AMC 27.807(d) Underwater emergency exits for passengers

ED Decision 2018/007/R

This AMC replaces FAA AC 27.807, AC 27.807A and AC 27.807B.

(a)     Explanation

CS-27 Amendment 5 re-evaluates the need for and the concept behind emergency exits for rotorcraft approved with ditching provisions. Prior to CS-27 Amendment 5, there were no additional ditching provisions for rotorcraft certified for ditching with regard to the number of emergency exits.

Operational experience has shown that in a ditching in which the rotorcraft remains upright, use of the passenger doors can be very beneficial in ensuring a rapid and orderly evacuation onto the life raft(s). However, when a rotorcraft capsizes, doors may be unusable and the number and availability of emergency exits that can be readily used underwater will be crucial to ensuring that passengers are able to escape in a timely manner. Experience has shown that the number of emergency exits required in the past by design requirements has been inadequate in a capsized situation, and a common design solution has been to use the passenger cabin windows as additional emergency egress means by including a jettison feature. The jettison feature has commonly been provided by modifying the elastomeric window seal such that its retention strength is either reduced, or can be reduced by providing a removable part of its cross section, i.e. the so called ‘push out’ window, although other design solutions have been employed. The provision of openable windows has been required by some air operations regulations.

In recognition of this identified need for an increased number of exits for underwater escape, Amendment 5 created a new set of exit terminology and CS 27.807(d)(1) was revised to require one pair of ‘underwater emergency exits’, i.e. one on each side of the rotorcraft, to be provided for each unit, or part of a unit, of four passenger seats, and passenger seats to be located relative to these exits in a way to best facilitate escape. This new terminology was seen as describing the real intent of this higher number of required emergency exits for rotorcraft approved with ditching provisions.

The objective is for no passenger to be in a worse position than the second person to egress through an exit. The size of each underwater emergency exit should at least meet the dimensional provisions of CS 27.807(b)(1), i.e. it should provide an unobstructed opening through which a 0.48 m x 0.66 m (19 in. x 26 in.) elliptical object could pass.

This provision is based on the need to facilitate egress in the case of a capsize that occurs soon after the rotorcraft has alighted on the water or in the event of a survivable water impact in which the cabin will likely be immediately flooded. The time available for evacuation is very short in such situations, and therefore, CS-27 Amendment 5 has increased the safety level by mandating additional exits, in the form of underwater emergency exits, to both shorten available escape routes and to ensure that no occupant should need to wait for more than one other person to escape before being able to make their own escape. The provision of an underwater emergency exit in each side of the fuselage for each unit (or part of a unit) of four passenger seats will make this possible, provided that seats are positioned relative to the exits in a favourable manner.

Critical evacuation factors are the distance to an underwater emergency exit and how direct and obvious the exit route is, taking into account that the passengers are likely to be disoriented.

So called ‘push-out’ windows (see above) have some advantages in that they are not susceptible to jamming and may open by themselves in a water impact due to flexing of the fuselage upon water entry and/or external water pressure.

The risk of a capsize during evacuation onto the life rafts can be mitigated to some extent by instructing passengers to open all the underwater emergency exits as a matter of course soon after the helicopter has alighted on the water, thus avoiding the delay due to opening the exits in the event that the exits are needed. Such advice should be considered for inclusion in the documentation provided to the helicopter operator.

(b)     Procedures

(1)     The number and the size of underwater emergency exits should be as specified above.

(2)      Care should be taken regarding oversized exits to avoid them becoming blocked if more than one passenger attempts to use the same exit simultaneously.

(3)      A higher seat-to-exit ratio may be accepted if the exits are large enough to allow the simultaneous escape of more than one passenger. For example, a pair of exits may be approved for eight passengers if the size of each exit provides an unobstructed area that encompasses two ellipses of 0.48 m x 0.66 m (19 in. x 26 in.) side by side.

(4)      Test, demonstration, compliance inspection, or analysis is required to substantiate that an exit is free from interference from stowed or deployed emergency flotation devices. In the event that an analysis or inspection is insufficient or that a given design is questionable, a test or demonstration may be required. Such a test or demonstration would consist of an accurate, full-size replica (or true representation) of the rotorcraft and flotation devices, both when stowed and after their deployment.

(5)      Consideration should be given to reducing the potential confusion caused by the lack of standardisation of the location of the operating devices (pull tab, handle) for underwater emergency exits. For example, the operating device should be located next to the handhold (see (10) below). The occupant then has only to find the handhold to locate the operating device. Each adjacent occupant should be able to reach the handhold and operating device whilst seated, with restraints fastened, with seat energy absorption features at any design position, and with the rotorcraft in any attitude. If a single underwater emergency exit is designed for the simultaneous egress of two occupants side by side, a handhold and an operating device should be within reach of each occupant seated adjacent to the exit.

(6)      Underwater emergency exits should be shown to be operable with the rotorcraft in any foreseeable attitude, including with the rotorcraft capsized.

(7)     Underwater emergency exits should be designed so that they are optimised for use with the rotorcraft capsized. For example, the handhold(s) should be located close to the bottom of the window (top if inverted) to assist an occupant in overcoming the buoyancy loads of an immersion suit, and by ensuring that markings and lighting will help identify the exit(s) and readily assist in an escape.

(8)     The means to open an underwater emergency exit should be simple and obvious and should not require any exceptional effort. Designs with any of the following characteristics (non-exhaustive list) are considered to be non-compliant:

(i)      More than one hand is needed to operate the exit itself (use of the handhold may occupy the other hand);

(ii)      Any part of the opening means, e.g. an operating handle or control, is located remotely from the exit such that it would be outside of a person’s direct vision when looking directly at the exit, or that the person needs to move away from the immediate vicinity of the exit in order to reach it; and

(iii)     The exit does not meet the opening effort limitations set by FAA AC 29.809.

(9)      It should be possible to readily grasp and operate any operating handle or control using either a bare or a gloved hand.

(10)    Handholds, as required by CS 27.807(d)(3), should be mounted close to the bottom of each underwater emergency exit such that they fall easily to hand for a normally seated occupant. In the case of exits between face-to-face seating, the provision of two handholds is required. Handholds should be designed such that the risk is low of escapees’ clothing or emergency equipment snagging on them.

(11)    To make it easier to recognise underwater, the operating device for the underwater emergency exit should have black and yellow markings with at least two bands of each colour of approximately equal widths. Any other operating features, e.g. highlighted ‘push here’ decal(s) for openable windows, should also incorporate black-and-yellow-striped markings.

(12)    With regard to the location of seats relative to the exits, the most obvious layout that maximises achievement of the objective that no passenger is in a worse position than the second person to egress through an exit is a four-abreast arrangement with all the seats in each row located appropriately and directly next to the emergency exits. However, this might not be possible in all rotorcraft designs due to issues such as limited cabin width, the need to locate seats such as to accommodate normal boarding and egress, and the installation of items other than seats in the cabin. Notwithstanding this, an egress route necessitating movement such as along an aisle, around a cabin item, or in any way other than directly towards the nearest emergency exit, to escape the rotorcraft is not considered to be compliant with CS 27.807(d)(1).

[Amdt No: 27/5]