Sam James Cowl - Alternate Air or Not?

mikemalone · #1 01-05-2019, 02:03 PM

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.

Mark33 · #2 01-05-2019, 02:20 PM

I?m also building a -7 with the S.J. cowling and I?m not installing the alternate air inlet in mine.

Mark

N941WR · #3 01-05-2019, 04:48 PM

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.

hgerhardt · #4 01-05-2019, 05:15 PM

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.

N941WR · #5 01-05-2019, 06:38 PM

Quote:

Originally Posted by hgerhardt

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.

Quote:

Originally Posted by N941WR

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.

Charles in SC · #6 01-05-2019, 08:03 PM

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.

RV6_flyer · #7 01-05-2019, 08:30 PM

Quote:

Originally Posted by hgerhardt

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.

KatanaPilot · #8 01-06-2019, 05:13 AM

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.

maniago · #9 01-06-2019, 06:56 AM

I installed it in my SJ cowl - never considered not doing it. Cant use it if you dont have it.

BillL · #10 01-06-2019, 03:51 PM

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.