Aircraft Systems Related to IFR Operations Flashcards
What type of engine does your aircraft have?
Propeller?
Engine: Textron Lycoming IO-360-L2A, normally aspirated, direct-drive, air-cooled, horizontally opposed, fuel-injected, 4-cylinder engine with 360 cubic inches of displacement, producing 180 BHP at 2700 RPM.
Propeller: McCauley Propeller Systems, fixed pitch, 76 inches in diameter.
Ref: POH Section 1, Descriptive Data
What does “normally aspirated” mean?
The engine relies on atmospheric pressure to draw air into the cylinders, without the use of turbochargers or superchargers. This limits performance at higher altitudes due to reduced air density.
Ref: General engine
knowledge, POH Section 1
What does the mixture do?
The mixture control adjusts the ratio of fuel to air entering the engine. Leaning reduces fuel for high-altitude or cruise operations, while enriching adds fuel for takeoff, climb, and cold conditions. Proper adjustment ensures engine efficiency and prevents fouling or detonation.
Ref: POH Section 1
What is the fuel capacity of the aircraft?
Usable? Unusable?
Total Fuel Capacity: 56 gallons (28 gallons per tank).
Usable Fuel: 53 gallons.
Unusable Fuel: 3 gallons.
Ref: POH Section 1, Fuel
What type of fuel can you use?
What color is it?
What color are other fuel types?
Approved Fuel: 100LL (blue) or 100 (green).
Other Fuel Types:
Jet A: Clear or straw-colored.
Auto gas (not approved for this aircraft): Clear.
Ref: POH Section 1, Fuel
Why do you sample fuel before every flight?
To check for contamination (water, debris) and verify the correct fuel grade and color. Ensures safety and engine performance.
Ref: POH Section 1, Preflight Procedures
What are the two systems that add fuel to an engine?
What system does your aircraft have?
Two Systems: Carbureted and fuel-injected.
Cessna 172S System: Fuel-injected system for precise fuel delivery, reducing icing risks.
Ref: POH Section 1, Engine
What does a carburetor do?
Mixes fuel with air to create a combustible mixture for the engine. It operates using venturi suction to atomize fuel. Not applicable to the fuel-injected Cessna 172S.
Ref: General knowledge
What is carb ice?
How is it recognized?
When can it take place?
Definition: Ice formation in the carburetor due to rapid cooling of air during fuel vaporization.
Recognition: Loss of RPM (fixed pitch) or manifold pressure (constant speed).
Conditions: Common in high humidity, temperatures between 20°F and 70°F.
Ref: General knowledge (Not applicable to 172S due to fuel injection).
What is induction icing?
Are fuel-injected systems susceptible to it?
Ice forms in the air intake system, reducing airflow to the engine. Fuel-injected systems are less susceptible but not immune, particularly in freezing rain or severe conditions.
Ref: General knowledge
Does your aircraft have any anti-icing or deicing equipment?
Anti-icing: Pitot heat, windshield defrost.
Deicing: Not equipped with airframe deicing systems.
Ref: POH Section 7, Systems Description
What are some limitations to anti-icing and deicing equipment?
Limited effectiveness in severe icing conditions.
May not protect all surfaces (e.g., wings).
Relying solely on anti-icing can lead to dangerous situations in known icing.
Ref: General systems knowledge
Explain the electrical system.
28-volt DC system powered by a 60-amp alternator.
24-volt main battery and 24-volt standby battery for essential systems during alternator failure.
Circuit breakers protect the system from overload.
Ref: POH Section 7, Electrical System
What indications will be displayed during an alternator failure?
Alternator annunciator light illuminates.
Voltage indication drops on the electrical meter.
Essential systems may lose power if the battery depletes.
Ref: POH Section 3, Emergency Procedures
What instruments operate from the pitot-static system?
Airspeed Indicator: Requires both pitot and static pressures.
Altimeter: Uses static pressure to measure altitude.
Vertical Speed Indicator (VSI): Uses static pressure changes to indicate the rate of climb or descent.
Ref: PHAK Chapter 7
Which instruments are connected to the pitot tube?
The static port?
Pitot Tube: Provides ram air pressure to the airspeed indicator.
Static Port: Supplies static pressure to the altimeter, VSI, and airspeed indicator.
Ref: PHAK Chapter 7
How does an altimeter work?
The altimeter uses static pressure to compare the ambient air pressure to a sealed aneroid wafer calibrated to standard atmospheric pressure (29.92 inHg). As the aircraft climbs or descends, changes in static pressure cause the wafers to expand or contract, moving the hands on the altimeter display.
Ref: PHAK Chapter 7
What is the maximum allowable error for an altimeter when used for IFR flight?
Is this recommended or mandated?
The altimeter must be within 75 feet of the field elevation when set to the local altimeter setting. This is a mandated requirement for IFR flight to ensure altitude accuracy.
Ref: FAR 91.411, AIM 7-2-3
Define the following types of altitude:
Indicated Altitude: Read directly from the altimeter when set to the local altimeter setting.
Pressure Altitude: Altitude above the standard datum plane (29.92 inHg). Used for performance calculations.
True Altitude: Actual altitude above mean sea level (MSL). Airports and terrain elevations are expressed in true altitude.
Density Altitude: Pressure altitude corrected for nonstandard temperature. Indicates aircraft performance.
Absolute Altitude: Height above ground level (AGL).
Ref: PHAK Chapter 7
How does the airspeed indicator work?
The airspeed indicator measures the difference between ram air pressure from the pitot tube and static pressure from the static port. The diaphragm inside the instrument expands or contracts as the difference changes, moving the needle to indicate airspeed.
Ref: PHAK Chapter 7
Define the following types of airspeed:
Indicated Airspeed (IAS): Airspeed read directly from the instrument, uncorrected for errors.
Calibrated Airspeed (CAS): IAS corrected for instrument and position errors.
Equivalent Airspeed (EAS): CAS corrected for compressibility effects at high speeds.
True Airspeed (TAS): EAS corrected for altitude and temperature. Represents actual speed through the air.
Groundspeed (GS): TAS adjusted for wind, representing the speed over the ground.
Ref: PHAK Chapter 7
How does the vertical speed indicator (VSI) work?
The VSI measures the rate of change in static pressure. A calibrated leak allows static pressure to change inside the diaphragm and casing at different rates. This difference causes the needle to show climb or descent rates in feet per minute (FPM).
Ref: PHAK Chapter 7
What are some limitations of the VSI?
Lag: A delay of 6-9 seconds to display accurate climb/descent rates due to the calibrated leak.
Errors: Rapid pressure changes (e.g., turbulence) can cause inaccurate readings.
Ref: PHAK Chapter 7
What instruments are affected if the static port freezes over?
What are the instrument errors?
Affected Instruments: Altimeter, VSI, airspeed indicator.
Errors:
Altimeter: Will freeze at the last altitude.
VSI: Will read zero regardless of climb or descent.
Airspeed Indicator: Reads incorrectly—higher than actual during descent and lower during climb.
Ref: PHAK Chapter 7
What corrective action should you take if your static port freezes over?
Activate the alternate static source (if equipped).
If no alternate static source is available, break the glass on the VSI as a last resort to access static pressure.
Ref: PHAK Chapter 7
What indications should you expect if you use alternate air?
Altimeter: Reads slightly higher than actual altitude.
Airspeed Indicator: Reads slightly faster than actual airspeed.
VSI: Shows a momentary climb.
Ref: PHAK Chapter 7
What instruments are affected when the pitot tube, ram air inlet, and drain hole freeze?
What are the instrument errors?
Airspeed Indicator:
If only the ram air inlet freezes: Airspeed drops to zero.
If both the ram air inlet and drain hole freeze: Airspeed indicator behaves like an altimeter, increasing during a climb and decreasing during descent.
Ref: PHAK Chapter 7
What would be the indication if the pitot tube entry hole becomes partially blocked?
The airspeed indicator may show erratic or incorrect readings, depending on the extent of the blockage.
Ref: PHAK Chapter 7
What corrective action should you take if your pitot tube freezes?
Turn on the pitot heat to melt the ice.
Avoid flying into further icing conditions if possible.
Ref: PHAK Chapter 7
What instruments contain gyroscopes?
Attitude Indicator
Heading Indicator
Turn Coordinator
Ref: PHAK Chapter 7
What are the two principles of operation for gyroscopes?
Rigidity in Space: A spinning gyroscope remains fixed in its plane of rotation.
Precession: A force applied to a spinning gyroscope is felt 90° ahead in the direction of rotation.
Ref: PHAK Chapter 7
How does the vacuum system operate?
The vacuum system uses an engine-driven pump to create suction, drawing air through the system.
Air passes through filters and spins the gyroscopes in the attitude and heading indicators.
Ref: PHAK Chapter 7
What instruments work off of a vacuum system?
Attitude Indicator
Heading Indicator
Ref: PHAK Chapter 7
What are pendulous vanes?
Pendulous vanes are part of the attitude indicator. They help maintain alignment of the gyro by directing airflow to correct for deviations.
Ref: PHAK Chapter 7
A vacuum failure affects which instruments?
How would you notice the failure?
Affects the attitude and heading indicators.
You would notice:
Attitude Indicator: Slowly tumbles or becomes unreliable.
Heading Indicator: Stops precessing correctly.
Vacuum annunciator light or gauge indicating low vacuum.
Ref: PHAK Chapter 7
How does the turn coordinator operate?
Uses an electrically driven gyro mounted at an angle to sense rate of turn and roll.
The ball in the inclinometer shows coordination of the turn.
Ref: PHAK Chapter 7
What is an inclinometer?
A liquid-filled tube with a ball used to indicate coordination of a turn. The ball is centered during coordinated flight.
Ref: PHAK Chapter 7
What information does the turn coordinator provide?
Rate of turn (standard rate or half-standard rate).
Quality of turn (coordinated, slip, or skid).
Ref: PHAK Chapter 7
How does the heading indicator work?
Operates on the principle of rigidity in space. The gyro remains fixed while the aircraft rotates around it, providing a stable heading reference.
Requires periodic alignment with the magnetic compass due to gyro precession.
Ref: PHAK Chapter 7
How does the attitude indicator work?
Uses a gyro mounted horizontally.
Shows pitch and roll by detecting aircraft movement relative to the horizon bar.
Adjustments are made via pendulous vanes to counter drift.
Ref: PHAK Chapter 7
Are the heading and attitude indicators mounted vertically or horizontally?
Heading Indicator: Horizontally mounted.
Attitude Indicator: Vertically mounted.
Ref: PHAK Chapter 7
What are the limitations to the attitude indicator?
The heading indicator?
Attitude Indicator:
Limited pitch and bank angles (e.g., typically 60° pitch and 100° bank). Beyond limits, the instrument may tumble.
Susceptible to gyro precession.
Heading Indicator:
Precession causes gradual drift. Requires periodic realignment with the magnetic compass.
Ref: PHAK Chapter 7
What is the AHRS?
AHRS (Attitude and Heading Reference System) is a system of sensors that provides attitude (pitch and roll), heading, and rate of turn information to the cockpit displays. It uses accelerometers, gyroscopes, and magnetometers to replace traditional gyroscopic instruments.
Ref: PHAK Chapter 8
What is the ADC?
ADC (Air Data Computer) processes data from the pitot-static system and temperature sensors to calculate altitude, airspeed, vertical speed, and true airspeed. It replaces mechanical pitot-static instruments with digital data for cockpit displays.
Ref: PHAK Chapter 8
What is the FMS?
What is the function of the FMS?
FMS (Flight Management System) is an integrated navigation and performance management tool.
Function: It manages flight plans, navigation, fuel management, and performance calculations. The FMS interfaces with GPS, VOR/DME, and other sensors to provide accurate positioning and guidance.
Ref: Instrument Flying
Handbook (IFH) Chapter 6
What is EFIS?
EFIS (Electronic Flight Instrument System) is an integrated system that replaces traditional analog instruments with digital displays, including the PFD (Primary Flight Display) and MFD (Multi-Function Display).
Ref: IFH Chapter 6
Define PFD. What information does it display?
PFD (Primary Flight Display): Displays critical flight information in a consolidated format, including:
Attitude
Airspeed
Altitude
Vertical speed
Heading
Rate of turn
Flight director cues.
Ref: PHAK Chapter 8
Define MFD. What information does it display?
MFD (Multi-Function Display): Provides supplemental flight information such as:
Moving maps
Weather data
Traffic information
Engine monitoring
Navigation aids.
Ref: PHAK Chapter 8
What would happen if the PFD failed?
The critical flight information (e.g., attitude, altitude, airspeed, heading) would no longer be displayed.
Most systems provide reversionary mode, where the MFD can assume PFD functions. Pilots must know how to activate this mode.
Ref: PHAK Chapter 8
What display information will be affected when an ADC failure occurs?
Airspeed, altitude, vertical speed, and true airspeed will be lost or display errors.
The PFD may show red Xs or other failure indications on these instruments.
Ref: PHAK Chapter 8
What display information will be affected when an AHRS failure occurs?
Attitude, heading, and rate of turn information will be lost or inaccurate.
Failure indications (e.g., red Xs) may appear on the PFD for these parameters.
Ref: PHAK Chapter 8
What is the function of the magnetometer?
What happens if it fails?
Function: The magnetometer measures the Earth’s magnetic field and provides heading information to the AHRS.
Failure: Heading information becomes unreliable, and the PFD will show a failure indication for the heading indicator. The standby magnetic compass must be used for heading references.
Ref: PHAK Chapter 8
How does the magnetic compass work?
The magnetic compass uses a magnetized needle or bar suspended in fluid to align with Earth’s magnetic field. It indicates the aircraft’s heading relative to magnetic north.
Ref: PHAK Chapter 8
What are the various compass errors?
Deviation: Magnetic interference from aircraft
systems.
Variation: Difference between true north and magnetic north.
Magnetic Dip: Caused by Earth’s magnetic field curvature.
Oscillation: Erratic movement due to turbulence or vibrations.
Turning Errors: Errors caused by magnetic dip during turns (e.g., UNOS).
Acceleration Errors: Errors caused by acceleration or deceleration (e.g., ANDS).
Ref: PHAK Chapter 8
What are the magnetic dip errors?
Errors caused by the magnetic field pulling the compass needle downward, especially at higher latitudes. Includes turning errors (UNOS) and acceleration errors (ANDS).
Ref: PHAK Chapter 8
Where is the magnetic compass most accurate?
When flying straight and level, unaccelerated, and without turning.
Ref: PHAK Chapter 8
What is ANDS?
UNOS?
ANDS (Accelerate North, Decelerate South): In the northern hemisphere, acceleration shows a false turn toward the north; deceleration shows a false turn toward the south.
UNOS (Undershoot North, Overshoot South): When turning, undershoot the heading for north turns and overshoot for south turns.
Ref: PHAK Chapter 8
What does VOR stand for?
VHF Omnidirectional Range.
Ref: AIM 1-1-3
What are the different classes of VOR stations?
Terminal (T): 25 NM range, 1,000–12,000 ft AGL.
Low Altitude (L): 40 NM range, 1,000–18,000 ft AGL.
High Altitude (H): Up to 130 NM range, depending on altitude.
Ref: AIM 1-1-8
What are the different service volumes?
Defined ranges and altitudes for VOR reception.
Terminal: 25 NM.
Low Altitude: 40 NM.
High Altitude: Up to 130 NM.
Ref: AIM 1-1-8
What are some VOR limitations?
Line-of-sight only.
Signal distortion near obstacles or terrain.
Cone of confusion directly over the station.
Reverse sensing on some indicators.
Ref: AIM 1-1-3
How does a VOR work?
The VOR transmits two signals: a reference phase and a variable phase. The aircraft’s receiver determines the difference in phases to calculate the radial.
Ref: AIM 1-1-3
How do you determine if a VOR is working?
Listen for the Morse code identifier. If no code is transmitted, the VOR may be out of service.
Perform a VOR check as required by FAR 91.171.
Ref: AIM 1-1-3
What does a single tone every 30 seconds mean on a VORTAC?
The VORTAC is undergoing maintenance and should not be used for navigation.
Ref: AIM 1-1-3
What is a VORTAC and a TACAN? How do they differ?
VORTAC: Combines VOR and TACAN, providing VOR navigation for civilian aircraft and TACAN features for military use.
TACAN: Tactical Air Navigation, used by the military for precise navigation and DME.
Ref: AIM 1-1-3
How many degrees of deviation does each dot represent?
2 degrees of deviation per dot on the CDI (Course Deviation Indicator).
Ref: AIM 1-1-3
What is a full-scale deflection?
Indicates a deviation of 10 degrees or more from the selected course.
Ref: AIM 1-1-3
You are 60 miles from the station, and you have a one-dot deflection.
How far are you off course?
1 NM off course (1 dot = 2°; at 60 NM, each degree is 1 NM).
Ref: AIM 1-1-3
What is DME?
How does it work?
DME (Distance Measuring Equipment) measures the slant-range distance to a station by timing the delay between signals sent and received by the aircraft.
Ref: AIM 1-1-7
Where can you find DME?
Found on VORTACs, some VOR/DME stations, and ILS installations.
Ref: AIM 1-1-7
Describe slant range. How does it work?
Slant range is the distance measured diagonally from the aircraft to the station. It is affected by the aircraft’s altitude and distance from the station.
Ref: AIM 1-1-7
Where would slant range error be most prominent? Least prominent?
Most Prominent: When close to the station at high altitudes.
Least Prominent: At lower altitudes and greater distances.
Ref: AIM 1-1-7
What is reverse sensing?
Occurs when flying a course using a VOR indicator set to the reciprocal course. The CDI will deflect opposite to the correction needed. Modern systems with automatic sensing mitigate this issue.
Ref: AIM 1-1-3
Is a VOR approach precision or non-precision?
A VOR approach is a non-precision approach because it provides only lateral guidance to the runway and no vertical guidance.
Ref: AIM 5-4-5
When is an approach considered straight in?
When the final approach course aligns within 30° of the runway centerline (15° for GPS).
Ref: AIM 5-4-6
When is an approach considered a circling approach?
When the final approach course does not meet the alignment criteria for a straight-in approach or when circling is required to land on a different runway.
Ref: AIM 5-4-20
What is the purpose of a timed approach?
To execute an approach when radar is unavailable, timing is used to ensure aircraft separation and safe descent to the missed approach point (MAP).
Ref: AIM 5-4-9
What are the VOR receiver checks? (91.171)
Airborne Checkpoints: ±6°.
Ground Checkpoints: ±4°.
VOT (VOR Test Facility): ±4°,
must center on 180° TO or 360° FROM.
Dual VOR Check: ±4° between receivers.
Ref: FAR 91.171
Give a brief description of the Global Positioning System.
GPS is a satellite-based navigation system that provides precise positioning and timing data to users worldwide. It uses a constellation of satellites transmitting signals that are received by GPS receivers to determine location, altitude, and velocity.
Ref: AIM 1-1-17
How many satellites do we have in orbit?
The GPS constellation typically consists of 24 satellites, with spares in orbit.
Ref: AIM 1-1-17
How many do we need for a 3D position? For RAIM?
3D Position (latitude, longitude, altitude): 4 satellites.
RAIM: 5 satellites (or 4 with baro-aiding).
Ref: AIM 1-1-17
What is RAIM? How does it work?
RAIM (Receiver Autonomous Integrity Monitoring) checks GPS signals for reliability by comparing measurements from multiple satellites. If RAIM detects errors, the GPS will alert the pilot.
Ref: AIM 1-1-17
What is the purpose of baro-aiding?
Baro-aiding allows the GPS receiver to use pressure altitude data to reduce the number of satellites needed for RAIM, improving reliability.
Ref: AIM 1-1-17
What is WAAS?
WAAS (Wide Area Augmentation System) enhances GPS accuracy, integrity, and availability by using ground stations to monitor GPS signals and provide corrections via satellites. It supports precision approaches like LPV.
Ref: AIM 1-1-18
How often are GPS databases required to be updated?
Answer: Every 28 days.
Ref: AIM 1-1-20
Can a GPS with an expired database be used for navigation under IFR? How often must this be completed?
Yes, but only if the database is verified as current for the planned route. IFR-certified GPS must have updates verified before use.
Ref: AIM 1-1-19
Where would you find the location of airborne checkpoints, ground checkpoints, and VOT testing stations?
Chart Supplement (formerly A/FD).
Ref: AIM 1-1-4
You complete a VOR check. What information must you include in your signoff? (91.171)
Date, place, bearing error, and pilot signature.
Ref: FAR 91.171
What is the allowable error for the receiver checks? (91.171)
Ground Check: ±4°.
Airborne Check: ±6°.
Ref: FAR 91.171
Is there a difference between GPS distance and DME distance?
Yes. GPS measures actual horizontal distance, while DME measures slant range, including altitude.
Ref: AIM 1-1-17
Which ground navigational aids can GPS replace?
VOR, DME, and NDB, if appropriately certified GPS equipment is used.
Ref: AIM 1-1-17
Can you use GPS as a sole source for IFR navigation?
Yes, if it is IFR-certified and RAIM is available.
Ref: AIM 1-1-17
Can your filed alternate have a GPS approach?
Yes, but only if the primary destination does not rely solely on GPS.
Ref: AIM 1-1-20
What are two things you should do before flight to check if GPS can be used for your route?
Verify database currency.
Check for NOTAMs related to GPS outages or restrictions.
Ref: AIM 1-1-20
What are the differences between the various RNAV approaches?
LPV: Precision-like vertical guidance.
LNAV/VNAV: Vertical guidance, lower minima than LNAV.
LNAV: Lateral guidance only, higher minima.
LP: Localizer-like performance without vertical guidance.
Ref: AIM 1-1-20
Are GPS approaches considered precision or non-precision?
Most are non-precision (e.g., LNAV). LPV approaches are considered APV (Approach with Vertical Guidance), not full precision.
Ref: AIM 1-1-20
During a GPS approach, how many miles before the FAF should you have an APR indication?
2 NM before the Final Approach Fix (FAF).
Ref: AIM 1-1-20
What do you do if that does not happen?
Execute the missed approach. GPS guidance beyond the FAF is not reliable without APR mode.
Ref: AIM 1-1-20
What if it happens inside the FAF?
Do not descend further. Execute the missed approach if unable to re-establish proper APR guidance.
Ref: AIM 1-1-20
What are the components of an ILS? (AIM 1-1-9)
The ILS consists of:
Localizer:
Provides lateral guidance to the runway centerline.
Glide Slope: Provides vertical guidance to the touchdown zone.
Marker Beacons: Indicate specific points along the approach path.
Approach Lighting System (ALS): Enhances visual guidance during low visibility.
Ref: AIM 1-1-9
What is the purpose of marker beacons?
Marker beacons indicate key points along the approach path, such as the outer marker (OM), middle marker (MM), and sometimes the inner marker (IM). They provide audible and visual signals to help pilots verify position during the ILS approach.
Ref: AIM 1-1-9
What are the approximate distances from the landing threshold to the outer, middle, and inner marker?
Outer Marker (OM): Approximately 4–7 NM from the runway threshold.
Middle Marker (MM): Approximately 3,500 feet from the threshold.
Inner Marker (IM): Located between the MM and the runway, usually near the threshold, used for Category II/III approaches.
Ref: AIM 1-1-9
How would you know you have passed the outer marker?
What point does this marker represent?
Indications:
Blue light illuminates on the marker beacon panel.
Audible Morse code tone (dash-dash-dash) is heard.
Purpose: Indicates the position where the aircraft intercepts the glide slope on an ILS approach.
Ref: AIM 1-1-9
How would you know you have passed the middle marker?
What point does this marker represent?
Indications:
Amber light illuminates on the marker beacon panel.
Audible Morse code tone (dot-dash-dot-dash) is heard.
Purpose: Indicates the decision altitude (DA) point for Category I ILS approaches.
Ref: AIM 1-1-9
When is an inner marker used? How would you know if you’ve passed one?
Use: Found on Category II/III approaches, it indicates the point where the aircraft is at or near the DA/DH for these approaches.
Indications:
White light illuminates on the marker beacon panel.
Audible Morse code tone (dot-dot-dot-dot) is heard.
Ref: AIM 1-1-9
How do you know if you have passed a marker beacon?
Visual indications: Colored lights on the marker beacon panel (blue for OM, amber for MM, white for IM).
Audible signals: Distinct Morse code tones for each marker.
Ref: AIM 1-1-9
What can be used as a substitute for the outer marker? (91.175)
DME (Distance Measuring Equipment).
Compass locator.
Precision Approach Radar (PAR).
GPS Waypoints.
VOR radials.
These substitutes provide equivalent position information to the outer marker.
Ref: FAR 91.175
Where is the localizer antenna located? What type of guidance does it offer?
Location: At the far end of the runway, opposite the approach end.
Guidance: Provides lateral guidance to align the aircraft with the runway centerline.
Ref: AIM 1-1-9
What is the angular width of the localizer?
The localizer’s angular width is typically 3–6°, ensuring a total coverage of about 700 feet at the runway threshold.
Ref: AIM 1-1-9
What is the coverage range of the localizer?
18 NM within 10° of the centerline.
10 NM within 35° of the centerline.
Ref: AIM 1-1-9
Where can you find the glideslope antenna?
Located approximately 750–1,250 feet down the runway from the approach threshold and offset about 400–600 feet from the runway centerline.
Ref: AIM 1-1-9
What is the typical range of the glideslope? Slope?
Range: Up to 10 NM.
Slope: Typically set at 3°, providing vertical guidance to the touchdown zone.
Ref: AIM 1-1-9
Are there sensitivity differences with the CDI when tuned to a VOR vs. a LOC?
Yes:
VOR: Each CDI dot represents 2° of deviation.
Localizer: Each CDI dot represents 0.5° of deviation, making it four times more sensitive than a VOR.
Ref: AIM 1-1-9
What is a compass locator? Where is it normally installed?
Compass Locator: A low-power NDB (Non-Directional Beacon) used in conjunction with an ILS.
Installation: Typically located at the outer marker or middle marker to aid in approach navigation.
Ref: AIM 1-1-9
What is the purpose of an Approach Light System (ALS)?
The ALS provides a visual transition from instrument-based navigation to visual references needed for landing. It helps pilots align with the runway and judge the approach path in low-visibility conditions.
Ref: AIM 2-1-2
