[Federal Register Volume 67, Number 142 (Wednesday, July 24, 2002)]
[Rules and Regulations]
[Pages 48361-48365]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 02-18617]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. NM225; Special Conditions No. 25-207-SC]


Special Conditions: Embraer Model EMB-135BJ; 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 Embraer Model EMB-
135BJ airplane. The Embraer Model EMB-135BJ airplane will have a novel 
or unusual design feature involving a fuel transfer system whose 
failure can affect the structural performance of the airplane. The 
applicable airworthiness regulations do not contain adequate or 
appropriate safety standards for this system and its effect on 
structural performance. 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 
applicable airworthiness standards.

DATES: The effective date of these special conditions is July 12, 2002. 
Comments must be received on or before August 23, 2002.

ADDRESSES: Comments on these special conditions may be mailed in 
duplicate to: Federal Aviation Administration, Transport Airplane 
Directorate, Aircraft Certification Service, Attention: Rules Docket 
(ANM-113), Docket No. NM225, 1601 Lind Avenue SW., Renton, Washington 
98055-4056; or delivered in duplicate to the Transport Airplane 
Directorate at the above address. All comments must be marked: Docket 
No. NM225. Comments may be inspected in the Rules Docket weekdays, 
except Federal holidays, between 7:30 a.m. and 4 p.m.

FOR FURTHER INFORMATION CONTACT: Todd Martin, FAA, Airframe/Cabin 
Safety Branch, ANM-115, Transport Airplane Directorate, Aircraft 
Certification Service, 1601 Lind Avenue, SW., Renton, Washington 98055-
4056; telephone (425) 227-1178; facsimile (425) 227-1320.

SUPPLEMENTARY INFORMATION:
    The FAA has determined that notice and opportunity for prior public 
comment hereon are impracticable because these procedures would 
significantly delay certification of the airplane and thus delivery of 
the affected airplanes. The FAA therefore finds that good cause exists 
for making these special conditions effective upon issuance.

Comments Invited

    The FAA invites interested persons to participate in this 
rulemaking by submitting 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. The docket is available for public 
inspection 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 9 a.m. and 5 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 in light of the comments we receive.
    If you want the FAA to acknowledge receipt of your comments on 
these special conditions, include with your comments a pre-addressed, 
stamped postcard on which the docket number appears. We will stamp the 
date on the postcard and mail it to you.

Background

    On May 22, 2002, Embraer applied for an amendment to Type 
Certificate No. T00011AT to include a corporate jet version of the 
Model EMB-135 airplane. The Model EMB-135BJ, which is a derivative of 
the EMB-135LR aircraft currently approved under Type Certificate No. 
T00011AT, is a pressurized, low-wing, ``T'' tail, transport category 
airplane with tricycle landing gear. It is powered by two Rolls-Royce 
model AE3007A1P engines, and will carry a maximum of 19 passengers. The 
primary differences between the existing EMB-135LR and the new EMB-

[[Page 48362]]

135BJ are the addition of winglets, increased maximum takeoff weight 
(to 21,990 kg), increased maximum operational ceiling (to 39,000 feet), 
additional exposed underbelly fuel tank installed ahead of the air 
conditioning area, extra internal fuel tanks installed in the back of 
the baggage compartment, and a modified fuel system due to the extra 
tanks. The new fuel system can serve to alleviate loads in the airframe 
and, when in a failure state, can create loads in the airframe. The 
current regulations do not adequately account for the effects of these 
systems and their failures on structural performance. These special 
conditions will require Embraer to substantiate the strength capability 
and freedom from aeroelastic instabilities after failures in the fuel 
transfer system.

Type Certification Basis

    Under the provisions of Sec. 21.101, Embraer must show that the 
Model EMB-135BJ meets the applicable provisions of the regulations 
incorporated by reference in Type Certificate T00011AT, or the 
applicable regulations in effect on the date of application for the 
change. 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.T00011AT are 14 CFR part 25, effective February 1, 
1965, including Amendments 25-1 through 25-84; Amendment 25-85; 
Sec. 25.1517, as amended by Amendment 25-86; Amendment 25-88; Amendment 
25-90; Secs. 25.331, 25.335(b)(2), 25.345, 25.351, 25.363, 25.371, 
25.415, 25.491, 25.499 and 25.561, as amended by Amendment 25-91; 
Amendment 25-93; Sec. 25.807, as amended by Amendment 25-94; and 
Amendment 25-97. In addition, the certification basis includes certain 
special conditions, exemptions, and equivalent safety findings that are 
not relevant to these special conditions.
    If the Administrator finds that the applicable airworthiness 
regulations (i.e., part 25, as amended) do not contain adequate or 
appropriate safety standards for the Model EMB-135BJ because of a novel 
or unusual design feature, special conditions are prescribed under the 
provisions of Sec. 21.16.
    In addition to the applicable airworthiness regulations and special 
conditions, the Model EMB-135BJ 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.
    Special conditions, as defined in Sec. 11.19, are issued in 
accordance with Sec. 11.38, and become part of the type certification 
basis in accordance with Sec. 21.101(b)(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 Feature

    The Model EMB-135BJ will have systems that affect the structural 
performance of the airplane, either directly or as a result of a 
failure or malfunction. These novel or unusual design features are 
systems that can serve to alleviate loads in the airframe and, when in 
a failure state, can create loads in the airframe. The current 
regulations do not adequately account for the effects of these systems 
and their failures on structural performance. These special conditions 
provide the criteria to be used in assessing the effects of these 
systems on structures.

Conclusion

    This action affects only certain novel or unusual design features 
on one model airplane. It is not a rule of general applicability and 
affects only the applicant who applied to the FAA for approval of these 
features on the airplane.

Immediate Adoption

    The substance of these special conditions has been subjected to the 
notice and comment period in several prior instances and has been 
derived without substantive change from those previously issued. It is 
unlikely that prior public comment would result in a significant change 
from the substance contained herein. For this reason, and because a 
delay would significantly affect certification of the Embraer Model 
EMB-135BJ, which is imminent, the FAA has determined that prior public 
notice and comment are unnecessary and impracticable, and good cause 
exists for adopting these special conditions upon issuance. The FAA is 
requesting comments to allow interested persons to submit views that 
may not have been submitted in response to the prior opportunities for 
comment described above.

List of Subjects in 14 CFR Part 25

    Aircraft, Aviation safety, Reporting and recordkeeping 
requirements.

    The authority citation for these special conditions is as follows:

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

The Special Conditions

Interaction of Systems and Structure

1. General
    For airplanes equipped with systems that affect structural 
performance, either directly or as a result of a failure or 
malfunction, the influence of these systems and their failure 
conditions must be taken into account when showing compliance with the 
requirements of subparts C and D of part 25. The following criteria 
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, and fuel management systems. If these special conditions are 
used for other systems, it may be necessary to adapt the criteria to 
the specific system.
    (a) The criteria defined herein only address the direct structural 
consequences of the system responses and performances and cannot be 
considered in isolation but should be included in the overall safety 
evaluation of the airplane. These criteria may in some instances 
duplicate standards already established for this evaluation. These 
criteria are only applicable to structures whose failure could prevent 
continued safe flight and landing. Specific criteria that define 
acceptable limits on handling characteristics or stability requirements 
when operating in the system degraded or inoperative modes are not 
provided in these special conditions.
    (b) Depending upon the specific characteristics of the airplane, 
additional studies that go beyond the criteria provided in these 
special conditions may be required in order to demonstrate the 
capability of the airplane to meet other realistic conditions, such as 
alternative gust or maneuver descriptions, for an airplane equipped 
with a load alleviation system.
    (c) The following definitions are applicable to these special 
conditions.
    Structural performance: Capability of the airplane to meet the 
structural requirements of part 25.
    Flight limitations: Limitations that can be applied to the airplane 
flight conditions following an in-flight occurrence and that are 
included in the

[[Page 48363]]

flight manual (e.g., speed limitations, avoidance of severe weather 
conditions, etc.).
    Operational limitations: Limitations, including flight limitations 
that can be applied to the airplane operating conditions before 
dispatch (e.g., fuel, payload, and Master Minimum Equipment List 
limitations).
    Probabilistic terms: The probabilistic terms (probable, improbable, 
extremely improbable) used in these special conditions are the same as 
those used in Sec. 25.1309.
    Failure condition: The term failure condition is the same as that 
used in Sec. 25.1309; however, these special conditions apply only to 
system failure conditions that affect the structural performance of the 
airplane (e.g., system failure conditions that induce loads, lower 
flutter margins, or change the response of the airplane to inputs such 
as gusts or pilot actions).
2. Effects of Systems on Structures
    The following criteria will be used in determining the influence of 
a system and its failure conditions on the airplane structure.
    (a) System fully operative. With the system fully operative, the 
following apply:
    (1) Limit loads must be derived in all normal operating 
configurations of the system from all the limit conditions 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 nonlinearity (rate of displacement of control surface, 
thresholds, or any other system nonlinearities) must be accounted for 
in a realistic or conservative way when deriving limit loads from limit 
conditions.
    (2) The airplane must meet the strength requirements of part 25 
(static strength, 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 when it can be shown that the airplane has 
design features that will not allow it to exceed those limit 
conditions.
    (3) The airplane must meet the aeroelastic stability requirements 
of Sec. 25.629.
    (b) System in the failure condition. For any system failure 
condition not shown to be extremely improbable, the following apply:
    (1) At the time of occurrence. Starting from 1-g level flight 
conditions, a realistic scenario, including pilot corrective actions, 
must be established to determine the loads occurring at the time of 
failure and immediately after failure.
    (i) For static strength substantiation, these loads multiplied by 
an appropriate factor of safety that is related to the 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]TR24JY02.000

    (ii) For residual strength substantiation, the airplane must be 
able to withstand two thirds of the ultimate loads defined in paragraph 
(b)(1)(i) above.
    (iii) Freedom from aeroelastic instability must be shown up to the 
speeds defined in Sec. 25.629(b)(2). For failure conditions that result 
in speed increases beyond Vc/Mc, freedom from aeroelastic instability 
must be shown to increased speeds, so that the margins intended by 
Sec. 25.629(b)(2) are maintained.
    (iv) 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.
    (2) For the continuation of the flight. For the airplane in the 
system failed state and considering any appropriate reconfiguration and 
flight limitations, the following apply:
    (i) The loads derived from the following conditions at speeds up to 
Vc, or the speed limitation prescribed for the remainder of the flight, 
must be determined:
    (A) The limit symmetrical maneuvering conditions specified in 
Secs. 25.331 and 25.345.
    (B) The limit gust and turbulence conditions specified in 
Secs. 25.341 and 25.345.
    (C) The limit rolling conditions specified in Sec. 25.349, and the 
limit unsymmetrical conditions specified in Sec. 25.367 and 
Sec. 25.427(b) and (c).
    (D) The limit yaw maneuvering conditions specified in Sec. 25.351.
    (E) The limit ground loading conditions specified in Secs. 25.473 
and 25.491.
    (ii) For static strength substantiation, each part of the structure 
must be able to withstand the loads defined in paragraph (2)(i) above, 
multiplied by a factor of safety depending on the probability of being 
in this failure state. The factor of safety is defined in Figure 2.

[[Page 48364]]

[GRAPHIC][TIFF OMITTED]TR24JY02.001

    Qj = (Tj)(Pj) where:
    Tj = Average time spent in failure condition j (in 
hours).
    Pj = Probability of occurrence of failure mode j (per 
hour).

    Note: If Pj is greater than 10-3 per flight hour, 
then a 1.5 factor of safety must be applied to all limit load 
conditions specified in subpart C.

    (iii) For residual strength substantiation, the airplane must be 
able to withstand two thirds of the ultimate loads defined in paragraph 
(2)(ii) above.
    (iv) If the loads induced by the failure condition have a 
significant effect on fatigue or damage tolerance, then their effects 
must be taken into account.
    (v) Freedom from aeroelastic instability must be shown up to a 
speed determined from Figure 3. Flutter clearance speeds VI 
and VII 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]TR24JY02.002

    VI = Clearance speed as defined by Sec. 25.629(b)(2).
    VII = Clearance speed as defined by Sec. 25.629(b)(1).
    Qj = (Tj)(Pj) where:
    Tj = Average time spent in failure condition j (in 
hours).
    Pj = Probability of occurrence of failure mode j (per 
hour).

    Note: If Pj is greater than 10-3 per flight hour, 
then the flutter clearance speed must not be less than 
VII.

    (vi) Freedom from aeroelastic instability must also be shown up to 
VI in Figure 3 above for any probable system failure 
condition combined with any damage required or selected for 
investigation by Sec. 25.571(b).
    (3) 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 10-9, criteria other than those specified in this 
paragraph may be used for structural substantiation to show continued 
safe flight and landing.
    (c) Warning considerations. For system failure detection and 
warning, the following apply:
    (1) The system must be checked for failure conditions, not 
extremely improbable, that degrade the structural capability below the 
level required by part 25, or significantly reduce the reliability of 
the remaining system. 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, in lieu of 
warning systems, to achieve the objective of this requirement. These 
certification maintenance requirements must be limited to components 
that are not readily detectable by normal warning 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 factor of safety between the airplane 
strength and the loads of subpart C below 1.25, or flutter margins 
below VII, must be signaled to the crew during flight.
    (d) 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

[[Page 48365]]

structural performance, then the provisions of these special conditions 
must be met for the dispatched condition and for subsequent failures. 
Flight limitations and expected operational limitations may be taken 
into account in establishing Qj 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 10-3 
per hour.

    Issued in Renton, Washington, on July 12, 2002.
Ali Bahrami,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 02-18617 Filed 7-23-02; 8:45 am]
BILLING CODE 4910-13-P