Bushbaby Down at Petit - 2019-01-27

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Re: Bushbaby Down at Petit - 2019-01-27

Unread post by Ugly Duckling » Sun Jan 27, 2019 10:00 pm

Extending the wheel tracks backwards it would appear that he came over the North South line of powerlines to the east of the field. Once down there was a fence ahead.
Options were limited.
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Re: Bushbaby Down at Petit - 2019-01-27

Unread post by Funflier » Mon Jan 28, 2019 8:18 am

Perhaps any pictures?
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Re: Bushbaby Down at Petit - 2019-01-27

Unread post by Ray W » Mon Jan 28, 2019 4:06 pm

Does anybody have the registration
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Re: Bushbaby Down at Petit - 2019-01-27

Unread post by Bundu » Mon Jan 28, 2019 6:04 pm

There was an investigation done today by myself ( Bundu Aviation - ULPower Dealer ) and Stefan ( Kitplanes for Africa) and the following conclusion and finding on the engine shutdown in flight. Master Switch ( Key Switch failure - intermittant contact ) and cut all power to the engine and fuel pumps. Wing was refueled and header tank filled. Engine and all connections checked , fuel system, software checks revelaed no power to ECU . No oil leaks, engine still full of oil ( did not leak out even inverted) Master Key switch on - Nothing. No power to pumps or ECU. Checked wiring and connections , all good and solid. Key swicth internally suspect. Identified the problem. Key Switch. After switch Identified as issue, engine started as usual. Pumps running. Conclusion. Faulty Master Key Switch / start switch ( Off On Start)
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Re: Bushbaby Down at Petit - 2019-01-27

Unread post by Dobbs » Mon Jan 28, 2019 6:24 pm

So was this the same problem the last time the same plane, and same engine resulted in an emergency landing?
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Re: Bushbaby Down at Petit - 2019-01-27

Unread post by Peregrine » Mon Jan 28, 2019 6:30 pm

What is the failure rate of that key switch? :roll:
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Re: Bushbaby Down at Petit - 2019-01-27

Unread post by Bundu » Tue Jan 29, 2019 7:37 am

we now suspect the same switch was in failure mode but very intermittant. Switch lasted 270 hrs before issues and at that stage intermittant when amp load increased ( running both fuel pumps together) increased amp load on the switch. It is STRONGLY recommended to never run aircraft master power thru a switch but rather thru a master relay ( Cole Hershee type) , even in Carb engine aircraft. On the previous incident, ambient temps were in excess of 44 C and aircraft had been standing in the sun and fuel temps were suspected to be in excess of 50C and fuel perculation was suspected. LAA has many articles on flying MOGAS / ULP automotive fuels in high ambient temps and issue of fuel perculation and vapour lock. TPS was replaced as a precaution and sent for testing. TPS did not fail. Aircraft flew another 30 hrs after this incident with no issues until sunday when switch failed to the point of not intermittant. Once power was restored to engine and pumps yesterday, everything was in order again and engine software and sensors all were working again ( had power) and engine started normally again.

So lesson learnt is go thru master relay and not a switch for master power. ULPower also recommends since about 2011 to power ECU and pumps direct from battery and not thru any master bus after relays etc. ie, ECU and pumps on own circuit direct to battery with breakers as needed ( Specified) and Amp rated switches.
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Re: Bushbaby Down at Petit - 2019-01-27

Unread post by jasv@acweb.co.za » Tue Jan 29, 2019 8:34 am

May I give my 2 bits as well?
Personally I am also scared of a relay as the solenoid of a relay is wined with very thin copper wire and they do fail more often than a switch.
What I will suggest that the master is going through a normal 10A dabble pole dabble through toggle switch and only the starter solenoid going through a key switch.
A key switch only have a sort of a slip ring on witch a pin contact is making contact with.
My plane do not have a key switch at all as the result of key switch failur.
Have a lock in older piston planes. they work in this way and for a reason. I do run the lights and non essentials through a relay, but not the engine electronics or mag switches.
If I am wrong with this Please tell me and why
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Re: Bushbaby Down at Petit - 2019-01-27

Unread post by GERMAN » Tue Jan 29, 2019 8:58 am

Picture of the switch please
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Re: Bushbaby Down at Petit - 2019-01-27

Unread post by heisan » Tue Jan 29, 2019 9:30 am

Forget switches/relays... There should be a separate switch feeding from a separate (alternator and/or battery) bus...

NTCA or not, the CAA does not accept single bus avionics (without analog backup) - how can they accept a single bus FADEC?
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Re: Bushbaby Down at Petit - 2019-01-27

Unread post by jasv@acweb.co.za » Tue Jan 29, 2019 9:39 am

https://images.homedepot-static.com/pro ... 4_1000.jpg
https://www.researchgate.net/profile/Ka ... es-the.png
You are 100% correct > the engine (electronics or electrical power) must be separate (is this the right word to use?) from the rest of the electronics.
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Re: Bushbaby Down at Petit - 2019-01-27

Unread post by Flooi » Tue Jan 29, 2019 11:37 am

Bottom line....Good engine... faulty electrical installation....
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Re: Bushbaby Down at Petit - 2019-01-27

Unread post by Volo » Tue Jan 29, 2019 12:07 pm

Battery power to sustain an aircraft engine is a non - starter !! ( pun intended)
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Re: Bushbaby Down at Petit - 2019-01-27

Unread post by Mouser » Tue Jan 29, 2019 3:05 pm

Was the switch a high quality item or possibly a knock off and was the life acceptable?
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Re: Bushbaby Down at Petit - 2019-01-27

Unread post by rare bird » Tue Jan 29, 2019 8:36 pm

jasv@acweb.co.za wrote:
Tue Jan 29, 2019 9:39 am
https://images.homedepot-static.com/pro ... 4_1000.jpg
https://www.researchgate.net/profile/Ka ... es-the.png
You are 100% correct > the engine (electronics or electrical power) must be separate (is this the right word to use?) from the rest of the electronics.
just a word of caution on using AC switches on a DC system. (I noticed the picture of the switch you posted is AC rated)

basics / fundamentals of a switch :
1. it must carry the current (ie sufficient cross sectional area of all conducting components to handle the intended current, without heat rise)
2. it must break the arc (and prevent welding the contact / or build up of carbon & oxides on the contact surfaces) (this is where AC and DC designs differ significantly)
3. obviously there must be sufficient insulation to withstand the operating voltage
4 mechanical strength in all components to ensure lifespan
5 other features eg provision for lockout, covers / guards, dust ingress (IP rating) etc

rather use a DC switch with the correct voltage and current rating
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