Grounded Without Cause

Again an issue has arisen that demonstrates how far away we really are from having a level playing field between FAA field offices. There have been several such issues in the past but with the advent of the Customer Service Initiative (CSI) we thought we had made enough progress to have confidence that this sort of issue would not develop. The issue has to do with engine fire extinguishers and the ability to see, prior to takeoff, if the engine fire extinguisher(s) has been discharged, ensuring the availability of the extinguisher for the flight, if needed.

Many of the large aircraft manufacturers have used colored disks displayed in the skin of the aircraft to display the state of charge of the engine fire extinguishers. However, many other manufacturers have used pressure gauges or other indicators on the bottles themselves when the bottles are easily accessible for inspection prior to takeoff, clearly meeting the requirements of Part 25. See below.

Sec. 25.1199 Extinguishing agent containers

(a) Each extinguishing agent container must have a pressure relief to prevent bursting of the container by excessive internal pressures.

(b) The discharge end of each discharge line from a pressure relief connection must be located so that discharge of the fire extinguishing agent would not damage the airplane. The line must also be located or protected to prevent clogging caused by ice or other foreign matter.

(c) There must be a means for each fire extinguishing agent container to indicate that the container has discharged or that the charging pressure is below the established minimum necessary for proper functioning.

(d) The temperature of each container must be maintained, under intended operating conditions, to prevent the pressure in the container from (1) Falling below that necessary to provide an adequate rate of discharge; or (2) Rising high enough to cause premature discharge.

(e) If a pyrotechnic capsule is used to discharge the extinguishing agent, each container must be installed so that the temperature conditions will not cause hazardous deterioration of the pyrotechnic capsule.

The problem came up when an operator was receiving a periodic certificate inspection by the local FSDO inspector. Although I don’t know for sure, I suspect that this inspector was new to the operator and had recently been reassigned from mainly heavy air carrier operations under CFR Part 121. Following a physical inspection of a Citation II, the inspector wrote a letter to the operator stating that operation of the Citation II under CFR Part 135 “may” be contrary to the Federal Aviation Regulations. The basis of the allegations is the fact that the aircraft does not have discharge tubes that terminate at the aircraft fuselage in order to indicate that the fire extinguisher container has been discharged. The applicable regulation is CFR Part 135.169(a) which refers to CFR Part 121.267 which states:

Sec. 121.267 Extinguishing agent container pressure relief

Extinguishing agent containers must be provided with a pressure relief to prevent bursting of the container because of excessive internal pressures. The discharge line from the relief connection must terminate outside the airplane in a place convenient for inspection on the ground. An indicator must be provided at the discharge end of the line to provide a visual indication when the container has discharged.

To us it is very obvious that when the aircraft conforms to Part 25, the basis of its type certification, it clearly meets the intent of Part 121.267 which, by the way, appears to have not been revised since April 4, 1965.