Cessna to intro diesel 172 for 2015

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It's been a long time coming. I interviewed with Continental aircraft engines back in 1993 for a position developing a 2-stroke diesel engine for general aviation. That project never really got off the ground (so to speak).
 
It's nice, but $435k(starting price) for a single engine airplane is a bit outrageous. Guess I'll stay in the used market.
 
Originally Posted By: A_Harman
It's been a long time coming. I interviewed with Continental aircraft engines back in 1993 for a position developing a 2-stroke diesel engine for general aviation. That project never really got off the ground (so to speak).
It's been a very long time coming, since Packard's successful diesel in the late 1920s... http://en.wikipedia.org/wiki/Aircraft_diesel_engine But the issue has always been weight, diesel engines have to be robust, so the power/weight has always been a challenge... The real driver in this is the availability of fuel. The diesel can run on Jet-A...as Avgas gets more expensive relative to other fuels...the diesel makes more sense... The Cessna TTX pictured in the article looks a lot like a Cirrus SR-22/20. Nice looking airplane. For that level of performance, the price of admission is $500,000+...not in reach for most of us, but that's the market...sadly... And people wonder why GA is on the decline...
 
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So, with a few minor mods, it will soon be possible to "Roll Coal" on the peons, from above! I guess the mag check will disappear from the checklist....
 
What's New? (Maule's owners have been successfully running the SMA for a while.) It's worthwhile trade-off of the Loss of Spark Ignition. BUT, the SMA's Engine will require observation during operation for Ambient Temps.It's apparently sensitive to Froid.
 
I really like the idea of turbocharged, compression ignition aircraft engines. We could have, and should have, done this decades ago. The advantages of using a more efficient engine are obvious. What's not so obvious to many is the wonderful high altitude performance of turbocharged engines. The combo of diesel and turbocharging is an ideal one. Better, in my opinion, than air cooled, turbocharged gasoline engines.
 
Originally Posted By: Cujet
I really like the idea of turbocharged, compression ignition aircraft engines. We could have, and should have, done this decades ago.
I truly know little about aviation, but it seems that whatever entity that oversees design and operation of aircraft (FAA?) is very slow to change. Still using mags, leaded fuel and carbs- Why? I would assume after reading of the multiple part failures here (mags, starters and sticking valves to name a few) that the electronics and parts today's auto industry runs on would be more than durable enough to provide many hours of safe and reliable operation.
 
Their biggest hurdle is going to be managing the fuel pump wear issues with Jet-A being such a dry fuel and with #1/#2 being poor quality in the states. The light duty truck market is having a [censored] of a time getting keeping their pumps together, lots of them grenading within 1000hrs
 
Originally Posted By: The_Eric
Originally Posted By: Cujet
I really like the idea of turbocharged, compression ignition aircraft engines. We could have, and should have, done this decades ago.
I truly know little about aviation, but it seems that whatever entity that oversees design and operation of aircraft (FAA?) is very slow to change. Still using mags, leaded fuel and carbs- Why? I would assume after reading of the multiple part failures here (mags, starters and sticking valves to name a few) that the electronics and parts today's auto industry runs on would be more than durable enough to provide many hours of safe and reliable operation.
While it's nice to blame the FAA, they really are not the entire problem. Aircraft engines are unique, direct drive, reasonably simple and incredibly efficient. People often think a Chevy Small Block would be a better aircraft engine. Not so. It's far less efficient, it's HP to weight is worse, it's cooling drag (water cooled) is much worse and it's not particularly reliable in "aviation spec". Even that engine in the 172 (a Thielert variant) was known for early gearbox failures, at 500-600 hours. It eventually became a requirement to pull the engine at 600 hours for "repair", which was simply a replacement gearbox, and often an entirely new engine. The early versions of that engine were absolutely awful, with 300 hour gearbox requirements. And, other parts failed too, not just the gearbox. But fuel pumps, oil pumps etc. Aviation truly is hard on engines. I certainly hope those issues are worked out.
 
Originally Posted By: Cujet
Originally Posted By: The_Eric
Originally Posted By: Cujet
I really like the idea of turbocharged, compression ignition aircraft engines. We could have, and should have, done this decades ago.
I truly know little about aviation, but it seems that whatever entity that oversees design and operation of aircraft (FAA?) is very slow to change. Still using mags, leaded fuel and carbs- Why? I would assume after reading of the multiple part failures here (mags, starters and sticking valves to name a few) that the electronics and parts today's auto industry runs on would be more than durable enough to provide many hours of safe and reliable operation.
While it's nice to blame the FAA, they really are not the entire problem. Aircraft engines are unique, direct drive, reasonably simple and incredibly efficient. People often think a Chevy Small Block would be a better aircraft engine. Not so. It's far less efficient, it's HP to weight is worse, it's cooling drag (water cooled) is much worse and it's not particularly reliable in "aviation spec". Even that engine in the 172 (a Thielert variant) was known for early gearbox failures, at 500-600 hours. It eventually became a requirement to pull the engine at 600 hours for "repair", which was simply a replacement gearbox, and often an entirely new engine. The early versions of that engine were absolutely awful, with 300 hour gearbox requirements. And, other parts failed too, not just the gearbox. But fuel pumps, oil pumps etc. Aviation truly is hard on engines. I certainly hope those issues are worked out.
I realize that the majority of auto engines are not well suited to aviation use. That's not what I was questioning. My question is why can't auto type engine management systems/hard parts be used instead of the old style mags and carbs? Most auto electronics will go for a 100K plus miles without so much as a hiccup. Surely that translates favorably to hours of flight time?
 
Originally Posted By: The_Eric
My question is why can't auto type engine management systems/hard parts be used instead of the old style mags and carbs? Most auto electronics will go for a 100K plus miles without so much as a hiccup. Surely that translates favorably to hours of flight time?
Lycoming has a FADEC (electronic ign and elec port fuel inj) piston engine that, I believe, is certified. Not sure that it's any better in any way. Remember that we match injectors to the cylinder requirements carefully, so fueling is actually quite accurate. Electronic ign has been aval in various forms for some time now. It's not always better. In fact, The CAFE Foundation did extensive testing and was able to achieve improved MPG when operated lean of peak. But they lost power under normal operations, which resulted in lower top speed, and lower climb rates. The results match my experience. Mags make more power due to the very robust spark. Why this matters is that some aircraft (like mine) require as much power as the engine can produce to achieve acceptable cruise speeds. I lose way too much speed operating "lean of peak". (on the order of 20Kts) to save 2GPH. The end result is a very slight gain in MPG, and a significant increase in trip time. That's not acceptable. What I would like to see is a direct injection aviation engine. That could improve BSFC somewhat.
 
I have read about exp planes using the VW 2.0 tdi engine and worked very well even with the weight of water cooling the turbo provided a good power to weight ratio. The timing controlled by computer makes a big difference.
 
Originally Posted By: The_Eric
Still using mags, leaded fuel and carbs- Why? I would assume after reading of the multiple part failures here (mags, starters and sticking valves to name a few) that the electronics and parts today's auto industry runs on would be more than durable enough to provide many hours of safe and reliable operation.
An easy and often inaccurate assumption to make. Aviation is unusually hard on components. My Cessna 177RG operates at full throttle 100% and maximum cylinder pressure 100% of the time. Except during rapid descent and taxi of course. Think about driving your vehicle at full throttle for thousands of hours and expecting long life? Now think about how hot the exhaust valves would get under such conditions. And consider the cylinder pressure relationship to piston ring wear. Bearing loads etc. But, most importantly, consider the torsional stress on the crankshaft. Automotive crankshafts are not designed to hold a propeller, while twisting wildly on each power stroke due to high torque demands. Better power to weight is another factor in modern aircraft engines. Cooling drag of liquid cooled engines is at least 2x higher. (200 degree water vs. 400 deg fins) As more airflow is required to transfer the BTU's from a radiator. Overall efficiency of aircraft engines is better than automotive engines. Resulting in more range/or better payload. A typical Chevy Small Block conversion does not result in the expected 450HP and improved speed/reliability/efficiency. It results in increased weight, short engine life, 300HP, 0.55BSFC (Lycomings are now at 0.39) and the very real possibility of head gasket, cooling system, and prop reduction drive failure. Note: My friend Doug was killed in his experimental Lancair when his prop drive failed on his Chevy engine. All the signs were there. He had experienced a large number of engine failures. And 4 inflight shutdowns. I even strongly advised him to install a turbo 350HP Continental and avoid the risk.
 
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Originally Posted By: BusyLittleShop
Originally Posted By: Astro14
[quote=A_Harman] But the issue has always been weight, diesel engines have to be robust, so the power/weight has always been a challenge..
True but the Delta Hawk was a 200hp V4 Diesel with a dry weight of 327 pounds... I think one would fit my Chipmunk nicely... http://www.deltahawkengines.com/econom00.shtml
I think the DeltaHawk engine has many advantages. One big advantage is the nature of the 2 stroke firing impulses reducing prop and crankshaft harmonics. Most modern aircraft diesels require wooden propellers, such as the MT prop. The combustion event is so abrubt, the typical aluminum prop is subject to fatigue stress with diesel engines. While I like the MT props, I very much prefer conventional props. Wood is thicker and much less durable when impact damage is considered. It's amazingly easy to destroy the thin "trailing edge" of an MT prop by touching it with a tool (by mistake) or by hitting a tow bar on it, or by kicking up a rock during taxi. We've had multiple, unnecessary failures of our exceedingly expensive MT props.
 
Originally Posted By: Cujet
I think the DeltaHawk engine has many advantages. One big advantage is the nature of the 2 stroke firing impulses reducing prop and crankshaft harmonics.
I think another advantage of a V4 design are the cube-block crankcase that are inherently more rigid than the split case of an O4 engine... not to mention a 90º V4 affords up to 35% reduction in aerodynamic drag over the wide O4...
 
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My 200HP 177RG would LOVE a Delta Hawk engine. I volunteer to try it on my Cardinal! They have one flying on the Cirrus and the preliminary results are fantastic.
 
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