discussion- J230D potential electrical fire - firewall penetration

[RFguy]

On my J230D, there is a firewall penetration with no grommet.  I would always have a grommet, however read on ...

Now, this might be OK as the edges of the metal clamp  are all fairly clean and smooth and it is quite a deep long clamp, clamps over a vary long length and hence has a large surface area

 

BUT there are some sharp edges where to the two halves join . 

 

In my airplane, the EGT/CGT wires have gone through to the wire, through two lots of insulation.

AND

the unfused 10/12 AWG  TEF wire , direct to battery wires have lost quite a bit of their insulation !!! fire waiting to happen.

 

I rectified this before I flew it, however people may want to check it

I have pulled the wires back in the photo to show. You cannot see the loss of insulation on the battery wires, too hard to do with a phone camera.

This is on the STARBOARD side, IE co pilot.

 

Also there is a single photo from the OTHER side- pilot side.

 

 

[Thruster88]

Glen, If you turn the master switch off (smoke in the cockpit) is that wire still live? 

[RFguy]

yes.  its how they are wired.  it's in the schematic.

 

the penetration- I just dont know if this is typical (mfr/install)   or special  (unique) 

Edited December 21, 2020 by RFguy

[facthunter]

You must take a lot of care with "Unprotected" wiring. Even fuses don't rule out a fire. Sharp metal edges there are wrong also. "It's your life. Ralph". If you get smoke you should be able to isolate the circuits from POWER quickly and easily.. Nev

[RFguy]

either way, I suggest people to check out their aircraft BEFORE ANY FLIGHT

I am also going to dig a bit deeper on the Tasmania J170C fire (ATSB report).

I have got a MIDI fuse size setup ready for it, and a contactor in the pipeline. so it can be completely isolated. 

It's f__king insane the way it is.

 

Edited December 21, 2020 by RFguy

[Thruster88]

2 minutes ago, facthunter said:

You must take a lot of care with "Unprotected" wiring. Even fuses don't rule out a fire. Sharp metal edges there are wrong also. "It's your life. Ralph". If you get smoke you should be able to isolate the circuits from POWER quickly and easily.. 

I fly and work on certified aircraft, they have the ability to isolate all electrical power.

[facthunter]

Relay points can weld/stick too, and whatever they energise stays working, even though the switch says OFF.. I experienced a BIG engine fire that way.  Nev

Edited December 21, 2020 by facthunter

[RFguy]

Anyway, this needs to be made a safety priority. Like I said I do not know if that setup I have is unique  or factory.

Service Problem 1) firewall  wire clamp cuts wires , no conformable grommet used.  (IE unique or factory ?) 

Design Problem 2) Battery has no ability to be isolated for wires passing through the firewall into the unknown where they cannot be readily inspected.

 

Should this be driven from the manufacturer or RAaus technical manager or the regulator ?

 

I AM NOT TRYING TO CREATE A HEADACHE FOR PEOPLE HERE--  BUT I KNOW WHAT BATTERY DRIVEN ELECTRICAL FIRES DO 

 

Edited December 21, 2020 by RFguy

[RFguy]

and on relays and DC coil contactors . There is a common mistake people should know about with relay contacts and coils  and switches

 

It is common to put a diode across the relay coil to stop 'back EMF' high voltage from being generated across the coil switching contact.

This SLOWS DOWN the release of the contacts, making them more likely to not isolate. Some relays have these built in and that is bad for this sort of application. 

You need the raw coil .

Edited December 21, 2020 by RFguy

[facthunter]

Certainly not the situation that I was alluding to. An "energised" light is easy to have for critical circuits. Nev

[RFguy]

anyway, hopefully people will check out their aircraft and see what they have for the grommet/pass through

 

the wiring setup is a separate (design) issue. 

 

[RFguy]

Nev,please  tell me about your engine fire.

I just finishing reading the short stories in Macarthur Job "The old and the bold". Beleive it or not, part of my instructors syllabus (required reading material) .... great reading for me.

[onetrack]

I find it hard to believe anyone would build an aircraft with such an amateurish wiring protection setup. Either that, or someone has worked on it, and discarded any properly-installed grommet or other protection.

 

I wouldn't even allow any land-based vehicle to have a firewall wiring setup like that, it's just asking for trouble.

Edited December 21, 2020 by onetrack

[old man emu]

RFguy,

I'm being serious here. 

 

I firmly believe that it is your duty to firstly notify RAAus and the manufacturer of the situation in your aircraft. I would strongly recommend, in fact, say to do it first, contact CASA and advise them of the defect.

 

There will be some here who will exhibit their paranoia about "The Man", but if you tell CASA they will have to do something about it. RAAus and the manufacturer might sit on it. You've saved your life by identifying the problem, and no doubt, rectifying it, but what about the other poor bugger who might find him/herself dealing with an in-flight fire over inhospitable country?

[Blueadventures]

4 hours ago, RFguy said:

On my J230D, there is a firewall penetration with no grommet.  I would always have a grommet, however read on ...

Now, this might be OK as the edges of the metal clamp  are all fairly clean and smooth and it is quite a deep long clamp, clamps over a vary long length and hence has a large surface area

 

BUT there are some sharp edges where to the two halves join . 

 

In my airplane, the EGT/CGT wires have gone through to the wire, through two lots of insulation.

AND

the unfused 10/12 AWG  TEF wire , direct to battery wires have lost quite a bit of their insulation !!! fire waiting to happen.

 

I rectified this before I flew it, however people may want to check it

I have pulled the wires back in the photo to show. You cannot see the loss of insulation on the battery wires, too hard to do with a phone camera.

This is on the STARBOARD side, IE co pilot.

 

Also there is a single photo from the OTHER side- pilot side.

 

 

Just too many wires in this penetration gland. Need two and wrap the wires to prevent mechanical damage to the wire insulation. Some wrap the wires in fire sleeve through the gland and then fill with a heat resistant silicone.  No worries if done correctly.  Yours needs fixing so agree that you are getting on to it.  Your Jab a 19 or factory build?

[Thruster88]

This pilot was lucky to be only 700 feet when a fire began. Luck should not be relied on in aircraft systems. I fully support your position Glen.

 

https://www.9news.com.au/national/nsw-news-plan-on-fire-wagga-wagga/641d93d7-6822-492c-b3f0-3c5bde44af17

 

19/4/2019Forest Hill AerodromeNSWJabiruJ120CJabiru2200BAfter take-off at 700ft AGL a left turn was initiated. Immediately, there was a toxic smell and smo... 

After take-off at 700ft AGL a left turn was initiated. Immediately, there was a toxic smell and smoke in the cockpit. At this moment, with the aircraft needing to dump about 800feet of height NOW!!, The throttle was cut, the turn was pulled tight, full 'top rudder' was applied and the fuel shut-off valve was closed. A diving full slip was carried out, toward the general direction of the departure RWY strip. This was performed at a speed well above normal approach speed, in an attempt to land as quickly as possible. At or before the half way point of the approach, it became difficult to breathe and see due to smoke and flames. The aircraft was rounded out and forced onto the ground at high speed. After heavy braking, the aircraft came to rest on the centre line, facing 320 degrees, at right angles to the RWY direction, about half way along the RWY.The pilot and PAX disembarked the aircraft via the port door. The aircraft was destroyed by the fire. Suspected cause was a leakage from the fuel delivery system, within the engine bay.

[RFguy]

24 build  airframe #J766. built 2010.   TTIS 700 h.

Mechanically everywhere else- beautiful. Fantastic to fly. A  pleasure to fly .  Mechanical maintenance and books was in my opinion, gold standard. The previous owners really looked after this bird .

 

But, as I see regularly, electronics and wiring can be a weak spot in general aviation .

(I wrapped it up in Kapton tape before it flew).

 

I think the gland-clamp is supposed to work by a broad area clamp (heater hose clamp?) , so if nothing moves, and the insulation does not cold-flow (I am not sure about cold flow behaviour for TEF wire ???) then you might be lucky. There is not  much movement due to the size of the bundle, and the bundle going all different directions, so for that reason, there are probably less fires than there might be.

 

Either way, people need to check their aircraft.  I will have a discussion with a maintenance facility tomorrow. on a course of action.

 

 

Edited December 21, 2020 by RFguy

[RFguy]

there is this one

The ATSB simplistically concluded, in my opinion , the possible fire cause by blaming the battery type. I suspect hew ATSB are equally skill starved with electrical systems understandng as other orgs.

 

http://www.atsb.gov.au/publications/occurrence-briefs/2018/aviation/ab-2018-124/

 

[skippydiesel]

On 21/12/2020 at 5:47 PM, RFguy said:

On my J230D, there is a firewall penetration with no grommet.  I would always have a grommet, however read on ...

Now, this might be OK as the edges of the metal clamp  are all fairly clean and smooth and it is quite a deep long clamp, clamps over a vary long length and hence has a large surface area

 

BUT there are some sharp edges where to the two halves join . 

 

In my airplane, the EGT/CGT wires have gone through to the wire, through two lots of insulation.

AND

the unfused 10/12 AWG  TEF wire , direct to battery wires have lost quite a bit of their insulation !!! fire waiting to happen.

 

I rectified this before I flew it, however people may want to check it

I have pulled the wires back in the photo to show. You cannot see the loss of insulation on the battery wires, too hard to do with a phone camera.

This is on the STARBOARD side, IE co pilot.

 

Also there is a single photo from the OTHER side- pilot side.

 

 

RF the damage you have shown looks to me to have little to do with the firewall penetration/gland itself.

It looks like the one with obviously damaged wire/insulation and its close partner, have been subject to strong mechanical force, consistent with being pulled ridiculously hard.

The one with the peeled back insulation has been pulled against  a, none too sharp, edge,  its close  partner shows possible stretch damage.

[planedriver]

However, this is something many should all be aware of.

Not everyone is oh fay with electrics and by raising the issue which could possibly save someones bacon, I say good on you RF.

To be forewarned is to be forearmed.

Hopefully not too many around like it, but certainly worth checking.

Not easy to do once airborne.

All electrics should have provision to be isolated if the need arises.

[RFguy]

Sean you cannot see the damage to the TEF wire, either. There is a edge on the clamshell join .

 

Make no mistake . This is a very serious situation. Everyone needs to check their aircraft 

 

 

[skippydiesel]

1 hour ago, RFguy said:

Sean you cannot see the damage to the TEF wire, either. There is a edge on the clamshell join .

 

Make no mistake . This is a very serious situation. Everyone needs to check their aircraft 

 

 

I agree 110%. Just musing/speculating on the possible cause/mechanism of the damage - not intending to minimise the seriousness of the issue - no one wants an in flight fire.

[facthunter]

It is probably your worst situation. Get on the ground fast but don't muck it up when you are already on fire. Nev

[Yenn]

That grouping of wires looks poor to me. The greater the number of wires in a bundle, the greater the heating effect and also the greater the possibility of  circuits interacting with each other. You would not want to put the P leads in with CHT or EGT and the general setup is just asking for abrasion and damage. At the very least the bundle should have had some protection from mechanical damage, Just a case of very poor assembly. Was it done by the manufacturer> I doubt it.

[Blueadventures]

7 hours ago, Yenn said:

That grouping of wires looks poor to me. The greater the number of wires in a bundle, the greater the heating effect and also the greater the possibility of  circuits interacting with each other. You would not want to put the P leads in with CHT or EGT and the general setup is just asking for abrasion and damage. At the very least the bundle should have had some protection from mechanical damage, Just a case of very poor assembly. Was it done by the manufacturer> I doubt it.

It’s a factory built 24. Being J766 in 2010. Refer earlier post by RF.  The gland is excellent, just the number of wires and their fit up is poor / not good enough.