11560 Federal Register / Vol. 78, No. 33 / Tuesday, February 19, 2013 / Rules and Regulations 

capability below the level required by 

14 CFR 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, in lieu of detection and 

indication systems to achieve the 

objective of this requirement. These 

certification maintenance requirements 

must be limited to components that 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 factor of safety between the airplane 

strength and the loads of Subpart C 

below 1.25, or flutter margins below V′′, 

must be signaled to the flightcrew 

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 

structural performance, then the 

provisions of these special conditions 

must be met, including the provisions of 

paragraph 2(a) for the dispatched 

condition, and paragraph 2(b) for 

subsequent failures. Expected 

operational limitations may be taken 

into account in establishing Pj as the 

probability of failure occurrence for 

determining the safety margin in Figure 

1 of these special conditions. 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 of these special 

conditions. 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 February 

12, 2013. 

Ali Bahrami, 

Manager, Transport Airplane Directorate, 

Aircraft Certification Service. 

[FR Doc. 2013–03678 Filed 2–15–13; 8:45 am] 

BILLING CODE 4910–13–P 

DEPARTMENT OF TRANSPORTATION 

Federal Aviation Administration 

14 CFR Part 25 

[Docket No. FAA–2012–1218; Special 

Conditions No. 25–483–SC] 

Special Conditions: Embraer S.A., 

Model EMB–550 Airplane; Electronic 

Flight Control System: LateralDirectional and Longitudinal Stability 

and Low Energy Awareness 

AGENCY: Federal Aviation 

Administration (FAA), DOT. 

ACTION: Final special conditions. 

SUMMARY: These special conditions are 

issued for the Embraer S.A. Model 

EMB–550 airplane. This airplane will 

have a novel or unusual design 

feature(s) associated with an electronic 

flight control system with respect to 

lateral-directional and longitudinal 

stability and low energy awareness. 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: Effective date: March 21, 2013. 

FOR FURTHER INFORMATION CONTACT: Joe 

Jacobsen, FAA, Airplane and Flight 

Crew Interface Branch, ANM–111 

Transport Airplane Directorate, Aircraft 

Certification Service, 1601 Lind Avenue 

SW., Renton, Washington 98057–3356; 

telephone 425–227–2011; facsimile 

425–227–1149. 

SUPPLEMENTARY INFORMATION: 

Background 

On May 14, 2009, Embraer S.A. 

applied for a type certificate for their 

new Model EMB–550 airplane. The 

Model EMB–550 airplane is the first of 

a new family of jet airplanes designed 

for corporate flight, fractional, charter, 

and private owner operations. The 

aircraft has a conventional configuration 

with low wing and T-tail empennage. 

The primary structure is metal with 

composite empennage and control 

surfaces. The Model EMB–550 airplane 

is designed for 8 passengers, with a 

maximum of 12 passengers. It is 

equipped with two Honeywell 

HTF7500–E medium bypass ratio 

turbofan engines mounted on aft 

fuselage pylons. Each engine produces 

approximately 6,540 pounds of thrust 

for normal takeoff. The primary flight 

controls consist of hydraulically 

powered fly-by-wire elevators, aileron 

and rudder, controlled by the pilot or 

copilot sidestick. 

The Embraer S.A. Model EMB–550 

airplane has a flight control design 

feature within the normal operational 

envelope in which sidestick deflection 

in the roll axis commands roll rate. As 

a result, the stick force in the roll axis 

will be zero (neutral stability) during the 

straight, steady sideslip flight maneuver 

required by Title 14, Code of Federal 

Regulations (14 CFR) 25.177(c) and will 

not be ‘‘substantially proportional to the 

angle of sideslip’’ as required by the 

rule. 

The longitudinal flight control laws 

for the Model EMB–550 airplane 

provide neutral static stability within 

the normal operational envelope; 

therefore, the airplane design does not 

comply with the static longitudinal 

stability requirements of §§ 25.171, 

25.173, and 25.175. 

Static longitudinal stability provides 

awareness to the flightcrew of a low 

energy state (i.e., low speed and thrust 

at low altitude). Recovery from a low 

energy state may become hazardous 

when associated with a low altitude and 

performance-limiting conditions. These 

low energy situations must therefore be 

avoided, and pilots must be given 

adequate cues when approaching such 

situations. 

Type Certification Basis 

Under the provisions of 14 CFR 21.17, 

Embraer S.A. must show that the Model 

EMB–550 airplane meets the applicable 

provisions of part 25, as amended by 

Amendments 25–1 through 25–127 

thereto. 

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 Model EMB–550 airplane 

because of a novel or unusual design 

feature, special conditions are 

prescribed under the provisions of 

§ 21.16. 

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, the special 

conditions would also apply to the other 

model under § 21.101. 


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Federal Register / Vol. 78, No. 33 / Tuesday, February 19, 2013 / Rules and Regulations 11561 

In addition to the applicable 

airworthiness regulations and special 

conditions, the Model EMB–550 

airplane 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 under 

section 611 of Public Law 92–574, the 

‘‘Noise Control Act of 1972.’’ 

The FAA issues special conditions, as 

defined in 14 CFR part 11.19, in 

accordance with § 11.38, and they 

become part of the type-certification 

basis under § 21.17(a)(2). 

Novel or Unusual Design Features 

The Model EMB–550 airplane will 

incorporate the following novel or 

unusual design features: 

(1) Lateral-Directional Static Stability: 

The electronic flight control system on 

the Model EMB–550 airplane contains 

fly-by-wire control laws that can result 

in neutral lateral-directional static 

stability; therefore, the conventional 

requirements in §§ 25.171, 25.173, 

25.175, and 25.177 are not met. 

Positive static directional stability is 

the tendency to recover from a skid with 

the rudder free. Positive static lateral 

stability is the tendency to raise the low 

wing in a sideslip with the aileron 

controls free. These control criteria are 

intended to accomplish all of the 

following: 

• Provide additional cues of 

inadvertent sideslips and skids through 

control force changes, 

• Ensure that short periods of 

unattended operation do not result in 

any significant changes in yaw or bank 

angle, 

• Provide predictable roll and yaw 

response, and 

• Provide an acceptable level of pilot 

attention and workload to attain and 

maintain a coordinated turn. 

The Flight Test Harmonization 

Working Group recommended a rule 

and advisory material change for 

§ 25.177, Static lateral-directional 

stability, which was adopted at 

Amendment 25–135 (76 FR 74654, 

December 1, 2011), effective January 30, 

2012. (This amendment is not in the 

Model EMB–550 certification basis.) 

That harmonized text formed the basis 

for these special conditions. 

(2) Longitudinal Static Stability: Static 

longitudinal stability on airplanes with 

mechanical links to the pitch control 

surface means that a pull force on the 

controller will result in a reduction in 

speed relative to the trim speed, and a 

push force will result in higher than 

trim speed. Longitudinal stability is 

required by the regulations for the 

following reasons: 

• Speed change cues are provided to 

the pilot through increased and 

decreased forces on the controller. 

• Short periods of unattended control 

of the airplane do not result in 

significant changes in attitude, airspeed 

or load factor. 

• A predictable pitch response is 

provided to the pilot. 

• An acceptable level of pilot 

attention (workload) to attain and 

maintain trim speed and altitude is 

provided to the pilot. 

• Longitudinal stability provides gust 

stability. 

The pitch control movement of the 

sidestick on the Model EMB–550 

airplane is designed to be a normal load 

factor or g command that results in an 

initial movement of the elevator surface 

to attain the commanded load factor 

that’s then followed by integrated 

movement of the stabilizer and elevator 

to automatically trim the airplane to a 

neutral, 1g, stick-free stability. The 

flight path commanded by the initial 

sidestick input will remain, stick-free, 

until the pilot gives another command. 

This control function is applied during 

‘‘normal’’ control law within the speed 

range from initiation of the angle of 

attack protection limit, to VMO/MMO. 

Once outside this speed range, the 

control laws introduce the conventional 

longitudinal static stability as described 

above. 

As a result of neutral static stability, 

the Model EMB–550 airplane does not 

meet the 14 CFR part 25 requirements 

for static longitudinal stability. 

(3) Low Energy Awareness: Past 

experience on airplanes fitted with a 

flight control system providing neutral 

longitudinal stability shows there is 

insufficient feedback cues to the pilot of 

excursion below normal operational 

speeds. The maximum angle of attack 

protection system limits the airplane 

angle of attack and prevents stall during 

normal operating speeds, but this 

system is not sufficient to prevent stall 

at low speed excursions below normal 

operational speeds. Until intervention, 

there are no stability cues since the 

airplane remains trimmed. Additionally, 

feedback from the pitching moment due 

to thrust variation is reduced by the 

flight control laws. Recovery from a low 

speed excursion may become hazardous 

when the low speed situation is 

associated with a low altitude and with 

the engines at low thrust or with 

performance-limiting conditions. 

Discussion 

In the absence of positive lateral 

stability, the curve of lateral control 

surface deflections against sideslip 

angle should be in a conventional sense, 

and reasonably in harmony with rudder 

deflection during steady heading 

sideslip maneuvers. 

Since conventional relationships 

between stick forces and control surface 

displacements do not apply to the ‘‘load 

factor command’’ flight control system 

on the Model EMB–550 airplane, 

longitudinal stability characteristics 

should be evaluated by assessing the 

airplane handling qualities during 

simulator and flight test maneuvers 

appropriate to operation of the airplane. 

This may be accomplished by using the 

Handling Qualities Rating Method 

presented in Appendix 7 of Advisory 

Circular (AC) 25–7B, Flight Test Guide, 

dated March 29, 2011, or an acceptable 

alternative method proposed by 

Embraer S.A. Important considerations 

are as follows: 

• Adequate speed control without 

creating excessive pilot workload, 

• Acceptable high and low speed 

protection, and 

• Providing adequate cues to the pilot 

of significant speed excursions beyond 

VMO/MMO, and low speed awareness 

flight conditions. 

The airplane should provide adequate 

awareness cues to the pilot of a low 

energy (i.e., a low speed, low thrust, or 

low height) state to ensure that the 

airplane retains sufficient energy to 

recover when flight control laws 

provide neutral longitudinal stability 

significantly below the normal operating 

speeds. This may be accomplished as 

follows: 

• Adequate low speed/low thrust 

cues at low altitude may be provided by 

a strong positive static stability force 

gradient (1 pound per 6 knots applied 

through the sidestick), or 

• The low energy awareness may be 

provided by an appropriate warning 

with the following characteristics: 

Æ It should be unique, unambiguous, 

and unmistakable. 

Æ It should be active at appropriate 

altitudes and in appropriate 

configurations (e.g., at low altitude, in 

the approach and landing 

configurations). 

Æ It should be sufficiently timely to 

allow recovery to a stabilized flight 

condition inside the normal flight 

envelope while maintaining the desired 

flight path and without entering the 

flight controls angle-of-attack protection 

mode. 

Æ It should not be triggered during 

normal operation, including operation 

in moderate turbulence for 

recommended maneuvers at 

recommended speeds. 


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11562 Federal Register / Vol. 78, No. 33 / Tuesday, February 19, 2013 / Rules and Regulations 

Æ The pilot should only be able to 

cancel it by achieving a higher energy 

state. 

Æ An adequate hierarchy should exist 

among the warnings so that the pilot is 

not confused and led to take 

inappropriate recovery action if 

multiple warnings occur. 

Simulators and flight test should 

evaluate global energy awareness and 

ensure that low energy cues are not a 

nuisance in all take-off and landing 

altitude ranges for which certification is 

requested. These evaluations should 

include all relevant combinations of 

weight, center of gravity position, 

configuration, airbrakes position, and 

available thrust, including reduced and 

derated take-off thrust operations and 

engine failure cases. A sufficient 

number of tests should be conducted to 

assess the level of energy awareness and 

the effects of energy management errors. 

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. 

Discussion of Comments 

Notice of proposed special conditions 

No. 25–12–11–SC for the Embraer S.A. 

Model EMB–550 airplanes was 

published in the Federal Register on 

November 20, 2012 (77 FR 69573). No 

comments were received, and the 

special conditions are adopted as 

proposed. 

Applicability 

As discussed above, these special 

conditions are applicable to the Model 

EMB–550 airplane. Should Embraer 

S.A. apply at a later date for a change 

to the type certificate to include another 

model incorporating the same novel or 

unusual design feature, the special 

conditions would apply to that model as 

well. 

Conclusion 

This action affects only certain novel 

or unusual design features on one model 

of airplanes. It is not a rule of general 

applicability. 

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 

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 Model EMB–550 

airplanes. 

1. Electronic Flight Control System: 

Lateral-Directional and Longitudinal 

Stability and Low Energy Awareness. In 

lieu of the requirements of §§ 25.171, 

25.173, 25.175, and 25.177, the 

following special conditions apply: 

a. The airplane must be shown to 

have suitable static lateral, directional, 

and longitudinal stability in any 

condition normally encountered in 

service, including the effects of 

atmospheric disturbance. The showing 

of suitable static lateral, directional, and 

longitudinal stability must be based on 

the airplane handling qualities, 

including pilot workload and pilot 

compensation, for specific test 

procedures during the flight test 

evaluations. 

b. The airplane must provide 

adequate awareness to the pilot of a low 

energy (e.g., low speed, low thrust, or 

low height) state when fitted with flight 

control laws presenting neutral 

longitudinal stability significantly 

below the normal operating speeds. 

‘‘Adequate awareness’’ means warning 

information must be provided to alert 

the crew of unsafe operating conditions 

and to enable them to take appropriate 

corrective action. 

c. The static directional stability (as 

shown by the tendency to recover from 

a skid with the rudder free) must be 

positive for any landing gear and flap 

position and symmetrical power 

condition, at speeds from 1.13 VSR1, up 

to VFE, VLE, or VFC/MFC (as appropriate). 

d. The static lateral stability (as 

shown by the tendency to raise the low 

wing in a sideslip with the aileron 

controls free) for any landing gear and 

wing-flap position and symmetric 

power condition, may not be negative at 

any airspeed (except that speeds higher 

than VFE need not be considered for 

wing-flaps extended configurations nor 

speeds higher than VLE for landing gear 

extended configurations) in the 

following airspeed ranges: 

i. From 1.13 VSR1 to VMO/MMO. 

ii. From VMO/MMO to VFC/MFC, unless 

the divergence is – 

1. Gradual; 

2. Easily recognizable by the pilot; 

and 

3. Easily controllable by the pilot. 

e. In straight, steady sideslips over the 

range of sideslip angles appropriate to 

the operation of the airplane, but not 

less than those obtained with one-half of 

the available rudder control movement 

(but not exceeding a rudder control 

force of 180 pounds), rudder control 

movements and forces must be 

substantially proportional to the angle 

of sideslip in a stable sense; and the 

factor of proportionality must lie 

between limits found necessary for safe 

operation. This requirement must be 

met for the configurations and speeds 

specified in paragraph (c) of this 

section. 

f. For sideslip angles greater than 

those prescribed by paragraph (e) of this 

section, up to the angle at which full 

rudder control is used or a rudder 

control force of 180 pounds is obtained, 

the rudder control forces may not 

reverse, and increased rudder deflection 

must be needed for increased angles of 

sideslip. Compliance with this 

requirement must be shown using 

straight, steady sideslips, unless full 

lateral control input is achieved before 

reaching either full rudder control input 

or a rudder control force of 180 pounds; 

a straight, steady sideslip need not be 

maintained after achieving full lateral 

control input. This requirement must be 

met at all approved landing gear and 

wing-flap positions for the range of 

operating speeds and power conditions 

appropriate to each landing gear and 

wing-flap position with all engines 

operating. 

Issued in Renton, Washington, on February 

12, 2013. 

Ali Bahrami, 

Manager, Transport Airplane Directorate, 

Aircraft Certification Service. 

[FR Doc. 2013–03677 Filed 2–15–13; 8:45 am] 

BILLING CODE 4910–13–P 

DEPARTMENT OF TRANSPORTATION 

Federal Aviation Administration 

14 CFR Part 25 

[Docket No. FAA–2012–1215; Special 

Conditions No. 25–12–482–SC] 

Special Conditions: Embraer S.A., 

Model EMB–550 Airplanes; Flight 

Envelope Protection: High Speed 

Limiting 

AGENCY: Federal Aviation 

Administration (FAA), DOT. 

ACTION: Final special conditions. 

SUMMARY: These special conditions are 

issued for the Embraer S.A. Model 

EMB–550 airplane. This airplane will 

have a novel or unusual design feature, 

specifically an electronic flight control 

system which contains fly-by-wire 

control laws, including envelope 

protections, for the overspeed protection 

and roll limiting function. The 

applicable airworthiness regulations do 

not contain adequate or appropriate 

safety standards for this design feature. 

These special conditions contain the 


sroberts on DSK5SPTVN1PROD with RULES