Diesel vs Jet A

[pilottj]

Hey guys, I was reading about the Diamond DA-42. It uses twin aero diesel engines that run on Jet A. Chemistry is not a strong subject for me, but I gather Jet A and Diesel are very similar. Could one type of fuel be used in the other type of engine? Could the DA-42 in theory use regular diesel that powers typical ground/marine equipment? Is regular diesel a viable aviation fuel in this instance?

Cheers
TJ

[seaniam81]

Jet-A and Diesel are kinda close but not (really) interchangeable. Mostly Jet-A is closer to kerosene then diesel found in the gas pumps. Secondly Jet-A is "dry" as in there is no lubricants and additives in it, as apposed to diesel which needs them for the injectors. Third Jet-A is not built for compression ignition like diesel is. And the Diamond engines are built different then a truck/car engine. In fact the old Thielert diesel diamonds required the pilot to sign a waver before Exxon would fill there planes because it ran rough(er) with Jet-A. But that was a liability thing.

I've heard of and seen airports stick Jet A into thier old diesel vehicles, to save some money. And that worked but Jet-A into newer vehicles would gum them up pretty good, and not run all that well.

As for viability thats a tough one, but I don't think so. Jet is just to easy to make, and that add all the safety junk that would be needed to run diesel in aviation I don't think it would be cost effective.

The Mogas vs Avgas is special because Avgas is hard and expensive to make, but still look at all the hoops needed to be able to run Mogas legally.

[CAPFlyer]

We ran Jet-A in even 2004 compliant engines at Denver. All we had to do is put in an additive to properly condition the fuel. With Ultra-Low Sulfur fuels, the issue is lessened even more as the Sulfur was most of what lubricated the engine. I would be interested in seeing how things work now.

Sent from my SAMSUNG-SGH-I747 using Tapatalk 2

[rosesnowm]

The Mogas vs Avgas is special because Avgas is hard and expensive to make, but still look at all the hoops needed to be able to run Mogas legally.

[pilotgod]

Jet A is refined kerosene for aviation use. Diesel is kerosene based fuel. The main differences from a standpoint of powering engines is that Diesel has additives for emissions and most importantly for lubrication. Jet A has no lubrication qualities to really speak of and what additives it has are not really an emissions issue, but more to keep the fuel stable across a wide range of temperatures. The DA-42 can run Jet A because the engine is designed to not require the fuel to have lubricating capabilities. This changes a bit of the maintenance schedule, but is not really anything that would cause an operator any grief.

For over 6 years I was the supervisor at an FBO in the Dallas area and we would run Jet A in our Diesel GSE. Add a bottle of Marvel Mystery Oil every 5 tanks or so and it was fine. You wouldn't want to do this on anything with modern emissions like our diesel fuel trucks (that is what the Off-Road Diesel was for), but for tugs, GPU's, and the like it works fine.

There are two main reasons that MoGas has been slow to be implemented as a blanket replacement to Avgas. First is Octane rating. Just as the Mustang, Connie, DC-7, etc. are given operating limitations for running 100LL instead of 130 due to increase power, the same would happen when you go from 100 Octane to 87,which is MoGas requirement, even though you could drop 92 Octane Super and be at about the same abilities. The other issue is engine knocking. For the most part, aircraft piston engines are air cooled, large displacement engines. Running an unleaeded fuel in these engines is going cause problems with knocking and with temperatures. So far, only lower performance and specially designed new engines are getting MoGas approval. Your standard IO-540 for example, is not likely to ever really run happily on MoGas. This is why there is a push to devlop a bio-fuel that is comparable to 100LL.

[CAPFlyer]

Actually, the push is to create an unleaded fuel comparable to 100LL, not specifically a bio-fuel. Swift Enterprises' 100SF happens to be a "bio-fuel", and is currently the most advanced unleaded AVGAS replacement. 100SF is actually more of a sustainable synthetic fuel than a "bio-fuel" as it still uses binary hydrocarbons. The difference is that they're produced through biomass instead of being pumped out of the ground.

[greasysidedown]

I don't know the chemistry either and I don't recall what was needed for the switch but in the late '80s the US DOD converted all of its diesel equipment and vehicles to run on JP-8. I think the driving force was the increased need for JP-8 for the M-1s and the resulting decreased need for diesel as the M-60s were withdrawn.

[pilotgod]

My day job is as a lead/supervisor for one of the two companies that provides fueling services at KSEA. The comments above are correct in that basically, Jet A is highly refined kerosene. Diesel is a kerosene product. They both will ignite when at the correct ratio and under pressure, which allows a diesel engine to run on Jet A. Technically, a jet turbine will run on diesel, but it will put out more black smoke than the entire SAC B-47/B-52 fleet combined and you'll be needing to overhaul that engine pretty quickly. Until the recent EPA changes (2007), it was common practice to run ground service equipment off of clean Jet A samples. Anyone who has ever worked in fuel distribution knows you quickly wind up with gallons upon gallons of perfectly good Jet A just sitting in drums as waste fuel because once it is removed in a sump it can't be reused for aircraft. So, instead of just having it hauled off to be burned in an incinerator for asphalt, we would filter it and run our tugs, GPU's, trucks, etc. off of it. As long as you toss in a bit of lubricating additive, there was nothing to worry about. Until the treehuggers (and the tax assessors) chimed in.

[Kiwi Spitfire]

Anyone who has ever worked in fuel distribution knows you quickly wind up with gallons upon gallons of perfectly good Jet A just sitting in drums as waste fuel because once it is removed in a sump it can't be reused for aircraft. So, instead of just having it hauled off to be burned in an incinerator for asphalt, we would filter it and run our tugs, GPU's, trucks, etc. off of it. As long as you toss in a bit of lubricating additive, there was nothing to worry about. Until the treehuggers (and the tax assessors) chimed in.

Or anyone who has worked at a 747 depot maint facility - lots of tank de-puddling! 20 litres of Jet A-1 with a litre of Mil-H-5606 hydraulic fluid chucked in for some injector lubrication works a treat in your personal diesel vehicle

Is no mystery why you see a lot of aircraft mechs driving diesels hehe

[000rick000]

Hey guys, I was reading about the Diamond DA-42. It uses twin aero diesel engines that run on Jet A. Chemistry is not a strong subject for me, but I gather Jet A and Diesel are very similar. Could one type of fuel be used in the other type of engine? Could the DA-42 in theory use regular diesel that powers typical ground/marine equipment? Is regular diesel a viable aviation fuel in this instance?

Cheers
TJ

I have fond memories of that bird! I did all my initial ME training in the DA-42, and then racked up ~50 hrs of flight in them until I moved. Great aircraft. This was back in 2007. At that time we ran on Jet A-1 as Diesel was not certified for use in the USA. I'm not sure about now, as I haven't followed the timeline, but at the time, it was a viable fuel source outside of the USA/wherever it was certified. I flew the Theilert Centurion 1.7L and 2.0L engined versions. It was a very efficient engine. IIRC, it was like ~8gph fuel burn (total). Overall a great aircraft. One interesting note, is that VNE & VLO were the same speed, which allowed for some speedy visual approaches. It had great decceleration qualities as well, due to it's dual flap config (meaning outboard of the engines, the single two piece flap was a slotted config, but as it passed under the engine nacelle and inboard of the engines and under the fuselage, it was connected via a tongue-in-groove assembly and changed to a split flap for great speed reduction quickly.) It was a real pleasure to fly.

[Jettrader]

Jet-A and Diesel are kinda close but not (really) interchangeable. Mostly Jet-A is closer to kerosene then diesel found in the gas pumps. Secondly Jet-A is "dry" as in there is no lubricants and additives in it, as apposed to diesel which needs them for the injectors. Third Jet-A is not built for compression ignition like diesel is. And the Diamond engines are built different then a truck/car engine. In fact the old Thielert diesel diamonds required the pilot to sign a waver before Exxon would fill there planes because it ran rough(er) with Jet-A. But that was a liability thing.

I've heard of and seen airports stick Jet A into thier old diesel vehicles, to save some money. And that worked but Jet-A into newer vehicles would gum them up pretty good, and not run all that well.

As for viability thats a tough one, but I don't think so. Jet is just to easy to make, and that add all the safety junk that would be needed to run diesel in aviation I don't think it would be cost effective.

The Mogas vs Avgas is special because Avgas is hard and expensive to make, but still look at all the hoops needed to be able to run Mogas legally.

Actually the Thielert TAE engine is a modified car engine (from the Mercedes A-Class).

I have around 300 hrs on Diesel Cessnas and we operate them exclusively with Jet A1 (which is the prefered fuel for it). It can be operated by normal car Diesel, but then temperature restrictions apply. You can mix it with JET A1 at any mixture but when returning to JET A1 operation one has to reach a certain mixture ratio before temperature restrictions don't apply anymore. If you're interested I can post the sections from the TAE-125 manual.