1 1/212015 LET L13-085a mandatory bU ietin MANDATORY BULLETIN No. L13/985a Concerning: L13, L13A sailplanes Reason: On the L 13 BLANIK sailplane S/N 927226, the t ai lf uselage attachment fitting P/N A 192 921 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 To be accomplished Cost covered by: not later than: December 31, 1999 by: The operator The operator Material availability: Validity: Total number of sheets: ing. Pesak I Manufacturer Upon the approval date 5 Engineering data contained in this Bulletin is CAl Approved
. Date: November 17, 1999 L

ET, a.s . , Kunovice 686 94, Czech Republic L

13/985a Sheet 1 of 5

==== 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 192 921 N as follows: a)Conductivity measurement by means of eddy currents :

- Recommended measurement frequency: 69 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: 

### X lACS: 28.5

- 35.9 MS/m : 15.9

- 29
. 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 m eans of a manual probe. Measuring point: lower milled surface of the component. Measured value : not lower than 199 HB. http: //home

.nwi

.net/- blani kamlball13-085a

.htm 1/711/212015 LET L13-085a mandatory bulletin 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 192 921 N must be replaced before the sailplane operation can be continued. 4. If the attachment fitting P/N A 192 921 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

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 L13/08Sa Attachment fitting P/N A 192 921 N material hardness tested. Measured values: http://home.nwi.net/-blani kam/ba/113-085a

.htm 21711/212015 Sailplane Date: LET L13-085a mandatory bulletin cleared for operation. 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 Sheets 4 and 5: Fig. 1 and Fig. 2

http://home.nwi.net/-blani kam/ba/113-085a

.htm 317111212015 LET L13-0SSa mandatory bulletin 

## L13/085a Fig 1. and 2.

Fig. 1

Ff

g . 2 FuBel age bulkhead N- lc with **chment** fitt ing

**P~** A 1 02 0 21 N SUPPLEMENT;

http: / /home

.nwi.net/-blanikamlball13-085a

.htm fus&l age ):)u

**tl F.**  **·o** <1.

"1-1
. 14

4f711/212015

LEl, a.s. 686 04 Ku n ovlca C;r.e-ch Republlo

OUfl;RII' J**~~** /OT S!OO LET L13-085a mandatory bulletin**f~** lETU. TO

. OtANII< AMERICA**ATT.~ Vll~t~e**  sr rol<y I' M: 00 1 !10!'1 llO.t.SlOG eouNYRY ; WA , u.s.A. PAt' .£S:**~** MltT"Ar.T**l>i;~tON :**  Josof**fl ~J/O'** **i'S** Subj : LET Mandl!ltory Bull eti n L 13IOB5a
Either method is**acc~ptab le:**  A) Conduclivlt y measurement by means ofeddy**curre~lts** , or D) Hardness measuremcut by mean:; nf A portable digital hardneS$ tester.



## Equivalent material For those testing facilities which need to 

### calibrate their measuring instrument by 

### means ofan 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.

http://home.nwi.net/-blani kam/ba/113-085a

.htm 5171 1/212015 LET L13-085a mandatory bulletin 

### 2

) .t ! spd 

## Czech matertgl 

### lur P/ N A 

## 102 011 

## 'f:L Aluminium 

## aloy Z 424253
.62 

## R-**(~pt)** 

### = 407-:- 427 

### M..Pa 

### R.p (0'0 

### .?.)**~** 

### 270 ..;-. 

## 275 :MPa 

## A 

# = 11 _!_ 

## 13% l!quivalent alloy 

### Z 424253
.61**~(apt) ..--**  

### 390**~** 

### 412 MPa**~** 

## (Cfo;)**~** 

## 255 --=:.. 

### 265 :\Ill' 

## a A -= 

## 10% temperature vr,..·.ater 

## mne 490
.... 

### 505 

# oc 20 ...L. 

## 40 

# oc 10 + 

### 15 

## sec . ageing on the 

## atr 5days


## 3) U'S&, egu.tvalcnt**mt;z,t~rtals** 

### aluminium 

### alluy CL
. AD 2024 T 351 

# Rm ( Opl) 

## =- 397 -t- 

### 44 1 M:Pa**~** 

### (Go.:z)**~** 

### 269**~** 

## 290 

## I'vl.Pa

.. !J... 

### =**4~** 

## 12% equiV31ent**<~lloy** 

### C:LAD 2024 T3**Rw(~?t)** 

### _. 400 -:- 434 

### :MPa Rp**(Go.~) ~**  

### 269 .;,. 290 :VIPa



### ... <\.**~tO+lS~i.** 

## heat treatement:

PUBLIC SERVICE: 

### tii!mperature 

### watter 495**~** 

# s(jc up to 

## 3S 

# :Joe

There are many non-destructive testing facilities in North America. Some of 

### them can be accessed at: http://home.nwi.net/-blani kam/ba/113-085a

.htm 61711/212015 LET L13-085a mandatory bulletin • NATIONWIDE http://www.nondestructivetesting.com/nav/aircraft.html 

### • COLORADO. Terry or Robbie at: NDE Services Inc., 8775 East Orchard Road, Greenwood Village, CO 80111, Phone (303) 741-0518. Internet www.ndeseryjces.com
• TENNESSEE. The man in Chattanooga, Tennessee, is Rich Hall. Phone number is 423 899 0043 (W).


### • CALIFORNIA. Gail 

### Flagor, g GE Inspection Services, 1211 K.ona Drive, Rancho Dominguez, Ca. 90220, (310)635-2700 fax:(310)635-1646, Cell phone (310) 505-5648, e-mail: gail.flagor@ps.ge.com .They are in Compton, not a great neighborhood, but you can be in and out in a few hours
.... • CALIFORNIA. Certified Testing and Consulting, 2100 Flight Line Drive #4, Lincoln CA 93648, Phone: 916.434.0195 • MARYLAND. Maryland QC Laboratory, Don Wilson, Tel. (410) 575-7295, Fax (410) 272-5937
• WASIDNGTON. Caliber Inspection, Seattle (at the Boeing Field) Tel. 800-638-3787
• WASIDNGTON. 742 s. Spruce St. Burlington, WA 98233 ph 360 755 9350 • PENNSYLVANIA. Precision Calibration in**Yor~** 

### PA. (717)840-4994. They have eddy current equipment as well as a machine to test the hardness
.....but the second one may be too large for this application. • MONTANA. The headquarters ofMontanaAnvil is 742 s. Spruce St. Burlington, WA 98233 ph 360 755 9350. Their Missoula Mf 

### address is Box 2336 Missoula, Mf 

### 59806. ph406 721 8803 or 406 240 6134. The level III inspector that checked our glider is Brian Moran. The $233 GESC paid for this inspection included a prorated charge for travel from Missoula to Kalispell. Glacier Eagles Soaring Club • COLORADO. Leonard Lantz, Weststar Aviation, Grand Junction 800-255-4193. They can do conductivity test only. • NEW ENGLAND. Tailwind Inspections, Windsor Locks CT. 860-623-8600 will travel all over NewEngland. (one customer paid $125 

### + $50/hr travel)

............ END
........

http://home.nwi.net/-blani kam/ba/113-085a

.htm 717