Random Q. Why not diesel?

Pi1otguy

Pi1otguy

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For most of my time as a pilot there's been a push to get the lead out. Typically these focus around a new unleaded AvGas that performs mostly like 100LL but without TEL. But it begs the random question.

What about diesel engines running on widely available Jet-A? Jet-A isn't diesel fuel per se, but presumably it's close enough. I'm not sure how much weight the emissions systems adds, but wouldn't a diesel engine could generate enough power to raise the gross weight on many airframes.
 
Pi1otguy said:
For most of my time as a pilot there's been a push to get the lead out. Typically these focus around a new unleaded AvGas that performs mostly like 100LL but without TEL. But it begs the random question.

What about diesel engines running on widely available Jet-A? Jet-A isn't diesel fuel per se, but presumably it's close enough. I'm not sure how much weight the emissions systems adds, but wouldn't a diesel engine could generate enough power to raise the gross weight on many airframes.
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So the entire legacy fleet would have to replace its engines?
 
Pi1otguy said:
For most of my time as a pilot there's been a push to get the lead out. Typically these focus around a new unleaded AvGas that performs mostly like 100LL but without TEL. But it begs the random question.

What about diesel engines running on widely available Jet-A? Jet-A isn't diesel fuel per se, but presumably it's close enough. I'm not sure how much weight the emissions systems adds, but wouldn't a diesel engine could generate enough power to raise the gross weight on many airframes.
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Ask Diamond/Austro.
 
Pi1otguy said:
For most of my time as a pilot there's been a push to get the lead out. Typically these focus around a new unleaded AvGas that performs mostly like 100LL but without TEL. But it begs the random question.

What about diesel engines running on widely available Jet-A? Jet-A isn't diesel fuel per se, but presumably it's close enough. I'm not sure how much weight the emissions systems adds, but wouldn't a diesel engine could generate enough power to raise the gross weight on many airframes.
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How many air cooled diesel engines have you come across in your life?
 
Pi1otguy said:
but wouldn't a diesel engine could generate enough power to raise the gross weight on many airframes.
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Gross weight is a factor of a number of items than just engine power. And while there are diesels flying they usually tend to be found in niche uses for the same reasons there are limited turbines in similar aircraft: cost, payload issues, etc.
 
It's not just that it weighs more. It's where the weight is located.

The continental cd300 weighs 584 pounds compared to the 430 pounds of the io540. That's 150 pounds on a massive arm when mounted to the pa32....which is already nose heavy.

I was contemplating spending 20k+ to LOSE 20 lbs off the nose.
 
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Pi1otguy said:
Presumably the fleet replaces it's engines every handful of years at TBO. I'm envisioning a gradual change over a decade.
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Hey, wow, yeah!! Why overhaul a Lycoming O-360 when you could simply replace the whole firewall-forward with a completely different engine with different engine technology! What were the thousands of folks who have been working on this problem for decades (not) thinking??!?
 
Pi1otguy said:
Presumably the fleet replaces it's engines every handful of years at TBO. I'm envisioning a gradual change over a decade.
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So... to repeat... EVERY SINGLE LEGACY AIRPLANE WOULD BE REQUIRED TO GET AN STC FOR A DIFFERENT ENGINE AND INSTALL THAT ENGINE?

That is not a solution.
 
2-Bit Speed said:
So... to repeat... EVERY SINGLE LEGACY AIRPLANE WOULD BE REQUIRED TO GET AN STC FOR A DIFFERENT ENGINE AND INSTALL THAT ENGINE?

That is not a solution.
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I nominate Pi1otguy to be the one to call and explain this to everyone that spent more than $50,000 to install a new Lycoming in the last year.
 
Diesel is a great idea. But engines manufacturers have struggled to create workable solutions for legacy aircraft AND to create products that make financial sense for owners.

Though I suspect if there was a 10k engine per year demand things might move faster and at a lower cost.
 
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Salty said:
Rather than forcing diesel we might as well just go straight to turbine. Think of the children man.
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You can.

The problem is that they are still less efficient than equivalent GA piston engines. But close. They do close the gap between your typical Garret/Honeywell 1000+ hp turbines you find in your Caravans and PC24s.
 
I know what it costs to get complicated stuff certified with the FAA and EASA, and I know what you need to go through. Not to mention that each use case would also need to be approved (you can't make an IO-360 replacement that drops in every plane with a version of that engine, there are a zillion variations.)
BTW, to get FAA and EASA type certification for a large turbofan engine will cost you two billion dollars. And change.
It would be nice if Cessna had continued with the 182 diesel project, but they had problems, and decided it wasn't worth it. At $600K a copy (or more) they wouldn't be selling that many.
 
Money, deltahawk is charging what 110k per install, continental probably more, austro not happening

if i could go diesel for the price of an overhaul i would
 
I’d love to put a RR300 turbine on a Skywagon. 300 shp at 200#. The price kills the dream. A half million would take a long time to realize a return!
 
Stewartb said:
I’d love to put a RR300 turbine on a Skywagon. 300 shp at 200#. The price kills the dream. A half million would take a long time to realize a return!
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That just depends on the exchange rate you give to those smiles :D
 
Clip4 said:
How many air cooled diesel engines have you come across in your life?
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Many. Duetz tractor engines come to mind. Diesel, air cooled and very reliable with a 20,000 hour tbo.
 
Sac Arrow said:
You can.

The problem is that they are still less efficient than equivalent GA piston engines. But close. They do close the gap between your typical Garret/Honeywell 1000+ hp turbines you find in your Caravans and PC24s.
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Can I though? Pictures of a CAD engine doesn't inspire confidence the product is commercially available
 
Ask Porsche how much money they made with their diesel airplane engines. Corrected, they were gas engines. But they failed to be a successful entry in the aviation engine business.

And how many are still flying...

They did make it all the way through FAA certification, and put a fleet of them in the air.
 
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We were at Oshkosh a few years back and walking by the Continental group and I say "No way!". Margy goes what? I say look at the N Number on this plane. It was the plane she had learned to fly in. N73ER was an original Embry-Riddle plane that was renumbered N73FR when the university sold it. It was on lease to our the flying club at IAD and Margy got her private in it. The owners sold it to Stan Fetter who ran a traffic reporting operation over at Hyde. Stan put a Thielert diesel in it as it gave him cheaper long and slow operations. Apparently, it made its way down to some Florida flight school, still with the diesel, and Continental bought the Thielert line, so they put it on display.
 
2-Bit Speed said:
So... to repeat... EVERY SINGLE LEGACY AIRPLANE WOULD BE REQUIRED TO GET AN STC FOR A DIFFERENT ENGINE AND INSTALL THAT ENGINE?

That is not a solution.
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If you could make a diesel that weighed/produced the same HP as a gas engine it would be much simpler. But currently the diesels are way to heavy and would wildly affect performance/W&B.

Ie a 'drop in replacement' needs to be an actual drop in replacement.
 
Chip Sylverne said:
Many. Duetz tractor engines come to mind. Diesel, air cooled and very reliable with a 20,000 hour tbo.
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The question was how many air cooled diesel engines have you seen in your life, not if one came to mind.

If burning a diesel product is you goal, we have those in aviation now. They are called turbine engines. Light weight, very dependable and very expensive.
 
When mass-produced clone cruise missile / UAV engines hit alibaba, the EAB folks will snap them up.

Maybe trickle-down economics from the military-industrial complex works after all, it's just from AVIC :p

Hopefully in another couple short decades, everything will flip over to electric and render the 100LL debate moot.
 
2-Bit Speed said:
So... to repeat... EVERY SINGLE LEGACY AIRPLANE WOULD BE REQUIRED TO GET AN STC FOR A DIFFERENT ENGINE AND INSTALL THAT ENGINE?

That is not a solution.
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I thought with mosaic we could now hang a mercedes OM617 off the nose if we wanted to...
 
172andyou said:
I thought with mosaic we could now hang a mercedes OM617 off the nose if we wanted to...
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Why would you want to when you could have a turboprop or electric motor?

But on a more serious note, you cannot convert a standard airworthiness certificate to LSA (MOSAIC).
 
Clip4 said:
The question was how many air cooled diesel engines have you seen in your life, not if one came to mind.

If burning a diesel product is you goal, we have those in aviation now. They are called turbine engines. Light weight, very dependable and very expensive.
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Well, an engineer could explain why, but the TL:DR; is 'that's not how diesel engines work'.

Water cooling is not new, and water cooling would solve a ton of problems. Rotax engines have gear reduction AND water cooling and they are perfect fit for 100-125hp needs.

Also, historically, most 1,000+hp engines uses in proper airplanes had PSRU and/or water cooling. Only in civil aircraft (mostly due to cost and simplicity) did air cooling dominate.
 
pfarber said:
If you could make a diesel that weighed/produced the same HP as a gas engine it would be much simpler. But currently the diesels are way to heavy and would wildly affect performance/W&B.

Ie a 'drop in replacement' needs to be an actual drop in replacement.
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hmm wouldn't have to be a drop in replacement for me, id exchange a bit of weight for hp and liquid cooling. also since most are turbodiesels you're very likely to go much faster at altitude.
 
Answer: The R-101.

(short version, it was diesel, it very much didn't work, and the lessons IMHO are still relevant 100 years later.)
 
IMO what should have happened and probably still is the best way to solve the leaded fuel problem is for the EPA to just announce that 100LL will be going away in 25 years. IF they had done this 20 years ago manufactures would have come up with a suitable alternative by now and 90% of the engines would be capable of running something beside 100LL. As it is probably the best they can hope for it to eliminate 100LL by around 2050.

AS the 100LL drop dead date approach manufactures wouldn't be able to sell replacement engines that didn't run Auto Fuel, Diesel, or something else. And only a small percentage of operators would be force to change engines or find an alternative fuel by the drop dead date.

here is an idea, Diesel class(s) at the National Air Races? Maybe a Formula 1 or Sports Diesel Class?
Would promote development of diesel engine

Brian
 
pfarber said:
Also, historically, most 1,000+hp engines uses in proper airplanes had PSRU and/or water cooling. Only in civil aircraft (mostly due to cost and simplicity) did air cooling dominate.
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Hm. All those radial engines, BIG radial engines, in WW2 fighters and bombers and transports, were all air-cooled. The P&W R2800 made from 1500 to 2800 HP, depending on model. Wiki lists about 35 different airplanes and helicopters that used it up into the 1960s.

Or the P&W R4360 that made between 2650 and 3500 HP, used in at least 29 more aircraft types, including airliners.

Or the Wright R2600 that made between 1600 and 2100 HP. Used on 14 different airplanes.

More recently, we have the 1000-hp Shvetsov radial used on the Antonov AN-2 and others. I think it might still be in production in Poland or China.

All air-cooled.
 
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