Instrument Departures

Terrain usually dictates the design. Airspace restrictions, neighbouring aerodromes, ATS routes and ATC requirements can alter the route and navigation-aid locations.

Core assumptions

Design considerations

Where possible, a straight departure is aligned with the runway. A required turn of more than 15 degrees creates a turning departure. Where no track guidance exists, the omnidirectional method is used.

Aerodrome operating minima

If the required margin cannot be obtained while the aeroplane is flown on instruments, operating minima may require visual obstacle avoidance. This does not permit visual avoidance unless ceiling and visibility actually support it.

Establishment and wind effect

A procedure is established for each runway where instrument departures are expected and covers the aircraft categories using it. On a published track the pilot corrects for wind. On a radar heading the pilot flies the heading given.

The standard 3.3 percent PDG combines a 2.5 percent obstacle identification surface with an increasing 0.8 percent obstacle-clearance margin.

Beginning at the DER

The departure begins at the departure end of runway, or DER, which is the end of the area declared suitable for take-off, including a clearway where applicable. The PANS-OPS path crosses the DER at least 5 m, 16 ft, above its elevation.

Basis of the PDG

In the turn-initiation and turn area, at least 90 m, 295 ft, of obstacle clearance is provided. Mountainous or precipitous terrain may require more. If an obstacle requires a gradient above 3.3 percent, the chart gives that gradient and the altitude or height where 3.3 percent resumes.

Fixes for obstacle avoidance

DME, an RNAV waypoint or another suitable fix may pair position with a minimum height so the crew can monitor climb performance before passing a critical obstacle.

A straight departure has an initial track within 15 degrees of runway centre-line alignment. Later course changes do not alter that initial classification.

Alignment and guidance

The protected area expands from the DER about the departure track. Guidance may come from VOR, NDB or RNAV and is expected to be acquired within 20 km, 10.8 NM, of the DER. Bali's conventional construction shows approximately 3.7 km, 2.0 NM, tolerance for VOR and 4.6 km, 2.5 NM, for NDB.

The crew converts a published percentage into the required climb rate for actual groundspeed and confirms that the aircraft can achieve it. The stated gradient applies to the published altitude or height, after which the charted or standard value continues.

A turning departure protects the straight climb to the turn point and a larger, speed-dependent curved area beyond it.

Turn initiation

An aeroplane is assumed to fly straight until at least 120 m, 394 ft, above DER elevation. For helicopters the value is 90 m, 295 ft. A fix, facility, altitude or height may define the turning point, and the turn area receives at least 90 m, 295 ft, MOC.

Speed and containment

Turn radius grows with true airspeed, wind and the design bank angle. A published maximum speed protects containment. If the aircraft cannot comply, the crew requests another procedure.

Guidance after the turn

Track guidance for a conventional turning departure is expected within 10 km, 5.4 NM, after completion of the turn.

Radar vectors

A pilot should not accept a departure vector unless above the altitude or height needed for obstacle clearance after engine failure, or the route is non-critical for obstacle clearance. Vectoring does not replace the operator's engine-out analysis.

Without track guidance, the omnidirectional method protects any permitted direction after the aircraft meets the published climb and turn conditions.

Beginning and standard case

The procedure begins at the DER. An aeroplane does not turn before reaching 120 m, 394 ft, above aerodrome elevation and not sooner than 600 m from the runway beginning. Helicopter turns may begin at 90 m, 295 ft. If no obstacle penetrates the 2.5 percent OIS and 90 m MOC prevails, a 3.3 percent climb to 120 m permits a turn in any direction. The inner construction applies if that height is reached within 3.5 km, 1.9 NM, of the DER.

Obstacle-driven solutions

Areas 1 and 2 widen ahead of the runway; Area 3 supplies the circular protection after the turn. An obstacle can shorten the available distance or close a sector.

A SID combines obstacle protection, navigation and ATC flow into a charted route from the runway to the en-route structure.

SID termination

The SID begins at the DER and ends at the first fix, facility or waypoint of the en-route phase. That significant point marks where clearance for the next phase is assured.

Published information

CLIMB VIA SID retains the published level and speed restrictions unless ATC explicitly cancels or amends them. A direct routing or vector can shorten the SID only when issued by ATC and supported by obstacle clearance.

Minimum sector altitude

An MSA normally provides at least 300 m, 1,000 ft, obstacle clearance within 25 NM of the stated facility or reference point. It is an emergency reference, not permission to leave the SID.

RNAV converts sensor data into position, track, distance and steering guidance. A computer can process bad data consistently, so database and sensor checks remain essential.

Navigation systems

Straight departure and SBAS

The first waypoint after the DER determines whether the initial RNAV track is within 15 degrees. An SBAS straight departure supplies a nominal full-scale deflection of 0.3 NM to the first turn-initiation point.

Four turn types

The crew confirms approval for the navigation specification, database currency, sensor availability and continuous performance monitoring. An FMS overlay of a conventional SID is monitored with the underlying raw data.

The published departure protects a normally operating aircraft. The operator separately proves a safe path after an engine failure, especially after V1.

Operator responsibility

The briefing identifies the engine-out track, acceleration altitude, safe altitude and rejoin point. That route may differ from the SID because all-engines PDG and one-engine-inoperative performance solve different problems.

Pre-departure decision

If performance cannot meet the gradient, reduce mass, wait for better conditions, select another runway or route, or obtain an assessed alternative clearance. Telling ATC alone cannot create obstacle clearance.

Noise-abatement procedures alter thrust reduction, acceleration and flap retraction. They never relax obstacle clearance, aircraft limits or ATC restrictions.

Common foundation

Take-off power and configuration continue through the initial climb, with gear retracted when safely airborne. The first noise-driven action is not initiated below 800 ft above aerodrome elevation. By 3,000 ft the aircraft transitions to normal en-route climb unless an approved aircraft-specific procedure says otherwise.

NADP 1 and NADP 2

Briefing priorities

Confirm runway, SID, transition, turn types, maximum speeds, PDG, level constraints, engine-out route, thrust reduction and flap schedule. Obstacle protection and aircraft limitations govern if a generic noise profile conflicts.