The SMA people openly recommend flying at full throttle all the time.
I've visited the Austro factory a couple of times as well & these guys also openly encourage running the Austros at full power all day long. They even suggest running at 100% power, with no issues. (Diamond lists 92% as max continuous power in the AFM)
I saw some of their fancy engine test beds at the factory. I think they've been running several Austros flat-out on those until TBO (1500hrs) without any apparent ill effects.
A friend of mine runs his Austros at 92% all the time during cruise. Seems to be fine - main issue is the added soot around the exhaust pipes.
I still think 85% is a good "power cruise" for the Austros - lose just a couple of knots, but benefit from lower fuel & oil flow... - also the turbos easily delivers 85% at FL180.
I saw some of their fancy engine test beds at the factory. I think they've been running several Austros flat-out on those until TBO (1500hrs) without any apparent ill effects.
Like Peter alluded to, nothing like 10 years of maintenance experience, if the data becomes available that is.. I tend to be a bit careful when everything is based on ground testing. Ground testing is often ideal. Almost constant running. Think of the excellent condition of the engines of a taxi even after 500.000 km. Compare that to the typical usage of a private individual who may not fly for a week or more while his plane sits somewhere in nasty conditions (wet, salty or both). Then there are other factors that may not be simulated on the ground, like turbulence or hard landings.
The engine manufacturers would of course suffer the consequences of non-performance, during warranty and beyond and they know it. So it it at least encouraging that they seem to stand by their products.
The SMA engine has more than 5 years of history and it is looking good. Very sturdy design. Diesel generators operate at 100% and some ship engines, too.
I think we cannot compare stationary, low rev Diesels, often huge and very much over-designed because weight is not an issue, to the Aero Diesels we are talking about here.
Ahh well, maybe I am just to conservative. Hope so!
Like Peter alluded to, nothing like 10 years of maintenance experience, if the data becomes available that is.. I tend to be a bit careful when everything is based on ground testing. Ground testing is often ideal.
Yes - for example, I understood that the 'certified' Rotax V6 was subjected to lots of ground testing but they never did actually get it airborne because it broke in taxi testing. They then made a 'strategic business decision' :-) to discontinue development.
Wow, the AOPA article on the SMA 6-cylinder project gives the alleged reason for the Cessna 172 JT-A in-flight shutdown in the final certification tests:
On the other hand, a Skylane JT-A suffered an engine failure during its flight test phase. The problem was traced to burrs on the SR305’s crankshaft—burrs caused by manufacturing defects that have since been corrected at the factory.
That is quite a surprise. A manufacturing defect not caught in the single-unit hand assembled project phase.
That indicates to me a bearing seized, broke up or whatever, or that the crankshaft broke. A lot more information than was previously available. The forensics of figuring out why that happened unexpectedly can be tricky business.
I’ve visited the Austro factory a couple of times as well & these guys also openly encourage running the Austros at full power all day long.
Yes, because a) the aircraft they are installed on will otherwise not cruise sufficiently fast for good sales numbers and b) on these diesels, flying full bore will not really ruin the fuel flow (like in a Lyco or Conti).
I still detest that running full power is good for the engines.
They even suggest running at 100% power, with no issues. (Diamond lists 92% as max continuous power in the AFM)
Easy to “suggest” a lot of things.
I saw some of their fancy engine test beds at the factory. I think they’ve been running several Austros flat-out on those until TBO (1500hrs) without any apparent ill effects.
Conti did that, as well. No significant wear. As the old saying goes: constant use doesn’t ruin engines. Disuse does.
A friend of mine runs his Austros at 92% all the time during cruise. Seems to be fine
Seems to be fine, yes. How many hours on these engines?
Any news on the SMA engine, or is this yet another Jet-A1 option that has died?
The years just go by…
That seems to have close to zero retrofit options, due to the form factor.
Amazing that Raikhlin took it all the way to certification. I would not have expected that.
