Exercise Pitch Black 2012

Noise Monitoring27 July – 11 August 2012

Introduction

• Exercise Pitch Black is conducted in the Northern Territory and is the largest Air Force exercise in the Southern Hemisphere. In 2012, it involved over 2,200 personnel and up to 100 military aircraft from Australia, New Zealand and several other foreign nations.

• Defence undertook noise monitoring to assist with understanding the noise impacts from the Exercise. Ten recording noise monitors were placed at locations surrounding RAAF Base Darwin and in nearby suburbs for a two week observation period, 30 July to 10 August.

• Observers in various locations documented flights of both military and civilian aircraft.

• This information was compiled and cross referenced to present the total noise impacts from the Exercise at the monitoring locations and also to compare various aircraft and flight movements.

The purpose of Pitch Black

• Exercise Pitch Black is a biennial activity that brings together the Air Forces of several nations to practice large formation offensive counter air and offensive air support operations.

• Exercise Pitch Black recognises the strong relationship Australia has with its participant nations, and the high value it places on regional security and fostering closer ties throughout the Asia Pacific region.

• Up to 100 aircraft use airspace over Bradshaw Field Training Area and Delamere Air Weapons Range.

• The Northern Territory is well situated to conduct Exercise Pitch Black. RAAF Bases Darwin and Tindal each have facilities that allow them to host visiting aircraft.

• The airspace surrounding Delamere and Bradshaw is amongst the world’s largest training airspace.

• The proximity of Northern Australia to regional neighbours makes it a suitable location for other Air Forces to deploy.

Pitch Black 2012 Fly Neighbourly PolicyThe following is an extract of the noise mitigation strategies employed by Defence to minimise the noise impacts on Darwin during Pitch Black 2012:

• All flying activity relating to the exercise commences after 9am and ceases before 11pm, with no exercise related flying on weekends.

• Use of afterburner for takeoff is limited to only when operationally essential.• No continuous circuits for training at Darwin, in order to minimise noise.• Departure and recovery procedures used are efficient and designed to recover jets in

the minimum time with the minimum amount of noise to all Darwin residents; efficiency minimises the noise generated.

• All departures for military jets are flown by maintaining the runway heading until 10nm or 5000ft (which ever comes first), before a turn is made to outbound track. This minimises the noise for departure to well out to sea for Runway 29 and over sparsely populated areas to the south east of Darwin, and over Robertson Barracks. 

• All night recoveries are via straight in approach, for both safety and an effort to share noise.

• All daytime recoveries are via an initial and pitch. Aircraft maintain 4000ft until 10nm from the field on extended centreline, descend to 2000ft overhead the airfield, then complete a downwind and base leg, descending from 2000ft only when turning base to land.

• On Runway 29 the initial and pitch takes the aircraft over Winnellie on downwind at 2000ft, then in a descending right hand turn just south of Fannie Bay racecourse, then over Fannie Bay and East Point, before lining up with the runway to land. 

• The normal altitude for the initial and pitch is 1500ft; however, it is flown at 2000ft at Darwin to minimise noise. It is not possible to safely and efficiently execute the base turn from any higher than 2000ft.

Noise Monitoring Locations

Noise metrics – what are we measuring

Equivalent Noise Level – L(A)eqThe constant sound pressure level which exhibits the equivalent acoustic energy of a fluctuating noise level. Otherwise known as the “Energy-Average” sound level, or “Equivalent Continuous” sound level.

Maximum Noise Level – L(A)maxThe maximum instantaneous time weighted noise level during a noise measurement period.

Noise metrics – what are we measuring

Number of Noise Events (N70 and N85)• The ‘number above’ (Nx) metric is the number of noise

events that exceed a nominal noise level. For example N70 is the number of events that exceed 70dB(A).

• This assessment method is useful for civilian airports where there is a clear time interval between aircraft movements; however, this method has some limitations when it is applied to military aircraft movements.

• For example, a formation of four aircraft taking-off could exceed 70dB(A) at the RAAF golf course (location 7) continuously for the entire take-off. The event may span two consecutive minutes.

Overall Observations• In total 798 aircraft events were observed during Pitch Black 2012, in the two

week observation period. • In this study, an event is defined as an aircraft, or aircraft formation movement

that is reasonably isolated from other aircraft or aircraft formation movements. For example, a formation of four F/A-18s taking off is considered one event. An aircraft event is distinctly different to an N70 or N85 noise event described on the following slide.

Total military N70 and N85 during the Exercise (30 Jul - 10 Aug)

• Note: these are military N70 and N85 noise events and are different to the ‘aircraft events’ described on the previous slide

Overall L(A)eq (30 Jul – 10 Aug)

Overall maximum noise levels (30 Jul – 10 Aug)

Overall noise impacts

Occupational noise impacts

• Regulations specify an exposure standard of 85dB(A) 8hr, Leq and 140dB Lc peak. This exposure standard is based on both the National Standard for Occupational Noise 2000 [NOSHC:1007(2000)] and the associated National Code of Practice for Noise Management and Protection of Hearing at work [NOHSC:2009(2004)].

• Limits for occupational noise were not exceeded during Exercise Pitch Black 2012 at any location during the monitoring period, except at the RAAF Golf Course on a single day.

• The RAAF Golf Course was the location exposed to the highest noise levels during Pitch Black and was the only location that exceeded the 8hr, 85dB(A) Leq. For one day of the noise monitoring period (2/8/2012), a person standing at the RAAF Golf Course logging location for the full duration of the military events would just exceed the occupational noise standard, if no hearing protection was worn. All other days were within the occupational noise standard.

• All other monitoring locations were subject to much lower noise levels and did not exceed the occupational noise standard.

RAAF Golf Course

• The RAAF Golf Course is directly under the flight path for aircraft landing on Runway 29. It is on Defence property, significantly closer to the runway threshold than any local residential areas.

• For one day of the noise monitoring period (2/8/2012), a person standing at the RAAF Golf Course logging location for the full duration of the military events would just exceed the occupational noise standard, if no hearing protection was worn. All other days were within the occupational noise standard.

• At no stage during the monitoring period did Defence record an exceedance of the 140dB Lc peak standard

Conclusion

• Noise measurements from this study are consistent with the Noise and Flight Path Monitoring System measurements conducted at Darwin in 2011.

• Occupational noise limits were not exceeded during Exercise Pitch Black 2012 at any location during the monitoring period, except on one day at the RAAF Golf Course. The RAAF Golf Course is directly under the flight path for aircraft landing on Runway 29. It is on Defence property, significantly closer to the runway threshold than any local residential areas.

• Average noise from military fast jets is generally 10-15 dB higher than from commercial aircraft at residential areas not immediately adjacent to the airport.

• Directly under the flight path, fast jets are typically 10-20dB higher. • The primary noise source for military jets is the shearing of ambient air by the exhaust

of the jet engines.• The large amount of civilian commercial traffic at Darwin during the day, prevents the

recovery of high numbers of fuel limited military fighter jet aircraft via any means other than initial and pitch.

• Full afterburner take-offs cause a large amount of low frequency noise. Aircraft that disengage the afterburner sooner have less noise impact.

• Locations at either end of the runway are subject to the greatest noise impacts.• Areas at either end of the runway should be protected from residential encroachment

where possible.