Aviation safety issues and actions
Interim Recommendation issued to: SAAB Scania As
|Date issued:||18 December 1998|
|Safety action status:|
|Background:||Why this Interim Recommendation was developed|
The Bureau of Air Safety Investigation recommends that Saab
Aircraft AB amend the SAAB 340 Aircraft Operations Manual to more
appropriately alert pilots that the stall warning system may not
activate when the aircraft is operating in icing conditions.
The Bureau of Air Safety Investigation simultaneously issues related interim recommendations IR980269, IR980270, IR980271, IR980272 and IR90274 to Kendell Airlines, Hazelton Airlines, Macair, the Civil Aviation Safety Authority and Saab Aircraft AB respectively.
|Date issued:||18 February 1999|
|Response from:||SAAB Scania As|
|Action status:||Closed - Accepted|
Please find enclosed SAAB Aircraft AB response to your Air Safety Interim Recommendation IR980273. These AOM operation bulletin (one for 340A, 340B) have been released and will be distributed to the operator in the near future.
OPERATIONS BULLETIN NO. 56
Artificial Stall Warning in Icing Conditions
Applicable to all Saab 340 aircraft.
NOTE: With Mod. No. 2650 (ice speed system) installed and selected, the stall warning triggering level is changed to give stall warning at a higher speed.
To highlight the fact that the design of the artificial stall warning system does not always provide a stall warn before stall is encountered if there is ice on the wing-
Even a small amount of ice on the wing will reduce the lifting
capability and increase the stall speed of the aircraft. The
aircraft will stall at a lower angle of attack than for the normal
clean (free of ice) case.
With reference to the above, it is essential that the crew is aware of the adverse effects of ice on the aircraft The operational speeds shall be increased according to AFM (section 5) and AOM (section 2711) if ice is observed on the aircraft or if it is not certain there is no ice on the aircraft. The amount of ice allowed to build up shall be kept at a minimum.