Hello All:

           I noticed that my venturm were corrupted with foreign particulate after landing in grass.  Now the question becomes, is this detrimental to the engines? If so I guess that it is time to fit  pieces of panty hose over the venturm to help prevent this from happening.  But, since the engine is not running, would it be just as good to flush out the venturm after a flight.

         Suggestions?

                                                                                                                                                        Frank

          Hello All:

           I noticed that my venturm were corrupted with foreign particulate after landing in grass.  Now the question becomes, is this detrimental to the engines? If so I guess that it is time to fit  pieces of panty hose over the venturm to help prevent this from happening.  But, since the engine is not running, would it be just as good to flush out the venturm after a flight.

    I would suggest some sort of screen, panty hose at least, or the Bru-Line filter (which I am led to understand can be had from Brodak). Grass probably doesn't wear anything, dirt or dust probably does. I have used panty-hose filters for years ,mostly for the diffusion more than the filtering, but I haven't had any significant issue with wear on my AAC engines, except for a single flight where I knew as soon as I started the engine, there was going to be a dust issue.

   I think the Bru-Line "fine" filter (tan/beige/yellow depending on who you are talking to) is pretty effective, because they get obviously dirty pretty quickly. The "coarse", a little harder to tell. Panty hose, hard to say, it would probably stop a big chunk (or in Ted's case, a honeybee...) and some fraction of extremely fine dust, but the gaps between the fibers are pretty good sized.

    I have had damage, not from grit, but from either bearing chips or glow plug elements. That's 2 cases of damage in maybe 1500 flights and 20 years, so it's not a big issue. We (David, Ted, and I, and Uncle Jimby before he went over to beepers and whiners)  fly off of grass at least 50% of the time.

   If we are talking vintage engines, ringed engines are usually *extremely fragile" and can be significantly altered by small bits of grit or dirt, but they are relatively cheap to repair (if you can find acceptable parts). Meehanite pistons/steel liners are reasonably tolerant of dirt but the damage can add up over time. They are much more likely to be damaged by improper settings and operation than they are small amounts of dirt.

    If it's just normal grass surface, without a lot of bare spots, then I wouldn't worry too much about it. But a filter doesn't hurt anything, while providing useful diffiusion AND the fuel suction will be slightly improved - which, if you are putting .280 spigot venturis on HP 40SS's, might be just what you need.

    Brett

p.s. I just read Tim's response - of course, takeoff is the case you have to care about, far more than just picking up a few stray bits on landing

I was reminded 2 days ago to cover all my venturi with pantyhose after an unscheduled heavy landing! We had rain recently and the ground was soft so I ended up with a plug of damp soil and grass stuffed into the motor. This has been prevented in the past with stretching tight and tying off a ribbon of pantyhose around the front of the engine. Gently pull on both ends of the material and out comes a nice clean plug of muck that didn't get into your engine. Cheap, effective and it works.

Gently pull on both ends of the material and out comes a nice clean plug of muck that didn't get into your engine. Cheap, effective and it works.

  It will also keep the stray bumblebee out of the venturi, we discovered, but too late to help Ted.

    Brett