Hey guys, my crazy side visited me last night while I slept and planted a
seed. Here is what my alter ego said-
If we are going to end up with a functioning EFI, why not use it to set the
RPM we want like jet engines do? We could have say 3 or 4 detents or set
points, WOT, cruise, flight idle and ground idle and let the engine control
the rest of it automatically. No more prop overspeeds, etc. Set the RPM at
6000, start a climb and the computer would keep the 6000 by adding more
throttle. Start a descent, same thing but backwards, the EFI would throttle
back to keep 6000.
It would require a servo motor on the throttle, and not much else. The
throttle cable could still be there for manual over ride if the servo motor
failed. Kind of like cruise control in cars. Turn it on and its on, tap
the brakes and its off.
Kevin Alderman
Now this sounds like a great idea. A good way to reduce pilot work load
at high load moments.
- Mark LaPierre
I am not building an RV, so flutter is not one of my primary concerns, but
it is always a potential problem. I am building a composite, and reinforced
the dickens out of the tail/ fuselage intersection and spent way too many
hours balancing my control surfaces. The overspeed (RPM) came from
observing students at the local flight school where I rent planes. I have
noticed that quite a few pilots will overspeed an engine in emergency
situations- like practicing emergency descents- they tend to push the nose
down and then sometime after worrying about Vne figure out that the engine
has passed redline. Not an everyday event, but it does happen in particular
with a carbed Cherokee P28-140, poor abused plane. One student at the
school has locked the brakes twice on this plane on landing and once on the
172 to the point of blowing out the tires on the runway. The wheel pants
have been gone for a while. Not that this idea would be for students, but
we have the system, all that would be needed would be a servo motor, a
controller and a few more lines of code. And just like cruise control, any
pilot input would over ride the system.
As I get more toward completion of my toy, I will put some more thought into
this. Since performance will vary with each plane, the RPM would be
programmable by the owner in say 4 places. Pull from WOT to the first
detent and then she goes into flight cruise mode with auto leaning to a
point say 10% rich. You can further lean if you like, or maybe normal
cruise mode would lean to peak EGT after finding a way to read it. The next
detent is cruise descent, the next could be flight idle. All of this could
be managed with microswitches at the detent points. Spend say 4 seconds at
the detent and the system takes over automatically. Move it from the detent
and its all yours again.
My OCD nature will push this thing straight to a FADEC, so I might as well
look at it this way from the beginning- if the other sensors aren't there
the system can compensate for it and let the pilot do the leaning,
adjustments, etc.
I will keep you posted. In the meantime, throw ideas at me and I will see
how it can go into the system.
KA
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