[Federal Register Volume 68, Number 172 (Friday, September 5, 2003)]
[Rules and Regulations]
[Pages 52684-52688]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 03-22565]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. NM248; Special Conditions No. 25-241-SC]


Special Conditions: Embraer Model ERJ-170 series airplanes; 
Electronic Flight Control Systems; Automatic Takeoff Thrust Control 
System

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final special conditions.

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SUMMARY: These special conditions are issued for the Embraer Model ERJ-
170 series airplanes. These airplanes will have novel or unusual design 
features when compared to the state of technology envisioned in the 
airworthiness standards for transport category airplanes. These design 
features are associated with (1) Electronic Flight Control Systems and 
(2) Automatic Takeoff Thrust Control System (ATTCS). The applicable 
airworthiness regulations do not contain adequate or appropriate safety 
standards

[[Page 52685]]

for these design features. 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. Additional special conditions will be 
issued for other novel or unusual design features of Embraer Model 170 
series airplanes.

EFFECTIVE DATE: August 15, 2003.

FOR FURTHER INFORMATION CONTACT: Tom Groves, FAA, International Branch, 
ANM-116, Transport Airplane Directorate, Aircraft Certification 
Service, 1601 Lind Avenue SW., Renton, Washington 98055-4056; telephone 
(425) 227-1503; facsimile (425) 227-1149; email [email protected].

SUPPLEMENTARY INFORMATION: 

Background

    On May 20, 1999, Embraer applied for a type certificate for its new 
Model ERJ-170 airplane. Two basic versions of the Model ERJ-170 are 
included in the application. The ERJ-170-100 airplane is a 69-78 
passenger, twin-engine regional jet with a maximum takeoff weight of 
81,240 pounds. The ERJ-170-200 is a derivative with a lengthened 
fuselage. Passenger capacity for the ERJ-170-200 is increased to 86, 
and maximum takeoff weight is increased to 85,960 pounds.

Type Certification Basis

    Under the provisions of 14 CFR 21.17, Embraer must show that the 
Model ERJ-170 series airplanes meet the applicable provisions of 14 CFR 
part 25, as amended by Amendments 25-1 through 25-98.
    If the Administrator finds that the applicable airworthiness 
regulations (i.e., part 25, as amended) do not contain adequate or 
appropriate safety standards for Embraer Model ERJ-170 series airplanes 
because of novel or unusual design features, special conditions are 
prescribed under the provisions of Sec.  21.16.
    In addition to the applicable airworthiness regulations and special 
conditions, Embraer Model ERJ-170 series airplanes 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, and the FAA must 
issue a finding of regulatory adequacy pursuant to Sec.  611 of Public 
Law 93-574, the ``Noise Control Act of 1972.''
    Special conditions, as defined in 14 CFR 11.19, are issued in 
accordance with Sec.  11.38 and become part of the type certification 
basis in accordance with Sec.  21.17(a)(2), Amendment 21-69, effective 
September 16, 1991.
    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 incorporate 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 features, the special conditions would also apply to the 
other model under the provisions of Sec.  21.101(a)(1), Amendment 21-
69, effective September 16, 1991.

Novel or Unusual Design Features

    The Embraer Model ERJ-170 series airplanes will incorporate the 
following novel or unusual design features:

I. Electronic Flight Control System

    In airplanes with electronic flight control systems, there may not 
always be a direct correlation between pilot control position and the 
associated airplane control surface position. Under certain 
circumstances, a commanded maneuver that does not require a large 
control input may require a large control surface movement, possibly 
encroaching on a control surface or actuation system limit without the 
flightcrew's knowledge. This situation can arise in either manually 
piloted or autopilot flight and may be further exacerbated on airplanes 
where the pilot controls are not back-driven during autopilot system 
operation. Unless the flightcrew is made aware of excessive deflection 
or impending control surface limiting, control of the airplane by the 
pilot or autoflight system may be inadvertently continued so as to 
cause loss of control of the airplane or other unsafe characteristics 
of stability or performance.
    Given these possibilities, a special condition for Embraer Model 
ERJ-170 series airplanes addresses control surface position awareness. 
This special condition requires that suitable display or annunciation 
of flight control position be provided to the flightcrew when near full 
surface authority (not crew-commanded) is being used, unless other 
existing indications are found adequate or sufficient to prompt any 
required crew actions. Suitability of such a display or annunciation 
must take into account that some piloted maneuvers may demand the 
airplane's maximum performance capability, possibly associated with a 
full control surface deflection. Therefore, simple display systems--
that would function in both intended and unexpected control-limiting 
situations--must be properly balanced to provide needed crew awareness 
and minimize nuisance alerts. A monitoring system that compares 
airplane motion, surface deflection, and pilot demand could be useful 
in eliminating nuisance alerting.

II. Automatic Takeoff Thrust Control System (ATTCS)

    The Embraer Model ERJ-170 series airplane will incorporate an 
Automatic Takeoff Thrust Control System (ATTCS) in the engine's Full 
Authority Digital Electronic Control (FADEC) system architecture. The 
manufacturer requested that the FAA issue special conditions to allow 
performance credit to be taken for use of this function during go-
around to show compliance with the requirement of Sec.  25.121(d) 
regarding the approach climb gradient.
    Section 25.904 and Appendix I refer to operation of ATTCS only 
during takeoff. Model ERJ-170 series airplanes have this feature for 
go-around also. The ATTCS will automatically increase thrust to the 
maximum go-around thrust available under the ambient conditions in the 
following circumstances:
    [sbull] If an engine failure occurs during an all-engines-operating 
go-around, or
    [sbull] If an engine has failed or been shut down earlier in the 
flight.
    This maximum go-around thrust is the same as that used to show 
compliance with the approach-climb-gradient requirement of Sec.  
25.121(d). If the ATTCS is not operating, selection of go-around thrust 
will result in a lower thrust level.
    The part 25 standards for ATTCS, contained in Sec.  25.904 
[Automatic takeoff thrust control system (ATTCS) and Appendix I], 
specifically restrict performance credit for ATTCS to takeoff. 
Expanding the scope of the standards to include other phases of flight, 
such as go-around, was considered when the standards were issued but 
was not accepted because of the effect on the flightcrew's workload. As 
stated in the preamble to amendment 25-62:

    In regard to ATTCS credit for approach climb and go-around 
maneuvers, current regulations preclude a higher thrust for the 
approach climb [Sec.  25.121(d)] than for the landing climb [Sec.  
25.119]. The workload required for the flightcrew to monitor and 
select from multiple in-flight thrust settings in the event of an 
engine failure during a critical point in the approach, landing, or 
go-around operations is excessive. Therefore, the FAA does not agree 
that the scope of the amendment should be changed to include the use 
of ATTCS for anything except the takeoff phase.'' (Refer to 52 FR 
43153, November 9, 1987.)


[[Page 52686]]


    The ATTCS incorporated on Embraer Model ERJ-170 series airplanes 
allows the pilot to use the same power setting procedure during a go-
around, regardless of whether or not an engine fails. In either case, 
the pilot obtains go-around power by moving the throttles into the 
forward (takeoff/go-around) throttle detent. Since the ATTCS is 
permanently armed for the go-around phase, it will function 
automatically following an engine failure and advance the remaining 
engine to the ATTCS thrust level. This design adequately addresses the 
concerns about pilot workload which were discussed in the preamble to 
Amendment 25-62.
    The system design allows the pilot to enable or disable the ATTCS 
function for takeoff. If the pilot enables ATTCS, a white ``ATTCS'' 
icon will be displayed on the Engine Indication and Crew Alerting 
System (EICAS) beneath the thrust mode indication on the display. This 
white icon indicates to the pilot that the ATTCS function is enabled. 
When the throttle lever is put in the TO/GA (takeoff/go-around) detent 
position, the white icon turns green, indicating to the pilot that the 
ATTCS is armed. If the pilot disables the ATTCS function for takeoff, 
no indication appears on the EICAS.
    Regardless of whether the ATTCS is enabled for takeoff, it is 
automatically enabled when the airplane reaches the end of the take-off 
phase (that is, the thrust lever is below the TO/GA position and the 
altitude is greater than 1,700 feet above the ground, 5 minutes have 
elapsed since lift-off, or the airplane speed is greater than 140 
knots).
    During climb, cruise and descent, when the throttle is not in the 
TO/GA position, the ATTCS indication is inhibited. During descent and 
approach to land, until the thrust management system go-around mode is 
enabled--either by crew action or automatically when the landing gear 
are down and locked and flaps are extended--the ATTCS indication 
remains inhibited.
    When the go-around thrust mode is enabled, unless the ATTCS system 
has failed, the white ``ATTCS'' icon will again be shown on the EICAS, 
indicating to the pilot that the system is enabled and in an operative 
condition in the event a go-around is necessary. If the thrust lever is 
subsequently placed in the TO/GA position, the ATTCS icon turns green, 
indicating that the system is armed and ready to operate.
    If an engine fails during the go-around or during a one-engine-
inoperative go-around in which an engine had been shut down or 
otherwise made inoperative earlier in the flight, the EICAS indication 
will be GA RSV (go-around reserve) when the thrust levers are placed in 
the TO/GA position. The GA RSV indication means that the maximum go-
around thrust under the ambient conditions has been commanded.
    The propulsive thrust used to determine compliance with the 
approach climb requirements of Sec.  25.121(d) is limited to the lesser 
of (i) the thrust provided by the ATTCS system, or (ii) 111 percent of 
the thrust resulting from the initial thrust setting with the ATTCS 
system failing to perform its uptrim function and without action by the 
crew to reset thrust. This requirement limits the adverse performance 
effects of a failure of the ATTCS and ensures adequate all-engines-
operating go-around performance.
    These special conditions require a showing of compliance with the 
provisions of Sec.  25.904 and Appendix I applicable to the approach 
climb and go-around maneuvers.
    The definition of a critical time interval for the approach climb 
case is of primary importance. During this time it must be extremely 
improbable to violate a flight path derived from the gradient 
requirement of Sec.  25.121(d). That gradient requirement implies a 
minimum one-engine-inoperative flight path with the airplane in the 
approach configuration. The engine may have been inoperative before 
initiating the go-around, or it may become inoperative during the go-
around. The definition of the critical time interval must consider both 
possibilities.

Discussion of Comments

    Notice of proposed special conditions No. 25-03-03-SC for the 
Embraer Model ERJ-170 series airplane was published in the Federal 
Register on April 23, 2003 (68 FR 19958) and a Supplemental notice of 
proposed special conditions was published on June 5, 2003 (68 FR 
33659). No comments were received after publication of the initial 
notice or the supplemental notice, and the special conditions are 
adopted as proposed.

Applicability

    As discussed above, these special conditions are applicable to the 
Embraer Model ERJ-170 series airplanes. Should Embraer apply at a later 
date for a change to the type certificate to include another model 
incorporating the same novel or unusual design features, these special 
conditions would apply to that model as well under the provisions of 
Sec.  21.101(a)(1), Amendment 21-69, effective September 16, 1991.
    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 Embraer 
Model ERJ-170 series airplane is imminent, the FAA finds that good 
cause exists to make these special conditions effective upon issuance.

Conclusion

    This action affects only certain novel or unusual design features 
on the Embraer Model ERJ-170 series airplanes. It is not a rule of 
general applicability, and it affects only the applicant who applied to 
the FAA for approval of these features on the airplane.

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, the Federal Aviation Administration (FAA) issues the 
following special conditions as part of the type certification basis 
for Embraer Model ERJ-170 series airplanes.

I. Electronic Flight Control System

    In addition to compliance with Sec. Sec.  25.143, 25.671 and 
25.672, when a flight condition exists where, without being commanded 
by the crew, control surfaces are coming so close to their limits that 
return to the normal flight envelope and (or) continuation of safe 
flight requires a specific crew action, a suitable flight control 
position annunciation shall be provided to the crew, unless other 
existing indications are found adequate or sufficient to prompt that 
action.

    Note: The term suitable also indicates an appropriate balance 
between nuisance and necessary operation.


II. Automatic Takeoff Thrust Control System (ATTCS)

    To use the thrust provided by the ATTCS to determine the approach 
climb performance limitations, the Embraer Model ERJ-170 series 
airplane must comply with the requirements of Sec.  25.904 and Appendix 
I, including the following requirements pertaining to the go-around 
phase of flight:
1. Definitions
    (a) TOGA--(Take Off/Go-Around). Throttle lever in takeoff or go-
around position.

[[Page 52687]]

    (b) Automatic Takeoff Thrust Control System--(ATTCS). The Embraer 
Model ERJ-170 series ATTCS is defined as the entire automatic system 
available in takeoff when selected by the pilot and always in go-around 
mode; including all devices, both mechanical and electrical, that sense 
engine failure, transmit signals, and actuate fuel controls or power 
levers or increase engine power by other means on operating engines to 
achieve scheduled thrust or power increases and to furnish cockpit 
information on system operation.
    (c) Critical Time Interval. The definition of the Critical Time 
Interval in appendix I, Sec.  I25.2(b) shall be expanded to include the 
following:
    (1) When conducting an approach for landing using ATTCS, the 
critical time interval is defined as 120 seconds. A shorter time 
interval may be used if justified by a rational analysis. An accepted 
analysis that has been used on past aircraft certification programs is 
as follows:
    (i) The critical time interval begins at a point on a 2.5 degree 
approach glide path from which, assuming a simultaneous engine and 
ATTCS failure, the resulting approach climb flight path intersects a 
flight path originating at a later point on the same approach path 
corresponding to the part 25 one-engine-inoperative approach climb 
gradient. The period of time from the point of simultaneous engine and 
ATTCS failure to the intersection of these flight paths must be no 
shorter than the time interval used in evaluating the critical time 
interval for takeoff, beginning from the point of simultaneous engine 
and ATTCS failure and ending upon reaching a height of 400 feet.
    (ii) The critical time interval ends at the point on a minimum 
performance, all-engines-operating go-around flight path from which, 
assuming a simultaneous engine and ATTCS failure, the resulting minimum 
approach climb flight path intersects a flight path corresponding to 
the part 25 minimum one-engine-inoperative approach-climb-gradient. The 
all-engines-operating go-around flight path and the part 25 one-engine-
inoperative, approach-climb-gradient flight path originate from a 
common point on a 2.5 degree approach path. The period of time from the 
point of simultaneous engine and ATTCS failure to the intersection of 
these flight paths must be no shorter than the time interval used in 
evaluating the critical time interval for the takeoff beginning from 
the point of simultaneous engine and ATTCS failure and ending upon 
reaching a height of 400 feet.
    (2) The critical time interval must be determined at the altitude 
resulting in the longest critical time interval for which one-engine-
inoperative approach climb performance data are presented in the 
Airplane Flight Manual (AFM).
    (3) The critical time interval is illustrated in the following 
figure:
[GRAPHIC] [TIFF OMITTED] TR05SE03.000

    The engine and ATTCS failed time interval must be no shorter than 
the time interval from the point of simultaneous engine and ATTCS 
failure to a height of 400 feet used to comply with I25.2(b) for ATTCS 
use during takeoff.
    2. Performance and System Reliability Requirements.
    The applicant must comply with the following performance and ATTCS 
reliability requirements:
    (a) An ATTCS failure or combination of failures in the ATTCS during 
the critical time interval:
    (1) Shall not prevent the insertion of the maximum approved go-
around thrust or power or must be shown to be an improbable event.
    (2) Shall not result in a significant loss or reduction in thrust 
or power or must be shown to be an extremely improbable event.
    (b) The concurrent existence of an ATTCS failure and an engine 
failure during the critical time interval must be shown to be extremely 
improbable.
    (c) All applicable performance requirements of part 25 must be met 
with an engine failure occurring at the most critical point during go-
around with the ATTCS system functioning.
    (d) The probability analysis must include consideration of ATTCS 
failure occurring after the time at which the flightcrew last verifies 
that the ATTCS is in a condition to operate until the beginning of the 
critical time interval.

[[Page 52688]]

    (e) The propulsive thrust obtained from the operating engine after 
failure of the critical engine during a go-around used to show 
compliance with the one-engine-inoperative climb requirements of Sec.  
25.121(d) may not be greater than the lesser of:
    (i) The actual propulsive thrust resulting from the initial setting 
of power or thrust controls with the ATTCS functioning; or
    (ii) 111 percent of the propulsive thrust resulting from the 
initial setting of power or thrust controls with the ATTCS failing to 
reset thrust or power and without any action by the crew to reset 
thrust or power.
    3. Thrust Setting.
    (a) The initial go-around thrust setting on each engine at the 
beginning of the go-around phase may not be less than any of the 
following:
    (1) That required to permit normal operation of all safety-related 
systems and equipment dependent upon engine thrust or power lever 
position; or
    (2) That shown to be free of hazardous engine response 
characteristics when thrust or power is advanced from the initial go-
around position to the maximum approved power setting.
    (b) For approval of an ATTCS for go-around, the thrust setting 
procedure must be the same for go-arounds initiated with all engines 
operating as for go-arounds initiated with one engine inoperative.
    4. Powerplant Controls.
    (a) In addition to the requirements of Sec.  25.1141, no single 
failure or malfunction, or probable combination thereof, of the ATTCS, 
including associated systems, may cause the failure of any powerplant 
function necessary for safety.
    (b) The ATTCS must be designed to accomplish the following:
    (1) Following any single engine failure during go around: Apply 
thrust or power on the operating engine(s) to achieve the maximum 
approved go-around thrust without exceeding engine operating limits;
    (2) Permit manual decrease or increase in thrust or power up to the 
maximum go-around thrust approved for the airplane under existing 
conditions through the use of the power lever. For airplanes equipped 
with limiters that automatically prevent engine operating limits from 
being exceeded under existing ambient conditions, other means may be 
used to increase the thrust in the event of an ATTCS failure. Any such 
means must be located on or forward of the power levers; be easily 
identified and operated under all operating conditions by a single 
action of either pilot with the hand that is normally used to actuate 
the power levers, and meet the requirements of Sec.  25.777 (a), (b), 
and (c);
    (3) Provide a means to verify to the flightcrew before beginning an 
approach for landing that the ATTCS is in a condition to operate 
(unless it can be demonstrated that an ATTCS failure combined with an 
engine failure during an entire flight is extremely improbable); and
    (4) Provide a means for the flightcrew to deactivate the automatic 
function. This means must be designed to prevent inadvertent 
deactivation.
    5. In addition to the requirements of Sec.  25.1305, the following 
requirements pertaining to powerplant instruments must be met:
    (a) A means must be provided to indicate when the ATTCS is in the 
armed or ready condition; and
    (b) If the inherent flight characteristics of the airplane do not 
provide adequate warning that an engine has failed, a warning system 
that is independent of the ATTCS must be provided to give the pilot a 
clear warning of any engine failure during go-around.

    Issued in Renton, Washington, on August 15, 2003.
Kyle Olsen,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 03-22565 Filed 9-4-03; 8:45 am]
BILLING CODE 4910-13-P