Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Flight Perf. & SS > Test 4 Lecture Notes > Flashcards

Test 4 Lecture Notes Flashcards

1
Q

What variables are needed to normalize a yawing moment?

A

q, S, b

Lect. 33, Slide 7

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

True or False:

(dC_L / d psi)_vt is the slope of the lift curve of the vertical tail.

A

False. It’s not the lift curve slope due to the fact that flow over the wing/fuselage combines to generate a sidewash component (but it is close).

Lect. 33, Slide 19

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Directional control in yaw is principally determined by ______.

A

The ability of the rudder to create yawing moments.

Lect. 34, slide

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

There are seven jobs that the rudder is used for with respect to airplanes. What are they?

A
  1. The airplane path on the ground during TO and LNDG
  2. Spin recovery
  3. Coordinate the turn
  4. Induce a sideslip if needed
  5. Overcome prop effects
  6. Overcome asymmetric power effects
  7. Overcome adverse yawing effects

Lect. 34, slide 2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Directional trim changes with speed in straight flight are due almost entirely to ___________. Jet-powered aircraft should have _______ changes.

A

Singe rotation props.
No trim

Lect. 34, slide 4

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Trim changes due to a single-rotation propeller arise from what two effects?

A

Sidewash effects on the vertical tail
Direct propeller yawing moments from the prop normal force

Lect. 34, slide 4

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What are the two effects of the prop sidewash on the vertical tail?

A
  1. Increase in relative speed so qt/q is increased
  2. Increase of the sidewash angle (sigma)

Lect. 34, slide 4

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Why is the vertical tail and rudder often offset from the aircraft’s longitudinal centerline?

A

So that at cruise, no rudder deflection is required. This is especially true when no independent rudder trim is available.

Lect. 34, slide 5

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

True or False

Having an offset rudder/vertical tail helps to reduce pilot workload.

A

True.

Lect. 34, slide 5

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

The greatest cause of directional trim change (for a single prop airplane) with speed is due to _________.

A

The direct yawing moment created by the propeller.

Lect. 34, slide 6

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

As the axis of rotation of the prop is included upward wrt the relative wind, the downward moving blade has a ___________ than the upward moving blade.

A

Higher effective angle of attack.

Lect. 34, slide 6

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

True or False
Since the prop axis is inclined wrt the horizon, the blades will experience a change in angle of attack throughout their cycle of rotation.

A

True

Lect. 34, slide 6

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

If the angle of attack of the aircraft is changed, the prop will produce a _______.

A

Yawing moment.

Lect. 34, slide 7

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

If a prop is yawed with respect to the relative wind, a _________.

A

A pitching moment will result.

Lect. 34, slide 7

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

True or False

The effects of the side wash and the propeller moment are in the same direction and are additive.

A

True

Lect. 34, slide 10

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

When are the effects of side wash and propeller moment greatest?

A

At low flight speeds and high power levels.

Lect. 34, slide 10

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

True or False
For a single rotation propeller aircraft, a rudder deflection is required to maintain heading as a change in speed is applied.

A

True

Lect. 34, slide 11

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

For a single rotation propeller aircraft as speed is changed the rudder must be deflected in order to maintain heading. This is accompanied by a change in ________.

A

Sideslip angle.

Lect. 35, slide 11

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

True or False
Adverse yaw moments are critical at low speeds and the rudder must be sized to overcome these moments, especially near stall.

A

True

Lect. 35, slide 14

20
Q

When the rudder is free to float in response to hinge moments, it can have _______________.

A

An adverse effect on the directional stability.

Lect. 35, slide 20

21
Q

With respect to rudder free analysis; if the AC sideslips, the restoring moment of the tail _________ and the rudder _________.

A

decreases
will float with the wind

Lect. 35, slide 20

22
Q

What is the consequence of having a low pedal force gradient?

A

It will be difficult for the pilot to hold zero sideslip maneuvers.

Lect. 35, slide 22

23
Q

What is the consequence of having a high pedal force gradient?

A

The aircraft will feel sluggish and stiff.

Lect. 35, slide 22

24
Q

The rolling moment the aircraft experiences in sideslip is primarily due to __________.

A

The Dihedral Effect.

Lect. 36, slide 2

25
Q

How is the dihedral effect linked to positive or negative lateral stability?

A

If the rolling moment generated from the dihedral effect is away from the sideslip, the dihedral effect is positive and the AC is said to have positive static lateral stability.

Lect. 36, slide 2

26
Q

For a positive dihedral, the wing panel moving into the wind has a _______ delta alpha and thus a ______ incremental lift value, and VV.

A

positive
positive

Lect. 36, slide 6

27
Q

What are the sign values for dCl’/dbeta and dCl’/dpsi when positive dihedral is considered?

A

dCl’/beta is negative
dCl’/dpsi is positive

Lect. 36, slide 9

28
Q

True or False

A sweepback wing has a negative dihedral effect.

A

False. A sweepback wing has a positive dihedral effect.

Lect. 36, slide 11

29
Q

Sweepforward produces a ______ dihedral effect, while sweepback produces a ______ effect.

A

negative
positive

Lect. 36, slide 13

30
Q

With respect to the fuselage, if the side force acts above the c.g., what type of rolling moment is produced?

A

A stable rolling moment.

Lect. 36, slide 14

31
Q

With respect to the fuselage, if the side force acts below the c.g., what type of rolling moment is generated?

A

A de-stabilizing rolling moment.

Lect. 36, slide 14

32
Q

WIth respect to the fuselage, if the sideforce acts above the c.g., what type of dihedral effect is produced by the sideslip?

A

A positive dihedral effect.

Lect. 36, slide 14

33
Q

WIth respect to the fuselage, if the side force acts below the c.g., what type of dihedral effect is produced?

A

A negative dihedral effect.

Lect. 36, slide 14

34
Q

How do high and low wings affect the dihedral effect?

A

High wings provide a slightly positive effect
Low wings provide a slight negative effect.

Lect. 36, slide 17

35
Q

How does the addition of flaps affect lateral stability?

A

Partial span flaps reduce the effective moment arm thus decreasing the rolling moment. The decrease in lateral stability can be very large.

Lect. 36, slide 18

36
Q

When combined with sweep, if the wing flap LE is swept aft there is a ___________ dihedral effect that is identical to the general sweep effect.

A

small positive

Lect. 36, slide 18

37
Q

How does the prop influence the dihedral effect?

A

Tractor prop = negative dihedral effect
Pusher prop = positive dihedral effect.

Note: For power on flight, the effect is greatest.

Lect. 36, slide 19

38
Q

The rolling moment due to rolling velocity is called ________.

A

Damping in roll.

Lect. 36, slide 22

39
Q

What are the two reasons why the use of ailerons causes a yawing moment (hint–adverse yaw)?

A
  1. Induced drag on the down aileron is increased.
  2. When the AC starts to roll, the lift vectors on the down-going wing are included backward and those on the up-going wing are inclined forward.

Lect. 36, slide 29

40
Q

To overcome adverse yaw, one can increase _____.

A

dCn/dbeta

Lect. 36, slide 34

41
Q

True or False
At low speeds (or high lift coefficients) a large amount of sideslip will be required with a small angle of bank to achieve a steady sideslip.

A

True

Lect. 36, slide 38

42
Q

True or False
Aircraft with large vertical tails in which the centroid of the aerodynamic surface is above the center of gravity will induce a rolling moment.

A

True

Lect. 36, slide 38

43
Q

What is spiral divergence? What conditions are necessary to cause it?

A

Spiral divergence occurs when the static directional stability is very strong in comparison to the dihedral effect. In spiral divergence, when the aircraft is disturbed, it tends to go into an ever-tightening spiral dive.

Lect. 36, slide 41

44
Q

How is Dutch roll related to spiral divergence?

A

Dutch roll exists in any airplane in which the ratio of the static directional stability and the dihedral effect falls between the limiting conditions for spiral divergence and directional divergence.

Lect. 36, slide 42

45
Q

True or False
When directional stability is relatively strong (tending towards spiral divergence) the Dutch Roll oscillation is heavily damped and is not objectionable.

A

True

Lect. 36, slide 42

46
Q

True or False
When the dihedral effect becomes very strong, the Dutch Roll motion is weakly damped and the motion is troublesome for the pilot. In some cases it can become dynamically unstable.

A

True

Lect. 36, slide 42

Flight Perf. & SS (26 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions