AMC 25.813(c) Emergency Exit Access and Ease of Operation

ED Decision 2017/015/R

1       Post crash seat deformation

The requirement for an “unobstructed” passageway is not intended to preclude some deformation of seat structure into the required minimum passageway dimension due to emergency landing dynamic loading.

Seat permanent deformation of up to 3 inches (as recorded in the tests required by CS 25.562) into the minimum passageway dimensions defined in CS 25.813(c) is acceptable, provided no part of the seat intrudes into the minimum required projected opening of the exit and provided the exit operating characteristics are not compromised. Relevant parts of FAA Advisory Circular 25.562-1B provide further details.

2        Deployable features

Features mounted on seats, bulkheads or other cabin features, under passenger control and which deploy into the required minimum passageway, may be accepted as not contravening the “unobstructed passageway” requirements of CS 25.813(c) provided they are easily and instinctively pushed out of the passageway by escapees in the event that they remain deployed prior to, or become deployed during, an evacuation. This may include, but not be limited to, items such as handsets, tray tables, in-armrest video monitors. Items such as footrests which would not be within easy reach of escapees’ hands and/or not easily visible during an evacuation will not be accepted as being easily and instinctively re-stowed.

Such designs will be assessed on their individual merits.

It must be noted that none of the above reduces the requirement to design latching means that will prevent inadvertent release by evacuating passengers. A “Lock out device” will not be acceptable as part of a means of compliance to the minimum unobstructed passageway dimensions. “Lock out device” means a mechanism actuated by a cabin crew member to prevent passengers deploying items into an access passageway during taxi, take-off and landing.

Features (e.g. seat recline, footrests, video screens, tables) may still be unsafe, even if they do not deploy into a defined minimum 15.2, 25.4 or 33 cm (6, 10 or 13 inches) passageway (as applicable). Deployable items may create snagging/tripping hazards and in the case where a wider passageway than the minimum is provided, it cannot be assumed that escaping passengers will constrain themselves to passing along one side or the centre. Features which deploy into the actual passageway provided (in vertical projection from floor level to the upper ceiling/over head bin constraint) will be assessed in the same way as if they deployed into the minimum passageway, i.e. they can be accepted if they can be easily and instinctively pushed out of the passageway as described above.

3       Automatic disposal of hatch/door

The intent, in CS 25.813(c)(6), of requiring “automatic” disposal of a Type III hatch/door on aeroplanes with passenger seating configurations of 41 or more is to remove the risk of passenger confusion, difficulty or error once the opening handle movement has been initiated.

In this context, “automatic” is intended to convey the requirement that this type of Type III exit should be by its design as simple, instinctive and easy to operate as any other type of exit.

Markings, controls and kinematics of the design should be so that with minimal instruction (i.e. from a study of the placards required by CS 25.813(c)(5) a naïve subject, with the ranges of size and strength found in the 5^th percentile female to the 95^th percentile male, would be expected to be able to swiftly and correctly operate the exit to its fully open and secured position.

In this regard, the exit hatch/door should move from its closed to fully open position in one simple and continuous operator motion, e.g. avoiding discontinuities in required force/direction on the handle(s). The traditional practice of providing a removable hatch will not be accepted as meeting the requirements of CS 25.813(c)(6).

It is to be noted that the requirements of CS 25.809, which defines emergency exit operating characteristics, testing requirements, etc. are applicable to all exit types, including Type III and IV.

4       Very large exit access provision

In most cases it is expected that the cabin arrangement adjacent to a Type III or IV exit will be such that access provision and unobstructed space for operation will be towards the minimum dimensions required. However, this might not always be the case.

Some of the testing performed to substantiate the required dimensions has revealed that competition between escaping passengers can reduce a Type III exit’s evacuation performance in cases where a large unobstructed passageway or adjacent area is provided.

Dependent on the details of a specific cabin layout, additional substantiation may therefore be necessary for a design providing a substantially larger passageway and/or clear area adjacent to the exit than the minimum required. This will also apply to Type IV exits.

5       “De-rated” and “oversized” exits

Two cases can be identified where some additional considerations may be needed when considering the provisions of CS 25.813(c)(4)(i), namely:

a.       A larger exit type (e.g. Type II, I) which is declared as a Type III in order to, for instance, place a seat partially overlapping the exit opening (i.e. “de-rating” the exit).

b.       The exit opening provided by the design is larger than the minimum required (i.e. an “oversize exit”).

In such cases it may be acceptable that the exit opening provided is partially obstructed, at all times or perhaps when certain features are deployed, if the remaining exit aperture still provides the intended egress performance.

Each such case will be assessed on its own individual merits and, if accepted, would be so on the basis of Equivalent Safety.

6       Provisions to prevent escapees bypassing the intended evacuation route

CS 25.813(c)(7)(i) is intended to prevent cabin installations which would permit escaping passengers bypassing the intended evacuation route to the exit by climbing over seat backs or any other feature that may bound the required access passageway.

In the case of seat backs, the surface over which an escapee may attempt to climb should remain essentially upright, i.e. not exceeding 20 degrees rearward and 10 degrees forward relative to a plane normal to the cabin floor, when a load of up to 668 N (150 lbf) is applied horizontally in a fore/aft direction at the structurally most critical point.

In the case of features other than seat backs, the obstacle to climbing over should be assessed with the aim that it be comparable to the seat back example above, i.e. the angle and height of the item/surface in question.

7       Placards

The placards required by CS 25.813(c)(5) must accurately illustrate the proper method of opening the exit. This will require different “handed” placards for installation on the left and right sides of the cabin. Precautions should be taken to minimise the risk of a placard being installed on the incorrect side of the cabin.

The particular method illustrated on a placard, e.g. placement of body, hands etc. should be substantiated as being that most likely to result in successful operation.

8.       Entrapment

The seat design should be free of any gaps into which it would be possible to place a foot, hand or arm in such a way as to delay or hamper free movement of passengers to the exit. Any opening/gap that is assessed as being positioned such that it poses a risk and which is more than 2.54 cm (one inch) in width will need to be the subject of particular scrutiny before being found acceptable.

9        Minor obstructions

An item may be acceptable as meeting the intent of a minor obstruction in accordance with CS 25.813(c)(4)(ii) provided that, as soon as an occupant begins to open the emergency exit using only the required and visible operating handle, the obstruction moves such that the occupant instinctively understands how to complete removal of the obstructive item. Examples of such items are unattached (or loosely attached) soft seat back cushions on side-facing divans, provided that the cushion may be readily moved away and the emergency exit then easily fully opened. Ease of opening from the outside should also be assessed with the minor obstruction in place. Neither the emergency exit sign nor the operating handle should be obscured at any point.

[Amdt 25/9]

[Amdt 25/19]