Got Heat coming into the cabin in the blazing
summer time? Not Enough heat in the winter time? Well, here are some thoughts on
the heater box from Beechcraft owners that may help you get a
better handle on your system and how you might
go about solving some of your issues.
Here are some thoughts from Bob K. on his B35
Bonanza heater box set up:
Here I don't know if there are any differences between the B
and other Bonanza heater set-ups but one thing I found in mine was a cable for
emergency heat cutoff in the circuit breaker panel on the right hand side. The
original setup on this plane had the battery box on the back side of the panel
with an access to the engine side. Mine had let battery acid leak through the
box and ate through the cable windings for the emergency shut off used to reduce
smoke in the cabin in the event of a fire. You could pull that knob all the way
out and it had absolutely no effect on shutting off the heat access.
When I replaced my panel, the heater controls were moved to
the opposite side of the panel and the cables replaced. On mine there are
actually two mechanisms that can affect heat entry. The first being the heater
lever that controls flow of air past the exhaust and into the initial heater
baffle and the second being the emergency heater shut-off to the upper chamber
entering into the cabin that was damaged. Even with the the heat in the off
position.... I guess due to age just don't seal off the air as well as they
should, some heat was still entering the cabin. If you close the emergency heat
shut-off, it does a much better job of stopping heat flow into the cabin. Hard
to do if the cable is defective.
On the firewall on the left hand side you will see a small
inspection port on the firewall to inspect the flap for closure fitness for the
emergency shut-off. Making sure this device works properly can make a dramatic
difference in unwanted heating of the cabin.
Pics courtesy of Bob K., of Michigan! Thanks
Here are some innovative approaches to improving heat delivery
to the back seat passengers contributed to BeechTalk by engineer, Joe F. His
approach relies on the principle of "delta T" and the heat losses through the
ducting that delivers the warm air.
Insulating the ductwork in the engine bay that carries the
heated air is also part of Joe's solution. Joe reports using 1/4" aluminum foil
wrapped foam insulation. The aluminum in contact with the belly skin is not
likely to contribute to dissimilar metal corrosion issues, but what the heck do
If you've got heater box solutions worthy of CSOB
E-mail me with the details!