Federal Register / Vol. 72, No. 80 / Thursday April 26, 2007 / Proposed Rules 20777 

3. Will not have a significant 

economic impact, positive or negative, 

on a substantial number of small entities 

under the criteria of the Regulatory 

Flexibility Act. 

We prepared a regulatory evaluation 

of the estimated costs to comply with 

this proposed AD and placed it in the 

AD docket. See the ADDRESSES section 

for a location to examine the regulatory 

evaluation. 

List of Subjects in 14 CFR Part 39 

Air transportation, Aircraft, Aviation 

safety, Safety. 

The Proposed Amendment 

Accordingly, under the authority 

delegated to me by the Administrator, 

the FAA proposes to amend 14 CFR part 

39 as follows: 

PART 39—AIRWORTHINESS 

DIRECTIVES 

1. The authority citation for part 39 

continues to read as follows: 

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

§ 39.13 [Amended] 

2. The Federal Aviation 

Administration (FAA) amends § 39.13 

by adding the following new 

airworthiness directive (AD): 

LEARJET: Docket No. FAA–2007–28016; 

Directorate Identifier 2006–NM–227–AD. 

Comments Due Date 

(a) The FAA must receive comments on 

this AD action by June 11, 2007. 

Affected ADs 

(b) None. 

Applicability 

(c) This AD applies to Learjet Model 31, 

31A, 35, 35A (C–21A), 36, 36A, 55, 55B, and 

55C airplanes, and Model 45 airplanes; 

certificated in any category; as identified in 

the service information specified in Table 1 

of this AD. 

TABLE 1.—APPLICABLE SERVICE INFORMATION

Learjet airplane model Service bulletin Revision level Date 

31/31A ......................................... Bombardier Service Bulletin 31–54–2 ............................................. 1 ....................... August 21, 2006. 

45 ................................................ Bombardier Service Bulletin 45–54–3 ............................................. 2 ....................... August 15, 2003. 

35/35A (C–21A) and 36/36A ...... Learjet Service Bulletin 35/36–54–3 ............................................... Original ............. March 16, 2001. 

55/55B/55C ................................. Learjet Service Bulletin 55–54–3 .................................................... Original ............. March 16, 2001. 

Unsafe Condition 

(d) This AD results from a report that 

unsealed gaps (penetration points) of the 

engine firewall were discovered during 

production. We are issuing this AD to 

prevent penetration of flammable liquids or 

fire through the engine firewall into the 

engine pylon, which could lead to fire inside 

the airplane. 

Compliance 

(e) You are responsible for having the 

actions required by this AD performed within 

the compliance times specified, unless the 

actions have already been done. 

Inspecting, Cleaning, and Sealing of Gaps in 

Engine Firewall 

(f) Within 12 months after the effective 

date of this AD, do the actions described in 

paragraphs (f)(1) and (f)(2) of this AD, in 

accordance with the applicable service 

information specified in Table 1 of this AD. 

(1) For all airplanes: Inspect for unsealed 

gaps on the pylon side of the engine firewall 

and clean and seal any unsealed gap. 

(2) For Learjet Model 45 airplanes only: 

Inspect the engine pylon trailing edge for 

unsealed gaps, and clean and seal any 

unsealed gap. 

Credit for Actions Done Using Previous 

Service Information 

(g) Actions accomplished before the 

effective date of this AD according to 

Bombardier Service Bulletin 31–54–2, dated 

March 16, 2001; or Bombardier Service 

Bulletin 45–54–3, dated March 16, 2001; or 

Revision 1, dated December 12, 2001; as 

applicable; are considered acceptable for 

compliance with the corresponding action 

specified in this AD. 

Alternative Methods of Compliance 

(AMOCs) 

(h)(1) The Manager, Wichita Aircraft 

Certification Office (ACO), FAA, has the 

authority to approve AMOCs for this AD, if 

requested in accordance with the procedures 

found in 14 CFR 39.19. 

(2) To request a different method of 

compliance or a different compliance time 

for this AD, follow the procedures in 14 CFR 

39.19. Before using any approved AMOC on 

any airplane to which the AMOC applies, 

notify your appropriate principal inspector 

(PI) in the FAA Flight Standards District 

Office (FSDO), or lacking a PI, your local 

FSDO. 

Issued in Renton, Washington, on April 19, 

2007. 

Ali Bahrami, 

Manager, Transport Airplane Directorate, 

Aircraft Certification Service. 

[FR Doc. E7–8001 Filed 4–25–07; 8:45 am] 

BILLING CODE 4910–13–P 

DEPARTMENT OF TRANSPORTATION 

Federal Aviation Administration 

14 CFR Part 39 

[Docket No. FAA–2006–26353; Directorate 

Identifier 2006–NM–189–AD] 

RIN 2120–AA64 

Airworthiness Directives; Bombardier 

Model CL–600–1A11 (CL–600), CL–

600–2A12 (CL–601), CL–600–2B16 (CL–

601–3A, CL–601–3R, and CL–604) 

Airplanes 

AGENCY: Federal Aviation 

Administration (FAA), Department of 

Transportation (DOT). 

ACTION: Supplemental notice of 

proposed rulemaking (NPRM); 

reopening of comment period. 

SUMMARY: The FAA is revising an earlier 

NPRM for an airworthiness directive 

(AD) that applies to certain Bombardier 

Model CL–600–1A11 (CL–600) 

airplanes, CL–600–2A12 (CL–601) 

airplanes, and CL–600–2B16 (CL–601–

3A, CL–601–3R, and CL–604) airplanes. 

The original NPRM would have 

required inspecting to identify the part 

number and serial number of the 

selector valves of the nose landing gear 

(NLG) and the nose gear door; and doing 

related investigative and corrective 

actions if necessary. The original NPRM 

resulted from reports of uncommanded 

partial retractions of the NLG. This 

action revises the original NPRM by 

adding airplanes to the applicability. 


jlentini on PROD1PC65 with PROPOSALS
20778 Federal Register / Vol. 72, No. 80 / Thursday April 26, 2007 / Proposed Rules 

We are proposing this supplemental 

NPRM to prevent internal leakage of the 

selector valve, which, under certain 

conditions, could result in an 

uncommanded retraction of the NLG 

with consequent damage to the airplane 

and possible serious injury to ground 

personnel. 

DATES: We must receive comments on 

this supplemental NPRM by May 21, 

2007. 

ADDRESSES: Use one of the following 

addresses to submit comments on this 

supplemental NPRM. 

• DOT Docket Web site: Go to http:// 

dms.dot.gov and follow the instructions 

for sending your comments 

electronically. 

• Government-wide rulemaking Web 

site: Go to http://www.regulations.gov 

and follow the instructions for sending 

your comments electronically. 

• Mail: Docket Management Facility; 

U.S. Department of Transportation, 400 

Seventh Street, SW., Nassif Building, 

Room PL–401, Washington, DC 20590. 

• Fax: (202) 493–2251. 

• 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. 

Contact Bombardier, Inc., Canadair, 

Aerospace Group, P.O. Box 6087, 

Station Centre-ville, Montreal, Quebec 

H3C 3G9, Canada, for service 

information identified in this proposed 

AD. 

FOR FURTHER INFORMATION CONTACT: 

Daniel Parrillo, Aerospace Engineer, 

Systems and Flight Test Branch, ANE–

172, FAA, New York Aircraft 

Certification Office, 1600 Stewart 

Avenue, suite 410, Westbury, New York 

11590; telephone (516) 228–7305; fax 

(516) 794–5531. 

SUPPLEMENTARY INFORMATION: 

Comments Invited 

We invite you to submit any relevant 

written data, views, or arguments 

regarding this supplemental NPRM. 

Send your comments to an address 

listed in the ADDRESSES section. Include 

the docket number ‘‘Docket No. FAA–

2006–26353; Directorate Identifier 

2006–NM–189–AD’’ at the beginning of 

your comments. We specifically invite 

comments on the overall regulatory, 

economic, environmental, and energy 

aspects of this supplemental NPRM. We 

will consider all comments received by 

the closing date and may amend this 

supplemental NPRM in light of those 

comments. 

We will post all comments submitted, 

without change, to http://dms.dot.gov, 

including any personal information you 

provide. We will also post a report 

summarizing each substantive verbal 

contact with FAA personnel concerning 

this supplemental NPRM. Using the 

search function of that Web site, anyone 

can find and read the comments in any 

of our dockets, including the name of 

the individual who sent the comment 

(or signed the comment on behalf of an 

association, business, labor union, etc.). 

You may review the DOT’s complete 

Privacy Act Statement in the Federal 

Register published on April 11, 2000 

(65 FR 19477–78), or you may visit 

http://dms.dot.gov. 

Examining the Docket 

You may examine the AD docket on 

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

person at the Docket Management 

Facility office between 9 a.m. and 5 

p.m., Monday through Friday, except 

Federal holidays. The Docket 

Management Facility office (telephone 

(800) 647–5227) is located on the plaza 

level in the Nassif Building at the DOT 

street address stated in ADDRESSES. 

Comments will be available in the AD 

docket shortly after the Docket 

Management System receives them. 

Discussion 

We proposed to amend 14 CFR part 

39 with a notice of proposed rulemaking 

(NPRM) for an airworthiness directive 

(AD) (the ‘‘original NPRM’’). The 

original NPRM applies to certain 

Bombardier Model CL–600–1A11 (CL–

600) airplanes, CL–600–2A12 (CL–601) 

airplanes, and CL–600–2B16 (CL–601–

3A, CL–601–3R, and CL–604) airplanes. 

The original NPRM was published in 

the Federal Register on November 20, 

2006 (71 FR 67079). The original NPRM 

proposed to require inspecting to 

identify the part number and serial 

number of the selector valves of the 

nose landing gear (NLG) and the nose 

gear door, and doing related 

investigative and corrective actions if 

necessary. 

Actions Since Original NPRM Was 

Issued 

Since the original NPRM was issued, 

Bombardier has determined that 

additional airplanes are subject to the 

unsafe condition. 

Relevant Service Information 

Bombardier has issued Service 

Bulletin 604–32–021, Revision 02, dated 

February 20, 2007 (for Model CL–600–

2B16 (CL–604) airplanes). The service 

bulletin adds airplanes to the effectivity; 

however, Revision 02 is technically 

identical to Revision 01, dated February 

20, 2006. We referred to Revision 01 as 

the appropriate source of service 

information for doing the actions 

specified in the original NPRM. 

Accomplishing the actions specified in 

the service information is intended to 

adequately address the unsafe 

condition. 

FAA’s Determination and Proposed 

Requirements of the Supplemental 

NPRM 

Certain changes discussed above 

expand the scope of the original NPRM; 

therefore, we have determined that it is 

necessary to reopen the comment period 

to provide additional opportunity for 

public comment on this supplemental 

NPRM. 

Difference Between Supplemental 

NPRM and Canadian Airworthiness 

Directive 

Although Canadian airworthiness 

directive CF–2006–16, dated July 6, 

2006, applies to certain airplanes as 

identified in Service Bulletin 604–32–

021, Revision 01, this supplemental 

NPRM would apply to those airplanes 

and certain additional airplanes, as 

identified in Service Bulletin 604–32–

021, Revision 02. This difference has 

been coordinated with TCCA. 

Costs of Compliance 

This proposed AD would affect about 

502 airplanes of U.S. registry. 

The inspection to determine the 

manufacturer P/N and S/N of the 

selector valve(s) would take about 1 

work hour per airplane, at an average 

labor rate of $80 per work hour. Based 

on these figures, the estimated cost of 

the proposed AD for U.S. operators is 

$40,160, or $80 per airplane. 

The general visual inspection of the 

selector valve(s), if accomplished, 

would take about 1 work hour per 

airplane, at an average labor rate of $80 

per work hour. Based on these figures, 

the estimated cost of the proposed AD 

for U.S. operators is $80 per airplane. 

Authority for This Rulemaking 

Title 49 of the United States Code 

specifies the FAA’s authority to issue 

rules on aviation safety. Subtitle I, 

Section 106, describes the authority of 

the FAA Administrator. Subtitle VII, 

Aviation Programs, describes in more 

detail the scope of the Agency’s 

authority. 

We are issuing this rulemaking under 

the authority described in Subtitle VII, 

Part A, Subpart III, Section 44701, 

‘‘General requirements.’’ Under that 

section, Congress charges the FAA with 

promoting safe flight of civil aircraft in 

air commerce by prescribing regulations 

for practices, methods, and procedures 

the Administrator finds necessary for 


jlentini on PROD1PC65 with PROPOSALS
Federal Register / Vol. 72, No. 80 / Thursday April 26, 2007 / Proposed Rules 20779 

safety in air commerce. This regulation 

is within the scope of that authority 

because it addresses an unsafe condition 

that is likely to exist or develop on 

products identified in this rulemaking 

action. 

Regulatory Findings 

We have determined that this 

proposed AD would not have federalism 

implications under Executive Order 

13132. This proposed AD would not 

have a substantial direct effect on the 

States, on the relationship between the 

national Government and the States, or 

on the distribution of power and 

responsibilities among the various 

levels of government. 

For the reasons discussed above, I 

certify that the proposed regulation: 

1. Is not a ‘‘significant regulatory 

action’’ under Executive Order 12866; 

2. Is not a ‘‘significant rule’’ under the 

DOT Regulatory Policies and Procedures 

(44 FR 11034, February 26, 1979); and 

3. Will not have a significant 

economic impact, positive or negative, 

on a substantial number of small entities 

under the criteria of the Regulatory 

Flexibility Act. 

We prepared a regulatory evaluation 

of the estimated costs to comply with 

this supplemental NPRM and placed it 

in the AD docket. See the ADDRESSES

section for a location to examine the 

regulatory evaluation. 

List of Subjects in 14 CFR Part 39 

Air transportation, Aircraft, Aviation 

safety, Safety. 

The Proposed Amendment 

Accordingly, under the authority 

delegated to me by the Administrator, 

the FAA proposes to amend 14 CFR part 

39 as follows: 

PART 39—AIRWORTHINESS 

DIRECTIVES 

1. The authority citation for part 39 

continues to read as follows: 

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

§ 39.13 [Amended] 

2. The Federal Aviation 

Administration (FAA) amends § 39.13 

by adding the following new 

airworthiness directive (AD): 

BOMBARDIER, INC. (Formerly Canadair): 

Docket No. FAA–2006–26353; 

Directorate Identifier 2006–NM–189–AD. 

Comments Due Date 

(a) The FAA must receive comments on 

this AD action by May 21, 2007. 

Affected ADs 

(b) None. 

Applicability 

(c) This AD applies to Bombardier Model 

CL–600–1A11 (CL–600) airplanes, CL–600–

2A12 (CL–601) airplanes, and CL–600–2B16 

(CL–601–3A, CL–601–3R, and CL–604) 

airplanes; certificated in any category; having 

serial numbers (S/Ns) as identified in the 

service bulletins specified in Table 1 of this 

AD, as applicable. 

TABLE 1.—BOMBARDIER SERVICE BULLETINS

Service Bulletin Revision 

level Date 

600–0721 (for Model CL–600–1A11 (CL–600) airplanes) ............................................................................ 01 February 20, 2006. 

601–0558 (for Model CL–600–2A12 (CL–601) airplanes, and CL–600–2B16 (CL–601–3A and CL–601–

3R) airplanes).

01 February 20, 2006. 

604–32–021 (for Model CL–600–2B16 (CL–604) airplanes) ........................................................................ 02 February 20, 2007. 

Unsafe Condition 

(d) This AD results from reports of 

uncommanded partial retractions of the nose 

landing gear (NLG). We are issuing this AD 

to prevent internal leakage of the selector 

valve, which, under certain conditions, could 

result in an uncommanded retraction of the 

NLG with consequent damage to the airplane 

and possible serious injury to ground 

personnel. 

Compliance 

(e) You are responsible for having the 

actions required by this AD performed within 

the compliance times specified, unless the 

actions have already been done. 

Inspection and Corrective Actions 

(f) Within 500 flight hours or 12 months 

after the effective date of this AD, whichever 

occurs first, inspect to determine the 

manufacturer part number (P/N) and S/N of 

the selector valves of the NLG and nose gear 

door. A review of airplane maintenance 

records is acceptable in lieu of this 

inspection if the S/Ns of the selector valves 

can be conclusively determined from that 

review. For any subject selector valve having 

Tactair Fluid Controls P/N 750006000 and a 

S/N from 0001 through 0767 inclusive, before 

further flight, do related investigative 

(including a general visual inspection for 

proper installation of the lock wire of the end 

cap) and corrective actions; in accordance 

with the applicable service bulletins 

identified in Table 1 of this AD. 

Note 1: Operators should be aware that 

selector valves having Bombardier P/N 

601R75146–1 may be supplied by different 

manufacturers and have different 

manufacturer part numbers. Only airplanes 

having selector valves manufactured by 

Tactair Fluid Controls, having P/N 

750006000, are subject to the investigative 

and corrective actions specified in paragraph 

(f) of this AD. 

Note 2: For the purposes of this AD, a 

general visual inspection is: ‘‘A visual 

examination of an interior or exterior area, 

installation, or assembly to detect obvious 

damage, failure, or irregularity. This level of 

inspection is made from within touching 

distance unless otherwise specified. A mirror 

may be necessary to ensure visual access to 

all surfaces in the inspection area. This level 

of inspection is made under normally 

available lighting conditions such as 

daylight, hangar lighting, flashlight, or 

droplight and may require removal or 

opening of access panels or doors. Stands, 

ladders, or platforms may be required to gain 

proximity to the area being checked.’’

Note 3: The service bulletins identified in 

Table 1 of this AD refer to Tactair Fluid 

Controls Service Bulletin SB750006000–1, 

Revision A, dated September 6, 2005, as an 

additional source of service information for 

doing the related investigative and corrective 

actions required by this AD. 

Actions Accomplished According to 

Previous Issue of Service Bulletin 

(g) Actions accomplished before the 

effective date of this AD according to 

Bombardier Service Bulletin 604–32–021, 

Revision 01, dated February 20, 2006 (for 

Model CL–600–2B16 (CL–604) airplanes), are 

considered acceptable for compliance with 

the corresponding actions specified in this 

AD. 

Alternative Methods of Compliance 

(AMOCs) 

(h)(1) The Manager, New York Aircraft 

Certification Office (ACO), FAA, has the 

authority to approve AMOCs for this AD, if 

requested in accordance with the procedures 

found in 14 CFR 39.19. 

(2) Before using any AMOC approved in 

accordance with § 39.19 on any airplane to 

which the AMOC applies, notify the 

appropriate principal inspector in the FAA 

Flight Standards Certificate Holding District 

Office. 

Related Information 

(i) Canadian airworthiness directive CF–

2006–16, dated July 6, 2006, also addresses 

the subject of this AD. 


jlentini on PROD1PC65 with PROPOSALS
20780 Federal Register / Vol. 72, No. 80 / Thursday April 26, 2007 / Proposed Rules 

Issued in Renton, Washington, on April 19, 

2007. 

Ali Bahrami, 

Manager, Transport Airplane Directorate, 

Aircraft Certification Service. 

[FR Doc. E7–7979 Filed 4–25–07; 8:45 am] 

BILLING CODE 4910–13–P 

DEPARTMENT OF TRANSPORTATION 

Federal Aviation Administration 

14 CFR Part 39 

[Docket No. FAA–2007–27680; Directorate 

Identifier 2007–CE–026–AD] 

RIN 2120–AA64 

Airworthiness Directives; 

AEROTECHNIC Vertriebs-u. Service 

GmbH Honeywell CAS67A ACAS II 

Systems Appliances 

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: 

It was detected by the STC holder that in 

earlier installations of the ACASII system 

there were no isolation diodes installed in 

the Heading and Attitude Valid lines. The 

absence of an isolation diode in the valid 

lines can prevent the valid flag to come up 

even if a gyro fault exists. The problem has 

only been detected for Heading Valid lines 

but could equally affect the Altitude Valid 

lines. 

With installation of the ACASII, the 

heading and attitude valid lines have to be 

connected to the TPU67A. On valid state, the 

signals are +28VDC. On invalid, the signals 

are open. This condition of direct connection 

(without an isolation diode installed) of the 

valid lines to the TPU67A, if not corrected, 

could cause the TPU67A to feed current into 

the open stated valid lines. This prevents the 

flag to appear even if the gyro is invalid, 

providing the flight crew with erroneous 

navigation information. 

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 May 29, 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: Go to 

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: Karl 

Schletzbaum, Aerospace Engineer, FAA, 

Small Airplane Directorate, 901 Locust, 

Room 301, Kansas City, Missouri 64106; 

telephone: (816) 329–4146; fax: (816) 

329–4090. 

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–2007–27680; Directorate Identifier 

2007–CE–026–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 European Aviation Safety Agency 

(EASA), which is the Technical Agent 

for the Member States of the European 

Community, has issued EASA AD No. 

2007–0059 dated March 5, 2007 

(referred to after this as ‘‘the MCAI’’), to 

correct an unsafe condition for the 

specified products. 

The MCAI states: 

It was detected by the STC holder that in 

earlier installations of the ACASII system 

there were no isolation diodes installed in 

the Heading and Attitude Valid lines. The 

absence of an isolation diode in the valid 

lines can prevent the valid flag to come up 

even if a gyro fault exists. The problem has 

only been detected for Heading Valid lines 

but could equally affect the Attitude Valid 

lines. 

With installation of the ACASII, the 

heading and attitude valid lines have to be 

connected to the TPU67A. On valid state, the 

signals are +28VDC. On invalid, the signals 

are open. This condition of direct connection 

(without an isolation diode installed) of the 

valid lines to the TPU67A, if not corrected, 

could cause the TPU67A to feed current into 

the open stated valid lines. This prevents the 

flag to appear even if the gyro is invalid, 

providing the flight crew with erroneous 

navigation information. 

For the reasons stated above, this 

Airworthiness Directive (AD) requires the 

installation of isolation diodes into the signal 

lines to the TPU67A to prevent reverse feed 

of the valid lines. 

You may obtain further information 

by examining the MCAI in the AD 

docket. 

Relevant Service Information 

Aerotechnic Vertiebs -u. Service 

GmbH has issued Service Bulletin No. 

DO228–119780–0104, Revision 2, dated 

December 21, 2006. The actions 

described in this service information are 

intended to correct the unsafe condition 

identified in the MCAI. 


jlentini on PROD1PC65 with PROPOSALS