# Presentation: 143608

## Engine Nacelle Halon Replacement

** **

- International Aircraft Systems Fire Protection Working Group

- Mr. Richard Hill for
- Douglas Ingerson, Engineer
- Federal Aviation Administration
- WJ Hughes Technical Center
- Fire Safety Branch
- Atlantic City Int’l Airport, NJ USA
- tel : 609-485-4945
- email : Douglas.A.Ingerson@faa.gov

- 17April2007

## Presentation Overview

**Review Equivalent Concentrations for HFC-125, CF3I, and FK-5-1-12**
**Alterations/Embellishments to the Minimum Performance Standard for Engine Nacelles and APU Compartments (MPSe)**
- Move away from a Halon 1301 Benchmark
- Considerations for atypical fire extinguishing agents

## Equivalent Concentrations, HFC-125, CF3I, FK-5-1-12

**Based on work completed in the FAA Technical Center’s nacelle fire simulator in accordance with the MPSe**
**Calculated values exceed cup burner data and intermingle with inerting data**

## Equivalent Concentrations, HFC-125, CF3I, FK-5-1-12

## Alterations to the MPSe Move the MPSe off a Halon 1301 Benchmark

**Why ?**
- Halon 1301 supplies diminishing
- continued discharge to atmosphere SPECIFIED for testing purposes
- need to move forward
**How ?**
- specify another fire extinguishing agent as the benchmark
- specify the combustion threats
- other ?

## Alterations to the MPSe Move the MPSe off a Halon 1301 Benchmark

**Specify another fire extinguishing agent as the benchmark**
- HFC-125
- Pro’s
- compares physically to Halon 1301 better than common choices
- established work with this agent already exists within aviation
- widely used outside aviation as a halon replacement candidate
- Con’s
- global warmer
- increased mass required to equate to Halon 1301 performance
- CF3I : no forecasted use by working group members; currently not considered a possibility for this issue

## Alterations to the MPSe Move the MPSe off a Halon 1301 Benchmark

**Specify another fire extinguishing agent as the benchmark (continued)**
- FK-5-1-12
- Pro’s
- not a global warmer
- wide use as a halon replacement being established outside aviation
- Con’s
- physically dissimilar to Halon 1301
- increased mass required to equate to Halon 1301 performance
- lesser work established within aviation
- other suggestion ?

## Alterations to the MPSe Move the MPSe off a Halon 1301 Benchmark

**Specify the combustion threats**
- During early developmental history of the MPSe, task group  opted _NOT_ to do this
- complex test environment; i.e. aerodynamically dependent, flame holding, electrical arcs, hot surfaces, ignition behaviors, fuel/air diffusion behavior, etc.
- observed/measured the fire extinction performance of Halon 1301 and forced a candidate to replicate the established performance
- fire threat intensity affirmed by delivering “half-certification” Halon 1301 and verifying no fire extinction
- negated specifying by heat flux, temperature profile, geometries, fuel flows, etc.

## Alterations to the MPSe Move the MPSe off a Halon 1301 Benchmark

**Specify the combustion threats (continued)**
- HOWEVER, this offers another path to remove the specification of Halon 1301 from the MPSe
- need to specify :
- fuel types, initial fuel temperature, flow rates, fuel spray patterns, etc.
- energy release of the fire threat; i.e. heat flux, temperature
- geometries of the fire threat; i.e. flame holders, hot surface(s)
- ventilated pathway of the structure
- some of this specification already exists in the MPSe
- principle focus for additional thought/work/specification are the fire threats themselves

## Alterations to the MPSe Move the MPSe off a Halon 1301 Benchmark

**Other possibilities to remove the Halon 1301 benchmark ?**

## Alterations to the MPSeConsiderations for atypical replacement candidates

**MPSe is written with sections reserved to allow for atypical replacement candidates**
**These sections are currently unspecified**
**Potential examples :**
- agents delivered as liquid or solid aerosols; i.e. particles
- active or inert gas generators; i.e. gases and particles
- hybrids; clean agents sitting atop an inert gas generator

## Alterations to the MPSeConsiderations for atypical replacement candidates

**Current state of the art for civil aviation is clean, gaseous agents**
**The entire certification process is dependent upon the current state of the art**
**Atypical candidates will require alternate means of measurement to demonstrate acceptable behavior**

## Alterations to the MPSeConsiderations for atypical replacement candidates

**How should atypical agent quantification be handled in the MPSe ?**
- Statham-derivative gas analyzers are written into the MPSe due to common availability and historical stature
- no means to measure aerosols is recognized by the FAA
- no means to measure products from inert gas generators is recognized by the FAA
- two major decomposition products are H2O(g) and N2
- Statham-derivative analyzers :
- can not measure N2 concentration
- have no history of measuring water vapor
- early reports indicate sensitivity to atmospheric humidity
- however, potentially insufficient sensitivity

## Alterations to the MPSeConsiderations for atypical replacement candidates

**How should atypical agent quantification be handled in the MPSe ? (continued)**
- if an applicant pursues an atypical agent pathway :
- they will be required, by default, to develop/prove their own measurement method and equipment
- what is the impact on the MPSe as a result ?
- incorporate new words in the reserved sections about the atypical agent and measurement procedure; in essence, specify agent and applicant in the MPSe
- remove details from the MPSe regarding the Statham-derivative analyzers and their applicability to clean agents
- by doing so, negates the need to specify atypical agent details
- could place ambiguous wording to ensure an adequate measurement process is followed

## Alterations to the MPSeConsiderations for atypical replacement candidates

**Impact on the assessment of the reignition time delay (RTD)**
- RTD = time (fire reignition) – time (fire extinction)
- agent pulse moves through ventilated test fixture
- persistent fuel and ignition sources force reignition after agent pulse degrades sufficiently
- due to the use of clean agents, the RTD is a reasonably visiual determination from video tape; is specified so in the MPSe
- atypical agents may obscure visibility
- change the specification in the MPSe to permit alternate means ?
- should the specification change be “tight”/exact or ambiguous ?

## Alterations to the MPSeConsiderations for atypical replacement candidates

**Impact on the assessment of the reignition time delay (RTD) (continued)**
- historical work indicates the use of a fine-bead thermocouple is inexact as compared to visual indication
- thermal response too slow
- thermocouple bead location is very important
- alternate considerations
- track energy output from the obscured volume surrounding the flame
- obscured cloud temperature should change obviously based on the lack or presence of energy (flames) internal to the cloud
- absorption/reflection/transmission characteristics of the cloud are likely unknowns
- use a Gardon gage style heat flux transducer
- other ?

## Concluding Summary

**Equivalent concentrations**
- HFC-125 = 17.6%v/v
- CF3I = 7.1%v/v
- FK-5-1-12 = 6.1%v/v
**Engine task group members please consider impacts to the MPSe due to :**
- replacing the Halon 1301 benchmark with another reference
- atypical Halon 1301 replacement agents :
- whether or not to specify individual analytical measurement methods
- how to asses the RTD by non-visual means
- comments to be solicited in the “near” future