Grounded Without Cause

Sept. 26, 2006
The FAA and extinguishing agent containers

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.

This type of disconnect is exactly what causes the industry to lose faith in the knowledge level of the FAA inspectors. This particular inspector told the operator not to operate the Citation II under Part 135 any longer until an exemption could be obtained or an STC incorporated that would install the disk-type indication system. It seems that if the inspector had a little common sense he would have thought to consider the number of Citation II’s currently being operated under Part 135. Not to mention the numerous other aircraft that do not use the green disk/red disk indication system. Falcon 20’s, Falcon 900, Falcon 2000, Gulfstream GIII and GIV and Bombardier Challenger aircraft just to mention a few and hundreds of which are currently operating under Part 135. Inspectors are required to ensure that those who they oversee meet the intent of the regulation. As many of you know, the regulation is a means of ensuring that federal law is not broken.

Letter of Compliance

Another point to ponder is this. The process of certification for operations under Part 135 requires an operator to provide a “Letter of Compliance” that explains in detail how each regulation will be complied with by the operations. The problem is, most safety inspectors use the letter of compliance merely during certification and do not go back to look at it before going off the handle when they run across something they question. In this case I am sure that the operator described how a Citation II aircraft meets the requirements of Part 121.267. It’s actually quite simple. Part 135 refers to Part 121 for additional airworthiness requirements rather than having its own. When the subject portion of Part 121 was written, the author had no reason to believe that the smaller “Large” aircraft would be used for flight under Part 135 and would be referred to this section of Part 121.

Convenient for inspection

Lets look at Part 121.267 above again. Now, look at the sentence in question. “The discharge line from the relief connection must terminate outside the airplane in a place convenient for inspection.” The key here is convenient for inspection. The multiple business aviation large aircraft that don’t have discharge disks don’t because the purpose of the disks is to identify, during pre-flight inspection, that the engine fire extinguishers are fully charged and capable of extinguishing an engine fire in the case one should erupt during the flight. (as required by Part 25.1199 above.) For those aircraft that do not have discharge disks, access to the actual gauge (a much more accurate means of checking the pressure) is readily available in a place convenient for inspection, the hell hole which is accessible in most cases by just opening the hatch.

Literal mis-interpretation

Look at the entire paragraph including the title. This regulation is not at all limited to engine fire extinguishers. If taken literally, this means that all handheld fire extinguishers would be required to meet this rule and that is completely ridiculous. Literal interpretation would mean that all large aircraft operating under Part 135 required to have hand-held fire extinguishers (which is all aircraft) are operating contrary to the regulation and should be grounded immediately with an emergency AD. Ridiculous isn’t it. Well, the FAA is not going to issue an emergency AD to ground all of the aircraft, but neither should this rogue inspector be able to unnecessarily halt business for this operator.

I wish I could put my finger on what it is that creates a situation like this. We as industry are subject to, and in some cases victim to, the ignorance of our assigned FAA safety inspector. I can appreciate the fact that all safety inspectors are different and that they all have different levels of experience. And I can appreciate also that there can be misunderstandings between us and our safety inspectors. But I believe that being a federal agency, our FAA is called to rise above this sort of mediocrity. How much more effort would it have taken for him to ask himself, “How many Citation II’s are operating under Part 135?”, or “How many Citation II aircraft have been modified to meet the literal interpretation of this regulation?” or even more enlightening “How many other aircraft are operating under Part 135 that were not manufactured with blow out disk systems and have not been modified? The answer to the latter is hundreds.

It is very frustrating when there is no consideration for the cost of lost operation for those who fall subject to these situations. The only recourse we have at this point is the Customer Service Initiative (CSI) program put in place about two years ago. Many do not know about it but the program allows for industry to push what we feel are inappropriate interpretations or just lousy service to the next level. You can read more about the CSI program in the April 2006 issue available online at

Until next time.

About the Author

Joe Hertzler