AMC to Appendix S, S25.10(d) and (e) Deactivation of existing Emergency Exits

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ED Decision 2017/015/R

(1) General

S25.10(d)(3) requires to ensure that the distance from each passenger seat to at least one non-deactivated emergency exit on each side of the fuselage remains compatible with easy egress from the aeroplane.

For the purpose of this provision, a passenger seat distribution will be considered to meet this objective, provided that each passenger seat approved for use during taxiing, take-off, or landing is located such that:

(a) It is within 9.14 m (30 ft) from the nearest emergency exit on one side of the fuselage on the same deck, and within 13.72 m (45 ft) from the nearest emergency exit on the other side of the fuselage on the same deck; and

(b) The occupant of that seat has the possibility to move to an emergency exit, on the left side, or the right side of the fuselage, whilst at all points along the way remaining within 9.14 m (30 ft) from an emergency exit on one side of the fuselage on the same deck and within 13.72 m (45 ft) from an emergency exit on the other side of the fuselage on the same deck.

When calculating the distance from a passenger seat, or from any point in the egress path of an occupant, to an emergency exit, this distance should be taken as the total longitudinal distance (i.e. as measured parallel to the aeroplane’s longitudinal axis) that the escapee should cover in order to get to the emergency exit in question (i.e. the distance calculated should take into account all required changes in the direction of movement but measured only longitudinally). For the distance from a passenger seat, as starting point, the front edge of the seat bottom cushion at the seat centreline is to be taken (for forward, angled, side or aft-facing seats), and as end point, the nearest exit edge.

For aeroplanes with an approved passenger seating configuration of 19 or less, only one pair of emergency exits is required. However, such aeroplanes may have additional exits installed, which must then comply with CS 25.807(h) but not with the 18.3-m (60-feet) rule of CS 25.807(f)(4). The distance between each passenger seat and the nearest available emergency exit may be determined considering all available emergency exits, including the ones addressed by CS 25.807(h).

When deactivation of one or more emergency exits results in an emergency exit arrangement that is asymmetrical relative to the aeroplane centre line, the acceptable seating capacity for each cabin zone should be determined considering the emergency exits remaining available on each side of the fuselage separately, i.e. following a similar methodology as the one used in FAA AC 25.807-1, Uniform distribution of exits, 13 August 1990.

(2) Examples

The following examples illustrate the analysis method to be followed when examining the acceptability of various emergency exit deactivation schemes on an aeroplane that is originally type-certified with two pairs of Type C exits (rated at 55 passengers for each pair) at the forward and aft limits of the cabin, and a single pair of overwing Type III exits (rated at 35 passengers). In accordance with CS 25.807, this emergency exit layout will have a possible maximum approved passenger capacity of 145 (55 + 35 + 55). It is assumed that the aeroplane manufacturer has received approval for this number of passengers.

The distance between the nearest exit edges of the two pairs of Type C exits is 20 m (65.7 ft). The overwing exits pair’s forward edges are 8 m (26.3 ft) from the rear edges of the forward Type C exit pair.

The figures below provide additional clarification on the methodology to be used and the resultant limitations.

A cabin area that should not include any crew or passenger seats that can be occupied during taxiing, take-off, and landing is referred to as a ‘stay-out zone’, coloured pink in the illustrations below. The hatched/yellow areas in the illustrations below are referred to as ‘additional stay-out zones’ and should also not include any crew or passenger seats that can be occupied during taxiing, take-off, and landing. Seats located within these latter zones do meet the criteria of the above paragraph (1)(a) but do not meet the criteria of the above paragraph (1)(b). In other words, although these zones are located sufficiently close to emergency exits to meet the basic emergency exit egress distance requirements on both sides of the fuselage, an occupant of one of these seats would be forced to traverse a cabin area that does not meet these requirements, i.e. a stay-out zone, in order to egress the aeroplane.

Example 1

In the first example, only the left hand (LH) overwing Type III exit is deactivated.

Identification of stay-out zones

No stay-out zone needs to be identified in the cabin, if any possible passenger seat location will be no more than 9.14 m (30 ft) from the nearest exit on one side of thefuselage, and no more than 13.72 m (45 ft) from the nearest exit on the other side of the fuselage, i.e. in compliance with the above paragraph 1.(i).

Calculation of the basic passenger seating configuration limitations set by S25.1(a).

In the case of non-commercial operations, in accordance with S25.1(a), the passenger capacity will have an upper possible limit of 73 passengers (1/2 of 145 (55 + 35 + 55) rounded up), i.e. one half of the maximum passenger seating capacity of the type-certified aeroplane having all exits functional.

In the case of commercial operations, in accordance with S25.1(a), the passenger capacity will have an upper possible limit of 48 passengers (1/3 of 145 (55 + 35 + 55) rounded down), i.e. one third of the maximum passenger seating capacity of the type-certified aeroplane having all exits functional. Additionally, there will be an upper possible limit of 30 passengers seated forward or aft of the overwing exits (1/3 of 90 (55 + 35)), i.e. one third of the maximum passenger seating capacity for each cabin zone of the type-certified aeroplane having all exits functional.

Calculation of additional passenger seating limitations due to exit deactivation

Firstly, a zonal analysis is conducted on the right side of the fuselage in accordance with S25.10(d). Two zones are represented by the exits on this side (all original emergency exits remain functional).

The allowable number of seats between the forward Type C exit and the overwing exit is limited to one half of the sum of the ratings of the exits that bound the zone: 1/2 of 90 (55 + 35) = 45.

The same limit is valid also for the zone between the overwing exit and the rearmost Type C exit.

Secondly, a zonal analysis is conducted on the left side of the fuselage in accordance with S25.10(d). There is only one zone represented by the remaining functional exits on this side. The allowable number of passenger seats between the forward and aft Type C exits is again limited to one half of the sum of the exit ratings that bound the zone: 1/2 of 110 (55 + 55) = 55.

The passenger seating locations for taxiing, take-off, and landing should simultaneously satisfy all basic limitations set by S25.1(a) and both of the zonal analyses in accordance with S25.10(d).

In the case of non-commercial operations, this means that the passenger seating configuration is limited to 55 (i.e. in this case, the limitation resulting from the left-side fuselage zonal analysis is most constraining and defines the maximum seating capacity of the aeroplane) and a maximum of 45 passenger seats located either forward or aft of the remaining functional overwing exit may be occupied for taxiing, take-off, and landing.

However, for commercial operations, an overriding consideration applies due to the fact that there is a non-compliance with CS 25.807(f)(4) on the left side of the fuselage, andthe provisions of S25.10(d) only apply to non-commercial operations. The seating capacity of the example aeroplane in commercial operation will thus be limited to 19 seats because CS 25.807(f)(4) only applies to aeroplanes for which more than one exit pair is required. However, there will be no limitation on the passenger seating location for taxiing, take-off, and landing, as explained in AMC 25.807.

Example 2

In the second example, both left hand (LH) and right hand (RH) overwing Type III exits are deactivated. The aeroplane has thus only two pairs of remaining functional Type C exits located at either end of the cabin.

Identification of stay-out zones

A stay-out zone is identified in the middle of the cabin, where a passenger seat that can be occupied during taxiing, take-off, and landing would not be in compliance with the above paragraph 1.(i), i.e. would be further than 9.14 m (30 ft) from the nearest exit, on both sides of the fuselage. The exact limitation on the seat installation location in order to respect the stay-out zone should be calculated using the longitudinal measurement method as explained in AMC 25.807.

Calculation of the basic passenger seating configuration limitation set by S25.1(a)

In the case of commercial operations, in accordance with S25.1(a), the passenger capacity will have an upper possible limit of 48 passengers (1/3 of 145 (55 + 35 + 55) rounded down), i.e. one third of the maximum passenger seating capacity of the type-certified aeroplane having all exits functional. Additionally, there will be an upper possible limit of 30 passengers seated forward or aft of the overwing exits (1/3 of 90 (55+35)), i.e. one third of the maximum passenger seating capacity for each cabin zone of the type-certified aeroplane having all exits functional.

Calculation of additional passenger seating limitations due to exit deactivation

In this example, the arrangement of the remaining functional exit is symmetrical on either side of the aeroplane centre line, hence, no separate LH and RH zonal analyses are required, and only one cabin zone remains.

The zonal analysis, in accordance with S25.10(d), results in the number of seats that may be occupied during taxiing, take-off, and landing between the forward and aft Type C exits, limited to one half of the sum of the ratings of the exits that bound the zone: i.e. 1/2 of 110 (55 + 55) = 55.

The passenger seating locations for taxiing, take-off, and landing should simultaneously satisfy all basic limitations set by S25.1(a) and the zonal analysis in accordance with S25.10(d). Therefore, for non-commercial operations, a maximum total of 55 passenger seats may be occupied during taxiing, take-off, and landing, in any combination of individual locations forward or aft of the identified stay-out zone.

For commercial operations, as in Example 1, the seating capacity of the aeroplane will be limited to 19, due to non-compliance with CS 25.807(f)(4), on both sides of the fuselage this time. However, as also explained in Example 1, the total of 19 passenger seats that can be occupied during taxiing, take-off, and landing may be in any combination of locations forward or aft of the identified stay-out zone.

Example 3

In the third example, the rearmost LH Type C exit is deactivated. The aeroplane has, thus, one pair of functional forward Type C emergency exits and one pair of functional overwing Type III emergency exits, and a functional aft Type C emergency exit on the RH side only.

Identification of stay-out zones

No stay-out zone can be identified in the cabin, i.e. any possible passenger seat location will be no more than 9.14 m (30 ft) from the nearest exit on one side of the fuselage, and no more than 13.72 m (45 ft) from the nearest exit on the other side of the fuselage.

Calculation of the basic passenger seating configuration limitations set by S25.1(a)

In the case of non-commercial operation, in accordance with S25.1(a), the passenger capacity will be limited to 73 passengers (1/2 of 145 (55+35+55) rounded up), i.e. one half the maximum passenger seating capacity of the type certified aeroplane with all exits functional.

In the case of commercial operation, in accordance with S25.1(a), the passenger capacity will have an upper possible limit of 48 passengers (1/3 of 145 (55+35+55) rounded down), i.e. one third the maximum passenger seating capacity of the type certified aeroplane with all exits functional. Additionally, there will be an upper possible limit of 30 passengers seated forward or aft of the overwing exits (1/3 of 90 (55+35)), i.e. one third of the maximum passenger seating capacity for each cabin zone of the type certified aeroplane with all exits functional.

Calculation of additional passenger seating limitations due to exit deactivation

Firstly, a zonal analysis is conducted on the right side of the fuselage, in accordance with S25.10(d). Two zones are represented by the remaining functional exits on this side (all original emergency exits remain functional).

The allowable number of seats for installation between the forward Type C and the overwing exit is limited to one half of the sum of the ratings of the exits that bound the zone: 1/2 of 90 (55 + 35) = 45.

The same limit is also valid for the zone between the overwing emergency exit and the rearmost Type C exit. Secondly, a zonal analysis is conducted on the left side of the fuselage. Again, two zones are represented by the remaining functional emergency exits on this side, but this time, one zone is a so-called dead end zone.

As for the right side, it is acceptable to install 45 seats between the forward Type C and the overwing exit: 1/2 of 90 (55 + 35) = 45.

In the dead end zone aft of the overwing exit, it is acceptable to install a maximum of 18 seats (1/2 of 35 rounded up).

The passenger seating locations for taxiing, take-off, and landing should simultaneously satisfy all basic limitations set by S25.1(a) and both of the zonal analyses in accordance with S25.10(d).

Therefore, for non-commercial operations, this results in a maximum total seating capacity of 63 when it simultaneously satisfies the upper limit for each zone, i.e. 45 for the forward zone and 18 for the aft zone.

In case of commercial operations, the total capacity of the aeroplane will be limited to 48 passengers, not exceeding 30 passengers forward of and 18 aft of the overwing exits.

Further examples

In addition to Examples 1, 2 and 3 above, further examples of exit deactivation for the same basic aeroplane are illustrated, and the resultant allowable passenger seating restrictions are summarised.

The principles evident from these examples can be used to determine zonal capacities and stay-out zones for any aeroplane.