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Sam James Cowl - Alternate Air or Not?

mikemalone

Active Member
I have bought a Sam James cowl. Do most builders install the alternate air function? For that matter, even with other cowls, what is the best guess as to the proportion of builders that fit one? How many times have people heard of pilots having to use it? One occasion might be a birdstrike blockage. Another, might be a clogged filter. my feeling is to keep it simple and omit it. I would be interested in the views of others.
 
I?m also building a -7 with the S.J. cowling and I?m not installing the alternate air inlet in mine.

Mark
 
I have the short cowl on my O-360 and do not have an alternate air door and have never had a need for one in 11 years.
 
An ATP flew his -6 out of Torrance one night towards Mammoth and flew into a snow storm. As far as anyone knows, the snow clogged the air filter and he crashed into the Sierra foothills. The stock alternate (heated) air system with the FAB setup adds the air upstream of the filter, which does no good if the filter is clogged already.

I believe this incident prompted Van's to implement their (emergency) alternate air solution.

I met the pilot of that airplane for the first time at TOA an hour before he died. I had checked out his airplane to figure out some build details for my own -6 project.
 
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An ATP flew his -6 out of Torrance one night towards Mammoth and flew into a snow storm. As far as anyone knows, the snow clogged the air filter and he crashed into the Sierra foothills. The stock alternate (heated) air system with the FAB setup adds the air upstream of the filter, which does no good if the filter is clogged already.

I believe this incident prompted Van's to implement their (emergency) alternate air solution.

I met the pilot of that airplane for the first time at TOA an hour before he died. I had checked out his airplane to figure out some build details for my own -6 project.
Which alternate air door?

A number of engines have ingested parts from the alternate air door, which is why I haven't put one on my RV.

As for flying in snow, I have flown through a good bit of snow in my RV and never had an issue.

Here is a post I made from a few years back on the subject. This carb heat muff works much better than the "stock" van's muff.

The picture also shows the mode I made to the FAB and carb heat flapper valve to accommodate the short Sam James cowl with a carb.

I went with this SS Heat Muff from Wicks with good results.

Here is a picture of it installed on my O-360. Keep in mind, my FAB and heater valve are slightly different due to installing a short Sam James Holey cowl.

carb%2520heat%25202.JPG
 
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I am putting the alternate air on with my James cowl. I have needed it once in 40 plus years of flying and I am glad I had it.
 
An ATP flew his -6 out of Torrance one night towards Mammoth and flew into a snow storm. As far as anyone knows, the snow clogged the air filter and he crashed into the Sierra foothills. The stock alternate (heated) air system with the FAB setup adds the air upstream of the filter, which does no good if the filter is clogged already.

I believe this incident prompted Van's to implement their (emergency) alternate air solution.

I met the pilot of that airplane for the first time at TOA an hour before he died. I had checked out his airplane to figure out some build details for my own -6 project.

Knew the pilot, co-pilot, and airplane. Heard the ATC tapes of the flight. Flew out to see the crash site. 300' higher or 30-degrees left or right and he would have missed the mountain top is my observation of the crash site.

NTSB report LAX01LA110 REPORT and SUMMARY.
 
It's not that complicated to install. Hardest part was getting the geometry of the actuator arm set correctly and trimming the inlet to clear. I have the extended cowl and horizontal induction with Mk 3 inlet, so your setup might be different.

The instructions provided with the SJ cowl are pretty good and most of the components needed came with the cowl kit. Had to buy a push pull cable from either Van's or ACS as I recall.

Certainly a personal choice, but given the possibility of inlet blockage, I think it's pretty inexpensive insurance.
 
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I installed it in my SJ cowl - never considered not doing it. Cant use it if you dont have it.
 
I installed mine, there may be a better way

There is a 7 builder in Australia that made his alt-air valve out of a car throttle valve. He ran a tube up to it so it was in a more favorable location. I thought it was a great idea. It seals well, easy to operate, and intake suction has no effect on the operation forces. It could be filtered too.
 
I had an "incident" with a RV transition training student where he left the intake plugs in. He assured me the airplane was preflighted and I got distracted with someone and did not do my customary walkaround even if the student says was preflighted. Lesson learned there but anyway. Took off and right after we're airborne I notice we've got a big problem. On crosswind I pull alternate air and immediately knew what the problem was.

Something is better than nothing.

I have an "automatic" spring loaded door on my Rocket intake shamelessly copied from a Bonanza.
 
A different (in)take on alternate air

There is a 7 builder in Australia that made his alt-air valve out of a car throttle valve. He ran a tube up to it so it was in a more favorable location. I thought it was a great idea. It seals well, easy to operate, and intake suction has no effect on the operation forces. It could be filtered too.

That would be me!:D
Rather than a flap type door, I stripped most of the hardware off a Lotus Elise plastic throttle body. Made my own fibreglass duct which extends from the James filter assembly base and a custom actuating lever with cable support bracket.
The other benefit of using this butterfly valve is using the throttle position sensor to show valve position on my G3X. The valve can be operationally tested and verified open or closed at any time.
 
I am at that point right now trying to figure out an alternate air system on my custom FAB. IMHO, to be truly effective, the alternate air source needs to be located post filter (unfiltered air). It does no good if the filter itself is clogged shut with whatever. Its not just the air inlet that could get blocked. I have looked at Dan H. posts on his automatic AA door in an earlier post and will probably do something similiar, except I am using a cone filter so will need to fab up a box behind that for the AA door.
 
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Alt air filter setup

Here’s how mine works:
This is the base which attaches to the fuel servo inlet.
3EC3FDEB-D585-4700-A23E-CB08B2B935D5.jpeg
I modified the James diffuser plate to match the alt air intake. This plate also seals off all fasteners and anchor nuts so even if they come loose, they can’t get sucked into the engine.
019AA6D2-0BAC-4B4B-9BF5-5AF9797F62A4.jpeg
The diffuser fits into the base like this. Alternate air comes in AFTER the filter.
AB90FCDB-621A-43A9-A67B-42E68E903024.jpeg
The conical filter seals to the diffuser plate and base like this;
79D9274C-82DF-4C5F-BE99-9CEA58CECA53.jpeg
Then the housing goes over the whole assembly to seal and hold the filter.
6F47F847-C8C0-43D2-9F66-65159EC3C31A.jpeg
And the finished assembly looks like this. The alternate inlet has a stainless steel mesh screen - I couldn’t find a good filter.
E30D6924-CCED-4405-B303-C1AFA3CB5365.jpeg
 
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