Approach to Address RM Issues

Rationale for a risk management approach

Agricultural aircraft operate in an environment where many of the relevant parameters are variable over time and from place to place (e.g. wind speed, wind direction, temperature, location of the application target, the coverage required, and the surrounding activities and areas). Therefore it can be challenging to manage the effects of these operations through plan provisions and controls that will be appropriate for all situations.

Traditionally the approach has been to prescribe limits or specifications, such as how the operation should be carried out. Such a prescriptive approach assumes that compliance with requirements will achieve the desired outcomes and can often result in a complex suite of requirements to catch all possibilities, which may not actually adequately address the actual situation or achieve the desired outcomes.

This guidance note promotes a risk assessment/management approach to address the actual risk of the situation and the use of appropriate performance standards to achieve desired outcomes. This approach is intended to provide more flexibility in how outcomes are to be achieved while providing clear performance standards for operators to meet (e.g. “no fertiliser directly into water”).

Adopting a risk management approach requires the person responsible for the discharge to assess the situation and circumstances and adopt appropriate procedures to ensure that risks are appropriately managed and the performance standards are achieved. For agricultural aviation activities, a risk management approach requires a pilot to:

  • Undertake an assessment of the risk of the application which takes into account the nature of the substance being discharged and the actual (real time) situation.
  • Choose appropriate actions to address and minimise the identified risks.
  • Follow best practice when undertaking their operations and be able to verify that.

Under this approach a pilot must also accept the responsibility for the outcome and take all practicable steps to minimise the risk. If requested, a pilot should also be able to demonstrate how the activity was carried out and that the performance standard was achieved. For example:

  • What discharges occurred?
  • Where did the discharge go?
  • What were the (weather/real time) conditions at the place and time of application?

The methods adopted and requirements for verification should reflect the level of risk of the application. Technical information relating to the Agricultural Aviation Industry contains relevant technical information for pilots to manage risk, and to satisfy the task verification requirements by any authorised third party. These methods enable operators to demonstrate that aerial application tasks were carried out according to industry best practice.

The risk management approach

Risk assessment management is a well-established approach to manage a range of activities. This approach is based on the relationship between hazard, exposure and risk where:

Hazard x Exposure = Risk (level)



Something that could present a risk – a potential adverse effect



The extent to which people and/or the environment   are exposed to the hazard



The combination of the nature of the hazard and level of exposure determines the degree/magnitude of risk


The state and nature of the substance influences the degree of hazard from aerial application of fertilisers, agrichemicals and VTAs, the degree of exposure and hence the risk. The following table compares the risk of off-target drift based on the state of the substance and its ballistic properties (the extent to which the trajectory of released particles can be predicted).

Table 1:Comparative risk of off-target drift as a function of the state of the substance (i.e., solid, liquid or vapour) and particle size (ballistic properties)

                    Potential off-

                     Target drift


ballistic properties        







< 200 µm




0.5 mm




> 1 mm




* = with larger droplet sizes the potential for droplet shatter into smaller droplets increases thereby increasing the risk. The same applies to large solid particles that break up when discharged.

Understanding the comparative risk of off-target risk is important as the state of the substance varies between fertilisers, agrichemicals and VTAs:

  • Fertiliser - As well as typically being relatively low hazard most fertilisers are in a solid form and particles are larger than 0.5mm (i.e. a low hazard substance can more effectively be contained to the target area).
  • Agrichemicals - Most agrichemicals are applied in liquid form and although the means to contain them to the target is available, the larger droplet sizes may mean a reduction in efficacy of the agrichemical which is a dis-incentive. Increased spray drift potential is closely linked to small droplets (< 200 µm).
  • VTAs - VTAs (1080 Bait) are most often applied in a compressed cereal “cylinder” which weigh about 6-12 gm each, and therefore it is entirely a matter of where it is directed that determines where it goes. Local wind and variation in temperature will be the main determining factors of risk.

Once the level of risk from the hazard is identified, steps can then be taken to eliminate the hazard, isolate the hazard, or reduce exposure to it. This approach involves asking relevant questions so that the best option to manage the risk can be identified, as set out in the following table:

Table 2: Managing the risk 

Is there a risk?

Contributing factors

Reference in Guidance Note

Is the risk significant?

Combination of likelihood and potential adverse effect

Table 3

What could be the adverse effect from the hazard?

Potential adverse effects

Resource management issues

What are the possible reasons for the adverse effect?

Risk factor

Table 4

How could it occur?

Exposure pathway

Exposure pathways

How can the potential effect be managed?

Management options

Table 4

Fertiliser – Table 5

Agrichemicals – Table 6

VTAs – Table 7


To assess the significance of the risk, both the likelihood of the adverse event occurring and the potential impact need to be determined. Refer to Technical Information relating to the Agricultural Aviation Industry (Section 2 – Risk Management).

A risk matrix, as set out below, can also be used to assess the level of risk based on the likelihood of an adverse effect together with the potential impact of that adverse effect. The colours indicate the degree of risk. Management options can then be selected that reflect the degree of risk, which may include not undertaking aerial applications at that point in time.

Table 3: Is the risk significant?

Table 3 

Applying a risk management approach to agricultural aviation discharges

The following sections provide guidance on managing the effects of discharges from the industry, focusing on the three main types of substances that are applied from the air – fertilisers, agrichemicals and VTAs. Understanding the nature of these discharges and associated potential adverse effects is important to ensuring the management approach is focused on the actual risk factors associated with the substance being applied.

Managing the risk

Managing the risk should involve the following steps:

Risk Factors

The reasons for and magnitude of potential adverse effects from agricultural aviation operations is related to a range of risk factors. The extent to which a risk factor applies varies according to the nature of the receiving environment and on the type and nature of the discharge.

Key risk factors to consider include:

  • The chemical being used.
  • The exposure pathway.
  • The concentration and rate of application of the substance.
  • The timing of the application and its proximity to people and sensitive areas (including water bodies).
  • The location of the application and use, including mixing sites.
  • On site/real time weather conditions and their suitability for the task/application.
  • Substance characteristics (e.g. particle size or ballistic properties).
  • Accuracy of the target identification.
  • Application height.
  • Application equipment.
  • The permeability of the soil.

A risk based approach enables management controls to be clearly linked to these risk factors in order to manage potential adverse effects. Further information is available in Technical Information relating to the Agricultural Aviation Industry (Section 2 – Risk Management).

Risk assessment factors

Once the relevant risk factors have been identified, these can then be assessed to determine the appropriate information requirements and pilot management options. Distinguishing between pre-determined and real-time risk assessment factors is important because the most significant factor causing adverse
effects from off-target spray drift is almost always wind direction – a real-time factor. The real-time factors are those which can vary over the time of the operation, such as the weather conditions. A pre-determined factor is one that is evident and on which decisions are made before the application commences. These real-time and pre-determined risk factors are identified in Table 4 along with corresponding information requirements and pilot management options. This table is based on a risk management approach with requirements and management options based on the level of risk from each factor.


Table 4:Risk assessment requirements and management controls for aerial application of fertiliser, agrichemical* and VTA





Risk assessment requirements  


Information needed


Information able to be used for task verification


Pilot Management



Application site (target)

Location and boundaries

  • GIS co-ordinates, dated photograph
  • Hand-written diagram or map, verbal

Application plan with map detailing location and boundaries. Use of GPS system to ensure coverage and avoid drops beyond target area boundaries.


Sensitive area

Nature of and location with respect to application area

  • GIS co-ordinates, dated photograph
  • Hand-written diagram or map
  • Verbal only if task is low risk

Sensitive areas identified and actions taken to avoid adverse effects


Wind direction

Direction (bearing) at the application site at the time

  • Digital recording wind vane/sensor with time base
  • Hand held vane or equivalent
  • Smoke or other visual indicators

Adjacent to sensitive areas, aerial application only when wind is away from sensitive areas and when wind speed is steady


Wind speed

Wind speed at the application site at the time

  • Digital recording wind vane/sensor with time base
  • Hand held anemometer or equivalent
  • Smoke or other visual indicators

Adjacent to sensitive areas, no application when wind speed exceeds the limits according to the risk.


Particle size

Physical properties of the product being applied

  • Documented record of particle size and size range, and stability, i.e. volatility (liquid) or fragmentation (solid)

Adjacent to sensitive areas, physical properties of the product must be such that trajectory after release is predictable


Product hazard

HSNO hazard classifications and controls, bio-accumulation, water solubility and attributes relevant to potential adverse effects.

High risk situations may require more information, for example there may be specific situations where the product hazards limit the time of day or season when they can be used.

  • Product selected according to application task, taking account of HSNO class, efficacy, other attributes that may result in greater risk (e.g., volatility) and the at-risk sensitive locations, all according to written prescriptions and documented

Choose least hazardous product suitable for the task

Extra care taken if using Classes 6.1A, 6.1B, 6.1C, 6.7, 6.9, 9.1A, 9.2A, 9.3A and/or 9.4A adjacent to sensitive areas


Effective height of release of product

Application method, including lateral spreading vs localised

  • Application equipment selected to minimise product losses between the point of release and the target, all fully documented

Product directed to the target at all times


Buffer zone

Downwind application free zone

  • Location of application target and sensitive area known and logged, communication/notification confirmed, product quality, and wind direction known and drift modelling done

Adjacent to sensitive areas, application only when wind is away from sensitive areas and is a steady wind speed


Shelter belts

Nature of and location with respect to application area

  • Location of application target and sensitive area known and logged, communication/notification confirmed, product quality, and wind direction known and drift modelling done

Adjacent to sensitive areas, application only when wind is away from sensitive areas and is a steady wind speed

Also operation must be planned to take account of hazards associated with shelter trees and structures



Air temperature

  • Humidity measured and recorded on site at the time

Specific controls according to the volatility of the product being applied


Atmospheric stability

Inversion layer

  • Wind and temperature data recorded on site such that no inversion layer, and visual clues e.g. smoke to test for inversion according to the risk

If label information indicates volatility an on-site test for inversion layer should be done

* Refer to NZS 8409 (Appendix G)

** A real time factor i.e., factors that can change while the application is occurring (e.g. wind speed and direction).

Exposure pathways

The indirect exposure pathways for adverse effects are:

  • Off-target drift or dust – Off-target drift is where the product drifts beyond the target area and this may, or may not, lead to adverse effects, depending on the nature of the non-target area. For example, lime dust on a neighbouring farming property may not be regarded as an adverse effect by the owner whereas lime dust on a roof where water is being collected is likely to be regarded as an adverse effect.
  • Overland flow - This is where there is runoff from land when product has been applied and the runoff flows overland with product entrained in the flow ending up in a water body. Operators can minimise the risk of this occurring by ensuring the product has time to be absorbed before heavy rainfall events.
  • Leaching through soil - Leaching is the movement of a substance through the soil into groundwater. Leaching may only remove mobile components of the product while some immobile components remain bound to soil particles and may accumulate to unacceptable levels, such as cadmium build-up from phosphate fertilisers[1]. The potential for leaching depends in part on the chemical and physical properties of a product and the permeability of the soil. To reduce the potential for leaching, regional plans may have controls on the amount of product that can be applied (input control) or have limits on the amount of leaching that can occur (output control). The rate and type of product being applied needs to take into account any such requirements.

The direct exposure pathways for adverse effects are:

  • Applications direct to non-target area - This is where there is a direct application on a non-target area, such as a non-target crop, water body or sensitive area which may result in adverse effects. Such a situation may arise where insufficient care has been taken accurately direct and apply the substance to the target area. Management controls can be imposed that require applications to avoid non-target areas, water bodies or sensitive areas.
  • Frequency and rate of application - The frequency and rate of application can determine the potential for adverse effects, particularly soil contamination or leaching to water. It is the role of the land manager/owner (client) and applicator to ensure that relevant RMA, HSNO and ACVM Act requirements regarding the substances being applied are met. All farmers or growers applying products should prepare a management plan to ensure that the amount of product being applied is appropriate. The task of the aerial applicator is to ensure the land manager/ owner (client) has met relevant requirements and to apply the required amount of product to the target area as instructed by the land manager/ owner (client) and ensuring regional plan requirements for the application are met.
  • Exposure of public in public areas at time of application - Applications can occur in public areas, creating a risk of direct exposure. Care needs to be taken to ensure that public areas are free of people at the time of application.

Indirect and direct exposure pathways include:

  • Inappropriate disposal of wastes - Inappropriate disposal of surplus or waste could lead to product ending up in water bodies or sensitive areas. There are general disposal rules under HSNO relating to different classes of substance. Care should be taken to ensure that disposal does not lead to such effects.
  • Spillages/ overflows at loading sites - For aerial applications the loading site is the area between the storage area and where the aircraft stops for loading. The Safety Guidelines and the appropriate loading practices can be found in the Health and Safety section of the CAA website, and for VATs there are HSNO controls relating to spillages at loading sites. Care should be taken when loading substances, to ensure that the product is loaded into the aircraft to avoid excess product in one area otherwise this can lead to contamination of the specific area or leaching into water. If the loading area is near a waterbody or bore then extra care is required to ensure that no product ends up in the water.


[1] The Code of Practice for Nutrient Management (COPNM) sets out good practice for managing potential contaminants as a result of fertiliser applications (including cadmium).