Turbo Diesel Skyhawk Certified

[Bonchie]

Any guess to the cost of those components, then what would be the cost at TBR? Begs the question of how many Thielert's are out there (mostly in Europe)?

The outfit in Africa I've flown with several times has 182s with diesel conversions from France. An overhaul is 60k. What those specific parts cost, I don't know.

 

[BiffJ]

I know my Cessna 175 with a Lycoming 160HP O-320 and constant speed climbs better, takes off quicker and cruises at the same speed or better than the original 175HP continental geared engine powered plane did. 15 less horsepower and equal or better performance. I can see the advantage to the diesel even if the price of fuel is the same. Fuel is still cheaper when you're using less. Torque is king for turning a prop too......

Frank

 

[ElPaso Pilot]

Having a number of hours in the 172 Thielert diesel in higher altitude NM and Texas conditions, the magic performance bump comes from the turbo at altitude, with some additional help from the CS prop.

As the NA 172s were wheezing for air and slowing down, the turbo diesel was generating significantly more power and associated performance.

At sea level, the story might be different.

 

[Tantalum]

Horsepower sells cars, torque wins races

Totally. I was always curious why horsepower was the big number everything gravitated toward... isn't torque what you really care about? The actual rotational energy the engine has to empart to the propeller (or tires) and propel you forward

Mathematically torque seems to be the magic item. Horsepower is just torque multiplied by RPM then divided by some constant

Other than the turbo and altitude I always just assumed the lower horsepower diesel planes actually had better torque than their counterparts hence the comparable, or better, performance figures..

 

[tspear]

Torque matters for static thrust, and occasionally for climb.
HP matters for cruise. Hence CS props to allow an engine to develop max HP in multiple flight regimes.

Tim

 

[Jeff Cutler]

Having a number of hours in the 172 Thielert diesel in higher altitude NM and Texas conditions, the magic performance bump comes from the turbo at altitude, with some additional help from the CS prop.

As the NA 172s were wheezing for air and slowing down, the turbo diesel was generating significantly more power and associated performance.

At sea level, the story might be different.

True for any turbo, but just hearing about the cost of the diesel TBR vs TBO, not sure I understand how anyone could justify? $12 per hour additional engine amort versus overhaul cost. You can pay for alot of 100LL over JetA... until AvGas goes away, I guess.

 

[Sac Arrow]

Totally. I was always curious why horsepower was the big number everything gravitated toward... isn't torque what you really care about? The actual rotational energy the engine has to empart to the propeller (or tires) and propel you forward

Mathematically torque seems to be the magic item. Horsepower is just torque multiplied by RPM then divided by some constant

Other than the turbo and altitude I always just assumed the lower horsepower diesel planes actually had better torque than their counterparts hence the comparable, or better, performance figures..

Actually mathematically the reverse is true. It takes a specific amount of horsepower to move an airframe through the air at a certain speed, and to climb at a certain rate.

Depending on prop pitch, it is however possible that a lower horsepower diesel might be able deliver more horsepower during a specific flight regime, e.g. climb than a higher peak horsepower gasoline engine. But that's a limitation on gearing and/or prop pitch.

 

[Palmpilot]

Totally. I was always curious why horsepower was the big number everything gravitated toward... isn't torque what you really care about? The actual rotational energy the engine has to empart to the propeller (or tires) and propel you forward

Mathematically torque seems to be the magic item. Horsepower is just torque multiplied by RPM then divided by some constant

Other than the turbo and altitude I always just assumed the lower horsepower diesel planes actually had better torque than their counterparts hence the comparable, or better, performance figures..

If rotational energy is what you're concerned with, then horsepower is what you want to look at, because power is energy per unit of time.

 

[ElPaso Pilot]

True for any turbo, but just hearing about the cost of the diesel TBR vs TBO, not sure I understand how anyone could justify? $12 per hour additional engine amort versus overhaul cost. You can pay for alot of 100LL over JetA... until AvGas goes away, I guess.

That's an entirely different question than how can a lower HP diesel go faster than a 100LL version.

And I doubt the major market for this plane is in the US where avgas is common and plentiful.

 

[zaitcev]

Begs the question of how many Thielert's are out there (mostly in Europe)?

Diamond cranked out more than 600 DA-42s. So, logically, and considering the attrition over the years, about a thousand engines are flying. Lots of these airframes are surveillance platforms. One of them famously took footage of Russians digging in in Crimea in 2014 and got lasered.

Compared to Theilert/Austro/Continental small diesels, the medium clean-sheet designes by SMA fared poorly. Cessna could not certify the Skylane with them (kinda a murky story). Elsewhere, operators complain about their high cost. It's a rare case when an auto conversion did better than a real aircraft engine in aviation market.

Compared to either of these, RED is an absolutely massive powerplant. Well, it's not at the scale of a Merlin quite yet, but it's intruding into the area where small turboprops are viable nowadays.

 

[zaitcev]

Totally. I was always curious why horsepower was the big number everything gravitated toward... isn't torque what you really care about?

The acceleration of a racecar is proportional to the torque AT WHEELS. This is what often forgotten; cars have transmissions! A more powerful engine can be easily made to produce greater torque than a high torque engine, by selecting an appropriate gear ratio. A high torque engine can be a tactical advantage because it permits to shift gears less, so the racer has the flexibility of taking any line, be fast at any line, and disrupt the opponent's line. Once you aren't running wheel-to-wheel, hoursepower triumphs because of math and physics.

 

[Tantalum]

hoursepower triumphs because of math

Reminds me of: "I don't think that math is going to bring you back from the dead"

maybe it's semantics, but at the end of the day I want as much rotational force as possible so I can turn the biggest and most badass prop to move me through the air fast. Torque seems to be the most direct way of showing that.. not arguing though the math and physics of it though!

side topic: I think I've mentioned but I have an aftermarket digital gauge cluster in my car that plugs into the OBDII.. I have it setup to show HP, torque, and kilowatt. Neat to see the numbers and the harmony (or dissonance) between them. I'm assuming the figures are "at the flywheel" and I'm not sure how accurate it is because it can only use the standard inputs from the OBDII slot, but it is still cool to see the numbers move around, especially during gear shifts and highway on ramp accels

 

[ElPaso Pilot]

Reminds me of: "I don't think that math is going to bring you back from the dead"

maybe it's semantics, but at the end of the day I want as much rotational force as possible so I can turn the biggest and most badass prop to move me through the air fast. Torque seems to be the most direct way of showing that.. not arguing though the math and physics of it though!

No you don't. You want as much rotational force as possible at the right rpm to move you through the air quickly. That's the definition of horsepower -- it captures how much work is actually being done. RPM X Torque.

You can have all the torque in the world (think a winch), but it sure ain't going to move you anywhere quickly without those RPMs.

 

[FlyingTiger]

Hope they made it impossible to put the wrong gas in because every line guy in America is going to head to the avgas truck when they see a 172.