DEPARTMENT OF TRANSPORTATION

FEDERAL AVIATION ADMINISTRATION

14 CFR Part 39

[Docket  No.  FAA-2005-22558; Directorate  Identifier  2005-NM-107-AD] RIN
2120-AA64

AIRWORTHINESS DIRECTIVES; Cessna Model 500, 550, S550, 560, 560XL, and 750
Airplanes

AGENCY:  Federal Aviation Administration (FAA),  Department of  Transport-
ation (DOT).

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: The FAA proposes to adopt a new airworthiness directive (AD)  for
certain Cessna Model 500, 550,  S550, 560, 560XL, and 750  airplanes. This
proposed AD would require  installing identification sleeves on  the wires
for  the  positive  and  negative  terminal  studs  of  the  engine and/or
auxiliary power unit (APU) fire extinguishing bottles, as applicable,  and
re-connecting the wires  to the correct  terminal studs. This  proposed AD
results from  a report  of mis-wired  fire extinguishing  bottles. We  are
proposing  this  AD to  ensure  that the  fire  extinguishing bottles  are
activated in the event of an engine or APU fire, and that flammable fluids
are not supplied  during a fire,  which could result  in an unextinguished
fire in the nacelle or APU.

DATES: We must receive comments on this proposed AD by November 14, 2005.

ADDRESSES: Use one of the  following addresses to submit comments  on this
proposed AD.

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 Cessna Aircraft Co., P.O. Box 7706, Wichita, Kansas 67277, for the
service information identified in this proposed AD.

FOR FURTHER INFORMATION CONTACT:  Robert D. Adamson,  Aerospace  Engineer,
Systems   and   Propulsion  Branch,   ACE-116W,   FAA,  Wichita   Aircraft
Certification Office, 1801 Airport Road, Room 100, Mid-Continent  Airport,
Wichita, Kansas 67209; telephone (316) 946-4145; fax (316) 946-4107.

SUPPLEMENTARY INFORMATION:

COMMENTS INVITED

We invite  you to  submit any  relevant written  data, views, or arguments
regarding this proposed  AD. Include the  docket number "FAA-  2005-22558;
Directorate Identifier 2005-NM-107-AD" at the beginning of your  comments.
We  specifically  invite  comments on  the  overall  regulatory, economic,
environmental, and energy aspects of the proposed AD. We will consider all
comments received by  the closing date  and may amend  the proposed AD  in
light 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  with
FAA personnel concerning  this proposed AD.  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 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 of the Nassif Building at the DOT street address stated in the
ADDRESSES section.  Comments will  be available  in the  AD docket shortly
after the Docket Management System receives them.

DISCUSSION

We have received a report  indicating that the auxiliary power  unit (APU)
fire  extinguishing  system  was  mis-wired  on  some  Cessna  Model   750
airplanes.  Although  the main  engine  fire extinguishing  system  on all
Cessna  Model  750  airplanes is  wired  correctly,  further investigation
revealed that the fire extinguishing systems on the main engines of Cessna
Model 500, 550, S550, 560 airplanes,  and on the main engines and  APUs of
Cessna Model 560XL airplanes may not be wired correctly. Therefore, all of
these models may be subject to the same or similar unsafe condition  found
on  the  Cessna  Model  750 APU  installation.  The  engine  and APU  fire
extinguishing bottles on these airplane models have positive and  negative
terminal studs that are the same size, so it is possible to  cross-connect
the wiring  of the  positive and  negative leads.  If the  wiring is cross
-connected and the fire  extinguishing bottles are activated,  the circuit
breaker may trip  due to the  direct ground on  the positive lead,  and no
fire  extinguishing  agent  would  be  expelled.  In  addition,  with  the
exception of the Model 750  APU installation, the tripped circuit  breaker
removes power from the fuel  and hydraulic firewall shutoff valves,  which
are powered  closed from  a normally  open state,  and from the associated
cockpit indications. As  a result, flammable  fluids could continue  to be
supplied  to the  area during  a fire.  It should  be noted  that the  APU
installation on the Cessna Model  750 airplanes has a solenoid  valve that
is powered open from the normally closed state and would close to shut off
fuel with the disruption of power. The circuit breaker that provides power
to the extinguishing bottle differs from the circuit breaker that controls
the shutoff valve that is  powered on. Finally, the flightcrew  would know
that  the  fire  had  not  been  extinguished  because  the  engine   fire
annunciator would stay illuminated, and the annunciators for the  firewall
shutoff valve may not  illuminate if the valve  does not close. Thus,  the
flightcrew would not  know why the  fire had not  been extinguished. These
conditions, if not  corrected, could result  in an unextinguished  fire in
the nacelle or APU.

RELEVANT SERVICE INFORMATION

We have reviewed the Cessna service bulletins in the table below.

                       CESSNA SERVICE BULLETINS
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   FOR CESSNA         SERVICE
   AIRPLANE MODEL     BULLETIN          REVISION          DATE
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       500            500-26-02         Original      April 1, 2005
       550            550-26-05         Original      April 1, 2005
       S550           S550-26-02        Original      April 1, 2005
       560            560-26-01         Original      April 1, 2005
       560XL          560XL-26-02       1             December 22, 2004
       750            750-26-05         Original      November 24, 2004
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The service  bulletins describe  procedures for  installing identification
sleeves on the wires for the  positive and negative terminal studs of  the
engine and/or APU fire extinguishing bottles; re- connecting the wires  to
the correct  studs; testing  the connection;  and, for  all but the Cessna
Model  750  airplanes,  re-connecting the  wires  if  necessary until  the
connection  tests correctly.  For Cessna  Model 500,  550, S550,  and  560
airplanes,  these  actions  are done  for  the  engine fire  extinguishing
bottles only. For Cessna Model  750 airplanes, these actions are  done for
the APU fire extinguishing bottle only. For Cessna Model 560XL  airplanes,
this action is  done for both  the engine and  the APU fire  extinguishing
bottles. The service bulletins also  specify that operators should send  a
maintenance  transaction  report to  the  manufacturer. Accomplishing  the
actions specified  in the  service information  is intended  to adequately
address the unsafe condition.

FAA'S DETERMINATION AND REQUIREMENTS OF THE PROPOSED AD

We  have  evaluated all  pertinent  information and  identified  an unsafe
condition that is likely  to exist or develop  on other airplanes of  this
same type design. For this reason,  we are proposing this AD, which  would
require accomplishing  the actions  specified in  the service  information
described previously, except as  discussed under "Differences Between  the
Proposed AD and the Service Bulletins."

DIFFERENCES BETWEEN THE PROPOSED AD AND THE SERVICE BULLETINS

Operators should  note that,  although the  Accomplishment Instructions of
the  referenced service  bulletins describe  procedures for  submitting  a
maintenance transaction report to the manufacturer, this proposed AD would
not require that action. We do not need this information from operators.

CLARIFICATION OF SERVICE BULLETIN 750-26-05

Although Cessna Service Bulletin 750-26-05 does not specify procedures for
re-connecting the wires if necessary until the connection tests correctly,
that action is implied  in the service bulletin  and would be required  in
this proposed AD.

COSTS OF COMPLIANCE

There are about  2,801 airplanes of  the affected design  in the worldwide
fleet. The following table provides the estimated costs for U.S. operators
to comply with this proposed AD.

                                ESTIMATED COSTS
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                          AVERAGE
                          LABOR
                          RATE                     NUMBER OF U.S.-
MODIFICATION FOR   WORK   PER            COST PER   REGISTERED
CESSNA MODEL--     HOURS  HOUR   PARTS   AIRPLANE   AIRPLANES  FLEET COST
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500, 550, S550,
 and 560 airplanes   3    $65     $50      $245       1,827     $447,615
560XL airplanes      4     65     100       360         331      119,160
750 airplanes        2     65      25       155         211       32,705
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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 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 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.

SEC. 39.13 [AMENDED]

2. The Federal Aviation Administration (FAA) amends Sec.  39.13 by  adding
the following new airworthiness directive (AD):