AVweb

« Back to Full Story

Diesel Déjà Vu: Lessons from Packard's Past

  • E-Mail this Article
  • View Printable Article
  • Text size:

    • A
    • A
    • A

If Charles Lindbergh had equipped the Spirit of St. Louis with a Packard Dr-980 instead of the Wright Whirlwind, he might not have had to stuff a gas tank in the nose in lieu of a windshield and he could have enjoyed the view while crossing the Atlantic. And that would have made ditching easier, too, since it's probably a 50/50 shot that the Packard—the first aircraft diesel of note—would have run long enough to get across the pond.

So it is with aerodiesels and sometimes I think not much has changed in the intervening 80 years. For an article in Aviation Consumer on the state of the diesel market, I picked up a copy of Robert Meyer's excellent The First Airplane Diesel Engine, part of the Smithsonian's Annals of Flight Series. I'd seen pictures of the Packard diesel in a Stinson Detroiter and always assumed it was a one-off experimental. It wasn't.

The Dr-980 was a full-up industrial project funded by the equivalent of more than $8 million in today's dollars. A 600-person factory was set up to build it. Think of it as the 1928 version of the Austro project. But it failed. There were several reasons for this. Packard had trouble keeping the cylinders on the thing, its quirky four-cycle, single-valve design tended to fill the cabin with stinky fumes and it was 30 percent more expensive than its competition, the Wright Whirlwind.

But like modern diesels, it had terrific fuel specifics--.0.40 BSFC compared to the Whirlwind's awful 0.60. I now see why Lindbergh had to carry all that gas. Actually, the Packard represented a much greater leap in efficiency against the Whirlwind than modern diesels do against their gasoline counterparts. A Continental IO-550 running lean of peak can operate in the .39 to .40 range, while today's aerodiesels typically run in the mid-.3s. A Packard-powered Bellanca CH-300 held the unrefueled time-aloft record of more than 84 hours until Dick Rutan broke it with the Voyager 1986.

What finally did the Packard in was higher-performance gasoline engines made possible by 87-octane gas. Pilots were more interested in speed than economy and range and I have to wonder if that's still true. Or will the imminent loss of 100LL drive enough buyers toward aerodiesels to make these engines real players? Austro, Continental, Centurion and SMA hope so.

But the ghosts of the Packard failure may still inhabit the diesel market. When you reduce the numbers on diesels, they sometimes turn out to be heavier, more expensive and less power dense than gasoline engines. In fact, to some extent, things have gone a little backward. The Packard matched the Whirlwind's weight and power density, but no modern diesels do that against their gasoline competition because gas engines have gotten lighter and more powerful. An O-470 can claim 1.78 pounds/horsepower; the Austro a portly 2.42—worse than the Packard. But that extra weight may do what the Packard couldn't: deliver long-term durability. With diesel, you can have light or you can have durable. Getting both is the designer's balancing act. SMA and DeltaHawk may have it figured out.

What's different now is assured fuel supply and that may be enough to tip it, even if diesels still struggle with weight. In looking at fuel production history, I was surprised to see that peak production for avgas occurred more than 50 years ago, in 1958. It's been downhill ever since. That was the year the military finally got enough jet aircraft and had retired enough piston airplanes to tip the balance toward kerosene.

So if ever there were overwhelmingly favorable conditions for aircraft diesels to succeed, we're lookin' at 'em.

Comments (22)

Last week you reported "No Avgas? Here's How To Burn Jet Fuel In A Gas Engine". This development would mean that diesel engines no longer need to be heavy by using medium compression, clever piston design and intelligent fuel injection and still can use JET fuel. The technology is here... why wait?

Posted by: John Piepers | July 19, 2010 4:54 AM    Report this comment

If-IF-we can get Avgas 100LL, we're paying already $12/gallon (EU) for it. So yes, bring on the diesels...

Posted by: Stijn Lammens | July 19, 2010 8:14 AM    Report this comment

The fact that there is so little avgas production is another argument in favor of keeping the lead in it. Why is the EPA so concerned with forcing the issue when the issue gets smaller and smaller on its own?

Posted by: Brad Vaught | July 19, 2010 8:21 AM    Report this comment

I must admit I am a confirmed diesel fan. With several Mercedes diesels in the family, one with over 450,000 miles on it, I won't drive anything else. At least until I can go all electric which I am working on. But if you are going to use the Packard diesel as your poster child for aerodiesels, I would suggest that your data points of one is highly biased. The Junkers diesels flew in paying passenger airline service for may years. With modern variable timing fuel injection some of the performance penalty can be addressed and with a turbo the constant pressure, awewsome torque of the diesel at the modest RPMs we like to run our propeller driver airplanes at seems to indicate a diesel solution. The technology is there, the problem, in my mind, is that there is a significant learn curve to be surmounted in diesel engine design manufacturing. Centurion went to Daimler Benz to acquire some of that institutional knowledge. Then ran the company into the ground. Continental initially went radical with a 2 stroke diesel, with not so surprising results. Gasoline engines have some along way in 80 years. So have diesels, but the unique aspects of an aerodiesel application will have to be learned and overcome in good time. Personally I am done with hydrocarbon based fuel and am going all electric. Tesla could make all of the free electricity he wanted and so can many others of us. Its time to make it a reality. So sit back and watch.

Posted by: Ed Wahler | July 19, 2010 8:55 AM    Report this comment

The Junkers diesels flew in paying passenger airline service for may years.<<

This is most likely a myth. The Jumo 205s were used in the Bloem and Voss 138 and 139 flying boats, of which a limited number were made. The 205s found use in military aircraft and both the civil and military versions were sustained by a wartime economy, which is not a measure of commercial success. In other words, they were almost certainly subsidized.

The 205s were displaced by higher power, lighter gasoline engines and eventually turbine engines. If they were attractive, they would have been picked up after the war. Well, they were...the Napier Nomad and the Deltic for marine use. The Nomad for aircraft use failed, the Deltic did not.

Now there may be a lot of excuses--the war killed diesel, Thielert mismangaged the project, SMA should have gone with two cycle and so forth.

But this fact remains: Diesel have proven widely sustainable in cars and trucks, boats and trains, but there is no compelling example of a commercially long-term successful aircraft diesel.

Not to say there won't be. Or that there shouldn't be. Just that there isn't. And say, how about letting me in on that free electricity thing. I could use some of that.

Posted by: Paul Bertorelli | July 19, 2010 9:20 AM    Report this comment

If anybody wants to see the Packard diesel, there's one on an aircraft (Curtiss Robin? Dunno, been years since I went there) in static display at the New England Air Museum at Bradley Field between Hartford, CT and Springfield, MA.

I'm not aware of any other survivors. (Doesn't mean there aren't any, just that I'm unaware).

Packard was a firm whose strength was engineering, but the diesel radial was probably overreach. Required them to schedule too many inventions.

Posted by: KEVIN O'BRIEN | July 19, 2010 10:15 AM    Report this comment

Just looked at the Da42 numbers (admittedly, a very quick glance). It seems that the heavier engine weight is at least partially offset by the lower weight for fuel for a similar mission. So, as long as ZFW limits aren't being hit, is the engine weight in itself that much of a problem?

Posted by: Mike Zippy | July 19, 2010 9:08 PM    Report this comment

Anyone from DeltaHawk want to chime in? I thought the weight of their 160/180/200 hp was the same as an 0-360, and with the lower fuel burn, the mission weight was less. They also are turbo-normallized to something like 16,000 ft or so. I realize certification is not yet done, but there are a number flying with a fair amount of hours, and if we are going to look to the future, we should use future examples rather than 80-year old examples. I wonder how much of the lack of legacy diesels is due to the fact that traditional diesel engineers were in the heavy industrial area, where they have excelled. Without a compelling reason, until now, there just wasn't critical mass of the technology being applied. Gasoline worked well enough to not make an economic case to introduce and amortize anything new, diesel or otherwise. Even if it could have been done corectly 20 years ago or more, there wasn't a compelling economic case to bring in any new technology.

Posted by: TOM LUBBEN | July 19, 2010 11:35 PM    Report this comment

DeltaHawk has the same problems as Packard, and doesn't have the same resources (financial or human). They are working towards the certification of the 180-hp engine but it has yet to demonstrate reliability or durability.

Until they have an engine in series production, and we're starting to get numbers from independent operators, I'd take all specifications and performance claims with a grain of salt.

Remember the Thielert diesel? It was great on paper, until you actually were trying to operate the beastly thing and ran into little details like the 300-hour life limit on the gearbox.

Remember: crawl/walk/run always happens in that order. It's great to watch new technology develop, but being the first one to own it is not for everybody.

Posted by: KEVIN O'BRIEN | July 20, 2010 1:45 AM    Report this comment

Here are some power densities for engines of note:

Wright J-5: 2.26 HP/LB Packard Dr-980: 2.26 HP/LB SMA SR 305 1.9 HP/LB Deltahawk V4 2.0 HP/LB Lycoming O-360 1.6 HP/LB Centurion 2.0 2.18 HP/LB Austro AE300 2.42 HP/LB

Not too hard to see why gasoline technology persists. In a small airplane with minimal power, weight matters a lot.

Posted by: Paul Bertorelli | July 20, 2010 5:38 AM    Report this comment

Paul, did you mean to say "LB/HP"? Your list seems to indicate that the O360 generates less horsepower per pound than any diesel.

Again, though, shouldn't one also consider the lesser amount of fuel a diesel needs to carry for similar range/performance in the weight calculations?

Posted by: Mike Zippy | July 20, 2010 5:44 AM    Report this comment

Let me reformat that here. I reversed the weight and power. Also, this forum software doesn't do well with column format. In this group, the Lyc O-360 has the best power density.

Wright J-5: 2.26 LB/HP

Packard Dr-980: 2.26 LB/HP

SMA SR 305 1.9 LB/HP

Deltahawk V4 2.0 LB/HP

Lycoming O-360 1.6 LB/HP

Centurion 2.0 2.18 LB/HP

Austro AE300 2.42 LB/HP

Not too hard to see why gasoline technology persists. In a small airplane with minimal power, weight matters a lot.

Posted by: Paul Bertorelli | July 20, 2010 8:10 AM    Report this comment

Again, though, shouldn't one also consider the lesser amount of fuel a diesel needs to carry for similar range/performance in the weight calculations?<<

Yes, you should. But if the power density is too low, the fuel economy may not offset the difference enough to be an economic player.

A comparison for equal power. The O-360 runs at .41 BSFC. The diesel runs at .36 BSFC and assume it runs at the same speed for equivalent power--diesels might not to because of cooling/induction drag. So for a full tank--say 50 gallons of gasoline--the diesel can get the same range on 38 gallons.

The weight Delta for the lesser fuel carried by the diesel is 46 pounds in favor of the diesel. (300 pounds of gas for the gas engine, 254 pounds of Jet A. for the diesel.) If the diesel is 46 pounds heavier, it's a wash. But if the diesel is 100 pounds heavier, it doesn't work as well.

Deltahawk claims the same weight as Lycoming, so the equation works. But you have to poke at the claims to make sure they're apples to apples. The SMA pencils out well because we can compare it directly to the O-470 in the Cessna 182 in actual flight circumstances.

Posted by: Paul Bertorelli | July 20, 2010 8:42 AM    Report this comment

The DeltaHawk does do a direct comparison to the O-360 using two Velocity RG aircraft, and the data is on their website. So that is more apples to apples than not, although they did use an earlier 160hp version of their engine. Even with less HP it looks pretty good. My own perspective is somewhat flavored by the fact I have seen their facility (many years ago at the start) and have alway been impressed by the quality and forethought of what they are doing. All these new efforts take a lot of upfront investment in time and intellect and money, but I think they have no illusions about the task and challenges. The visit to their shop in Racine really impressed me.

Posted by: TOM LUBBEN | July 20, 2010 10:15 AM    Report this comment

Surely the figures we should be looking at are based around, say, 75% power i.e. in the cruise.

The major (some say only) benefit diesel has is vastly superior part-throttle fuel consumption.

Posted by: Richard Whincup | July 21, 2010 3:50 AM    Report this comment

Junkers G38s flew London to Berlin with 4 .diesels

Posted by: Tim Vecchiarelli | July 21, 2010 6:02 PM    Report this comment

The Theilert experience is a cautionary tale, but not necessarily a comment on Aircraft Diesels. Theilert chose a poor design for the transmission, resulting in expensive maintenance at short intervals. This is less important in their big UAV market than for retail aircraft. Austro likely went too far the other way in a bid to get certified and in the air; their cast iron transmission is likely overkill, resulting in poor power to weight. In neither case can transmission woes be laid against the Diesel concept for aircraft engines. If Deltahawk gets to market with their carefully developed engine, we may see a truer test. The SMA engine appears to work well, but at too high a price. Continental may improve on that. A future consideration is noise; 2700 RPM engines are unlikely to meet noise standards, so Deltahawk may have to re-engineer for lower RPM. Geared engines are a better bet for noise. Liquid cooling is more likely to result in long life. Where is the Gemini Engine? Their estimates on size and weight are good; will they meet their numbers? Jet A and Diesel are much more common throughout the world than gasoline or particularly Avgas. The Diesel versus gasoline engine fight may be won on fuel availability.

Posted by: BRIAN HOPE | July 22, 2010 9:58 AM    Report this comment

The Aero Diesel designed by VM (Detroit Diesel) in the mid 90's solved all the problems discussed here, economy, wieght, simple design and reiability. The real issue holding up the Aero Diesel is Wall Street economic. Who is going to invest in a product requiring high capital investment with little potential or short term return, only to be saddled with unrealistic liability.

Posted by: Darrell Yelton | July 22, 2010 11:30 AM    Report this comment

As far as the Delta Hawk goes - don't hold your breath. 10-12 years into its development and the projected price went from 30,000 to over 62,000. missing your mark by over 100% - I would say a re-think is called for. Not a bad engine, but as long as they can get investors to keep them in a job, what do they care?

The Jumo's one shortcoming was the exhaust piston burning and having a very short life - this can be solved with modern carbon pistons, as can any of the other minor problems it had. There really is nothing so difficult about making a decent aero-diesel; it's all proven technology. It just takes the will to to it - but there is more money in .coms and real estate, so why bother? It would take somebody with the finances and the passion for it and these types of individuals seem to have died out with Howard Hughes.

Posted by: PETER THOMAS | July 25, 2010 10:00 PM    Report this comment

TCM IO-550N 1.4 lb/hp

Posted by: Greg Goodknight | July 27, 2010 11:55 AM    Report this comment

P.S. Speaking of having the passion and the finances for such a project - I have the one, but not the other! Now if I could only find somebody with the other....

Posted by: PETER THOMAS | July 27, 2010 11:59 AM    Report this comment

I thought it would be exiting to see what Austro-Steyr can accomplish with their new diesel, but was disappointed when I saw the M1 block was for marine and automotive applications. I checked out the m16sci for automotive with 272hp and found it has a weight/power of 2.34lb/hp. I fly the DA40D in Aeroclub of Oslo with the Thielert installed. The plane is great but we have had two cases of engine quitting. It is great at altitude though with the turbo. We cruise at 142Kts TAS in FL100 at 77% power burning in the order of 6.2gph. No other 4place plane in the world can do that.

Posted by: Finn Hoyer | March 3, 2011 3:29 PM    Report this comment

Add your comments

Log In

You must be logged in to comment

Forgot password?

Register

Enter your information below to begin your FREE registration

« Back to Full Story