Performance I Flashcards

1
Q

What is the key element for determining an aircraft’s performance?

A

The drag polar.

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2
Q

CD stands for (note the capital D)?

A

The drag coefficient for the entire aircraft.

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3
Q

C_D_0 stands for?

A

The parasite drag coefficient for the aircraft.

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4
Q

The Oswald efficiency factor is represented using the symbol ___.

A

e

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5
Q

For basic performance, lift is considered to be _______.

A

Perpendicular to the flight path direction and equal and opposite to the weight.

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6
Q

For basic performance, drag is considered to be _____ to the flight path direction.

A

Parallel

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7
Q

True or False
For an aircraft in flight, the thrust is often inclined with respect to the flight path although the angle is usually small.

A

True

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8
Q

The angle between the horizontal plane and the flight path is given the symbol ____.

A

theta

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9
Q

True or False
The flight path is drawn in a straight line, however, the AC is generally traveling in a curved path (especially when viewed from a distance).

A

True

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10
Q

In the most basic sense, all flight is ______ as opposed to straight.

A

Curvilinear

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11
Q

The case where the acceleration of the aircraft is equal to zero is referred to as _________.

A

Static performance.

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12
Q

For completely level flight, the angle between the horizontal and the flight path is _______.

A

Zero

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13
Q

True or False
In steady level flight with no acceleration or disturbances, T = D and L = W.

A

True

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14
Q

Thrust required varies proportionally with _______ and inversely with ______.

A

The drag coefficient times the weight
The lift coefficient

T = (CD*W)/CL = W/(CL/CD)

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15
Q

Thrust required varies inversely with the _____ ratio.

A

Lift to Drag

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16
Q

The thrust required is directly proportional to the ____ ratio.

A

Drag to lift (D/L)

Note: T = 1/(L/D) = D/L

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17
Q

Since Thrust required varies ____ with the lift to drag ratio, the minimum thrust required will occur when ______.

A

Inversely
The aircraft is flying at a velocity where the L/D ratio is at a maximum

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18
Q

True or False
The L/D ratio is a measure of the structural efficiency of the AC.

A

False, its a measure of the aerodynamic efficiency.

19
Q

On the velocity vs thrust required curve, a low speed corresponds to what five aerodynamic characteristics?

A
  1. High angle of attack
  2. High CL
  3. High CD_i (induced drag)
  4. Low q_infinity
  5. Low CD_0
20
Q

On the velocity vs thrust required curve, a high-speed corresponds to what five general aerodynamic characteristics?

A
  1. Low angle of attack
  2. Low C_L
  3. High q_infinity
  4. High C_D_0
  5. Low C_D_i
21
Q

Induced thrust decreases with ________.

A

Increasing velocity and vice versa.

Note: Induced thrust required is proportional to inverse velocity squared.

22
Q

Parasite thrust increases with ________.

A

Increasing velocity and vice versa.

23
Q

Minimum thrust required occurs where ____.

A

The airspeed at which the lift to drag ratio is at a maximum.

24
Q

At (L/D) max, the airframe’s induced drag is equal to ______.

A

The parasite drag.

CD_0 = CD_i

25
Q

Thrust required is an ______ associated phnomenon.

A

Airframe

26
Q

Thrust available is an ______ associated phenomenon.

A

Engine

27
Q

For a propeller driven aircraft, thrust at a zero velocity is at a ____________.

A

Maximum

28
Q

For a propeller-driven aircraft, thrust varies as forward speed changes in accordance with ______.

A

The efficiency of the propeller (\Nu_prop)

29
Q

For a reaction jet engine, the thrust _____ slightly with forward speed due to _______.

A

Increases
Inlet pressure recovery

30
Q

If the thrust increases to the maximum amount available, the aircraft’s speed is ______.

A

Fixed

31
Q

The intersection of what two curves defines the maximum aircraft speed?

A

The Tr (thrust required) and the Ta (thrust available) curve.

32
Q

For gliding flight, the descent angle is strictly a function of ______.

A

The lift to drag ratio.

33
Q

At low speeds, C_D_0 includes _____ and _____.

A

Skin friction
pressure drag

Pamadi, Pg. 72

34
Q

What is power required?

A

The power required is the power necessary to overcome the aerodynamic drag of the airplane.

Pamadi, Pg. 72

35
Q

What is thrust required?

A

The thrust necessary to balance the aerodynamic drag of the aircraft.

Pamadi, Pg. 72

36
Q

For a given altitude, the power developed by a piston engine is virtually constant with _______.

A

Flight Velocity

Pamadi, Pg. 73

37
Q

Power developed by a piston engine decreases with an increase in altitude because of _______.

A

The decrease in density.

Pamadi, Pg. 73

38
Q

What is required for a piston aircraft’s propulsive efficiency to be assumed constant over the operating range?

A

The aircraft must be equipped with a variable pitch, constant speed prop.

Pamadi, Pg. 73

39
Q

For gliding flight, the flattest glide occurs when ____.

A

The glider flies at (CL/CD) max or the minimum drag per unit weight.

Pamadi, Pg. 80

40
Q

What CL/CD condition is required for max range in a glider.

A

Max CL/CD

Pamadi, Pg. 80

41
Q

For a glider, the rate of sink is at a minimum when _____.

A

CL^(3/2) / CD is maximum.

Pamadi, Pg. 81

42
Q

For a glider, the maximum endurance occurs when ______.

A

CL^(3/2) / CD is maximum.

Pamadi, Pg. 84

43
Q

For a glider, endurance is _______ when sink rate is minimum.

A

Maximum

Pamadi, Pg. 84