Aircraft engines are supposed to be simple..

RyanB

RyanB

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Answer this, after reading many accidents of engine failures, fires etc. why do these airplane engines fail much more often than it seems car engines do. You dont hear of car engines "throwing rods" and what not? Whats up with this?
 
Most of our aircraft engines were designed in the 50's. Most of our car engines are post Y2K and reflect the latest in piston engine technology. Also most airplane engines are run nearly wide open whereas we typically cruise in our cars at 1/3 of redline.
 
Ryanb said:
True, just doesnt seem like i hear about engine failures in cars.
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That is exactly what he said. :D

Also not all engine failures are mechanical problems. Most are pilot-induced fuel starvation.
 
MickYoumans said:
Most of our aircraft engines were designed in the 50's. Most of our car engines are post Y2K and reflect the latest in piston engine technology. Also most airplane engines are run nearly wide open whereas we typically cruise in our cars at 1/3 of redline.
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But aren't these engines designed to run at those RPM's? I wonder how things would change if these engines were re-designed.
 
Maybe they don't throw rods, but car engines fail plenty.

I am on another board that is frequented by a lot of auto mechanics and people who like to work on cars in their garages.

There are - literally - hundreds of stories on that board about engine failures.
 
Aircraft engines do not fail much more often then car engines. You just don't hear about it because if you throw a rod in your car you pull over and call a tow truck. Throw a rod in your plane @ 5000 AGL and your looking at a possible life threatening situation.

The ensuing carnage will result in media coverage and mass hysteria about the safety of GA to the masses. :yikes:

Nobody cares if your car breaks down. :dunno:
 
Ryanb said:
But aren't these engines designed to run at those RPM's? I wonder how things would change if these engines were re-designed.
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Take a typical piston engine (O-320). It has a 2000hr TBO, most planes it is in cruise +/-100kts, and it runs at 65-75% power all day. In car terms, this would be like running a family sedan at 4500rpm for 200,000 miles and deep-servicing it once a decade.

See the problem?
 
warthog1984 said:
Take a typical piston engine (O-320). It has a 2000hr TBO, most planes it is in cruise +/-100kts, and it runs at 65-75% power all day. In car terms, this would be like running a family sedan at 4500rpm for 200,000 miles and deep-servicing it once a decade.

See the problem?
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My car has gone 225,000 miles without catastrophic mechanical failures, assuming at an average 40 miles per hour that's about 5,500 hours run time not including all the hours spent idling and not moving.

225,000 miles most (98% I'd guess)of which were at very low engine power settings over 12 years.
 
I hear more about bikers destroying high tech toys in motorcycles than cars
 
bnt83 said:
My car has gone 225,000 miles without catastrophic mechanical failures, assuming at an average 40 miles per hour that's about 5,500 hours run time not including all the hours spent idling and not moving.

225,000 miles most (98% I'd guess)of which were at very low engine power settings over 12 years.
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At 40mph, your car was loafing at 2000-2500rpm. Now if you did 70mph up mountain each day, then you'd be closer.

Remember, TBO is not a half-life to catastrophic failure, it is a target figure for the fleet- almost every engine should make TBO +/- standard deviation.
 
It's like the old canard...

"Why does it seem cars are so prone to stalling on railroad tracks?"

In fact, cars stall everywhere.

You only read about it when they stall on the railroad tracks!
 
Ryanb said:
Answer this, after reading many accidents of engine failures, fires etc.
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Actually engine failures make up a tiny percentage of GA aircraft accidents and like someone above correctly pointed out such power loss is often due to fuel starvation or clogged fuel line or improper fuel, etc and have nothing to do with the engine itself. Engine failure doesn't even make into top 10 accident causes in GA.
 
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I still don't understand how running at 2600 RPM is so stressful on an airplane engine and my car will do 6500. both are metal pistons in metal cylinders separated by a thin layer of oil. I could drive across the state in my car at 2600 RPM without a care in the world

^all that being said, I know very little about plane engines. I know a lot about the ford 289 V8 as I had one for awhile. MAybe there are vast differences. I don't know em though.
 
In all the driving I've done, many years I drove 40 thousand miles, I never had an engine in my car quit that I remember. In those same years, 2 aircraft engines quit due to lousy mechanics working on them. I've never driven a car as hard as the airplanes I've flown simply by taking off at full throttle, hot weather, air cooled cylinders getting hot on the ground, etc. over the years I've checked the faa monthly accident reports and found many aircraft engines actually do quit, especially on takeoff. ( some due to idiots running out of gas) I think a lot of it is due to an old fleet, many engines over 50 years old, etc. I rarely see a car beside the road that it isn't a flat tire. Most cars run on and on. Add to this pilots sitting on the ground running an air cooled engine a very long time doing things I know not of , usually with others waiting to take off. Very hard on an air cooled engine. I was taught to get the temp off the peg, taxi into position and get off the ground as rapidly as possible using common sense of course regarding temperature.
 
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How many times does a piston go up and down in your car at 1300 rpm in an hour versus an aircraft engine at 2600 rpm . Try hooking a large trailer behind your car and then run it at 2600 rpm for a year or two every time you drive it and see what kind of problems develop. Having scattered a few car engines over the years I can attest that sometimes they come apart with no warning in extreemly violent ways even with the oil changed every three thousand miles since new. Now some of the ones that blew on me may have been somehow connected to my right foot as a factor in their destruction. Besides if car engines did not fail we would have no tow trucks.
 
Part of me thinks that the GA world is overdue for a 5000 hour turbonormalised water-cooled injected ICE (or, at the very least, an engine from Goldwing), then the other part just wants to keep it stupid simple. I guess if it were possible to have something like this, there would be one already, and we'd be flying them by now. As we are witnessing the breakthroughs of hybrid/battery tech in cars, we are much more likely to see electricity powered GA planes than ones using car based engines. The cutting edge has moved beyond ICE...
 
airplane engines are simple. Chainsaw engines are simpler. Many car engines are pretty complex. Really, airplane engines are amazingly reliable. but what is really remarkable is how reliable car engines are given the high level of complexity of many of them.

That said, all vehicles break down. I see cars on the side of the road all the time. I've certainly walked away from my car on the side of the road more times than I've walked away from my airplane in a cornfield.
 
Air cooled engines are not the way to go. The cooling is not efficient and wear is greater than liquid cooled. In addition aircraft engines, by design, are as light as possible compared to a car engine. Porsche was on the verge of dropping an air cooled engine years ago due to the problems they encountered trying to cool their engines which are basically an aircraft , horizontally opposed engine. Finally they wised up and liquid cooled it in 1999. As for complexity, peek at an engine on a machen super star or a newer bonanza. Pretty complex to me and packed into a very small hard to cool space.
 
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It sure made sense to North American, and the P 51 has been a pretty decent airplane. One of the best.
 
I think in motorcycling world the tide has turned toward water cooling, everywhere, including motoGP long time since. The weight, gained by addition of a cooling system was offset by using lighter cylinder heads. Performance went up as well, with higher specific (bhp/lb) output of wc engine.
 
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Phillip said:
I think in motorcycling world the tide has turned toward water cooling, everywhere, including motoGP long time since. The weight, gained by addition of a cooling system was offset by using lighter cylinder heads. Performance went up as well, with higher specific (bhp/lb) output of wc engine.
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That is very true! It took the japs to set us straight on motorcycle engines. I owned a shadow and a kaw ZL 1000. Both water cooled and smooth nice bikes.
 
Jimmy cooper said:
It sure made sense to North American, and the P 51 has been a pretty decent airplane. One of the best.
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And those engines didn't last very long, either. Certainly didn't have 2000 hour TBOs. Might have made 400 hours.


Dan
 
Ryanb said:
Answer this, after reading many accidents of engine failures, fires etc. why do these airplane engines fail much more often than it seems car engines do. You dont hear of car engines "throwing rods" and what not? Whats up with this?
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Aircraft engines very seldom fail due to mechanical destruction like throwing a rod. Normally, they quit because of (A) carb icing, (c) fuel starvation, (C) ignition failures (magnetos that weren't maintained), and (D) oil starvation.

Carb ice kills engines because too many pilots don't understand carb icing. Fuel starvation happens because the pilot didn't buy fuel, or tried to run on an empty tank, or didn't get the water out, or had ancient hoses in the system that crumbled internally and plugged up. Magnetos need periodic internal inspections. They often don't get it.

Oil starvation causes seizure or "throwing a rod." And that's because the pilot didn't put oil in it, or an old hose broke in flight and blew all the oil overboard.

Some engines have mechanical trouble becauase they sit for 99.98% of the year. Moisture, sun, heat, cold, age all take their toll. You wouldn't believe the hardened fuel and oil hoses I find in some airplanes. Found one the other day, a fuel hose between the strainer and carb, that had been made in 1974. It was as hard as wood, and would eventually have torn loose at the fittings because it couldn't flex. How many airplanes are running around like that? The FAA and Transport Canada recommend a five-year replacement cycle on hoses. 40 years is stretching it a bit.

Dan
 
Your wrong. Jap engines are very well balanced and go forever if maintained and not abused. Both of my motorcycles ran extremely well for a long time and were sold in excellent condition. Same with Honda and Toyota cars of which I've owned several.
 
Jimmy cooper said:
It sure made sense to North American, and the P 51 has been a pretty decent airplane. One of the best.
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according to my grandfather, the P51 was only preferred when sending a picture to a girl pack home. When people were shooting at him he wanted to be in a P47
 
Dan Thomas said:
And those engines didn't last very long, either. Certainly didn't have 2000 hour TBOs. Might have made 400 hours.


Dan
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They were flown in combat and run very hard from day one. No comparison to an everyday hamburger flight. The rolls engine was and is a fantastic engine and was constantly changed and upgraded during WW 2. When raced they tend to fail as they've been tweeked to their limit then run full bore. Lousy comparison.
 
The bottom line is they are ancient designs in the combustion engine world. The IO-520 in my bird is a 1963 design which was great and cutting edge 50 years ago. Just drop a GM V8 from 1963 into your 2014 2500 and show that to a few people to see how they look at you. The first thing that would help these motors out a ton is changing the induction system and going with direct injection. This would increase fuel efficiency and power output greatly. At the end of the day we are running old technology in our birds that was out dated 40 years ago.
 
JHW said:
according to my grandfather, the P51 was only preferred when sending a picture to a girl pack home. When people were shooting at him he wanted to be in a P47
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Only because the p 51 was liquid cooled and a bullet in the cooling system would bring it down. P47 was radial and air cooled. Also a great aircraft but not without its own problems.
 
I've worked on a few engines in my time. Aircraft engines are bone simple. They minimize moving parts, and the parts that do move are vastly overbuilt for the power provided, because the safety margins and duty cycle require it.

A few weeks ago, I was working on a Ferrari V8. It has 32 valves and all that goes with it, four cams, two drive belts, two ignition systems(for performance, not redundancy), and the fuel injection would set your hair on fire. Compared to a 6cyl Conti engine with a carb and pushrod controlled valves.
 
SixPapaCharlie said:
I still don't understand how running at 2600 RPM is so stressful on an airplane engine and my car will do 6500. both are metal pistons in metal cylinders separated by a thin layer of oil. I could drive across the state in my car at 2600 RPM without a care in the world

^all that being said, I know very little about plane engines. I know a lot about the ford 289 V8 as I had one for awhile. MAybe there are vast differences. I don't know em though.
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In a nutshell, the difference is in the length of connecting rods and pushrods.

If you have a car that will do 6500 RPM, it probably doesn't even have pushrods.
 
olasek said:
Actually engine failures make up a tiny percentage of GA aircraft accidents and like someone above correctly pointed out such power loss is often due to fuel starvation or clogged fuel line or improper fuel, etc and have nothing to do with the engine itself. Engine failure doesn't even make into top 10 accident causes in GA.
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I've got a ten-year database of Cessna 172 and Cessna 210 accidents, which I use as a Control Group for my homebuilt accident analyses.

About 13% of the accidents were due to mechanical issues, including those related to faulty maintenance. Roughly 24% of all their accidents involved engine failures, but this include fuel starvation/exhaustion/contamination, carb ice, etc. Roughly 12% of the accidents involved engine failure through mechanical issues. About 5% more were cases where the engine quit but the post-accident investigation was unable to determine why.

As others have said, aircraft engine failures get more attention because they're more likely to involve accidents than automobile accidents.

Over ~45 years, I've had a number of auto-engine failures. Points got messed up, rocker arm fell off, computers went on the fritz, ignition system failures, shorts and fires in the engine compartment, and, yes, fuel exhaustion. Haven't had any in the past ~15 years, probably mostly due to being able to afford newer cars and the improvement in system reliability.

Had one aircraft engine failure; fuel contamination. Number of hours don't come anywhere close, of course.

Ron Wanttaja
 
SixPapaCharlie said:
I still don't understand how running at 2600 RPM is so stressful on an airplane engine and my car will do 6500. both are metal pistons in metal cylinders separated by a thin layer of oil. I could drive across the state in my car at 2600 RPM without a care in the world

^all that being said, I know very little about plane engines. I know a lot about the ford 289 V8 as I had one for awhile. MAybe there are vast differences. I don't know em though.
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RPM is not what kills engines, load is. Cars very rarely see any real load, and almost never for more than a couple minutes at a time. Climbing steep hills, hard acceleration, trucks trying to get a big trailer moving, and that's about it. When you're cruising down the freeway at 80 you're barely on the gas, and using about 15-20% power to maintain that speed. An airplane engine on the other hand is expected to run at 70-75% load for hours and hours on end. This is the equivalent of taking your 6000rpm rated car, and holding it wide open while climbing a hill so steep that you can only maintain 5000rpm and just keeping it there for hours. Trust me, if you could find that hill your car wouldn't survive very long. The only time you actually see those kind of conditions is towing trailers in the mountains, and that's very well known to overheat engines and kill transmissions. I'm betting if you've ever driven any mountain pass you've seen a truck or 2 on the side of the road with steam coming out.

People have been trying to get the GenIII chevy LS engines aircraft certified for a long time, and so far nobody can get them to survive long enough to pass the certification tests. These are motors that we regularly tune to 800+ horsepower and run wide open in heavy desert race trucks in 100 degree heat for 1000 race miles (which is similar to probably 50,000 road miles) at a time and they survive that yet they cant seem to build one that will survive typical airplane use. That says a lot.
 
Ok I just decided to be a total nerd and do a little testing to show what I'm talking about in regards to load factor. I recently picked up a little bluetooth OBDII dongle that plugs into the diagnostic port on any newer car. It sends all sorts of data from the cars computer to another device, in this case my phone running an app called Torque. It'll give you any error codes that might be turning on the check engine light, but will also give you real time data on all sorts of things, including engine water temp, intake air temp, ambient temp, rpm, speed, O2 sensor readings, throttle position, load %, and much more.

For this test I set up the screen to show me a graph of the Load %, speed, RPM, and throttle position. The car being used is a 2006 VW GTi with a 2.0l turbocharged 4cyl, 6500rpm redline. I then drove from my house and got on Interstate 15, accelerated at full throttle up the on ramp to around 85mph, then slowed to 70mph. I then set the cruise control since it's a lot smoother at applying throttle than my foot. Since I'm in Southern California there's no such thing as a straight and level freeway so I was going up and down some gentle hills, but I think the data is still worthwhile.

So here's what I got. I was only able to hit 100% load while full throttle accelerating on an uphill on-ramp above 3500rpm, and I was only able to keep it there for a couple seconds at a time before hitting redline and needing to shift (or slow down). Load was never above 75% for more than 10 seconds at a time, and only when accelerating with more than 60% throttle opening. When cruising at 70mph the load varied between 25-35% depending on if I was going up or down hill and throttle position of around 25-30%. This was in 6th gear at about 2650rpm. Interesting thing happened when I shifted down to 4th gear. The load % went down by roughly 7% at 4100rpm. I assume this is because that's the rpm range where this engine makes most of it's power, and also spools the turbo, which means it requires less load for the same amount of power output. Coming back home I decided to use a bit of engine braking on the off-ramp and saw loads as low as 11% at ~4000rpm. Nowhere did I see the kinds of loads that we typically cruise at in an aircraft, except for very short bursts of acceleration.

A couple other interesting things to note. Idling in my driveway showed a 20% load, 17% with the air conditioning off, which means cruising at 70mph only takes 10% more load than idling in neutral. It also showed about a 14% throttle position at idle. The highest throttle position I saw at any time was 88.6%, which is apparently all this car will give you with the pedal on the stop. I'm not really sure how to interpret these things, but I thought they were interesting enough to note.
 
Ryanb said:
Answer this, after reading many accidents of engine failures, fires etc. why do these airplane engines fail much more often than it seems car engines do. You dont hear of car engines "throwing rods" and what not? Whats up with this?
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Throwing rods is not really a typical failure on an aircraft engine either. The most typical failure is that the engine fails to receive fuel from empty tanks. The most common mechanical failures will be accessory related, magneto failures, fuel injector pump failure, cylinder head separation.

As for car engines not throwing rods, that would be incorrect, cars launch rods out through the block with about the same frequency as aircraft. This kind of failure is typically caused by a clog in the oil gallery or failed oil pump drive.
 
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