1. Explosives forming part of an aircraft system are part of the certified type design11. Managing design changes for such systems, including their explosives components, is within a MDO’s scope unless expressly exempted in the MDO’s certificate of approval.
Design changes for aircraft systems containing explosives
2. MDOs managing the design of aircraft systems containing explosives should follow their normal design change processes, while also:
performing the activities detailed at 7.6.6.16 to ensure compliance with all applicable ESRF requirements
obtaining specialist explosives advice (7.6.6.16a) as early as practicable in the design change management process
creating links to selected organisations at 7.6.6.18, documented as detailed at 7.6.6.22, that can be exercised as necessary.
considering what other stakeholders may contribute to safe design, as discussed at 7.6.6.23
using recognition for explosive-related design changes, where appropriate, except for explosives lifing discussed below.
Lifing
3. The ESRF uses the term ‘explosive ordnance’ (EO) to describe all munitions containing explosives, nuclear fission or fusion materials and biological and chemical agents22. EO degrades with age and exposure to the environment, so cannot be reliably guaranteed to be safe after a certain point in time. Accordingly, the following EO lives are created based on a rigorous qualification process and extensive testing:
Service Life. The Service Life is the maximum period for which an EO item, whilst stored and when subsequently used in its operational or training role, may be expected to remain safe and continue to meet its defined function and performance requirements.
Storage and Transport (S&T) Life. The S&T Life is the total period for which an EO item, under specified conditions, may be expected to remain safe to store and transport. The S&T Life encompasses the Service Life and the EO’s disposal phase.
Operational Life. An Operational Life is assigned where the operational environment is expected to result in an accelerated rate of aging relative to that experienced in the storage environment. The Operational Life is therefore a subset of the Service Life. The types of Operational Life most often used for explosives within aircraft systems (termed ‘installed EO’ within the ESRF) are Unpacked Life and Installed Life. Note that ‘installed EO’ should not be confused with items that only have an Installed Life. The Operational Life for ‘installed EO’ may be an Unpacked Life, and some ‘installed EO’ may only have a Service Life (ie no defined Operational Life).
4. These EO lives are shown diagrammatically in Figure 1, which illustrates two scenarios for the same EO item. The start of the S&T Life and Service Life is typically based on the Date of Manufacture. In Case 1, the Operational Life starts later in the lifecycle, and the Service Life ends up limiting the life of the item before the disposal phase starts. In Case 2, the Operational Life starts earlier and ends up limiting the life of the item. DEOP 101 Regulation 2.5 Explosive Ordnance Life and DEOP 102 Part 2 Chapter 10 Determine Life provides further information on EO lifing.
Figure 1: EO Life Cycle
Managing EO lives under the DASF
5. Explosives are mainly used within safety-critical aircraft systems required to work first-time, on-time with high reliability. Malfunction of such systems, including failure to actuate when commanded, will usually result in serious or fatal injury and/or prevent continued safe flight and landing. Therefore, DASA’s default position is that the Service Life and Operational Life for ‘installed EO’ should be treated as Airworthiness Limitations (AwL)33 However, DASA would consider exceptions to this based on sufficient justification that failure of ‘installed EO’ would not result in an unsafe condition44. Where an AwL exists for ‘installed EO’, it must be included in the AwL section of the ICA as defined by the applicable airworthiness codes.
6. Although these life limits are considered to be AwLs, routine inspections and ‘in-service surveillance’ of ‘installed EO’ are not to be treated as AwLs. Routine inspections may occur before installation or when an assembly (such as an ejection seat or bomb rack) is removed from the aircraft. Some installed EO may also be subject to inspections or testing for in-service surveillance purposes (refer DEOP 102 Part 2 Chapter 11). These activities are conducted to gather additional data about the ‘installed EO’s’ real-world performance.
7. Both the Service Life and Operational Life (where defined) for ‘installed EO’ (whether treated as an AwL or not) should be included in the respective Aircraft Maintenance Program as both these lives limit how long the ‘installed EO’ can be used in the aircraft. The S&T Life does not need to be included as it only affects the disposal phase.
Amending ‘Installed EO’ lives
8. Classification. A change to the type design is to be classified ‘major’ when the change alters AwLs (GM DASR 21.A.91). Therefore, amendment of an ‘installed EO’ life limit should be processed as a major change if the life limit is considered an AwL. If the ‘installed EO’ life limit is not considered an AwL, amendment of the life limit could be classified as a minor change, assuming other criteria for a major classification are not met. The minor change could then be approved by an appropriately privileged MDO. DASA should be contacted for queries regarding classification of changes for ‘installed EO’ life limits, including formal requests for re classification from major to minor.
9. Leveraging other approvals. DASA’s recognition framework does not consider explosives safety. Accordingly, recognition by DASA of a Military Aviation Authority (MAA) does not include any explosive-specific aspects of the foreign military’s system. By extension, DASA recognition certificates will not list explosive-specific authorisations issued by foreign militaries55. Therefore, when a foreign military publishes an ‘installed EO’ life amendment, DASA recognition typically cannot be leveraged since the native approval artefact will not be listed in the recognition certificate. However, a foreign airworthiness authorisation, listed in the DASA recognition certificate, may inherently cover changes to ‘installed EO’66. Applicants could then leverage prior certification to claim relief from developing compliance demonstration evidence under DASR 21.
10. Within the ESRF, Explosive Materiel Branch (EMB) approves and promulgates EO life amendments after an EO life assessment77. For aircraft with ‘installed EO’, the assessment will typically be performed by Aerospace EO Systems Program Office (AEOSPO). The outcome of its assessment will either be that EMB is:
able to approve the life amendment, or
unable to approve the life amendment, and instead may provide an assessment of risk related to the amendment for consideration and acceptance by the appropriate risk management authority88
11. Processing ‘Installed EO’ AwL amendments. The processing of an ‘installed EO’ AwL amendment under DASR 21 depends on the outcome of the EMB assessment as follows:
EMB approval. Applicants should submit a ‘simple’ major change to DASA, using Form 31A, that references the EMB approval and consideration of any additional aircraft integration aspects99. Where the proposed life amendment has originated from another military operator, applicants should include the relevant MAA airworthiness authorisation (if applicable) and a Configuration, Role and Environment (CRE) delta assessment if such an assessment was not considered as part of the EMB approval. DASA approval of a Form 31A should be routine. A Form 31A should be used to proposed amendments that will be enduring / long-term (typically applied at part number level) as well as short-term amendments (typically asset level or lot/batch-specific). Whilst not essential, applicants may seek DASA agreement on a standing Certification Program Plan (CPP) for ‘installed EO’ life limit amendments that would further streamline individual Form 31A processing.
Risk-based approval. An amendment to an ‘installed EO’ life limit not approved by EMB and that requires risk management represents a TCB non-compliance. The risk management process should integrate both explosive safety and aviation safety considerations. The most appropriate pathway for DASR 21 approval is as follows, depending on whether the risk-based life limit amendment will be enduring / long-term or short-term:
For enduring / long-term life limit amendments, applicants should engage with DASA to agree to TCB tailoring through an ‘Exception’ Military Certification Review Item (MCRI), supported by the operator’s risk management analysis. Such an MCRI could be standing and apply to all similar situations where the EO life amendments will be based on risk management. Once the MCRI is agreed, a Form 31A may be submitted to DASA. DASA acknowledges that not all Defence TCBs will have explicit requirements for ‘installed EO’ that can be identified in an Exception MCRI1010. Nonetheless, DASA considers the Exception MCRI the most suitable mechanism to document the non-compliance, so encourages applicants to engage early with DASA to define the MCRI contents. Whilst not essential, applicants may seek DASA agreement on a standing CPP for ‘installed EO’ life limit amendments that would further streamline individual Form 31A processing.
For short-term life limit amendments (which are often asset level or lot/batch-specific, and time-sensitive), a Military Permit to Fly would provide a suitable and flexible authorisation.
