Federal Register / Vol. 76, No. 51 / Wednesday, March 16, 2011 / Proposed Rules 14341 

Dated: March 9, 2011. 

Karen G. Mills, 

Administrator. 

[FR Doc. 2011–5876 Filed 3–15–11; 8:45 am] 

BILLING CODE 8025–01–P 

DEPARTMENT OF TRANSPORTATION 

Federal Aviation Administration 

14 CFR Part 25 

[Docket No. NM400 Special Conditions No. 

25–11–09–SC] 

Special Conditions: Boeing Model 747– 

8/–8F Airplanes, Interaction of Systems 

and Structures 

AGENCY: Federal Aviation 

Administration (FAA), DOT. 

ACTION: Notice of proposed special 

conditions. 

SUMMARY: This notice proposes to 

amend Special Conditions No. 25–388– 

SC for the Boeing Model 747–8/–8F 

airplanes. These special conditions were 

previously issued July 29, 2009, and 

became effective September 10, 2009. 

These special conditions are being 

amended to include additional criteria 

addressing the Outboard Aileron Modal 

Suppression System. The 747–8/–8F 

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 their effects on the 

structural performance. These proposed 

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 the 747–8/–8F airplanes. 

DATES: Comments must be received on 

or before April 15, 2011. 

ADDRESSES: Comments on this proposal 

may be mailed in duplicate to: Federal 

Aviation Administration, Transport 

Airplane Directorate, Attention: Rules 

Docket (ANM–113), Docket No. NM400, 

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. 

NM400. 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: Carl 

Niedermeyer, FAA, Airframe & Cabin 

Safety Branch, ANM–115, Transport 

Airplane Directorate, Aircraft 

Certification Service, 1601 Lind Avenue 

SW., Renton, Washington 98057–3356; 

telephone (425) 227–2279; e-mail 

Carl.Niedermeyer@faa.gov. 

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 

proposed 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 November 4, 2005, The Boeing 

Company, PO Box 3707, Seattle, WA 

98124, applied for an amendment to 

Type Certificate Number A20WE to 

include the new Model 747–8 passenger 

airplane and the new Model 747–8F 

freighter airplane. The Model 747–8 and 

the Model 747–8F are derivatives of the 

747–400 and the 747–400F, 

respectively. Both the Model 747–8 and 

the Model 747–8F are four-engine jet 

transport airplanes that will have a 

maximum takeoff weight of 970,000 

pounds and new General Electric GEnx 

–2B67 engines. The Model 747–8 will 

have two flight crew and the capacity to 

carry 605 passengers. The Model 747– 

8F will have two flight crew and a zero 

passenger capacity, although Boeing has 

submitted a petition for exemption to 

allow the carriage of supernumeraries. 

These special conditions were 

originally issued July 29, 2009, and 

published in the Federal Register on 

August 12, 2009 (74 FR 40479). 

Type Certification Basis 

Under the provisions of Title 14, Code 

of Federal Regulations (14 CFR) 21.101, 

Boeing must show that Model 747–8 

and 747–8F airplanes (hereafter referred 

as 747–8/–8F) meet the applicable 

provisions of part 25, as amended by 

Amendments 25–1 through 25–117, 

except for earlier amendments as agreed 

upon by the FAA. These regulations 

will be incorporated into Type 

Certificate No. A20WE after type 

certification approval of the 747–8/–8F. 

In addition, the certification basis 

includes other regulations, special 

conditions and exemptions that are not 

relevant to these proposed special 

conditions. Type Certificate No. A20WE 

will be updated to include a complete 

description of the certification basis for 

these model airplanes. 

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 747–8/–8F 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, or should any 

other model already included on the 

same type certificate be modified to 

incorporate the same or similar novel or 

unusual design feature, the special 

conditions would also apply to the other 

model under § 21.101. 

In addition to the applicable 

airworthiness regulations and special 

conditions, the 747–8/–8F 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 

§ 11.19, are issued under § 11.38, and 

become part of the type certification 

basis under § 21.101. 

Novel or Unusual Design Features 

The Boeing Model 747–8/–8F 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 


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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. 

The Boeing 747–8F airplane exhibits 

an aeroelastic mode of oscillation that is 

self-excited and does not completely 

damp out after an external disturbance. 

The sustained oscillation (also known as 

a limit cycle oscillation or limit cycle 

flutter) is caused by an unstable 

aeroelastic mode that is prevented from 

becoming a divergent oscillation due to 

one or more nonlinearities that exist in 

the airplane. 

While the sustained oscillation is not 

divergent, the FAA considers it to be an 

aeroelastic instability. Boeing has 

proposed the addition of an Outboard 

Aileron Modal Suppression (OAMS) 

system to the fly-by-wire (FBW) flight 

control system to reduce, but not 

eliminate, the amplitude of the 

sustained oscillation and control the 

aeroelastic instability. 

Section 25.629 requires the airplane 

to be free of any aeroelastic instability, 

including flutter. It also requires the 

airplane to remain flutter free after 

certain failures. The regulations do not 

anticipate the use of systems that 

control flutter modes but do not 

completely suppress them. The use of 

the OAMS system is a novel and 

unusual design feature that the 

airworthiness standards do not 

adequately address. The FAA believes 

such systems can be used to ensure that 

limit cycle (non-divergent) flutter is 

kept to safe levels. Therefore, the FAA 

proposes a special condition that 

addresses this particular sustained 

oscillation characteristic and provides 

the necessary standards that permit the 

use of such active flutter control 

systems. 

Applicability 

As discussed above, this proposed 

special condition is applicable to Boeing 

Model 747–8/–8F airplanes. 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, this proposed 

special condition 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 Boeing 

Model 747–8/–8F 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 this 

proposed Special Condition is as 

follows: 

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

44702, 44704. 

The Proposed Special Conditions 

Accordingly, pursuant to the 

authority delegated to me by the 

Administrator, the Federal Aviation 

Administration (FAA) proposes the 

following amendment to Special 

Conditions 25–388–SC as part of the 

type certification basis for the 747–8/– 

8F airplanes. The standards in Section 

A have been modified to incorporate the 

reference to Section C and remove 

‘‘flutter control systems’’ from the 

applicability of this special condition. 

Section B was already adopted in 

Special Conditions 25–388–SC and is 

included for reference. Comments are 

invited on the amended Section A and 

the proposed text of Section C, 

Outboard Aileron Modal Suppression 

System. 

A. General 

The Boeing Model 747–8/–8F 

airplanes are equipped with automatic 

control systems that affect the airplane’s 

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. Except as provided in Section 

C of this special condition, the 

following criteria must be used for 

showing compliance with this special 

condition for airplanes equipped with 

flight control systems, autopilots, 

stability augmentation systems, load 

alleviation systems, fuel management 

systems, and other systems that either 

directly or as a result of failure or 

malfunction affect structural 

performance. If this special condition is 

used for other systems, it may be 

necessary to adapt the criteria to the 

specific system. 

1. The criteria defined here only 

address the direct structural 

consequences of the system responses 

and performances and cannot be 

considered in isolation; however, they 

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 structural elements 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 mode are not provided in 

this special condition. 

2. 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 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. 

3. The following definitions are 

applicable to this special condition. 

(a) Structural performance: Capability 

of the airplane to meet the structural 

requirements of part 25. 

(b) Flight limitations: Limitations that 

can be applied to the airplane flight 

conditions following an in-flight 

occurrence and that are included in the 

airplane flight manual (AFM) (e.g., 

speed limitations, avoidance of severe 

weather conditions). 

(c) 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 (MMEL) 

limitations). 

(d) Probabilistic terms: The 

probabilistic terms (probable, 

improbable, extremely improbable) used 

in this special condition are the same as 

those used in § 25.1309. 

(e) Failure condition: The term failure 

condition is the same as that used in 

§ 25.1309, however this special 

condition applies only to system failure 

conditions that affect the structural 

performance of the airplane (e.g., system 

failure conditions that induce loads, 

change the response of the airplane to 

inputs such as gusts or pilot actions, or 

lower flutter margins). The system 

failure condition includes consequential 

or cascading effects resulting from the 

first failure. 

B. Effects of Systems on Structures 

1. General. The following criteria will 

be used in determining the influence of 

a system and its failure conditions on 

the airplane structural elements. 

2. System fully operative. With the 

system fully operative, the following 

apply: 

(a) Limit loads must be derived in all 

normal operating configurations of the 

system from all the limit conditions 

specified in subpart C (or used in lieu 

of those specified in subpart C), taking 

into account any special behavior of 


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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. 

(b) The airplane must meet the 

strength requirements of part 25 (i.e., 

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. 

(c) The airplane must meet the 

aeroelastic stability requirements of 

§ 25.629. 

3. System in the failure condition. For 

any system failure condition not shown 

to be extremely improbable, the 

following apply: 

(a) 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. 

(1) 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 (F.S.) is 

defined in Figure 1. 

BILLING CODE 4910–13–P 

(2) For residual strength 

substantiation, the airplane must be able 

to withstand two thirds of the ultimate 

loads defined in subparagraph 3(a)(1). 

For pressurized cabins, these loads must 

be combined with the normal operating 

differential pressure. 

(3) 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 VC/MC, freedom from 

aeroelastic instability must be shown to 

increased speeds, so that the margins 

intended by § 25.629(b)(2) are 

maintained. 

(4) Failures of the system that result 

in forced structural vibrations 

(oscillatory failures) must not produce 

loads that could result in detrimental 

deformation of the affected structural 

elements. 

(b) For continuation of flight, for an 

airplane in the system failed state and 

considering any appropriate 

reconfiguration and flight limitations, 

the following apply: 

(1) The loads derived from the 

following conditions (or used in lieu of 

the following conditions) at speeds up 

to VC/MC, or the speed limitation 

prescribed for the remainder of the 

flight, must be determined: 

(i) the limit symmetrical maneuvering 

conditions specified in § 25.331 and in 

§ 25.345. 

(ii) the limit gust and turbulence 

conditions specified in § 25.341 and in 

§ 25.345. 

(iii) the limit rolling conditions 

specified in § 25.349 and the limit 

unsymmetrical conditions specified in 

§§ 25.367 and 25.427(b) and (c). 

(iv) the limit yaw maneuvering 

conditions specified in § 25.351. 

(v) the limit ground loading 

conditions specified in §§ 25.473, 

25.491 and 25.493. 

(2) For static strength substantiation, 

each part of the structure must be able 

to withstand the loads in paragraph 

(3)(b)(1) of the special condition 

multiplied by a factor of safety 

depending on the probability of being in 


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14344 Federal Register / Vol. 76, No. 51 / Wednesday, March 16, 2011 / Proposed Rules 

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. 

(3) For residual strength 

substantiation, the airplane must be able 

to withstand two thirds of the ultimate 

loads defined in paragraph (3)(b)(1) of 

the special condition. For pressurized 

cabins, these loads must be combined 

with the normal operating differential 

pressure. 

(4) 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. 

(5) 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). 


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BILLING CODE 4910–13–C 

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′′. 

(6) 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). 

(c) 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. 

4. Failure indications. For system 

failure detection and indication, the 

following apply: 

(a) 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. As 

far as reasonably practicable, the flight 

crew 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 

(CMRs) 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. 

(b) 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 flight crew. 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. 

5. 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 2 for the dispatched 

condition, and paragraph 3 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. 

C. Outboard Aileron Modal Suppression 

System 

1. In general, this special condition 

applies to fly-by-wire active flutter 

suppression systems that are intended 

to operate on a certain type of 

aeroelastic instability. This type of 

instability is characterized by a low 

frequency, self-excited, sustained 


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oscillation of an aeroelastic vibration 

mode that is shown to be a stable limit 

cycle oscillation (LCO), with the system 

operative and inoperative. (An LCO is 

considered ‘‘stable’’ if it maintains the 

same frequency and amplitude for a 

given excitation input and flight 

condition.) In addition, the type of 

sustained oscillation covered by this 

special condition must not be a hazard 

to the airplane nor its occupants with 

the active system failed. These systems 

must be shown to reduce the amplitude 

of the sustained oscillation to acceptable 

levels and effectively control the 

aeroelastic instability. 

Specifically, the following criteria 

address the existence of such a 

sustained oscillation on the Boeing 

Model 747–8/–8F airplanes and the 

Outboard Aileron Modal Suppression 

(OAMS) system that will be used to 

control it. 

2. In lieu of the requirements 

contained in § 25.629, the existence of a 

sustained, or limit cycle, oscillation that 

is controlled by an active flight control 

system is acceptable, provided that the 

following requirements are met: 

(a) OAMS System Inoperative 

(1) The sustained, or limit cycle, 

oscillation must be shown by test and 

analysis to be stable throughout the 

nominal aeroelastic stability envelope 

specified in § 25.629(b)(1) with the 

OAMS system inoperative. This should 

include the consideration of 

disturbances above the sustained 

amplitude of oscillation 

(b) Nominal Conditions: 

(1) With the OAMS system operative 

it must be shown that the airplane 

remains safe, stable, and controllable 

throughout the nominal aeroelastic 

stability envelope specified in 

§ 25.629(b)(1) by providing adequate 

suppression of the aeroelastic modes 

being controlled. All applicable 

airworthiness and environmental 

requirements should continue to be 

complied with. Additionally, loads 

imposed on the airplane due to any 

amplitude of oscillation must be shown 

to have a negligible impact on structure 

and systems, including wear, fatigue 

and damage tolerance. The OAMS 

system must function properly in all 

environments that may be encountered. 

(2) The applicant must establish by 

test and analysis that the OAMS system 

can be relied upon to control and limit 

the sustained amplitude of the 

oscillation to acceptable levels (per 

§ 25.251) and control the stability of the 

aeroelastic mode. This should include 

the consideration of disturbances above 

the sustained amplitude of oscillation; 

maneuvering flight, icing conditions; 

manufacturing variations; Master 

Minimum Equipment List (MMEL) 

items; spare engine carriage; engine 

removed or inoperative ferry flights; and 

wear, repairs, and modifications 

throughout the service life of the 

airplane by: 

(i) Analysis to the nominal aeroelastic 

stability envelope specified in 

§ 25.629(b)(1), and 

(ii) Flight flutter test to the VDF/MDF

boundary. These tests must demonstrate 

that the airplane has a proper margin of 

damping for disturbances above the 

sustained amplitude of oscillation at all 

speeds up to VDF/MDF, and that there is 

no large and rapid reduction in damping 

as VDF/MDF is approached. 

(iii) The structural modes must have 

adequate stability margins for any 

OAMS flight control system feedback 

loop at speeds up to the fail-safe 

aeroelastic stability envelope specified 

in § 25.629(b)(2). 

(c) Failures, Malfunctions, and 

Adverse Conditions: 

(1) For the OAMS system operative 

and failed, for any failure, or 

combination of failures not shown to be 

extremely improbable, and addressed by 

§§ 25.629(d), 25.571, 25.631, 25.671, 

25.672, 25.901(c) or 25.1309 that results 

in LCO, it must be established by test or 

analysis up to the aeroelastic stability 

envelope specified in § 25.629(b)(2) that 

the LCO: 

(i) is stable and decays to an 

acceptable limited amplitude once an 

external perturbing force is removed; 

(ii) does not result in loads that would 

cause static, dynamic, or fatigue failure 

of structure during the expected 

exposure period; 

(iii) does not result in repeated loads 

that would cause an additional failure 

due to wear during the expected 

exposure period that precludes safe 

flight and landing; 

(iv) has, if necessary, sufficient 

indication of OAMS failure(s) and crew 

procedures to properly address the 

failure(s); 

(v) does not result in a vibration 

condition on the flight deck that is 

severe enough to interfere with control 

of the airplane, ability of the crew to 

read the flight instruments, perform 

vital functions like reading and 

accomplishing checklist procedures, or 

to cause excessive fatigue to the crew; 

(vi) does not result in adverse effects 

on the flight control system or on 

airplane stability, controllability, or 

handling characteristics (including 

airplane-pilot coupling (APC) per 

§ 25.143) that would prevent safe flight 

and landing; and 

(vii) does not interfere with the flight 

crew’s ability to correctly distinguish 

vibration from buffeting associated with 

the recognition of stalls or high speed 

buffet. 

(2) The applicant must show that 

particular risks such as engine failure, 

uncontained engine, or APU rotor burst, 

or other failures not shown to be 

extremely improbable, will not 

adversely or significantly change the 

aeroelastic stability characteristics of the 

airplane. 

(3) No MMEL dispatch is allowed 

with the OAMS system inoperative. 

Issued in Renton, Washington on March 9, 

2011. 

Ali Bahrami, 

Manager, Transport Airplane Directorate, 

Aircraft Certification Service. 

[FR Doc. 2011–6073 Filed 3–15–11; 8:45 am] 

BILLING CODE 4910–13–P 

DEPARTMENT OF TRANSPORTATION 

Federal Aviation Administration 

14 CFR Part 39 

[Docket No. FAA–2011–0231; Directorate 

Identifier 2011–CE–003–AD] 

RIN 2120–AA64 

Airworthiness Directives; Diamond 

Aircraft Industries GmbH Model DA 42 

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) 

originated 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: 

Cracks have been reportedly found on DA 

42 Main Landing Gear (MLG) Damper-toTrailing Arm joints during standard 

maintenance. Depending on environmental-, 

operating- and runway conditions, the 

affected MLG joint, Part Number (P/N) D60– 

3217–23–5x (4 different lengths are 

available), which is made of aluminum, is 

susceptible to cracking. 

This condition, if not detected and 

corrected, may lead to failure of the joint and 

subsequent damage or malfunction of the 

MLG, possibly resulting in damage to the 

aeroplane during landing and injury to 

occupants. 

The proposed AD would require 

actions that are intended to address the 

unsafe condition described in the MCAI. 


jlentini on DSKJ8SOYB1PROD with PROPOSALS