Jump to Content

Recommendation issued to: Civil Aviation Safety Authority

Recommendation details
Output No: R20040058
Date issued: 12 May 2004
Safety action status:
Background:

SADN DESCRIPTION

Several Australian registered Cessna 208 aircraft are operating under Australian Civil Aviation Safety Authority Approved Single Engine Turbine Powered Aeroplane (ASETPA) authorisation without an aircraft manufacturer approved safety enhancement. The safety enhancement requires the aircraft Emergency Power Lever (EPL) to have copper witness wire installed to prevent inadvertent activation during normal operations, and to indicate movement of the lever during emergency use. Inadvertent activation of the EPL during normal operations could cause engine surging, exceeding inter-turbine temperatures, gas generator speeds and torque limits, leading to engine damage.


Background

The EPL, which is connected through linkages to the manual override lever on the fuel control unit, governs the fuel supply to the engine should a pneumatic malfunction occur in the unit. The EPL permits the pilot to restore engine power by activating the lever to manually introduce fuel to the engine.

The aircraft manufacturers Service Kit, SK208-142, provides for the installation of mechanical devices allowing for the installation of copper witness wire to the EPL. If the EPL has been moved from the NORMAL position, the copper witness wire will fracture and provide a physical indication that it has been activated. The installation of Service Kit SK208-142 is not mandatory for Australian registered aircraft.

Cessna Alert Bulletin, CAB01-15, includes a requirement to ensure the fitment of the copper witness wire to the EPL of all aircraft that have had Service Kit SK208-142 installed. Some Australian operators have had Service Kit SK208-142 installed in their aircraft, but are not complying with the Cessna Alert Bulletin CABO1-15 as it is not mandatory for Australian registered aircraft. Compliance with the requirements of the bulletin was also not mandated by the US Federal Aviation Administration.

The aircraft maintenance manual states that if the EPL witness wire was broken or missing then a determination was to be made, as required by the engine maintenance manual, to ascertain if the engine limitations had been exceeded.

The aircraft pilots operating handbook includes a caution that states:

'The emergency power lever and its associated manual override system is considered to be an emergency system and should be used only in the event of a fuel control unit malfunction. When attempting a normal start the pilot must ensure that the emergency power lever is in the NORMAL (full aft) position; otherwise, an overtemperature condition may result.

'When using the fuel control manual override system, engine response may be more rapid than when using the power lever. Additional care is required during engine acceleration to avoid exceeding the engine limitations.

'Inappropriate use of the emergency power lever may adversely affect engine operation and durability. Use of the emergency power lever during normal operation of the power lever may result in engine surges, or exceeding the ITT, Ng, and torque limits.'

Inadvertent movement of the EPL during normal operations could result in engine damage. Compliance with the requirements of CABO1-15 would mitigate the risk of such an inadvertent movement and would ensure that appropriate maintenance actions were taken as required by the engine manufacturer.

Output text

Safety Recommendation

The Australian Transport Safety Bureau recommends that the Civil Aviation Safety Authority assess the safety benefit of mandating Cessna Alert Bulletin CAB01-15 with regard to the Emergency Power Lever on all Approved Single Engine Turbine Powered Aeroplane Australian registered C208 aircraft.

Initial response
Date issued: 14 July 2004
Response from: Civil Aviation Safety Authority
Action status: Monitor
Response text:

CASA has assessed the safety benefit of mandating Cessna Alert Bulletin CAB01-15 and has agreed to issue an Airworthiness Directive (AD), which will mandate the Cessna Bulletin.

Further correspondence
Date issued: 26 May 2005
Response from: Civil Aviation Safety Authority
Response status: Closed - Accepted
Response text:

The Civil Aviation Safety Authority issued Airworthiness Directive AD/CESSNA 208/18 Emergency Power Lever Shear Wire on 26 May 2005.

 
Share this page Comment
Last update 01 April 2011