DB-605 versus Allison V-1710 TBOs

[Stephan Wilkinson]

I have seen references to the Daimler-Benz 605 engine as used in the Bf-109G being "timed out" at 150 hours of running. Does this mean it has reached an official TBO? Or that it needs comprehensive inspection and probably maintenance? Or that 150 hours is a generally accepted number for the length of time a DB-605 can be trusted to run without failure?

In the same vein, Allison V-1710s seem to have a reputation for "running forever"--well, 1,500 hours--without needing overhaul. Is this true?

(I'm writing about the "new" Erickson Collection Bf-109G-10 replica with an upright Allison engine and want to see if I can get some reliable numbers on the durability of a V-1710 versus a DBF-605.)

[redvanner]

I have seen references to the Daimler-Benz 605 engine as used in the Bf-109G being "timed out" at 150 hours of running. Does this mean it has reached an official TBO? Or that it needs comprehensive inspection and probably maintenance? Or that 150 hours is a generally accepted number for the length of time a DB-605 can be trusted to run without failure?

In the same vein, Allison V-1710s seem to have a reputation for "running forever"--well, 1,500 hours--without needing overhaul. Is this true?

(I'm writing about the "new" Erickson Collection Bf-109G-10 replica with an upright Allison engine and want to see if I can get some reliable numbers on the durability of a V-1710 versus a DBF-605.)

Stephan, 5 years ago I asked a question about the TBO of DB 601 / 605 in a German forum. The main engine expert gave the following answer:
Teilüberholung (part overhaul) : 100 hours,
Grundüberholung (main overhaul) : 200 hours,
maximum lifetime span: 2 main overhauls + 200 hours,
so a maximum time of 600 hours
all of the above by original DB manuals.
But he wrote additionally, today, IF key components are within tolerances, and you use spare parts then you might use the main parts even longer (of course a lots of parts will need to be replaced by that runtime.

IIRC the manual states, that the 100 hours overhaul time can be extended for a maximum of 50 hours if: operational reasons dictate so, if the engine and its components are thoroughly inspected and no problems occur, all parameters are in their limitations. But: this does NOT extend the 200 hours limit as well. (I believe it would make no sense in todays operational mode to extend the 100 hours limit).

Michael

P.S. I do not know what amount of work / change of parts either the 100 or the 200 hrs overhaul need.

[shrike]

That would be 150hrs of service before removal, disassembly and overhaul.

It can't be an apples to apples comparison in any case. The 150 hr TBO is probably for DB605 in late war trim which has a power to weight ratio roughly twice that of the Allison. Highly stressed, supercharged with water/methanol injection and in combat situations it's going to be run hard.

The Allison in the replica will have the advantage of another few years of development (or few decades) and will never be expected to put out close to it's own full horepower, let alone try to match the output of the DB.

Remember a Bf109 is roughly the same size as a Cherokee, with the weight difference being almost entirely engine. The Bf108, built in exactly the same fashion was a spritely performer with 240hp.

For point of comparison, I think the R-1820 had a combat TBO of only about 250hrs

[fiftycal]

early P-400 airacobras in the pacific and russia barely got 50 hours, this was the V1710-E4 but the advertised tbo was 150 hours. later in the war they raised this to around 500 hours, but apparently they used to overheat all the time and it would severely shorten their lives

[hang the expense]

You can fly an Allison farther than you can ship a DB.

[Mathieu]

I wonder why they still use the wartime figures. Many issues have been largely improved, think about the quality of the lub. oil and fuel. Beside that the engines will never be stressed as they did under war conditions. Is there anyone who knows if parts, particulary the bearings, are NOS or do the manufacture them again.

Regards,

Mathieu.

[Mathieu]

I wonder why they still use the wartime figures. Many issues have been largely improved, think about the quality of the lub. oil and fuel. Beside that the engines will never be stressed as they did under war conditions. Is there anyone who knows if parts, particulary the bearings, are NOS or do they manufacture them again.

Regards,

Mathieu.

Last edited by Mathieu on Fri May 05, 2017 9:58 am, edited 1 time in total.

[airnutz]

Is there anyone who knows if parts, particulary the bearings, are NOS or do the manufacture them again.

In your question you brought up another variable. The raw materials and production of the parts are available at a consistent quality today versus wartime. Fuel quality and petrochemicals, as you know, were often affected drastrically in the war years.

[redvanner]

I wonder why they still use the wartime figures. Many issues have been largely improved, think about the quality of the lub. oil and fuel. Beside that the engines will never be stressed as they did under war conditions. ...........

Regards,

Mathieu.

Well, 4 reasons: 1. Because the manual says so
2. Because Daimler Benz (or Mercedes Benz) will not provide any help or assistance of any kind
3. Because no one can or will change the TBO and be liable for any possible damage or loss of machine or man
4. To stay on the save side

BTW initially the operators of the first DB 605´s had problems with modern oils, as the oil grades nowadays are much "thinner" than German wartime ones, so a modern substitute had to be found that is comparable to the old ones. (Problems were with sealings high loss and leakages IIRC)

Michael

[GregP]

If you go research wartime TBOs, you'll find they were generally set by expectations of overhaul success rate. That is, in WWII engines were TBO'd with the expectation that 99+% of the engines could be overhauled and returned to service. They did NOT want to discover that the engine blocks had to be scrapped. They did NOT want to use new-production engines to replace in-service engines, Rather, they wanted a successful overhaul to be possible when the time came. It was generally expected that in-service engines would remain in-service for quite some time.

So, most U.S. engines started out at 250 hours TBO and the TBO time could be extended as experience at overhaul became available. By the end of gte war, Allison V-1710 were regularly seeing 500 hour TBO. Today, in civilian life, I know of many ALlison V-1710 owners who are flying them over 800 hours and they are running just fine. I know one guy who has 1,100 hours on his and it is running great. Of course, most warbirds owners are not running them at full power or especially at WER very often or even at all. First, they don't have the 150 PN fuel to do it and second, the government isn't paying for the engine. So, it is usually take off and almost immediately pull back to economy cruise. Same for Merlins, They are running well past wartime TBO due to being run easier than when they were in service.

I don't know any Daimler-Benz owners, but I'd assume they run well, too. No reason they shouldn't. The Planes of Fame operates a Mitsubishi A6M5 Model 52 Zero with the original Nakajima-built Sakae engine. It runs reliably and gives little trouble. If you go look at your copy of the 1944 Fighter Conference summary, you'll see the Zero they flew is the one that Planes of Fame operates now, and it was the only aircraft in the conference flight test program that never broke during the entire time it was flown there. For reference, during the conference, they put about 160 flight hours on the Zero.

[GregP]

If you go research wartime TBOs, you'll find they were generally set by expectations of overhaul success rate. That is, in WWII engines were TBO'd with the expectation that 99+% of the engines could be overhauled and returned to service. They did NOT want to discover that the engine blocks had to be scrapped. They did NOT want to use new-production engines to replace in-service engines, Rather, they wanted a successful overhaul to be possible when the time came. It was generally expected that in-service engines would remain in-service for quite some time.

So, most U.S. engines started out at 250 hours TBO and the TBO time could be extended as experience at overhaul became available. By the end of gte war, Allison V-1710 were regularly seeing 500 hour TBO. Today, in civilian life, I know of many ALlison V-1710 owners who are flying them over 800 hours and they are running just fine. I know one guy who has 1,100 hours on his and it is running great. Of course, most warbirds owners are not running them at full power or especially at WER very often or even at all. First, they don't have the 150 PN fuel to do it and second, the government isn't paying for the engine. So, it is usually take off and almost immediately pull back to economy cruise. Same for Merlins, They are running well past wartime TBO due to being run easier than when they were in service.

I don't know any Daimler-Benz owners, but I'd assume they run well, too. No reason they shouldn't. The Planes of Fame operates a Mitsubishi A6M5 Model 52 Zero with the original Nakajima-built Sakae engine. It runs reliably and gives little trouble. If you go look at your copy of the 1944 Fighter Conference summary, you'll see the Zero they flew is the one that Planes of Fame operates now, and it was the only aircraft in the conference flight test program that never broke during the entire time it was flown there. For reference, during the conference, they put about 160 flight hours on the Zero.

[GregP]

Sorry for duplicate post. I think I hit submit once!

[lmritger]

Stephan, if you don't already have it, I cannot recommend Calum Douglas' masterwork "The Secret Horsepower Race" highly enough. The answers you seek can be found in that book.

I can tell you that 605 reliability was absolutely horrific in 1942/43 due to issues such as low nickel content in critical parts, spark plug failures, poorly designed cooling circuits which also led to overheating and what not; reliability did improve to the point that they felt comfortable cranking up the boost pressure to 1,98 atmospheres by early 1945 but the average lifespan of a Jagdwaffe fighter at that point in the war was something like 25 hours, so long-term reliability was a moot point.

Lynn