Engine Failure - AFP Air Filter

JordanGrant · #1 05-04-2006, 12:30 AM

A question for those with Airflow Performance fuel injectors.
My wife is flying off the test hours back home (I'm deployed right now) and had a bit of a scare last week. After flying 2 hrs in the morning and 2 hrs in the afternoon with absolutely no problems, she was on her way back to the home drome when the engine started to lose power and eventually die (windmilling rpm). She executed the engine failure checklist (switch tanks, boost pump on, full rich, etc), with no success. As she picked out a field and set up for best glide, she also went to idle on the throttle, then back to full power. The engine came back to life for a few seconds before dying again. So she did the same thing over again, same result. This procedure gave her enough extra power to make it to the field and execute a semi-deadstick landing.
Upon taking the cowl off on the ground, she discovered that the air filter assembly had fallen off the throttle body and was resting on the bottom of the cowl, partially blocking air from the throttle body. At full power, the engine was probably flooding (not enough air) and that's why it lost power. As she pushed the throttle out and back in, the engine found a balance where it could run, giving some power back.

My question is thus: Has anyone else had (or heard of) having the air filter assembly come loose or come off? On the AFP, it is held on only by the tension of that round retainer ring. I thought mine was secured tightly, but obviously it was not. If this is the only case anyone knows of, then clearly our procedures are at fault. If its happened to others, then maybe we should pursue a way to better secure that thing.

Be careful out there,

Jordan Grant
RV-6 N198G
In testing while I roast in the desert

rv8ch · #2 05-04-2006, 01:25 AM

Jordan, I can't help with the air filter, but just want to say congratulations to your wife for getting back to the airfield safely. Great job!

Dean Pichon · #3 05-04-2006, 05:12 PM

Such a failure has occurred at least once previously. The in-flight symptoms were similar as was the outcome. We later surmised the ring separated from the air induction tube because of the installation procedure.

In this case, the ring was fastened (and tightened) to the airbox plate prior to being clamped to the air induction tube. This prevented the ring from closing tightly around the induction tube. Installing the ring to the tube first (followed by the installation of the airbox plate) has allowed the air filter housing to remain attached for several years.

Of course, I have no idea if this is the same issue you experienced...

Good luck,

Dean

briand · #4 05-04-2006, 06:31 PM

Quote:

Originally Posted by JordanGrant

My question is thus: Has anyone else had (or heard of) having the air filter assembly come loose or come off? On the AFP, it is held on only by the tension of that round retainer ring. I thought mine was secured tightly, but obviously it was not. If this is the only case anyone knows of, then clearly our procedures are at fault. If its happened to others, then maybe we should pursue a way to better secure that thing.

Jordan Grant
RV-6 N198G
In testing while I roast in the desert

Not sure exactly what your talking about but if the securing device is a standard retaining/snap ring (the kind with the two holes for the pliers that get "pried" apart for installation), you should have lockwired it. Maybe you did or maybe you can't.

markscogg · #5 05-04-2006, 07:56 PM

I cleaned the Allen bolt and the threaded hole with acetone. Then used the blue (removable) loctite.
As mentioned above, tighten the allen screw BEFORE the 4 airbox screws. And make sure the holes in the airbox mounting plate are large enough so they don't prevent the ring from locking on the throttle body.

PS - Drill and safety wire the airbox bolt heads per the service letter.
I don't think you will be able to drill the allen bolt though.

Mark
Flying 06

N733JJ · #6 05-05-2006, 07:36 AM

Jordan,
Yes this has happened to me as well though it was only a reduction in power. I also noticed higher than normal CHT's and more heat coming through the firewall to my feet. This was caused by the airbox blocking the flow of the exiting air.

Part of my oil change checklist (25 hours) is to check the security of the airbos. Get that allen bolt as tight as possible! I have had no problems in the 200 or so hours since I started these regular checks.

Scott A. Jordan
N733JJ
560 hours

JordanGrant · #7 05-05-2006, 10:17 AM

Sounds like a tightened-up retaining ring should really be all that's required. That's what I'm going to recommend to the frau.

I didn't know about a service letter for drilling/safety wiring the bolts. With self-locking nutplates there, I'm surprised it would be necessary. There should be very little stress on those bolts and it would take a heck of lot of vibration to work them loose enough to cause a problem.

Brantel · #8 05-05-2006, 12:56 PM

This has nothing to to with an RV but when I was on my last hour of night flying for my private ticket back in 1989, I had a 152 go to no more than 1100 rpm on takeoff about 400 feet agl about halfway into a upwind turn off the end of the runway.

The pucker factor was way high because at KMOR on 23, there is no options for a landing out in the industrial park off the end of the runway. I know you are not suppose to attempt to turn a 180, but I did and survived. I turned 45 degrees at a time to see if I could make it. The 1100 rpm was just enough to get me across the threshold. Thank God there was little to no wind that night.

The problem was the filter screen that covers the air inlet sucked into the carb and choked it off.

We had to push the airplane back to the hangar because it would not develop enough power to taxi back.

briand · #9 05-05-2006, 04:31 PM

Nothing profound but I just thought I'd post anyway.

http://www.auf.asn.au/scratchbuilder...g.html#general

markscogg · #10 05-05-2006, 07:06 PM

Quote:

Originally Posted by JordanGrant

Sounds like a tightened-up retaining ring should really be all that's required. That's what I'm going to recommend to the frau.

I didn't know about a service letter for drilling/safety wiring the bolts. With self-locking nutplates there, I'm surprised it would be necessary. There should be very little stress on those bolts and it would take a heck of lot of vibration to work them loose enough to cause a problem.

The service letter is ONLY for the four 1/4 - 20 bolts that hold the top plate of the air box to the anodozed aluminum "dougnut" with the allen screw in it.

If these bolts come loose they will go through the intake.......

Mark
Flying -6 (with AFP fuel injection)