MANDATORY BULLETIN
No. L13/085a
Concerning: L13, L13A sailplanes
Reason: On the L 13 BLANIK sailplane S/N 027226, the tail-
fuselage attachment fitting P/N A 102 021 N made of
424253.11 material has been damaged in service.
The material of this component must be tested as
instructed in this Bulletin.
To be accomplished not later than: December 31, 1999
To be accomplished by: The operator
Cost covered by: The operator
Material availability: ----
Validity: Upon the approval date
Total number of sheets: 5
ing. Pesak / Manufacturer
Engineering data contained in this Bulletin is CAI Approved.
Date: November 17, 1999
LET, a.s., Kunovice 686 04, Czech Republic
L13/085a Sheet 1 of 5
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A. WORK PROCEDURE
1. Remove the oval cover located on the LH side of the fuselage,
under the horizontal stabilizer.
2.Test the material of the attachment fitting P/N A 102 021 N as
follows:
a)Conductivity measurement by means of eddy currents:
- Recommended measurement frequency: 60 kHz
- Probe diameter: not exceeding 15 mm
- Measuring contact point: lower milled surface of the component,
between the rivets (see, Figs. 1 and 2).
Permissible range of measured values:
% IACS: 28.5 - 35.0
MS/m: 15.0 - 20.
Note: The surface protective coating of the component need
not be removed.
b) Hardness measurement by means of a portable digital hardness
tester. Measuring method: depending on the type of the hardness
tester used, i.e. dynamic, ultrasonic, and/or by means of a
manual probe.
Measuring point: lower milled surface of the component.
Measured value: not lower than 100 HB.
c) Any other measuring method must be approved by the sailplane
manufacturer before it can be used.
3.1 If the values measured during the check are within the
permissible limits specified above, make a record in the
sailplane logbook (see section H of this Bulletin). The
sailplane operation can be continued without any limitations.
3.2 If the values measured during the check are not within the
permissible limits, the attachment fitting P/N A 102 021 N must
be replaced before the sailplane operation can be continued.
4. If the attachment fitting P/N A 102 021 N is to be replaced,
the operator shall place an order with the manufacturer, stating
the sailplane Serial No., number of flight hours, registration
mark, and number of its repairs and/or overhauls.
5. The manufacturer will send to the operator the material
required for replacement, together with a bulletin providing the
work procedure.
6. After the check, reinstall the inspection hole cover.
L13/085a Sheet 2 of 5
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D. MATERIAL REQUIRED FOR MODIFICATION OF ONE SAILPLANE
None.
C. ILLUSTRATIONS
Figs 1 and 2.
D. DOCUMENTATION REQUIRED
None.
E. TOOLS REQUIRED
Material hardness testing equipment:
- Eddy current conductivity meter
- Hardness tester
F. SPARE PARTS IN OPERATION
The spare parts in stock, if any, must be tested as
instructed in Section A, item 2 of this Bulletin.
G. SAILPLANE MASS
Not affected.
H. RECORD IN LOGBOOK AFTER BULLETIN IMPLEMENTATION L13/085a
Attachment fitting P/N A 102 021 N material hardness
tested.
Measured values:
Sailplane cleared for operation.
Date: Carried out by:
(legible signature of
authorized engineer)
I. ACCOMPANYING DOCUMENTATION
Not affected.
Contact Address:
LET, a.s.
Product Support Dept. 686 04 Kunovice 1177
Czech Republic
tel 0632/55 44 96; fax 0632/56 41 13
E-mail: ots@let.cz
L13/085a Sheet 3 of 5
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Sheets 4 and 5:
Fig. 1 and Fig. 2
SUPPLEMENT:
For those testing facilities which need to calibrate their measuring instrument by means of an equivalent U.S. material, below is the table provided by LET a.s. For clarity, the equivalent U.S. material is either CLAD 2024 T 351, or CLAD 2024 T3.
PUBLIC SERVICE:
There are many non-destructive testing facilities in North America.
Some of them can be accessed at:
NATIONWIDE http://www.nondestructivetesting.com/nav/aircraft.html
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