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FIREWALLS AND FIRE PROTECTION OF FLIGHT CONTROLSFrom Cp49, Page 5 (July, 1986)
The study of VariEze
accident history has always shown considerably reduced incidents of fire as a result of an
accident than the conventional metal aircraft with the engine on the front. The reasons
for this are relatively obvious in that the sources of ignition of a fire are more remote
to the major impact. Another feature that has been considered safer than the tractor
aircraft is the airflow pattern through the engine area which pulls the fire away from the
aircraft rather than impinging it toward the firewall. There have been no accidents or
incidents in the VariEze or Long-EZ that have been caused by fire destroying aircraft
structure or flight controls. There may be, however, a possibility of this occurring and
this possibility is something that we feel obligated to address and, thus, are
recommending specific modifications to the VariEze, Defiant and Long-EZ to reduce, as much
as possible, the exposure to this risk.
Several years ago, we tested a product called Liquid Firewall and
found it did not provide satisfactory fireproofing/insulation and, thus, did not recommend
its use and, in fact, specifically cautioned those who would attempt substituting it for
the recommended firewall. A couple of weeks ago, Wicks Aircraft sent us a new product
(Ocean 1644 Intumescent) to evaluate. This material is intumescent which means it swells
up to a very thick layer of high temperature insulation and provides surprising results in
that it will protect an aluminum surface from fire damage for a considerable time period.
We do not have the equipment to specifically qualify this material to FAR 23 regulations,
however the torch tests we have conducted have convinced us that it can provide a
considerable barrier to deterioration by fire to aluminum or composite structuew.
The other good news is that this material costs considerably less
than the previous liquid protection product.
Because of our concern that it may be possible to suffer
unacceptable structural damage or loss of flight controls, we are recommending mandatory
changes in this newsletter to all our designs except the Solitaire. This is particularly
important in the VariEze and Long-EZ where both yaw and roll systems pass through the
engine compartment. Loss of roll control on a Defiant may allow recovery using rudder.