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Air filter broke in flight

I've never seen one do that before.

As a guess, it would seem that you had a backfire...probably at startup.
 
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Hi Folks,

Anyone have expirience this kind of air filter failure in flight???:eek:

Please give me some advise I don't want it to happens again.



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Yes, looks very much like the filter in my buddy's IO-360-powered RV-8 after a backfire during a hot start. It managed to blow the filter all the way out of the plane one time.
 
Yes I have a sniffle valve.

How can a back fire destroy the filter and not to damage the fiber glass snorkle:confused:

How may I prevent this to happens again????

A back fire doesn't mean Fire comes all the way back to the filter. Back fire just means fuel/air mixture burned somewhere within the induction system. This produces a lot of pressure just like it does within a combustion chamber. If the pressure is high enough it can blow out the filter.

As for preventing it... I have been flying RV's with fuel injection and a snorkle for more than ten years and I have never had a backfire. With that being said it could be your starting technique or an issue with your airplane (or even a little of both).

First place to look...If your engine has two standard magnetos and only one of them has an impulse coupling (typically the left one), make sure your ignition switch has the grounding bar installed for disabling the non-impulse mag while starting. If you have an impulse and a non-impulse mag and you are using separate toggle switches for the mag switches, make sure you are only switching on the impulse mag for starting (switch on the non-impulse mag after start).
 
A back fire doesn't mean Fire comes all the way back to the filter. Back fire just means fuel/air mixture burned somewhere within the induction system. This produces a lot of pressure just like it does within a combustion chamber. If the pressure is high enough it can blow out the filter.

As for preventing it... I have been flying RV's with fuel injection and a snorkle for more than ten years and I have never had a backfire. With that being said it could be your starting technique or an issue with your airplane (or even a little of both).

First place to look...If your engine has two standard magnetos and only one of them has an impulse coupling (typically the left one), make sure your ignition switch has the grounding bar installed for disabling the non-impulse mag while starting. If you have an impulse and a non-impulse mag and you are using separate toggle switches for the mag switches, make sure you are only switching on the impulse mag for starting (switch on the non-impulse mag after start).

Here is my hot start technic (from lycoming manual)

Mixture ICO
Throttle Full
Boost pump off
Just left Magneto ON (the one with impulse coupling)
Cranck

Once engine fire
Mixture rich
Throttle idle
Magnetos both ON

This technics works every time, I have try some other with the throttle in different position than full, because I have read here full throttle technics could be dangerous but I have been not able to start the engine and I have run out of battery.

Please give me some advices
 
Fernando,
I use the exact same technique with the exception that as I crank I start pulling the throttle to idle. At some point (usually about half way) it starts. The idea is that by pulling the throttle to idle, the engine finds a position that the air/fuel mixture is just right for starting.

Hope this helps.
 
Check timing of magneto's

Fernando,

I had the same problem on an RV-8 with an IO-360 M1. When I started it the first few times the engine backfired and blew the filter element out of the filter box. It also happened during a flight. It turned out that there was a timing problem with one Magneto. The points were broken (brand new mag). Once the magneto was repaired and timed properly, the problem went away.

Dan Miller
RV-8 790 hours
 
Filter broken from holder

I had this occur serveral times and I attributed it to a backfire. I ended up putting a screen over the filter to prevent it bending and subsequently pulling out of the bracket holding it in place. I think my starting technique has improved as this occurred when I first started flying my plane, I am confident the loose screen keeps the filter in place regardless.

Steve Anderson
RV 7A Flying
130 hours
Lafayette, La.
 
Happened to me too

I have had this happen to me twice in the past 650 hours. Both times it occurred while starting (back-fired) after a 2 or 3 minute shutdown. The sniffle valve is mounted in the center of the sump. With a tail dragger, the rear of the sump is lower than the sniffle valve and allows fuel/vapors to collect. Now, I lift the tail up to allow fuel to drain through the sniffle valve for those occasional brief shutdowns. This may not be the cause, but no problems in the past 200 hours using same hot start procedures.

Bill
RV-7 N151WP
Barrett IO-390
Lee's Summit, MO
 
Just this morning I was watching inside the sump and even I have a sniffle Valve installed I found fuel in the sump (24 hours after stop engine). If I lift the tail there were some fuel out of sniffle valve, so I am thinking that this fuel is back firing at hoy start.
 
Backfiring is usually caused by excessively lean fuel/air ratio or incorrect ignition timing. It can happen if the pilot advances the throttle while cranking the engine thereby creating a lean mixture. Cranking the engine with the throttle wide open could also set up a lean mixture and cause a backfire.

I have never heard of starting a FI Lycoming with the throttle wide open. Besides the possibility of a backfire it is sure not good to have the engine roar into life with cold oil and no oil pressure(initially). There is a lot of good info on start procedures in this forum if you do a search of "engine start procedure" .

The following start technique has always seemed to work for me:

Mixture full rich
Throttle wide open
Prime until fuel pressure STABILIZES
Retard throttle to 1/2'' above idle
Mixture full LEAN
Keep cranking until engine catches
Mixture full rich
Be ready to give some more prime if the engine starts to die(particularly when engine is hot)

If this technique does not work there could be something else wrong( incorrect ignition timing,bad magneto???)

To stop the filter from blowing out again, you could install a spring loaded backfire flap somewhere in the snorkle. Radial engine installations always have them to stop backfires doing any damage.

Good luck
Cheers
Graham
RV6 flying
 
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