Piper to abandon the Piper Sport
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“You could say that about most engine failures ”
Yes! According to LAA eng the Rotax 912 series is the most reliable engine in the LAA fleet! As I have said many times, the prop is a significant advantage on a Rotax.
Rod1
Yes! According to LAA eng the Rotax 912 series is the most reliable engine in the LAA fleet! As I have said many times, the prop is a significant advantage on a Rotax.
Rod1
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Rod 1
The reliability of the Rotax is probably due to the fact that they are all quite new because of the "on condition" rules on the LAA some of the Lycoming & continental engines have not been apart for overhaul for twenty to thirty years.
If you look at the failure rate of Lycomings & contnentals that have had an overhaul in the last ten years or so I think you would find another story.
If you look at the failure rate of Lycomings & contnentals that have had an overhaul in the last ten years or so I think you would find another story.
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You could also look at the attrition rate on Lycon cylinders and their record of cracking - almost regardless of who manufacturers them. Or of course Continentals inability to produce a crankshaft without defects or Lycomings 'instant wear' valve guides or disposable camshafts.
As Rotax's age doubtless there will be issues - but the exisiting Lycon engines are very far from reliable or long lasting across the fleet. Although once they are treated well they are reliable.
As Rotax's age doubtless there will be issues - but the exisiting Lycon engines are very far from reliable or long lasting across the fleet. Although once they are treated well they are reliable.
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If you look at the failure rate of Lycomings & contnentals that have had an overhaul in the last ten years or so I think you would find another story.
You could also look at the attrition rate on Lycon cylinders and their record of cracking - almost regardless of who manufacturers them. Or of course Continentals inability to produce a crankshaft without defects or Lycomings 'instant wear' valve guides or disposable camshafts.
However, I think this is the chickens coming home to roost as a result of most of these engines going into poorly instrumented planes, and flown by uneducated pilots.
Cylinders don't just crack for no reason. They crack if the CHT is allowed to build up excessively, in high power (high chamber pressure) conditions, and rapid cooling from a high CHT probably doesn't help.
I would expect a regularly flown engine, non-turbo, with an EDM700 or similar, with the CHTs kept below 400F, to make TBO easily. My engine was apart at 700hrs (for the crank swap) and the only parts which were outside new limits were the exhaust valves (which were replaced). I fly LOP all the time in cruise.
It is a pity that the old motors do need careful engine management, and it is a failure of the mfgs and of the training apparatus to get this message across, but it is not at all hard to achieve.
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Agreed.
"Dear Customer, if you spend a few pounds on an EDM 700 or equivalent and follow a few simple procedures, we think you will get at least 30% more life (and better fuel consumption) from one of our engines before you have to send it back to us for overhaul."
"Dear Customer, if you spend a few pounds on an EDM 700 or equivalent and follow a few simple procedures, we think you will get at least 30% more life (and better fuel consumption) from one of our engines before you have to send it back to us for overhaul."
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The Rotax 912 was launched in the late 1980’s. Now I know that compared with the US engines which can trace their ancestry back to the 1930’s ground power units, that is not very old, but come on! The Rotax will always win the reliability war if it is being properly maintained. It removes the shock cooling problem and the “mags” are orders of magnitude more reliable and the product has much better (though not perfect) QA.
Rod1
Rod1
I think it's also worth mentioning - in the Rotax' favour - that mixture control is automatic, thus presenting an aviation newcomer straight out of a modern car with one archaic control less to deal with (or not) or complain about. I also think they start more readily than a Lyconental when cold, and believe they (must) use (cheaper?) automotive oil as a lubricant.
I think it's true that Rotaxes start better then Lycontinentals when cold, but they can be a pig when "warm" (shut down 30-60 minutes).
Losing the archaic mixture control (although it's an optional extra on a few installations) you do add the archaic choke control!
On most installations, you also lose the carb heat CONTROL, which is a big bonus.
The use of automotive fuels and oils definitely presents a huge saving (interestingly, I know a Rotax dealer who sells lots of 912 spark plugs to BMW motorcycle owners who use the same plugs, but they cost 4 times the price if sold for motorcycle use!).
On net, I also prefer the Rotax - and would point to the Tecnam P2006T as an example of a really good use of a 900 series engine.
G
Losing the archaic mixture control (although it's an optional extra on a few installations) you do add the archaic choke control!
On most installations, you also lose the carb heat CONTROL, which is a big bonus.
The use of automotive fuels and oils definitely presents a huge saving (interestingly, I know a Rotax dealer who sells lots of 912 spark plugs to BMW motorcycle owners who use the same plugs, but they cost 4 times the price if sold for motorcycle use!).
On net, I also prefer the Rotax - and would point to the Tecnam P2006T as an example of a really good use of a 900 series engine.
G
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Cold starting a Lyco is easy. Warm starting a fuel injected Lyco is not You need a Skytec starter motor...
The cost of oil is not really significant. I pay about £60 for 12 quarts of Aeroshell 15/50 which lasts for 50hrs so that's just over £1/hr - against some £70/hr for avgas. 9qts goes into the engine at the service, leaving 3 for topups and I usually need to buy 1 more quart during the 50hrs.
You need a Skytec starter motor...The cost of oil is not really significant. I pay about £60 for 12 quarts of Aeroshell 15/50 which lasts for 50hrs so that's just over £1/hr - against some £70/hr for avgas. 9qts goes into the engine at the service, leaving 3 for topups and I usually need to buy 1 more quart during the 50hrs.
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Cylinders don't just crack for no reason. They crack if the CHT is allowed to build up excessively, in high power (high chamber pressure) conditions, and rapid cooling from a high CHT probably doesn't help.
I don't think the Bing carbs are as unreliable as Silvaire says they are to be quite honest. And I can't seem to find any evidence online of failures. Though having dual carbs (on the 912 at least) doesn’t mean that if one fails you are still alright. The engine operates as two separate banks of Left and Right cylinders basically. A tiny change of mixture in one and you have a hell of a lot of vibrations. A lot, and it would probably shut down.
unless Bing does something different when these carbs are supplied for aircraft, the floats are plastic not brass.
BTW for how much does a new Lyco sell for?
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Genghis If you are needing the aircraft after a short shutdown all you need to do
Is let it idle with the fuel off until she falters then switch off, this will eliminate the possibility of a vapour lock At the carbs, with cool fuel she will start up fine,
NGK plugs can now be used with a box of 10 for £21 (914)
It doesn’t have a choke it has a cold start jet operated by cable
Silvare1 the rubber Diaphragms on the Bings and carb sockets are replaced
Every 5 years or on condition which ever comes first?
The floats are solid plastic with no possibility of sinking and the carbs have
Heat shields that double as fuel catchment trays with a drain tube to the rear of the engine, so no chance of dumping fuel onto the engine on my 914.
True they don’t fully weaken at altitude but it also doesn’t have a mixture control
To be misused by a incompetent pilot
IO540 I use 3 litres of aero shell sports plus4 at £23 with none used between changes,
She burns 17 litres’ of Mogas an hour about £22 at current prices, and a bonus is
A very low level sound footprint, (Good for the neighbours) and a reduced landing
Fee in Europe, All this from a 1200cc engine producing 100hp (115hp Take off)
No need to worry about carb icing, I could go on but I think it’s a reliable and well
Engineered engine IMHO
Is let it idle with the fuel off until she falters then switch off, this will eliminate the possibility of a vapour lock At the carbs, with cool fuel she will start up fine,
NGK plugs can now be used with a box of 10 for £21 (914)
It doesn’t have a choke it has a cold start jet operated by cable
Silvare1 the rubber Diaphragms on the Bings and carb sockets are replaced
Every 5 years or on condition which ever comes first?
The floats are solid plastic with no possibility of sinking and the carbs have
Heat shields that double as fuel catchment trays with a drain tube to the rear of the engine, so no chance of dumping fuel onto the engine on my 914.
True they don’t fully weaken at altitude but it also doesn’t have a mixture control
To be misused by a incompetent pilot
IO540 I use 3 litres of aero shell sports plus4 at £23 with none used between changes,
She burns 17 litres’ of Mogas an hour about £22 at current prices, and a bonus is
A very low level sound footprint, (Good for the neighbours) and a reduced landing
Fee in Europe, All this from a 1200cc engine producing 100hp (115hp Take off)
No need to worry about carb icing, I could go on but I think it’s a reliable and well
Engineered engine IMHO
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Because the Rotax is liquid cooled, and CHT never goes above 150C (usually operates between 90C to 120), and the engine block is made out of the same alloy with the same expansion rates, shock cooling isn't really a problem. Hence, better design has solved this problem hasn't it?
If Rotax made an IO540-type engine (250-350HP depending on accessories) how much would it weigh?
Diamond had problems with the Thielert coolant systems, and they had all the existing technology and experience to draw on.
Of the energy generated by combustion, around 44% goes out of the exhaust, 8% is lost via the oil cooler, and 12% is lost directly from the cylinders to the airflow (ref). So you have a lot of hardware just for that 12% or so.
BTW for how much does a new Lyco sell for?
IO540 I use 3 litres of aero shell sports plus4 at £23 with none used between changes, She burns 17 litres’ of Mogas an hour
Sure; you fly a much smaller aircraft. I would expect it to use less fuel.
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As IO540 points out, it's all about the type of aircraft and mission you are planning to fly with it. The problem with Rotax - as I see it - they currently aren't capable or interested in playing with Lycoming in Continental with anything that requires more than 115hp - for ex. C172/PA28 or heavier. Agreed, you cannot put 150 kg engine into a 400kg aircraft, but that doesn't make Rotax all-in-all better than Lycoming or TCM engines - it's like comparing light and relatively powerful two-stroke engine of a lawnmower with Rotax and saying it's better, because it's lighter. As far as Mogas use goes, my position remains the same - it's not useful for longer flights to other countries, since it is rarely found at international airports - Jet A-1 seems to be the long-term winner here, not Mogas.
From my experience (with Thielert, just for clarification), water cooling in aviation engines isn't that great. In summer, you have to make cruise climbs to avoid coolant temperature to go over the limit and in the winter you have to make very shallow descents - again to stay within the limits, whereas with conventional engine you have the advantage of manual mixture control to keep CHTs and their rate of change on a normal level. Just as said before, water cooling isn't a weight problem if the engine volume (and thus cooling area) is small. As soon as you increase volume to 3 or 4 liters (sure, VW produces 1.4 TFSI with 175hp output, but would it last 2000 hours on 75% power?), the water cooling becomes very heavy in comparison to traditional air cooling. Of course, if you take reliability in account, loss of cooling liquid could limit your maximum power (to prevent overheat) significantly, while air cooling is at least partly efficient even when at speeds near Vs.
Concerning the fuel consumption during various mission profiles (training, touring, etc.), if argument against Lycontinentals is that most people run them fully rich (especially during training, after-PPL renting etc.) and thus fuel consumption is much higher: I personally think it isn't the engine's or manufacturer's fault, but the instructor should have a word with himself. Sadly, most people think (and is also written in some Piper's POHs) that the full rich mixture is the "best and safest" for the engine. I'm not going to get into discussion about how fast an aircraft with Rotax goes in cruise - most Rotax installation are very modern, thus being much more aerodynamic than average spamcan, not to mention few hundred kilos lighter. With oil consumption, it's the same story: engine with higher displacement that produces much greater power will always burn more oil - unfortunately the engineering hasn't yet developed to such an extent that it would be possible to completely seal the combustion chamber and at the same time reduce piston friction to zero.
From my experience (with Thielert, just for clarification), water cooling in aviation engines isn't that great. In summer, you have to make cruise climbs to avoid coolant temperature to go over the limit and in the winter you have to make very shallow descents - again to stay within the limits, whereas with conventional engine you have the advantage of manual mixture control to keep CHTs and their rate of change on a normal level. Just as said before, water cooling isn't a weight problem if the engine volume (and thus cooling area) is small. As soon as you increase volume to 3 or 4 liters (sure, VW produces 1.4 TFSI with 175hp output, but would it last 2000 hours on 75% power?), the water cooling becomes very heavy in comparison to traditional air cooling. Of course, if you take reliability in account, loss of cooling liquid could limit your maximum power (to prevent overheat) significantly, while air cooling is at least partly efficient even when at speeds near Vs.
Concerning the fuel consumption during various mission profiles (training, touring, etc.), if argument against Lycontinentals is that most people run them fully rich (especially during training, after-PPL renting etc.) and thus fuel consumption is much higher: I personally think it isn't the engine's or manufacturer's fault, but the instructor should have a word with himself. Sadly, most people think (and is also written in some Piper's POHs) that the full rich mixture is the "best and safest" for the engine. I'm not going to get into discussion about how fast an aircraft with Rotax goes in cruise - most Rotax installation are very modern, thus being much more aerodynamic than average spamcan, not to mention few hundred kilos lighter. With oil consumption, it's the same story: engine with higher displacement that produces much greater power will always burn more oil - unfortunately the engineering hasn't yet developed to such an extent that it would be possible to completely seal the combustion chamber and at the same time reduce piston friction to zero.
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“From my experience (with Thielert, just for clarification), water cooling in aviation engines isn't that great. In summer, you have to make cruise climbs to avoid coolant temperature to go over the limit and in the winter you have to make very shallow descents - again to stay within the limits, whereas with conventional engine you have the advantage of manual mixture control to keep CHTs and their rate of change on a normal level.”
In 4.5 years of Rotax experience I have never had an issue with temps. Having said that I tend to cruse clime at 100kn and 1000fpm in preference max r of c as it gives much better forward vis. Tests have shown that in very hot weather at max r of c you can get quite hot if you go straight up to 8000 ft, but if you keep going to 10,000 it does not make much difference. Such a clime will start at about 1650 fpm, so 8000 ft does not take very long. Never had an issue in decent at all at normal speed. Most rotax installations have 2 X CGT, 2 X EGT, Oil t, Oil P, water T and volts so you have a good idea of what is going on.
Rod1
In 4.5 years of Rotax experience I have never had an issue with temps. Having said that I tend to cruse clime at 100kn and 1000fpm in preference max r of c as it gives much better forward vis. Tests have shown that in very hot weather at max r of c you can get quite hot if you go straight up to 8000 ft, but if you keep going to 10,000 it does not make much difference. Such a clime will start at about 1650 fpm, so 8000 ft does not take very long. Never had an issue in decent at all at normal speed. Most rotax installations have 2 X CGT, 2 X EGT, Oil t, Oil P, water T and volts so you have a good idea of what is going on.
Rod1
