Most Recent Agent Guidance

This document was drafted by members of the task group to narrow the focus of work further. Their results were made public in September 2000. The group selected CF3I and HFC-125 for continued evaluation. Some remaining technologies do hold promise, however, economically, the gaseous systems still hold advantage.

View Options for Aircraft Engine Fire Protection, September, 2000.

"User Preferred Fire Extinguishing Agents for Engine and Auxiliary Power Compartments"

This document was written to direct the focus of this project regarding which agents ought be evaluated. The published work is a survey which was circulated amongst airline operators, powerplant, and air frame manufacturers to gather their feedback regarding the leading selections for halon replacement in this application. The conclusions resulted in (paraphrasing)...

1. Work with compressible fluids, specifically, FIC-13I1 (CF3I), HFC-227ea (Great Lakes Chemical Corporation FM-200), and HFC-125 (DuPont FE-25), is of primary importance.
2. Material compatibility with engine components must be better known.
3. Gas generator technology is of interest; secondary to compressible fluids.
4. Interest in water mist for this application received minor attention.
5. Operation of these systems will not likely produce human exposure concerns regarding toxicological issues. However, concern during maintenance operations is voiced.

View User Preferred Fire Extinguishing Agents for Engine and Auxiliary Power Compartments, DOT/FAA/AR-96/80.

Minimum Performance Standard for Engine and Auxiliary Power Unit Compartments

The IHRWG formulated a plan to address the issue of finding replacements for Halon 1301 in the engine and APU compartments. The approach conceived is based on the principle of maintaining the current level of safety. The document describes the two facets needed to effect such an evaluation; a simulator and a procedure. The group crafting the document has been involved in this effort since October 1993. The current version was accepted by the group during the July 1996 IHRWG meeting held at the FAA W. J. Hughes Technical Center.

The MPSE describes a test article and a process which may be used to demonstrate the equivalence of an alternate to the current level of safety, as defined by Halon 1301. The process is dependent upon issues relevant to conditions of airflow, agent, and the fire seen in the test section. The primary step is the development of a system capable of delivering Halon 1301 to the test section of the test article which meets the intent of current certification criteria. Upon completing this step, the next process involves repeating fire tests for both Halon 1301 and a replacement candidate to achieve similar fire extinguishment behaviors for a given set of test conditions. The fire extinguishment behavior is marked by the duration a fire is extinguished. The reignition phenomena is accomplished by strategically placing a selection of secondary ignition sources to reignite the fuel/air mixture after the primary extinguishment occurs.

To achieve similar fire extinguishment behaviors between Halon 1301 and the replacement candidate, the quantity of the alternate is iterated until an amount can repeat the performance of the Halon 1301. Upon the replacement candidate achieving comparable performance and it being gaseous, the gas analysis equipment is pulled out and the alternate then quantified. The entire process will be repeated for multiple scenarios representing possible circumstances found in an engine nacelle.

In a broad view the MPSE requires :

1. Fabricating a simulator which must be supplied with :
   • an airflow
   • spray and residual fire scenarios
   • a system to deliver Halon 1301 representative of the current level of safety
   • an ability to deliver a potential replacement to challenge the chosen fire scenario
2. Following the procedure to demonstrate the performance of a replacement by :
   • producing an acceptable Halon 1301 concentration profile within the test article
   • challenging that profile with the two fire scenarios
   • extinguishing the fire scenarios acceptably
   • determining the mass of a replacement agent which reproduces the Halon 1301 extinguishment performance
   • quantifying the replacement agent which did the job adequately

The MPSE no longer reflects requirements to demonstrate equivalence for an alternate in the APU compartment. The discontinuation of the APU effort within the IHRWG reflects the fact that the nacelle criteria was found to far exceed what was actually needed to adequately protect APU compartments as they currently exist. For this reason, protection in this compartment is based on the criteria defined for the nacelle.

The MPSE has been written broadly to allow different technologies potential evaluation in this challenge. Realizing the input from the transport category interests however, the main technology considered will be compressed fluid suppressants.

The MPSE is currently in draft review. A copy can be accessed here.

Additional Information

For information contact:
Doug Ingerson