[Federal Register Volume 59, Number 176 (Tuesday, September 13, 1994)]
[Unknown Section]
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From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-22620]
[[Page Unknown]]
[Federal Register: September 13, 1994]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 25
[Docket No. NM-53; Notice No. SC-94-3-NM]
Special Conditions: Jetstream Aircraft Limited Model 4100 Series
Airplanes, Main Cabin Aisle Arrangement
AGENCY: Federal Aviation Administration, DOT.
ACTION: Notice of proposed special conditions.
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SUMMARY: This notice proposes to amend special conditions issued to
British Aerospace Public Limited Company (BAe) (Currently Jetstream
Aircraft Limited) for the BAe Model 4100 airplane. This airplane has a
novel or unusual design feature associated with the main cabin aisle
arrangement. Special Conditions No. 25-ANM-45 were issued on July 9,
1991, addressing this unusual arrangement, and included a limitation on
passenger capacity. The applicant has requested that the special
conditions be amended to increase the passenger capacity limit from 29
to 30 passengers. Since the special conditions were issued the
applicant has changed the company name and revised the model number of
the airplane. This amendment of the special conditions should also
reflect these changes. Since the applicable airworthiness regulations
do not contain adequate or appropriate safety standards for this
particular design feature, this notice contains the additional safety
standards which the Administrator finds necessary to establish a level
of safety equivalent to that established by the airworthiness standards
for transport category airplanes.
DATES: Comments must be received on or before October 3, 1994.
ADDRESSES: Comments on this proposal may be mailed in triplicate to:
Federal Aviation Administration, Transport Airplane Directorate (ANM-
100), Attn: Docket No. NM-53, 1601 Lind Avenue SW, Renton, Washington
98055-4056; or delivered in triplicate to the Transport Airplane
Directorate at the above address. Comments must be marked: Docket No.
NM-53. Comments may be inspected in the Rules Docket weekdays, except
Federal holidays, between 7:30 a.m. and 4:00 p.m.
FOR FURTHER INFORMATION CONTACT:
Jeff Gardlin, Regulations Branch, ANM-114, Transport Airplane
Directorate, Aircraft Certification Service, FAA, 1601 Lind Avenue SW.,
Renton, Washington 98055-4056; telephone (206) 227-2136.
SUPPLEMENTARY INFORMATION:
Comments Invited
Interested persons are invited to participate in the making of
these proposed special conditions by submitting such written data,
views, or arguments as they may desire. Communications should identify
the regulatory docket or notice number and be submitted in triplicate
to the address specified above. All communications received on or
before the closing date for comments will be considered by the
Administrator before taking action on this proposal. The proposal
contained in this notice may be changed in light of comments received.
All comments submitted will be available in the Rules Docket for
examination by interested persons, both before and after the closing
date for comments. A report summarizing each substantive public contact
with FAA personnel concerning this rulemaking will be filed in the
docket. Persons wishing the FAA to acknowledge receipt of their
comments submitted in response to this notice must submit with those
comments a self-addressed, stamped postcard on which the following
statement is made: ``Comments to Docket No. NM-53.'' The postcard will
be date/time stamped, and returned to the commentor.
Background
On May 24, 1989, BAe Public Limited Company (currently Jetstream
Aircraft Ltd.) applied for a type certificate for the BAe Model 4100
(currently Jetstream Model 4101) airplane in the transport airplane
category. The Model 4100 was to be a derivative of the Model 3100,
which is a small airplane and is certificated under the provisions of
part 23. Like the Model 3100, the Model 4100 was a low wing, twin
engine turbo-prop design. The fuselage was stretched, however, to seat
29 passengers in a three-abreast arrangement. Since the Model 4100
airplane had the same fuselage cross section as the Model 3100, it did
not have a traditional main cabin aisle arrangement.
Section 25.815 species the minimum aisle width dimensions for
transport category airplanes based on the passenger capacity. For
airplanes with 20 or more passenger seats, a minimum 15-inch width at
heights 25 inches or less above the main aisle floor and a minimum 20-
inch width at heights greater than 25 inches above the floor must be
maintained. Aisle width is measured at any point along the aisle,
normal to the centerline of the aisle. The main aisle envisioned by the
regulations would run in a straight line from one end of the passenger
cabin to the other and would satisfy these width criteria. Long
standing FAA policy has permitted slight deviation from a straight line
where there is a transition from one cabin section to another, or where
there are interior features which dictate that the aisle move
laterally. For example, from tourist class to first class there may be
a change from five-abreast seating to four-abreast seating which moves
the aisle centerline laterally. This has been accepted provided the
required widths are maintained at all heights normal to the path that
an individual would take. This type of offset normally occurs at one or
two points in a main cabin aisle. In addition, there is no offset
permitted in the aisle vertically; that is, the required 15-inch
dimension must lie completely below the projected 20-inch dimension at
all points along the aisle.
The Jetstream main cabin aisle arrangement utilizes an offset at
each seat row. The left and right seat assemblies are offset from one
another longitudinally such that the seatbacks are not opposite each
other across the aisle. This arrangement permits a 20-inch measurement
between seatbacks (at an angle to the airplane centerline) and the
required 15-inch dimension is maintained within the projected 20-inch
dimension vertically. Thus the ``required aisle'' is not a straight
line from one end of the cabin to the other, but a series of
alternating angular segments from seatback to seatback. Nonetheless,
there is a straight path along the cabin length, and the aisle floor
does not deviate from side to side at all. The projected aisle width
along this straight path reaches 20 inches at a height of 43 inches
above the floor, which is the typical seatback height for transport
airplanes. Another feature of the design includes the use of overwing
exits which are offset longitudinally, corresponding to the seat
positions on the left and right of the airplane.
In order to provide design standards for the novel and unusual
aisle configuration in the BAe Model 4100 airplanes, the FAA issued
Special Conditions No. 25-ANM-45 on July 9, 1991. The criteria used to
develop Special Conditions No. 25-ANM-45 utilized the existing
regulations, and made certain favorable design features in the Model
4100 mandatory. Special Conditions No. 25-ANM-45 are summarized as
follows:
a. There are no more than 29 passenger seats with no more than ten
seat rows on either side of the aisle;
b. The interior arrangement includes one pair of Type II and one
pair of Type III passenger emergency exits;
c. In addition to the requirements of Sec. 25.815, the projected
aisle width is at least 20 inches measured at a height of 43 inches
above the aisle floor;
d. The Type III exits and adjacent seat rows are offset
longitudinally such that persons approaching an exit from one end of
the cabin may use the exit without interfering with those approaching
the other exit from the other end of the cabin;
e. The location and part number of each passenger seat must be
defined by a drawing approved by the FAA or foreign civil airworthiness
authority. The seat arrangement may not be reconfigured without FAA
approval; and
f. An evacuation demonstration must be conducted to demonstrate the
efficacy of the aisle arrangement.
The content of the special conditions was based, in part, on the
maximum passenger capacity proposed by BAe. The specific limitation of
29 passenger seats was the maximum capacity requested by BAe, but the
FAA considered that the fact that this capacity was well below the
maximum that could be allowed for the installed exit combination was a
significant factor in acceptance of the aisle arrangement.
Subsequent to issuing the Special Conditions 25-ANM-45 and prior to
issuance of the Type Certificate for that project British Aerospace
Public Limited Company changed its name to Jetstream Aircraft Limited
and changed the model designation for the airplane from BAe Model 4100
to the Jetstream Model 4101. Type Certificate A41NM was issued to
Jetstream Aircraft Limited on April 9, 1993 for the Jetstream Model
4101 airplane. It is now anticipated that additional models of the 4100
series may be added to this Type Certificate in the future. In addition
to the Model 4101, Special Conditions No. 25-ANM-45 would be applicable
to any other Jetstream Model 4100 series airplanes that incorporate the
same novel or unusual aisle configuration.
Type Certification Basis
Under the provisions of Sec. 21.101, Jetstream must show that 30
passenger Model 4100 series airplanes comply with the regulations in
the type certification basis established for the 29 passenger Jetstream
Model 4101 airplane. The type certification basis for the Model 4101 is
as follows:
The certification basis for the Model 4101 is established in
accordance with Sec. 21.29, using the Joint Aviation Regulations (JAR)
as a reference point, with appropriate additional requirements
incorporated to provide an equivalent certification basis to the FAR
requirements for U.S. certification. British Aerospace and the Civil
Aviation Authorities (CAA)-UK elected to have the type certification
basis be the following:
--JAR 25 as amended through Change 12 dated May 10, 1988;
--JAR 25 Orange Paper Amendment 88-1 effective October 18, 1988;
--JAR 1, definitions as amended through Change 4 dated June 1, 1987;
and
--any additional part 25 paragraphs necessary to provide a composite
type certification basis equal to the required part 25 type
certification basis.
Based on Secs. 21.29 and 21.17 and the type certification
application date, the applicable U.S. type certification basis was
established as follows:
--Part 25 dated February 1, 1965, as amended by Amendments 25-1 through
25-66;
--any applicable special conditions issued;
--any applicable exemptions granted;
--any equivalent safety findings made;
--the fuel venting requirements of Special Federal Aviation Regulation
No. 27, including Amendments 27-1 through the latest amendment in
effect on the date the Model 4100 is type certificated, and
--Part 36, including Amendments 36-1 through the latest amendment in
effect on the date of TC.
If the Administrator finds that the applicable airworthiness
regulations (i.e., part 25 as amended) do not contain adequate or
appropriate safety standards for Jetstream Model 4100 series airplanes
because of a novel or unusual design feature, special conditions are
prescribed under the provisions of Sec. 21.16 to establish a level of
safety equivalent to that established in the regulations.
Special conditions, as appropriate, are issued in accordance with
Sec. 11.49 after public notice, as required by Secs. 11.28 and
11.29(b), and become part of the type certification basis in accordance
with Sec. 21.17(a)(2).
Special conditions are initially applicable to the model for which
they are issued. Should the type certificate for that model be amended
later to include any other model that incorporates the same novel or
unusual design feature, or should any other model already included on
the same type certificate be modified to incorporate the same novel or
unusual design feature, the special conditions would also apply to the
other model under the provisions of Sec. 21.101(a)(1).
Novel or Unusual Design Features
The 30 passenger seat version of the Jetstream Model 4100 series
airplanes incorporate(s) the same novel or unusual aisle configuration
as described above for the 29 seat version.
As in the case of the 29 seat version, the required main cabin
aisle widths would be established using measurements taken between
seatbacks, which form a path in angular segments. The aisle width
measured normal to the fuselage centerline above 25 inches from the
floor, would extend from the seat back to the opposite cabin sidewall.
Thus, while the required 15-inch dimension at cabin heights below 25
inches from the floor would be completely within the projected 20-inch
width vertically, the 20-inch position would not be centered over the
15-inch position (See Figure 1.)
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In establishing Special Conditions No. 25-ANM-45, the FAA carefully
evaluated the relevant design parameters of the BAe Model 4100 and
determined that the main aisle configuration is clearly not what was
envisioned by the regulations. The regulations do not specifically
prohibit the arrangement proposed; however, the policy in effect is
predicated on a largely straight aisle which has only one or two
lateral deviations; in other words, a traditional cabin arrangement.
Therefore, special conditions were developed to establish design
criteria which result in a level of safety equivalent to configurations
on which the regulations were based.
Jetstream has requested that the FAA amend Special Conditions No.
25-ANM-45 to allow a maximum passenger capacity of 30, to account for a
new customer demand, and be responsive to the market. In their request
Jetstream contends that there is no technical basis for the limitation
on passenger capacity, and that the Joint Aviation Authorities (JAA)
have, in fact, already granted such approval. Jetstream has proposed
that on the basis of harmonization with the JAA, the FAA should
consider their request favorably.
Jetstream further contends that the evacuation demonstration
conducted in accordance with the special conditions for the 29
passenger Model 4101 illustrated that there is no impediment due to the
aisle arrangement for 30 passengers. Jetstream argues that the concern
that prompted the requirement was therefore demonstrated not to exist.
In developing the special conditions, the FAA took account of the
several favorable cabin safety features that the 29 passenger Model
4101 incorporates. One of the major features was the good exit-to-
passenger ratio for the number of passengers requested. That is, one
pair of Type II exits and one pair of Type III exits for 29 passenger
seats, where the regulations allow up to 39. In this regard, 29
passenger seats was the largest arrangement proposed for a US customer.
Consequently, the FAA did not consider a greater passenger capacity,
and the issue of harmonization did not come up.
With respect to the evacuation demonstration conducted in
accordance with the special conditions, this demonstration was a
modified version of the demonstration specified in part 25, Appendix J.
The principal modification was the use of a single exit (in this case,
the forward Type I exit) instead of one half of the total number of
exits installed. The demonstration was conducted this way in order to
provide for maximum usage of the aisle, by the maximum number of
passengers. While this demonstration was completed in 54 seconds, the
resultant overall rates of egress were not particularly fast for this
type of exit. In addition, the evacuees appeared to steady themselves
on seatbacks to a higher degree than is typically seen in such
demonstrations. Thus, while there was no clear obstruction due to the
aisle, the overall egress rates did seem to be somewhat reduced. The
FAA therefore considers that the aisle arrangement should result in a
limit on maximum passenger capacity that is reduced over the
theoretical limit in the regulations.
Jetstream has requested that the FAA increase the current limit,
which they believe is arbitrary, and allow up to 30 passengers in
accordance with same special conditions. As noted by the applicant the
demonstration conducted for approval of the 29 passenger version Model
4101 did include 30 occupants in the passenger cabin (to account for
the JAA approved arrangement) and was completed well within the
allowable time. Therefore, from the standpoint of amending the special
conditions, an additional demonstration would not be required. While
the limit of 29 passengers is somewhat arbitrary, the FAA must consider
whether other conditions should apply if the limit is raised.
One of the existing conditions is that there be no more than ten
seat rows on either side of the aisle. The 30 passenger arrangement
proposed by Jetstream still complies with this requirement. In fact,
the additional seat is located on the left side of the aisle at the
extreme rear of the airplane, and does not produce the same kind of
aisle offset that occurs throughout the cabin. This is because the seat
is opposite a windscreen at which point the aisle leads into the
passageway for the aft exit.
These special conditions are intended to provide requirements which
result in a cabin aisle that is as effective and safe as those
envisioned by the regulations for the maximum number of passengers on
the airplane. Where appropriate, requirements have been drawn from
existing regulations. In other cases, new requirements were developed
to preserve the level of safety which is inherent in the design of more
conventional aisle arrangements. The FAA considers that an additional
passenger does not invalidate the existing special conditions. It is
noted however, that further increase in passenger capacity would
violate one of the other conditions because it would result in more
than ten seat rows on at least one side of the aisle. Therefore, any
increase beyond 30 passenger seats would very likely require the
development of additional conditions. As noted above, the FAA has
determined that the staggered aisle should limit the passenger seating
capacity to something less than would otherwise be allowed by the
regulations. Under the terms of these special conditions, 30 is
considered to be the reasonable maximum.
As in the case of Special Conditions No. 25-ANM-45, an evacuation
demonstration would be required for the 30-passenger version. Since the
applicant chose to conduct it with 30 rather than 29 passengers, the
evacuation demonstration conducted for the 29-passenger version would
show compliance with this requirement for the 30-passenger version as
well.
Accordingly, in addition to the requirements of Sec. 25.815, the
following amended special conditions are proposed for Jetstream Model
4100 series airplanes with a staggered main aisle. Other conditions may
be developed as needed based on further FAA review and discussions with
the manufacturer and the Civil Aviation Authority (CAA).
As discussed above, the proposed special conditions would be
applicable initially to the 30 passenger version of the Jetstream
Aircraft Limited Jetstream Model 4101 airplane. Should Jetstream apply
at a later date for a change to the type certificate to include another
model of the 4100 series incorporating the same novel or unusual design
feature, the special conditions would apply to that model, as well,
under the provisions of Sec. 21.101(a)(1).
Jetstream, in their petition, requested that the amended special
conditions be promulgated without delay as a final rule and in time to
permit delivery of 30 passenger airplanes during August 1994. The FAA
has determined that public comment would be in the public interest, but
will shorten the comment period to 20 days in order to expedite the
issuance of the final special conditions.
Conclusion
This action affects only certain novel or unusual design features
on one Model of airplanes. It is not a rule of general applicability,
and it affects only the manufacturer who applied to the FAA for
approval of these features on the airplane.
List of Subjects in 14 CFR Part 25
Air transportation, Aircraft, Aviation safety, Safety.
The Proposed Amended Special Conditions
Accordingly, the Federal Aviation Administration proposes the
following amended special conditions for Jetstream Aircraft Limited
Model 4100 series airplanes with an offset main cabin aisle.
PART 25--[AMENDED]
The authority citation for these special conditions is as follows:
Authority: 49 U.S.C. 1344, 1348(c), 1352, 1354(a), 1355, 1421
through 1431, 1502, 1651(b)(2), 42 U.S.C. 1857f-10, 4321 et seq.,
E.O. 11514; 49 U.S.C. 106(g) (Revised Pub. L. 97-449, January 12,
1983).
1. Jetstream Model 4100 series airplanes may be approved with an
offset main aisle provided:
a. There are no more than 30 passenger seats with no more than ten
seat rows on either side of the aisle;
b. The interior arrangement includes on pair of Type II and one
pair of Type III passenger emergency exits;
c. In addition to the requirements of Sec. 25.815, the projected
aisle width is at least 20 inches measured at a height of 43 inches
above the aisle floor; and
d. The Type III exits and adjacent seat rows are offset
longitudinally such that persons approaching an exit from one end of
the cabin may use the exit without interfering with those approaching
the other exit from the other end of the cabin.
2. The location and part number of each passenger seat must be
defined by a drawing approved by the FAA or CAA-UK. The seat
arrangement may not be reconfigured without FAA approval.
3. An evacuation demonstration must be conducted to demonstrate the
efficacy of the aisle arrangement.
Issued in Renton, Washington, on August 30, 1994.
Stewart R. Miller,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 94-22620 Filed 9-12-94; 8:45 am]
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