Recommendation

This recommendation placed in MONITOR status after receipt of the following initial response from the FAA on 30 July 2002. :

The Office of Accident Investigation is in receipt of your recommendations regarding "Cabin Barometric Pressure Switches."

Your recommendations have been forwarded to the appropriate office for response, which is normally 90 days. Your recommendations have been identified, as 02.216 and 02.217 inquiries should reference these numbers.

You will be kept informed as to the progress and final resolution of your submission.

Final Response to FAA Safety Date: December 18, 2002

Recommendations 02.216 and 02.217

Safety Recommendations 02.216 and 02.217: Safety Recommendations (SR) 02.216 and 02.217 were raised as a result of an inquiry by the Australian Transport Safety Bureau (ATSB). These recommendations concern the Cessna Model 441 aircraft, and request the FAA review the adequacy of the maintenance requirements for the barometric pressure switches utilized in the cabin altitude alerting system and the oxygen mask auto-deploy system. FAA SR 02.216 is written with regard to the cabin altitude barometric pressure switch and SR 02.217 concerns the oxygen auto-deploy barometric pressure switch. The ATSB recommendation numbers for these items are R20020103 and 20020104, respectively.

These actions were presented in response to an incident that occurred on January 31, 2002 in which a Cessna Model 441 had to initiate an emergency descent as the result of a loss in cabin pressure. It was noted during this incident that the cabin oxygen mask did not auto-deploy as expected. The aircraft landed without incident.

Subsequent maintenance actions discovered a faulty barometric pressure switch in the oxygen auto-deploy system. As a precaution the barometric pressure switch which triggers the cabin altitude warning was also checked. As a result of these maintenance actions it was discovered that there were no published maintenance procedures to adjust and/or test either barometric pressure switch after maintenance action.

Wichita ACO Position:

The ACO interim response of September 25, 2002 stated that maintenance procedure did exist for the cabin altitude warning barometric pressure switch. It also highlighted the omission of similar maintenance procedures for the oxygen mask auto-deploy barometric pressure switch. In the interim response it was noted that Cessna would develop and incorporate maintenance procedures for this switch in the Maintenance Manual. Additionally, two items remained unresolved at the time of the interim response. These items were as follows:

a. Cessna to supply the ACO a date for MM incorporation of a functional test
procedure of the oxygen auto-deploy barometric pressure switch.

b. Cessna to incorporate a required check interval for the barometric pressure switches. This should be required, as the failure of these switches is latent. The ACO and Cessna are currently addressing this issue.

Cessna has provided the following response to both these items:

a. The MM will be updated at the next scheduled revision in July 2003.

b. Cessna has agreed to a required periodic inspection incorporated into the phase 5, interval D inspection in chapter 5 of the MM. This inspection coincides with functional tests of the oxygen and pressurization systems. This office is working with Cessna to define the nature of these inspections.

The ACO has reviewed Cessna's proposal and accepts this position. Based on the fact that procedures exist or will be developed and periodic inspection intervals will be  implemented in the MM. This office respectfully requests that this safety recommendation be closed.