Federal Register / Vol. 72, No. 47 / Monday, March 12, 2007 / Proposed Rules 10941 

of Federal Regulations to read as 

follows: 

PART 627—TITLE IV CONSERVATORS, 

RECEIVERS, AND VOLUNTARY 

LIQUIDATIONS 

1. The authority citation for part 627 

continues to read as follows: 

Authority: Secs. 4.2, 5.9, 5.10, 5.17, 5.51, 

5.58, 5.61 of the Farm Credit Act (12 U.S.C. 

2183, 2243, 2244, 2252, 2277a, 2277a–7, 

2277a–10). 

Subpart B—Receivers and 

Receiverships 

2. Revise § 627.2750(h) to read as 

follows: 

§ 627.2750 Priority of claims—banks. 

* * * * * 

(h) All claims of holders of 

consolidated and System-wide bonds 

and all claims of the other Farm Credit 

banks arising from their payments on 

consolidated and System-wide bonds 

pursuant to 12 U.S.C. 2155 or pursuant 

to an agreement among the banks to 

reallocate the payments, provided the 

agreement is in writing and approved by 

the Farm Credit Administration. 

* * * * * 

§ 627.2755 [Amended] 

3. Amend § 627.2755(a) by removing 

the words ‘‘described in § 627.2745’’ in 

the last sentence. 

Dated: March 7, 2007. 

Roland E. Smith, 

Secretary, Farm Credit Administration Board. 

[FR Doc. E7–4427 Filed 3–9–07; 8:45 am] 

BILLING CODE 6705–01–P 

DEPARTMENT OF TRANSPORTATION 

Federal Aviation Administration 

14 CFR Part 25 

[Docket No. NM362 Special Conditions No. 

25–06–15–SC] 

Special Conditions: Boeing Model 787–

8 Airplane; Interaction of Systems And 

Structures, Electronic Flight Control 

System—Control Surface Awareness, 

High Intensity Radiated Fields (HIRF) 

Protection, Limit Engine Torque Loads 

for Sudden Engine Stoppage, and 

Design Roll Maneuver Requirement 

AGENCY: Federal Aviation 

Administration (FAA), DOT. 

ACTION: Notice of proposed special 

conditions. 

SUMMARY: This notice proposes special 

conditions for the Boeing Model 787–8 

airplane. This airplane 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 include 

electronic flight control systems and 

high bypass engines. These special 

conditions also pertain to the effects of 

such novel or unusual design features, 

such as effects on the structural 

performance of the airplane. Finally, 

these special conditions pertain to 

effects of certain conditions on these 

novel or unusual design features, such 

as the effects of high intensity radiated 

fields (HIRF). Additional special 

conditions will be issued for other novel 

or unusual design features of the Boeing 

Model 787–8 airplanes. 

DATES: Comments must be received on 

or before April 26, 2007. 

ADDRESSES: Comments on this proposal 

may be mailed in duplicate to: Federal 

Aviation Administration, Transport 

Airplane Directorate, Attention: Rules 

Docket (ANM–113), Docket No. NM362, 

1601 Lind Avenue, SW., Renton, 

Washington 98057–3356; or delivered in 

duplicate to the Transport Airplane 

Directorate at the above address. All 

comments must be marked Docket No. 

NM362. 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: 

Meghan Gordon, FAA, Standardization 

Branch, ANM–113, Transport Airplane 

Directorate, Aircraft Certification 

Service, 1601 Lind Avenue, SW., 

Renton, Washington 98057–3356; 

telephone (425) 227–2138; facsimile 

(425) 227–1149. 

SUPPLEMENTARY INFORMATION: 

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 proposed 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 notice 

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 the proposed special 

conditions based on comments we 

receive. 

If you want the FAA to acknowledge 

receipt of your comments on this 

proposal, 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 back to you. 

Background 

On March 28, 2003, Boeing applied 

for an FAA type certificate for its new 

Boeing Model 787–8 passenger airplane. 

The Boeing Model 787–8 airplane will 

be an all-new, two-engine jet transport 

airplane with a two-aisle cabin. The 

maximum takeoff weight will be 

476,000 pounds, with a maximum 

passenger count of 381 passengers. 

Type Certification Basis 

Under provisions of 14 CFR 21.17, 

Boeing must show that Boeing Model 

787–8 airplanes (hereafter referred to as 

‘‘the 787’’) meet the applicable 

provisions of 14 CFR part 25, as 

amended by Amendments 25–1 through 

25–117, except §§ 25.809(a) and 25.812, 

which will remain at Amendment 25–

115. If the Administrator finds that the 

applicable airworthiness regulations do 

not contain adequate or appropriate 

safety standards for the 787 because of 

a novel or unusual design feature, 

special conditions are prescribed under 

provisions of 14 CFR 21.16. 

In addition to the applicable 

airworthiness regulations and special 

conditions, the 787 must comply with 

the fuel vent and exhaust emission 

requirements of 14 CFR part 34 and the 

noise certification requirements of part 

36. In addition, the FAA must issue a 

finding of regulatory adequacy pursuant 

to section 611 of Public Law 92–574, the 

‘‘Noise Control Act of 1972.’’

Special conditions, as defined in 

§ 11.19, are issued in accordance with 

§ 11.38 and become part of the type 

certification basis in accordance with 

§ 21.17(a)(2). 

Special conditions are initially 

applicable to the model for which they 

are issued. Should the type certificate 

for that model be amended later to 

include any other model that 

incorporates the same or similar novel 

or unusual design feature, the special 

conditions would also apply to the other 

model under the provisions of § 21.101. 


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Discussion of Novel or Unusual Design 

Features 

The 787 will incorporate a number of 

novel or unusual design features. 

Because of rapid improvements in 

airplane technology, the applicable 

airworthiness regulations do not contain 

adequate or appropriate safety standards 

for these design features. These 

proposed special conditions for the 787 

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. 

Most of these proposed special 

conditions are identical or nearly 

identical to those previously required 

for type certification of the Model 777 

series airplanes. 

Most of these proposed special 

conditions were derived initially from 

standardized requirements developed 

by the Aviation Rulemaking Advisory 

Committee (ARAC), comprised of 

representatives of the FAA, Europe’s 

Joint Aviation Authorities (now 

replaced by the European Aviation 

Safety Agency), and industry. In the 

case of some of these requirements, a 

draft notice of proposed rulemaking has 

been prepared but no final rule has yet 

been promulgated. 

Additional special conditions will be 

issued for other novel or unusual design 

features of the 787 in the near future. 

1. Interaction of Systems and Structures 

The 787 is equipped with systems 

that affect the airplane’s structural 

performance, either directly or as a 

result of failure or malfunction. That is, 

the airplane’s systems affect how it 

responds in maneuver and gust 

conditions, and thereby affect its 

structural capability. These systems may 

also affect the aeroelastic stability of the 

airplane. Such systems represent a 

novel and unusual feature when 

compared to the technology envisioned 

in the current airworthiness standards. 

A special condition is needed to require 

consideration of the effects of systems 

on the structural capability and 

aeroelastic stability of the airplane, both 

in the normal and in the failed state. 

This special condition requires that 

the airplane meet the structural 

requirements of subparts C and D of 14 

CFR part 25 when the airplane systems 

are fully operative. The special 

condition also requires that the airplane 

meet these requirements considering 

failure conditions. In some cases, 

reduced margins are allowed for failure 

conditions based on system reliability. 

2. Electronic Flight Control System: 

Control Surface Awareness 

With a response-command type of 

flight control system and no direct 

coupling from cockpit controller to 

control surface, such as on the 787, the 

pilot is not aware of the actual surface 

deflection position during flight 

maneuvers. These features are novel and 

unusual when compared to the state of 

technology envisioned in the 

airworthiness standards for transport 

category airplanes. These special 

conditions are meant to 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. Some unusual 

flight conditions, arising from 

atmospheric conditions or airplane or 

engine failures or both, may result in 

full or nearly full surface deflection. 

Unless the flightcrew is made aware of 

excessive deflection or impending 

control surface deflection limiting, 

piloted or auto-flight system control of 

the airplane might be inadvertently 

continued in a way that would cause 

loss of control or other unsafe handling 

or performance characteristics. 

These proposed special conditions 

require that suitable annunciation be 

provided to the flightcrew when a flight 

condition exists in which nearly full 

control surface deflection occurs. 

Suitability of such an annunciation 

must take into account that some pilotdemanded maneuvers, such as a rapid 

roll, are necessarily associated with 

intended full or nearly full control 

surface deflection. Simple alerting 

systems which would function in both 

intended or unexpected control-limiting 

situations must be properly balanced 

between providing needed crew 

awareness and avoiding nuisance 

warnings. 

3. High Intensity Radiated Fields (HIRF) 

Protection 

The 787 will use electrical and 

electronic systems which perform 

critical functions. These systems may be 

vulnerable to high-intensity radiated 

fields (HIRF) external to the airplane. 

There is no specific regulation that 

addresses requirements for protection of 

electrical and electronic systems from 

HIRF. Increased power levels from radio 

frequency transmitters and use of 

sensitive avionics /electronics and 

electrical systems to command and 

control the airplane have made it 

necessary to provide adequate 

protection. 

To ensure that a level of safety is 

achieved that is equivalent to that 

intended by the regulations 

incorporated by reference, the proposed 

special conditions are needed for the 

787. These proposed special conditions 

require that avionics/electronics and 

electrical systems that perform critical 

functions be designed and installed to 

preclude component damage and 

interruption of function because of 

HIRF. 

High-power radio frequency 

transmitters for radio, radar, television, 

and satellite communications can 

adversely affect operations of airplane 

electrical and electronic systems. 

Therefore, immunity of critical 

avionics/electronics and electrical 

systems to HIRF must be established. 

Based on surveys and analysis of 

existing HIRF emitters, adequate 

protection from HIRF exists if airplane 

system immunity is demonstrated when 

exposed to the HIRF environments in 

either paragraph (a) OR (b) below: 

(a) A minimum environment of 100 

volts rms (root-mean-square) per meter 

electric field strength from 10 KHz to 18 

GHz. 

(1) System elements and their 

associated wiring harnesses must be 

exposed to the environment without 

benefit of airframe shielding. 

(2) Demonstration of this level of 

protection is established through system 

tests and analysis. 

(b) An environment external to the 

airframe of the field strengths shown in 

the table below for the frequency ranges 

indicated. Immunity to both peak and 

average field strength components from 

the table must be demonstrated. 

Frequency 

Field strength 

(volts per meter) 

Peak Average 

10 kHz–100 kHz ....... 50 50 

100 kHz–500 kHz ..... 50 50 

500 kHz–2 MHz ........ 50 50 

2 MHz–30 MHz ......... 100 100 

30 MHz–70 MHz ....... 50 50 

70 MHz–100 MHz ..... 50 50 

100 MHz–200 MHz ... 100 100 

200 MHz–400 MHz ... 100 100 

400 MHz–700 MHz ... 700 50 

700 MHz–1 GHz ....... 700 100 

1 GHz–2 GHz ........... 2000 200 

2 GHz–4 GHz ........... 3000 200 

4 GHz–6 GHz ........... 3000 200 

6 GHz–8 GHz ........... 1000 200 

8 GHz–12 GHz ......... 3000 300 

12 GHz–18 GHz ....... 2000 200 

18 GHz–40 GHz ....... 600 200 

Field strengths are expressed in terms of 

peak root-mean-square (rms) values over the 

complete modulation period. 

The environment levels identified 

above are the result of an FAA review 

of existing studies on the subject of 

HIRF and of the work of the 


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1A nonlinearity is a situation where output does 

not change in the same proportion as input. 

Electromagnetic Effects Harmonization 

Working Group of ARAC. 

4. Limit Engine Torque Loads for 

Sudden Engine Stoppage 

The 787 will have high-bypass 

engines with a chord-swept fan 112 

inches in diameter. Engines of this size 

were not envisioned when § 25.361, 

pertaining to loads imposed by engine 

seizure, was adopted in 1965. Worst 

case engine seizure events become 

increasingly more severe with 

increasing engine size because of the 

higher inertia of the rotating 

components. 

Section 25.361(b)(1) requires that for 

turbine engine installations, the engine 

mounts and the supporting structures 

must be designed to withstand a ‘‘limit 

engine torque load imposed by sudden 

engine stoppage due to malfunction or 

structural failure.’’ Limit loads are 

expected to occur about once in the 

lifetime of any airplane. Section 25.305 

requires that supporting structures be 

able to support limit loads without 

detrimental permanent deformation, 

meaning that supporting structures 

should remain serviceable after a limit 

load event. 

Since adoption of § 25.361(b)(1), the 

size, configuration, and failure modes of 

jet engines have changed considerably. 

Current engines are much larger and are 

designed with large bypass fans. In the 

event of a structural failure, these 

engines are capable of producing much 

higher transient loads on the engine 

mounts and supporting structures. 

As a result, modern high bypass 

engines are subject to certain rare-butsevere engine seizure events. Service 

history shows that such events occur far 

less frequently than limit load events. 

Although it is important for the airplane 

to be able to support such rare loads 

safely without failure, it is unrealistic to 

expect that no permanent deformation 

will occur. 

Given this situation, ARAC has 

proposed a design standard for today’s 

large engines. For the commonlyoccurring deceleration events, the 

proposed standard requires engine 

mounts and structures to support 

maximum torques without detrimental 

permanent deformation. For the rarebut-severe engine seizure events such as 

loss of any fan, compressor, or turbine 

blade, the proposed standard requires 

engine mounts and structures to support 

maximum torques without failure, but 

allows for some deformation in the 

structure. 

The FAA concludes that modern large 

engines, including those on the 787, are 

novel and unusual compared to those 

envisioned when § 25.361(b)(1) was 

adopted and thus warrant a special 

condition. The proposed special 

condition contains design criteria 

recommended by ARAC. The ARAC 

proposal would revise the wording of 

§ 25.361(b), including §§ 25.361(b)(1) 

and (b)(2), removing language pertaining 

to structural failures and moving it to a 

separate requirement that discusses the 

reduced factors of safety that apply to 

these failures. 

5. Design Roll Maneuver Requirement 

The 787 is equipped with an 

electronic flight control system that 

provides control of the aircraft through 

pilot inputs to the flight computer. 

Current part 25 airworthiness 

regulations account for ‘‘control laws,’’

for which aileron deflection is 

proportional to control stick deflection. 

They do not address any nonlinearities 1

or other effects on aileron actuation that 

may be caused by electronic flight 

controls. Therefore, the FAA considers 

the flight control system to be a novel 

and unusual feature compared to those 

envisioned when current regulations 

were adopted. Since this type of system 

may affect flight loads, and therefore the 

structural capability of the airplane, 

special conditions are needed to address 

these effects. 

This proposed special condition 

differs from current requirements in that 

it requires that the roll maneuver result 

from defined movements of the cockpit 

roll control as opposed to defined 

aileron deflections. Also, the proposed 

special condition requires an additional 

load condition at design maneuvering 

speed (VA), in which the cockpit roll 

control is returned to neutral following 

the initial roll input. 

This proposed special condition 

differs from similar special conditions 

applied to previous designs. This 

special condition is limited to the roll 

axis only, whereas previous special 

conditions also included pitch and yaw 

axes. A special condition is no longer 

needed for the yaw axis because 

§ 25.351 was revised at Amendment 25–

91 to take into account effects of an 

electronic flight control system. No 

special condition is needed for the pitch 

axis because the applicant’s proposed 

methodology for the pitch maneuver 

takes into account effects of an 

electronic flight control system. 

Applicability 

As discussed above, these proposed 

special conditions are applicable to the 

787. Should Boeing 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 proposed special conditions 

would apply to that model as well 

under the provisions of § 21.101. 

Conclusion 

This action affects only certain novel 

or unusual design features of the 787. It 

is not a rule of general applicability, and 

it affects only the applicant that 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. 

The authority citation for these 

Special Conditions is as follows: 

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

44702, 44704. 

The Proposed Special Conditions 

Accordingly, the Administrator of the 

Federal Aviation Administration (FAA) 

proposes the following special 

conditions as part of the type 

certification basis for the Boeing Model 

787–8 airplane. 

1. Interaction of Systems and Structures 

The Boeing Model 787–8 airplane is 

equipped with systems which 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 subparts C and D of part 25 of Title 

14 of the Code of Federal Regulations. 

The following criteria must be used for 

showing compliance with this proposed 

special condition 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 this proposed 

special condition is used for other 

systems, it may be necessary to adapt 

the criteria to the specific system. 

(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 structures whose failure 

could prevent continued safe flight and 

landing. Specific criteria defining 

acceptable limits on handling 

characteristics or stability requirements 

when operating in the system degraded 


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or inoperative mode are not provided in 

this special condition. 

(b) Depending on the specific 

characteristics of the airplane, 

additional studies may be required that 

go beyond the criteria provided in this 

special condition in order to 

demonstrate 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 this special condition. 

(1) Structural performance: 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 

(fuel, payload, and master minimum 

equipment list limitations, for example). 

(4) Probabilistic terms: Terms 

(probable, improbable, extremely 

improbable) used in this special 

condition which are the same as those 

probabilistic terms used in § 25.1309. 

(5) Failure condition: Term that is the 

same as that used in § 25.1309. The term 

failure condition in this proposed 

special condition, however, 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 (f) of 

the proposed special condition, there is no 

specific reliability requirement for the 

annunciation system required in paragraph 

(g) of the proposed special condition. 

(d) General. The following criteria 

will be used in determining the 

influence of a system and its failure 

conditions on the airplane structure. 

(e) 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 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. 

(2) 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. 

(3) The airplane must meet the 

aeroelastic stability requirements of 

§ 25.629. 

(f) System in the failure condition. For 

any system failure condition not shown 

to be extremely improbable, the 

following apply: 

(1) Establishing loads at the time of 

failure. Starting from 1-g 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. 

(i) 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. 

(ii) For residual strength 

substantiation, the airplane must be able 

to withstand two thirds of the ultimate 

loads defined in subparagraph (f)(1)(i) of 

these special conditions. For 

pressurized cabins, these loads must be 

combined with the normal operating 

differential pressure. 

(iii) Freedom from aeroelastic 

instability must be shown up to the 

speeds defined in § 25.629(b)(2). For 

failure conditions that result in speeds 

beyond design cruise speed or design 

cruise mach number (VC/MC), freedom 

from aeroelastic instability must be 

shown to increased speeds, so that the 

margins intended by § 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) Establishing loads in the system 

failed state for the continuation of the 

flight. For the continuation of flight of 

the airplane 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 

VC/MC, or the speed limitation 


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prescribed for the remainder of the 

flight, must be determined: 

(A) The limit symmetrical 

maneuvering conditions specified in 

§ 25.331 and § 25.345. 

(B) The limit gust and turbulence 

conditions specified in § 25.341 and 

§ 25.345. 

(C) The limit rolling conditions 

specified in § 25.349 and the limit 

unsymmetrical conditions specified in 

§ 25.367 and § 25.427(b) and (c). 

(D) The limit yaw maneuvering 

conditions specified in § 25.351. 

(E) The limit ground loading 

conditions specified in § 25.473 and 

§ 25.491. 

(ii) For static strength substantiation, 

each part of the structure must be able 

to withstand the loads in paragraph 

(f)(2)(i) of the special condition 

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. 

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-Structure, of 14 CFR part 25. 

(iii) For residual strength 

substantiation, the airplane must be able 

to withstand two-thirds of the ultimate 

loads defined in paragraph (f)(2)(ii) of 

the special condition. 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 § 25.629(b). 

V′ = Clearance speed as defined by 

§ 25.629(b)(2). 

V′′ = Clearance speed as defined by 

§ 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 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 § 25.571(b). 

(3) Consideration of certain failure 

conditions may be required by other 

sections of 14 CFR part 25 regardless of 

calculated system reliability. Where 


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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. 

(g) 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 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 crew during 

flight. 

(h) 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 this special condition 

must be met, including the provisions of 

paragraph (e) for the dispatched 

condition, and paragraph (f) 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. 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. 

2. Electronic Flight Control System: 

Control Surface Awareness 

In addition to compliance with 

§§ 25.143, 25.671, and 25.672, the 

following special condition applies: 

(a) The system design must ensure 

that the flightcrew is made suitably 

aware whenever the primary control 

means nears the limit of control 

authority. This indication should direct 

the pilot to take appropriate action to 

avoid the unsafe condition in 

accordance with appropriate airplane 

flight manual (AFM) instructions. 

Depending on the application, suitable 

annunciations may include cockpit 

control position, annunciator light, or 

surface position indicators. 

Furthermore, this requirement applies at 

limits of control authority, not 

necessarily at limits of any individual 

surface travel. 

(b) Suitability of such a display or 

alerting must take into account that 

some pilot-demanded maneuvers are 

necessarily associated with intended 

full performance, which may require 

full surface deflection. Therefore, 

simple alerting systems, which would 

function in both intended or unexpected 

control-limiting situations, must be 

properly balanced between needed crew 

awareness and nuisance factors. A 

monitoring system which might 

compare airplane motion, surface 

deflection, and pilot demand could be 

useful for eliminating nuisance alerting. 

3. High Intensity Radiated Fields 

(HIRF) Protection 

(a) Protection from Unwanted Effects 

of High-intensity Radiated Fields. Each 

electrical and electronic system which 

performs critical functions must be 

designed and installed to ensure that the 

operation and operational capabilities of 

these systems to perform critical 

functions are not adversely affected 

when the airplane is exposed to high 

intensity radiated fields external to the 

airplane. 

(b) For the purposes of these Special 

Conditions, the following definition 

applies: Critical Functions: Functions 

whose failure would contribute to or 

cause a failure condition that would 

prevent continued safe flight and 

landing of the airplane. 

4. Limit Engine Torque Loads for 

Sudden Engine Stoppage 

In lieu of § 25.361(b) the following 

special condition is proposed: 

(a) For turbine engine installations, 

the engine mounts, pylons, and adjacent 

supporting airframe structure must be 

designed to withstand 1g level flight 

loads acting simultaneously with the 

maximum limit torque loads imposed 

by each of the following: 

(1) Sudden engine deceleration due to 

a malfunction which could result in a 

temporary loss of power or thrust. 

(2) The maximum acceleration of the 

engine. 

(b) For auxiliary power unit 

installations, the power unit mounts 

and adjacent supporting airframe 

structure must be designed to withstand 

1g level flight loads acting 

simultaneously with the maximum limit 

torque loads imposed by each of the 

following: 

(1) Sudden auxiliary power unit 

deceleration due to malfunction or 

structural failure. 

(2) The maximum acceleration of the 

power unit. 

(c) For engine supporting structure, an 

ultimate loading condition must be 

considered that combines 1g flight loads 

with the transient dynamic loads 

resulting from each of the following: 

(1) Loss of any fan, compressor, or 

turbine blade. 

(2) Where applicable to a specific 

engine design, any other engine 

structural failure that results in higher 

loads. 

(d) The ultimate loads developed from 

the conditions specified in paragraphs 

(c)(1) and (c)(2) are to be multiplied by 

a factor of 1.0 when applied to engine 

mounts and pylons and multiplied by a 

factor of 1.25 when applied to adjacent 

supporting airframe structure. 

5. Design Roll Maneuver Requirement 

In lieu of compliance to § 25.349(a), 

the following special conditions are 

proposed. 

The following conditions, speeds, and 

cockpit roll control motions (except as 

the motions may be limited by pilot 

effort) must be considered in 

combination with an airplane load 

factor of zero and of two-thirds of the 

positive maneuvering factor used in 

design. In determining the resulting 

control surface deflections, the torsional 

flexibility of the wing must be 

considered in accordance with 

§ 25.301(b): 

(a) Conditions corresponding to 

steady rolling velocities must be 

investigated. In addition, conditions 

corresponding to maximum angular 


jlentini on PROD1PC65 with PROPOSAL
Federal Register / Vol. 72, No. 47 / Monday, March 12, 2007 / Proposed Rules 10947 

acceleration must be investigated for 

airplanes with engines or other weight 

concentrations outboard of the fuselage. 

For the angular acceleration conditions, 

zero rolling velocity may be assumed in 

the absence of a rational time history 

investigation of the maneuver. 

(b) At VA, sudden movement of the 

cockpit roll control up to the limit is 

assumed. The position of the cockpit 

roll control must be maintained until a 

steady roll rate is achieved and then 

must be returned suddenly to the 

neutral position. 

(c) At VC, the cockpit roll control 

must be moved suddenly and 

maintained so as to achieve a roll rate 

not less than that obtained in paragraph 

(2). 

(d) At VD, the cockpit roll control 

must be moved suddenly and 

maintained so as to achieve a roll rate 

not less than one-third of that obtained 

in paragraph (2). 

Issued in Renton, Washington, on March 1, 

2007. 

Ali Bahrami, 

Manager, Transport Airplane Directorate, 

Aircraft Certification Service. 

[FR Doc. E7–4306 Filed 3–9–07; 8:45 am] 

BILLING CODE 4910–13–P 

DEPARTMENT OF TRANSPORTATION 

Federal Aviation Administration 

14 CFR Part 39 

[Docket No. FAA–2007–27508; Directorate 

Identifier 2006–NM–252–AD] 

RIN 2120–AA64 

Airworthiness Directives; Empresa 

Brasileira de Aeronautica S.A. 

(EMBRAER) ERJ 170 Airplanes 

AGENCY: Federal Aviation 

Administration (FAA), Department of 

Transportation (DOT). 

ACTION: Notice of proposed rulemaking 

(NPRM). 

SUMMARY: We propose to adopt a new 

airworthiness directive (AD) for the 

products listed above. This proposed 

AD results from mandatory continuing 

airworthiness information (MCAI) 

issued by an aviation authority of 

another country to identify and correct 

an unsafe condition on an aviation 

product. The MCAI describes the unsafe 

condition as an obstruction at the cargo 

compartment fire extinguisher system 

drier metering unit (DME) inlet, 

affecting the system effectiveness and, 

consequently, making the fire 

extinguishing capability at those 

compartments inadequate should a fire 

erupt. The proposed AD would require 

actions that are intended to address the 

unsafe condition described in the MCAI. 

DATES: We must receive comments on 

this proposed AD by April 11, 2007. 

ADDRESSES: You may send comments by 

any of the following methods: 

• DOT Docket Web Site: Go to 

http://dms.dot.gov and follow the 

instructions for sending your comments 

electronically. 

• Fax: (202) 493–2251. 

• Mail: Docket Management Facility, 

U.S. Department of Transportation, 400 

Seventh Street, SW., Nassif Building, 

Room PL–401, Washington, DC 20590–

0001. 

• Hand Delivery: Room PL–401 on 

the plaza level of the Nassif Building, 

400 Seventh Street, SW., Washington, 

DC, between 9 a.m. and 5 p.m., Monday 

through Friday, except Federal holidays. 

• Federal eRulemaking Portal: http:// 

www.regulations.gov. Follow the 

instructions for submitting comments. 

Examining the AD Docket 

You may examine the AD docket on 

the Internet at http://dms.dot.gov; or in 

person at the Docket Management 

Facility between 9 a.m. and 5 p.m., 

Monday through Friday, except Federal 

holidays. The AD docket contains this 

proposed AD, the regulatory evaluation, 

any comments received, and other 

information. The street address for the 

Docket Office (telephone (800) 647–

5227) is in the ADDRESSES section. 

Comments will be available in the AD 

docket shortly after receipt. 

FOR FURTHER INFORMATION CONTACT: 

Todd Thompson, Aerospace Engineer, 

International Branch, ANM–116, FAA, 

Transport Airplane Directorate, 1601 

Lind Avenue, SW., Renton, Washington 

98057–3356; telephone (425) 227–1175; 

fax (425) 227–1149. 

SUPPLEMENTARY INFORMATION: 

Streamlined Issuance of AD 

The FAA is implementing a new 

process for streamlining the issuance of 

ADs related to MCAI. This streamlined 

process will allow us to adopt MCAI 

safety requirements in a more efficient 

manner and will reduce safety risks to 

the public. This process continues to 

follow all FAA AD issuance processes to 

meet legal, economic, Administrative 

Procedure Act, and Federal Register 

requirements. We also continue to meet 

our technical decision-making 

responsibilities to identify and correct 

unsafe conditions on U.S.-certificated 

products. 

This proposed AD references the 

MCAI and related service information 

that we considered in forming the 

engineering basis to correct the unsafe 

condition. The proposed AD contains 

text copied from the MCAI and for this 

reason might not follow our plain 

language principles. 

Comments Invited 

We invite you to send any written 

relevant data, views, or arguments about 

this proposed AD. Send your comments 

to an address listed under the 

ADDRESSES section. Include ‘‘Docket No. 

FAA–2007–27508; Directorate Identifier 

2006–NM–252–AD’’ at the beginning of 

your comments. We specifically invite 

comments on the overall regulatory, 

economic, environmental, and energy 

aspects of this proposed AD. We will 

consider all comments received by the 

closing date and may amend this 

proposed AD because of those 

comments. 

We will post all comments we 

receive, without change, to http:// 

dms.dot.gov, including any personal 

information you provide. We will also 

post a report summarizing each 

substantive verbal contact we receive 

about this proposed AD. 

Discussion 

The Age`ncia Nacional de Aviac ̧a ̃o 

Civil (ANAC), which is the aviation 

authority for Brazil, has issued Brazilian 

Airworthiness Directive 2006–01–03, 

effective February 7, 2006 (referred to 

after this as ‘‘the MCAI’’), to correct an 

unsafe condition for the specified 

products. The MCAI states that it has 

been found the occurrence of one case 

of obstruction at the cargo compartment 

fire extinguisher system drier metering 

unit (DMU) inlet, affecting the system 

effectiveness and, consequently, making 

the fire extinguishing capability at those 

compartments inadequate should a fire 

erupt. The MCAI requires installation of 

a debris strainer at the DMU inlet. You 

may obtain further information by 

examining the MCAI in the AD docket. 

Relevant Service Information 

EMBRAER has issued Service Bulletin 

170–26–0002, dated November 11, 2005. 

The actions described in this service 

information are intended to correct the 

unsafe condition identified in the 

MCAI. 

FAA’s Determination and Requirements 

of This Proposed AD 

This product has been approved by 

the aviation authority of another 

country, and is approved for operation 

in the United States. Pursuant to our 

bilateral agreement with this State of 

Design Authority, they have notified us 

of the unsafe condition described in the 

MCAI and service information 


jlentini on PROD1PC65 with PROPOSAL