Noise Abatement Procedures - ATPL 070 — Operational Procedures

The flight-preparation lesson made the promise this lesson keeps: it taught the noise rule's headline, the operator's duty to establish departure and arrival procedures that minimise noise, with safety holding priority, and deferred the two standard departure procedures, their speeds and their heights, to here. This lesson pays that debt: the two NADPs in full, where the aerodrome-specific detail is published, and the list of conditions under which noise abatement is simply not asked for.

The operator's two procedures

The rule itself is short. Except for VFR operations of other-than-complex motor-powered aeroplanes, the operator shall establish appropriate operating departure and arrival/approach procedures for each aeroplane type, taking into account the need to minimise the effect of aircraft noise, and the procedures shall ensure that safety has priority over noise abatement and be simple and safe to operate with no significant increase in crew workload during critical phases of flight. The acceptable means of compliance turns that duty into a design: for each aeroplane type, two departure procedures should be defined in accordance with ICAO Doc 8168, and for each of them a single climb profile should be specified for use at all aerodromes, associated with a single sequence of actions; the two profiles may even be identical. The guidance explains the vocabulary: the climb profile is the vertical path that results from the pilot's actions, the power reduction, the acceleration and the slat/flap retraction, and the sequence of actions is the order and timing of those actions. The rule addresses only the vertical profile; the lateral track has to comply with the standard instrument departure (SID).

The two procedures split the neighbourhood between them. NADP 1 is designed to meet the close-in noise abatement objective, protecting the noise-sensitive areas near the departure end of the runway, and NADP 2 is designed to meet the distant objective, protecting areas further out along the climb. And above the whole design sits the commander's authority: the pilot-in-command has the authority to decide not to execute an NADP if conditions preclude the safe execution of the procedure. Noise abatement never outranks the commander's judgement of safety.

NADP 1 and NADP 2

Both procedures start identically: take-off thrust and a climb at V2 + 10 to 20 kt, and neither may begin its noise actions early, because a noise abatement procedure shall not be executed below 800 ft (240 m) above aerodrome elevation. From that gate they diverge. NADP 1 reduces power first and accelerates later: at or above 800 ft the power comes back to the noise abatement schedule from the aircraft operating manual, and the aircraft climbs on at V2 + 10 to 20 kt with flaps and slats still in the take-off configuration, holding that quiet, draggy climb until 3,000 ft (900 m), where it accelerates, retracts flaps and slats on schedule, and transitions to the en-route climb speed. NADP 2 accelerates first: not before 800 ft, and while maintaining a positive rate of climb, the aircraft lowers its pitch and accelerates towards VZF, the zero flap/slat speed, with the power reduced either with the initiation of the first flap or slat retraction or once flaps and slats are retracted, then climbs at VZF + 10 to 20 kt to 3,000 ft and transitions smoothly to the en-route climb speed. The two sequences of actions, reduce-then-accelerate against accelerate-then-reduce, are the whole difference: NADP 1 stays slow and quiet over the close-in houses, NADP 2 gets clean early and carries less thrust noise to the distant ones.

Where the procedures live

Two publication facts carry their own learning objectives. On the ground, a runway lead-in lighting system should be provided where it is desired to give visual guidance along a specific approach path for noise abatement purposes; the system itself belongs to ICAO Annex 14's aerodrome design world, and for this lesson the fact to hold is what it is for: lights that draw the approach around the noise-sensitive area. On paper, the air-law course's AIP lesson taught the three-part anatomy of the aeronautical information publication, and the noise chapter files exactly where that lesson predicts: detailed information about noise abatement procedures is found in Part 3, Aerodromes (AD), Sections 2 and 3 of the AIP, alongside the rest of each aerodrome's local data.

When noise gives way

Doc 8168 keeps two lists of adverse operating conditions under which noise abatement should not be required, and they are near-twins, so learn the shared skeleton first. Noise abatement in the form of a reduced-power take-off should not be required when the runway surface conditions are adversely affected by snow, slush, ice, water, mud, rubber, oil or other substances; when the horizontal visibility is less than 1.9 km (1 NM); when the crosswind component including gusts exceeds 28 km/h (15 kt); when the tailwind component including gusts exceeds 9 km/h (5 kt); and when wind shear has been reported or forecast or adverse weather such as thunderstorms is expected to affect the departure. That last item is the wind-shear lesson's precautions arriving from the other direction: the same conditions that argue for delaying a departure argue against flying it at reduced power.

The approach list repeats the skeleton, worded for the runway ahead: compliance with published noise abatement approach procedures should not be required when the runway is not clear and dry, affected by the same contaminant list; when the ceiling is lower than 500 ft (150 m) above aerodrome elevation or the visibility is less than 1.9 km (1 NM); with the same 15 kt crosswind and 5 kt tailwind gust-inclusive limits; and with the same shear-or-thunderstorm item. The ceiling entry is the one difference worth circling: the take-off list has no ceiling item, the approach list adds one. The approach procedures the lists protect are the continuous-descent, reduced-power and reduced-drag techniques, delaying flap and gear extension until the final stages; their own safety fences are that the aircraft cannot be required to be in anything other than the final landing configuration after the outer marker or 5 NM from the threshold, whichever is earlier, and that excessive rates of descent shall not be required.

The landing rule is one sentence, quoted whole because the exam quotes it whole: noise abatement procedures shall not contain a prohibition of use of reverse thrust during landing. The stopping device stays available on every landing; a procedure that forbade it would trade safety for decibels, exactly the trade the rule at the top of the lesson forbids.

The operator's two procedures

NADP 1 and NADP 2

Check you understood

Where the procedures live

When noise gives way