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145.A.25 requires that a maintenance organisation has facilities appropriate for all planned work, including hangars, workshops, offices, and storage areas that protect personnel and aircraft or components from weather and environmental contamination.
What it means in practice
The organisation must have hangars, workshops, and office space adequate for the maintenance tasks it is approved to perform. For base maintenance, hangars must be large enough to accommodate the aircraft types on the approval and must protect both the aircraft and personnel from weather. For line maintenance, suitable arrangements must be in place even if a full hangar is not always available, though shelter must be provided when required by the nature of the task.
Storage facilities must be secure and properly controlled to prevent deterioration or damage of components, equipment, tools, and materials. Separate storage is required for serviceable and unserviceable components to prevent inadvertent installation of defective parts. Environmental conditions such as temperature, humidity, and cleanliness must be controlled where required by maintenance data or component standards.
Key requirements
Facilities must protect against weather, dust, and other environmental contamination for all planned tasks. Specialised workshops and bays must be segregated as appropriate to ensure that environmental and work-area contamination is unlikely to occur — this is why disciplines such as composite repair, non-destructive testing, or avionic calibration are typically housed separately, even though the regulation does not list specific disciplines. Office accommodation must allow management, planning, and technical records staff to carry out their duties effectively, and AMC 145.A.25(b) recommends it should also allow certifying staff to consult maintenance data and complete maintenance records properly. The size and layout of facilities must be proportionate to the volume and complexity of work.
Under 145.A.25(c), the working environment, including hangars, workshops, and offices, must be appropriate for the task carried out and must not impair the effectiveness of personnel: temperature, dust, noise, lighting, and other environmental conditions must be controlled so that personnel can perform tasks without their effectiveness being impaired, and the environment for maintenance must meet the requirements of the applicable maintenance data. Critically, 145.A.25(c) requires that where the working environment deteriorates to an unacceptable level — for example through temperature extremes, swirling dust, hail, ice, snow, precipitation, electrical storms, wind, or inadequate moisture or lighting conditions — the affected maintenance tasks must be suspended until satisfactory conditions are re-established. This applies with particular force to line maintenance performed outside a hangar.
Storage facilities for components, equipment, tools, and material must be secure, with segregation of serviceable from unserviceable items. AMC 145.A.25(d) adds that storage conditions should keep parts clean, dry, and well ventilated, with racking strong enough to prevent damage and distortion, and with components remaining in protective packaging to prevent deterioration; storage conditions must follow the manufacturer's instructions where specified.
Common compliance gaps
Organisations frequently underestimate storage requirements, leading to serviceable and unserviceable components being stored together or in conditions that risk contamination. Another common gap is line stations that lack adequate shelter or lighting for the tasks being performed, particularly for overnight work in adverse weather conditions. A related and often-missed obligation is the failure to formally suspend maintenance when environmental conditions degrade below the standard required by 145.A.25(c) — continuing weather-exposed line tasks during precipitation, electrical storms, or high winds is a direct non-compliance, not merely poor practice.
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