[Federal Register Volume 62, Number 33 (Wednesday, February 19, 1997)]
[Proposed Rules]
[Pages 7373-7375]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-3961]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 96-CE-40-AD]
RIN 2120-AA64


Airworthiness Directives; Grob Luft-und Raumfahrt, GmbH; Models G 
109 and G 109B Sailplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: This document proposes to adopt a new airworthiness directive 
(AD) that would apply to certain Grob Luft-und Raumfahrt (Grob) Models 
G 109 and G 109B sailplanes. The proposed action would require 
inspecting the landing gear retaining bars and landing gear legs for 
proper radius, thickness, and cracking, and installing additional 
supportive parts or replacing the retaining bars and landing legs with 
parts of improved design. Reports of landing gear failure on certain G 
109 and G 109B sailplanes prompted the proposed action. The actions 
specified by the proposed AD are intended to prevent failure of the 
landing gear legs and possible loss of the sailplane.

DATES: Comments must be received on or before April 21, 1997.

ADDRESSES: Submit comments on the proposal in triplicate to the Federal 
Aviation Administration (FAA), Central Region, Office of the Assistant 
Chief Counsel, Attention: Rules Docket No. 96-CE-40-AD, Room 1558, 601 
E. 12th Street, Kansas City, Missouri 64106. Comments may be inspected 
at this location between 8 a.m. and 4 p.m., Monday through Friday, 
holidays excepted.
    Service information that applies to the proposed AD may be obtained 
from Grob Luft-und Raumfahrt, GmbH., D-8939, Mattsies-am Flugplatz, 
Germany. This information also may be examined at the Rules Docket at 
the address above.

FOR FURTHER INFORMATION CONTACT: Mr. J. Mike Kiesov, Project Officer, 
Sailplanes, FAA, Small Airplane Directorate, 1201 Walnut, suite 900, 
Kansas City, Missouri 64106; telephone (816) 426-6932; facsimile (816) 
426-2169.

SUPPLEMENTARY INFORMATION:

Comments Invited

    Interested persons are invited to participate in the making of the 
proposed rule by submitting such written data, views, or arguments as 
they may desire. Communications should identify the Rules Docket number 
and be submitted in triplicate to the address specified above. All 
communications received on or before the closing date for comments, 
specified above, will be considered before taking action on the 
proposed rule. The proposals contained in this notice may be changed in 
light of the comments received.
    Comments are specifically invited on the overall regulatory, 
economic, environmental, and energy aspects of the proposed rule. All 
comments submitted will be available, both before and after the closing 
date for comments, in the Rules Docket for examination by interested 
persons. A report that summarizes each FAA-public contact concerned 
with the substance of this proposal will be filed in the Rules Docket.
    Commenters wishing the FAA to acknowledge receipt of their comments 
submitted in response to this notice must submit a self-addressed, 
stamped postcard on which the following statement is made: ``Comments 
to Docket No. 96-CE-40-AD.'' The postcard will be date stamped and 
returned to the commenter.

Availability of NPRMs

    Any person may obtain a copy of this NPRM by submitting a request 
to the FAA, Central Region, Office of the Assistant Chief Counsel, 
Attention: Rules Docket No. 96-CE-40-AD, Room 1558, 601 E. 12th Street, 
Kansas City, Missouri 64106.

Discussion

    The Luftfahrt-Bundesamt (LBA), which is the airworthiness authority 
for Germany, recently notified the FAA that an unsafe condition may 
exist on certain Grob G 109 and G 109B sailplanes. The LBA reports that 
the landing gear on three of these sailplanes failed during landing. An 
investigation of these incidents revealed landing gear legs with 
fatigue cracks and weak retaining bars from an error in the 
manufacturing process. This condition, if not detected and corrected, 
could result in landing gear failure and possible loss of the 
sailplane.

Related Service Information

    Grob has issued Service Bulletin TM 817-39, dated January 4, 1994, 
which specifies procedures for inspecting and modifying or replacing 
the landing gear retaining bars and the landing gear legs. The landing 
gear retaining bar should have a minimum radius of 3.0 millimeters (mm) 
on the chamfer. If the

[[Page 7374]]

radius is less than 3.0 mm, the retaining bar would be replaced with an 
improved retaining bar (part number (P/N) 109-5000.02) and a plastic 
reinforcing strip (P/N 109-5000.07). If the radius is 3.0 mm or 
greater, the plastic reinforcing strip would be glued onto the 
retaining bars.
    The landing gear legs that are not marked with ``0'' (zero) would 
require inspecting for cracks by the magnetic particle or x-ray method, 
and if there are any cracks measuring greater than 0.5 mm, the landing 
gear legs would be replaced with new legs. If there are cracks 
measuring less than 0.5 mm, the proposed action would require polishing 
the cracks out, unless polishing would reduce the total leg thickness 
to less than 13.0 mm. If the leg thickness is less than 13.0 mm, the 
landing gear leg would be replaced. If there are no cracks in the 
landing gear legs, or the landing gear leg thickness is greater than 
13.0 mm, after polishing, the proposed action would require 
repetitively inspecting until cracks are found, or until new landing 
gear legs are installed. Installing the improved landing gear legs and 
the improved retaining bars would terminate the proposed repetitive 
inspection.
    The LBA classified this service bulletin as mandatory and issued AD 
94-004/2 Grob, dated February 3, 1994, in order to ensure the continued 
airworthiness of these sailplanes in Germany.

FAA's Determination

    These sailplane models are manufactured in Germany and are type 
certificated for operation in the United States under the provisions of 
section 21.29 of the Federal Aviation Regulations (14 CFR 21.29) and 
the applicable bilateral airworthiness agreement. Pursuant to this 
bilateral airworthiness agreement, the LBA has kept the FAA informed of 
the situation described above. The FAA has examined the findings of the 
LBA, reviewed all available information including the service 
information referenced above, and determined that AD action is 
necessary for products of this type design that are certificated for 
operation in the United States.

Explanation of the Provisions of the Proposed AD

    Since an unsafe condition has been identified that is likely to 
exist or develop in other Grob G 109 and G 109B sailplanes of the same 
type design registered in the United States, the proposed AD would 
require:
    (1) Inspecting the retaining bars chamfer for the correct radius, 
and replacing the bars or reinforcing the bars, as applicable.
    (2) Inspecting the landing gear legs that are not marked with ``0'' 
(zero) on the front of the legs for fatigue cracks, and if cracks are 
greater than or less than the tolerance measurement, either replace or 
repetitively inspect the landing gear legs, as applicable.
    (3) Measure the total thickness of the landing gear legs. If they 
measure less than, greater than or equal to 13.0 mm, continue to 
inspect or replace legs with new improved legs, as applicable.
    (4) Replacing the landing gear legs with parts of improved design 
would terminate the proposed repetitive inspections.

Cost Impact

    The FAA estimates that 63 sailplanes in the U.S. registry would be 
affected by the proposed AD, that it would take approximately 2 
workhours per leg per sailplane to accomplish the inspection and 
modification on the proposed retaining bar action, approximately 9 
workhours per leg per sailplane to accomplish the removal, inspection 
and re-installation, and approximately 6 workhours per leg to 
accomplish the replacement. The average labor rate is approximately $60 
an hour. Parts cost approximately $90 per sailplane for retaining bars 
and $1800 per sailplane for landing gear legs. The plastic strip for 
the retaining bar is provided by the manufacturer at no charge. 
Breaking these costs down by individual action, the estimated total 
cost for each action would be as follows:

--The proposed inspection and modification of the retaining bars would 
be $210 ($120/labor + $90/parts) per sailplane or $13,230 for the U.S. 
fleet.
--The proposed inspection and polishing of the landing gear legs would 
be $540 per sailplane or $34,020 for the U.S. fleet.
--The proposed replacement of the landing gear legs would be $2,160 
($360/labor + $1,800/parts) per sailplane or $136,080 for the U.S. 
fleet.
--The cost for the proposed repetitive inspections on the landing gear 
legs is not included in the above figures.

    The manufacturer has informed the FAA that they have dispatched 
equipment to outfit approximately 30 sailplanes with new retaining 
bars, reducing the estimated cost impact of the retaining bars from 
$13,230 to $6,930. The manufacturer has also distributed approximately 
3 sets of new landing gear legs, reducing the estimated total cost 
impact of the landing gear leg replacement from $136,080 to $129,600.

Proposed Compliance Time

    The compliance time of the proposed AD is presented in calendar 
time instead of hours time-in-service (TIS). The FAA has determined 
that a calendar time compliance is the most desirable method because 
the unsafe condition of the landing gear legs described by this AD is 
caused by corrosion. Corrosion initiates as a result of sailplane 
operation, but can continue to develop regardless of whether the 
sailplane is in service or in storage. Therefore, to ensure that the 
above-referenced condition is detected and corrected on all sailplanes 
within a reasonable period of time without inadvertently grounding any 
sailplanes, a compliance schedule based upon calendar time instead of 
hours TIS is required.

Regulatory Impact

    The regulations proposed herein would 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 
proposal would 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) if promulgated, 
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 draft regulatory evaluation 
prepared for this action has been placed 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, Safety.

The Proposed Amendment

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the Federal Aviation Administration proposes to amend 
part 39 of the Federal Aviation Regulations (14 CFR part 39) as 
follows:

[[Page 7375]]

PART 39--AIRWORTHINESS DIRECTIVES

    1. The authority citation for part 39 continues to read as follows:

    Authority: 49 USC 106(g), 40113, 44701.


Sec. 39.13  [Amended]

    2. Section 39.13 is amended by adding a new airworthiness directive 
(AD) to read as follows:

Grob Luft-Und Raumfahrt, GMBH. (GROB): Docket No. 96-CE-40-AD.

    Applicability: Models G 109 and G 109B sailplanes, all serial 
numbers, certificated in any category.

    Note 1: This AD applies to each sailplane identified in the 
preceding applicability provision, regardless of whether it has been 
modified, altered, or repaired in the area subject to the 
requirements of this AD. For sailplanes 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 (e) 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 failure of the landing gear legs and possible loss of 
the sailplane, accomplish the following:
    (a) Within the next 120 calendar days after the effective date 
of this AD, inspect the retaining bars chamfer on both landing gear 
legs for a minimum of 3.0 millimeters (mm) radius in accordance with 
the ``Actions'' section, paragraph A3 in Grob Service Bulletin (SB) 
817-39, dated January 4, 1994.
    (1) If the chamfer radius is 3.0 mm or greater, prior to further 
flight, glue a reinforcing plastic strip (part number (P/N) 109-
5000.07) to the retaining bar in accordance with the ``Actions'' 
section, paragraph A4 in Grob SB 817-39, dated January 4, 1994.
    (2) If the chamfer radius is less than 3.0 mm, prior to further 
flight, replace with a new improved retaining bar (P/N 109-5000.02), 
and install the plastic strip (P/N 109-5000.07) in accordance with 
the ``Actions'' section, paragraph A5 in Grob SB 817-39, dated 
January 1994.
    (b) For sailplanes not equipped with landing gear legs, P/N 
109B-5001.01/1, within the next 2,000 sailplane landings or 1,000 
hours TIS after the effective date, whichever occurs first, inspect 
the landing gear legs for cracks (using the magnetic particle or X-
ray analysis method) in accordance with the ``Actions'' section, 
paragraph B9 in Grob SB 817-39, dated January 4, 1994.

    Note 2: Landing gear legs (P/N 109B-5001.01/1) have a ``0'' 
stamped on the front side of the leg for easy identification.

    (1) If there are cracks less than or equal to 0.5 mm, prior to 
further flight, polish the existing legs or replace the legs with P/
N 109B-5001.01/1 in accordance with the ``Actions'' section, 
paragraph B10 in Grob SB 817-39, dated January 4, 1994.
    (2) If the polished landing gear legs measures less than 13.0 
mm, prior to further flight, replace the landing gear legs with P/N 
1090B-5001.01/1 in accordance with the ``Actions'' section, 
paragraph B10 in Grob SB 817-39, dated January 4, 1994.
    (3) If no cracks are found, or the cracks are less than 0.5 mm, 
and the thickness of the landing gear legs is equal to or greater 
than 13.0 mm, repetitively inspect the landing gear legs for cracks 
every 1,000 landings or 500 hours TIS, whichever occurs first, in 
accordance with the ``Actions'' section, paragraph B12 in Grob SB 
817-39, dated January 4, 1994.
    (4) If during any of the repetitive inspections, the legs have 
previously been polished and new cracks are found, prior to further 
flight, replace the legs with P/N 109B-5001.01/1 in accordance with 
the ``Actions'' section, paragraph B12 in Grob SB 817-39, dated 
January 4, 1994.
    (c) Replacement of the landing gear legs with P/N 109B-5000.01/1 
terminates the repetitive inspections required by this AD and Grob 
SB 817-39, dated January 4, 1994.
    (d) 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 sailplane to a location where 
the requirements of this AD can be accomplished.
    (e) 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, Small Airplane 
Directorate, 1201 Walnut, suite 900, Kansas City, Missouri 64106. 
The request shall be forwarded through an appropriate FAA 
Maintenance Inspector, who may add comments and then send it to the 
Manager, Small Airplane Directorate.

    Note 3: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Small Airplane Directorate.

    (f) All persons affected by this directive may obtain copies of 
the documents referred to herein upon request to Grob Luft-und 
Raumfahrt, GmbH., D-8939, Mattsies-am Flugplatz, Germany or may 
examine these documents at the FAA, Central Region, Office of the 
Assistant Chief Counsel, Room 1558, 601 E. 12th Street, Kansas City, 
Missouri 64106.

    Issued in Kansas City, Missouri, on February 10, 1997.
Henry A. Armstrong,
Acting Manager, Small Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 97-3961 Filed 2-18-97; 8:45 am]
BILLING CODE 4910-13-U