Glassed Filtered Air Box Alternate Air Door

[aerhed]

Paul, good idea. Bill, yeah that's the stock door thanks.The key words in your post are "maintained and inspected". Part of what we're doing here is to guard against a deficiency in those regards. Other guys, am I correctly remembering a version that just hooked under tabs and dangled or did I dream that?

[paul330]

Let's remember that the 50 hour check should involve cleaning and re-oiling the air filter so you should get a good look at the structure of the box........

Sorry, did I say I love this forum for highlighting potential problems like this so you can deal with them before they become an issue!

[mcphersn]

Well, I don't know about the 10, but I've tried pretty much tried all of the above on my 1000 plus hour 6, and it now has no alternate air. I'm trying to stay in the southwest, where ice is harder to come by...

[dcpearso]

Hey all, Thought I would share an issue I had just a week ago. Cruising along at 4500' and had an engine failure. Put down in a paddock and all ppl walked away.

Upon investigation the rivets holding the alternate air in place had let go and pulled through the fiberglass air box. The FCU air inlet was blocked by the alternate air panel and that's what had caused the failure.

Now fabricating a fully aluminum air box now....

Definitely worth the few $$ and replace your fiberglass box. It should almost be an AD. I know people have made their own and have seem some really nice fiberglass ones on here but 1 engine failure too many for me

[Bill.Peyton]

Do you have some photos of the box that failed showing how it failed? Also your new design? Also how many hours?
Thanks

[jchang10]

Wow! Glad you got down safely. How did the airplane fare? I know we are not supposed to care but as a builder, i do.

The airbox is probably the most overlooked critical component on the plane. IMHO it is absolutely NOT good enough stock. The drain tube, the air seal, the filter, the alternate air door, and the alt air door control all go into this tiny little kit that is too easy to overlook. I have had to redo or tinker with almost every aspect of it in phase 2.

[RV10inOz]

Dan,

You did a great job indeed. Not a scratch on man, machine or beasts!

For those interested, the following are pic's of the fabricated box we made a couple of years back.

This in my opinion is a SB needing to happen.

See ya tomorrow Dan!

[bruceh]

I leveraged a bunch of information out of this original thread when adding the alternate air to my Filtered Air Box. I tweaked the design a bit, and am really happy with the way it turned out. With my alternate air system on the airbox, there is no way anything can be sucked into the engine. The alternate air door opens and closes smoothly.
The details and photos of the construction are in among the Engine section of my web log.

[AMac]

What exactly is it that is wrong with the VANS design?

- OK, it's not the most elegant but it works
- You can't close it in flight but if your main intake is blocked, why do you want to? It's not as if it's something you want to be opening and closing on a regular basis
- as far as I can see, if any bits do come loose, they are going to fall into the cowl, not the engine. Having said that, I can see the pop rivets through he fiberglass are a weak point and I am going to glass over the inside. I also used RTV when I fitted the ring.

In my opinion, the original design was seriously flawed, if you're still running it, you shouldn't!

The failure experienced by dcpearso was from a temporary fix. The original design kept flapping on the initial test flights, I asked the chap that helped me build the aircraft if he had any ideas for a fix. Unfortunately he sealed the flap shut permanently. (non pilot, possibly unaware of the consequenses). I didn't check the fix.

Lesson 1: You as PIC and more importantly the builder MUST check these 'fixes'

I'm not a big 'what if' person. What happens.....happens. But the consequences of this incident could have been disastrous. The incident included a PAN-PAN call that escalated to a MAYDAY. ATC did a great job in support, dcpearso did a remarkable job putting it down with no injury or damage. The aircraft was flown out of the paddock the next day. Testament to the aircraft, there was NO damage!

Lesson 2: Maintenance Authority comes with a massive responsibility, it's a privilege.

Not that I didn't understand the gravity of the privilege, but there's more to it than just inspecting under the panels and changing the oil.