AD 75-16-14 ACTIVE

75-16-14 BRITISH AIRCRAFT CORPORATION: Amendment 39-2289. Applies to Model BAC 1-11, 200 and 400 Series airplanes.

Compliance is required within the next 500 hours' time in service after the effective date of this AD, unless already accomplished.

To prevent possible static inverter failure which could result in the loss of the A.C. emergency power supply to essential flight instruments, accomplish the following:

(a) For airplanes which have not had BAC Modification 4535 incorporated, either -

(1) Replace the installed Rotax static inverter, P/N U6705, with a serviceable Rotax static inverter, P/N U6705/1; or

(2) Modify the installed Rotax static inverter, P/N U6705, in accordance with paragraph (c).

(b) For airplanes which have had BAC Modification 4535 incorporated, either -

(1) Replace the installed Rotax static inverter, P/N U6724, with a serviceable Rotax static inverter, P/N U6724/1; or

(2) Modify the installed Rotax static inverter, P/N U6724, in accordance with paragraph (c).

(c) Rotax static inverters, P/N U6705, may be converted to Rotax static inverters, P/N U6705/1, and Rotax static inverters, P/N U6724, may be converted to Rotax static inverters, P/N U6724/1, for compliance with paragraph (a)(2) or (b)(2) by -

(1) Changing the R6 and R7 resistors on Printed Circuit Board No. 1 from 220 ohms/1.5 watt to 82 ohms/0.25 watt or 0.5 watt; and

(2) Satisfying the functional tests for the modified static inverters as specified in Rotax Service Bulletin No. 24-420 at Revision 1, dated August 20, 1971 (Rotax Modification No. 4743 U) or an FAA-approved equivalent.

(British Aircraft Corporation, Model BAC 1-11 Service Bulletin No. 24-PM 4992, Revision 1, dated November 8, 1971, refers to this same subject).

This amendment becomes effective August 28, 1975.