AMC to Appendix S, S25.10(c) Isolated Compartments

ED Decision 2017/015/R

(1)     Cabin Compartments

(a)      Compartments to be considered as isolated

Compartments in an aeroplane with an approved passenger capacity of less than 20 and a cabin length of 18.29 m (60 ft) or less do not need, in any case, to be considered as isolated. AMC 25.854 provides guidance on how to determine the cabin length.

S25.10(c) requires that a compartment in which a fire would not be directly or would not be quickly detected by occupants of another compartment must meet additional criteria in order to provide confidence that a fire will be detected. Such a compartment is described as an isolated compartment.

Any compartment that can be occupied by crew members and/or passengers during flight (other than accessible cargo/baggage compartments) should be considered as isolated for the purposes of showing compliance to S25.10(c) if it cannot be assured that fire/smoke in the compartment will be quickly detected by occupants of other occupied compartments of the aeroplane due to rapid smoke/fumes transmission enabled by the design of the aeroplane.

The assurance that fire/smoke will be quickly detected by occupants of other occupied compartments in the aeroplane may be provided by obvious smoke/fumes passage features, e.g. grills/louvres in a door, or via the aeroplane’s environmental control system air recirculation characteristics. Substantiation of the effectiveness of such declared smoke/fumes transmission means, via ground and/or flight tests, may be required. Detection of fire/smoke by occupants of another compartment only will provide the required assurance if there is confidence that this other compartment in question will be occupied, and not by sleeping persons (i.e. it is a compartment that meets the conditions set out in paragraph (1)(b)(ii) below). Thus, if smoke/fumes transmission is relied upon for compliance, the occupancy conditions of the aeroplane as a whole need to be taken into account.

(b)      Isolated compartments occupied for the majority of the flight time

S25.10(c) exempts isolated compartments (as described in paragraph (a) above) that are occupied for the majority of the flight time from being equipped with a smoke/fire detection system, based on the assumption that the occupants will quickly detect the fire.

(i)       However, some categories of isolated compartments will by their nature not be eligible for this approach, either because there is a risk that all occupants will be sleeping (sleeping persons will not be able to detect a fire starting in the isolated compartment), or because occupancy for the majority of the flight time cannot be realistically assessed. Examples include, but are not limited to, the following:

(A)     bedrooms, (i.e. rooms containing any sleeping installations intended to provide a high level of sleeping comfort, such as beds, or berthable divans, even if they also contain seats that can be occupied during taxiing, take-off, and landing; however, passenger seats do not need to be considered as sleeping installations in this context);

(B)     specialised rooms for which permanent occupation during the flight is unlikely (examples would include smoking rooms, cinema rooms, etc.);

(C)     washrooms/bathrooms, although the intent of S25.10(c) will be met in any case, if they are compliant with CS 25.854; however, a shower cubicle does not need to be considered an isolated compartment;

(D)     crew rest compartments; and

(E)     galley compartments.

(ii)      On the other hand, an isolated compartment, unless meeting one of the criteria in (i) above, will be accepted as being occupied for at least the majority of the flight time, thus providing for smoke/fire detection by the occupants, if any of the following conditions are met:

(A)     it is the flight crew compartment

(B)     all required cabin crew seats are located in the isolated compartment;

(C)     the isolated compartment contains a crew station that due to its specialised purpose, is likely to be occupied for the majority of the flight time;

(D)     the number of seats in the isolated compartment (including cabin attendant seats and seats in excess) approved for occupancy during taxiing, take-off, and landing is at least equal to the number indicated in the right hand column of the table below.

                   Note: the ‘Up to 19’ figure is included for the case of an aeroplane with a total cabin length in excess of 18.29 m (60 ft).

(iii)     In addition, an isolated compartment featuring no seat and no stowage (e.g. a connecting corridor) might be accepted as being an isolated compartment without a smoke/fire detection system, because of the low likelihood of a fire starting in such a compartment.

(c)      Minimum requirements for compartments

For all compartments, irrespective of whether or not they are required to have a smoke/fire detection system installed:

(i)       For accessibility and firefighting purposes, sufficient lighting in the compartment should be provided. For compartments that could be dark during flight, a means should be provided to enable a person entering the compartment to readily gain visibility of the interior. Such means may be:

(A)     a conveniently located, easy to find and use lighting control for the compartment;

(B)     a flashlight within close proximity to the entrance of the compartment; or

(C)     automatic illumination in the event the smoke/fire detection system in the compartment (if installed) triggers.

(ii)      At least one readily accessible handheld fire extinguisher should be available for use in each compartment. Fire extinguishers required by CS 25.851(a) may be used for this purpose. On the other hand this may also lead to the need to install more fire extinguishers than the minimum required by CS 25.851(a).

(iii)     Portable breathing equipment, required by CS 25.1439(a), should be located close to the handheld fire extinguisher.

(b)      Smoke/fire detection in isolated compartments

For interiors with more than one isolated compartment, there should be means by which flight or cabin crew can readily identify in which compartment smoke/fire has been detected. Depending on the number of isolated compartments and the specific layout, such means might be simply moving through the cabin and checking each compartment (in the case that cabin crew are required to be on board) or might need to be a visual indication outside each compartment, or some form of annunciator panel available to an appropriate crew member. The objective in any case is that correct identification of the location of the smoke/fire should be possible without unnecessary delay.

If the isolated compartment incorporates a stowage compartment of a volume greater than 0.7 m3 (25 ft3), this stowage compartment should be itself equipped with a smoke detector, unless it can be demonstrated that smoke from within the stowage compartment will be detected by the detector of the isolated compartment in which the stowage compartment is located (e.g. through grilles in the stowage door), and within the time specified in the requirement S25.10(c).

If the isolated compartment incorporates a galley, or if smoking is to be allowed in the isolated compartment, nuisance triggering of the smoke/fire detection system may be minimised by a design feature that provides for temporary system deactivation by an occupant (passenger or crew member). In that case, full reactivation should be automatic after a time period of no longer than 10 minutes following the last deactivation action.

The effectiveness of the smoke/fire detection system should be demonstrated for all approved operating configurations and conditions. For smoke detection demonstration, FAA AC 25-9A, Smoke detection, penetration, and evacuation tests and related flight manual emergency procedures, 6 January 1994 provides acceptable means of compliance.

During testing, it should be demonstrated that no inadvertent operation of smoke/fire detectors in any compartment would occur as a result of fire starting in any other compartment.

An assessment of the compartment design and observations during smoke/fire detection tests will be expected in order to provide a demonstration of the effectiveness of firefighting procedures. This should also include demonstrating that the compartment is provided with sufficient access in flight to enable a crew member to effectively reach any part with the contents of a handheld fire extinguisher.

[Amdt 25/19]