IFR Terms, Definitions, and Notes
Minimum Obstruction Clearance Altitude (MOCA) - The lowest published altitude in effect between radio fixes on VOR airways, off-airway routes, or route segments which meets obstacle clearance requirements for the entire route segment and which ensures acceptable navigational signal coverage only within 25 statute (22 nautical) miles of a VOR.
Minimum Reception Altitude (MRA) - The lowest altitude at which an airway intersection can be determined.
Minimum Crossing Altitude (MCA) - The lowest altitude at certain fixes at which an aircraft must cross when proceeding in the direction of a higher MEA.
Maximum Authorized Altitude (MAA) - A published altitude representing the maximum usable altitude or FL for an airspace structure or route segment.
Minimum Safe Altitude (MSA) - The minimum altitude depicted on approach charts which provides at least 1,000 feet of obstacle clearance for emergency use within a specified distance from the listed navigation facility or waypoint.
Off-Route Obstruction Clearance Altitude (ORCA) - Provides obstruction clearance with a 1,000 foot buffer in non-mountainous terrain areas and a 2,000 foot buffer in designated mountainous areas within the United States . Might not provide signal coverage from ground-based navigational aids, ATC radar, or communications coverage.
Minimum Vectoring Altitude (MVA) - Lowest MSL altitude at which an IFR aircraft can be vectored by a radar controller except as otherwise authorized for radar approaches, departures, and missed approaches. Meets IFR obstacle clearance criteria and may be lower than the published MEA along an airway. May be used for vectoring only upon controller’s determination that an adequate radar return is being received from the aircraft being controlled. Not charted for pilots, is typically only available to controllers.
Initial Approach Fix (IAF) - The fixes depicted on IAP charts that identify the beginning of the initial approach segment.
Procedure Turn - The maneuver prescribed when it is necessary to reverse direction to establish an aircraft on the intermediate approach segment or final approach course.
NoPT (No Procedure Turn) - Used with the appropriate course and altitude to denote the procedure turn is not required.
Final Approach Fix (FAF) - The fix from which the IFR final approach to an airport is executed, which identifies the beginning of the final approach segment.
Glide-slope Intercept Altitude - The minimum altitude of an intermediate approach segment prescribed for a precision approach that ensures obstacle clearance.
Stepdown Fix - Permits additional descent within a segment of an IAP by identifying a point at which an obstacle has been safely overflown.
Minimum Descent Altitude (MDA) - The lowest altitude (in feet MSL) to which descent is authorized in execution of a nonprecision IAP.
Missed Approach Point (MAP) - A point prescribed in each instrument approach at which a missed approach required visual reference has not been established.
Runway Visual Range (RVR) - The instrumentally-derived horizontal distance a pilot should be able to see down the runway from the approach end, based on either the sighting of high-intensity runway lights, or the visual contrast of other objects.
Alternate Airport - Designated in an IFR flight plan, provides a suitable destination if a landing at the intended airport becomes inadequate.
Touch down zone elevation (TDZE) - The highest elevation in the first 3,000 feet of the landing surface, TDZE is indicated on the IAP chart when straight-in landing minimums are authorized.
Clearance Void Time - Used by ATC to advise an aircraft that the departure clearance is automatically canceled if takeoff is not made prior to a specified time. The pilot must obtain a new clearance or cancel the IFR flight plan if not off by the specified time.
Clearance - Allows an aircraft to proceed under specified traffic conditions within controlled airspace, for the purpose of providing separation between known aircraft.
Cruise Clearance - Used in an ATC clearance to allow a pilot to conduct flight at any altitude from the minimum IFR altitude up to and including the altitude specified in the clearance. Also authorizes a pilot to proceed to and make an approach at the destination airport.
Clearance Delivery - Control tower position responsible for transmitting departure clearances to IFR flights.
Departure Procedure (DP) - Preplanned IFR ATC departure/obstacle avoidance procedures, published for pilot use in textual and graphic format.
Compass Locator - A low-power low- or medium-frequency radio beacon installed at the site of the outer or middle marker of an ILS.
Holding - A predetermined maneuver that keeps aircraft within a specified airspace while awaiting further clearance from ATC.
Standard Holding Pattern - A holding pattern in which all turns are made to the right.
Minimum Descent Altitude (MDA) - The lowest altitude to which descent is authorized on final approach, or during circle-to-land maneuvering in execution of a nonprecision approach.
Decision Altitude (DA) - A specified altitude in the precision approach, charted in ‘feel MSL’, at which a missed approach must be initiated if the required visual reference to continue the approach has not been established.
Decision Height (DH) - A specified altitude in the precision approach, charted in ‘height above threshold elevation’, at which decision must be made to either continue the approach or to execute a missed approach.
Circling Approach - A maneuver initiated by the pilot to align the aircraft with a runway for landing when a straight-in-landing from an instrument approach is not possible or is not desirable.
Precipitation Static - A form of radio interference caused by rain, snow, or dust particles hitting the antenna and inducing a small radio-frequency voltage into it.
St. Elmo’s Fire - A corona discharge that lights up the aircraft surface areas where maximum static discharge occurs.
Precision Approach - An instrument approach in which both course and glide slope information is provided.
Localizer - The portion of the ILS that gives left/right guidance information down the centerline of the instrument runway for final approach.
Glide Slope - The portion of the ILS approach which gives horizontal guidance down to the threshold of the instrument runway for final approach.
Outer Marker - VHF marker beacon used in the ILS. When the NDB compass locator is co-located with an OM , it is shown as LOM on instrument approach charts.
Middle Marker - VHF marker beacon used in the ILS. When the NDB compass locator is co-located with an MM, it is shown as LMM on instrument approach charts.
Instrument Landing System (ILS) - An electronic system that provides both horizontal and vertical guidance to a specific runway used to execute a precision instrument approach procedure. The course width is between 3 and 6 degrees.
SDF Approach - Approach that provides final approach course similar to the ILS localizer, but may or may not be aligned with the runway and the course may be wider than the standard ILS localizer, resulting in less precision. The course with of the SDF signal emitted from the transmitter is fixed at either 6 degrees or 12 degrees as necessary to provide maximum flyability and optimum approach course quality.
Localizer Type Direction Aid Approach (LDA) - The LDA approach is of comparable utility and accuracy to a localizer but is not a part of a complete ILS. The LDA course width is between 3 and 6 degrees and thus provides a more precise approach than an SDF approach.
Federal Airways - Class E airspace areas that extend upward from 1,200 ft. to, but not including, 18,000 ft. MSL, unless otherwise specified.
Victor Airways - The VOR airways are predicated solely on VOR and VORTAC navigation aids, they are depicted in blue on aeronautical charts.
Hi to Low, Look out Below: As temperature or pressure altitude decreases, the altimeter will read higher than the actual flight level you are at. EG: A change from 30.00” hg to 29.90” hg will result in a 100 ft. change in altitude. If your altimeter read 3000 ft. msl . at 30.00” hg you would actually be flying at 2900 ft. msl.
Standard Rate Turn - 3 degrees per second or 2 minutes for a full 360-degree turn.
Relative Bearing (RB) - The number of degrees measured clockwise between the heading of the aircraft and the direction from which the bearing is taken.
Magnetic Heading (MH) - The direction an aircraft is pointed with respect to magnetic north.
Magnetic Bearing (MB) - The direction to or from a radio transmitting station measured relative to magnetic north.
Homing - Flying an aircraft on any heading required to keep the needle pointing directly at the t0 degree relative bearing position toward a navigational facility.
Tracking - Flying a bearing that will maintain the desired track to or from a station regardless of crosswind conditions.
Wind Correction Angle (WCA) - Angle between the desired track and the heading necessary to keep an aircraft on the desired track.
Reverse Sensing - When the VOR needle indicates the reverse of normal operation. This occurs when the aircraft is headed toward the station with a FROM indication or when the aircraft is headed away from the station with a TO indication.
Types of Airspeed:
Indicated Airspeed - What is shown on the airspeed dial, uncorrected for installation or system errors.Calibrated Airspeed - Seed aircraft is moving through the air. IAS corrected for installation or position errors.
Equivalent Airspeed - Calibrated airspeed corrected for compression of the air inside the pito tube. EG: As airspeed and pressure altitude increase, the CAS becomes higher than it should be and a correction for compression must be subtracted from the CAS.
True Airspeed - CAS corrected for non-standard pressure and temperature.
The 5 Antidotes
| Hazardous Attitude | Antidote |
| Anti-Authority: Don’t tell me. | Follow the rules, they are usually right. |
| Impulsivity: Do something quickly. | Not so fast. Think first. |
| Invulnerability: It won’t happen to me. | It could happen to me. |
| Macho: I can do it. | Taking chances is foolish. |
| Resignation: What’s the use.I’m not helpless. | I can make a difference. |
Time and Distance to Station Computation:
| Time to Station = | Time in Seconds Number of Degrees Change |
= | Minutes to Station |
Distance off-course calculation:
| 200 x (deflection x distance out) |
| ------------------------------------------ | 6000 |
Permitted Aircraft Speeds per Altitude
| MHA - 6000 ft | 200 KIAS |
| 6001 - 14000 ft | 230 KIAS |
| 14001 and above | 265 KIAS |
Aircraft Approach Categories
| Category A | Speed less than 91 KIAS |
| Category B | Speed 91 KIAS - 121 KIASf |
| Category C | Speed 121 KIAS - 141 KIAS |
| Category D | Speed 141 KIAS - 166 KIAS |
| Category E | Speed 166 KIAS and above |
Memory Aids for IFR Approach Flying
| 3 A’s: Used to setup the aircraft prior to an approach: | |
| ATIS - Listen and record current information for inbound. | |
| Altimeter - Set to local setting either off ATIS or as ATC advised. | |
| Audio Panel - Set all communication and navigation frequencies and identify all of them. | |
| 6 M’s: Used to remember priority during flying instrument approaches. Follow the order to determine what to do/check first during the setup and flying of the approach. | |
| Magnetic Compass - Check Heading Indicator against the Magnetic Compass for accuracy. | |
| Marker Beacon - Turn on to listen. | |
| Mixture - Mixture full for approach. | |
| Minutes - How much time is needed for the approach before you execute a missed approach. | |
| Minimums - What is the minimum descent altitude allowed for the approach and the instruments you have to use in your aircraft. | |
| Missed - What are the published or ATC directed missed approach procedures for the approach you are flying. | |
| 5 T’s: Used to remember priority of action during a missed approach execution for IFR flight. | |
| Time - Is your time elapsed/or record your time. | |
| Turn - Turn to your next course. | |
| Throttle - Full Throttle for the descent. | |
| Twist - Turn to the new OBS Heading | |
| Talk - Talk to ATC and describe what you are doing last, only after the aircraft is under control and secured. | |
| 4 C’s: This is typically used to remember what the proper order for actions on a missed approach. | |
| Cram - Full Power (and manifold pressure if applicable and not already full). | |
| Climb - Climb as per ATC missed approach instructions or published. | |
| Clean - Flaps and Gear up, Carburetor Heat Cold (if applicable) | |
| Communicate - Talk to ATC as required or needed. | |