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From Flashcardlet > aerodynamics exam 2 > Flashcards

aerodynamics exam 2 Flashcards

0
Q

Mach crit

A

When the airflow over the wing reaches the speed of sound you have reached Mach crit

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1
Q

List problems encountered in transonic flight

A

1) force divergence
2) wave drag
- boundary layer separation changes aerodynamic force
- drag increases dramatically due to wave drag
- loss of lift
- shock induced stall
- tuck under
- buffet
- control surface buzz
- control effectiveness
Holy crap

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2
Q

Flight Mach #

A

The air in front of the wing

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3
Q

When MUST you determine runway lengths?

A

When the aircraft is certified under part 25 CFR FAR

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4
Q

Speeds that must be computed

A

V1-decision speed (above this speed continue takeoff)
V2-best rate of climb
VR-rotation speed

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5
Q

What part are our school aircraft certified under?

A

Part 23

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6
Q

Factors effecting takeoff performance

A 
Weight 
       - increased mass
       - rolling friction
Density altitude
       - as Density altitude increases, the density or mass of air decreases which in turn causes less power produced by the engine. Results are slow acceleration, increased takeoff distance and slower rate of climb
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7
Q

What happens to IAS with higher density altitude?

A

TAS increases but IAS remains the same

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8
Q

What does a high density altitude airport require for takeoff?

A

Higher TAS

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9
Q

Effects of upslope on takeoff performance

A

Increase distance approximately 5% for each 1% upslope

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10
Q

Vx

A

Yields most altitude over a given horizontal distance

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11
Q

Vy

A

Yields most altitude over a given time

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12
Q

What is rate of climb dependent on?

A

Excess power

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13
Q

How much performance does a twin engine aircraft lose if an engine fails

A

80%

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14
Q

What increases proportionally with load factor

A

Stall speed..

-square root of load factor-

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15
Q

How to figure out when the aircraft will hydroplane on wet surface

A

Square root of the tire pressure x 9

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16
Q

Top of descent formula (pressurized)

A

3 times altitude loss (TOD)

6 times ground speed (ROD)

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17
Q

TOD for unpressurized aircraft

A

No more than 500FPM

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18
Q

When does pitch control airspeed?

A

When power is not available

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19
Q

Where does best glide occur?

A

L/D max

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20
Q

Forces acting on an aircraft during landing

A

Thrust, weight, drag, lift, braking action

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21
Q

What causes an airplane to return to level flight after lateral upset?

A

Dihedral

22
Q

Dihedral

A

Angle that wings are attached to fuselage

23
Q

T/F - compressibility is not a factor in subsonic flight

A

False

24
Q

If there is a loss of energy, it is a …

A

Shockwave

waves will form in front of the aircraft, just as they do in water

25
Q

What does speed of sound depend on?

A

Temperature

26
Q

Two ways to raise Mach crit

A

1) thinner airfoil

2) swept wing

27
Q

High subsonic designs

A
  • supercritical airfoils are used to make airflow separation harder
  • wing sweep
  • vortex generators (energize airflow and breakup shock waves)
28
Q

What happens when a shockwave forms?

A

You have reached Mach crit

29
Q

Speed regimes and values (4)

A

Subsonic—up to .7 Mach
Transonic—.7 - 1.3 Mach
Supersonic—1.3. - 5 Mach
Hypersonic— > 5 Mach

30
Q

What is TAS

A

Ratio of TAS to temperature

31
Q

Effects of wave drag

A

A loss of energy is known as wave drag

32
Q

What causes wave drag?

A

Airflow

33
Q

Advantages of swept wing in supersonic flight

A

1) raises Mach crit
2) reduces amount of coefficient of drag increase
3) wing is within Mach cone

34
Q

Va

A

Aircraft’s design maneuvering speed

  • not displayed on ASI
  • changes with weight
35
Q

Performance

A

Measure of how well an aircraft flies under the combined effect of thrust and drag

36
Q

Factors affecting aircraft performance

A
  • weight
  • altitude
  • temperature
37
Q

Types of stability

A

STATIC STABILITY (initial response to upset)—
—positive–return to initial position
–neutral–remains displaced
–negative–continues away from initial position
————————————————————————
DYNAMIC STABILITY (effects over time)
–positive–oscillations continue to decrease
–neutral–oscillations remain the same
–negative–oscillations continue to increase

38
Q

Reynolds #

A

Used to measure viscosity of a fluid

39
Q

First study of stability and control

A

Sir George Cailey ( concept of rigid wing )

40
Q

What do symmetrical airfoils not have?

A

Pitching moments

41
Q

Purpose of slots/slats

A

To energize airflow

42
Q

What defines acceleration best

A

Rate of change of velocity

43
Q

Compressibility is not restricted to supersonic flight T/F

A

True

44
Q

Shaft horse power

A

Horsepower that has been run through a gear reduction box

45
Q

Stability in flight refers to…

A

An aircrafts tendency to return to previous flight attitude after an upset

46
Q

What is Mach number based on

A

Ratio of TAS to speed of sound

Mach = TAS/speed of sound

47
Q

What is the most efficient thrust producer?

A

Propellor

48
Q

What is required by a turbofan engine?

A

Bypass ratio

49
Q

How do you measure an aircraft’s efficiency?

A

L/D ratio

50
Q

When is an aircraft fully supersonic?

A

When the bow wave is attached to the leading edges

51
Q

What determines if a “wave” is a shock wave?

A

There is a loss of energy as the air passes through it

52
Q

Effects of reaching force divergence Mach number

A

(A) increase in coefficient of drag
(B) decrease in coefficient of lift
(C) change in pitching moment as center of pressure changes

53
Q

Is an expansion wave a shockwave?

A

No

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