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The alternate air door is between the air filter and the intake
manifold. Should the air filter ice over or suffer a bird strike or in some
other way fail and close off or substantially restrict the air supply from the
filter, the alternate air door is designed to open and keep the engine running.
The thinking is that it is a last chance option for a failed system. At this
juncture protecting the engine from FOD is out the window and getting on the
ground safely is the only mission.
Lynn E. Hanover
In a message dated 7/6/2013 9:57:18 A.M. Eastern Daylight Time,
ARGOLDMAN@aol.com writes:
please change the word ' upstream in the phrase "---alternate air
flapper, upstream--" to downstream.
THX
Rich
In a message dated 7/6/2013 8:38:43 A.M. Central Daylight Time,
ARGOLDMAN@aol.com writes:
Greetings Lynn,
I understand the first part of your post eg. damaged housing causing
drag, but I am scratching my head about how an alternate air door, in the
intake, would address that problem. It is my understanding that the
alternate air door is placed to allow air breathing in the case of induction
system blockage upstream of the door itself, i.e.. induction
icing bird etc impaction which strangulates the system defeating the
normal flow of air to the chambers.
This alternate air, if used, is unfiltered.
So my question is how does this air coming into the system, through the
alternate air flapper, upstream of the air filter, eliminate the
problem of blowby in the case of the type of damage that you
mentioned.
My system allows me to shut off the injectors and ignition to each
trochoid (in my typically anal approach, I can shut off each injector and
coil separately). I can use the EGTs to tell me what trochoid is problematic
and electrically and fuelishly isolate it. this should reduce the
drag.
Happy 4th of July weekend to all
Rich
In a message dated 7/4/2013 9:42:41 A.M. Central Daylight Time,
Lehanover@aol.com writes:
While a piston engine can survive some dreadful FOD damage, a
rotary cannot. Even a tiny stone can turn your engine into
ballast.
Many think that one rotor housing can get you home. Not the
case. Extend the glide? Maybe, depending on the damage. A damaged
housing may connect the firing chamber to the next mixture filled
chamber and fight the running housing with lots of drag and heat. An
alternate air door in the intake would eliminate
the problem. It is common on production aircraft and part of
a Life Extension program.
Lynn E. Hanover
In a message dated 7/4/2013 10:06:31 A.M. Eastern Daylight Time,
steveizett@me.com writes:
Thanks Rich
Steve
The necessity of a filter may depend on where you fly from and
where you expect to fly. Occasionally there are swarms of
insects that we fly through (at least in my part of the country) which
will be ingested. those little exoskeletons are quite abrasive.
Mooney in their old "Super 21s" had a flap which
allowed one to select ram air at cruise.
In a carb, when operating on carb heat, the air is
unfiltered.
Rich
In a message dated 7/4/2013 7:48:58 A.M. Central Daylight Time,
rwstracy@gmail.com writes: > 2. I
take it that filtering is essential. How does water effect filter
material? What filter material is best.
On a car, a
must. On an airplane, just be careful where you put inlet (
keep it high) and don't taxi behind someone on a dry dusty
taxiway. Never had an air
filter.
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