Bang goes the Jab motor

[Flyer]

Well maybe not quite that serious but it did put me on notice.

 

I took a mate for a fly today, Tooradin over to Traralgon, down to Yarram and back to Tooradin.

 

I hadn't planned to stop at Yarram but bladder made an executive decision, so a stop was called for some weelief.

 

No problem, jump back in the plane and get out of there.

 

Climbing out and passing through about 1500agl, BANG or probably more a thumpy type bang came from the engine as well as a shudder.

 

I can tell you I had 4 paddocks picked out to put the plane in while I checked ops normal. Temps normal, pressures normal everything normal.:confused:

 

I chose to make sure I had a suitable landing spot available the whole way home just in case something did fail.

 

Spoke to the LAME and CFI when I got back there were various suggestions from small fuel vapour lock to a fouled plug that caused the bang in said engine...:raise_eyebrow:

 

Anybody else experienced this with a Jabiru 4 cyl before and if so, did you work out what caused it ? i_dunno

 

 

[BigPete]

A similair episode happened to a friend of mine last year. Landed straight away (fortunately close to the airfield) and pulled off the cowls and checked it out completley. Nothing wrong - the only thing we could think of was a bit of ice going thru the motor.

 

The conditions were conducive for ice forming. We couldn't prove it, but was the only thing we came up with. The motor in question has done a further 140 hours with no trouble since.

 

regards

 

 

[Guest brentc]

Was the fuel pump on Phil? Manual says until top of climb..........

 

 

[Flyer]

We were on climb to A045 passing through about 1500 fuel pump on and ops normal when it happened. I checked ops normal and all seemed ok after that.

 

No even so much as a murmur the whole way home...

 

I think our LAME suggested ice as a possibility as well.

 

It was probably between 0-5 degrees (guessing no OAT) and there was certainly enough moisture around to support the ice theory...

 

Thanks for the suggestion Big Pete.

 

Curious to hear further thoughts Brent....

 

 

[facthunter]

ICE?

 

Good informed guess. Why not? Carb ice is an ever present threat. Why not consider fitting a carb temp indicator, you might get a bit of a surprise.

 

These backfires have a fair amount of potential to dislodge/ damage carburetters, so I would suggest an inspection should be carried out sooner rather than later. Nev..

 

 

[Flyer]

Hi Facthunter

 

Good suggestion for the carb temp but being a club plane I doubt it will happen....

 

It is starting to sound like carb ice and I admit it obtained my total and undivided attention at the time.

 

The motor never missed a beat after that....and I made damn sure that I didn't fly over any tiger country on the way home either :raise_eyebrow:

 

I notified our LAME and left it with him to check out....

 

 

[poteroo]

Sounds like carb ice to me. We have ci quite often on the south coast of WA. We teach doing the power checks last - so that any ice accumulated during taxi is cleared. Also seems impt to use wide open throttle all the way on climb, rather than some form of reduced power/cruise climb.

 

happy days,

 

 

[Flyer]

Had a further chat with our CFI yesterday and reviewed what I did. His thoughts are also ice because I didn't use carb heat before take off. My reasoning was that I was on a dirt runway and didn't want to suck in dust.

 

Heres what it looked like before I started rolling...

 

Start aircraft and get it moving straight away because I'm on a dirt runway with very coarse sand

 

Do runups on the move

 

Keep moving as I lined up

 

Engine ops normal and fuel pump on

 

applied full power rolling

 

full power was still on and the fuel pump was also on when the motor had its episode.

 

We think it accumulated ice during the taxi and runup and had no way of clearing.

 

Sorry for hammering this thread but I'm trying to understand what happened...I dont like unexplained engine bangs....:confused::big_grin:

 

thank you all for your input sofar...

 

 

[Captain]

I have a carb temp probe on my 3300 and it is fascinating to watch how often the temps get to carb icing levels ...... sometimes when you least expect it.

 

As a result of watching it I now find I use carb heat more than I used to and for a little longer than I used to.

 

 

[brilin_air]

carb ice

 

Hi Geoff, The temps for carb ice,are you seeing them on the ground while taxiing or when you are at cruise ?

 

 

[Captain]

Hi Geoff, The temps for carb ice,are you seeing them on the ground while taxiing or when you are at cruise ?

More often than I expected while on the ground and almost any time that there is moisture in the air. On some of the longer taxi's that we get at Wagga I often pull the heat on (based on carb temp readings) while partway to the run-up area & without noticing the engine running rough. (it seems to me that once it starts to run rough there will be a fair bit of ice in the carb and I would prefer to get rid of it without a big cheesle of ice going on into the engine).

 

 

 

Not so much at cruise at 2850 or so, but have seen it a few times on descent around misty wispy cloud and when above the 2000 rpm which was the rule of thumb where I used to automatically use the carb heat before having the sensor.

 

 

 

I have read an article somewhere .... think it was by Cessna, which talks about ice forming in carbys when carb temp is showing 4C or so. I'll see if I can locate that.

 

 

 

As per my previous post, I was surprised how often it shows 0C or less than 4C at partial throttle settings. Also, see the panel reading that I recently posted in J230 @ YSWG which shows a carb temp of 3C at 2900 rpm at about 7000 ft and above patchy cloud with an OAT of 11C, so it can get down there, even at cruise.

 

 

 

[BigPete]

Don't worry about using carb heat on the dirt in a Jabiru, Flyer, as the carb heat air is still filtered. :thumb_up:

 

regards,

 

:big_grin::big_grin:

 

 

[Captain]

Further to my last note there is an ATSB article on Carb Icing at http://www.atsb.gov.au/aviation/editorials/e00016.aspx

 

And I now see that the same graph is on the RAA website.

 

Note the temps and humidity where they classify Icing at any throttle setting.

 

And their graph is below, which is similar to the one I have seen previously: ... bugger. Can't get it to load as it is too big. Can anyone else attached it here at slightly reduced definition.

 

There is also an Aircraft Icing Handbook at http://www.caa.govt.nz/safety_info/GAPs/Aircraft_Icing_Handbook.pdf which covers induction icing between pages 21 - 27

 

 

[MrH]

This the chart?

 

http://www.atsb.gov.au/pdfs/carb_icing.pdf

 

H

 

 

[Geoff]

Pete that's not the case on all Jabs.

 

 

[brilin_air]

Carb ice

 

I have always been told to use the carb heat on decent with the throttle backed off, and to give it a go just before turning on the runway for take off, but I am surprised that you've had icing when the outside air temp was around 11 degrees, I suppose it is more of a moisture related problem than an actual temperature problem, I have been lucky enough to not have experienced it yet fully, but as passenger in a friends aircraft we had a slight iceing after a fairly long slow decent and then applying power the engine wasn't as smooth as it was previously.

 

Thanks for the info guys

 

Brian

 

 

[Flyer]

I've downloaded the temps and dew points from about 3pm friday from the BOM site and put them into the chart as can be found on the PDF version that MrH has supplied...

 

Very interesting.

 

At 3pm the Temp was 11.6 deg C and the dewpoint was 7.7 deg C.

 

When I feed the figures into the chart The temp is

 

(1) 11.6C

 

(2) The Dew point depression is 3.9C (temp - dew point)

 

(3) where those lines intersect is almost slap bang in the middle of the Serious Icing-any power area of the graph

 

and

 

The relative humidity was 76%.

 

It looks like I scored a dose of carb icing and sucked some ice through the motor.

 

I'll be a bit more careful with carb heat before takeoff in future.

 

Thanks for the help guys.

 

I feel a bit better now having a better understanding of what possibly (and probably)happened :thumb_up:

 

 

[BigPete]

OK Geoff, fill me in. :confused:

 

All the jabs I have used (all certified) have the carb heat routed thru the filter. :thumb_up:

 

regards

 

:big_grin::big_grin:

 

 

[Old Koreelah]

Further to my last note there is an ATSB article on Carb Icing at http://www.atsb.gov.au/aviation/editorials/e00016.aspxThere is also an Aircraft Icing Handbook at http://www.caa.govt.nz/safety_info/GAPs/Aircraft_Icing_Handbook.pdf which covers induction icing between pages 21 - 27

Excellent publication, Captain. Thanks everyone for the thought-provoking posts. As I have said to Ian, this site is the Wikipedia of the Air. After reading everything on this thread and the associated resources, I have decided:

 

To use carb heat during all taxi operations and on descent (heated air goes via the air filter).

 

To extend the shroud much further around the muffler, which may double the heating effect.

 

To investigate relocating the temp probe to the throat of the Bing (could not find the info on location, Captain) so I can better predict icing, or at least move it closer to the intake where it will give me a better indication of how much I am heating the air.

 

 

[Captain]

Excellent publication, Captain. Thanks everyone for the thought-provoking posts. As I have said to Ian, this site is the Wikipedia of the Air. After reading everything on this thread and the associated resources, I have decided:To use carb heat during all taxi operations and on descent (heated air goes via the air filter).

 

To extend the shroud much further around the muffler, which may double the heating effect.

 

To investigate relocating the temp probe to the throat of the Bing (could not find the info on location, Captain) so I can better predict icing, or at least move it closer to the intake where it will give me a better indication of how much I am heating the air.

OK

 

The pic of the sensor is at photo # 6800 in post #185 on P10 of J230 @ YSWG.

 

Or http://www.recreationalflying.com/attachments/img_6800-jpg.1208/

 

Hope this all helps.

 

Regards Geoff

 

 

[Captain]

Excellent publication, Captain. Thanks everyone for the thought-provoking posts. As I have said to Ian, this site is the Wikipedia of the Air. After reading everything on this thread and the associated resources, I have decided:To use carb heat during all taxi operations and on descent (heated air goes via the air filter).

 

To extend the shroud much further around the muffler, which may double the heating effect.

 

To investigate relocating the temp probe to the throat of the Bing (could not find the info on location, Captain) so I can better predict icing, or at least move it closer to the intake where it will give me a better indication of how much I am heating the air.

Old K

 

The pic of the sensor is at photo # 6800 in post #185 on P10 of J230 @ YSWG.

 

Or http://www.recreationalflying.com/attachments/img_6800-jpg.1208/

 

Hope this all helps.

 

Regards Geoff

 

 

[Old Koreelah]

Old KThe pic of the sensor is at photo # 6800 in post #185 on P10 of J230 @ YSWG.

 

Or http://www.recreationalflying.com/attachments/img_6800-jpg.1208/

 

Hope this all helps.

 

Regards Geoff

Got it, thanks Geoff.

 

 

[Yenn]

Seems a bit odd to me. Carby ice will reduce power in the climb, if it is serious enough to produce a bang in the motor. I would have expected carby ice to be evident during taxi and when checking for icing as part of the pre take off checks. I had to abort a take off at Grovedale due to carby ice, in a C150. It just had a very reduced power output.

 

Keep a very careful eye on that plane until you are convinced it couldn't be anything else, also remember that what you are told may be someone putting his spin on a problem.

 

 

[nong]

I've noticed that Jab 2200s often give a good kick and jump on the engine mount as the first indication of ice. This is quite unlike many aero engines in that it is sudden and unannounced. I could well imagine a pilot reasonably interpreting the jump as being an engine about to shit itself.

 

 

[turboplanner]

If there is a kick and a jump on the engine mounts, then that would indicate a major overstress on the through bolts wouldn't it?