Subject: [FlyRotary] air filters and scoop intakes

 

Hi All

 

I have 2 questions that people have alluded to on the list but I have

not seen them addressed directly. 

 

1) Do rotary aircraft engines need air filters?  I have seen pictures of

engines with air filters but man pictures comments on the list,

particularly from Jerry have led me to believe that not every one uses

air filters. No air filters would greatly simplify design of CF p-port

(eliminate plenum) and other manifolds.

 

2) Do most planes have scoop intakes for pressure recovery from air

going intake manifold?  It seem to me a lot of the intakes terminate

after the throttle. While this would make construction easer it is a

loss of some potential HP.

 

Alex Madsen

 

Alex;

 

I’d imagine that the need for a filter would be similar for rotary or piston.  I chose to go without an air filter because the pressure drop would negate the bit of performance improvement you can get from ram-air induction; unless, of course you have large filter area, which makes the installation troublesome.  I do recommend a screen to keep out anything larger than about 1/16”.

 

Once you are away from the ground there is generally no need for a filter.  You may ingest a bug or two, but a little organic matter isn’t going to matter.  It depends on the landing strips you expect to use, and where your induction scoop is located.  I put mine above the wing on my Velocity (prop in back) thinking there is little likelihood of picking up any dirt.

 

Al