Need more information about the BH5 horizontal induction.

[schu]

Questions:

Which fuel system is it mounted to? A bendix?

Will it work on an airflow performance mounted to a parallel valve io-540?

How does the alternate air work? I'm assuming push pull cable? Is the hole on the side the alternate air, or in the front.

Does the bearhawk 5 have a fiberglass cone around the filter or does it just have the nose bowl inlet the blasts cool air onto it?

If it doesn't have a cone, would making one cause the engine to have a little more MP at cruise? (Free HP)

If it doesn't have a cone, do we really need alternate air? The odds of that entire filter being clogged when it's in open space in the cowl seems very remote to me.

Will we be able to buy these?

image_7330.png

[Collin Campbell]

Let me see if I can answer some of your questions.

The fuel system is an Avstar, which I am told is similiar to the Bendix. I think it would work on most any forward facing (horizontal) sump. The bolt pattern on the servo might differ some...I am not sure, but it could be made to fit.

I am attaching a picture of the push/pull cable setup. Also a picture of the adapter from the front. There are actually 4 holes that allow for alternate air...a rotating "collar" opens and closes the holes. It's a pretty slick and simple design, I think.

The filter is enclosed in a fiberglass cone or shroud and is sealed off at the back by a foam gasket. So we have ram air, which should increase the MP somewhat. I have a pic also of the nose bowl under construction.

The question..."Do we really need the alternate air?" Good question, as I know many RV aircraft that are flying without it. But...I suppose it could happen, the filter is enclosed in the shroud and if it gets stopped up somehow, we have to get air in somehow...a bird strike...a stray trash bag...ice...etc.

I just got off the phone with Bob, so with his permission I will share the current situation with the alternate air set up. Bob has had me do some tests
with the cowl opening taped up to see if the alternate air system is adequate. It seems that as of now the airflow over the air sensor on the front of the servo is not sensing the airflow like it should. It seems the air coming in from the 4 holes is blowing more "across" the sensor instead of sensing ram air flow. (least that's the best way I know how to explain it) I was only able to operate the engine @ 1400 rpm before it began to act up. Bob tells me that all servos don't have the center sensor protuding out the front...some acually have 4 separate sensors...so things
might work differently...have to do more testing to see. Hope we can come up with a working solution, it seems to be a great idea otherwise.

Can you buy one? I don't know for sure what Bob is planning to do. Give him a call, he tells me that he has had quite a bit of interest in the design. Collin

[robcaldwell]

Thanks for sharing this information, Collin. I have a similar set up on my IO-540. Do you have any pics of the fiberglass cone/shroud? I purchased mine from James Aircraft, but really had to modify it.

[zkelley2]

Induction ice is the most commonly referred to reason for alternate air. Usually on the filter itself. That and if turbocharged, in case the thing eats itself, one downstream of that.

[svyolo]

Do most airbox setups have any drainage for rain/condensation?

[svyolo]

I was trying to guess what the rotating alternate air setup was. I would have guessed a rotating disc on the back of a flange for the air filter/box. I think that might be what I do.