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CL Studying > Aerodynamics of Turns, Loads, and Autos > Flashcards

Aerodynamics of Turns, Loads, and Autos Flashcards

1
Q

What are the two components of the total lift generated by a helicopter’s rotor system during a turn?

A

The vertical component (which holds the helicopter up) and the horizontal component (which pulls the helicopter into the turn).

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2
Q

What role does centrifugal force play in a helicopter turn?

A

Centrifugal force, or inertia, acts outward during a turn, causing any object to continue moving in a straight line unless acted upon by another force.

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3
Q

How does the load change when the bank angle increases?

A

The load becomes greater than the weight of the helicopter; at zero bank angle, load equals weight, but with a bank greater than zero, load increases.

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4
Q

What generates lift in a helicopter’s rotor system?

A

Lift is generated perpendicular to the rotor disc and is divided into a vertical component (maintaining altitude) and a horizontal component (pulling the helicopter into the turn).

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5
Q

What is the vertical component of lift responsible for?

A

It counters gravity to maintain altitude.

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6
Q

What does the horizontal component of lift do during a turn?

A

It creates a centripetal force that pulls the helicopter into the turn.

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7
Q

How does gravity affect a helicopter during a turn?

A

Gravity continues to pull down on the helicopter, requiring more lift to maintain altitude.

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8
Q

Define load in a helicopter turn.

A

Load is the total force supported by the aircraft’s lifting surfaces, which exceeds the helicopter’s weight during a turn.

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9
Q

What is centrifugal force in the context of helicopter turns?

A

It opposes the centripetal force and results from the helicopter’s inertia, which tries to keep it moving in a straight line.

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10
Q

How does bank angle affect load factor?

A

A greater bank angle increases load factor, requiring more lift to counteract gravity and centrifugal force.

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11
Q

What is the load factor at a 0° bank angle?

A

The load factor is 1, which equals the helicopter’s weight.

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12
Q

At what bank angle does the load factor reach 2?

A

At a 60° bank angle.

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13
Q

What happens to load factors at bank angles of 80° or higher?

A

Load factors rise sharply, leading to higher stress on helicopter components.

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14
Q

Why is it important to manage bank angles and loads in helicopter flight?

A

To avoid mechanical failure due to increased strain on rotor blades and other components.

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15
Q

What does a load factor table provide for pilots?

A

Load factor values at various bank angles, helping anticipate stress on the helicopter.

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16
Q

Describe the relationship between turbulence and load factor.

A

Turbulence can temporarily increase the load factor, adding strain on the helicopter, especially at higher gross weights.

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17
Q

How does higher gross weight affect helicopter stress?

A

It increases total load on the structure, leading to more stress on rotor, mast, and transmission components.

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18
Q

What happens to the coning angle with higher loads?

A

The coning angle increases, requiring more lift and resulting in a sharper coning angle.

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19
Q

What is the impact of increased coning angle on rotor RPM?

A

It may lead to higher RPM due to the Cholis effect during auto-rotation.

20
Q

How does density altitude affect lift capability?

A

At high density altitudes, lift capability decreases due to reduced air density.

21
Q

What must pilots do to compensate for reduced lift at high density altitudes?

A

They must raise the collective to increase the angle of attack, bringing rotor blades closer to the critical angle.

22
Q

What hazards can abrupt control movements create?

A

They can lead to accelerated stalls or low-G situations, increasing stress on the helicopter.

23
Q

What is the relationship between bank angle and power requirements?

A

Increasing the bank angle raises the load factor, requiring more collective pitch and power to maintain altitude and speed.

24
Q

Define slips and skids in helicopter flight.

A

A slip occurs when horizontal lift exceeds inertia, causing the helicopter to fall into the turn. A skid occurs when inertia exceeds horizontal lift, causing the helicopter to slide outward.

25
Q

How can a pilot visually identify a slip or skid?

A

If the tail slides outward, it’s a skid; if it falls inward, it’s a slip.

26
Q

How does bank angle influence the rate and radius of turns?

A

More bank angle results in a higher turn rate and smaller radius.

27
Q

What is auto-rotation?

A

A flight condition where the rotor is driven by airflow (relative wind) rather than the engine.

28
Q

What is the windmill brake state?

A

The transition phase from engine-driven to wind-driven rotor movement during auto-rotation.

29
Q

Describe airflow dynamics in powered flight.

A

Air flows downward through the rotor system as the helicopter moves forward.

30
Q

What occurs during auto-rotative flight?

A

The helicopter descends, and air flows upward through the rotor, keeping the rotor blades turning.

31
Q

How does entering auto-rotation from a climb differ from entering from a descent?

A

Entering from a climb takes longer due to upward inertia, while entering from a descent results in minimal RPM loss.

32
Q

What are the three main regions of a rotor blade during auto-rotation?

A

Stall region, driving region, and driven region.

33
Q

What happens in the stall region of a rotor blade?

A

Blades are at a high angle of attack, leading to a stall where they generate more drag than lift.

34
Q

What is the function of the driving region?

A

It generates lift and thrust to maintain rotor RPM during descent.

35
Q

Describe the driven region of a rotor blade.

A

It generates lift but with a drag that slows the blades down, moderating descent speed.

36
Q

What are equilibrium points on the rotor blade?

A

Points where aerodynamic forces are balanced, with no net drag or thrust.

37
Q

How does relative wind affect rotor aerodynamics?

A

It is created by rotor rotation, with profile drag acting opposite to the direction of rotation.

38
Q

What impact does adjusting collective have on rotor regions?

A

It changes the size of the driven and stall/driven regions, affecting rotor performance.

39
Q

How do aerodynamic regions shift during forward flight?

A

They shift towards the retreating side, with lower angles of attack on the advancing side.

40
Q

What are the phases of auto-rotation?

A

Entry phase, glide phase (steady descent), and flare phase (approach to ground).

41
Q

What controls RPM during the entry phase of auto-rotation?

A

Lowering the collective reduces drag and helps prevent RPM decay.

42
Q

How is energy managed during auto-rotation?

A

It relies on a balance of altitude, airspeed, and rotor RPM, using kinetic energy to cushion landing.

43
Q

What does the height-velocity diagram indicate for autorotative landings?

A

It shows unsafe altitude and speed combinations, highlighting risks for landing gear and tail strikes.

44
Q

What does excessive landing gear stress result from?

A

Descending from low altitudes at high forward speeds can severely stress the landing gear.

45
Q

Why is it critical to understand the height-velocity curves?

A

They determine safe altitude and airspeed combinations for autorotation based on conditions.

46
Q

How do weight and density altitude affect shaded regions on the height-velocity diagram?

A

Higher weight and density altitude expand shaded areas, making autorotation recovery more difficult.

47
Q

What is the recommended takeoff profile to avoid shaded areas?

A

Conducting a ground run at low altitude and speed, keeping under 10 feet and increasing speed before climb.

CL Studying (11 decks)

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