducing lift and engine power.
What is density altitude?
Pressure altitude adjusted for non-standard temperature.
The altitude the aircraft “feels” like it’s at during a flight.
How does high density altitude affect takeoff distance?
It increases the required takeoff distance due to reduced air density and performance.
What is the benefit of flying in cooler parts of the day?
Cooler temperatures increase air density, improving lift and optimizing engine output.
How can high altitudes and temperatures impact rotor efficiency?
Lower air density reduces rotor lift, necessitating more power to maintain performance. There are less oxygen molecules being displaced by the airfoil which is directly affecting lift production, via the lift equation.
How can pilots use performance charts for planning?
To estimate hover ceilings, power output, airspeed restrictions under expected conditions.
How does air density influence the engine’s oxygen intake?
Lower density means fewer oxygen molecules per intake, decreasing fuel combustion efficiency.
Define pressure altitude and its purpose.
The true altitude adjusted for nonstandard pressure (29.92). It is used for performance calculations.
-set the altimeter to 29.92 and read the outcome directly
or
-mathematically: 1000 x (29.92 - reported pressure) + field elevation
How does pressure altitude vary with weather changes?
High or low-pressure systems can raise or lower the pressure altitude.
Why is manifold pressure crucial in engine management?
It shows the parameters that will keep the engine power output at 124HP at 2652rpm; exceeding limits can damage the engine.
How is VNE (Never Exceed Speed) determined in helicopters?
Determined based on altitude and temperature to prevent retreating blade stall.
How does carburetor heat affect performance?
It heats up the air before it’s ingested into the engine, reducing air density, potentially decreasing hover ceiling by up to 2,000 feet.
How does a pilot manage low RPM in high-density altitude?
By reducing collective.
Why should pilots avoid abrupt maneuvers at high VNE?
To prevent retreating blade stall and maintain structural integrity.
How can reducing weight improve hover performance?
It lessens the power required to generate lift, aiding operations in high-density conditions.
Why is understanding density altitude important for mountain flying?
Mountain flying involves higher elevations where engine performance is reduced due to low air density. Understanding density altitude allows us to calculate how much power is available to us throughout different flight environments.
Why is knowing the pressure altitude important for confined area landings?
Confined areas require steep approaches to land and therefore knowing how much power is available within a certain flight configuration is critical.
What factors affect air density?
Temperature, humidity, altitude, and air pressure.
What is the horsepower and engine rpm of an R22?
Max continuous is 124HP at 2652rpm.
What are the components of the lift equation?
L = (1/2) d v2 s CL
d=density
v=velocity
s= surface area of airfoil
CL= the airfoil angle of attack
What are the standards by which aircraft performance is evaluated? (temperature, pressure, lapse, and altitude)
15degrees C
29.92
-2degrees C / 1000’ gained
sea level
Why does atmospheric pressure change?
Weather systems like high and low-pressure areas.
When there’s a high-pressure system, the atmospheric pressure is above standard, while a low-pressure system means the atmospheric pressure is below standard.
Better describe the standard reference datum via an example.
Imagine a field at Prescott, AZ, with a known elevation of 5,045 ft. If the atmospheric pressure is low (e.g., 29.80 inHg), we must “sink” below the field level to reach the 29.92 inHg reference level, effectively raising our pressure altitude above the field elevation.
Conversely, if the atmospheric pressure is high (e.g., 30.22 inHg), we would “climb” above the field to reach the 29.92 inHg reference, thus lowering our pressure altitude below the field elevation.
Verbalize a depiction of the standard pressure plane.
Visualize a cross-section of the atmosphere, the 29.92 inHg “plane”C moves up and down based on actual atmospheric pressure. When pressure is lower than standard, the plane sinks closer to the surface, raising pressure altitude. When pressure is higher than standard, it rises, lowering pressure altitude.
Key Insight: Pressure altitude represents the aircraft’s altitude relative to this shifting plane. Pilots need to know whether they’re operating above or below this plane to understand how it will affect their performance.
What happens at full throttle?
The engine butterfly valve is fully open and providing max power output. If you continue to pull collective up at this point, you are introducing more pitch into the blades, thus increasing drag without giving more power which can result in rpm decay, especially in High DA settings.
What are the engine and drivetrain design limits for the Robinson R22, and what happens if these limits are exceeded?
The engine and drivetrain components in the Robinson R22, including the main rotor blades, gearboxes, drive shafts, and engine, are designed to endure 2,200 hours of operation if flown within prescribed limits. Exceeding power limits overstresses these components, leading to increased wear and tear, which can reduce their lifespan and reliability.
What is the Vne speed for the R22 below 3,000’ DA?
102; use the chart in the POH to determine Vne above 3000’ DA
