[Federal Register Volume 75, Number 221 (Wednesday, November 17, 2010)]
[Rules and Regulations]
[Pages 70092-70096]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2010-28999]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. NM434; Notice No. 25-412-SC]


Special Conditions: Bombardier Inc. Model CL-600-2E25 Airplane, 
Interaction of Systems and Structures

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final special conditions; request for comments.

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SUMMARY: These special conditions are issued for the Bombardier Inc. 
Model CL-600-2E25 airplane. This airplane will have a novel or unusual 
design feature associated with the rudder-traveler limiting system 
controlling the command-by-wire (CBW) rudder. This system can serve to 
alleviate loads in the airframe but, in a failure state, can create 
loads in the airframe. The applicable airworthiness regulations do not 
contain adequate or appropriate safety standards for this design 
feature. These special conditions contain the additional safety 
standards that the Administrator considers necessary to establish a 
level of safety equivalent to that established by the existing 
airworthiness standards.

DATES: The effective date of these special conditions is November 5, 
2010. We must receive your comments by January 3, 2011.

ADDRESSES: You must mail two copies of your comments to: Federal 
Aviation Administration, Transport Airplane Directorate, Attn: Rules 
Docket (ANM-113), Docket No. NM434, 1601 Lind Avenue, SW., Renton, 
Washington 98057-3356. You may deliver two copies to the Transport 
Airplane Directorate at the above address. You must mark your comments: 
Docket No. NM434. You can inspect comments in the Rules Docket 
weekdays, except Federal holidays, between 7:30 a.m. and 4 p.m.

FOR FURTHER INFORMATION CONTACT: Todd Martin, FAA, ANM-115, Transport 
Airplane Directorate, Aircraft Certification Service, 1601 Lind Avenue, 
SW., Renton, Washington 98057-3356; telephone (425) 227-1178; facsimile 
(425) 227-1149.

SUPPLEMENTARY INFORMATION: The FAA has determined that notice of, and 
opportunity for prior public comment on, these special conditions are 
impracticable because these procedures would significantly delay 
issuance of the design approval and thus delivery of the affected 
aircraft. In addition, the substance of these special conditions has 
been subject to the public-comment process in several prior instances 
with no substantive comments received. The FAA therefore finds that 
good cause exists for making these special conditions effective upon 
issuance.

Comments Invited

    We invite interested people to take part in this rulemaking by 
sending written comments, data, or views. The most helpful comments 
reference a specific portion of the special conditions, explain the 
reason for any recommended change, and include supporting data. We ask 
that you send us two copies of written comments.
    We will file in the docket all comments we receive, as well as a 
report summarizing each substantive public contact with FAA personnel 
concerning these special conditions. You can inspect the docket before 
and after the comment closing date. If you wish to review the docket in 
person, go to the address in the ADDRESSES section of this preamble 
between 7:30 a.m. and 4 p.m., Monday through Friday, except Federal 
holidays.
    We will consider all comments we receive on or before the closing 
date for comments. We will consider comments filed late if it is 
possible to do so without incurring expense or delay. We may change 
these special conditions based on the comments we receive.
    If you want us to acknowledge receipt of your comments on these 
special conditions, include with your comments a self-addressed, 
stamped postcard on which you have written the docket number. We will 
stamp the date on the postcard and mail it back to you.

Background

    On February 28, 2007, Bombardier Inc. applied for an amendment to 
Type Certificate No. A21EA, through Transport Canada, to include the 
new Model CL-600-2E25 airplane. The CL-600-2E25, which is a derivative 
of the CL-600-2D24 currently approved under Type Certificate No. A21EA, 
is to be certified for a maximum occupancy of 110 people, including 5 
crewmembers. The CL-600-2E25 has increased gross weight, extended wing 
tip, and increased fuselage length to accommodate the additional 
passengers as compared to the CL-600-2D24.
    The CL-600-2E25 will have a CBW rudder-control system that will 
affect the structural performance of the airplane. The airplane will 
use CBW Rudder Electronic Control Unit (ECU) software as a replacement 
for the Rudder Travel Limiter to limit rudder commands. The CBW Rudder 
ECU controls the rudder, trim, and yaw damping as well. This system can 
serve to alleviate loads in the airframe but, in a failure state, can 
create loads in the airframe. The current rules do not adequately 
account for the effects of this system and its failures on structural 
performance. The special conditions defined herein provide the criteria 
to be used in assessing the effects of this system on structures.

Type Certification Basis

    Under the provisions of Sec.  21.101, Bombardier Inc. must show 
that the Model CL-600-2E25 airplane meets the applicable provisions of 
Title 14, Code of Federal Regulations (14 CFR) part 25, as amended by 
Amendments 25-1 through 25-119, except for earlier amendments as agreed 
upon by the FAA. These regulations will be incorporated into Type 
Certificate No. A21EA after type-certification approval of the Model 
CL-600-2E25. The regulations incorporated by reference in the type 
certificate are commonly referred to as the ``original type-
certification basis.'' The regulations incorporated by reference in 
Type Certificate No. A21EA are as follows:
    The original type-certification basis for the Model CL-600-2D24 
(CRJ 900), shown on TCDS A21EA, Revision 25, and reprinted below.

Model CL-600-2D15/CL-600-2D24

    Part 25, including Amendments 25-1 through 25-86, Amendments 25-88 
through Amendments 25-90, and Amendments 25-92 through 25-98 with the 
following exceptions:
    <bullet> Section 25.783(f) at Amendment 25-23 shall replace Sec.  
25.783(f) at Amendment 25-88 for the Aft Cargo Compartment and Main 
Avionics Bay Doors only (common doors with CL-600-2C10 (CRJ-700);

[[Page 70093]]

    <bullet> Section 25.807(d)(6) at Amendment 25-72 shall replace 
Sec.  25.807(h) at Amendment 25-94;
    <bullet> Sections 25.365, 25.831(a), and 25.1447(c) at Amendment 
25-87. Part 25, Amendment 25-91, is not included in the type-
certification basis.

Additional FAA Requirements for Model CL-600-2D15/CL-600-2D24

1. 14 CFR part 36, effective September 10, 1990, and including all 
amendments effective on the date of type certification.
2. 14 CFR part 34, effective September 10, 1990, and including all 
amendments effective on the date of type certification.
3. Special Conditions:
    (a) High Intensity Radiated Fields, No. 25-ANM-109, dated October 
31, 1995.
    (b) Go-around Performance Credit for Use of Automatic Power Reserve 
(APR), No. 25-167-SC, dated October 24, 2000 (same as CL-600-2C10).
    (c) Sudden Engine Stoppage, No. 25-217-SC, dated October 04, 2002.
    (d) Passenger Seats with Non-traditional, Large, Non-metallic 
Panels, No. 25-384-SC, dated August 12, 2009.
4. Exemptions: Exemption No. 7447, hydraulic-systems testing per 14 CFR 
25.1435(b)(1). Equivalent safety has been established for the following 
requirements:

CL-600-2D15/CL-600-2D24

1. Section 25.103 and others, Reduced Minimum Operating Speed Factors.
2. Section 25.811(d)(2), Main Door Exit Marking Sign.
3. Section 25.813(c)(2)(i), Emergency Exit Access.
4. Section 25.904, Performance Credit for Use of APR During Reduced 
Thrust Takeoff.
5. Section 25.933(a)(1)(ii), Thrust Reverser System.
6. Section 25, appendix I, Sec.  25.5(b)(4), Lack of On/Off Switch for 
Automatic Takeoff Thrust Control System (ATTCS).
7. Section 25.841(b)(6), High Altitude Takeoff and Landing Operations 
documented in Transport Airplane Directorate ELOS Memo AT2587NY-T, 
dated January 31, 2007.
    In addition, the certification basis includes other regulations, 
special conditions, and exemptions that are not relevant to these 
special conditions. Type Certificate No. A21EA will be updated to 
include a complete description of the certification basis for this 
airplane model.
    If the Administrator finds that the applicable airworthiness 
regulations (i.e., 14 CFR part 25) do not contain adequate or 
appropriate safety standards for the CL-600-2E25 because of a novel or 
unusual design feature, special conditions are prescribed under the 
provisions of 14 CFR 21.16.
    In addition to the applicable airworthiness regulations and special 
conditions, the CL-600-2E25 must comply with the fuel-vent and exhaust-
emission requirements of 14 CFR part 34, and the noise-certification 
requirements of 14 CFR part 36.
    The FAA issues special conditions, as defined in 14 CFR 11.19, in 
accordance with Sec.  11.38, and they become part of the type-
certification basis under 14 CFR 21.101.
    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 or similar 
novel or unusual design feature, or should any other model already 
included on the same type certificate be modified to incorporate the 
same or similar novel or unusual design feature, the special conditions 
would also apply to the other model under Sec.  21.101.

Novel or Unusual Design Features

    The Bombardier Model CL-600-2E25 airplane will incorporate the 
following novel or unusual design features:
    The CL-600-2E25 airplane will have a CBW rudder-control system that 
will affect the structural performance of the airplane. The airplane 
will use a CBW Rudder ECU software as a replacement for the rudder-
travel limiter to limit rudder commands. The CBW Rudder ECU controls 
the rudder, trim, and yaw damping as well.

Discussion

    This CBW system can affect the airplane's structural performance, 
either directly or as a result of failure or malfunction. That is, the 
CBW system affects how the airplane responds in maneuver and gust 
conditions, and thereby affects the airplane's structural capability. 
Such systems represent a novel and unusual feature when compared to the 
technology envisioned in the current airworthiness standards. Special 
conditions are needed to require consideration of the effects of the 
system on the structural capability and aeroelastic stability of the 
airplane, both in the normal and in the failed state. These special 
conditions require that the airplane meet the structural requirements 
of subparts C and D of 14 CFR part 25 when the airplane systems are 
fully operative. These special conditions also require that the 
airplane meet these requirements considering failure conditions. In 
some cases, these special conditions allow reduced margins (in terms of 
speed margins and factors of safety) for failure conditions, as a 
function of system reliability.
    The Administrator considers these special conditions necessary to 
establish a level of safety equivalent to that established by the 
existing airworthiness standards.

Applicability

    As discussed above, these special conditions are applicable to the 
Model CL-600-2E25. Should Bombardier Inc. apply at a later date for a 
change to the type certificate to include another airplane model 
incorporating the same novel or unusual design feature, these special 
conditions would apply to that model as well.

Conclusion

    This action affects only certain novel or unusual design features 
on one model of airplane. It is not a rule of general applicability.
    Under standard practice, the effective date of final special 
conditions would be 30 days after the date of publication in the 
Federal Register. However, as the certification date for the Model CL-
600-2E25 is imminent, the FAA finds that good cause exists to make 
these special conditions effective upon issuance.

List of Subjects in 14 CFR Part 25

    Aircraft, Aviation safety, Reporting and recordkeeping 
requirements.

0
The authority citation for these special conditions is as follows:

    Authority: 49 U.S.C. 106(g), 40113, 44701, 44702, 44704.

The Special Conditions

0
Accordingly, pursuant to the authority delegated to me by the 
Administrator, the following special conditions are issued as part of 
the type-certification basis for Bombardier Model CL-600-2E25 airplanes 
modified according to DCA 0145-000-00020-2008/FAA (latest revision 
approved by the FAA).

1. CWB Rudder-Control-System Special Conditions

    The Bombardier Model CL-600-2E25 airplane is equipped with systems 
that affect the airplane's structural performance either directly or as 
a result of failure or malfunction. The influence of these systems and 
their failure conditions must be taken into account when showing 
compliance with requirements of 14 CFR part 25, subparts C and D. The 
following criteria

[[Page 70094]]

must be used for showing compliance with these special conditions for 
airplanes equipped with flight-control systems, autopilots, stability-
augmentation systems, load-alleviation systems, flutter-control 
systems, fuel-management systems, and other systems that either 
directly, or as a result of failure or malfunction, affect structural 
performance. If these special conditions are used for other systems, it 
may be necessary to adapt the criteria to the specific systems.
    (a) The criteria defined here address only direct structural 
consequences of system responses and performances. They cannot be 
considered in isolation but should be included in the overall safety 
evaluation of the airplane. They may, in some instances, duplicate 
standards already established for this evaluation. These criteria are 
only applicable to structure the failure of which could prevent 
continued safe flight and landing. Specific criteria defining 
acceptable limits on handling characteristics or stability 
requirements, when operating in the system-degraded or inoperative 
mode, are not provided in these special conditions.
    (b) Depending on the specific characteristics of the airplane, 
additional studies may be required, which go beyond the criteria 
provided in these special conditions, to demonstrate the capability of 
the airplane to meet other realistic conditions such as alternative 
gust conditions or maneuvers for an airplane equipped with a load-
alleviation system.
    (c) The following definitions are applicable to these special 
conditions:
    (1) Structural performance: The capability of the airplane to meet 
the structural requirements of part 25.
    (2) Flight limitations: Limitations that can be applied to the 
airplane flight conditions following an in-flight failure occurrence, 
and that are included in the flight manual (speed limitations or 
avoidance of severe weather conditions, for example).
    (3) Operational limitations: Limitations, including flight 
limitations, that can be applied to the airplane operating conditions 
before dispatch, and which include, for example, fuel, payload, and 
master minimum-equipment-list limitations.
    (4) Probabilistic terms: Terms, including probable, improbable, and 
extremely improbable, used in these special conditions and which are 
the same as those probabilistic terms used in Sec.  25.1309.
    (5) Failure condition: The same term as used in Sec.  25.1309. 
However, in these special conditions, the term ``failure condition'' 
applies only to system-failure conditions that affect structural 
performance of the airplane. Examples are system-failure conditions 
that induce loads, change the response of the airplane to inputs such 
as gusts or pilot actions, or lower flutter margins.

    Note: Although failure-annunciation-system reliability must be 
included in probability calculations for paragraph (d)(2) of these 
special conditions, there is no specific reliability requirement for 
the annunciation system required in paragraph (e) of these special 
conditions.

    (d) General. The following criteria will be used in determining the 
influence of a system and its failure conditions on the airplane 
structure:
    (1) System fully operative. With the system fully operative, the 
following apply:
    (i) Limit loads must be derived in all normal operating 
configurations of the system from all the limit conditions specified in 
subpart C of 14 CFR part 25 (or used in lieu of those specified in 
subpart C), taking into account any special behavior of such a system 
or associated functions, or any effect on the structural performance of 
the airplane that may occur up to the limit loads. In particular, any 
significant degree of nonlinearity in rate of displacement of control 
surface or thresholds, or any other system nonlinearities, must be 
accounted for in a realistic or conservative way when deriving limit 
loads from limit conditions.
    (ii) The airplane must meet the strength requirements of part 25 
for static strength and residual strength, using the specified factors 
to derive ultimate loads from the limit loads defined above. The effect 
of nonlinearities must be investigated beyond limit conditions to 
ensure the behavior of the system presents no anomaly compared to the 
behavior below limit conditions. However, conditions beyond limit 
conditions need not be considered if the applicant demonstrates that 
the airplane has design features that will not allow it to exceed those 
limit conditions.
    (iii) The airplane must meet the aeroelastic stability requirements 
of Sec.  25.629.
    (2) System in the failure condition. For any system failure 
condition not shown to be extremely improbable, the following apply:
    (i) Establishing loads at the time of occurrence. Starting from 1g 
level flight conditions, a realistic scenario including pilot 
corrective actions must be established to determine loads occurring at 
the time of failure and immediately after failure.
    (A) For static-strength substantiation, these loads, multiplied by 
an appropriate factor of safety related to probability of occurrence of 
the failure, are ultimate loads to be considered for design. The factor 
of safety (FS) is defined in Figure 1.
[GRAPHIC] [TIFF OMITTED] TR17NO10.051


[[Page 70095]]


    (B) For residual-strength substantiation, the airplane must be able 
to withstand two-thirds of the ultimate loads defined in paragraph 
(d)(2)(i)(A) of these special conditions. For pressurized cabins, these 
loads must be combined with the normal operating differential pressure.
    (C) Freedom from aeroelastic instability must be shown up to the 
speeds defined in Sec.  25.629(b)(2). For failure conditions that 
result in speeds beyond design cruise speed or design cruise mach 
number (V<INF>c</INF>/M<INF>c</INF>), freedom from aeroelastic 
instability must be shown to increased speeds, so that the margins 
intended by Sec.  25.629(b)(2) are maintained.
    (D) Failures of the system that result in forced structural 
vibrations (oscillatory failures) must not produce loads that could 
result in detrimental deformation of primary structure.
    (3) Establishing loads in the system-failed state for the 
continuation of the flight. For airplane-flight continuation in the 
system-failed state, and considering any appropriate reconfiguration 
and flight limitations, the following apply:
    (i) Loads derived from the following conditions (or used in lieu of 
the following conditions) at speeds up to V<INF>c</INF>/M<INF>c</INF>, 
or the speed limitation prescribed for the remainder of the flight, 
must be determined:
    (A) The limit symmetrical-maneuvering conditions specified in 
Sec. Sec.  25.331 and 25.345.
    (B) The limit gust-and-turbulence conditions specified in 
Sec. Sec.  25.341 and 25.345.
    (C) The limit rolling conditions specified in Sec.  25.349 and the 
limit unsymmetrical conditions specified in Sec. Sec.  25.367 and 
25.427(b) and (c).
    (D) The limit yaw-maneuvering conditions specified in Sec.  25.351.
    (E) The limit ground-loading conditions specified in Sec. Sec.  
25.473 and 25.491.
    (ii) For static-strength substantiation, each part of the structure 
must be able to withstand the loads in paragraph (d)(3)(i) of these 
special conditions, multiplied by a FS depending on the probability of 
being in this failure state. The FS is defined in Figure 2.
[GRAPHIC] [TIFF OMITTED] TR17NO10.052

Q<INF>j</INF> = (T<INF>j</INF>)(P<INF>j</INF>)

Where:

T<INF>j</INF> = Average time spent in failure condition j (in hours)
P<INF>j</INF> = Probability of occurrence of failure mode j (per 
hour)

    Note: If P<INF>j</INF> is greater than 10<SUP>-3</SUP> per 
flight hour, then a 1.5 FS must be applied to all limit-load 
conditions specified in part 25, subpart C.

    (iii) For residual-strength substantiation, the airplane must be 
able to withstand two-thirds of the ultimate loads defined in paragraph 
(d)(3)(ii) of these special conditions. For pressurized cabins, these 
loads must be combined with the normal operating differential pressure.
    (iv) If the loads induced by the failure condition have a 
significant effect on fatigue or damage tolerance, then the effects of 
these loads must be taken into account.
    (v) Freedom from aeroelastic instability must be shown up to a 
speed determined from Figure 3. Flutter-clearance speeds V' and V'' may 
be based on the speed limitation specified for the remainder of the 
flight using the margins defined by Sec.  25.629(b).
[GRAPHIC] [TIFF OMITTED] TR17NO10.053

V' = Clearance speed as defined by Sec.  25.629(b)(2)
V'' = Clearance speed as defined by Sec.  25.629(b)(1)
Q<INF>j</INF> = (T<INF>j</INF>)(P<INF>j</INF>)

Where:


[[Page 70096]]


T<INF>j</INF> = Average time spent in failure condition j (in hours)
P<INF>j</INF> = Probability of occurrence of failure mode j (per 
hour)

    Note: If P<INF>j</INF> is greater than 10<SUP>-3</SUP> per 
flight hour, then the flutter-clearance speed must not be less than 
V''.

    (vi) Freedom from aeroelastic instability must also be shown up to 
V' in Figure 3 above, for any probable system-failure condition, 
combined with any damage, required or selected for investigation by 
Sec.  25.571(b).
    (4) Consideration of certain failure conditions may be required by 
other sections of part 25 regardless of calculated system reliability. 
Where analysis shows the probability of these failure conditions to be 
less than 10<SUP>-9</SUP>, criteria other than those specified in this 
paragraph may be used for structural substantiation to show continued 
safe flight and landing.
    (e) Failure indications. For system failure detection and 
indication, the following apply:
    (1) The system must be checked for failure conditions, not 
extremely improbable, that degrade the structural capability of the 
airplane below the level required by part 25 or significantly reduce 
the reliability of the remaining system. As far as reasonably 
practicable, the flightcrew must be made aware of these failures before 
flight. Certain elements of the control system, such as mechanical and 
hydraulic components, may use special periodic inspections, and 
electronic components may use daily checks, instead of detection and 
indication systems to achieve the objective of this requirement. Such 
certification-maintenance inspections or daily checks must be limited 
to components on which faults are not readily detectable by normal 
detection and indication systems, and where service history shows that 
inspections will provide an adequate level of safety.
    (2) The existence of any failure condition, not extremely 
improbable during flight, that could significantly affect the 
structural capability of the airplane and for which the associated 
reduction in airworthiness can be minimized by suitable flight 
limitations, must be signaled to the flightcrew. For example, failure 
conditions that result in a FS between the airplane strength and the 
loads of part 25, subpart C, below 1.25, or flutter margins below V'', 
must be signaled to the crewmembers during flight.
    (f) Dispatch with known failure conditions. If the airplane is to 
be dispatched in a known system-failure condition that affects 
structural performance, or affects the reliability of the remaining 
system to maintain structural performance, then the provisions of these 
special conditions must be met, including the provisions of paragraph 
(d)(1) of these special conditions for the dispatched condition, and 
paragraph (d)(2) of these special conditions for subsequent failures. 
Expected operational limitations may be taken into account in 
establishing P<INF>j</INF> as the probability of failure occurrence for 
determining the safety margin in Figure 1. Flight limitations and 
expected operational limitations may be taken into account in 
establishing Q<INF>j</INF> as the combined probability of being in the 
dispatched failure condition and the subsequent failure condition for 
the safety margins in Figures 2 and 3. These limitations must be such 
that the probability of being in this combined failure state, and then 
subsequently encountering limit load conditions, is extremely 
improbable. No reduction in these safety margins is allowed if the 
subsequent system-failure rate is greater than 10<SUP>-3</SUP> per 
hour.

    Issued in Renton, Washington, on November 5, 2010.
Jeffrey Duven,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 2010-28999 Filed 11-16-10; 8:45 am]
BILLING CODE 4910-13-P