Instrument Systems Orals/IPCand Knowledge Test

Randy SchoephoersterAir Trek North

2013

AgendaInstrument Systems

• Compass• Heading Indicator/Directional Gyro• Turn Coordinator• Altimeter• Attitude Indicator• Pitot-Static System

CAUTION…………………..

• The sole purpose of this class is to expedite your passing the FAA

knowledge test. With that said, all extra material not directly tested on

the FAA knowledge test is omitted, even though much more information

and knowledge is necessary to fly safely. Consult the FAR/AIM (CFR) and

other FAA Handbooks for further information along with a Flight

Instruction course.

• www.sportys/faatest

CFR 61.65 (d) Instrument Practical Test Requirements

• (d) Aeronautical experience for the instrument-airplane rating. A person who applies for an instrument-airplane rating must have logged:– (1) Fifty hours of cross country flight time as pilot in command, of which 10

hours must have been in an airplane; and– (2) Forty hours of actual or simulated instrument time in the areas of operation

listed in paragraph (c) of this section, of which 15 hours must have been received from an authorized instructor who holds an instrument-airplane rating, and the instrument time includes:• (i) Three hours of instrument flight training from an authorized instructor in an airplane

that is appropriate to the instrument-airplane rating within 2 calendar months before the date of the practical test; and

• (ii) Instrument flight training on cross country flight procedures, including one cross country flight in an airplane with an authorized instructor, that is performed under instrument flight rules, when a flight plan has been filed with an air traffic control facility, and that involves—– (A) A flight of 250 nautical miles along airways or by directed routing from an air traffic

control facility;– (B) An instrument approach at each airport; and

– (C) Three different kinds of approaches with the use of navigation systems.

Instrument Rating RQT’s

• Private Pilot • Knowledge Test • 50hr Cross Country PIC • 40hr Actual or Simulated – 15 hrs w/CFII • 250NM IFR Flight Instrument

– Aprroach at each Airport – 3 Different Kinds of Approaches

• 3hrs with CFII in preceding 2 calendar months

Pitot Static System

Airspeed Indicator

• Ram Air enters the Pitot Tube• Static Pressure enters the Casing of the Airspeed Indicator• Higher pressure from the Pitot Tube expands the wafer, drives the gears, and

indicates higher airspeed• Lower pressure from the Pitot Tube contracts the wafer, drives the gears, and

indicates lower airspeed.• When the pressure on the Pitot Tube equals the Static pressure, the Airspeed

Indicator reads zero• What happens when the pitot tube and the drain hole freeze?

Altimeter

• 29.92” HG inside the wafer• Static Pressure enters the case of the Altimeter• High Static Pressure compresses the wafer and drives the

gears and indicates low altitude• Low Static pressure allows the wafer to expand, drives

the gears to indicate high altitude• If the Static port gets clogged, the altitude indicator

freezes• What happens if the alternate static air is used?

Altimeter• Altimeter indicates True Altitude at the field elevation if the local altimeter

setting is used in an accurate altimeter• Atmospheric pressure decreases about 1in Hg for every 1000ft increase in

altitude– When changing the kollsman window from 30.11” to 29.96”, the altimeter will

decrease 150ft• With the current altimeter setting, the altimeter should read within 75ft of

actual altitude to be acceptable• If pressure or temp becomes lower without adjusting the Kollsman window,

your airplane will be lower than the altimeter indicates.• Pressure altitude is the altitude read on the altimeter when set to 29.92” (The

standard datum plane)– This is the altitude used about 18,000ft (Class A)

• Pressure altitude and density altitude are the same at standard temperature• The local altimeter setting should be used by all pilots in a particular area

primarily to provide for better vertical separation of aircraft.

When Flying from High to LowLook out Below!!!!

When Flying from High to LowLook out Below!!!!!

Reading an Altimeter

Reading an Altimeter

VSIVertical Speed Indicator

• Trend Instrument due to the leak• Measures instantaneous static pressure chg compared to the average static pressure

change over last 6-9 seconds.• As Static Pressure is lower, then wafer contracts, driving the gears, and indicates

positive rate of climb• As Static Pressure is higher, then wafer expands, driving the gears to indicate rate of

descent• If the static port becomes clogged, then the pressure inside the wafer and the

pressure inside the instrument tube will be the same and thus, the VSI indicates 0 climb or descent

• What happens if alternate air is used? Short term? Long term?• If the VSI shows a descent of 100ft while on the taxiway during run-up, what can you

do?

Blocked Pitot Tube/Static Port Effects

Blocked Static Port Blocked Pitot and Drain Hole

Blocked Pitot, open Drain Hole

Airspeed Indicator Acts as a reverse Altimeter

Acts as an Altimeter

Airspeed = Zero

Altimeter Frozen at altitude when Static Port was Blocked

N/A N/A

VSI Reads Zero N/A N/A

Mode C Same as Altimeter N/A N/A

Alternate Static Air• Many airplanes have an alternate static air vent in the event the static

port becomes plugged• Alternate static air is taken from inside the cabin• Since air is moving rapidly across the fuselage, bernouli’s indicates that

the cabin air pressure will be slightly lower than the outside air pressure• Due to bernoulli’s, Altimeter, Mode C and Altimeter will read slightly high• When first using alternate static air, the VSI will initially show a climb

(due to lower pressure), but will then indicate properly• If Alternate Static Air does not work, or if not installed, break the glass on

the VSI– Direct access to the Static Line– Not required for IFR flight

Turn Indicator Vs Coordinator

Powered by Electrical System

Turn Indicator Turn Coordinator

Rate Of Turn Rate of Turn

Rate of Roll Rate of Roll

Vacuum System/Gyro Systems

Turn Coordinator

Gyro Characteristics

• Spin at 20,000+ RPM– Takes about 5 minutes to spin

up• Want to stay in the same place

– Resistance to deflection of the spinning wheel

– Called Rigidity in Space• A force applied results in a

reaction 90 degrees in the direction of the rotation

Gyroscopes

• Turn the battery ON (Master) and listen for unusual noises after the battery is turned on but before the engine is started

Gyro Errors

• Attitude Indicator (A/I)– Indicates climb during acceleration– Indicates descent during deceleration– In a 180 degree turn, shows climb and roll in opposite direction

• Directional Guidance (D/G)– Precesses due to friction– Max 3 degrees per 15 minutes– Can tumble at

• >60 degree pitch• >100 degree bank

– Set the DG to the magnetic compass 5 minutes after the engine has started. Why?

Attitude Indicate Errors

• Acceleration Error– Indicates a climb

• Deceleration Error– Indicates a descent

• Skidding Turn Error– Indicates a turn in the opposite direction upon return to

straight and level• Steep Turn Error– Most pronounced at 1800

– Shows a climb and a turn in the opposite direction

Remote Indicating Compass (RIC)

• Slave Mode puts the RIC to track the compass.

• Free Gyro Mode allows you to adjust the RIC to the magnetic compass

• A left deflection means you push the clockwise button

Remote Indicating CompassTest Supplement Book

• Depressing the Clockwise button will rotate the compass card to the right to eliminate left error

• If the heading on the RIC is to the left of that desired, press the counter clockwise button

Magnetic Compass Errors• Turns greater than 18 degree bank may cause compass to hang up on edge of card• UNOS Turning Errors

– Undershoot North, Overshoot South– 30 deg error at North and South– Zero deg error at East and West

• ANDS Acceleration/Deceleration Errors– Accelerate North, Decelerate South– Due to Counter Weight being heavier than magnet

• Body at rest stays at rest• Body in motion stays in motion

• Turbulence causes Compass to oscillate• Deviation

– Errors due to systems in the airplane– Compass Card correction

• Variation– Difference between True North and Magnetic North– Isogonic lines on charts minus for East, add for West

• Timed Turns– 3 degs/second

Dip Errors (Turning)

Compass Acceleration Error

Magnetic Compass

• On the taxi check, the magnetic compass should swing freely and indicate known headings

• On a South heading, you turn right.– The compass will indicate a turn to the right but at a faster

rate than is occurring (UNOS) causing you to overshoot.• On a North heading, you turn right.

– The compass will indicate a turn to the left (UNOS) causing you to undershoot.

• On a West or East heading, you turn right or left.– The compass will indicate the correct magnetic heading

Mach Meter

• Shows the ratio of aircraft true airspeed to the speed of sound

PFD vs MFDGlass Cockpits Enhance Situational Awareness