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Output Number
IR19990155
Approval Date
Published Date Time
Recommendation type
Interim recommendation
Mode
Aviation
Date released

The Bureau of Air Safety Investigation recommends that the
Federal Aviation Administration consider the incorporation of an
audible warning to operate in conjunction with the cabin altitude
alert system on Beech aircraft, and other aircraft so
equipped.



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



IR19990150



The Bureau of Air Safety Investigation recommends that Raytheon
Aircraft develop and publish methods for the in-situ testing of the
automatically deployable passenger oxygen activation system and the
cabin altitude alert system on Beechcraft aircraft, to ensure
complete system operation.



IR19990151



The Bureau of Air Safety Investigation recommends that the Civil
Aviation Safety Authority reassess the appropriateness of the
current maintenance procedures for the testing of automatically
deployable passenger oxygen systems and cabin altitude alert
systems, to ensure complete system operation.



IR19990152



The Bureau of Air Safety Investigation recommends that the Federal
Aviation Administration reassess the appropriateness of the current
maintenance procedures for the testing of automatically deployable
passenger oxygen systems and cabin altitude alert systems, to
ensure complete system operation.



IR19990153



The Bureau of Air Safety Investigation recommends that Raytheon
Aircraft consider the incorporation of an audible warning to
operate in conjunction with the cabin altitude alert system on all
Beech aircraft so equipped.



IR19990154



The Bureau of Air Safety Investigation recommends that the Civil
Aviation Safety Authority consider the incorporation of an audible
warning to operate in conjunction with the cabin altitude alert
system on Beech aircraft, and other aircraft so equipped.

Organisation Response
Date Received
Organisation
Federal Aviation Administration (FAA)
Response Text

The Office of Accident Investigation convened a Safety
Recommendation Review Board to review the enclosed responses to
your safety recommendations. As a result, the Review Board
classified your recommendations as follows:



(*IR19990155) 99.401 - "Closed - Acceptable Alternate Action"



This is in response to Safety Recommendation[s] 99.401, which
pertain[s] to passenger oxygen systems and cabin altitude alert
systems on Raytheon Model 200 Series aircraft. Safety
Recommendation 99.401 requested incorporation of an audible warning
to operate in conjunction with the cabin altitude alert system on
these aircraft and other aircraft similarly equipped.



Safety Recommendation 99.401, which requests consideration of an
audible warning to operate in conjunction with the existing visual
warning system, has also been reviewed. The existing system
utilizes a red "ALT WARNING" annunciator light. Although no aural
tone is present when the red light illuminates, both master warning
flashers begin flashing to bring the pilot's attention to the
appropriate annunciator. In reviewing this recommendation, the
certification basis for the Raytheon Model 200 Series airplanes was
reviewed. At the amendment level established in the certification
basis, Section 23.841 (f) states: "...an aural or visual signal (in
addition to cabin altitude indicating means) meets the warning
requirement for absolute cabin pressure limits". Furthermore, the
corresponding Part 25 (Transport Category) requirement (Section
25.841(b)(6)) states: "...an aural or visual signal (in addition to
cabin altitude indicating means) meets the warning requirements for
cabin pressure altitude limits ... ). Based on the above, the FAA
has clearly never specifically required an aural cabin altitude
warning. Although it is recognized that adding an aural warning is
a desirable enhancement of the system, requiring such a warning for
the existing fleet is not considered necessary to meet the minimum
airworthiness standards.



In conclusion, this office considers the actions identified in this
letter to be satisfactory in addressing the safety concern. The
existing visual warning system for high cabin altitude is deemed
acceptable.



Therefore, the Wichita ACO recommends that Safety Recommendation[s]
95.401 be closed.