I
considered your approach when building my Lancair IV-P, and elected to go with
two temperature sensors instead. Rationale was that I didn’t know how to
“calibrate” the thermal fuses without testing that was beyond my
capability…and probably interest. Basically I decided to install temperature
sensors near each cowling air exit rather than guess at what value to
use for the thermal fuses. I hooked the temperature sensors to my MVP-50
engine monitoring system and recorded the actual temperatures seen by the two
probes during initial test flying. After determining that the temps never went
above 150F during flight or ground operation, I set the alarm “trigger” temp
for 170F. My normal temperatures run between 120-135F in flight, meaning I
will get a warning if the cowl exit temperature increased by 35-50 degrees
from “normal.” This is an arbitrary setting that has precluded any false
alarm to date…but then again I’ve not yet had a real alarm either. I could
probably generate an earlier warning by lowering the alarm temp, and may do so
the next time I fiddle with the MVP-50 alarm settings. Of course, the
objective is to generate an alarm for any “real” event, but to not generate
false alarms. This took quite a bit of fiddling with most of the settings, but
I am now very comfortable with what I have…and love the system.
Considering
the consequences, I think a fire/overheat monitoring system in the engine
compartment is a very good idea, no matter what system you
use!
Bob
PS:
The actual temperatures will be dependent on the sensor/fuse mounting
location…so don’t use my figures; it’s easy to determine your
own…