AIRWORTHINESS DIRECTIVE
For the reasons set out in the background section, the CASA delegate whose signature appears below issues the following Airworthiness Directive (AD) under subregulation 39.1 (1) of CAR 1998. The AD requires that the action set out in the requirement section (being action that the delegate considers necessary to correct the unsafe condition) be taken in relation to the aircraft or aeronautical product mentioned in the applicability section: (a) in the circumstances mentioned in the requirement section; and (b) in accordance with the instructions set out in the requirement section; and (c) at the time mentioned in the compliance section.
Boeing 737 Series Aeroplanes
AD/B737/187 Captain’s Pitot Heater 9/2002
Applicability: Model 737-600, -700, -800, and -900 series aeroplanes listed in Boeing Alert Service Bulletin (ASB) 737-24A1150, dated 11April 2002.
Requirement: 1. Measure the electrical voltage at the circuit breaker for the aircraft captain's pitot heater to determine if the pitot heater is connected to the correct power supply bus, in accordance with ASB 737-24A1150. If the measurement is 100 to 122 volts alternating current (AC), no further action is required by this Directive.
2. If the measurement is not 100 to 122 volts AC, perform all actions associated with connecting the subject circuit breaker wire to the 115-volt AC standby power supply bus (including performing a test to ensure that the pitot heater system operates correctly, repeating the measurement of the electrical voltage at the circuit breaker for the captain's pitot heater, and troubleshooting and correcting the wire connections until the test and measurement are successful), in accordance with ASB 737-24A1150.
Note: FAA AD 2002-14-20 Amdt 39-12820 refers.
Compliance: For Requirement 1 - Within 60 days after the effective date of this Directive.
For Requirement 2 - Before further flight after the Requirement 1 voltage measurement.
This Airworthiness Directive becomes effective on 5 September 2002.
Boeing 737 Series Aeroplanes
AD/B737/187 (continued)
Background: This Directive requires measurement of the electrical voltage at the circuit breaker for the aircraft captain’s pitot heater to determine if the pitot heater is connected to the correct power supply bus and, if necessary, the performance of corrective action.
These actions are necessary to prevent ice from blocking the pitot tube that provides airspeed data to the captain. Such ice blockage could lead to the flight crew receiving incorrect airspeed data, which could result in loss of control of the aeroplane if the flight crew fails to recognize that the data are incorrect.
Eugene Paul Holzapfel
Delegate of the Civil Aviation Safety Authority 29 July 2002
The above AD is notified in the Commonwealth of Australia Gazette on 14 August 2002.
Overview
The Airworthiness Directive (AD) issued by the Civil Aviation Safety Authority (CASA) under subregulation 39.1 (1) of the Civil Aviation Regulations 1998, known as AD/B737/187, was enacted on 5 September 2002. This AD specifically addresses safety concerns related to the Boeing 737 Series Aeroplanes, namely the model 737-600, -700, -800, and -900 series, as outlined in Boeing Alert Service Bulletin (ASB) 737-24A1150 dated 11 April 2002. The primary objective of this directive is to mitigate the risk of ice blocking the pitot tube, which could lead to erroneous airspeed data being transmitted to the flight crew, potentially resulting in loss of control if the crew does not recognise the inaccuracy of the data. CASA mandates that specific electrical voltage measurements and corrective actions be undertaken to ensure the captain's pitot heater is correctly connected to the power supply bus, thereby preventing ice blockage and ensuring flight safety.
Scope and Application
This Airworthiness Directive applies specifically to the Boeing 737 series aeroplanes, namely the 737-600, -700, -800, and -900 models, as detailed in Boeing Alert Service Bulletin 737-24A1150 dated 11 April 2002. It is issued under the authority of the Civil Aviation Safety Authority (CASA) and mandates corrective actions to ensure the safe operation of the aircraft by addressing a potential unsafe condition related to the aircraft captain's pitot heater. The directive requires the measurement of electrical voltage at the circuit breaker for the captain's pitot heater to ascertain if it is correctly connected to the power supply bus, with further actions prescribed if the voltage does not fall within the specified range of 100 to 122 volts AC. Compliance with this directive is mandatory for operators of the affected aircraft models, with a specific timeframe provided for taking the required actions to rectify any identified issues. This legislation is applicable nationally within the Commonwealth of Australia, ensuring uniform safety standards across all jurisdictions.
Key Provisions
The Airworthiness Directive (AD/B737/187) issued under section 39.1(1) of the Civil Aviation Regulations 1998 (CAR 1998) applies to Boeing 737-600, -700, -800, and -900 series aeroplanes listed in Boeing Alert Service Bulletin (ASB) 737-24A1150, dated 11 April 2002. The AD mandates specific actions to ensure the captain's pitot heater is connected to the correct power supply bus to prevent ice from blocking the pitot tube, which could result in inaccurate airspeed readings and potential loss of control. The requirements are detailed in the AD, which include measuring the electrical voltage at the circuit breaker for the pitot heater (Section 1) and performing corrective actions if the voltage is not within the specified range of 100 to 122 volts AC (Section 2). Compliance with these requirements is crucial, with the first action to be completed within 60 days of the AD's effective date, and the second action to be completed before further flight after the voltage measurement.
The obligations imposed by this AD include conducting a voltage measurement at the circuit breaker for the pitot heater to confirm it is connected to the correct power supply bus. If the voltage is within the specified range, no further action is required. However, if the voltage is outside the specified range, operators must follow all necessary steps to connect the circuit breaker wire to the 115-volt AC standby power supply bus, ensuring the pitot heater system operates correctly. These actions are outlined in the Boeing Alert Service Bulletin 737-24A1150 and must be carried out meticulously to avoid any potential safety hazards.
Failure to comply with the AD may result in significant safety risks, as ice blockage of the pitot tube can lead to incorrect airspeed readings, potentially resulting in loss of control of the aeroplane. The AD clearly states that the corrective actions must be taken in accordance with the specified requirements and within the stipulated timeframes. Any non-compliance with the AD could be considered a violation of the Civil Aviation Regulations 1998, potentially leading to enforcement actions by the Civil Aviation Safety Authority (CASA). The specific penalties for non-compliance are not detailed in the AD, but they may include fines, sanctions, or other regulatory measures as prescribed by the relevant aviation authorities.