Airport noise allowances explained 

Engine testing occurs during the night as plane maintenance can't occur during the day when aircraft are flying. Regular maintenance is essential to a safe commercial aviation industry in New Zealand. Following overnight maintenance, the engines must be tested before aircraft go back into operation early the following morning.  

On-wing aircraft engine testing noise

On-wing aircraft engine testing is any engine test performed while the engine is attached to the aircraft. These engine tests are undertaken outside at various locations, depending on factors like wind direction, runway use and aircraft type. The noise emitted from these tests can be disruptive for nearby residents or sensitive activities.

In contrast, off-aircraft engine testing occurs when aircraft engines are removed for more rigorous repairs and testing occurs in an enclosed test cell. Because the testing happens in a closed environment, the potential for noise impacts are limited for these types of tests. 

It’s important to note aircraft engine testing does not include noise from aircraft taxiing, take-off and landing. Instead, this kind of noise is called aircraft operational noise and has to comply with a different set of noise restrictions explained further down the page.

The Christchurch District Plan has a number of restrictions regarding engine testing noise. To simplify, the plan states:

• Aircraft engine testing noise shall not exceed 65 dB L_dn at the 65 dB L_dn engine testing noise contour, calculated as a 7 day rolling average   
• Aircraft engine testing noise shall not exceed 55 dB L_dn at the 55 dB L_dn engine testing noise contour, calculated as a 7 day rolling average 
• The noise emitted from engine tests shall not exceed a 75 dB L_Amax between 10pm and 7am only as calculated at the edge of the residential zone  
• All high power turbo-prop engine tests that are five minutes or longer between 10pm and 7am must be carried out on the threshold of Runway 11 unless otherwise in use  
• There will be no high power jet engine tests carried out between 10pm and 7am unless the test is 'Unplanned' or exempt 
• The airport is only allowed to undertake five ‘Unplanned’ or exempt tests per quarter or 12 per year. 

Exemptions to the above restrictions only apply to tests that are:   

• Undertaken on aircraft associated with Antarctic Operations 
• Signed off by the Civil Aviation Authority or Minister of Transport 
• Required as a result of an airline model defect 
• Required as a result of a natural disaster.