Introduction to PANS-OPS (DOC 8168)
Procedures for Air Navigation Services – Aircraft Operations
PANS-OPS stands for Procedures for Air Navigation Services – Aircraft Operations. It is ICAO Document 8168 and consists of two volumes:
- Volume I – Flight Procedures: Operational procedures recommended for flight operations personnel and flight crew. Outlines the parameters on which Volume II criteria are based.
- Volume II – Construction of Visual and Instrument Flight Procedures: For procedures specialists. Describes areas, obstacle clearance requirements, and guidelines for constructing instrument flight charts.
- All engines operating (unless contingency procedures are being developed — that is the operator's responsibility).
- All procedures depict tracks. Pilots apply corrections to heading for known wind.
- Calculations are based on an altitude of 600 m (2,000 ft) above MSL and ISA +15°C unless otherwise stated.
General Criteria for Departure Procedures
Where track guidance is provided, each segment comprises a specified volume of airspace. The vertical cross-section is an area located symmetrically about the centre line of each segment.
- Vertical cross-section = divided into Primary and Secondary areas.
- Full obstacle clearances are applied over the primary area.
- Clearance reduces to zero at the outer edges of the secondary areas.
- On straight segments: Primary area width = ½ of total width. Each secondary area = ¼ of total width.
- Where no track guidance is provided during a turn: the entire total width is considered primary area.
- MOC is provided at full value across the primary area. In secondary areas, MOC reduces from inner edge to zero at outer edge.
Obstacle Clearance (MOC) in Departure
At the Departure End of Runway (DER):
MOC = ZERO
Increases by:
0.8% of the horizontal distance from DER (assuming max turn of 15°).
In the Turn Initiation Area and Turn Area:
MOC = 90 m (295 ft)
Mountainous/precipitous terrain:
Procedures designer may increase MOC.
Instrument Departure Procedure — Design
- Design of an IDP is dictated by the terrain surrounding the aerodrome.
- May also be required for ATC requirements in the case of SID routes.
- These factors influence the type and siting of navaids and the departure route.
- Airspace restrictions may also affect routing and siting of navaids.
Where obstacles cannot be cleared by the appropriate margin when flown on instruments, aerodrome operating minima are established to permit visual flight clear of obstacles.
Wherever possible, a straight departure aligned with the runway centre line is specified.
When a departure route requires a turn of more than 15° to avoid an obstacle, a turning departure is constructed.
A departure procedure is established for each runway where instrument departures are expected. It will include procedures for the various categories of aircraft.
- When radar vectored: Pilots will NOT compensate for wind effects.
- When flying departure routes expressed as tracks to be made good: Pilots WILL compensate for known or estimated wind.
Procedure Design Gradient (PDG)
The PDG is an aid to the procedures designer, who adjusts the route to minimise the PDG consistent with other constraints.
Unless otherwise published:
PDG = 3.3 per cent
For helicopters (Cat H):
PDG = 5.0 per cent
Basis of PDG:
OIS gradient = 2.5%
+ Additional margin = 0.8%
= PDG = 3.3%
- Published gradients are specified to an altitude/height after which the minimum gradient of 3.3% is considered to prevail.
- The final PDG continues until obstacle clearance is ensured for the next phase (en-route, holding, or approach).
- At that point, the departure procedure ends and is marked by a significant point.
Gradients to a height of 60 m (200 ft) or less, caused by close-in obstacles, are NOT specified. However, a note will be published stating that close-in obstacles exist.
Where a suitably located DME exists, additional specific height/distance information for obstacle avoidance may be published. RNAV waypoints or other suitable fixes may be used to provide a means of monitoring climb performance.
Radar Vectors during Departure
Pilots should NOT accept radar vectors during departure UNLESS one of the following applies:
- They are above the minimum altitudes/heights required to maintain obstacle clearance in the event of engine failure. (This relates to engine failure between V1 and minimum sector altitude, or end of contingency procedure.)
- The departure route is non-critical with respect to obstacle clearance.
Standard Instrument Departures (SIDs)
The SID terminates at the first fix/facility/waypoint of the en-route phase following the departure procedure.
A straight departure is one in which the initial departure track is within 15° of the alignment of the runway centre line.
- If obstacles exist that affect the departure route, PDGs greater than 3.3% may be specified.
- When such a gradient is specified, the altitude/height to which it extends shall be promulgated. After this point, PDG of 3.3% (Cat H: 5.0%) resumes.
- Gradients to a height of 60 m (200 ft) or less due to close-in obstacles are not specified; a note will be published instead.
- Turn of more than 15° from runway C/L = Turning Departure.
- Straight flight is assumed until reaching an altitude/height of at least 120 m (394 ft) for fixed-wing aircraft.
- For helicopters: 90 m (295 ft).
Omnidirectional Departures
Where no track guidance is provided, departure procedures are designed using the omnidirectional method.
Where obstacles do not permit omnidirectional procedures, one of the following is necessary:
- Fly a Standard Instrument Departure (SID) route; or
- Ensure ceiling and visibility permit obstacles to be avoided by visual means.
- Departure procedure begins at the Departure End of Runway (DER) = end of area declared suitable for take-off.
- Since point of lift-off varies, a turn at 120 m (394 ft) above aerodrome elevation is not initiated sooner than 600 m from the beginning of the runway.
- Procedures are normally designed/optimised for turns at 600 m from the beginning of the runway.
- Turns may NOT be initiated before the DER (or specified point); this will be noted on the departure chart.
- For Category H: procedure turns can be initiated at 90 m (295 ft) if the DER and earliest initiation point are at the beginning of the runway/FATO.
- Default PDG = 3.3% (helicopters: 5%) + straight climb on extended runway C/L until 120 m (394 ft) above aerodrome elevation (helicopters: 90 m).
- The basic procedure ensures:
(a) Aircraft climbs on extended C/L to 120 m (394 ft) before turns can be specified.
(b) At least 90 m (295 ft) of obstacle clearance is provided before turns greater than 15° are specified.
No obstacles penetrate the 2.5% OIS and 90 m (295 ft) clearance prevails. A 3.3% climb to 120 m satisfies requirements for a turn in any direction.
Where obstacles preclude omnidirectional turns at 120 m, the procedure specifies a 3.3% climb to a higher alt/height where omnidirectional turns can be made.
Where obstacles exist, the procedure defines a minimum gradient more than 3.3% to a specified altitude/height before turns are permitted.
The procedure identifies sectors for which either a minimum gradient or minimum turn alt/height is specified. E.g., "climb straight ahead to alt X before turning east; climb to alt Y before turning west."
RNAV Systems — GNSS, SBAS, GBAS, PBN
Global Navigation Satellite System. A worldwide position and time determination system including one or more satellite constellations, aircraft receivers, and system integrity monitoring, augmented as necessary.
Ground Based Augmented System. User receives augmentation information directly from a ground-based transmitter.
Satellite Based Augmentation System. User receives augmentation information from a satellite-based transmitter. (WAAS, EGNOS, GAGAN, MSAS)
Aircraft Based Augmentation System. Augments and/or integrates GNSS information with information available on board the aircraft.
GBAS Landing System. For approach and landing using GNSS augmented by GBAS as the primary navigational reference.
Performance Based Navigation. Area navigation based on performance requirements for aircraft operating along an ATS route, instrument departure/approach procedure, or in designated airspace.
- Turn at a fly-by waypoint — Turn anticipation always provided.
- Turn at a flyover waypoint — No turn anticipation.
- Turn at an altitude/height — Some systems cannot code this; must be executed manually.
- Fixed radius turn — Generally associated with RNP procedures.
- From DER to turn initiation point: SBAS receiver provides nominal full-scale deflection (FSD) of 0.3 NM.
- Larger FSDs may be acceptable with augmentations (e.g., autopilot).
- SBAS receiver will NOT transition to en-route integrity performance until the final waypoint in the departure procedure is sequenced.
No departure criteria specifically designed for GBAS exists. Departure operations based on basic GNSS or SBAS may be flown by aircraft with a GBAS receiver using the optional GBAS positioning service.
General Criteria for Arrival & Approach Procedures
Because all navigation facilities and waypoints have accuracy limitations, the geographic point identified is not precise but may be anywhere within an area called the fix tolerance area which surrounds its plotted point of intersection.
| Navigation System | Fix Tolerance | Notes |
|---|---|---|
| TAR (Terminal Area Radar) | ±1.5 km (0.8 NM) | Within 37 km (20 NM) |
| RSR (En-route Surveillance Radar) | ±3.1 km (1.7 NM) | Within 74 km (40 NM) |
| DME | ±0.46 km (0.25 NM) + 1.25% of distance | To the antenna |
| 75 MHz Marker Beacon | Used for ILS & "z" markers | Instrument approach |
Wherever possible, a straight-in approach aligned with the runway centre line is specified.
For non-precision approaches, a straight-in approach is acceptable if the angle between the final approach track and runway C/L is 30° or less.
Specified when terrain or other constraints cause the final approach track alignment or descent gradient to fall outside the criteria for a straight-in approach.
The final approach track is in most cases aligned to pass over some portion of the usable landing surface.
Categories of Aeroplanes & Speed Table
Five categories based on the indicated airspeed at threshold (Vat) which equals the stall speed VSO × 1.3 or stall speed VS1g × 1.23 (whichever is higher) in landing configuration at maximum certificated landing mass.
| Cat | Vat (kt) | Initial Approach (kt) | Final Approach (kt) | Circling Max (kt) | Missed App Intermediate (kt) | Missed App Final (kt) |
|---|---|---|---|---|---|---|
| A | <91 | 90 / 150 (110*) | 70 / 100 | 100 | 100 | 110 |
| B | 91–120 | 120 / 180 (140*) | 85 / 130 | 135 | 130 | 150 |
| C | 121–140 | 160 / 240 | 115 / 160 | 180 | 160 | 240 |
| D | 141–165 | 185 / 250 | 130 / 185 | 205 | 185 | 265 |
| E | 166–210 | 185 / 250 | 155 / 230 | 240 | 230 | 275 |
| H | N/A | 70 / 120** | 60 / 90*** | N/A | 90 | 90 |
* Maximum speed for reversal and racetrack procedures. ** Max speed for racetrack: ≤6000 ft = 100 kt; >6000 ft = 110 kt. *** GNSS point-in-space: 120 KIAS initial/intermediate, 90 KIAS final/MA (or 90/70 KIAS based on operational need).
Minimum/Optimum (with FAF):
5.2% / 3.0° (52 m/km = 318 ft/NM)
Maximum for Cat A & B:
6.5% / 3.7° (65 m/km = 395 ft/NM)
Maximum for Cat C, D, E:
6.1% / 3.5° (61 m/km = 370 ft/NM)
Maximum for Cat H:
10% / 5.7°
- Requires a continuous descent without level-offs, flown with VNAV guidance or manual calculation.
- Rate of descent adjusted to achieve continuous descent to a point approximately 15 m (50 ft) above the landing runway threshold.
- Descent shall pass at or above the minimum altitude at any stepdown fix.
- CDFA with advisory VNAV = 3D instrument approach operation.
- CDFA with manual calculation = 2D instrument approach operation.
Approach Segments — IAF to MAPt
Permits transition from the en-route phase to the approach phase. Arrival route normally ends at the IAF.
Protection area convergence: Begins at 46 km (25 NM) before the IAF, with a maximum convergence angle of 30° each side of the axis.
- MSA (Minimum Sector Altitude) provides at least 300 m (1,000 ft) obstacle clearance within 46 km (25 NM) of the navigation aid, IAF, or IF.
- TAA (Terminal Arrival Altitude): Associated with PBN procedures based on the "T" or "Y" arrangement with three IAFs around the IF. TAAs replace the 46 km (25 NM) MSA where published.
- Begins at the IAF and ends at the IF.
- Aircraft has left the en-route structure and is manoeuvring to enter the intermediate segment.
- Speed and configuration depend on distance from aerodrome and descent required.
- Max angle of interception of initial segment to IF: 90° for Precision 120° for Non-Precision
- MOC: 300 m (1,000 ft) in primary area, reducing to zero at outer edge of secondary area.
Used where no suitable IAF or IF is available. Entry is restricted to a specific direction or sector — a base turn or procedure turn is prescribed. Directions and timing specified must be strictly followed. A racetrack or holding manoeuvre cannot be conducted unless so specified.
Three manoeuvre types:
- 45°/225° Procedure Turn (1 to 3 minutes outbound timing)
- 80°/260° Procedure Turn (1 to 3 minutes outbound timing)
- Base Turn (1, 2, or 3 minutes — end of outbound leg by radial or DME distance)
- 180° turn overhead facility/fix onto outbound track for 1, 2, or 3 minutes.
- Followed by a 180° turn in the same direction to return to inbound track.
- Outbound leg may alternatively be limited by a DME distance or intersecting radial/bearing.
- Aircraft speed and configuration adjusted to prepare for final approach. Descent gradient kept as shallow as possible.
- MOC: Reduces from 300 m (984 ft) to 150 m (492 ft) in the primary area, reducing to zero at outer edge of secondary area.
- Begins: On inbound track of procedure turn / base turn / final inbound leg of racetrack.
- Ends: At the FAF or Final Approach Point (FAP).
- Note: Where no FAF is specified, the inbound track IS the final approach segment.
- NPA with FAF — Non-precision approach with final approach fix
- NPA without FAF — Non-precision approach; facility is both IAF and MAPt
- APV — Approach with vertical guidance
- PA — Precision approach
- Begins at FAF, ends at MAPt.
- FAF is sited on the final approach track.
- Optimum distance FAF to threshold: 9.3 km (5.0 NM)
- Maximum length: normally not greater than 19 km (10 NM)
- MOC: 75 m with FAF
- Stepdown fixes may be incorporated. Two OCA/H values published (higher for primary, lower if stepdown fix is positively identified).
- Single facility on or near aerodrome = both IAF and MAPt.
- Indicates: (a) minimum alt/height for reversal/racetrack; and (b) OCA/H for final approach.
- In absence of FAF, descent to MDA/H starts once established inbound on final approach track.
- MOC: 90 m without FAF
- Final approach track cannot normally be aligned on runway C/L.
- FAP = point in space on final approach track where intermediate approach altitude/height intercepts the nominal glide path / MLS elevation angle.
- Intermediate altitude generally intercepts glidepath at heights of 300 m (1,000 ft) to 900 m (3,000 ft) above runway elevation.
- For a 3° glide path, interception occurs between 6 km (3 NM) and 19 km (10 NM) from the threshold.
- Outer Marker/DME fix: Permits verification of glidepath/altimeter relationship. Descent below fix crossing altitude should NOT be made prior to crossing the fix.
- Note: FAF is associated with NPA; FAP is associated with PA.
- OCA (Obstacle Clearance Altitude) — Referenced to MSL.
- OCH (Obstacle Clearance Height) — Referenced to threshold elevation (or aerodrome elevation if threshold >2 m/7 ft below aerodrome elevation).
- MDA (Minimum Descent Altitude) — NPA/circling: altitude below which descent must NOT be made without required visual reference. Referenced to MSL.
- MDH (Minimum Descent Height) — Referenced to aerodrome elevation or threshold elevation.
- DA (Decision Altitude) — PA/APV: altitude at which a missed approach must be initiated if required visual reference not established. Referenced to MSL.
- DH (Decision Height) — Referenced to threshold elevation.
Constructed per ICAO Doc 8168/PANS-OPS Volume II. Identifies obstacles that may affect execution of an IAP (except circling). Refers to the final approach leg between MDA/DA of the procedure and the runway threshold.
Missed Approach Segment
- Only one missed approach procedure per instrument approach procedure.
- Three phases: Initial, Intermediate, and Final.
- Specifies a point where MA begins and a point or alt/height where it ends.
- MA should be initiated not lower than DA/H in precision approaches, or at the MAPt not lower than MDA/H in non-precision.
MAPt = point of intersection of the electronic glide path with the applicable DA/H.
MAPt = a navigation facility, a fix, or a specified distance from the FAF. Upon reaching the MAPt if required visual reference is not established, missed approach must be initiated at once.
Normally based on a minimum missed approach climb gradient of 2.5 per cent.
| Phase | Begins At | Ends At | Key Characteristics |
|---|---|---|---|
| Initial | MAPt | SOC (Start of Climb) | Concentrated attention on establishing climb. Guidance equipment not extensively utilised. No turns specified in this phase. |
| Intermediate | SOC | First point where 50 m (164 ft) obstacle clearance is obtained | Climb continued straight ahead. Track may be changed by max 15°. Aircraft begins track corrections. |
| Final | 50 m (164 ft) clearance point [Cat H: 40 m (131 ft)] | Point where new approach/holding/en-route flight is initiated | Turns may be prescribed in this phase. Airspace for turns based on final missed approach speeds. |
Turns in a missed approach procedure are only prescribed where terrain or other factors make a turn necessary. The protected airspace for turns is based on speeds for the final missed approach.
ICAO Classification of Approaches (NPA / APV / PA)
Type A: Minimum descent height or decision height at or above 75 m (250 ft).
Includes: NPA, APV, PA Cat I with DH ≥75 m.
Type B: Decision height below 75 m (250 ft). Categorised as Precision Approach Runway:
- CAT I: DH ≥ 60 m (200 ft); RVR ≥ 800 m or visibility ≥ 550 m
- CAT II: DH 30–60 m (100–200 ft); RVR ≥ 300 m
- CAT III: DH < 30 m (100 ft) OR no DH; RVR < 300 m OR no RVR limitation
⚠️ CAT II and CAT III operations shall NOT be authorized unless RVR information is provided.
| Type of Approach | Annex 10 System Performance | Annex 6 Approach Operation Category |
|---|---|---|
| Non-Precision (NPA) | — | 2D – Type A |
| APV (Vertical Guidance) | — | 3D – Type A |
| Precision Approach (PA) | CAT I, DH ≥ 75 m (250 ft) | 3D – Type A |
| CAT I, DH ≥ 60 m (200 ft) and < 75 m (250 ft) | 3D – Type B — CAT I | |
| Category II | 3D – Type B — CAT II | |
| Category III | 3D – Type B — CAT III |
- NPA Conventional: Ground-based (VOR/DME, NDB, Localiser). Runway visibility ≥ 1,000 m.
- NPA PBN (RNP APCH): Uses GNSS. Charted as RNAV(GNSS) or RNAV(GPS). Types: RNP App, NPA GPS, LNAV.
- APV (RNP AR APCH): 3D guidance but lower performance than PA. Types: APV BaroVNAV, APV SBAS (LPV), LNAV/VNAV.
- PA Conventional: ILS, MLS, PAR. 3D approach ops Type A or B.
- PA PBN: SBAS Cat I, GLS (GBAS Landing System).
Visual Manoeuvring (Circling)
Visual manoeuvring (circling) is the phase of flight after an instrument approach has been completed, which brings the aircraft into position for landing on a runway that is not suitably located for straight-in approach (i.e., alignment or descent gradient criteria cannot be met).
Arcs centred on each runway threshold, joined by tangent lines. Radius depends on:
- Aircraft category
- Speed for each category
- Wind speed: 46 km/h (25 kt) throughout the turn
- Bank angle: 20° average or 3° per second, whichever requires less bank
Descent below MDA/H should NOT be made until ALL three of the following are met:
- Visual reference has been established and can be maintained.
- The pilot has the landing threshold in sight.
- The required obstacle clearance can be maintained and the aircraft is in a position to carry out a landing.
If visual reference is lost while circling, the specified missed approach procedure must be followed. The pilot will make an initial climbing turn toward the landing runway and overhead the aerodrome, then establish on the missed approach track.
Holding Procedures
All turns to be made at a bank angle of 25° or at a rate of 3° per second, whichever requires the lesser bank.
Pilots should attempt to maintain the track by applying allowance for known wind — both heading and timing corrections. This applies during entry and while flying in the holding pattern.
Timing begins over or abeam the fix, whichever occurs later. If abeam position cannot be determined, start timing when the turn to outbound is completed.
If outbound leg is based on a DME distance, it terminates as soon as the limiting DME distance is reached.
| Sector | Entry Type | Procedure |
|---|---|---|
| Sector 1 | Parallel Entry | At the fix, turn LEFT onto outbound heading for the appropriate period of time; then turn LEFT to intercept inbound track or return to fix; on second arrival, turn RIGHT to follow holding pattern. |
| Sector 2 | Offset Entry (30°) | At the fix, turn to make good a track at 30° from the reciprocal of the inbound track on the holding side; fly outbound for the appropriate time; turn RIGHT to intercept inbound track; on second arrival over fix, turn RIGHT to follow holding pattern. |
| Sector 3 | Direct Entry | Having reached the fix, turn RIGHT to follow the holding pattern. |
- The entry track to a VOR/DME fix is limited to: (a) the VOR radial; (b) the DME arc; or (c) the entry radial to a VOR/DME fix at the end of the outbound leg as published.
- Note: DME arc entry is specified only when there is a specific operational difficulty making other entry procedures impossible.
| Level / Altitude | Normal Conditions | Turbulence Conditions |
|---|---|---|
| Up to 4,250 m (14,000 ft) | 425 km/h (230 kt) — Cats C,D,E 315 km/h (170 kt) — Cats A,B |
520 km/h (280 kt) [or 0.8 Mach] 315 km/h (170 kt) — Cats A,B |
| 4,250 m (14,000 ft) to 6,100 m (20,000 ft) inclusive | 445 km/h (240 kt) | 520 km/h (280 kt) or 0.8 Mach — lesser |
| 6,100 m (20,000 ft) to 10,350 m (34,000 ft) inclusive | 490 km/h (265 kt) | 520 km/h (280 kt) or 0.8 Mach — lesser |
| Above 10,350 m (34,000 ft) | 0.83 Mach | 0.83 Mach |
Notes: Speed of 520 km/h (280 kt) for turbulence requires prior ATC clearance, unless publications indicate the holding area can accommodate it. 315 km/h (170 kt) applies to Cat A and B only.
- At or below 4,250 m (14,000 ft): still air time for outbound entry heading must not exceed 1 minute.
- Above 4,250 m (14,000 ft): must not exceed 1.5 minutes.
- Provides clearance of at least 300 m (984 ft) above obstacles in the holding area.
- Minimum holding altitude published shall be rounded up to the nearest 50 m or 100 ft.
- Over high terrain/mountainous areas: additional clearance up to 600 m (1,969 ft) is provided to accommodate turbulence, down-drafts, and altimeter errors.
Simultaneous ILS Operations on Parallel / Near-Parallel Runways
| Mode | Name | Description | Runway Separation |
|---|---|---|---|
| Mode 1 | Independent Parallel Approaches | Radar separation minima between aircraft using adjacent ILS/MLS are not prescribed. | ≥ 1,035 m between C/Ls |
| Mode 2 | Dependent Parallel Approaches | Radar separation minima between aircraft using adjacent ILS/MLS are prescribed. | ≥ 915 m between C/Ls |
| Mode 3 | Independent Parallel Departures | Aircraft departing in same direction from parallel runways simultaneously. (Less than specified C/L distance for wake turbulence = single runway.) | ≥ 760 m between C/Ls |
| Mode 4 | Segregated Parallel Ops | One runway for approaches, one for departures. Approach runway staggered ≥ 2 NM straight and level minimum. Descent point. | ≥ 760 m (reduce by 150m/30% = 300 m min) |
RNAV Arrival & Approach — Based on VOR/DME
Based on one reference facility composed of a VOR and collocated DME. The reference facility will be indicated. The VOR/DME RNAV approach is a non-precision approach procedure.
| Segment | FTT Value | Key Rules |
|---|---|---|
| STARs (Arrival) | 3.7 km (2.0 NM) until 46 km (25 NM) from IAF; 1.9 km (1.0 NM) after | Based on RNP 1 or better; or specific RNAV criteria |
| Final Approach | MOC = 75 m (246 ft) in primary area | Generally aligned with runway. FAF = fly-by waypoint. Flyover waypoint also provided at runway threshold. |
| Missed Approach | Area splays at 15° each side from earliest MAPt | MAHF (Missed Approach Holding Fix) defines end of missed approach segment. |
Altimeter Setting Procedures
Provide adequate vertical separation between aircraft and adequate terrain clearance during all phases of flight. Method is based on the following basic principles:
- At or below transition altitude: vertical position expressed as ALTITUDE (altimeter set to QNH).
- Above transition altitude: vertical position expressed as FLIGHT LEVELS (altimeter set to 1,013.2 hPa).
- Change from altitude → flight level: at transition altitude (on climb).
- Change from flight level → altitude: at transition level (on descent).
- Transition layer = airspace between transition level and transition altitude.
- Normally specified for each aerodrome by the State.
- Minimum transition altitude in India = 4,000 ft
- Height above aerodrome: as low as possible but normally not less than 900 m (3,000 ft).
- Calculated height rounded up to the next full 300 m (1,000 ft).
- Transition level located 300 m (1,000 ft) above the transition altitude (to permit concurrent use in cruising flight with vertical separation ensured).
- Flight Level Zero = 1,013.2 hPa. Consecutive FLs separated by a pressure interval corresponding to at least 500 ft (152.4 m) in the standard atmosphere.
- With aircraft at a known elevation on the aerodrome, set the altimeter to the current QNH/QFE setting.
- Vibrate the instrument by tapping unless mechanical vibration is provided.
A serviceable altimeter indicates the elevation/height within a tolerance of:
- Test range 0 to 9,000 m (0 to 30,000 ft): ±20 m or 60 ft
- Test range 0 to 15,000 m (0 to 50,000 ft): ±25 m or 80 ft
Secondary Surveillance Radar (SSR) & Transponder
Secondary Surveillance Radar. Uses transmitters/receivers (interrogators) and transponders.
Aircraft system based on SSR transponder signals operating independently of ground-based equipment to provide advice to the pilot on potential conflicting aircraft equipped with SSR transponders.
To elicit transponder replies for identity and surveillance.
To elicit transponder replies for automatic pressure-altitude transmission and surveillance.
When an aircraft carries a serviceable transponder, the pilot shall operate it at all times during flight, regardless of whether SSR is used for ATS purposes in that airspace.
Squawk codes are four-digit octal numbers. Dials read 0–7 inclusive. Lowest squawk = 0000. Highest = 7777.
- Operate on Mode A codes as directed by the ATC unit with which contact is being made.
- Operate on Mode A codes as prescribed by regional air navigation agreements.
- In absence of any ATC directions or regional agreements: operate on Mode A Code 2000.
When ATC requests "CONFIRM SQUAWK (code)", the pilot shall:
- Verify the Mode A code setting on the transponder.
- Reselect the assigned code if necessary.
- Confirm to ATC the setting displayed on the transponder controls.
⚠️ Pilots shall NOT SQUAWK IDENT unless requested by ATC.
- 7700 (Emergency): Set unless ATC has previously directed to operate on a specified code. However, pilot may select 7700 whenever there is specific reason to believe it is the best course of action.
- 7600 (Comm Failure): Set when losing two-way communications. Controller will determine extent of failure by instructing pilot to SQUAWK IDENT or change code.
- 7500 (Unlawful Interference): If circumstances warrant, Code 7700 should be used instead. If ATC requests pilot to confirm 7500, pilot shall — according to circumstances — either confirm or not reply at all. Non-reply = confirmation that 7500 is not an inadvertent selection.
ATC units shall attempt to provide for continuation of the flight to the destination aerodrome in accordance with the flight plan. Pilots may, however, expect to comply with specific restrictions.
ACAS — Airborne Collision Avoidance System
ACAS indications shall be used by pilots in the avoidance of potential collisions, enhancement of situational awareness, and the active search for, and visual acquisition of, conflicting traffic. Nothing in ACAS procedures prevents pilots-in-command from exercising their best judgment and full authority in the choice of the best course of action.
- Nominal surveillance range: 26 km (14 NM)
- Minimum guaranteed range when airborne: 8.5 km (4.5 NM)
- Range can be reduced in geographic areas with large numbers of ground interrogators and/or ACAS-equipped aircraft.
- Intended to alert pilots to the possibility of an RA, to enhance situational awareness, and to assist in visual acquisition of conflicting traffic.
- Pilots shall NOT manoeuvre in response to TAs only.
- On receipt of a TA, use all available information to prepare for appropriate action if an RA occurs.
- TAs can be issued against any Mode C transponder-equipped aircraft.
- Respond IMMEDIATELY by following the RA as indicated, unless doing so would jeopardize safety.
- Follow the RA even if there is a conflict between RA and ATC instruction to manoeuvre.
- Do NOT manoeuvre in the opposite sense to the RA.
- As soon as possible, notify the appropriate ATC unit of the RA, including the direction of any deviation.
- Promptly comply with any modified RAs.
- Limit alterations to the minimum extent necessary.
- Promptly return to ATC clearance when conflict is resolved.
- Notify ATC when returning to the current clearance.
- TAs can be issued against any transponder-equipped aircraft responding to Mode C interrogations, even without altitude-reporting capability.
- RAs can be issued only against aircraft that are reporting altitude and in the vertical plane only.
- RAs against ACAS-equipped intruders are coordinated to ensure complementary RAs are issued.
- Failure to respond to an RA deprives the aircraft of collision protection AND restricts the other aircraft's ACAS choices.
- Manoeuvring in the opposite direction to an RA is likely to result in further reduction in separation.
The following alerts take precedence over ACAS:
- Stall Warning
- Wind Shear Warning
- Ground Proximity Warning System (GPWS) alerts
DGCA Question Bank & Answer Key
Selected questions from the RK-Bali reference text — 102 questions total
| Q | Ans | Q | Ans | Q | Ans | Q | Ans | Q | Ans | Q | Ans | Q | Ans |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1 | A | 2 | A | 3 | C | 4 | B | 5 | C | 6 | B | 7 | A |
| 8 | C | 9 | B | 10 | A | 11 | C | 12 | B | 13 | C | 14 | C |
| 15 | C | 16 | A | 17 | C | 18 | A | 19 | B | 20 | C | 21 | B |
| 22 | A | 23 | A | 24 | B | 25 | A | 26 | C | 27 | A | 28 | B |
| 29 | C | 30 | A | 31 | C | 32 | A | 33 | B | 34 | C | 35 | C |
| 36 | B | 37 | B | 38 | A | 39 | C | 40 | C | 41 | A | 42 | C |
| 43 | B | 44 | A | 45 | B | 46 | A | 47 | A | 48 | A | 49 | B |
| 50 | C | 51 | C | 52 | B | 53 | C | 54 | C | 55 | C | 56 | A |
| 57 | C | 58 | A | 59 | A | 60 | A | 61 | B | 62 | B | 63 | C |
| 64 | A | 65 | A | 66 | A | 67 | C | 68 | C | 69 | A | 70 | B |
| 71 | A | 72 | A | 73 | C | 74 | A | 75 | B | 76 | C | 77 | B |
| 78 | B | 79 | A | 80 | B | 81 | A | 82 | C | 83 | B | 84 | A |
| 85 | C | 86 | B | 87 | C | 88 | C | 89 | C | 90 | B | 91 | C |
| 92 | A | 93 | C | 94 | A | 95 | B | 96 | B | 97 | A | 98 | A |
| 99 | C | 100 | C | 101 | A | 102 | B | — | — | — | — | — | — |
Critical Numbers — Must Memorise
All the key figures from PANS-OPS Chapter 13 in one place
| Topic | Value | Unit | Context |
|---|---|---|---|
| Standard PDG (fixed-wing) | 3.3% | gradient | Unless otherwise published |
| Standard PDG (helicopters) | 5.0% | gradient | Cat H procedures |
| OIS gradient (basis of PDG) | 2.5% | gradient | Obstacle Identification Surface |
| MOC increase rate from DER | 0.8% | of horizontal dist | Departure, max turn 15° |
| MOC in turn initiation area | 90 m (295 ft) | m / ft | Departure turns |
| Straight departure track alignment | ±15° | degrees | From runway C/L |
| Min altitude before turn (fixed-wing) | 120 m (394 ft) | m / ft | Above aerodrome elevation |
| Min altitude before turn (Cat H) | 90 m (295 ft) | m / ft | Helicopter turns |
| Turn initiation distance from runway start | 600 m | m | Normal design optimisation |
| Close-in obstacle gradient not published | ≤60 m (200 ft) | m / ft | A note published instead |
| MSA / TAA obstacle clearance | 300 m (1,000 ft) | m / ft | Within 46 km (25 NM) |
| Initial approach MOC | 300 m (1,000 ft) | m / ft | Primary area |
| Intermediate approach MOC (start) | 300 m (984 ft) | m / ft | Reduces to 150 m |
| Intermediate approach MOC (end) | 150 m (492 ft) | m / ft | Primary area |
| NPA MOC with FAF | 75 m | m | Final approach |
| NPA MOC without FAF | 90 m | m | Final approach |
| FAF optimal distance from threshold | 9.3 km (5.0 NM) | km / NM | NPA with FAF |
| FAF maximum length from threshold | 19 km (10 NM) | km / NM | NPA with FAF |
| FA interception angle (precision) | 90° | degrees | Max angle at IF |
| FA interception angle (non-precision) | 120° | degrees | Max angle at IF |
| Straight-in approach alignment | ≤30° | degrees | NPA acceptable angle to C/L |
| Missed approach gradient (standard) | 2.5% | gradient | Minimum climb |
| MA intermediate phase turn | Max 15° | degrees | From initial MA track |
| MA final phase MOC (fixed-wing) | 50 m (164 ft) | m / ft | Start of final MA phase |
| MA final phase MOC (Cat H) | 40 m (131 ft) | m / ft | Cat H final MA |
| CAT I DH minimum | 60 m (200 ft) | m / ft | Precision approach |
| CAT I RVR minimum | 800 m | m | Or visibility 550 m |
| CAT II DH range | 30–60 m (100–200 ft) | m / ft | RVR ≥ 300 m |
| CAT III DH | <30 m (100 ft) | m / ft | Or no DH; RVR < 300 m |
| Type A minimum DH/MDH | ≥75 m (250 ft) | m / ft | 2D/3D Type A operations |
| Holding turn bank / rate | 25° or 3°/sec | °/°/sec | Whichever requires lesser bank |
| Holding entry zone of flexibility | ±5° | degrees | Either side of sector boundaries |
| Holding speed ≤ 14,000 ft (Cat C,D,E) | 230 kt | kt | Normal; 280 kt turbulence |
| Holding speed ≤ 14,000 ft (Cat A,B) | 170 kt | kt | Normal and turbulence |
| Holding outbound time ≤ 14,000 ft | 1 minute | min | Outbound leg timing |
| Holding outbound time > 14,000 ft | 1.5 minutes | min | Above 4,250 m |
| Min holding clearance (normal) | 300 m (984 ft) | m / ft | Above obstacles |
| Min holding clearance (mountainous) | 600 m (1,969 ft) | m / ft | High terrain areas |
| India minimum transition altitude | 4,000 ft | ft | INDIA specific |
| Altimeter test tolerance (0–30,000 ft) | ±20 m / 60 ft | m / ft | Pre-flight test |
| Altimeter test tolerance (0–50,000 ft) | ±25 m / 80 ft | m / ft | Pre-flight test |
| ACAS nominal surveillance range | 26 km (14 NM) | km / NM | Nominal |
| ACAS minimum guaranteed range | 8.5 km (4.5 NM) | km / NM | When airborne |
| Circling wind speed assumption | 46 km/h (25 kt) | kt | Throughout the turn |
| Circling bank angle assumption | 20° or 3°/sec | ° / °/sec | Whichever requires less bank |
| SBAS straight departure FSD | 0.3 NM | NM | From DER to turn initiation |
| Mode 1 parallel runway C/L separation | ≥1,035 m | m | Independent parallel approaches |
| Mode 2 parallel runway C/L separation | ≥915 m | m | Dependent parallel approaches |