What is the acceptable classification for operational consequences of a proposed MMEL dispatch configuration when evaluated according to CS MMEL.140(a) and (b)?

Operational consequences of the proposed dispatch configuration, including any limitations and/or procedures, evaluated according to the criteria of CS MMEL.140(a) and (b) and classified as no safety effect or minor as per the associated type-certification basis of the aircraft definitions, are considered acceptable.

What severities may need to be complemented or increased in the MMEL safety assessment, and what effects must be carefully assessed?

Some severities set up for type certification may need to be complemented or increased, particularly the effects on crew workload and potential fatigue.

When can a failure assessed as minor for in-flight failure during type certification be considered more than minor for MMEL dispatch?

It may be considered more than minor due to operating for several flights in some operational conditions, and aggravating factors such as the number of flights of exposure, flight duration, flight rules, or special operations may need mitigation.

What kind of limitations may be needed to mitigate aggravating factors for MMEL dispatch, and can you give an example?

Limitations that would normally not apply for a full-up aircraft configuration may be needed, for example day VFR only instead of Day & Night VFR, or restrictions on types of operations.

GM5 MMEL.145(c) Justification of MMEL items

Q: Why should the classification of failure conditions from the aircraft and system FHAs be used carefully in the safety assessment for MMEL items?

The classification should be used carefully because the mitigation means associated with the proposed MMEL item may lead to a reduction in the severity that was identified for type certification purposes.

Q: In the example given, how can a failure that is major during a flight phase become acceptable for dispatch?

When the item is known to have failed on the ground prior to departure, the consequence may be less critical for the crew, and the application of the associated dispatch conditions can allow the classification to be reduced to an acceptable level.

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GM5 MMEL.145(c) Justification of MMEL items

ED Decision 2020/012/R

QUALITATIVE SAFETY ASSESSMENT — CONSEQUENCES OF THE PROPOSED MMEL DISPATCH CONFIGURATION

(a) Operational consequences of the proposed dispatch configuration (including any limitations and/or procedures) evaluated according to the criteria of CS MMEL.140 (a) and (b), classified as no safety effect or minor as per the associated type-certification basis of the aircraft definitions, are considered to be acceptable.

(b) The classification of failure conditions established in the safety assessment process through the aircraft and system FHAs should be used carefully, as the mitigation means associated with the proposed MMEL item may lead to a reduction in the severity that was identified for type certification purposes.

For example, the failure of one item during a particular flight phase may be considered to be major due to a temporary loss of function until the flight crew performs a manual reconfiguration during the flight. But when this item is known to have failed on the ground, prior to the departure, the consequence may be less critical for the crew, and the application of the associated dispatch conditions can allow the classification to be reduced to an acceptable level.

(c) Conversely, some severities that were set up for the purpose of type certification may need to be complemented or increased. In particular, the effects on the crew workload and potential fatigue need to be carefully assessed. Indeed, the severity of a failure that may have been assessed as having minor effects as an in-flight failure during the type certification may be considered to have more than minor repercussions due to operating for several flights in some operational conditions. Some aggravating factors (e.g. the number of flights of the exposure, the flight duration, flight rules, special operations) will sometimes need to be mitigated by limitations that would normally not apply for a full-up aircraft configuration (e.g. day VFR only, instead of Day & Night VFR, types of operations).

Details

Source-Title: GM5 MMEL.145(c) Justification of MMEL items View latest amendments

Erulesid: ERULES-1963177438-19601 Compare versions

Domain: Initial airworthiness

Amendedby: CS Issue 2

Applicabilitydate: 1 February, 2021

Entryintoforcedate: 18 August, 2020

Regulatorysource: ED Decision 2020/012/R Navigate

Regulatorysubject: CS-MMEL

Typeofcontent: GM to CS (Guidance material to certification specification)

Parentir: CS MMEL.145 Justification of MMEL items

Origin: EASA

Category: EAR