Commonwealth legislation

AD/B737/128 - Forward Lavatory Drain - Isolation Valve

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legislative instrument

Plain English Summary

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This Airworthiness Directive applies to Boeing 737‑100/200/300/400/500 aeroplanes fitted with forward lavatories. It requires operators to place a warning placard by the forward lavatory sink to prevent selecting the drain position in flight, and later to fit an isolation valve in the forward-lavatory drain line.

Operators must install the placard within six months and the isolation valve within 36 months; the valve method must be approved by Boeing or under Regulation 35. Operators bear the compliance cost; approvals and maintenance scheduling are the decision and implementation points.

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AD/B737/128 - Forward Lavatory Drain - Isolation Valve

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

SCHEDULE OF AIRWORTHINESS DIRECTIVES

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Boeing 737 Series Aeroplanes

AD/B737/128 Forward Lavatory Drain - Isolation Valve 5/99

Applicability: All Boeing model 737-100, -200, -300, -400, and -500 series aeroplanes having forward lavatories installed.

Requirements: 1. Install a placard on the door beneath the forward lavatory sink, that warns the cabin crew not to put the selector valve for the forward lavatory water supply in the “DRAIN” position during flight. This installation is to be completed in accordance with the provisions of Boeing Service Bulletin 737-38-1043 dated 8 January 1998.

Install an isolation valve in the drain line downstream of the selector valve for the forward lavatory water supply, in accordance with a method approved by the aircraft manufacturer or is approved under Regulation 35. Once this is accomplished, the placard at requirement 1 above may be removed.

Note: US FAA AD 99-01-16 Amendment 39-10981 refers.

Compliance: 1. Within six months of the effective date of this Directive.

Within 36 months of the effective date of this Directive.

This Airworthiness Directive becomes effective on 20 May 1999.

Background: Reports of damage to the horizontal stabiliser and engine flame out caused by ice formed from water drained inadvertently from the forward toilet through a mispositioned selector valve. This Directive introduces measures to warn of mispositioning the valve and, eventually, modifying the system to eliminate such occurrences.

Source text

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

1 AD/B737/128 - Forward Lavatory Drain - Isolation Valve