For stowage compartments in the passenger and crew compartments it must be shown by analysis and/or tests that under the load conditions as specified in CS 25.561(b)(3), the retention items such as doors, swivels, latches etc., are still performing their retention function. In the analysis and/or tests the expected wear and deterioration should be taken into account. Stowage Compartment Latching Mechanisms:
(1)The following areas shall be considered in a special cabin interior for the purpose of designing latching mechanisms: Cabin crew member areas: Cabin crew member areas are those areas in the passenger cabin where cabin crew members may be seated during taxiing, take-off, and landing (these are typically zones in proximity to floor level emergency exits, although other areas may exist). To protect flight attendants from being struck by items dislodged from galley stowage compartments, it is common practice to install additional restraint devices (dual latching) to each stowage compartment located within a longitudinal distance equal to three rows of seats fore and aft of the cabin attendant seats. However, the following additional considerations may be used: A longitudinal distance of 2 metres (6.6 ft) may be used in case the ‘three rows’ criterion is difficult to assess due to widely spaced seating, Underseat and overhead stowage bins do not need to be considered, and A stowage compartment located in a closed unoccupied area during taxiing, take-off, and landing or behind a partition in the passenger cabin does not need to be considered. Passenger Areas: Passengers Areas are zones in which passenger seats designed for occupancy during taxiing, take-off, and landing are installed. In such cabin areas, if the means used to prevent the contents of the compartments from becoming a hazard by shifting is a latched door, the design should take into consideration the wear and deterioration expected in service. Non TTOL Areas: Non-TTOL areas are zones, separated from the remainder of the cabin by means of a door during taxiing, take-off, and landing (TTOL), in which no seat is installed (passenger or crew member) that may be occupied during taxiing, take-off, and landing, and which do not include any part of any possible egress route from the aeroplane (such areas may be for example lavatories, washrooms, bedrooms, closed galleys, etc.). In such areas, a single latch mechanism for stowage compartments is acceptable, provided that the door separating this area from the rest of the cabin is shown to be capable of staying securely closed under the applicable emergency landing conditions of CS 25.561 with an additional inertia load, uniformly distributed on the door, equating to the highest placarded allowable single compartment contents mass inside that area. Such single latch mechanisms do not need to be designed to account for the wear and deterioration expected in service.
(2)The following is provided as a clarification of the considerations to be followed when designing latching mechanisms, as well as of the means by which wear and deterioration expected in service may be substantiated: Single latch: A single latch is a latching mechanism capable of retaining a load derived from the specified maximum flight, ground and emergency landing load conditions. Dual latch: A dual latch is a latching mechanism composed of two independent single latching mechanisms each of which is capable of retaining a load determined by the specified maximum flight, ground and emergency landing load conditions. It is acceptable that a single operating mechanism (e.g. handle) operates with two independent latching mechanisms at the same time. Latch fail indication Latch fail indication is any means that permits clear visual confirmation that a latch is not properly engaged. In the case of a dual latching system, a single indication may serve for the two latches if it is ensured that the failure of either latch to properly engage will result in latch fail indication. All latches, whether single or dual, should include a latch fail indication. Wear and Deterioration Dual latching is a means of compliance to the wear and deterioration requirement. Where dual latches are installed there is no need to further demonstrate wear and tear. Consideration of wear and deterioration for single latches should be substantiated by test evidence, or analysis based on test evidence, showing that latch operation as intended by the design will be maintained following a simulation of full service life, with an appropriate scatter factor. A design life of 20 000 latch cycles may be used except if EASA finds the expected use of the aeroplane justifies more endurance substantiation. Demonstration of a 20 000 cycle design life can be accomplished by submitting the latch to a 100 000 cycle test representative of operational use, and verifying after the test that the latch is still able to operate as intended and is capable of withstanding ultimate load without failure.
(3)The above considerations regarding latching mechanisms, do not apply to compartments not accessible in flight for which a special tool is needed to gain access to (e.g. maintenance panel, access panels, etc.).
[Amdt 25/19]