GMGuidance material
GM No 1 to 21.A.93(b)(1)(iii) Interaction of changes to the type design and changes to operational suitability data (OSD)
In general, it has to be assumed that changes to the type design can have an effect on the OSD. Due to the alleviating nature of the OSD constituent master minimum equipment list (MMEL), the impact of design changes on the MMEL can be treated differently from the impact on other OSD constituents. Therefore, a separate GM No 2 to 21.A.93(b)(1)(iii) is available to explain the interaction between design changes and the MMEL. The following guidance is, therefore, only applicable to the other OSD constituents: flight crew data (FCD), cabin crew data (CCD), simulator data (SIMD), and maintenance certifying staff data (MCSD). In assessing the interactions between the changes to the type design and to the OSD, the following can be taken into consideration (see Figure 1): [Figure or form omitted from this preview — available in the Avioverse workspace library.] Figure 1
(a)Changes to the type certificate (TC) that only include a minor change to the type design (‘stand-alone’ type design changes) do not have an effect on the OSD. No dedicated assessment of the effects of the minor type design change on the OSD is needed in this case.
(b)TC changes that only include a major type design change do not need to be assessed for their effect on the OSD in case the experience of the applicant has demonstrated that similar changes do not have an effect on the OSD. Examples of major type design changes and their expected effect on OSD constituents are identified in Table 1 below.
Table 1: Examples of major type design changes and their expected impact on OSD constituents
| Discipline | Example of major type design change | Expected impact on OSD constituent | |||
|---|---|---|---|---|---|
| FCD | SIMD | CCD | MCSD | ||
| Structure | (i) Changes such as a cargo door cut-out, fuselage plugs, change to dihedral, addition of floats. | No | No | No | tbd |
| (ii) Changes to material, processes or methods of manufacture, or to primary structural elements such as spars, frames and critical parts. | No | No | No | tbd | |
| (iii) Changes that adversely affect fatigue or damage tolerance or life limit characteristics. | No | No | No | tbd | |
| (iv) Changes that adversely affect aeroelastic characteristics. | No | No | No | tbd | |
| (v) Aircraft weight changes such as maximum zero fuel weight (MZFW) changes or reduction in maximum take-off weight (MTOW) for operational considerations. | No | No | No | No | |
| Cabin safety | (i) Changes which introduce a new cabin layout of a sufficient extent to require a reassessment of the emergency evacuation capability, or which adversely affect other aspects of passenger or crew safety in aeroplanes with more than 19 passenger seats. | No | No | Yes, potential impact | No |
| (ii) Changes which introduce new cabin layout of a sufficient extent to require a reassessment of the emergency evaluation capability, or which adversely affect other aspects of passenger or crew safety in aeroplanes with 19 or less passenger seats. | No | No | No (unless assessment identifies need for CCD | No | |
| (iii) Installation of observer seat. | No | No | Yes, potential impact | No | |
| Flight | (i) Software changes that do not affect the pilot interface. | No | No | No | No |
| (ii) Software changes that affect the pilot interface. | Yes, potential impact | No | No | No | |
| Systems | (i) Updating the aircraft cockpit voice recorder (CVR) or flight data recorder (FDR) to meet a later standard. | No | No | No | No |
| Propellers | (i) Changes to: diameter, aerofoil, planform, material, and blade retention system. | No | No | No | No |
| Engines | (i) Power limit change | No | No | No | No |
| Rotors and drive systems | [Reserved] | ||||
| Environmental protections | (i) A change that introduces either an increase in the certified noise level(s) or a decrease in the certified noise level(s) for which the applicant wishes to take credit. | No | No | No | No |
| Power plant installation | (i) Modifications to the fuel system and tanks (number, size, or configuration) | No | No | No | tbd |
| Avionics | Comprehensive flight deck upgrade, such as conversion from entirely-federated, independent electromechanical flight instruments to highly-integrated and combined electronic display systems with extensive use of software and/or complex electronic hardware | Yes, potential impact | No | No | tbd |
(c)Design changes to aircraft for which OSD is not required in accordance with Article 7(a)(2) of Regulation (EU) No 748/2012, as amended by Regulation (EU) No 69/2014, cannot trigger the need to establish OSD.
(d)The OSD constituents SIMD and MCSD were not required to be included in the ‘catch-up’ OSD in accordance with Article 7(a)(2) of Regulation (EU) No 748/2012, as amended by Regulation (EU) No 69/2014. No design change can trigger the need to add that constituent.
(e)When the design change makes an OSD constituent applicable (see GM No 1 to 21.A.15(d) – Clarification of the applicability of operational suitability data (OSD) constituents) where it was not applicable before, that OSD constituent should be added to the application for the approval of the change to the TC.
GM — Regulation (EU) No 748/2012 · ED Decision 2025/016/R · Initial Airworthiness Easy Access Rules · EAR revision 27 Nov 2025