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Northrop F-15A / RF-61C Reporter

For my part. I added the internal 500 gallon fuel tank: adjusted the fuel flow for cruising range of 1900 miles @ 360 mph ( cruising speed ) with max ferry range @ 4300 miles with external tanks ( to specs ): Adjusted the viewpoint and CG: Softened the brakes so you dont fly through the windscreen when you step on them: Changed the propellers out for standard propellers instead of the big paddle propellers used on the P-61B&C: Adjusted the thrust to give us 400mph @ Sea level which should give us the requisite 440mph @ 27000 feet: and tested the planes ability to land @ 80mph for short field work. admittedly, it's a hair raising experience landing that slow, but it does it..
Left to do?? I have to get the rpms down from 2900 to 2700. Test and adjust to make sure the aircraft is developing 1hp for every 6.6 pounds of weight. Those will keep me busy for a little while..
missing information: Take off distance, landing distance.
Since this thing is developing so much power so quickly ( about like using a draft horse to pull a laptop out of a ditch ), the takeoff roll is much shorter than the P-61.
Pratt&Whitney report this plane as using their R2800-73 engines. These are 2800HP engines initially used on the P-61C and the first engine produced by Pratt&Whitney to produce 1HP per Cubic Inch. I'm doing my best to ensure we get thee correct performance for that engine.. Anyway. I'll keep you updated..
Pam
 
Graham Whites "R2800" lists the -73 as a 2100 hp takeoff and mil power, with the 2100 available up to 28,500', an impressive performance! It however does not mention use of water injection which would be necessary for the 2800 hp. It does list a landing speed of 93 mph. The -77 engine only differed in the ignition system used.

It does note 440 mph at 30,000 ft. As this would be "dry" power it doesn't have the built in WEP time limit imposed by FS. Impressive for such a large plane!
 
You may have some confused information there. The Original F15A prototype was based on a P-61A that was chopped down and converted to a two seater F-15. It had originally been slated to be built as a fighter ( The P-61E ) but was cancelled with the end of WWII, and reincarnated as the F-15A prototype which sported a 2000 HP Pratt and Whitney R-2800. Only one was built. The remainder of the RF-61s were P-61C conversions using the 2800 HP engine.
There was a technologie difference fom the R2800-63W to the R2800-73, and I desperately need to find the web site with the history of the engines designer and design progression, because what i'm about to say is simply extraordinary leaving the burden of proof in my court.

The R2800-73 didnt use WEP, BUT! Well, The fuel for the model 73 was 115 octane with a lot of lead. This helped cool the cylinder heads, but wasnt enough to win the in house competition against the R3600 team ( the corn cob ). Yeah, thats right, the 2800 HP R2800 was the result of a competition between the two design tams, only the R2800 chief designer was bloody crazy. Still at one horse power per cubic inch ( a record the R3600 team never achieved ) even he knew when he had reached the limits of the technology. Besides the 115 octane fuel, there was an ethanol mixture, but it wasnt fired directly into the cylinder. It was fed in with the fuel. The mechanism they used to accomplish this metering is diagrammed in the PDF located here. https://ww2aircraft.net/forum/threa...e-manual-double-wasp-r-2800-ca-engines.37875/

Here's the biggest issue. The only people with anything even close to canon information on these engines, seems to be Pratt and Whiney themselves. Even the changeover from numeral nomenclatures to the C and CA nomenclatures appears to confuse people and there is a great deal of understandably innocent misinformation out there. Why Mr. White lists the 73 as a 2100 HP engine, i do not know. Several sites, including revolvy ( https://www.revolvy.com/main/index.php?s=Pratt & Whitney R-2800-10&item_type=topic ) list the 73 as being the subtype which developed 2800 hp using water injection and a General Electric CH-5-A3 turbocharger. What is possible is that Mr White misread the data, as the model 83 produced 2100HP. and the distance between a 7 and an 8 when making a deadline, is very short. It is very possible he made a typo, and didnt realize it, then continued to use the data for the model 83 without knowing he'd made a mistake.. Still, more sites cite the model 73 as being not only 2800- HP but the engine used in the F-15A than not.. ( https://www.revolvy.com/main/index.php?s=Northrop+F-15+Reporter&item_type=topic )
 
Whites 950 page book seems to be the definitive work on the R2800, not only do they have specs for every model, there is a chapter on every aircraft that used this engine, including the P61-F15A series.

As far as I can tell "No Production, aircraft installed R2800 reached 2800 hp without water meth injection". Methanol cannot be used in aircraft engine fuel for various reasons, even "gasohol" or "Heet" for fuel anti icing. It's a problem for aircraft such as my Super Cub that have an Auto Gas STC, making sure that the gas has no alcohol in it.

Meeting the speed performance figures with the lower HP is not an issue in FS, but will result in a slightly lower acceleration and climb rate.

My guess as to why it did not have Water injection? Appropriate regulation of the turbo charger which would have to do a lot of thinking in an era when machines did not think much. Development of such systems could be very troublesome and time consuming. Time was a luxury during the war.

: )

Quote from one of your sources:


 
Oh no, please forgive me. I was incorrect if i mentioned methanol.. It was very early in the morning you see. No, the engine used water/ethanol but rather than injecting it into the cylinder directly, it was fed in as metered fuel. Thats why its so important that i find that website that was there when we worked on the P-61 and has since disappeared. It goes into how they did it..

Heh.. I'm sitting here with Squadron Signal's P-61 Black Widow open to page 76 where it shows the F-15A-1 Tail number 559303, and at the same time i have all these other windows opened up all over the place.. The caption for the F-15A-1 reads " The production F-15A-1 Aircraft differed from the XF-15 by utilizing the same engines and cowls as the P-61C." And the image indeed shows P-61C Nacelles attached to this F-15A-1.

If we go to http://www.aviation-history.com/northrop/p61.html and scroll down too the P-61C section, it states:

P-61C
The P-61C was essentially the same airframe, but with more powerful turbosupercharged R-2800-73 radials offering a max WEP of 2,800 hp (2,088 kW). It was heavier than the A or B models and was said to be less maneuverable. Exterior differences of the XP-61C were a large air scoop under each engine and paddle-bladed A.O. Smith propellers to take advantage of the increased power.

As too how the engine developed power without direct water injection into the cylinder I believe the answer is in the lower right corner of the below image showing unmetered fuel ( Avgas ) and metered fuel ( water/ethanol ) going through the same control unit.
3hUoplP.png


I think your correct about the supercharger, but i'm no expert. The main bearings played a very large part in power production and engine temperature as well. Again though thats part of that missing web page i cant find.. I do know that when the germans acquired an R2800 that P&W had a heart attack. The bearings were a top secret alloy compound and they were terrified the germans would find out.

Regarding Whites, It may very well be the definitive publication on the R-2800 But even God made a mistake once. However, there is one more detail that we may not be considering and White may have. After the war, as surplus planes and engines entered the civilian sector FAA regulations demanded that the military grade superchargers be removed. I dont know why. I always thought it was terribly unfair. With the F-15s, that would mean an entire change out if i'm correct which is where the 2100HP version may have been introduced. I dont know. I'm guessing here..
Pam.

(Edit) Correction on the fuel: The RF-61 FAA Type Certification lists the fuel used as being 130 Octane.
 
The way the water methanol injection worked was to meter it through the carburetor. Injecting it into the cyl would not work. The methanol was there to keep the water from freezing, it was not really as a fuel component. The water introduced into the intake manifold vaporized and considerably cooled the mixture, allowing a greater mixture density, making the supercharging more efficient, allowing more fuel and air on each intake stroke. The water also cooled the internal flame temperature slightly, allowing a leaner and more stocimetric mixture, yielding greater power than with the too rich mixtures normally used at high power settings. The water also increased the mass flow through the engine and carried a lot of waste heat out through the "tailpipe". After all heat transfer via cooling fins, out the tailpipe and through the oil coolers was really the limiting factor for potential engine power.

The P61A had an R2800 -10 which was also used in the Hellcat and was fitted with WEP as a -10W in the F6F. Some A and B series aircraft did have water injection (10 W engine), with 24-36 gallons on board, good for 15-20 mins of use.

The -73 and -77 engines were also used in the P47N and with water injection were capable of limited 2800 hp at 72" MP, but had the same 2100 HP at 54" for Mil Power. (Hundred Thou pg 281). So far no definite indication that the Reporter had Water injection, and some indication it did not, but if I do find it I will pass it along.

: )
 
That would be greatly appreciated Tom.. Thank you..

For the purposes of the initial release however, I'm leaving them at 2800 HP. The biggest reasons for this is plain and simple fun factor Copmbined with an exceedingly short ( and apparently ever shortening ) list of available data to draw from. I also didnt have any tools when i first started this project. What i did know from the various books in my collection as well as various other sources, was that the P-61C developed 2800 HP, and the f-15A was based on the P-61C using the same wings and engines.. I can easily model WEP into a second FDE and offer it as an option for those who want reality. The end result remains the same with a 360 mph cruise speed and a top speed of 440 mph. The F-15A was an amazing plane no matter hopw you looked at it. Fast, Sleek and more nimble than her somewhat heavier progenitor, the P-61C. It's only fault was being created at the wrong time in history.
 
America's Hundred Thousand and also "Northrop's Night Hunter" have some data on the various models of the P-61, but seem to fall off the planet when it comes to specifics about the Reporter.

No info is no info, so currently any case can be made. The water injected C models could carry up to 531 lbs of water/meth plus whatever the associated equipment weighed. That's a lot of weight! It is possible that a recon aircraft might be better off without the weight, being able to go higher and faster and further? I don't know. Heinemann who designed the A4 and many other famous aircraft had a philosophy for that project of "Simplicate and add lightness". An extra pound of basic weight required stronger structure, bigger engines, more fuel, which kept spiraling. His assertion was that an extra pound resulted in ten.

Only 500 -77 engines were built in total, all by Chevy.

Did they toss out all the weight they could and rely on cleaning up the airframe for the 440 mph or are they relying on the water injection to achieve that speed only in a sprint? Unlike the real world, once we set the HP and thrust, we trim the drag to get the proper speeds.

Sure it will be a fun flier!!
 
An interesting sidelight: The main crank bearings were Lead/silver and Iridium, with about 4% Iridium. The Germans who did examine engines from shot down aircraft couldn't understand why the bearings were "contaminated" with iridium.
 
:) Exactly
The thing that frightened P&W though wasnt that the germans would find the Iridium, but rather do a full metalurgical analysis and get the formula. At the time, those bearings were top secret.

Still working on finding the original P-61 thread. If it exists, its buried deep.. :(
 
Last edited:
JDTinballs said:
Have you tried putting the web address into the wayback machine?

https://archive.org/web/
Click to expand...

Welll, thats just it. I dont have the web address, and i cant even remember the name of the chief engineer who's history i followed to find the site.. I know the link in buried somewhere in the original P-61 project thread, but buried could very well be an understatement with as much information as we put into that thread. It's over a thousand pages if i'm correct.
 
Thanks to Seahawk, I've found this once again. This time, I saved it and it'll be getting backed up to Bluray disc.. Why is this document so important?? For me its because it isnt just about numbers and data. It lets you smell feel and taste the very soul of these engines, and the crazy man who made them.
In the end, it turns out there was very little these engines couldnt do below 3800HP and 150In/Hg MP.. Yeah, you read that right.. But see, That was Frank Walkers unique way of heckling the R4360 team.. Every time they made a milestone, Frank would take his little 2800, and beat them.. What we got out of it in the end, was one of the most amazing, dependable and ubiquitous engines in the world.. Its a delightful read, and provides an insight into these engines you would never expect.. Enjoy..

http://www.enginehistory.org/Biography/FrankWalkerWeb1.pdf

"
WATER INJECTION

In early 1943, word came down from the front office that a means must be found to

get additional power from existing engines without redesigning either the engine or

airplane it was in. While Pratt & Whitney was working around the clock to complete

the 3000HP R-4360, it was still years away and could not be fitted into existing

aircraft.

The shortest path to more power is always more manifold pressure. Since the P-47

had a turbo-supercharger which could produce surplus manifold pressure, it seemed
a good candidate for more power. The rub was that with the additional compression

of the inlet air came heating of the inlet charge which resulted in power-limiting
detonation. With the 130 PN fuel than available, Pratt & Whitney was already

getting all the power that was possible with the R-2800. Someone in the front office
suggested that water injection be tried. Perry Pratt was the Project Engineer.
Frank acquired a stock R-2800 “B” engine, serial number 5275, directly from the
production line. The only modification to the engine was a longer hollow bolt to
accommodate a second banjo fitting that supplied water to the fuel inlet of the
supercharger. Frank performed all of the initial water injection calibration by
manually adjusting the throttle, supercharger, propeller, and water injection settings.
Once the behavior of the water-injected engine was understood, Frank presented
data to the carburetor group which, under the direction Dick Coar, designed and
developed a water injection regulator and the associated carburetor modifications.
Frank got 2150 HP the first night. This was up from the 2000 hp the engine normally
produced and was the sole result of being able to use a leaner mixture at take-off
power. Until then, the engine had to be run very rich at take-off power to prevent
detonation, actually using fuel to cool the engine. It was running so rich in fact, that it
was producing less than ideal power. In later experiments, manifold pressure was
increased to simulate the output of the turbo-supercharger, and horsepower
increased dramatically.
Ultimately, the maximum power achieved on the “B” series was 2800 HP at 2700
RPM. Maximum power ever achieved on the “C” series was 3800 HP at 2800 RPM.
The maximum manifold pressure ever recorded was a staggering 150 inches of
mercury (inHg)! This was up from dramatically from the 49-inHg maximum manifold
pressure originally allowed in the R-2800 “A” series of engines.
Water injection worked by reducing cylinder inlet temperature, thereby delaying the
onset of detonation. As the water evaporated in the induction passages of the
engine, it providing a prodigious amount of cooling to the fuel charge due to the
latent heat of vaporization of the water. Cylinder inlet temperatures went from about
350qF to about 100qF. This increased the detonation margin to the point that up to

150 inHg of manifold pressure could be used. When water injection was in use, the
engine was markedly smoother, and the interior of the combustion chambers stayed
extremely clean with no carbon or varnish build-up on the piston crowns, valves, or
ring packs. Frank remembers that “There was no hard carbon whatsoever. You
could clean the top of a piston down to bare metal by wiping it with a cloth”.
German engineers tried water injection (Wassereinspritzung) on their gasoline
engines, but with limited success. Germans, who were very good at building high-
precision pumps, had perfected direct fuel injection for their large aircraft engines.
German engineers injected water directly into the cylinders as well. Since the water

did not have time to evaporate and cool the induction air, the large cylinder inlet

temperature reduction was not achieved. Frank learned of this while reviewing a

report on a captured German aircraft engine. "


"
RACING THE BIG GUYS

Early in 1942, work began at Pratt & Whitney on the R-4360, a secret monster

engine that was destined to have nearly twice the power of the stock “B” series R-

2800s that were by then in production. Pratt & Whitney used the time-honored

experimental development methodology of “Run ‘em, bust ‘em, fix ‘um” where

prototype engines were rapidly cobbled together and gotten into a test program to

find the weak points. Such was true of the R-4360. The team suffered their share of

false starts and blown engines as they made slow progress at making the engine

increasingly powerful.

The Pratt & Whitney R-4360

By the time the R-4360 team was getting 2800 HP out of the prototypes, Frank was

well into water injection development with the R-2800 “C” series engines. Unknown
to the R-4360 guys, Frank was regularly running his R-2800 at 2800 HP for 100

hours at the time. The reader must realize that each new power milestone in R-4360

development was ending with a damaged engine as each of the many parts found

its respective limit. Frank could not resist rubbing in the failures.

When the R-4360 team surpassed 2800 HP, Frank brought them over to his test cell

and extracted 2800 HP from his “little” R-2800. A month later, when the R-4360 first
produced 3000 HP, Frank summarily bettered their result at 3200 HP. Ultimately.

Frank drove the R-2800 to a whopping 3800 HP. The R-4360 team eventually

surpassed that mark, and went on to 4000 HP. Frank was tempted to try for 4000

HP on the R-2800, but finally decided against it. He did not have a good feeling
about pushing the engine past 3800 HP "

My Kind of crazy.. I love it..

Pam









 
You see, numbers are only a starting point. You can make an airplane using nothing but numbers taken from some computer generated data sheet with all the personality of a limp noodle, and well, thats what youll get; a limp noodle. Repairmen use numbers to fix things, not create things. Engineers ask: What if? and Why Not? Numbers dont provide answers. putting things together and blowing them up provides answers, and sometimes they're answers, numbers will never give you: Iridium on a ball bearing.
You want to experience a plane that when you get into your virtual cockpit, you can feel smell and taste it.. You dont want numbers. You want to step into the shoes og Jack Northrop, Kelly Johnson, Johnny Meyers, Willy Messerschmidt, all of them: see what they saw, feel what they felt, Experience things in the way that only a very fortunate few have experienced, and fall in love with the skys all over again, with each flight you make..
Numbers alone wont give you that. you have to get inside the lives and heads of the people who made them. Learn how they possibly saw things and learn what drove them day to day.. It wasnt money, and it wasnt numbers..
 
The racing people do use some of this "tech" to boost the power in their machines. But back in the thirties, when the major breakthroughs were made to allow the evolution of power plants that powered WWII aircraft, the bearing technology, harmonic balancing, sodium cooled valves and on and on, small but important details to plug every leak in the reliability of the engine formed the basis. Always bumping against the strength of materials.

Major initial development of the Double Wasp (R2800) was actually conducted by P&W with a single row test engine, the X80 to prove the concept and work out the initial problems.

Almost all piston aircraft engines use a dual ignition and two spark plugs per cylinder. This is not normally used in automotive applications. Aside from the "backup", with the large cylinders of the big aircraft engines, dual progression of the flame front is necessary to avoid detonation which would not occur with the smaller automotive cylinders.

Another aviation pioneer was Leroy Grumman, a legitimate thinker and test pilot in his own right. He flew a captured FW190 and was reported to say "this is the plane we should have built, referring to the F6F. The result was the superlative F8F Bearcat.

Looking forward to the Reporter!

T
 
Once again one or two weeks go by and you start to wonder just whatever happened to this project..

Sometimes its really hard to tell from all the side comments if a project is nearing completion or not.

So, how about an update?? :very_drunk: :bump:
 
This is not normally used in automotive applications.
Click to expand...
Normally, no, but my ex had a 80-something Nissan 4WD pickup that had a dual spark plug system. 4 cylinders, 8 plugs, a huge (for this size engine) distributer cap, 8 separate wires, the whole nine. It was a royal PITA to time, and ensuring the right wire went to the right plug, AND was routed correctly was a nightmare. The plugs fouled all the time, too, but that was the way she drove. Honestly, the 75 Impala with a nice V-8 I bought her (before we split up) was more fun to work on. I was SO glad she rolled it down the canal bank we lived on during a heavy rain one day. That colichi clay is slicker than greased ice, when it's good-n-wet.
Totaled the truck, and she hadn't payed her insurance (hehehehe...).

Have fun all
Pat☺
 
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