Hardest plane to take down in WW2?

[FLYBOYJ]

Originally Posted by HoHun

You are losing me - I would not travel 2000 miles while rapidly climbing or descending either, and I'd certainly not keep take-off/emergency power applied during a rapid descent as that would take me way past Vne.

Not necessarily - WEP application in a decent will build up airspeed but not as quickly as you might think especially in a large aircraft. I'm talking about seconds here...

Originally Posted by HoHun

>My point was based mainly on cruise. WEP settings are just for that - emergencies.

Oh well - my point was that as soon as you move away from the optimum working point of the carburetted engine, efficiency drops markedly. Even at maximum continuous, which could be used for longer spells, specific fuel consumption had risen by 60%.

OK...

Originally Posted by HoHun

It also seems that using automatic mixture control was standard operation procedure even in the B-29 though it had a flight engineer on board whose primary task was to operate the engines. The USAAF doesn't seem to have thought there was something to gain from manual leaning.

Actually FEs did manually lean, especially if at a certain altitude/ MPP setting/ CHT the engine began to run hot or cold.

Originally Posted by HoHun

In fact, I seriously doubt that one could reduce the minimum 195 g/HP/h by any meaningful amount, but should you want to prove your point, here you can download the B-29 Flight Engineer Manual you might find helpful:

I seen that - you could doubt it if you like - if you lean to the point that you're not running at high CHT you're going to save fuel.

http://www.ww2aircraft.net/forum/oth...tml#post260968 (B-29 Engineering Flight book)

Originally Posted by HoHun

It lists a minimum of 201 g/HP/h at 15000 ft. Apparently, the automatic control knew how to lean with altitude, too. This is actually a higher figure than the minimum from the cruise control chart and reinforces my opinion that the abovementioned 195 g/HP/h are already the optimum. Daimler-Benz list their minimum with a tolerance of +10 g/HP/h - only towards higher figures. That's how I tend to read the US figures, too: no way you're going to shave off another 10% from the 195 g/HP/h figure.

You also have to remember that the automatic fuel controllers found in pressure carbs weren't the most accurate pieces of equipment. They did go out of adjustment quite frequently and it is a maintenance activity to adjust them at specified hourly intervals.

I work around T-41s that have IO-360s. We've discovered that the automatic mixture control goes out of adjustment about every 100 hours. Continental has a service bulletin to deal with this but for the most part most operators ignore the SB and only deal with the problem if they have a hard time starting the engine. I could see this problem being two fold on a large radial where the automatic mixture controller functions through a series of bellows and rubber diaphragms.

[HoHun]

Hi Flyboyj,

>Actually FEs did manually lean, especially if at a certain altitude/ MPP setting/ CHT the engine began to run hot or cold.

It's the manual I referred to that defines the use of Auto Rich as normal practice. I'm sure the engineers were trained to deviate from normal practice when necessary, but the manual describes what the USAAF considered the best way to operate the engines, and it relies on the automatic mixture control.

>You also have to remember that the automatic fuel controllers found in pressure carbs weren't the most accurate pieces of equipment.

That's why tolerances in specific fuel consumption are given towards increased consumption from the minimum figure.

If the engine is running sub-optimally, you might get it back to optimum performance by manual leaning, but that doesn't mean you can beat the minimum figure.

Regards,

Henning (HoHun)

[FLYBOYJ]

I downloaded the manual - on P87 (Chart C60) there is a mixture control setting based on constant RPM. Max cylinder head temp is 240C. Depending on altitude desired airspeed, density altitude etc., you could lean up to the 240C limit, it may not be desirable, but if so it seems, based on that chart, you'll exceed the numbers on the fuel flow chart. Now with that said there is the the best power setting where the pressure carburetors are probably set to (or the goal is to get them as close to possible to that setting). I cannot read the reange chart on the computer I'm using, I'm going to download it on my home PC to I could read the notes....

[renrich]

My original question was how can an engine continue to run with a cylinder(or jug) missing. I can see how that might be unclear. I meant with a cylinder or meaningful part of a cylinder no longer there(missing, MIA) because it had been significantly damaged by gunfire or malfunction.

[FLYBOYJ]

Originally Posted by HoHun

If the engine is running sub-optimally, you might get it back to optimum performance by manual leaning, but that doesn't mean you can beat the minimum figure.

Regards,

Henning (HoHun)

Lindbergh did it with the P-38..

"Lindbergh explained cruise control techniques he had worked out for the Lightnings: reduce the standard 2,200 rpm to 1,600, set fuel mixtures to "auto-lean," and slightly increase manifold pressures. This, Lindbergh predicted, would stretch the Lightning's radius by 400 hundred miles, a nine-hour flight."

Here's another example....

"First one, then two pilots reported dwindling fuel and broke off for home. MacDonald ordered the squadron back but because Lindbergh had nursed his fuel, he asked for and received permission to continue the hunt with his wingman. After a few more strafing runs, Lindbergh noticed the other Lightning circling overhead. Nervously the pilot told Lindbergh that he had only 175 gallons of fuel left. The civilian told him to reduce engine rpms, lean out his fuel mixture, and throttle back. When they landed, the 431st driver had seventy gallons left, Lindbergh had 260. They had started the mission with equal amounts of gas."

Charles Lindbergh and the 475th Fighter Group

[renrich]

Lindberg conducted classes with many pilots on several types of AC about fuel conservation. I recall reading he told them to forget about much of the stuff they had learned about babying their engines because they were military engines and could take a lot of abuse. He did all this including combat flying while acting as a civilian consultant.

[FLYBOYJ]

Originally Posted by renrich

Lindberg conducted classes with many pilots on several types of AC about fuel conservation. I recall reading he told them to forget about much of the stuff they had learned about babying their engines because they were military engines and could take a lot of abuse. He did all this including combat flying while acting as a civilian consultant.

Correct.

In actuality "exceeding the chart" could be done in almost any recip aircraft. A lot of times the data is there, it's just a matter of the way it is formatted on a particular chart and the parameters given.

[HoHun]

Hi Flyboyj,

>Lindbergh explained cruise control techniques he had worked out for the Lightnings: reduce the standard 2,200 rpm to 1,600, set fuel mixtures to "auto-lean," and slightly increase manifold pressures.

Certainly - but my impression is that he was able to do that was more the result of the original USAAF "matched power settings" not having been optimized for range beforehand. His strategy matches the procedure the British had established before. (I don't know the V-1710 specific fuel consumption values according to USAAF standard and to Lindbergh, but it would be interesting to know.)

My point regarding the B-29 is that the 195 g/HP/h are an absolute value that is close to the optimum for WW2 era Otto engines, and if you shave off 10% of that you arrive at 175 g/HP/h which is extraordinarily low. For perspective, the optimum figure I found (in Müller, "Junkers Flugtriebwerke") for the turbo-compound variants of the R-3350 running on 115/145 rated fuel is 170 g/HP/h, but that's a significantly improved engine over the R-3350-23 of the B-29 with the benefit of some five years of extra development.

But thanks for checking out the manual - I certainly appreciate that you know more about engines than I do, and if you find something that escaped me, it will be a learning experience for me!

Regards,

Henning (HoHun)

[FLYBOYJ]

Originally Posted by HoHun

Hi Flyboyj,

>Lindbergh explained cruise control techniques he had worked out for the Lightnings: reduce the standard 2,200 rpm to 1,600, set fuel mixtures to "auto-lean," and slightly increase manifold pressures.

Certainly - but my impression is that he was able to do that was more the result of the original USAAF "matched power settings" not having been optimized for range beforehand. His strategy matches the procedure the British had established before. (I don't know the V-1710 specific fuel consumption values according to USAAF standard and to Lindbergh, but it would be interesting to know.)

I don't have a P-38 manual in front of me but I do know Lindbergh's methods exceeded chart values within the POH that were based on standard settings (auto lean and forget).

Originally Posted by HoHun

My point regarding the B-29 is that the 195 g/HP/h are an absolute value that is close to the optimum for WW2 era Otto engines, and if you shave off 10% of that you arrive at 175 g/HP/h which is extraordinarily low. For perspective, the optimum figure I found (in Müller, "Junkers Flugtriebwerke") for the turbo-compound variants of the R-3350 running on 115/145 rated fuel is 170 g/HP/h, but that's a significantly improved engine over the R-3350-23 of the B-29 with the benefit of some five years of extra development.

Based on the charts from the FEs manual I came up with the following...

Fuel consumption: 570 gph 42” Hg/2400 RPM @ 25,000 feet

Fuel consumption: 430 gph 38” Hg/2000 RPM @ 25,000 feet

At 2000 rpm that equates a little over 100 gph at cruise.

Originally Posted by HoHun

But thanks for checking out the manual - I certainly appreciate that you know more about engines than I do, and if you find something that escaped me, it will be a learning experience for me!

Regards,

Henning (HoHun)

Thanks Henning - I think the thing to realize that many cruise charts are based on "medium values" based on very standard operation. I think the example of Lindbergh's P-38 career shows that performance charts can be expanded based on established engine operating parameters CHT/ MP/ EGT against RPM at altitude and applying those parameters against the operational environment.

[Graeme]

Originally Posted by renrich

The question I posed was how could an AC engine continue to run with a "jug" or cylinder was shot off like I have heard reported by several writers.

[HoHun]

Hi Flyboyj,

>Based on the charts from the FEs manual I came up with the following...

>Fuel consumption: 570 gph 42” Hg/2400 RPM @ 25,000 feet

>Fuel consumption: 430 gph 38” Hg/2000 RPM @ 25,000 feet

>At 2000 rpm that equates a little over 100 gph at cruise.

Is it possible to determine the powers for these exact settings? Then I could calculate the specific fuel consumptions for comparison.

>Thanks Henning - I think the thing to realize that many cruise charts are based on "medium values" based on very standard operation.

Roger that - unfortunately, I have seldom found the charts explicitely specifying for which assumption they are meant. For example, some read "The usual 5% operational margin have not been applied here", others make no comment at all. Some even note "The figures have not been flight-tested yet"!

Regards,

Henning (HoHun)

[Crumpp]

they had learned about babying their engines because they were military engines and could take a lot of abuse.

This doesn't sound right to me.

All aircraft engines are constrained by the same physics whether they are civilian or Military.

All the Best,

Crumpp

[FLYBOYJ]

Originally Posted by HoHun

For example, some read "The usual 5% operational margin have not been applied here", others make no comment at all. Some even note "The figures have not been flight-tested yet"!

Regards,

Henning (HoHun)

Right now I'm on a project with the USAF where we put upgraded engines in the UV-18 (Twin Otter). Although the mod had been used by civilian operators for a number of years, there were several climb and power setting charts that were never incorporated in the POH. Right now we are developing those charts based on the upgraded engines and will conduct test flights to verify the data. All for a 35 year old aircraft!

Originally Posted by Crumpp

This doesn't sound right to me.

All aircraft engines are constrained by the same physics whether they are civilian or Military.

All the Best,

Crumpp

Agree - the only one who "baby's" there engine is the owner operator who also flies his aircraft on a shoestring budget! MHO!

[renrich]

If Lindberg said it, and perhaps he didn't, then I guess he did not know what he was talking about.

[FLYBOYJ]

Originally Posted by renrich

If Lindberg said it, and perhaps he didn't, then I guess he did not know what he was talking about.

Well you have the whole 431st FS who bore witness of this....