This Should Have Gone into Production...

[Shuckins]

Now I'm confused.

Widewing stated that 150 octane fuels were not used in the PTO, but F4UDOA you state the you have no evidence that the R2800-8 or -10 could run with 100/130 octane fuels because the B blocks were not rated for it.

If the Merlin engine of the Spit V could be run with it then why not the R2800-8 or -10?

Regards, Shuckins

[Squire]

Didnt they go to 115/145 fuel in the PTO in 1945?

[joeblogs]

I am looking at the Andrews article on the F6f that includes a Standard Aircraft Characteristics chart from 1949 that is based on 100/130 PN avgas.

The R2800-10 is a B series of the Double Wasp. All my data from Wilkinson suggests this engine was rated on 100/130 PN fuel. The A series engine was rated on only 100 PN, and many of the C series engines were rated on 100/145 PN fuel. It's quite possible those engines appeared in the postwar Corsair.

-Blogs

Originally posted by F4UDOA
JoeBlogs,

I have those charts for the R2800-18W and 32W(Without looking). I think I already scanned them. I have some -5 and AU-1 NAVAIR rating as well.

I have no evidence that the R2800-8 or -10 could be run with 100/130 fuel as the B blocks were not rated for it. I have seen where a F4U-1 was run at 65" MAP with ADI however.

[joeblogs]

It's possible since the P47-N could likely use it, but I've not seen any records of it.

-Blogs

Originally posted by Squire
Didnt they go to 115/145 fuel in the PTO in 1945?

[joeblogs]

As an aside there was at least one model of the Merlin (24) rated for 150 PN fuel and two Griffons (69, 72) rated for 115/145 avgas.

There were a number of postwar Griffons & Merlins rated for these high PN fuels.

There were two Cyclone 18 models rated for 150 PN fuels (-26 and -30); I think these were post war models.

There is even one model of the Cyclone 9 rated on this fuel.


-Blogs

[Widewing]

Originally posted by F4UDOA
JoeBlogs,

I have those charts for the R2800-18W and 32W(Without looking). I think I already scanned them. I have some -5 and AU-1 NAVAIR rating as well.

I have no evidence that the R2800-8 or -10 could be run with 100/130 fuel as the B blocks were not rated for it. I have seen where a F4U-1 was run at 65" MAP with ADI however.

I suggest you review the specific engine charts for aircraft powered by the R2800.... All R-2800s used in US fighters were rated for 100/130 avgas. All B Block R2800s used in the F6F and F4U, as well as the P-47s were not only rated for 100/130, but had restrictions on MAP if using 100 octane fuel (typically used for transport, utility and trainers).







My regards,

Widewing

[Widewing]

Originally posted by Shuckins
Widewing,

From the charts, if I may summarize a bit, it seems that most aircraft tested with 150 octane av fuel realized average gains in performance of:

Approximately 15mph in top speed.  Some considerably more than this.

About 500fpm increase in rate of climb.

Is that a fair summary?  Would the "official" top speeds posted by the Navy reflect the use of 130 or 150 octane fuels?  

If the listed speeds were for 130 octane fuels, could we expect similar gains of 15mph and 500fpm for naval fighters such as the -5 Hellcat?

Regards, Shuckins

As far as I know, only 100/130 avgas was authorized and issued. There may have been experiments done with higher octane fuels, but aircraft in the fleet operated on 100/130, which was the standard US grade for high performance aircraft during the war.

My regards,

Widewing

[F4UDOA]

As much as it pains me to say it but you are right WW.

I should have looked at my SFC charts before typing. What I should have said was the R2800-8/10 B blocks are not rated for 115/145 grade fuel.

I stand corrected.

[joeblogs]

Didn't see the reply for awhile and having re-read I realize I had a typo.
I had meant to say 150 PN fuel. 100/130 was standing fair in the Pacific.

-Blogs

Originally posted by Widewing
I suggest you review the specific engine charts for aircraft powered by the R2800.... All R-2800s used in US fighters were rated for 100/130 avgas. All B Block R2800s used in the F6F and F4U, as well as the P-47s were not only rated for 100/130, but had restrictions on MAP if using 100 octane fuel (typically used for transport, utility and trainers).



My regards,

Widewing

[joeblogs]

My manual for the R2800-8, -10 arrived. Here's one tidbit.

As I suspected sustained climb rates are not assuming the engine is run at WEP. It's not even assuming rated power, but rather 75 percent of rated power, which does not include the extra horsepower from WEP.

So it's no wonder the sustained climb rates of these planes slips a bit with more weight, given that rated horsepower (not maximum HP with WEP) did not increase.

-Blogs

Sustained

Originally posted by Shuckins
I can't really buy that argument Joe.  Weight can be offset by horsepower.  Otherwise, how does one explain the following?

P-38G at 15,800 lb. weight had an initial climb rate of 3,700 feet a minute using military power.

P-38L at 17,500 lb. weight had an initial climb rate of 3,700 feet a minute using combat power.

What was the difference between these two models?  Horsepower.  The version of the Allison engine used in the -G model was rated at 1325 hp.  The engine used in the -L was rated at 1,600 hp using combat power.

To quote Francis Dean:  "Increases in engine power usually more than made up for the inevitable airplane weight increase.  P-38J and P-38L fighters, though near a ton heavier than the early P-38s, took at least six minutes off the time getting to 30,000 feet and cut almost two minutes from the time to 25,000 feet.

The P-47D-25 and P-47M, by virtue of a new paddle blade propeller and increased engine power reduced time to 25,000 feet from 15 to 11 minutes, and took six minutes off the P-47C time to 30,000 feet."

Differences in empty weight between the -3 and -5 Hellcats amounted to only 127 lbs.  Since the -5 had water injection the power loadings were nearly identical.  Consequently, the -5 initial climb rate only marginally less than that of the -3.  Climb rate above 15,000 feet was actually greater than that of the -3.

The Corsair shared similar versions of the R2800 engine during their production lives.  Climb performances at similar weights were virtually identical.  Late F4U-1 Corsairs had an itialy climb rate with military power of around 2,900 fpm.  The F4U-4, with the same R2800-18W engine as the XF6F-6, could hit a climb rate of 3,900 fpm using water injection.  The XF6F-6 should have enjoyed a similar increase in climb performance when compared to the -3 and -5 model Hellcats.

Regards, Shuckins

[Shuckins]

Good post Joe,

That's revealing.  I had always assumed the published sustained climb rates were run a full power.

Or are these just figures that result from Pratt and Whitney's test programs, and not a common practice at Grumman, Chance-Vought, and the Navy?

Regards, Shuckins

[joeblogs]

I still have a lot of this thing to read, but my understanding is that the power curves published by the engine manufacturers are specific to the engine and not the installation (e.g. F6f, F4u).  

The section I was reading sounded as if the 75% rated power was an industry standard. What is interesting about that number is that it is right about where most engines are switched from auto-lean to auto-rich - in other words pouring more fuel into the cylinder to cool the charge and avoid detonation.

When you turn to specific aircraft, the question is how much power can you use in a sustained climb without overheating the engine. That will depend on the engine installation but also on the best climb speed of the plane - the best combination of climb angle and forward momentum to maximize the rate of climb. I imagine these are the numbers provided by the aircraft manufacturers or published in the standard tables from the airforce/navy we have all downloaded.

Interestingly, the best climb speed for the F6f is pretty slow (I am sure Dean has the exact number), so there isn't a great deal of cooling air getting to the cylinders, especially the bottom ones.

We've seen posts of historical materials that discuss overheating as a real problem in climbs for certain planes - the FW190 and La5 for instance.

As for instantaneous climb rates, the pilot has every available horsepower to use and I am sure WEP must really make these planes pop in a climb until the cylinder heads get too hot.

I'll post more as I get through this manual.

-Blogs

Originally posted by Shuckins
Good post Joe,

That's revealing.  I had always assumed the published sustained climb rates were run a full power.

Or are these just figures that result from Pratt and Whitney's test programs, and not a common practice at Grumman, Chance-Vought, and the Navy?

Regards, Shuckins