PROPMAN wrote:
I defy you to even measure the amount of “pollution” put out by an avgas fuelled GA plane.
Well considering the Avgas spec supposedly allows for 0.56 g of Pb / L, an hours worth flying for one aircraft could put out as much as 28g of Pb into the atmosphere? Multiply by number of piston engined aircraft times the average amount of hours flown each year… 500 hours would give some figure of 14 kg, should the Avgas contain the highest Pb content that is just legal.
But, you’d need to put it into perspective. How much lead is produced by an average car over it’s lifetime? Through batteries and wheel weights that end up in the environment. Some say ~7 kg per car over it’s lifetime. Multiply that by the number of cars…
but truth of the matter is that Cont and Lyc engines have become extremely reliable over the past decades.
Totally agree; the vast majority of GA pilots never see any engine failure in their entire flying career.
Otherwise, most would be dead, because if you do loads of forced landings at 50-60kt Vs, eventually you will get yourself killed.
At higher Vs, say 80kt, the chance of death goes up massively.
Well considering the Avgas spec supposedly allows for 0.56 g of Pb / L, an hours worth flying for one aircraft could put out as much as 28g of Pb into the atmosphere?
Anecdotally, current 100LL lead content is right at the bottom end of the spec. It would make no commercial sense for the mfgs to put in any more than the bottom spec.
Peter wrote:
Otherwise, most would be dead, because if you do loads of forced landings at 50-60kt Vs, eventually you will get yourself killed.
Even without getting dead, if Lyc/Cont engines didn’t have the reliability they did, the GA fleet wouldn’t be anywhere near as ancient as it is today. Many forced landings even injury free ones will result in a written off aircraft.
The Thielert engine has same or better reliability figures as the Lycontosaurus.
We’re not safe because of the great engines but despite the substandard engines…
Thielert engine has same or better reliability figures as the Lycontosaurus.
I am not sure that the statistics on that can be collected with any reliability.
Most Lyco engine work worldwide is done by independent engine shops who don’t report anything to Lyco. The only thing which might resemble centralised reporting would be that Lyco get a little order for replacement parts from each overhaul job, so they could work out how many are being overhauled. But they won’t know how many broke during flight.
Most Diamonds are owned by FTOs who keep very quiet about any issues, for obvious commercial/PR reasons. One FTO I know had four DA42s of which 3 were grounded for about a year, while they were issuing press releases about how great things are and how great a relationship they have with Diamond. Obviously things have much improved since…
And private owners rarely talk openly about any negative issues because most of them are either selling their plane right now (overtly or privately) or they plan to sell up at some stage and don’t want to leave an online trail of engine issues which a prospective buyer might stumble across.
So almost everybody will lie about almost everything pertaining to this issue 
I don’t know of any Lyco engine failures among people I know but I know of several Thielert ones. Totally anecdotal of course, and behind it are the much higher hours flown by (FTO) Thielerts than by the vast majority of private owners.
My own feeling is that the two are on the same order of magnitude – 100k hrs or so. They have to be for the simple reason that most GA pilots would be dead or crippled (or permanently scared of flying again) if the MTBF was say 1k hrs rather than say the 100k hours which is often mentioned re Lycos.
Even without getting dead, if Lyc/Cont engines didn’t have the reliability they did, the GA fleet wouldn’t be anywhere near as ancient as it is today. Many forced landings even injury free ones will result in a written off aircraft.
Exactly. A shock load + new prop will BER (beyond economic repair) most “spamcans”, and an in-flight mechanical failure will usually need an overhaul. Even an oil pump shredding will do that because metal will go everywhere. The average “spamcan” is worth the same as an engine OH.
Peter wrote:
I don’t know of any Lyco engine failures among people I know
I can tell you about one! A cylinder fractured on takeoff of a Cessna 172R in my club earlier this year (Lyco IO360-L2A engine). A very successful emergency landing followed with no further damage to the engine. The cylinder was replaced and a short time later the engine was replaced by a newly overhauled engine. (That was a scheduled replacement – it had nothing to do with the failure.)
But you are right about failures being rare. The PIC was a retired airline captain with 50 years experience of GA flying including extensive instructing and this was his first engine failure in any aircraft.
Peter wrote:
I am not sure that the statistics on that can be collected with any reliability.
No, that is hard but comparing the reliability of different engine makes is not difficult. You can assume that the same percentage of in-flight shutdown incidents get reported to the authorities for all engine types. The flight hours of the fleet assumption should also be similarly reliable for all. In the end you get shutdown rate that are halfway comparable. Those statistics give an advantage to Thielert but nothing groundbreaking. Here a very credible source, Continental press release: http://www.continentaldiesel.com/typo3/index.php?id=58&Year=2015&NewsID=149&L=1
Another interesting study by BEA on the troubled early Thielert gives some data: http://www.bea.aero/etudes/thielert.tae125.engines/thielert.tae125.engines.pdf
It should be noted that all piston engines, conventional as well as nonconventional,
have non-redundant components that can cause an engine shut
down or power loss (e.g. a failure of a carb float of a conventional spark ignited
carburetted piston engine). The engine certification rules have never required
redundant fuel systems for piston engines. Therefore there is no significant
difference in the fuel system design of conventional and non-conventional
piston engines. Because diesel engines are self-igniting, there is no need for
an ignition system at all. EASA has reviewed the in-flight shut down/power loss
(IFSD) rate of the TAE 125 engines. After implementing of several mandatory
corrective actions, the IFSD rate of the TAE 125-01 and TAE 125-02 engines is
now well in the expected range for piston engines. The FAA has established
the following general event rates for piston engines (see FAA Memorandum
1999-00006):
• Shutdowns/power losses: >1 every 10,000 hours;
• Accidents: 1 every 100,000 hours;
• Fatal Accidents: 1 every 1,000,000 hour.
The actual IFSD of the TAE 125 engines is around 0.4 every 10,000 flight hours
(rolling 12 month) which is less than half of the IFSD rate established by the
FAA.
Peter wrote:
I don’t know of any Lyco engine failures among people I know
I know several, some of which live 6 feet under now.
They LIVE down there? Why?
OTOH, most Thielerts went into DA42s and most failures there will not be reported.
And the Lyco twin market has shrunk a lot lately.
Archie wrote:
but truth of the matter is that Cont and Lyc engines have become extremely reliable over the past decades
I’m not sure they have “become” reliable, I think they have always been reliable as their designs inherently allowed. Are there any stats that show that the same basic designs are more reliable now than they were in the 1960s?
The improvements in the reliability engineering on these engines has been virtually zero in the last 50 years. And there is no question that they could be more reliable with stuff like electronic engine management/protection, use of new materials, better lubrication systems, use of computer simulations for better combustion chamber design, better cooling design, whatever.
