Jabiru ETC & Air Induction System

[sseeker]

Hi everyone just a few questions,

 

Question regarding the ETC in my schools Jabiru J160C. How exactly is the ETC wired up to the aircrafts electrical system? Some aircraft have an ETC on/off switch (which ours has) and with others the turn co-ordinator (maybe it's vacuum pumped and not electrical?) comes on with the masters. Looking through the J160 electrical wiring diagram the ETC should only function when the avionics is selected on and the ETC switch is selected on, however on many occasions I have jumped into the plane and turned the masters on to deploy flaps for inspection and the ETC has started spooling up because someone left the ETC switch on from the previous flight which is pretty easy to do because the switch is so small and under the throttle.

 

Question regarding air induction in the J160C. Just reading through the J160C manual I noticed that the Jabiru can also intake cold air which enters through a duct on the left side of the cowling (which is deffinetly there) however it says there's a flapper valve to select either hot or cold air. Our Jabiru came with the cabin heat factory mod so the lever inside the cockpit is marked "Cabin Heat" - I've never used it but I guess if I did pull it, hot air would come out right? is it a manual operation to change the induction from hot air from the muffler to cold air from outside? Or is it just a matter of pulling the cabin heat lever slightly so just cool air gets through? At the moment I just kick open the side vents to draw in a very very small amount of cool air (which manages to cool down my hand and nothing else )

 

Hope I didn't complicate that. Appreciate everyones input.

 

Thanks,

 

Andrew

 

 

[Captain]

Question regarding air induction in the J160C. Just reading through the J160C manual I noticed that the Jabiru can also intake cold air which enters through a duct on the left side of the cowling (which is deffinetly there) however it says there's a flapper valve to select either hot or cold air. Our Jabiru came with the cabin heat factory mod so the lever inside the cockpit is marked "Cabin Heat" - I've never used it but I guess if I did pull it, hot air would come out right? is it a manual operation to change the induction from hot air from the muffler to cold air from outside? Or is it just a matter of pulling the cabin heat lever slightly so just cool air gets through? At the moment I just kick open the side vents to draw in a very very small amount of cool air (which manages to cool down my hand and nothing else )

Hope I didn't complicate that. Appreciate everyones input.

 

Thanks,

 

Andrew

Andrew,

 

I can answer the above based on the way my 230 is hooked up.

 

The carb heat involves normal intake via the inlet on the left of the cowl, with a flap valve that redirects the intake from a bracket that is located at the rear of the muffler itself. That line is the same dia as the fresh cool air intake and the arrangement has the advantage that carb heat air is also taken in via the aircleaner. Some other aircraft take carb heat that bypasses the air filter.

 

This is controlled by a "Carb Heat" pull unit somewhere in the cabin.

 

The cabin heat comes from a separate smaller line with the inlet usually on the front of the cowl, then to a separate muff on the exhaust pipe and via a separete connection into the cabin.

 

This should have a "Cabin Heat" pull unit in the cabin.

 

Hope this helps.

 

Regards Geoff

 

 

[jetjr]

re ETC , some are electric and some vacuum driven

 

Electric uses a fair bit of power, so they have thier own isolator switch, Id guess if you had a electrical problem or needed every drop of battery power ie winter start, youd turn it off

 

Also gyro wears out so unless your using it you can turn it off

 

 

[sseeker]

Andrew,I can answer the above based on the way my 230 is hooked up.

 

The carb heat involves normal intake via the inlet on the left of the cowl, with a flap valve that redirects the intake from a bracket that is located at the rear of the muffler itself. That line is the same dia as the fresh cool air intake and the arrangement has the advantage that carb heat air is also taken in via the aircleaner. Some other aircraft take carb heat that bypasses the air filter.

 

This is controlled by a "Carb Heat" pull unit somewhere in the cabin.

 

The cabin heat comes from a separate smaller line with the inlet usually on the front of the cowl, then to a separate muff on the exhaust pipe and via a separete connection into the cabin.

 

This should have a "Cabin Heat" pull unit in the cabin.

 

Hope this helps.

 

Regards Geoff

Hi Geoff,

 

Yes our carby heat bypasses the filter box. But is there a way for me to intake cold air instead of hot air like the manual says?

 

re ETC , some are electric and some vacuum drivenElectric uses a fair bit of power, so they have thier own isolator switch, Id guess if you had a electrical problem or needed every drop of battery power ie winter start, youd turn it off

Also gyro wears out so unless your using it you can turn it off

Thanks, I think ours has been spiked since when I try to turn it on the red flag doesn't disappear. Time for an instrument overhaul/new instrument?

 

Regards,

 

Andrew

 

 

[jetjr]

Id be suprised if air for engine (hot or cold) bypassed filter box as its a great feature of Jabiru setup

 

The cabin heat air is completely separate to engine air, and its heated and on or off. No cold availiable. This is deliberate to prevent air from inside engine bay entering cockpit

 

I guess it would be possible to insert joiner where exhaust muff is for summer flying

 

2 side vents let in heaps of air for me except when on ground, Ive rarely got them more than 3/4 open even in hot weather.

 

I was going to add an ETC to mine but they are fairly expensive and apparantly have short lives - hence the switch I assume.

 

 

[sseeker]

A quote from the J160C pilot operating handbook,

 

"Air Induction System: The engine induction air normally enters through a NACA duct on the left side of the lower engine cowl. The air is then directed to a filter box where dust and other contaminants are removed by a replaceable paper filter element. On the outlet side of the filter box there is a flapper valve which allows the pilot to select normal cold induction air or hot induction air which is drawn through the muff fitted to the muffler. Hot air is not filtered - therefore care must be taken when choosing run up positions to minimise dust ingestion while carby heat is selected ON."

 

I was taught the same thing at school, that carburettor heat isn't filtered so care should be taken when running the engine up.

 

 

[jetjr]

In Jabirus Engine induction air IS FILTERED , just the source is changed, cold comes from NACA duct, hot comes from exhaust

 

Jabiru designed the flap valve on the INLET side of the filter box

 

Take a look

 

I just had a look, you are right regarding the manual but under "Carb heat" section 7.12.1 it says that both are filtered and this is the case

 

It does say "normally" and this is the case in most other AC.

 

Worth letting Jab know about this contradiction, unless they have changed something in the 160. They have had the same air box in all models since the very first ones I think.

 

 

[sseeker]

Sorry I'm lost are we talking about the same thing here? :hittinghead:

 

Carburettor heat isn't filtered but the cabin heat is & also the manual says the flapper valve is on the outlet side not inlet.

 

Really what I was trying to find out here is does the Jabiru have any other way of getting cold air from outside into the cockpit apart from opening the side vents (which are miniture on the 160 and don't cool much.)

 

EDIT: Ok you edited your post, no worries I'll send Jab an email. Thanks for your input. Also I have the printed copy of the 160 manual and it doesn't say anything about it being filtered under 7.12.1. My manual is from 2009.

 

 

[Jabiru Phil]

Just a word of caution re cabin heat.

 

I noted some time ago that by only partial openening of this control will leave cabin open to engine bay air.

 

I also found that opening the opposite cabin vent had better air flow to the pilot.

 

Phil.

 

 

[sseeker]

Hi Phil,

 

Thanks for sharing that info, I was considering having a go at opening it slightly to see if it'll let cool air through & luckily I didn't. When I open the side vents it usually manages to cool down my hand and not much else, I'm surprised Jabiru hasn't come up with something similar to Cessnas "Cabin Air"

 

 

[Jabiru Phil]

Hi Phil,Thanks for sharing that info, I was considering having a go at opening it slightly to see if it'll let cool air through & luckily I didn't. When I open the side vents it usually manages to cool down my hand and not much else, I'm surprised Jabiru hasn't come up with something similar to Cessnas "Cabin Air"

Just open the opposite side vent only. I think you will find a better air flow to your side.

 

Phil.

 

 

[sseeker]

Yeah I guess that'll have to do. I've been up to 5000' with the vents open and they work a charm up there. 10C cooler than it is on the ground.

 

 

[GraemeK]

We've just had round vents put in the side windows of the school Jabs - work a treat!

 

 

[sseeker]

Hi GraemeK,

 

Yeah I've seen some videos on Youtube with Jabs that have vents in the windows, deffinetly something worthwhile in the summer, especially in Bindoon.

 

 

[biggles]

The advice from 'jetjr' and 'JabiruPhil' is quite correct . The air to the carburettor is filtered , irrespective of whether carby heat is used or not and , as stated , unlike some other a/c , this has been a feature on Jabiru's from day one . And yes , the air is heated by a simple method of heat transfer from the exhaust muffler , and the flap valve is on the inlet to air filter , which then passes through the paper filter to the engine . As regards the cabin heater , and as 'Jetjr' indicated once again , the heated air comes from a different heat exchanger which is 'grubbed' high-up on the exhaust pipe . Resembling a jam tin with both ends open , and slid onto the exhaust pipe , with two openings - one for the cold air inlet , connected by hose ( scat-hose ) to an opening at the front of the lower cowl , and the other opening , connected by another hose to the on/off flap . This flap is designed to be either open or shut , although this could be defeated and air drawn from inside the engine compartment , near the firewall . Even with correct operation ie. fully pulled out , it appears possible that some minor leakage of hot air from within the engine compartment may occur due to . When open , ie. the 'Cabin Ht' knob pulled out , it is designed to allow ambient air to enter through the opening in the front of the lower cowl , pass over the exhaust pipe picking up temperature , and entering the cabin through the firewall . If the hoses are damaged , the flap is not fully open ( an 'over-centre' spring arrangement ), or the engine to have a small exhaust leak , which is not all that uncommon , it is possible for carbon monoxide gas to enter the cabin without the occupants knowing , and they will soon be off to sleep . For this reason it is good airmanship at all times , and particularly when using the cabin heater , to closely observe the CO monitor , located well within view of the pilot of course , and note any colour change , and if so , shut the heater off immediately , fully open the vents to purge the cabin air , and have the fault investigated ASAP . Of course you will have checked the 'use-by' date on the CO monitor, and you will know that it current , and therefore indicating correctly ! . I believe that it is important to always have the fresh air vents open a little , even though it may be cold outside . If the air flow through the side vents seems inadequate , check to make sure that the extraction is adequate and is not impeded . Even with 100 knots of positive pressure at the fresh air vents , there needs to be a negative pressure at the outlet to promote a flow , and most of the extraction seems to be achieved via a torturous path out through the ventral fin . I think the later A/c have a vent , similar to the side inlet vents , located beneath the A/c . On a broader note , the systems on a Jabiru , and many other A/c for that matter , are simple , and it is good airmanship to be familiar with all aspects of their operation . One day it may save your bacon !! . Have a talk to your L2 and get him/her to explain the systems , or alternatively contact many of the knowledgeable Jabiru owner/builders , who will be only to happy to help . PM me if you need .

 

Bob

 

 

[sseeker]

Hi Biggles thanks for the explanation. The reason I was arguing the point is because I'm going off what my manual says (which it appears to be wrong in this case).

 

I'll attach an image of my manual. I think the best thing in this case (as you suggested) would be to have a word with our L2 on how our Jab works.

 

 

 

[biggles]

SSeeker ,

 

The POH , of course ,should be correct but I remember mine referring to " adjustable seats " in the J160 . Of course no J160's had adjustable seats to my knowledge . It appears that the POH takes gets forgotten at the time for more important things but in the end these things sort themselves out .

 

 

[sseeker]

A copy of my manual (latest manual) can be found at: http://jabiru.net.au/Manuals/Pilot%20Operating%20Handbooks/J160-C_Section0-9_Rev3.pdf I'll speak with our CFI and L2 and if the manual turns out to be wrong I'll send Jabiru an email, it's just most aircraft don't have filtered carby heat and that's what the manual reflects that's why it's confusing me.

 

 

[slartibartfast]

I didn't trust that butterfly arrangement. When building the Cheetah with the standard Jabiru cabin heater (for the missus you understand), I welded an extension onto the engine bay facing sleeve and attached a NACA duct to source the cold air from outside the aircraft. I highly recommend this approach.

 

Regarding the CO monitor, when CO poisoned, it is my understanding that colour vision is the first thing to go. Relying on noticing a change in colour on the card type detectors seems like a bad bet. Get a good audio alerting detector. The life you save will be your own (and potentially others).

 

 

[sseeker]

Hi,

 

Our Jabiru is factory built and that's how the heater works.

 

According to the POH the carburettor heat is not filtered & the cabin heat is filtered, just thought I'd point them out so everyone's on the same page. We have a CO monitor card in the Jabiru and it's pretty out of sight (mounted on the top of the cockpit where the empty weight card, speeds etc... are placed) it's summer at the moment so the cabin heater isn't needed but winter is just around the corner and I'll be solo before then so I can see myself using the cabin heater.

 

Overall I'd rather be cold with a jumper in the cockpit rather than hot and muggy having to strip off my jumper. Regarding the audible CO device I've seen them before but I wonder if Clear Prop can order any in for a good price?

 

 

[jetjr]

.....IF you are watching your CO card, by the time it changes colour you are in serious trouble ~ 200ppm

 

If the CO leak has been going on for very long you could be sick, dizzy and having significant judgement problems

 

I imported some Electronic CO detectors and have a few left - selling @ cost $160

 

KWJ Engineering Pocket CO 300

 

These are small, have screen readout of CO ppm, loud buzzer and flashing light, alarm at 3 set levels as well as keep track of exposure vs time and alrm for dangerous levels from this too. First alarm is @ 50ppm

 

PM me if anyone would like one

 

PS I have offered these to Ian some time ago for Clear Prop but havent heard back