Page:CAB Accident Report, United Air Lines Flight 823.pdf/32

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Mr. George S. Moore Director Flight Standards Service Federal Aviation Agency Washington, D. C. 20553

Dear Mr. Moore:

During the course of our continuing investigation of the accident involving a United Air Lines Vickers Viscount aircraft near Parrottsville, Tennessee, on July 9, 1964, at was revealed, during static and flight tests, that certain discrepancies existed in the Pyrene fire extinguisher. The most serious of these discrepancies was the spraying of CO2 into the cockpit area when extinguishers are discharged. This was determined to have been due to leakage at either the bayonet floor fitting or at the valve in the head of the discharge bottle.

This discrepancy was previously brought to your attention in our correspondence of October 9, 1964, wherein we recommended that the Administrator evaluate the design of the Pyrene Duo Head Model DCD-10 fire extinguisher system. Your letter of October 19, 1964, indicated that our recommendation was being studied.

We believe that during the period required for your study the potential hazards outlined in our previous recommendation continue to exist. Therefore, it is further recommended that all operators of Viscount aircraft having a Pyrene cylinder installation within the general cockpit area, be requested to re-emphasize the need for pilots to don smoke masks before discharging the lower cargo bin CO2 cylinder.

In addition the operators should be informed that a CO2 spray directed into the cockpit area could result in considerable distraction if the pilots are unaware that such an incident could occur.