Recommendation

The ATSB received the following response from the FAA, dated 9
May 2003.



The FAA has reviewed the incident report and the recommendation and
does not agree that the regulations covering the fire detection
system need to be amended. In the incident, sited by the ATSB, the
detection system indicated a malfunction in the engine compartment
and subsequent action by the flight crew to shut the engine down
was appropriate.



The regulations applicable to fire detection systems result in
robust designs that provide redundant fire loops within the fire
zone and indication logic that is biased such that damage to the
wiring and fire loops will result in indication of a fire. Current
technology fire detection systems do not always have enough
fidelity to differentiate between a duct leak, localized fire,
wiring damage, or an engine case burn through. For example, engine
case burn through can cut wiring and detector loops rapidly before
the fire loop would be activated due to heating. It is imperative
that the engine is shutdown if this failure occurs. The FAA agrees
that it is not desirable to provide misleading information to the
flight crew and in the incident noted in this recommendation the
flight crew discharged both fire bottles into the fire zone when
there was no fire. However, the flight crew actions resulted in
safe shutdown of an engine with a high pressure duct leak.



Amendment of the existing regulations to provide protection of the
fire detector system wiring would likely result in the introduction
of protective heat shields. This feature would not appreciably
improve safety and maintenance errors on the engine could
significantly be impacted by these devices, reducing the overall
level of safety.



After careful consideration of the recommendation, the FAA has
concluded that amendment of the regulations affecting fire detector
systems is not appropriate.