Electrical failures

[Bruce Tuncks]

I just read a report about a "battery failure" that caused a twin to crash...  there is a real downside to using fuel injection setups which need electrical power to work. I well remember Rod Stiff rejecting the idea on reliability grounds, and this sure proves him  right.

[spacesailor]

It can't be Just a battery !, as the running power comes from the alternator. 

We often ran cars without the battery,  only used a jump start to get the motor going & the positive alternator wire through a globe to earth to keep the alternator happy .

spacesailor

[facthunter]

Many aircraft alternators have to be brought onto line with a charge from the battery to excite them. If the battery is flat you cant get the alternator to charge..  There's usually a placard bear the switch(ES).  Nev

[Thruster88]

1 hour ago, Bruce Tuncks said:

I just read a report about a "battery failure" that caused a twin to crash...  there is a real downside to using fuel injection setups which need electrical power to work. I well remember Rod Stiff rejecting the idea on reliability grounds, and this sure proves him  right.

If that was the DA-42 Diamond there is more to the story. The Pilot Operating Handbook has specific instructions in regards starting the aircraft with external power. Only one engine may be started with external power and the second engine is then started using internal battery once it has charged up some. That did not happen in the accident aircraft. 

 

The Rotax 912is, 915is engines have proven themselves. Once again pilots need to understand the systems and heed the warnings of  faults in the redundant systems.  

[spacesailor]

I did say it was " jumped started " .

So there was your ' power ' to the alternator! .

No crap .

I've even had motors out of vehicles,  on the ground , 'jump started ' to show prospective ( wreaking yard ) customers,  " it works " .

With that same alternator run to earth through an old headlight , to show It works too .

spacesailor

 

[BrendAn]

5 hours ago, Bruce Tuncks said:

I just read a report about a "battery failure" that caused a twin to crash...  there is a real downside to using fuel injection setups which need electrical power to work. I well remember Rod Stiff rejecting the idea on reliability grounds, and this sure proves him  right.

how often do your efi vehicles break down.

[kgwilson]

EFI in motor vehicles is very reliable these days & almost universal & presumably why it is now in many modern piston aircraft. Aircraft engine development and innovation has always been at the extreme end of the conservative spectrum with some very sound logic. If it works & it ain't broke, don't fix it till something else turns up that is better but more importantly, as or more reliable.

[facthunter]

You don't drive piston planes in traffic and they spend most of their time in cruise at about 75% power. easy to adjust one motor or four if you have to including keeping them synchronised/ Fuel Flow meters monitor. . There's plenty of issues with electronic. It's used because it's tamper free and holds settings (till something happens) like an air leak sensor failure, programme fault .Loss of electrical power shouldn't affect the engine in a plane. When it can the electrical system is very secure and has fail safe capability like you wouldn't believe. Nev

[spacesailor]

YES BUT ,.

My poor thing is electrical FREE , not a cent for an AA battery .

Ignition is magneto,  so it has problems with HT wire replacement,  No ' carbon ' leads allowed .

Were do you buy copper HT leads .

spacesailor

[Bruce Tuncks]

Cars are not completely reliable these days. There we were, me and the missus, on the hume, in our falcon, going past wangaratta when the engine stopped! It was the fuel-pump, which is inside the fuel tank and has a cheap sparking brush-motor.  Apparently the atmosphere inside a petrol tank is too rich to ignite, please don't test this with a match.

(I since heard of a guy who got home using his model-plane peristaltic cranking  fuel-filler pump. He said it was hard work cranking on an upgrade )

The pump works at about 40 psi, the guy who replaced it was impressed that planes had 2 fuel-pumps but he reckoned that most of his customers would ignore the failure of one pump and keep on as usual.

When a similar thing happened on my old P76, I got home ok using an air-bed pump to put a few psi into the petrol-tank. I know now that putting oxygen in there is a bad idea. And I reckon there is a lot to be said for the old-fashioned carburettors.

[facthunter]

I'm NOT a fan of float carburetters on aeroplanes. That type of mixing has a lot of mixture in the inlet manifold and IF backfired  can seriously damage a motor whereas a near port or direct injector won't have that problem.  Nev

[KRviator]

If it's the one I found, they jumped both engines, but didn't allow enough time to charge the battery following engine start. As the gear is electric, when the pilot selected gear up, the current draw of the gear motor caused the buss voltage to drop below that required to power the ECU's, which killed the engines, and when the engines failed, the props auto-feathered, so the alternators went with them. The ECU's may well have recovered, but there wouldn't have been time to attempt a restart, assuming the draw of the starter motor didn't cause the same issue.

Had the checklist been followed, it wouldn't have happened, as the battery would have been at a sufficient level to withstand the transient load imposed by the gear motor. 

If I were building my RV now, I would install EFI in a heartbeat. With a small backup alternator on the vacuum pad though. Yes, the ECU may fail, but so might the throttle cable, or an oil hose, or the prop governor. Single-point failures are a dime a dozen in our aircraft, so to focus exclusively on EFI/ECU as something that may cause an accident doesn't do them the justice they now deserve in terms of engine management, (consistent) fuel delivery, leaning and economy.

[Bruce Tuncks]

A real annoyance used to be how a battery charger would not work if the battery to be charged was below some voltage. Is that something like what happened with the Diamond?

I think newer battery chargers do not have the same limitation.....  I think I have seen how they will charge up from zero volts.

[facthunter]

Cars have a limp home mode and they stay on the ground. I don't think bring up other possible failures is a logical reason to ignore one you have just added. A crude manual set up will get you home if you have a gravity feed or a way of guaranteeing some fuel flow. Engines will run on a continuous priming pump if you regulate the throttle and with a way of controlling the fuel flow roughly you can keep going if you've checked it. A spray Bar in a model aeroplane motor for example, will suck and control fuel flow. 

  Bruce some chargers wil start from dead flat but you have to buy them specifically, which is what I would always advise.  Nev

Edited April 23, 2023 by facthunter

[Bruce Tuncks]

My old falcon didn't have a limp home mode that I knew of, and I had no way to get near 40 psi to pump fuel in. I do see that the uneven supply of fuel to a Jabiru engine can be fixed with an injector. But how do you get redundancy with this?

[Bruce Tuncks]

The fuel supply was so uneven that I worked on it to the extent of putting vanes downstream of the carby before I was happy.  In my mind, the flow out of the carby was not completely atomised when it entered the inlet manifold. So I deliberately deflected some "droplets" that would have flown past the earlier cylinder offtakes into the no 1 and 2 cylinders.

[facthunter]

It's a problem with ALL carburetters that feed multiple cylinders. In most cars they just didn't worry much about it. You just used a bit more fuel. ONE carb for each cylinder works fine and they are all jetted the same but just use the drip mechanical system with GAMI injectors.  Only floods if you muck up the start procedure. Mechanical leaning.   Nev

[BrendAn]

5 hours ago, Bruce Tuncks said:

Cars are not completely reliable these days. There we were, me and the missus, on the hume, in our falcon, going past wangaratta when the engine stopped! It was the fuel-pump, which is inside the fuel tank and has a cheap sparking brush-motor.  Apparently the atmosphere inside a petrol tank is too rich to ignite, please don't test this with a match.

(I since heard of a guy who got home using his model-plane peristaltic cranking  fuel-filler pump. He said it was hard work cranking on an upgrade )

The pump works at about 40 psi, the guy who replaced it was impressed that planes had 2 fuel-pumps but he reckoned that most of his customers would ignore the failure of one pump and keep on as usual.

When a similar thing happened on my old P76, I got home ok using an air-bed pump to put a few psi into the petrol-tank. I know now that putting oxygen in there is a bad idea. And I reckon there is a lot to be said for the old-fashioned carburettors.

And how many times has the EFI let you down besides that time

[BrendAn]

54 minutes ago, Bruce Tuncks said:

My old falcon didn't have a limp home mode that I knew of, and I had no way to get near 40 psi to pump fuel in. I do see that the uneven supply of fuel to a Jabiru engine can be fixed with an injector. But how do you get redundancy with this?

EFI can still run a back up pump just like a carb.  

[BrendAn]

A friend of mine has fitted EFI to his 912. Designed and built it himself.

  Still has the bing carbs fitted until he has done enough hrs with the new system. If EFI fails he just pulls a cable and sends fuel back to the carbs . A lot better economy when it's running on injection too.

[facthunter]

Injection is a plus, for sure. I just think the mechanical system is suitable.  Aeroplane s don't need the complex parameters that cars operate to..  Sensors can fail  and do and microprocessors too..Nev

[KRviator]

35 minutes ago, facthunter said:

Injection is a plus, for sure. I just think the mechanical system is suitable.  Aeroplane s don't need the complex parameters that cars operate to..  Sensors can fail  and do and microprocessors too..Nev

I think we need to distinguish between electronic fuel injection which is just controlling fuel vs EFII that does fuel and spark dynamically, based on a pre-set table. OR, as an option, will attempt to maintain stochiometric based on closed-loop EGT. And, IMHO, aircraft don't necessarily need EFII, but most would certainly benefit from EFII, in part due to the ability to run LOP, for greater efficiency through better fuel atomisation and the ability to trim fuel to specific cylinders on the fly and get your GAMI spread to the lowest possible value.

EFII, in an aviation context, is now mature enough technology that the bugs have been worked out, by a couple of manufacturers and it's racking up thousands of hours in Experimentals around the world. If you added a PP-FS14B or a B&C 410 backup alternator on the vacuum pad, both will put out nearly 30amps at cruise RPM, which is sufficient to power your EFII system and allow the battery to run your electrics, which, if you have EFIS &  LED's like most of us these days, draw bugger-all power (3.5A for Skyview for example) so your battery would most likely outlast both your remaining  fuel and your bladder. IF you have the setup properly, your primary will put out 14.8V and carry the load throughout the flight, but if i fails, your backup will pickup instantly at 13.8V and your only indication would be the difference on the voltmeter.

[facthunter]

People have fitted it to radial engines  and they run very sweetly but it needs to be your "Thing". and have the test gear and how to tickle these systems sometimes.  Mines redundancy and  ability to trouble shoot the basics and have it still work. .  I do not like float type carburettors so I'm half way there.  Nev

[Bruce Tuncks]

They were on the early spitfires ( float carburettors ) but not the later ones.

I like the idea of a simple mechanical injector.... how does it work?

[facthunter]

Floatless 4 chamber carburettors are on DC-4's. I had NO issues with them at all in over 8,000 engine hours. Plenty of other failures though. Nev.