Dec 1941. Long range day fighter.

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But would you agree that if we could field an a/c with a top speed of 380 mph and a range of 1200 miles, with an armament of 4 x 50s we have the makings of the original specification
 
Probably we would, it will need a drop tank facility though (not that is a rocket science - US and German aircraft were using external tanks in the mid-1930s).
 
I would also note that most, if not all, of the extra power is going to go into trying to shove those Cyclone 9s through the air. At least until you get close to 25,000ft.
A F4U-1 Corsair could make 380mph at 18,000ft using normal (max continuous) power of 1650hp at 11,194lbs.
The Corsair is armed, has ammo, armor and self sealing fuel tanks. It was the prototype Corsairs performance that lead to the cancellation of the F5F program.

Another picture;

Now what shape was the F5F in when it made the numbers in the report?
The plane had been modified to the shape in the photo by July 24th 1941.
You have the frontal area of the two engines plus the fuselage which is going to be much greater than the frontal area of either an F6F or P-47. Twin engine planes need more power than a single engine plane to get the same performance. Lockheed, as a rough guess, figured they needed 2000hp in a twin (what would become the P-38) to equal a singe engine plane with a 1500hp engine (no single 1500hp engine existed when they started design work).

And we don't really KNOW for certain what power was used for the speed numbers. The report doesn't actually say.
"Normal power" was either max continuous ( until the fuel ran out) or a 30 minute rating or 1 hour rating depending on the date of the test and the engine.
Take-off power was limited to 1 minute or sometimes 5 minutes.
very seldom 3 minutes
Take-off power limits were adopted as "military" power in many cases.
A lot of these ratings changed from 1938-41 to 1944/45.
Army and Navy tests were not always the same in the same time period.
Tests for the YP-43 were done using take-off or military power for speed runs.
 
parsifal said:
But would you agree that if we could field an a/c with a top speed of 380 mph and a range of 1200 miles, with an armament of 4 x 50s we have the makings of the original specification
Click to expand...

Unfortunately the F5F made the speeds listed with 178 US gallons of fuel or only about 20 gallons more than a Whirlwind. Total fuel capacity was 277 US gallons (all in unprotected tanks) and while the extra fuel only knocked 1-2mph of the speed it added over a full minute to the climb to 20,000ft or 10.5 minutes. Just the extra 100 gallons added 1.2 minutes to the climb.
Add 286lbs for four .50s and 360-516lbs of ammo (516lbs is for 1720 rounds, 430 rpg) add armor and add 250-350lbs for fuel protection and the climb rate is heading for dismal pretty quick even if slightly better engines are fitted.

The twin concept gets shaky when you figure that just the bare engines weigh bit over 2600lbs while a 2 stage supercharged R-2800 weighs about 2470lbs. the props on the R-1820s are going to go over 300lbs apiece (with turbo props going more) while the 3 blade props on F4Us and F6Fs were under 500lbs, same for some of the other engine bits and pieces. The twin is hauling several hundred more pounds of engine installation and has more drag. IF you don't have a big enough engine to get a single to do what you want then a twin is the way to go. But two small engines do NOT equal a big single.
 
Be careful about interpreting Flat Plate drag.

The equation for it is D/q=Cd*S. So, D = Total Drag, q= 1/2*rho*V^^2 and S= wing area. At low airspeeds, same for each ship at same altitude, it is a 'good' number

At low airspeeds it is useful when doing Kentucky windage drag comparisons but drag rise really grows from less than 0.02% at 0.35 M to major significance moving from say, 0.5M through .6M and beyond. The aero theory is elegant for incompressible fluids - which starts to be less compressible at approximately 0.35M. For 0.55M the P-38 is already getting tagged with a 1.2 factor compared to a P-51's 1.12 for low CL (level flight).

The compressibility factor applied to each a/c's Parasite Drag is much more severe for the P-38 at 400 mph than either the F6F or F4U and far more than the P-51B/D/H. Flat Plate Drag at 400mph drops the P-38 to the bottom of the comparison because of the fat wing's behavior at high speed - worse than F6F and F4U, and far worse than P-51 and P-47

Every CDo that is presented in most sources is a built up Parasite Drag delta for the major and minor airframe components, including the form/protuberance drag, the friction drag, drag due to gaps (like open wheel well or flap/wing interface) and presented usually at low airspeeds with RN> 5x10^^-6 up to 20x10^^6.

For a Mustang, the RN=20x10^^6 is about 180mph. For RN=5x10^^-6 the flow is near laminar/turbulent boundary at 80mph
 
Could those big bulky radial cowlings have been so close to the fuselage that the airflow patterns interfered with each other so that their total combined drag was more than just their individual drag added together ?

Sort of like triplane wings interfering with each others lift flow.
 
Thank you Drgondog,

Flat plate may work fairly well at speeds around climbing speed, you would know much better than I.
The F5F's climb numbers (time to altitude) seem pretty poor for the power available and the power has to be going somewhere (being used for something) or the propellers were pretty poor.
A Corsair may be using 250-300hp just to fly straight and level at around 180-200mph. If the F5F was using more power just to fly at that speed it may explain were some of the power/performance went.

Planes may swap around a bit on a list of least to greatest drag as the speed goes up and comprehensibility comes into play but it takes a mighty slick design to have a twin have less drag than a Single.

The Wright R-1820 was one of the largest diameter piston engine used in aviation pretty much matching the The R-3350, the R-4360 and the Bristol Centaurus. Trouble is they all produced roughly double the power (or more) for the same frontal area.
 

I certainly agree with almost everything you have said here and I certainly don't think the XF5F would be a better fighting machine than an F6F or F4U. But, what it could have been was developed and in the fighting day 1 before the F6F and F4U were deployed. I don't see it as a replacement for the F6F and F4U, I think it should have been developed instead of the F4F.

I would use turbocharged P&W 1830's instead of Wright Cyclones due to smaller frontal area.

I don't believe climb would have been as dismal as you portray it.

Overload fighter weight with 277 gallons of fuel 10,892 pounds
add 200 pounds of armor plate and bullet proof glass
add 800 pounds of weapons and ammo
add 350 for self sealing fuel tanks

total weight XF5F Skyrocket overload 12,242 pounds with 2,400 hp 0-25,000 feet
total weight Hellcat F6F-3 overload 12,243 pounds 1900 hp sea level 1650 25,000
total weight Corsair F4U-1 overload 12,656

The Skyrockets weight would be identical to the Hellcat and slightly lighter than the Corsair with 2,400 hp flat rated to 25,000 feet. I can't see why it would climb any worse than these 2


(FYI Shortround, I have great respect for your knowledge on these subjects even though I disagree with your opinion on this one)
 

The P-38 certainly have had the issues with pod and nacele creting the venturi. Execrpts from flight manual: link.
 
Over the course of the summer of 1941, the XF5F was tested against several other types:
F2A, F4F, XF4U, XFL-1, P-39, P-40, Hurricane and Spitfire. The pilots were to fly a specific set of maneuvers and then submit a report at the conclusion of the specific test. One of the Navy pilots, LtCdr. Crommelin remarked on the XF5F:
"I remember testing against XF4U in a climb to 10,000' - I pulled away from the Corsair so fast I thought he was having engine trouble. F5F was a carrier pilot's dream, opposite-rotating props eliminated all torque, and you had no engine in front to look around to see the LSO."

Grumman's test pilot, "Connie" Converse, recalled in his memoirs:
"The flying qualities for the XF5F-1 were good overall. The counter-rotating props were a nice feature, virtually eliminating the torque effect on takeoff. Single-engine performance was good, rudder forces tended to be high in single engine configuration. Spin recovery was positive but elevator forces required for recovery were unusually high. All acrobatics were easily performed, and of course forward visibility was excellent."
 
Well this is interesting:

The XF5F Skyrocket is faster at 4,500 feet (326 mph on 1,000 hp per engine) than a P38D at 5,000 feet (322 mph on 1,150 hp per engine at 3,000 rpm or 319.5 mph on 1,000 hp at 2,600 rpm)

So the XF5F is 6mph faster at 4,500 feet than a P38 at 5000 feet on the same 1,000 hp per engine.

Perhaps the XP50 showing 424 mph at 20,000 is correct after all
 
you guys just amaze me with this stuff..

So, say we have a fighter, based around the F5F, that has a range of 1200miles a top speed of 380 mph, climb rate okay but not great, 4 x 0.5" HMGs, pilot armour and self sealing tanks. These aircraft have probably been re- engined since the prototype, streamlined and the bugs worked out. its a workable design. They are now starting to come off the production lines, and in the ETO by May 42 could be expected to have 2-300 of these suckers, hopefully sent to the RAF who are the only one really in apposition to use these things.

by comparison, the germans have adopted one of two alternative responses. They can either maintain their current (historical) force structure, which would see about 150 me109s and FW190s ranged against them, or the Germans might have gone for their wonder weapon the FW187. If they go for the 187, one should assume they solve its many shortcomings and have an effective fighter. how effective Im not sure.....but one thing would occur, with a change over in production the germans would lose their FW 190s or some of their Me 109s and might have half as many of these new fighters to replace them...

How would a force of 250 lr F5Fs fare against 150 Me109s, or 75 FW 187s, assuming both of the hypothetical types have had their respective "kinks" ironed out?
 

Personally, I would be MUCH more inclined to used the XF5F as it was originally intended, as a carrier born fighter in the Pacific, not in Europe.

Back to climb rate, since the XF5F would weigh about 12,000 pounds in overload condition, about 11,200 in normal condition (while using 1,200 hp turbocharged engines) shouldn't it easily out-climb the P38D which should weigh 14,000 or so on 1,150 hp per engine? The P38D would out climb a Spitfire according to this document:

http://www.wwiiaircraftperformance.org/P-40/PHQ-M-19-1307-A.pdf

"The P38D can out climb the Spitfire at any altitude and is faster, its margin of performance increases with altitude over the Spitfire"
 
But Michael,
How is that any different than the historical timeline of the P-38, as the YP-38 was in development and subsequently delivered during the same time period? As it happend, the G-41 (XP-50) was a prime consideration in the competition for the Circular Proposal 39-775 issued in 1939, which Lockheed's model 522 won.

As a result of that competition, the Evaluation Board met at Wright Field on 4 August 1939 and placed an order for 66 Lockheeds and 41 Grummans. It was at that time that the P-38 and the P-50 were given their designations. In October 1939, negotiations for the contract were worked on, slight modifications were requested, and work got under way on the airframe by November 1939. A projected delivery date was set for 17 December 1940.

So in view of the early start on the P-50, we can see that the USAAC was impressed by the aircraft's potential and were serious about it's aquisition.

But due to several setabacks and a twist of fate, the P-38's rival quietly faded from view.

Almost forgot to mention: the XP-50 was designed to have two 20mm cannon and two .50 MG in the nose, with a proposal for two additional .50 MG, one in each outboard wing. The initial arrangement is really no different than the P-38's four nose-mounted weapons, which proved to be deadly as they were centerlined with no convergance issues and a good supply of ammunition for each MG.

So even if, by some chance, they decided to install only four .50 MGs in the P-50's nose, it would have produced just as much damage as the P-38 was capable of.
 
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We have the anecdote of the climb performance at odds with test results as written in the report. there is a least one typo on that data sheet, there could be more.
We also seem to have a problem with power levels. A number of aircraft were supposed to have rather startling climb performance based on their initial rate of climb but rather mediocre (if not poor performance) if based on time to altitude. Curtiss CW-21 for one and the Bell XP-77 for another.
IF the test pilot used take-off power settings (RPM and boost) for 1 minute or more he might be able to get some rather good performance from plane X, vrs climbing at the 'book' rate using max continuous power. Actual power levels might be lower than book levels due to poor ram from intake or having to restrict power due to engine temperature ( F5F did have trouble with cooling and 9 to 10 minutes of hard climbing is the worst for cooling.)

Against the XF4U and trying to compare that to service F4Us you have the fact that the XF4U went through several different engines during it's life and while the prototype was lighter than Service models the early experimental engines were also making 100-150hp less at most altitudes. Maybe it got a later engine by the summer of 1941, maybe not.

The test report gives an extra 1.2 minutes to 20,000ft with the extra 100gallons of fuel, adding another 1000lb to the planes weight for "service" equipment is just going to make things that much worse. Comparing power to weight of other planes doesn't do us much good unless we can figure out WHY the F5F was climbing so badly in the test results.
 
I would be more than a bit leary of the US Navy "Normal" vs "Overload" conditions as the "Normal" weight was with less than full internal tanks (fair enough at certain points during the war (pre drop tanks) as fuel is burned taking off and climbing to altitude) but often used either reduced armament or reduced ammo. For instance for the F6F not only is the plane at "normal" weight only carrying 182 gallons (?) vrs the 250 gallon internal capacity but ammo was restricted to just 200rpg instead of the full 400rpg.
Sounds good and provides some decent numbers in tests but how often did US Navy fighters leave the carrier deck with 2/3s fuel and 1/2 ammo to perform intercepts? Granted it may give a better "idea" of capability on the 2nd or 3rd intercept.

As to actual effect a lot depends on timing. F4Us entered production in Aug of 1942 with 9 built, (2 had been built in July), 13 are built in Sept and 31 in Oct. First Squadron is formed and starts getting aircraft in Sept. They go into action in Mid Feb 1943.
If you want even 2-3 squadrons in service in Sept 1942 (forget Midway) Production would have had to start in in Feb or March.
If you want turbos please remember that the first 500 P-47s built ALL stayed in the US for use as trainers, in part due to turbo problems, P-43s were noted as having turbo problems as did early P-38s. Early B-17s had turbo problems, B-24s didn't get turbos until the C model of which 9 were built in Dec of 1941, The "D" model also with turbos was rolled out starting in late Jan/early Feb of 1942.
AS has been said before the main problem was not with the turbos themselves but with the turbo control that regulated the waste gate. Moisture in the exhaust would get into the pressure sensing tubes and then freeze causing major problems in controlling the turbo/s.
This early control measured the exhaust back pressure and regulated the opening of the waste gate to maintain a constant pressure in the exhaust system. This, it was thought, would cause the intake pressure to maintain a constant value at the carburetor intake. However a "frozen" control would either keep the waste gate in an Open position causing low pressure/low power or in a closed position causing higher than normal pressure and temperature at the carburetor. The pilot could obviously throttle back and control manifold pressure and power that way although he could do little about the high intake temperature.
Later controls measured the pressure in the intake system ahead of the carburetor and tried to automatically maintain it to just under 30in of mercury (sea level pressure) by controlling the wastegate and letting the exhaust pressure fluctuate as needed.

I would also note that the R-1830 engines used in the B-24C and D weighed about 1490-1500lbs for the "bare" engine, (not including turbo and certain accessories) while the R-1820 engines in the F5F weighed about 1315-1320lbs. Maybe the smaller diameter will make up for the extra weight?
 
Shortround - "Flat plate may work fairly well at speeds around climbing speed, you would know much better than I.
The F5F's climb numbers (time to altitude) seem pretty poor for the power available and the power has to be going somewhere (being used for something) or the propellers were pretty poor.
A Corsair may be using 250-300hp just to fly straight and level at around 180-200mph. If the F5F was using more power just to fly at that speed it may explain were some of the power/performance went.

Planes may swap around a bit on a list of least to greatest drag as the speed goes up and comprehensibility comes into play but it takes a mighty slick design to have a twin have less drag than a Single."

SR - it IS a good rule of thumb comparison but consider this. Form Drag due to angle of attack goes up dramatically at higher angles of attack (turn and climb) versus level flight - low AoA cruise or dash. In the example of a P-51D at sustained climb of 170mph TAS, the increase in parasite drag is ~ 65% with the Wing as the worst offender.

As to your comment about twin engine, the wetted area for friction drag for a twin is usually far higher than a comparable performing single engine fighter - usually as much or more as the wing..
 


Perhaps you can name any "kinks" of the Fw 187?!
In this forum were many threads on a very very professional level about the Fw 187, and there were not any kind of "kinks" with the normal DB 601 and a conventional cooling.
The Fw 187 had issues with the hot steam cooling which was experimental.
At Dec 1941 the Fw 187 would be on 2 x Db 601E with 2700PS and around 670km/h at* 6000m high speed and a climb performance at 18-19m/s with 4 x 20mm guns.
 
If you took the time to read those "professional level" discussions, you would have noticed that the Fw187 had a series of "kimks" that needed ironing out.

First "kink" was the dangerous flutter in the rudder experienced in V1, eventually resulting in failure.

The next "kink" was the discovery of the weak landing gear design, which failed for V2 and V3.

The biggest "kink" was the insistance that the Fw187 be a two seater, then a three seater. Another "kink" was the insistance of using Jumos, not the DB engines. Then they wanted it to be a bomber, then a night fighter...

So there were a great deal of kinks in the program.

And V6 was the only one with the evaporitve cooling, it also is the only one that had the DB600 engines, which was the original design specification along with retractable radiators - not the DB601. The short production run had Jumo 210G engines with conventional radiators.
 

1. No the leading engineer has mounted a weight to the rudders, because of fail calculations, which was totaly unnecessary (Amazon product ASIN 0764318713View: http://www.amazon.com/gp/product/0764318713?keywords=Fw%20187&qid=1456105951&ref_=sr_1_1&sr=8-1
)

2. There was no single issue about the landing gear!
(Amazon product ASIN 0764318713View: http://www.amazon.com/gp/product/0764318713?keywords=Fw%20187&qid=1456105951&ref_=sr_1_1&sr=8-1
)

3. To my knowledge and any source I have read, there were NOT any plans of a three seater, that is totaly crap. Also the Fw 187 was only planed with DB engines.
(Amazon product ASIN 0764318713View: http://www.amazon.com/gp/product/0764318713?keywords=Fw%20187&qid=1456105951&ref_=sr_1_1&sr=8-1
)

DB 601 V, DB 601, Db 605 etc. The Jumo 210 engines were only installed, because of the shortage of the DB engines for war efforts.
 
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