DOCUMENT TYPE AND REF No TECHNICAL NEWS SHEET CT (MOTH) No 6 Issue 1
 

TITLE: FABRIC COVERING

CLASSIFICATION INFORMATION

This Technical News Sheet is issued for the guidance of Operators when repairing or recovering fabric covered components. Further advice on the method of testing and application may be found with reference to the Civil Aircraft Airworthiness Information and Procedures (CAP 562) Part 2 leaflet 2-8 and 2-9. When carrying out repairs and/or Maintenance of fabric covered aircraft the requirements of Airworthiness Notices (CAP 455) No.20 and 50 must be adhered to.

Fabric Deterioration

Some investigation has been made into the deterioration of fabric on a limited number of samples. It would appear possible for a serviceable life of the order of nine years to be achieved in some cases. However, it will be appreciated that the serviceable life of fabric is greatly affected by a number of variable factors e.g. conditions of storage, hangarage, oil soakage, exposure to sunlight etc.

Fabric Testing

Fabric may be tested by removing suitable test pieces and testing in accordance with B.S. F.100.
Alternatively a portable tester which employs a penetrating cone device, can be used.

Rib Stringing

In the case of early type aircraft single No. 3/18 natural soft flax cord, with a breaking strength of 171b., was specified.

Where single BSF.34.18 linen thread has been used for overhaul stringing it is recommended that a further single stringing is added at the next convenient opportunity but no later than the next major service. This will have the same effect as if doubled BSF.34.18 linen thread is used.

When components are overhauled it is recommended that one of the alternative cords listed in Appendix 1 is used.

Use of Polyester Synthetic Fabric

The use of polyester synthetic fabrics for covering aircraft and components is becoming more widespread due to some difficulty in obtaining the usual linen and cotton fabric. As with all fabric covering, some special expertise is necessary and Operators intending to use these synthetics should pay particular attention to the manufacturers instructions on their use and application. Whilst this Company has no experience of the use of these fabrics, there would appear to be no specific objection to their use providing all appropriate conditions are taken into consideration. In this context, the undermentioned points are emphasized and drawn to the attention of Operators intending to use these fabrics on any of the aircraft mentioned in this News Sheet.

Attachment of the fabric should be in the manner normally employed on that particular aircraft type, but the life expectancy of materials used for stringing stitching and taping should be compatible with that of the covering material.

Tautening of the fabric is by the application of heat and care should be taken to ensure that the makers recommendations are not exceeded or fabric strength can be critically decreased.

Very considerable loads can be applied to the structure if excessive tautening occurs. Particularly in the case of wooden structures, this could be sufficient to cause structural damage. It is therefore essential to exert careful control over the process.

Only non-tautening dopes should be used on these fabrics.

Use of Fibre-glass Fabric

As an alternative to the Polyester Synthetic fabrics mentioned in para 5. fibre-glass fabrics are also available. Whilst this company has no experience of the use of these fabrics, there would appear to be no specific objection to their use providing all appropriate conditions are taken into consideration. It is essential that manufacturers instructions for the use of the fabric are carefully followed.

This Technical News Sheet supersedes and cancels T.N.S. G.A. No.103 Issue 4 dated 28-7-75 which was cancelled due to the discontinuation of the General Series (GA) of T.N.S.'s in May 1990. The contents of the GA series of TNS's have subsequently been re-issued under a T.N.S. number allocated appropriate to aircraft type ie. Moth, Twin, Heron, Dove or Chipmunk.

Whenever a new Technical News Sheet (T.N.S.) is published, or an existing T.N.S. re-issued, operators are advised to hand amend the copy they hold of T.N.S. CT(MOTH) No.l "LIST OF TECHNICAL NEWS SHEETS" to ensure an up to date index is maintained.

NOTE 1:

Details of Fabric Covering and Rib Stringing may be found in the Civil Aviation Airworthiness Information and Procedures (CAIPS) CAP 562 Part 2 Leaflet 2-8.