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Instrument Oral > Flight Instruments > Flashcards

Flight Instruments Flashcards

1
Q

What instruments operate from the pitot/static system?

A

Altimeter, VSI and airspeed indicator

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2
Q

How does an altimeter work?

A

Aneroid wafers expand and contract with atmospheric pressure changes, and through a shaft and gear linkage rotate pointers on the indicator

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3
Q

What are the limitations that a pressure altimeter is subject to?

A

Nonstandard pressure and temperature

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4
Q

What are the effects of warmer than standard temperature on the altimeter?

A

The pressure level is higher than standard day. Altimeter indicates lower than actual altitude.

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5
Q

What are the effects of colder than standard temperature on the altimeter?

A

The pressure is lower than on a standard day. The altimeter indicates higher than actual altitude.

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6
Q

What is the effect of higher than standard pressure on the altimeter?

A

The pressure level is higher than a standard day. The altimeter indicates lower than actual altitude.

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7
Q

What is the effect of lower than standard pressure on the altimeter

A

Pressure is lower than on standard day. The altimeter indicates higher altitude than actual altitude.

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8
Q

For IFR, what is the max allowable error for an altimeter?

A

75’

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9
Q

Define and how to determine indicated altitude

A

Read off the face of the altimeter

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10
Q

Define and how to determine pressure altitude

A

Indicated altitude with 29.92 in the window

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11
Q

What is the name of the altimeter setting window?

A

The Kollsman window

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12
Q

Define and how to determine true altitude

A

Height above sea level. Use the flight computer.

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13
Q

Define and how to determine density altitude

A

Pressure altitude corrected for non-standard temperature. Use the flight computer

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14
Q

Define and how to determine absolute altitude

A

Height above the ground. Subtract terrain elevation from true altitude

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15
Q

How does the airspeed indicator operate?

A

Measures the difference between ram pressure from the static source

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16
Q

What limitations is the airspeed indicator subject to?

A

Proper flow of air in the pitot/static system

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17
Q

What are the three error the airspeed indicator is subject to?

A

Position error - static ports sensing erroneous static pressure; slipstream flow causes disturbance at the static port.
Density error - changes in altitude an temp are not compensated for by the instrument
Compressibility error - packing air into the pitot tubes, resulting in higher-than-normal indications. Usually occurs above 180KIAS.

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18
Q

What are the four types of airspeeds?

A

Indicated (IAS, KIAS)
Calibrated (CAS)
Equivalent (EAS)
True (TAS)

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19
Q

What airspeeds are indicated by the white arc on the airspeed indicator?

A

Flap operating range
bottom is flaps down stall speed
Top is max airspeed for flaps-down flight

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20
Q

What airspeeds are indicated by the green arc on the airspeed indicator?

A

normal operating range
The bottom is the no-flap stall speed
The top is max airspeed for rough air

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21
Q

What airspeeds are indicated by the yellow arc on the airspeed indicator?

A

structural warning area
bottom is the max a/s for rough air
top is VNE

22
Q

How does the VSI work?

A

Changing pressures expand or contract a diaphragm connected to the needle by gears and levers. The VSI is connected to static pressure line by a calibrated leak. It measures differential pressure

23
Q

What are the limitations of the VSI

A

Not accurate until the acft is stabilized. SUdden or abrupt changes in aircraft attitude causes errors. These changes are not immediately reflected due to calibrated leak.

24
Q

What instruments are affected when the pitot tube ram and drain holes freeze?

A

Only the AS/I is affected. Acts like an altimeter.

25
Q

What instruments are affected when the static port freezes?

A

AS/I - Accurate at the altitude frozen. AS/I reads high in a descent. A/S reads low in an ascent
Altimeter - indicates the altitude at which the system was blocked
VSI - indicates level flight

26
Q

If the temp is 6C at an airport with elev of 1,200ft and standard lapse rate exists, what is the approximate freezing level?

A

4,200MSL

6C sfc temp divided by avg temp lapse rate of 2C results in 3,000ft, then add 1,200ft airport elev.

27
Q

What is corrective action for a frozen pitot tube? For frozen static tube?

A

For pitot tube - turn on pitot heat

For static port - use alt air if available or break the face of a static instrument

28
Q

What indications should you expect from alternate air?

A

Altimeter - higher than actual
A/S - higher than actual
VSI - indicates a climb while in level flight

29
Q

What instruments contain gyroscopes?

A

A/I, hdg indicator, TC

30
Q

Name several types of power sources commonly used to power gyroscopic instruments

A

For cessna - A/I and DG are vacuum driven. TC is electric

31
Q

How does the vacuum system operate?

A

Spins a gyro by drawing a stream of air against rotor vanes to spin the rotor. Typical pressure is 4.5-5.5 “Hg. The pump is often engine-driven.

32
Q

What are two important characteristics of gyroscopes?

A

Rigidity - prevents its asix of rotation from tilting as the earth rotates. Attitude and HDG instruments use this principle.
Precession - applied forces are felt 90 degrees from the point of pressure in the direction of rotation. TC uses this principle.

33
Q

How does the TC operate?

A

Uses precession to indicate direction and approximate rate of turn. The inclinometer is the glass ball sealed in a curved glass tube. It measures relative strength of gravity and force of inertia.

34
Q

What information does a TC provide?

A

Rate of turn, rate of roll and direction of turn. The ball indicates quality of turn (slip or skid).

35
Q

How does the ball indicate a slip in a turn?

A

Ball on the inside of turn; not enough rate of turn for the amount of bank

36
Q

How does the ball indicate a skid in a turn?

A

Ball to the outside of the turn; too much rate of turn for the amount of bank.

37
Q

What is the power source for the TC

A

Can be electric or air. Typically TC is electrically operated.

38
Q

How does the heading indicator work?

A

Works on principle of rigidity in space. Rotor turns in a vertical plane, and is fixed to compass card. As the instrument case and airplane revolve around the vertical axis, the card provides clear and accurate heading information.

39
Q

What are the limits of the heading indicator?

A

Vary by aircraft. Typically about 55 degrees of pitch and 55 degrees of bank. If either limit is exceed the instrument will “tumble” until it is reset with the caging knob. Many modern instruments will not tumble.

40
Q

What type of error is the HDG indicator subject to?

A

Because of precession caused by friction, the HDG indicator will creep. This is affected by the condition of the instrument (dirty bearings, lubrication, etc). Additionally, the gyro is oriented in space and Earth rotates in space at 15 degrees/hour. Thus 15 deg/hr can be expected.

41
Q

How does the A/I work?

A

The gyro is mounted in the horizontal plane and depends on rigidity in space. It remains in horizontal plane as aircraft is pitched or banked.

42
Q

What are the limits of the A/I?

A

Limits vary by aircraft. Typically 100-110 deg for bank, and 60-70 for pitch. If either limit exceeded the instrument will tumble until restabilized. Some modern instruments will not tumble.

43
Q

Is the attitude indicator subject to errors?

A

Generally free from most errors. Some may indicate slightly nose-up during rapid acceleration or nose-down during rapid deceleration. Also possibility of small bank and pitch error after a 180 deg turn. After the turn the A/I will indicate a slight climb and turn opposite the rollout. These errors are small and will correct themselves within a minute after return to S&L flight.

44
Q

How does the mag compass work?

A

Magnets mounted on the compass card align themselves parallel to the Earth’s lines of magnetic force

45
Q

What limits does a mag compass have?

A

The jewel-and-pivot type mounting gives freedom to rotate and tilt up to 18 deg AOB. At steeper AOB the indications are erratic and unreliable.

46
Q

What are the various compass errors?

A

Oscillation error
Deviation error
Variation error
Dip Errors

47
Q

What is oscillation error in the mag compass?

A

Erratic movement of the compass card caused by turbulence or rough control technique

48
Q

What is deviation error in the mag compass?

A

Due to electrical and magnetic disturbances in the cockpit

49
Q

What is variation error in the mag compass?

A

Angular difference between true and magnetic north; reference isogonic lines of variation

50
Q

What are the two dip errors?

A

Acceleration error

Northerly turning error

51
Q

Describe acceleration error

A

On E or W headings when accelerating compass shows a turn to N. When decelerating shows a turn to S.
ANDS
A (accelerate) N (north)
D (Decelerate) S (south)

52
Q

Describe Northerly turning error

A

The compass leads in the south half of a turn and lags in north half of a turn
UNOS
Undershoot North
Overshoot South

Instrument Oral (6 decks)

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