Firewalls and Fire Protection of Flight Controls

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.

Copyright 1999-2017 All Rights Reserved