Diesel motors are great...but?

[Utopia Texas]

(1) If you have a Tier 4 diesel engine in a airplane and it goes into a regeneration cycle at 35 thousand feet do you have to pull over until the cycle is over?

(2) Would you prefer 12 x 12 gearing or hydrostatic transmission in a diesel engine aiirplane?

 

[yanmars]

Airplanes diesels are being worked on. Still some problems but I think we will see more in the future especially if there is no good substitute for leaded aviation fuel. Some of the diesels best power range permits direct drive so no gear reduction is needed like on some water cooled car adapted power plants used in some home builts/experimentals.
As mentioned in other countries lead aviation fuel is harder to come by so diesel may be more of a future alternative. With the relatively small number of lighter general aviation aircraft being sold now it may be difficult to have research funding to develop/work out the problems with a diesel powerplant.

Many airports have seen a real reduction in hours etc. The costs can be considerable.

 

[Industrial Toys]

I was thinking maybe the altitude (thin air) could be an issue. Or operating over such a wide altitude range.

 

[arlen4720]

I was thinking maybe the altitude (thin air) could be an issue. Or operating over such a wide altitude range.

That's what turbos are for:thumbsup:

 

[arlen4720]

Is the fuel jelling at altitude a problem? Last time I checked it gets cold at the altitudes most commercial jet fly and standard diesel fuel wouldn't flow at those temperatures.

At least one of the diesels for airplanes are designed to use jet fuel which is quite a bit lighter than #2 diesel. But, the altitudes that jets fly is unsuitable for piston engines anyway.
Most general aviation goes on below 10,000 feet, really below 5,00 feet.

 

[gwstang]

Thanks for your enlightening replies. I was wondering about the "fuel gelling" problem at very cold temps way up high. I don't know if a prop plane can go that high. I didn't know model airplanes had the diesel engine?

 

[bigdeano]

The service ceiling of the WW2 P51 Mustang was up to 46,000 feet depending on which model.

 

[Redneck in training]

Here are two made in WI.
EPS | Engine Overview
DeltaHawk Engines

 

[flyerdan]

Diesel aircraft engines kind of got a bad rap here in the US because of the Diamond/Thielert debacle, however new suppliers have overcome those problems and now Cessna is offering it's most popular model with a Jet A mill. There are several outfits that retrofit older models with a Continental compression engine, along with a general renovation. They are popular with flight training ops as they can save a lot on fuel during a majority of flight training aspects. I'm sure as time goes on there will be more players enter the market as popularity takes off, and the avgas supply continues to shrink.

 

[Jerry/MT]

Why have they never been used in airplanes (WW2 or so)? Too heavy? Seems they are more dependable than gas? Just wondering since most of us here have diesel tractors and rave about torque/great fuel usage/longevity etc... Seems to me that it would have been a good choice way back then.

NASA had a program in the '90's to develop and light weight diesel and a small gas turbine engine to be used in light aircraft. As I recall, the lightweight diesel was for the small Cessna 172 type air craft and the small gas turbine was for larger aircraft with higher speed capabilities than the Cessna 172. I was on a NASA advisory committee for propulsion systems then, so we were briefed on it regularly. I retired in '99 so I lost track of what happened but I think demonstrator engines were built and ground tested. There was supposed to be a flight demonstration program but I do not recall ever seeing anymore about it after my retirement.
The biggest problem with early diesels in aircraft was the power to weight ratio was not competitive with an Otto cycle spark ignition engine even when the diesels better specific fuel consumption was accounted for. Modern materials and manufacturing methods may be able to tip that balance in favor of a diesel.

Here's a link:NASA - Small Aircraft Propulsion: The Future Is Here