[Federal Register Volume 60, Number 178 (Thursday, September 14, 1995)]
[Rules and Regulations]
[Pages 47679-47682]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-21957]



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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39

[Docket No. 91-CE-21-AD; Amendment 39-9358; AD 95-18-11]


Airworthiness Directives; de Havilland DHC-6 Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

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SUMMARY: This amendment supersedes Airworthiness Directive (AD) 73-05-
03, which currently requires repetitively inspecting the rear spar cap 
for cracks on certain de Havilland DHC-6 series airplanes, and 
replacing any cracked rear spar cap. The Federal Aviation 
Administration's policy on aging commuter-class aircraft is to 
eliminate or, in certain instances, reduce the number of certain 
repetitive short-interval inspections when improved parts or 
modifications are available. This action requires modifying the wing 
rear spar support (Modification No. 6/1301) as terminating action for 
the currently required repetitive inspections. The actions specified by 
this AD are intended to prevent cracking of the top flange of the wing 
spar attachment caps, which, if not detected and corrected, could 
result in loss of control of the airplane.

DATES: Effective October 26, 1995.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of October 26, 1995.

ADDRESSES: Service information that applies to this AD may be obtained 
from de Havilland, Inc., 123 Garratt Boulevard, Downsview, Ontario, 
Canada, M3K 1Y5. This information may also be examined at the Federal 
Aviation Administration (FAA), Central Region, Office of the Assistant 
Chief Counsel, Attention: Rules Docket 91-CE-21-AD, room 1558, 601 E. 
12th Street, Kansas City, Missouri 64106; or at the Office of the 
Federal Register, 800 North Capitol Street NW., suite 700, Washington, 
DC.

FOR FURTHER INFORMATION CONTACT: Jon Hjelm, Aerospace Engineer, FAA, 
New York Aircraft Certification Office, 10 Fifth Street, 3rd Floor, 
Valley Stream, New York 11581; telephone (516) 256-7523; facsimile 
(516) 568-2716.

SUPPLEMENTARY INFORMATION: A proposal to amend part 39 of the Federal 
Aviation Regulations (14 CFR part 39) to include an AD that would apply 
to certain de Havilland DHC-6 series airplanes without Modification No. 
6/1301 incorporated was published in the Federal Register on October 
31, 1994 (59 FR 54415). The action proposed to supersede AD 73-05-03 
with a new AD that would (1) initially retain the requirement of 
repetitively inspecting the wing rear spar cap for cracks and replacing 
any cracked part; and (2) eventually require installing wing rear spar 
attachment caps that are manufactured from a material having improved 
stress corrosion resistant properties (Modification 6/1301) as 
terminating action for the repetitive inspections. Accomplishment of 
the proposed actions would be in accordance with de Havilland Service 
Bulletin No. 6/295, Revision D, dated December 20, 1991.
    Interested persons have been afforded an opportunity to participate 
in the making of this amendment. No comments were received on the 
proposed rule or the FAA's determination of the cost to the public.
    After careful review of all available information related to the 
subject presented above including the referenced service information, 
the FAA 

[[Page 47680]]
has determined that air safety and the public interest require the 
adoption of the rule as proposed except for minor editorial 
corrections. The FAA has determined that these minor corrections will 
not change the meaning of the AD and will not add any additional burden 
upon the public than was already proposed.
    The FAA estimates that 82 airplanes in the U.S. registry will be 
affected by this AD, that it will take approximately 22 workhours per 
airplane to accomplish the required modification, and that the average 
labor rate is approximately $60 an hour. Parts cost approximately 
$6,350 per airplane. Based on these figures, the total cost impact of 
this AD on U.S. operators is estimated to be $628,940. This figure is 
based upon the assumption that no affected airplane owner/operator has 
incorporated Modification 6/1301.
    The intent of the FAA's aging commuter airplane program is to 
ensure safe operation of commuter-class airplanes that are in 
commercial service without adversely impacting private operators. Of 
the approximately 82 airplanes in the U.S. registry that will be 
affected by this AD, the FAA has determined that approximately 45 
percent are operated in scheduled passenger service. A significant 
number of the remaining 55 percent are operated in other forms of air 
transportation such as air cargo and air taxi.
    The following paragraphs present cost scenarios for airplanes where 
no cracks were found and where certain category cracks were found 
during the inspections, and where the remaining airplane life is 15 
years with an average annual utilization rate of 1,600 hours time-in-
service (TIS). A copy of the full Cost Analysis and Regulatory 
Flexibility Determination for the required action may be examined at 
the FAA, Central Region, Office of the Assistant Chief Counsel, 
Attention: Rules Docket No. 91-CE-21-AD, Room 1558, 601 E. 12th Street, 
Kansas City, Missouri.
     No Cracks Scenario: Under the provisions of AD 73-05-03, 
an owner/operator of an affected de Havilland DHC-6 series airplane in 
scheduled service who operates an average of 1,600 hours TIS annually 
will inspect every 26 weeks. This amounts to a remaining airplane life 
(estimated 15 years) cost of $14,058; this figure is based on the 
assumption that no cracks are found during the inspections. This AD 
will incur the inspection at one 1,200-hour TIS interval and then, at 
2,400 hours TIS after the effective date of the AD, the operator has to 
replace the top flange of the wing spar attachment caps (eliminating 
the need for further repetitive inspections). This results in a present 
value cost of $8,331, which is a present value cost savings over that 
required in AD 73-05-03 of $5,727 or $4,154 annualized over the 1.5 
years it will take to accumulate 2,400 hours TIS. An owner of a general 
aviation airplane who operates 800 hours TIS annually without finding 
any cracks during the 1,200-hour TIS inspection will incur a present 
value cost savings over that required in AD 73-05-03 of $6,430. This 
amounts to a per year savings of $2,450 over the 1.5 years it takes to 
accumulate 2,400 hours TIS.
     Category I cracks found scenario: These are spanwise 
cracks that are inboard of the third rivet, or spanwise cracks that 
exceed 50 inches, or any chordwise cracks. Under the provisions of AD 
73-05-03, an owner/operator who finds cracks during an inspection under 
this scenario has to immediately repair the cracked part and 
repetitively inspect every 26 weeks. This AD will require immediate 
replacement as terminating action for the repetitive inspections, which 
results in present value compliance costs of $8,355. The present value 
cost savings over that required in AD 73-05-03 for this scenario is 
$6,300 for airplanes in scheduled service and $6,295 per general 
aviation airplane.
      Category II cracks found scenario: These are spanwise 
cracks that are outboard of the 10th rivet and within the limits of 
paragraph (b) of the service bulletin. Under the provisions of AD 73-
05-03, an owner/operator who finds cracks during an inspection under 
this scenario has to repetitively inspect every 13 weeks. This results 
in present value compliance costs of $27,625. This AD would require 
repetitive inspections every 600 hours TIS until replacement of the top 
flange of the wing rear spar attachment caps at 2,400 hours TIS after 
the effective date of the AD as terminating action for the repetitive 
inspections. This results in present value compliance costs of $9,700. 
Immediate replacement of the top flange is more economical than 
repetitively inspecting; present value costs are $8,355. The present 
value cost savings over that required in AD 73-05-03 for this scenario 
is $19,272 per airplane in scheduled service and $19,269 per general 
aviation airplane.
     Category III cracks found scenario: These are spanwise 
cracks that are outboard of the 10th rivet and within the limits of 
paragraph (c) of the service bulletin. Under the provisions of AD 73-
05-03, an owner/operator who finds cracks during an inspection in this 
scenario has to repetitively inspect every 2 weeks. This results in 
present value compliance costs of $175,000. This AD requires repetitive 
inspections every 100 hours TIS until replacement of the top flange of 
the wing rear spar attachment caps at 2,400 hours TIS after the 
effective date of the AD as terminating action for the repetitive 
inspections. This results in present value compliance costs of $13,965. 
Immediate replacement of the top flange is more economical than 
repetitively inspecting; present value costs are $8,355. The present 
value cost savings over that required in AD 73-05-03 for this scenario 
is $166,075 per airplane in scheduled service and $166,784 per general 
aviation airplane.
     Category IV cracks found scenario: These are spanwise 
cracks that are outboard of the 10th rivet and exceed the limits of 
paragraph (b) or (c) of the service bulletin. Also included are cracks 
in the splice plates of the vertical and horizontal legs of the rear 
spar or elongated rivet holes. Under the provisions of AD 73-05-03, an 
owner/operator who finds cracks during an inspection under this 
scenario has to immediately repair any crack and then repetitively 
inspect every 26 weeks. This results in present value costs of $14,500. 
This AD requires immediate crack repair, then an inspection after 
accumulating 1,200 hours TIS, and replacement of the top flange of the 
wing rear spar attachment caps at 2,400 hours TIS after the effective 
date of the AD as terminating action for the repetitive inspections. 
This results in present value compliance costs of $8,929. Immediate 
replacement of the top flange is more economical than repetitively 
inspecting; present value costs are $8,355. The present value cost 
savings over that required in AD 73-05-03 for this scenario is $6,040 
per airplane in scheduled service and $6,430 per general aviation 
airplane.
     Category V cracks found scenario: These are spanwise 
cracks that are between the third and tenth rivet. Under the provisions 
of AD 73-05-03, an owner/operator who finds cracks during an inspection 
under this scenario has to immediately repair any crack, repetitively 
inspect every 2 weeks, replace the top flange of the wing rear spar 
attachment caps, and repetitively inspect thereafter every 26 weeks. 
This results in present value compliance costs of about $30,000. This 
AD requires immediate crack repair, repetitive inspections every 50 
hours TIS, and replacement of the top flange of the wing rear spar 
attachment caps at 2,400 hours TIS after the effective date of the AD 
as terminating action for the repetitive inspections. This results in 
present value compliance costs of 

[[Page 47681]]
$38,988. Immediate replacement of the top flange is more economical 
than repetitively inspecting; present value costs are $8,355. The 
present value cost savings over that required in AD 73-05-03 for this 
scenario are $19,356 per airplane in scheduled service and $26,367 per 
general aviation airplane.
     Category VI cracks found scenario: These are spanwise 
cracks that have a total length exceeding 30 inches but not exceeding 
50 inches. Under the provisions of AD 73-05-03, an owner/operator who 
finds cracks during an inspection under this scenario has to 
immediately repair any crack, replace the top flange of the wing rear 
spar attachment caps at 26 weeks, and repetitively inspect thereafter 
every 26 weeks. This results in present value compliance costs of about 
$21,200. This AD requires immediate crack repair, repetitive 
inspections every 600 hours TIS, and replacement of the top flange of 
the wing rear spar attachment caps at 2,400 hours TIS after the 
effective date of the AD as terminating action for the repetitive 
inspections. This results in present value compliance costs of $10,289. 
Immediate replacement of the top flange is more economical than 
repetitively inspecting; present value costs are $8,355. The present 
value cost savings over that required in AD 73-05-03 for this scenario 
is $12,707 per airplane in scheduled service and $13,028 per general 
aviation airplane.
    The Regulatory Flexibility Act of 1980 (RFA) was enacted by 
Congress to ensure that small entities are not unnecessarily or 
disproportionally burdened by government regulations. The RFA requires 
government agencies to determine whether rules could have a 
``significant economic impact on a substantial number of small 
entities,'' and, in cases where they could, conduct a Regulatory 
Flexibility Analysis in which alternatives to the rule are considered. 
FAA Order 2100.14A, Regulatory Flexibility Criteria and Guidance, 
outlines FAA procedures and criteria for complying with the RFA. Small 
entities are defined as small businesses and small not-for-profit 
organizations that are independently owned and operated or airports 
operated by small governmental jurisdictions. A ``substantial number'' 
is defined as a number that is not less than 11 and that is more than 
one-third of the small entities subject to a rule, or any number of 
small entities judged to be substantial by the rulemaking official. A 
``significant economic impact'' is defined by an annualized net 
compliance cost, adjusted for inflation, which is greater than a 
threshold cost level for defined entity types. FAA Order 2100.14A sets 
the size threshold for small entities operating aircraft for hire at 9 
aircraft owned and the annualized cost thresholds, adjusted to 1994 
dollars, at $69,000 for scheduled operators and $5,000 for unscheduled 
operators.
    Of the 82 U.S.-registered airplanes affected by this AD, three 
airplanes are owned by the federal government. Of the other 79, one 
business owns 24 airplanes, one business owns 7 airplanes, one business 
owns 6 airplanes, one business owns 3 airplanes, 6 businesses own 2 
airplanes each, and twenty-seven businesses own 1 airplane each.
    As presented in the crack scenario discussion, replacing the top 
flange of the wing rear spar attachment caps immediately or within 
2,400 hours TIS after the effective date of this AD is more economical 
in all scenarios than continuing to repetitively inspect the part for 
the life of the airplane. Therefore, this AD will not have a 
``significant economic impact on a substantial number of small 
entities.''
    The regulations adopted herein will not have substantial direct 
effects 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. Therefore, in 
accordance with Executive Order 12612, it is determined that this final 
rule does not have sufficient federalism implications to warrant the 
preparation of a Federalism Assessment.
    For the reasons discussed above, I certify that this action (1) is 
not a ``significant regulatory action'' under Executive Order 12866; 
(2) is not a ``significant rule'' under 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. A copy of the final evaluation prepared for this 
action is contained in the Rules Docket. A copy of it may be obtained 
by contacting the Rules Docket at the location provided under the 
caption ADDRESSES.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Incorporation by 
reference, Safety.

Adoption of the Amendment

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the Federal Aviation Administration amends part 39 of 
the Federal Aviation Regulations (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), 40101, 40113, 44701.


Sec. 39.13  [Amended]

    2. Section 39.13 is amended by removing Airworthiness Directive 
(AD) 73-05-03, Amendment 39-1658, and adding a new AD to read as 
follows:

95-18-11  De Havillland: Amendment 39-9358; Docket No. 91-CE-21-AD.

    Supersedes AD 73-05-03, Amendment 39-1658.
    Applicability: Models DHC-6-1, DHC-6-100, DHC-6-200, and DHC-6-
300 airplanes (serial numbers 1 to 330), certificated in any 
category, that have not incorporated Modification 6/1301 in 
accordance with the instructions in Part C of de Havilland Service 
Bulletin (SB) 6/295, Revision D, dated December 20, 1991.

    Note 1: This AD applies to each airplane identified in the 
preceding applicability revision, regardless of whether it has been 
modified, altered, or repaired in the area subject to the 
requirements of this AD. For airplanes that have been modified, 
altered, or repaired so that the performance of the requirements of 
this AD is affected, the owner/operator must request approval for an 
alternative method of compliance in accordance with paragraph (f) of 
this AD. The request should include an assessment of the effect of 
the modification, alteration, or repair on the unsafe condition 
addressed by this AD; and, if the unsafe condition has not been 
eliminated, the request should include specific proposed actions to 
address it.

    Compliance: Required as indicated in the body of this AD, unless 
already accomplished.
    To prevent cracking of the top flange of the wing rear spar 
attachment caps, which, if not detected and corrected, could result 
in loss of control of the airplane, accomplish the following:
    (a) Within the next 100 hours time-in-service (TIS) after the 
effective date of this AD, inspect both wing rear spar attachment 
caps, part number (P/N) C6WM1032, for cracks in accordance with 
paragraph A of the Accomplishment Instructions section of de 
Havilland SB No. 6/295, Revision D, dated December 20, 1991. The 
exposure time of Inspection Method A.1 (Radiographic) in this 
service bulletin shall be 120 seconds instead of 60 seconds for the 
inboard X-ray tube location, and the X-ray beam angle shall be 
decreased from 10 degrees to 5 degrees for all X-ray tube locations.
    (1) If cracking is not detected, reinspect each cap every 1,200 
hours TIS until a Modification 6/1301 spar cap is installed as 
required by paragraph (c) of this AD.
    (2) If spanwise cracking is detected outboard of the 10th rivet, 
accomplish the following:

[[Page 47682]]

    (i) For cracks that have the following (the criteria of 
paragraph (c) in the Compliance section of de Havilland SB No. 6/
295, Revision D, dated December 20, 1991):


First to tenth rivet.............  No cracks.                           
11th to 29th rivet...............  One cracked pitch (the distance      
                                    between adjacent rivet holes) in ten
                                    pitches with four uncracked pitches 
                                    minimum between cracks.             
30th to 69th rivet...............  Two cracked pitches in ten pitches   
                                    with four uncracked pitches minimum 
                                    between cracks.                     
70th to 74th (end)...............  One cracked pitch.                   
                                                                        

Repeat the inspection specified in paragraph (a) of this AD at 
intervals not to exceed 100 hours TIS until a Modification 6/1301 
spar cap is installed as required by paragraph (c) of this AD.
    (ii) For cracks found outboard of the 10th rivet that run only 
between two adjacent rivets provided not more than four such cracks 
exist in an attachment cap and a minimum of two rivet pitch lengths 
of uncracked material separate cracks (the criteria of paragraph (b) 
in the Compliance section of de Havilland SB No. 6/295), repeat the 
inspection specified in paragraph (a) of this AD at intervals not to 
exceed 600 hours TIS until a Modification 6/1301 spar cap is 
installed as required by paragraph (c) of this AD.
    (iii) For cracks that meet or exceed the criteria of paragraphs 
(b) or (c) in the Compliance section of de Havilland SB No. 6/295, 
prior to further flight, reinforce the spar cap in accordance with 
paragraph B of the Accomplishment Instructions section of de 
Havilland SB No. 6/295, Revision D, dated December 20, 1991, and 
repeat the inspection specified in paragraph (a) of this AD at 
intervals not to exceed 1,200 hours TIS until a Modification 6/1301 
spar cap is installed as required by paragraph (c) of this AD.
    (3) If spanwise cracking is detected inboard of the third rivet, 
or if a chordwise crack is detected, or if the total length of 
cracks on a cap exceeds 50 inches, prior to further flight, replace 
the spar cap with a Modification 6/1301 cap in accordance with 
paragraph C of the Accomplishment Instructions section of de 
Havilland SB No. 6/295, Revision D, dated December 20, 1991.
    (4) If spanwise cracking is detected between the third and tenth 
rivet, prior to further flight, reinforce the spar cap in accordance 
with paragraph B of the Accomplishment Instructions section of de 
Havilland SB No. 6/295, Revision D, dated December 20, 1991, and 
repeat the inspection specified in paragraph (a) of this AD inboard 
of the reinforced attachment caps at intervals not to exceed 50 
hours TIS until a Modification 6/1301 spar cap is installed as 
required by paragraph (c) of this AD.
    (5) If cracking exceeds a total length of 30 inches but does not 
exceed 50 inches, prior to further flight, reinforce the spar cap in 
accordance with paragraph B of the Accomplishment Instructions 
section of de Havilland SB No. 6/295, Revision D, dated December 20, 
1991, and repeat the inspection specified in paragraph (a) of this 
AD at intervals not to exceed 600 hours TIS until a Modification 6/
1301 spar cap is installed as required by paragraph (c) of this AD.
    (b) Within 100 hours after the effective date of this AD and 
thereafter at intervals not to exceed 1,200 hours TIS until a 
Modification 6/1301 spar cap is installed as required by paragraph 
(c) of this AD, inspect the splice plates of the vertical and 
horizontal legs of the rear spar fitting at Wing Stations 87 to 91 
for cracks or elongated rivet holes. Prior to further flight, 
replace any part that is cracked or has elongated rivet holes with a 
serviceable part.
    (c) Within 2,400 hours TIS after the effective date of this AD, 
replace both wing rear spar caps with a Modification 6/1301 spar cap 
in accordance with paragraph C of the Accomplishment Instructions in 
de Havilland SB No. 6/295, Revision D, dated December 20, 1991, 
unless already accomplished.
    (d) Incorporating Modification 6/1301 on both wing rear spar 
caps in accordance with paragraph C of the Accomplishment 
Instructions in de Havilland SB No. 6/295, Revision D, dated 
December 20, 1991, is considered terminating action for the 
inspection requirements of this AD.
    (e) Special flight permits may be issued in accordance with 
sections 21.197 and 21.199 of the Federal Aviation Regulations (14 
CFR 21.197 and 21.199) to operate the airplane to a location where 
the requirements of this AD can be accomplished.
    (f) An alternative method of compliance or adjustment of the 
initial or repetitive compliance times that provides an equivalent 
level of safety may be approved by the Manager, New York Aircraft 
Certification Office (ACO), FAA, 10 Fifth Street, 3rd Floor, Valley 
Stream, New York 11581. The request shall be forwarded through an 
appropriate FAA Maintenance Inspector, who may add comments and then 
send it to the Manager, New York ACO.

    Note 2: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the New York ACO.

    (g) The inspections and modification required by this AD shall 
be done in accordance with de Havilland Service Bulletin No. 6/295, 
Revision D, dated December 20, 1991. This incorporation by reference 
was approved by the Director of the Federal Register in accordance 
with 5 U.S.C. 552(a) and 1 CFR part 51. Copies may be obtained from 
de Havilland, Inc., 123 Garratt Boulevard, Downsview, Ontario M3K 
1Y5 Canada. Copies may be inspected at the FAA, Central Region, 
Office of the Assistant Chief Counsel, Room 1558, 601 E. 12th 
Street, Kansas City, Missouri, or at the Office of the Federal 
Register, 800 North Capitol Street, NW., 7th Floor, suite 700, 
Washington, DC.
    (h) This amendment (39-9358) supersedes AD 73-05-03, Amendment 
39-1658.
    (i) This amendment (39-9358) becomes effective on October 26, 
1995.

    Issued in Kansas City, Missouri, on August 28, 1995.
Henry A. Armstrong,
Acting Manager, Small Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 95-21957 Filed 9-13-95; 8:45 am]
BILLING CODE 4910-13-U