Jump to Content

Interim Recommendation issued to: Civil Aviation Safety Authority

Recommendation details
Output No: IR19990076
Date issued: 03 June 1999
Safety action status:
Background: Why this Interim Recommendation was developed

Output text

The Bureau of Air Safety Investigation recommends that the Civil Aviation Safety Authority examine the circumstances surrounding this occurrence and take whatever steps it considers necessary to ensure the safety of the Saab 340 fleet operating within Australia.

As a result of the investigation into this occurrence, the Bureau simultaneously issues the following interim recommendations:

IR990072

The Bureau of Air Safety Investigation recommends that Saab Aircraft AB fit the ice-speed modification of the stall warning system to the worldwide fleet of Saab 340 aircraft, as a matter of priority.

IR990073

The Bureau of Air Safety Investigation recommends that the Federal Aviation Administration note the circumstances surrounding this occurrence, and note the fact that the Bureau shares a number of concerns regarding aircraft certification procedures, particularly those involving flight in known icing conditions.

IR990074

The Bureau of Air Safety Investigation recommends that the Joint Airworthiness Authorities note the circumstances surrounding this occurrence, and note the fact that the Bureau shares a number of concerns regarding aircraft certification procedures, particularly those involving flight in known icing conditions.

IR990075

The Bureau of Air Safety Investigation recommends that Luftfartsverket note the circumstances surrounding this occurrence, and note the fact that the Bureau shares a number of concerns regarding aircraft certification procedures, particularly those involving flight in known icing conditions. The Bureau also recommends that Luftfartsverket as the initial certifying agency of the Saab 340 aircraft, review the certification aspects of the aircraft's stall warning system, particularly in icing conditions.

Initial response
Date issued: 13 August 1999
Response from: Civil Aviation Safety Authority
Action status: Closed - Not Accepted
Response text:

BASI Interim Recommendation IR990076, resulting from occurrence 9805068, recommends that CASA examine the circumstances surrounding the stall of a SAAB 340 aircraft at Eildon Weir on 11th November 1998, and take whatever steps are necessary to ensure the safety of SAAB 340 aircraft operating in Australia.

The occurrence report noted that the crew had selected engine and propeller anti-ice systems on, but had not activated the leading edge de-icing boots. The auto pilot was engaged, and the aircraft slowed under the icing conditions until stall occurred. Airframe buffet was experienced, but the crew mistook this buffet for propeller vibration.

The report favourably notes modifications mandated by Transport Canada. The report is thorough in evaluating the history of de-icing problems in SAAB 340 and similar aircraft. However, actions by the crew in this instance appear to have made a poor situation worse. CASA therefore does not believe at this time that there is an airworthiness problem with this aircraft type that requires immediate mandatory action.

Also, you will be aware of the intense debate a decade ago on the subject of Australian-specific design requirements for aircraft. The debate resulted in Australia's design requirements in Part 101 of the Civil Aviation Orders being abandoned for aircraft types that have civil certification in a major aviation country. The public policy of CASA and the Government is now that CASA will impose requirements additional to those of internationally accepted certification standards only where those requirements can be publicly justified, including cost-benefit considerations. The SAAB 340 and many other similar aeroplanes have been type certificated to internationally accepted certification standards and the argument for imposing the Canadian requirement on these aeroplanes, or even the SAAB 340 in isolation, does not yet appear to be adequate to meet CASA's criteria for an Australian-specific design requirement.

Subsequent to the issue of this report, the US FAA has proposed some major changes to the way that modern propeller aircraft are handled under icing conditions. This includes a proposal to require that de-icing boots be activated as soon as an aircraft encounters icing conditions (FAA research has shown that "ice-bridging" is not of concern with modern de-icing systems). There is likely to be considerable discussion of these issues over the coming months, and CASA will be keeping a close watch on developments.

Pending the outcome of the FAA proposal, CASA will

- write to Australian operators of this aircraft type to inform them of the BASI investigation, and recommend they review their training and operating procedures; and

- write to the manufacturer and associated regulatory authorities to seek their views, and to elicit comments on appropriate action.

We will provide you with information copies of this correspondence, and keep you informed of any further action initiated.

 
Share this page Comment
Last update 01 April 2011