a. This British Standard specifies requirements for 'Tersil'* type cables for aircraft wiring of circuits in which the potential between conductors, or between a conductor and metal braid or the aircraft structure, does not exceed 600 volts (r.m.s.) and the frequency does not exceed 1600 c/s and where any combination of ambient temperature and conductor current for continuous service does not produce a stabilized conductor temperature in excess of 190℃. The cables are suitable for fixed wiring in aircraft at temperatures down to -75℃, but are not suitable for severe flexing at temperatures below -55℃. The cables do not support combustion and comply with the require-ments of British Standard 2G. 100 in respect of fire resistance.
b. The generic name 'Tersil' is applicable only to cables covered by this British Standard and complying with all its requirements.
c. The standard includes the following ranges of cables:
(i) Tersil. Cable with a copper conductor and composite insulation of silicone rubber, glass and polyethylene terephthalate or other suitable materials.
(ii) Tersilal. Similar to the Tersil range but with a conductor of aluminium instead of copper.
* The various combinations of the word 'Tersil' used to distinguish these cables were originated by the Royal Aircraft Establishment of the Ministry of Aviation.
(iii) Tersilmet. Similar to the Tersil range but with the addition of a metal braid.
(iv) Tersilmetsheath. Similar to the Tersilmet range but with the addition of an external sheath of insulating materials.
(v) Dutersil, Tritersil, Dutersilal andTritersilal. Two-or three-core cables consisting of two or three Tersil or Tersilal cables twisted together.
d. The cables are classified and identified, not by current ratings, but by a series of numbers indicative of the conductor cross-sectional area. These numbers correspond to those used for equivalent American cables. The maximum current ratings for Tersil cables are quoted in Appendix A.