Electrical failures

[facthunter]

On electrical failures? Qantas Mel-Per returns to Melbourne with fumes in the cockpit which could be smelled in the cabin as well. B737. Nev

[Bruce Tuncks]

The last cockpit smoke event I have heard of was caused by a Li-Ion battery shorting out internally. I thought that they subsequently banned such batteries.

 

[aro]

On 21/04/2023 at 9:58 PM, kgwilson said:

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.

Look at the number of cars vs. the number of aircraft. The reality is that if car engines were as unreliable as piston aero engines, there would be cars broken down everywhere by the side of the road. The CASA Jabiru engine failure study quoted a failure rate for Continental and Lycoming i.e. the "good" engines at 1 per 10,000 hours. Car manufacturers can't afford anywhere near the level of unreliability that aircraft engines get away with. The publicity would kill the manufacturer.

 

Car manufacturers need reliability. If there's a way to cause a failure they need to know about it. They put their engines through tests that an aircraft engine would be unlikely to survive. Aircraft engine manufacturers just can't afford the R&D costs that go into a modern car engine. They don't have the numbers.

[Bruce Tuncks]

 ARO, your math says that a plane  engine has a failure once in a MILLION km, if flown at 100km/hr.

I reckon my cars have been less reliable than this.

Edited April 23, 2023 by Bruce Tuncks

[spacesailor]

Cars are a lot like People .

They have a Finite life . keep them running & they last lots longer .

Lots of tender loving care helps both  .

spacesailor

[aro]

38 minutes ago, Bruce Tuncks said:

ARO, your math says that a plane  engine has a failure once in a MILLION km, if flown at 100km/hr.

I don't know whether per km is the best way to measure reliability, particularly since car reliability probably improves e.g. with more highway km at 100km/h. Would you say the same engine is more reliable in a fast aircraft than a slow one?

 

Even so, 1 in 10,000 hours is probably more like 1 in 5 aircraft experiencing a failure before 2000 hour TBO, rather than 10,000 hours on 1 engine. So using your calculation it's probably equivalent to 1 in 5 engines failing before 200,000km, which I think *would* be bad enough to seriously embarrass a car manufacturer. Any failures are also more likely to be maintenance related, e.g. not changing oil, coolant, hoses etc. in a 10+ year old engine rather than the engine itself.

 

I am really referring to car engines from the last 10-20 years - not older engines e.g. from the 70s and 80s which were definitely less reliable.

[KRviator]

49 minutes ago, Bruce Tuncks said:

 ARO, your math says that a plane  engine has a failure once in a MILLION km, if flown at 100km/hr.

I reckon my cars have been less reliable than this.

Should buy the right car then! 😛

I had an old (1993) Patrol with the 4.2 diesel. Brought it from the father in law of a mate with about 250,000 on it. Did nothing to it mechanically except change the oils & filters, replaced the alternator and the seal on the fuel pump. Mostly highway driving initially, then medium (30km or so) distances around town. Drove it for about 50,000km with no speedo after the correction box failed. Fixed that, then sold it to a mate with 550,000km indicated on it (worst thing I ever did), and he's still driving it around 5 years later. If you assume an average speed of 40km/h, that car has over 16,000hours run time, and probably closer to 18-20 if you factor idle time as well with nothing done to the engine except consumables. No rings. No pistons, no gaskets, no new head.

Though in saying that, it did need me to pull over twice. Once was the throttle cable came out of the bracket after I'd forgetting to tighten the jam nut. Did it up finger tight, forgot to tighten it once I got back home and never had it happen again. And the plug fur the fuel solenoid must've wiggled lose, the engine just stopped dead. Coasted to the emergency bay, had a look, unplugged and reconnected it and she fired straight up and never had the same problem.

It was slow as all get-out, but you would get there. Wherever you were going.

[kgwilson]

The thing is that you are talking chalk & cheese here.

 

Car engines are heavy & rarely run at high RPM and if something stops you pull over & ring NRMA. New innovations get thousands if not millions of hours testing before they are unleashed in to production models. The scale of production is thousands of times greater than for aero engines. And guess what there are still problems. We constantly hear of recalls due to a fault showing up. Start using them in a racing environment & reliability goes through the floor.

 

Aircraft reciprocating piston engines are built light for a good reason, so the aircraft can get off the ground. They have another dimension to deal with depleting air density often with very large temperature variations very quickly. They are run at full power not long after startup every time and then at around 75% of power for most of the time.

 

[aro]

39 minutes ago, kgwilson said:

New innovations get thousands if not millions of hours testing before they are unleashed in to production models. The scale of production is thousands of times greater than for aero engines.

That's my point, aircraft engines don't have nearly the same development resources available. And given the scale of production, car manufacturers can't afford to have anything like the failure rate that we see in aircraft engines.

43 minutes ago, kgwilson said:

And guess what there are still problems. We constantly hear of recalls due to a fault showing up.

There are still problems - but massively fewer than in aircraft engines.

43 minutes ago, kgwilson said:

They are run at full power not long after startup every time and then at around 75% of power for most of the time.

Compare the hp/capacity for an aircraft engine vs. car engine. 100% power in e.g. a Lycoming is relatively low for its capacity.

Car engines in development are tested at 100% power for hundreds of hours continuously. It's just a myth that they can't do that. Problems in auto engine conversions for aircraft are most likely due to the parts that are different or don't exist in a car e.g. cooling, PSRU. Auto manufacturers also spend millions validating the cooling system - no-one can match that in an auto conversion.

 

There have been huge advances in engine reliability in the last few decades, but aircraft engines have hardly changed. That is because of the cost of development, not because they are more advanced than auto engines.

[Bruce Tuncks]

I like your arguments ARO, but if you are correct then there would be more auto conversion engines in use in planes, maybe an enterprising type will fit one to a kit plane and do it well.

In the meantime, I reckon KG has a good argument in that they are different beasts. He didn't even mention the rpm deal. I like my Jabiru with no gearbox, but auto engines run too fast for a direct drive. Yes I know that the Rotax has a gearbox.

There was an auto conversion I have seen where a V8 was being used in a Pawnee tug plane. The reduction drive was a short toothed belt and it was destroying itself against a flanged pulley wheel. 

[facthunter]

So why is the sky not full of auto engine conversions then? . Aero engines are as specialised as race engines in their own way. Car engines are "loafing" most ot the time.. Nev

[aro]

The problem with auto conversions is all the other bits that you have to add and the things that are different to a car installation. Auto manufacturers probably spend tens of millions validating the cooling system, gearbox etc.

 

An auto conversion needs:

- a PSRU

- a custom cooling system

- maybe e.g. the sump needs to be modified to be sure of oil supply in different attitudes. Particularly if the engine is installed backwards relative to a car installation - climb power becomes the equivalent of full power *down* a steep hill - not something that cars commonly do

 

The type of people who do auto conversions also like to make their own tweaks, maybe to increase power e.g. based on race tuning or increase perceived reliability.

 

None of these changes get the type of testing that the car installation gets. It's not the engine that is the problem - it's the changes you need to make to put it in an aircraft, and the cost to do that development properly. Car manufacturers can afford to spend the cost - aircraft manufacturers can't. You just can't recoup the costs with the size of the market.

[facthunter]

A suitable aero engine is like a good airframe. No extra weight anywhere. Top race engines have  a design life of a few thousand KM's only. Heavy engines are in Trawlers. IF you want a good aero engine build it from scratch and design it as one. UL have done this but you can count success on one hand if you want to Instal and forget. The Wright J series motor was run flat out for 50 continuous hours in the late 20's. How many engines would meet that today and you have to consider the condition they are used in. Lots of idle time Too. Nev

[spacesailor]

LOTS ! Of ' V W ' convertions in planes & direct drive .

One  ' Spitfire ' with 3.2 litre V 6  Isuzu motor ( Holden Jackaroo )

SUBARU are flying too . And a ' Camic ' in a box for sale at Newcastle .

spacesailor

[BrendAn]

On 23/04/2023 at 12:31 PM, Bruce Tuncks said:

58 minutes ago, spacesailor said:

LOTS ! Of ' V W ' convertions in planes & direct drive .

One  ' Spitfire ' with 3.2 litre V 6  Isuzu motor ( Holden Jackaroo )

SUBARU are flying too . And a ' Camic ' in a box for sale at Newcastle .

spacesailor

 

Aren't jabirus made of auto parts. Holden pistons and rods. Gray motor dissy caps. Honda mower coils. Honda car starter.

[facthunter]

 They ALWAYS made their own conrods out of the same billet material the cylinders are made of. Earlier motors use a Holden V6 piston on max oversize. That piston to me was always crap but there could have been other car pistons that would have been better. Making the right piston is necessary if you can't find a suitable  readily available  one but again it's NOT rocket science.  Nev

[BrendAn]

9 minutes ago, facthunter said:

 They ALWAYS made their own conrods out of the same billet material the cylinders are made of. Earlier motors use a Holden V6 piston on max oversize. That piston to me was always crap but there could have been other car pistons that would have been better. Making the right piston is necessary if you can't find a suitable  readily available  one but again it's NOT rocket science.  Nev

What did the valves come from.

[facthunter]

No idea. Plenty of people make valves. In normal ops are they a particular problem? I've always preferred Non Hydraulic lifters with rollers where you know what's changing (if it is). Nev

[turboplanner]

56 minutes ago, BrendAn said:

Aren't jabirus made of auto parts. Holden pistons and rods. Gray motor dissy caps. Honda mower coils. Honda car starter.

The difference is in the engine design. Car engines are designed for intermittant power applications, water cooling of the engine and other accessories, construction designed for a lot of accessories and maximum power achieved by rpm setting.

 

Aircraft engines are designed for constant power applications, preferably air cooing to save mass, fewer and smaller accessories for lighter mass, and cruise power achieved by a higher percentage of torque and a lot less multiplying rpm.

 

The design starts with the crankshaft, and most of the auto failures have been through trying to get prop-suitable rpm by using reductions which were poorly designed or trying to get constant power to work in an engine not designed for it.

 

 

 

 

[BrendAn]

1 hour ago, facthunter said:

No idea. Plenty of people make valves. In normal ops are they a particular problem? I've always preferred Non Hydraulic lifters with rollers where you know what's changing (if it is). Nev

I would think the valves are from an auto engine. Wouldn't be much point designing their own.

[turboplanner]

17 minutes ago, BrendAn said:

I would think the valves are from an auto engine. Wouldn't be much point designing their own.

Why not? a constant power application has hotter chambers.

[BrendAn]

19 minutes ago, turboplanner said:

Why not? a constant power application has hotter chambers.i

Just can't imagine jabiru making their own when they could just source ready made valves. Not that I really care. I have a rotax so It doesn't affect me anyway.

[turboplanner]

36 minutes ago, BrendAn said:

Just can't imagine jabiru making their own when they could just source ready made valves. Not that I really care. I have a rotax so It doesn't affect me anyway.

Where would they get ready made valves from an auto supplier for a constant power application when they are designed for intermittant power application?

Same thing applies in trucks; there are intermittent power engined trucks for metro operations and constant power engined trucks for line haul.

[kgwilson]

Jabiru doesn't make many of its own parts other than what Ian Bent (Camit) used to make with the CNC gear he had which jabiru bought when Ian went in to receivership. Like most manufacturers these days they purchase components to their specification from specialist suppliers around the world. A lot of these are in China of course.

 

A friend ordered a new 3300A engine after his old one suffered a major prop strike as it was cheaper than a strip & repair & also 2 generations newer. The problem was none were available for several months last year as quite a few components were in short supply after nothing was made for ages during Covid. Eventually things started trickling in again and the last major component was the crankshaft & he finally got the new engine about 6 months after the order. The days of Holden, Honda and Kubota parts etc are long gone.

 

Jabiru has produced close to 8,000 engines to date split fairly evenly between the 4 & 6 cylinder versions.

Edited April 24, 2023 by kgwilson

[facthunter]

Just as an example of what's available at the top end google G&S Valves uk. Nev