Bushbaby Down at Petit - 2019-01-27

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

Unread post by GERMAN » Wed Jan 30, 2019 7:03 am

On some of those switches the part where the screw holds the wire or terminal is popriveted to the contacts inside the switch which vibrates loose and causes problems
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Re: Bushbaby Down at Petit - 2019-01-27

Unread post by Lood » Wed Jan 30, 2019 7:18 am

Can't one use the same switch/breaker and wiring/bus system, as used on TCA? It has obviously proved itself, over many years, to be fairly fail safe and most seem to last just about forever.
I have no experience on NTCA or Rotax, UL, etc engines, so not sure if the above is compatible?
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Re: Bushbaby Down at Petit - 2019-01-27

Unread post by phantom4 » Wed Jan 30, 2019 9:40 am

jasv@acweb.co.za wrote:
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 Bundu » Fri Feb 01, 2019 12:13 pm

I agree with you. Relays another failure point, but where do you stop?
What we do when we install ULPower engines and our customers that we assisted with installations ( 12 now), we use Honeywell Milspec Latching switches rated 20 amp and they are DPDT switches. Expesnive for sure at about R700 each but only 2 needed.
The wiring loom supplied and already on the engine and all connectors done for engine and ECU side. Install engine. Mount ECU. Plug engine harness in. Cannon Milspec connector. 2nd loom also supplied and also with cannon connectors has wire coming out of it colour coded and extremely simple to actually wire. Red bundle to 20 amp rated switch on panel, then Breaker then direct to battery Pos. Similalry black bundle direct to Batter NEG. Thats it. That is all the power for everything engine related. There are more wires coming out of the loom that connect to RDAC type for sensors for EFIS or Gauges, Mag switches ( 3 core screened with 1 wire common to inputs of each Coil/Mag swicth and 2nd and 3rd wire to output of the swicthes) thats Ignition control sorted. Engine standard one fuel pump and advised to be relay controlled by ECU ( again wires already there from ECU , you must just terminate on solenoid control circuit) and a swicth to override relay. We typically advise going 2 fuel pumps. When 2 installed, Primary is relay controlled and Aux is direct control. Both pumps power direct from battery again with Breakers. On the previous generation ECU ( Black) was a different casing and fittings connectors on ECU side. Since 2014 has been new inhouse ECU box with cannon connectors. Typically again a DPDT On-ON swicth so that both pumps cannot run at same time, even though pumps in Parallel. Each pump has own fuel filter as well. All wiring on engine side is Tefzel, twisted pair screened etc as needed. ECU has passed certification in Europe to very high standard for RMI/EMI etc interference etc. On the 4 cylinder engines we have as standard a 30 Amp alternator with option for 50 amp or 2 x 15 Amp alternators. We recommend using a 68000mF 64V Capacitor over the battery. Has 2 benefits. Quietens electric system as usual ( not that we have found electrics to be noisy from the engine as yet) and most importantly, if the battery fails internally, the voltage regulators will not shut voltage flow to battery as Cap now acts as battery and voltage regulators still allow power thru. Without the Capacitor the Regulator will close the taps ( even if alternator is still producing power) and you have electric failure of complete system again.
Main aircraft power should never ever run from a panel switch. Every aircraft should at least have a Relay installed and Master Switch activates the relay and then powers system busses. Switch is usually Negative swicthed to relay so no problem with arcing etc of switch interals etc. ( Remember to install the DIODE as per installation instructions of the relay!)
OK so now you have a seperate " engine Bus" and master aircraft circuit. Its easy to forget to swicth Engine "bus " off. The ECU has wiring output for 2 LED or Globes on the panel that shows a Low voltage caution ( activates at 12.5 volts ) so usually LED swicthes on when engine "bus" is swicthed on, thereby showing that there is power on on the system. 2nd light shows if there is a sensor failure of the engine. What a few of mys customers have done as well is install a small Voltage display ( LCD) that gets wired with the ECU circuit and it displays voltage seen by ECU. Very handy! No need to switch on EFIS etc to see voltage of plane. And of course if the voltage LCD displays a voltage, Engine ECU cicuit is live. Similarly it is advised to install LED's for each pump showing which is running and again, its a light on the panel showing power is on somewhere ( Fuel pump circuit) To be relaised also is that there has been growth in the ECu outputs over time ( LED lights for Voltage and sensor failure was a change from old style Black ECu to new Red style) and end 2018 Fuel pressure and oil Pressure senders are now standard on engine and data from ECU. Also, ECU now records last 15 minutes of engine run in a loop style for engine diagnostics , fault tracking etc. Previously you had to install your own Oil and Fuel pressure senders and wire to gauges / efis etc. Now Canbus output to instruments..

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

Unread post by jasv@acweb.co.za » Fri Feb 01, 2019 1:26 pm

Therefor the engine running is depended on the battery ? and the electrolytic will not supply voltage long enough to keep the alternator energised, specially if a short develop in the battery. don't they have a separate power sauce in the engine for running the fuel injection system?
there is a lot of pros & cons with each method and I feel the safest is the proven ones. My ching (geld) was made with electronics , analogue and digital, LEO , FLURR , and high end communication equipment and still I like a mechanical system. CDI or electronic ignitions as well as fuel injection use solid state (diodes , caps IC,S trannies fet,s )with no PREDICTAL life span (5SEC. 5MIN.5DAYS 5 YEARS.) Cars ok, but you can not park there on top. But I feel we are going off the topic.
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Re: Bushbaby Down at Petit - 2019-01-27

Unread post by Bundu » Thu Feb 07, 2019 2:14 pm

There is always 2nd battery option... we have wiring for that as well. Advent of lithium battery development makes it more and more feasible due to weights coming down...
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Re: Bushbaby Down at Petit - 2019-01-27

Unread post by dollar » Fri Feb 08, 2019 12:27 am

Very interesting stuff.

It all boils down to single points of failure vs redundancy? Found in ships, aeries, trains and even tower cranes!

You reduce the single points of failure by adding redundancy. Two mags instead of one, two engines, two pumps, two or 4 hydraulic circuit, Multiple electrical circuits etc.

Problem is that you cant duplicate everything so you have to do a bit of a head scratch as to whats likely to fail. Just about anything that can fail will fail at some point. So everything has a design life - supposedly. Vac pumps will last X hours, Engines Y hours, Air frames Z hours. Easy with the big bits but gets tricky with the component parts. Electronics as previously mentioned is a bit of challenge. A heat or voltage stressed IC may last a few minutes or days. But stressed electronics generally fail prematurely. Big snag if its in your ECU. Fortunately its entirely possible to build high levels of redundancy into things like ECU's. Not sure if this is done but its certainly practically possible. The components within one of these "black boxes" are only worth a few Rand.

A small (light) back up battery is also a good idea. Reduces the chances of total electrical failure doesn't it? A multiple electrical bus is also worthwhile but this starts getting costly and difficult to maintain. It may not be worth the complexity. Rather focus on the quality of the bus - wire, connectors and routing.

Bottom line I guess is that you can only have a level of redundancy in an aerie, to much and it simply wont fly!

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