Date: July 7, 2011
To: Manager, Seattle ACO, ANM-100S
From: Manager, Transport Airplane Directorate, ANM-100
Prepared by: Ana Martinez Hueto, ANM-150S
Subject: INFORMATION: Equivalent Level of Safety (ELOS) Finding for Door
Arrangement for Heath Tecna Inc. Project on a Model 747-400, FAA Project
ELOS Memo#: ST11011SE-T-C-2
Regulatory Ref: ?? 25.807(a)(2), (a)(7)(iv) & (vii), (b), (c)(1), 25.809, and 25.813(a) & (b)
This memorandum informs the certificate management aircraft certification office of an evaluation made by the Transport Airplane Directorate (TAD) on the establishment of an equivalent level of safety (ELOS) finding for the Boeing Model 747-400 airplane.
On January 18, 2011 Heath Tecna, Inc. (HT) located in Bellingham, Washington applied to the Federal Aviation Administration (FAA) to install a revised passenger seating arrangement on a Model 747-400 aircraft. The change installs business class seats on the upper deck of the airplane. The center pedestal of the cabin seat unit located immediately aft of the left hand upper deck Type A exit encroaches 15 inches into the projected opening. The pair of exits installed in the upper deck are nominally rated as Type A exits. Because of the restricted access to one of the exits due to the center pedestal, which does not comply with the requirements for Type A exits, HT proposes to re-rate the exit to a Type II exit.
?? 25.807(a)(2), (a)(7)(iv) & (vii), (b), (c)(1), 25.809, and 25.813(a) & (b)
Regulation(s) requiring an ELOS finding
?? 25.807(a)(2), (b), (c)(1) and 25.813(a) and (b)
Description of compensating design features or alternative standards which allow the granting of the ELOS (including design changes, limitations or equipment need for equivalency)
; The installation provides an unobstructed 24 inch wide passageway within the 42 inch
wide projected exit opening.
; An assist space is provided to one side of the exit doorway that does not reduce the
unobstructed width of the passageway.
; Only the cabin seating unit center pedestal may encroach no more than 15.25 inches into
the projected exit opening
; Seat back breakover is restricted so there is no encroachment into the 24 inch
passageway or assist space.
; The exit operating handle and the exit signs are visible from the aisle.
; The dual lane escape slides remained installed at the upper deck doors.
; Passenger capacity is limited to twenty.
Explanation of how design features or alternative standards provide an equivalent level of safety to the level of safety intended by the regulation
Title 14, Code of Federal Regulation (CFR) 25.807(a)(2), Amendment 25-55, states that Type II exits must have a rectangular opening of not less than 20 inches wide by 44 inches high, with corner radii not greater than one-third the width of the exit. Type II exits must be floor level exits unless located over the wing, in which case they may not have a step-up inside the airplane of more than 10 inches nor a step-down outside the airplane of more than 17 inches.
; The upper deck exit doors of the Model 747-400 are 42 inches wide by 72 inches high.
The Type II exit doorway can be inscribed within the unobstructed opening provided.
Section 25.807(b) states that “Each required passenger emergency exit must be accessible to the
passengers and located where it will afford the most effective means of passenger evacuation. Openings larger than those specified in this section, whether or not of rectangular shape, may be used if—
(1) The specified rectangular opening can be inscribed within the opening; and (2) The base of the inscribed rectangular opening meets the specified step-up and step-down heights.”
; The Type II exit is located approximately mid cabin with 8 passenger places located
forward of the exit and 12 passenger places located aft of the exit. The exit directly across
is a Type A exit. Additionally, the straight segment stairway between the main and upper
deck is located aft of all passenger places on the upper deck.
; The Type II exit doorway can be inscribed within the unobstructed opening provided.
; The existing upper deck doors are floor level.
Section 25.807(c)(1) states, in part:
For a passenger seating configuration (crewmember seats not included) of 20 through 39 one Type II and one Type III emergency exit are required for each side of the fuselage.
; Special Condition No. 25-71-NW-3 provided authorization for an upper deck seating
configuration of 45 passenger places with an upper deck door configuration of one Type I
emergency exit for each side of the fuselage and a stairway between decks. Based on the
criteria above in ? 25.807(c)(1), it is clear that for a configuration of between 40 and 45
passengers, the type certified stairway between decks is considered to have an evacuation
rate equal to one Type III emergency exit per side.
; A Type A exit on each side of the fuselage allows for 110 passenger seating
configuration and a Type II exit on each side of the fuselage allows for 20 to 39
passenger seating configuration. The resulting configuration for the upper deck is a Type
II exit on the left hand side of the fuselage and a Type A for the right hand side of the
fuselage. Counting the aft stairway between decks as being equivalent to having one
Type III exit per side of the fuselage, and providing one Type II exit on the left hand side
of the fuselage and a Type A for the right hand side of the fuselage, the proposed
configuration provides an equivalent level of safety for the upper deck seating
configuration of 20 passengers as that intended under ? 25.807(c)(1).
Section 25.813(a) at Amendment 25-46 states that the passageway leading from each aisle to each Type II emergency exit “must be unobstructed and at least 20 inches wide.”
; The configuration provides a 24 inch wide unobstructed passageway leading from the
main aisle directly to the exit.
; Encroachment of the center pedestal into the upper deck exit projected opening is
mitigated by the presence of a flight attendant located at the floor level exit.
Section 25.813(b) states that “there must be enough space next to the exit to allow a crewmember to assist in the evacuation of passengers without reducing the unobstructed width of the passageway below that required for the exit.”
; The assist space has been provided at the aft side of the exit and does not reduce the
unobstructed passageway width. The design as presented does fulfill the criteria
established in the regulation.
FAA approval and documentation of the ELOS finding
The FAA has approved the aforementioned ELOS finding in project Issue Paper C-2. This memorandum provides standardized documentation of the ELOS finding that is non-proprietary and can be made available to the public. The TAD has assigned a unique ELOS memorandum number (see front page) to facilitate archiving and retrieval of this ELOS. This ELOS memorandum number should be listed in the Limitations and Conditions Section of the STC Certificate. An example of an appropriate statement is provided below.
Equivalent Level of Safety Findings have been made for the following regulation(s):
?? 25.807(a)(2), (b), (c)(1) and 25.813(a) and (b) Emergency exits and Emergency exit access (documented in TAD ELOS Memo ST11011SE-T-C-2)]
Original Signed by
July 13, 2011 Jeff Gardlin
Transport Airplane Directorate, Date
Aircraft Certification Service
ELOS Originated by Project Engineer Routing Symbol
SACO: Ana Martinez Hueto ANM-150S