Flight Instruments

Static port blockage

Airspeed indicator - Indicates correctly only at the blockage altitude

• Higher altitudes - indicates lower than it should

• Lower altitudes - Indicates higher than it should

Altimeter - Freezes on the altitude where it was blocked

VSI - Freezes on zero

• When blockage occurs using an alt static source of pressure or break the VSI window this may result in reverse VSI indications

Alt static air instrument indications

Alt static air in inside the cockpit and due to a suction effect from air moving around the cockpit the air inside is lower pressure

Airspeed - Indicates faster speed than it should (less force pushing against diaphragm)

Altimeter - Indicates higher than it should (because air at higher altitudes is lower pressure)

VSI - Momentarily shows a climb and then 0fpm (because air at higher altitudes is lower pressure)

Pitot tube blockage

Ram inlet clogged and drain hole open - ASI goes to zero

• Air drains out drain hole

Both air inlet and drain hole clogged - ASI acts as altimeter

• Use another way of measuring speed like GS on GPS

One of two static ports blocked in dual static port system

Airspeed - Inaccurate during slips and skids

Altimeter - Inaccurate during slips and skids

VSI - Inaccurate during slips and skids

How can you prevent these errorrs from becoming a problem

Cross check with other instruments before taking action as if you didnt notice and ASI was reading erroneous you could stall in IMC
(In a climb verify VSI, altimeter, and ASI all agree)

Anticipate instrument indications before changing phases of flight (In a climb ASI should lower, etc)

What should you do if the pitot tube freezes over?

Pitot heat on

Reference power settings (2300) in lieu of ASI until melted

Cross check straight and level

What should you do if the static port freezes over

Alt static error, pay attention to instrument errors

Break the glass on the VSI to provide static pressure for altimeter and ASI

What is the rate of turn of the aircraft dependent (regardless of airspeed) on?

Horizontal component of lift by increasing bank

Skidding and slipping turns

Skidding turn - (Tail of aircraft being slung to the outside by CF) - CF > HL-

• Load factor increases

Slipping turn - (Wings of aircraft being slung to the outside by HL) - HL > CF

• Load factor decreases

Turn and slip

Gyro in turn and slip is electric

1. Rate of turn

2. Quality of turn

Turn Coordinator

Gyro in turn coordinator at an angle which allows for

1. Rate of turn of the aircraft

2. Quality of the turn (correct angle of bank for rate of turn and shown by inclonometer)

3. Roll rate (by showing how fast the miniature airplane moves)

4. Bank attitude (direction of turn) of airplane (indirect as angle of bank increases turn coordinator is displaced more around its gyro and the miniature aircraft shows a greater deflection or turn)

How does a vacuum system work?

Vacuum draws air that spins the rotor vanes of the gyro like a water wheel

What are the two characteristics of the gyros?

Rigidity - Tendency to remain in the plane of rotation

Precession - Force applied to the gyro is felt 90* in the direction of rotation of the gyro

Heading indicator

Stable, not subject to errors of mag compass

Heading reference - Rotor remains rigid in space and aircraft revolves around the vertical axis and headings are indicated via compass card

Friction and earth’s rotation 15* per hour (no longer points to north, effect worse at poles) cause the gyro to preccess and so we need to realign it every 15min

What are the errors of the heading indicator

Tumbles at 55* of pitch and 55* of bank

Reset with caging knob

Attitude indicator

Gyro mounted on horizontal plane remains rigid in space (horizon bar), aircraft pitches and bank around the gyro

What are the errors of the attitude indicator?

CF causes the gyro to precess to the inside of the turn

180* turn - Slight pitch up and slight turn in the opposite direction
360* turn - Error cancels itself out
Skidding turn - Slight turn in the opposite direction

Acceleration - Slight pitch up (dangerous on TO)
Deceleration - Slight pitch down

What are the errors of the attitude indicator?

Tumbles at 100* to 110* and 60* to 70* of pitch

Incorrect indications until restalized

Compass Turns

Left turn on the turn coodinator - Lower your heading
Right turn on the turn coordinator - Raise your heading

Overshoot the heading for southerly headings by an additional 10* per each 30* increment of heading you are turning to starting with 0* overshoot at W or E

Airspeed indicator

Measures difference between ram air pressure in pitot tube and static pressure in static port

Mechanical linkage converts the expansion and contraction of diaphragm to airspeed

What are the errors of the airspeed indicator

Must have proper flow of system

Position error - Caused by misaslignment between pitot tube and aircraft flight path varies with altitude, airspeed and configuration
Density error - Changes in altitude and temp are not compensated for by the instrument
Compressibility error - Caused by the packing of air into the pitot tube at high airspeeds leading to higher than normal indications. Ignore below 10,000 and 200KIAS

At warmer temps keeping IAS constant does what to TAS

TAS Increases

Altimeter

Uses an aneroid (wafers that expand and contract) barometer to compare air pressure in the static port to a known local pressure set by the pilot

Above FL180 use 2992 all altitudes here are based on pressure alt

What are the errors of the altimeter?

Temperature and pressure errors “High to low watch out below, low to high clear the sky
Altimeter has least error at the surface with standard conditions otherwise change in conditions or altitude result in error

Warmer than ISA the same column of air expands and has more air molecules above the aircraft that exert a greater pressure causing it to think that we are lower

Colder than ISA the same column of air contracts and has less air molecules above the aircraft that exert a smaller pressure causing it to think that we are higher

The errors get worse the more we climb in the atmosphere

How can you determine what altitude will be shown when you adjust the altimeter

Distance from SDP (29.92)

28
29.92
30 - Setting at field (6000)ft, switch for 29.92 would drop 30Hg below the ground making your pressure altitude 5920ft

What should you do if no altimeter setting and received and within what distance can you use an altimeter setting, what is the max altimeter setting avaliable?

Altimeter setting is given so we have the true altitude at field elevation

Set the field elevation

Use an altimeter setting within 100NM

31Hg (reg that also says no aircraft can fly) due to the mechanical limitation of many altimeters

When are pressure altitude and true altitude the same when are pressure altitude and density altitude the same

The only time an altimeter will show 0 is at sea level under standard conditions (2992 and 15)

Pressure altitude and true altitude are the same under standard conditions

Pressure altitude and density altitude are the same under standard temp

When should you make temp corrections to the ISA

Below ISA

Below the temp with the snowflake icon at CTA

When you change the pressure in the Kollsman window on the altimeter does this effect the altitude on the transponder?

No when you adjust the altimeter to the local setting it does not effect the data sent to the Mode C transponder

This is to ensure that all Mode C aircraft are transmitting altitude data referenced to a common pressure level

ATC equitment adjusts displayed altitudes to correct for pressure differences

VSI

Shows rate of climb and deviation from a constant pressure level with lag (6-9 seconds) and rate trend (instant)

Diaphragm and inside of VSI case are vented to the static system, case receies static pressure via calibrated leak and has a change of static pressure slower than the diagphram. As the pressure changes diagphram indicates climb, descent or level flight

The instrument responds to a static pressure change over time

What are the errors of the VSI

Lag

Not accurate until aircraft is stabalized

Sudden change in aircraft attitudes cause erroneous readings

If the VSI shows 100fpm down can you still fly?

Yes, set the new level as your zero reference

The VSI is not required for IFR flight

What are the primary instruments for pitch bank yaw

Pitch -
ASI - In a constant speed climb/descent
AI - Starting a climb/descent
ALT - All other flight conditions

Bank -
TC - In a constant rate turn
AI - Starting a turn
ALT - All other flight conditions

Power -
TACH - Climbing/descending flight conditions & speed changes
ASI - All other flight conditions

FD

Computes desired flight path to be followed

Magenta attitude indicator on G1000

Assists with turns, heading, course, pitch and VS for autopilot or hand flying

AHRS

Gyro information via three axis accelerometers

Replaces AI, DG and TC

May need to establish reference for all attitude changes on ground before taxi

ADC

Pitot static information

Airspeed indicator, altimeter, VSI

PFD

Graphically displays instrument six pack

Continuous scan across instrument

MFD

Displays moving maps, weather, engine information, traffic

FMS

Database of approaches, departure and routes

Gives nav data to FD

Calculates flight data like fuel consumption, time remaining, speed

What is the magnometer

Measures strength of the magnetic field to determine aircraft heading

Gives information to AHRS, AHRS relays to PFD

If your TC becomes INOP how can you make standard rate turns?

15% of your TAS on the attitude indicator

If your heading DG becomes INOP how can you make turns to a heading

Determine if you need to raise or lower your heading on the magnetic compass

If you need to lower your heading turn left on the TC
If you need to raise your heading turn right on the TC

When turning to a South heading overshoot/turning to a North heading undershoot by 10* per 30* increment from E/W you are turning to