Commonwealth legislation

AD/SWSA226/57 Amdt 1 - Battery Bus Relay

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legislative instrument

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This airworthiness directive requires operators of specified Fairchild (Swearingen) SA226/SA227 aeroplanes to remove a diode from the battery bus relay K40, reinstall the J‑box access cover, and verify battery voltage on the left and right essential and non‑essential buses. CASA set compliance within 100 flight hours from 17 May 1990.

CASA and Fairchild state a shorted diode can de‑energise the relay and prevent re‑energisation, risking unrecoverable electrical loss. Amendment 1 only corrects the serial‑number applicability; the required modification is unchanged.

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AD/SWSA226/57 Amdt 1 - Battery Bus Relay

COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY

SCHEDULE OF AIRWORTHINESS DIRECTIVES

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Fairchild (Swearingen) SA226 and SA227 Series Aeroplanes

AD/SWSA226/57

Amdt 1

Battery Bus Relay 10/90

Applicability: All model SA226-T S/N T201 through T275 and T277 through T291; SA226-T(B) S/No T(B) 276, and T(B) 292 throught T(B) 417; SA226-AT S/No AT 001 thorught AT 074; SA226-TC S/No TC 201 through TC 419; SA227TT S/No TT 421 through TT 541; SA227-AT S/No AT 423 through AT 695; SA227-AC S/No AC 406, AC

415, AC 416, AC 420 through AC 705, and AC 707 through AC 733.

Requirement: Modify the battery bus relay electrical system as follows:

Remove the access cover from the ‘J-box’, EP 11;

2. Remove the diode from terminals X1 and X2 of the battery bus relay K40;

3. Reinstall access cover; and

4. Using the battery switches, varify that battery voltage is present on the LH essential, RH essential and non essential busses.

Note: Fairchild SB’s SA226-24-032, SA227-24-013 and FAA AD 90-03-19 R1 also

refer.

Compliance: Prior to exceeding 100 hours time in service from 17 May 1990.

Background: Fairchild and the FAA have determined that a short circuited battery relay diode will cause de-energization of the battery relay and prevent any subsequent re-energization of the battery relay. This in combination with the loss or interruption of electrical power could result in an un-recoverable loss of electrical power to the aircraft. Tests by Fairchild indicate that removal of the battery relay diode as required by this AD did not impose any high voltage spike problems on the DC system.

Amendment 1 to this AD is issued to correct the applicable S/No range only. - No additional work is required.

Source text

Sourced from the Federal Register of Legislation (legislation.gov.au), CC BY 4.0.

1 AD/SWSA226/57 Amdt 1 - Battery Bus Relay