P-47: We could easily out-turn the Jerry

[Angus]

Well, the 109 Speeds seem to have been closely the same in 1942 as in 1944 if we take 670 km/h for the 109F for instance...

[gwshaw]

Originally posted by bozon
Johnson claims his D-5 was boosted up to 72". I wonder how it translates into HP. If it's anything resembling the "C" figures posted here than it would be 2800-3000 HP !
Bozon

If he stayed at the 2700 rpm that the A series were cleared for, 72 in Hg would be 2760 hp, charge cooling from water injection would bump that up a bit too. I don't have enough info to calculate charge air temps to make a valid comparison. SWAG, 1.1 * 2760 = 3035 hp on the high end, 1.05 * 2760 = 2900 hp on the low end.

If Widewing or someone has diameters and rpm limits for the C series turbo-superchargers I could make a more accurate estimate. I'm inclined towards the high end, it matches the 3000 hp @ 2800 rpm & 73 in Hg listed earlier pretty closely.

(edit)
Brain fart, the low end is a better match. Didn't take into account the difference between 2800 rpm & 2700 rpm. HoHun's 2850 interpolation doesn't take into account the lower slightly lower power draw at 2700 rpm for the integral blower and other accessories. So somewhere in the 2875 hp range would probably be accurate enough.
(/edit)

On a clean D-5 w/o wingracks or belly rack that should make 475 mph @ 35k realistic, if the earlier model turbo-supercharger could manage that high an altitude.

Greg Shaw

[gwshaw]

Originally posted by Kurfürst
It`s an actual test afaik, and results are what they are. Certainly quite a few P-47s were received by the Red Air Force, and they tested them of course. I`d like to see some evidence to the contrary, because it`s seems to me very unlikely that despite the stronger engines, better propellors, etc., the speeds were the same in 1942 as in 1944. All sources I have seen so far shows the early P-47s at 663kph max.

I was referring to the Pony's speed being about 30 km/h too low, not the P-47. The 410 mph range is probably about right for an early model Razorback running at 52 in Hg (2000 hp), when outfitted with the bulged belly and shackles. My read on the P-47 C/D history is that the WEP increases barely offset the increased drag from belly shackles, wing racks, new canopy and rocket rails, etc... Meaning practical speed stayed in the 420-435 mph range, despite significant increases in power. Difference being that the D-40 could manage 435 mph with all the crap hanging off it, while an original D-5 could only do about 420-425 clean.

Greg Shaw

[HoHun]

Hi Bozon,

>Johnson claims his D-5 was boosted up to 72". I wonder how it translates into HP. If it's anything resembling the "C" figures posted here than it would be 2800-3000 HP !

Approximation for 2700 rpm/72" Hg:

3000 HP * 2700 rpm/2800 rpm * 72" Hg/73" Hg = ca. 2850 HP

>I can almost hear the whines had the AH D-11 would have a paddle blade prop and 600HP to spare.

Hm, I'd say the shorter blades should make the toothpick propeller superior at higher speeds due to smaller tip speed losses. On the other hand, it seems possible that the tootpick had not enough area to actually transfer all that power, in which case the tip speed question becomes academic.

The problem with the 72" Hg setting on the early R-2800 is that it would have a lower critical altitude. From the Power Plant Chart in AN 01-65BC-1A (for the "P-47D-25 through P-47D-35", engine model "R-2800 'B' Series"), critical altitude was 34000 ft for 52" Hg and 26000 ft for 64" Hg, so it should be 20700 ft for 72" Hg, using the same linear extrapolation as evident in the R-2800-56(C) data.

(It might not be perfectly accurate as the higher power should generate more exhaust gases to spin the turbosupercharger faster, unless it's already at its limit, which it might be. Take it as an approximation. Altitude is given in 2000 ft steps anyway, so it definitely has only limited accuracy.)

Unfortunately, I'm not certain whether the altitudes are given including ram effect or not. The layout of the engine chart coincedes exactly with that of the flight operation chart for level flight, so I'd guess ram is included, but that's only a guess so far.

To sum it up, the problem with Johnson's figures is that they are for rather high altitude while 72" Hg would be available only at a rather low altitude, even on the "C" engine which he (probably) didn't have available. That doesn't appear logical from the current state of my analysis.

Applying the same rpm/boost comparison technique as above, I get the following data for the R-2800 B series, based on maximum output of the C series:

44" Hg/2700 rpm: 1570 HP (maximum continous)
52" Hg/2700 rpm: 2060 HP (MIL, 15 min)
64" Hg/2700 rpm: 2536 HP (WEP, 5 min)
72" Hg/2700 rpm: 2850 HP (Johnson)

(Wow! 2535 is mentioned in some books :-)

Since 2300 HP are quoted sometimes, it's interesting to see that they are achieved at a nice round 60" Hg:

60" Hg/2700 rpm: 2300 HP

So one might speculate:

- 52" Hg/2700 rpm was the standard MIL without water injection, and probably is equivalent to the well-known rated 2000 HP.

- 60" Hg/2700 rpm was introduced with the first water injection models

- 64" Hg/2700 rpm was introduced with the P-47D-25 (or earlier) and offered higher power, also at water injection.

With regard to 60" Hg/64" Hg: I have seen both 15 gallon and 30 gallon water tanks mentioned, maybe the larger size coincedes with the higher rating?

MIL obviously does not use water injection since it uses 4.67 gal/min while WEP uses only 4.16 gal/min (plus water/alcohol, of course). Specific fuel consumption usually drops with water consumption, so that's a telltale mark for its use.

Now if we could connect the different powers with different R-2800 dash numbers, we'd have made a good step forward in solving the Thunderbolt puzzle :-)

Regards,

Henning (HoHun)

[frank3]

Well now to make a long story short, no matter how fast it's opponent is, the Thunderbolt could always 'end the fight'

[StarOfAfrica2]

Originally posted by Rino
I know this is annecdotal, especially since I cannot remember
the book I read it in, but the Jugs were able to use a "trick" to
outturn 109s and 190s as well.

     It was called the lag pursuit roll, basically you roll opposite
the bandit's turn 270 degrees, then pull in behind him using
your elevators.  Because it allowed more seperation between
the aircraft, the P-47 was able to slow a bit and turn inside
the german aircraft.

Lag roll is useful in any plane like that, i.e. one that doesnt turn as well as their opponent.  FW's use it alot also.  Say you are in a Jug or a FW and chasing a spit.  He goes into a hard flat turn to the left.  Instead of trying to follow him, you roll to the right and when you come around 270 degrees in your roll you pull out facing the spit (hopefully) at about 90 degrees from where he started his turn.  It requires a plane with a good roll rate, proper timing, and not overdoing the g-forces in the roll or you'll spin out.  The nice thing is, if you screw up the timing the spit is still committed to the turn and you can zoom out of the fight and get separation.  It will take him a bit to get around where he can chase you and by then you are out of range.  Get some space, get some alt, and try again.

[StarOfAfrica2]

Originally posted by HoHun

Do you have a set of data which lists speed, climb and power/critical altitude for one specific aircraft along with the weight? In analyzing P-47 performance, I have only found partial sets so far, which were partially contradictory.

Regards,

Henning (HoHun)

This page doesnt list all the things you asked for, and I'm not saying its 100% correct either, as I dont know what their sources were.  However, the information I have used from them in the past was verified by other sources, and I have always found them to be fairly reliable.

http://www.warbirdsresourcegroup.org/URG/p47.html

This is the summary from their "Remarks" section on the P-47 in general.

Remarks: The Thunderbolt, designed by Alexander Kartveli, developed a reputation during World War II for extreme toughness and the ability to return it's pilot home even after suffering staggering damage. Nicknamed the "Jug", the Thunderbolt was produced in astonishing number and became the USAAF's premier ground attack fighter-bomber. The type was also used by Brazil, the Free French air force, Mexico, the RAF, and the Soviet Union.
   An evolutionary development of the P-43 Lancer, the Thunderbolt entered service in June 1942 with the USAAF's 56th Fighter Group being the first unit to recieved the initial P-47B aircraft. This unit was attached to the 8th Air Force by January 1943 and joined by the 78th Fighter group became operational in April 1943.
   Initial engagements with the Luftwaffe showed severe shortcoming at low and medium altitudes and a insufficient fuel load for the escort mission. Later variants overcame these shortcomings and greatly increased the types capabilities. By war's end the Jug had achieved some remarkable statistics. The Thunderbolt managed to destoy 4.6 aircraft for every one of there own number shot down. While flying of half a million combat sorties, accumulating nearly two million operational hours, the type shot down 3,752 enemy aircraft as well as destroying 3,315 aircraft on the ground. It is little wonder that the type achieved such a legendary and highly respected status.
    The Jug remained in service with the Air National guard units until 1954 and in numerous air forces around the world for many years after.

[StarOfAfrica2]

I also thought this writeup was interesting, considering how poorly the P47 was supposed to perform "on the deck".  Its a personal recollection of Edwin Heller.

QUOTE: Describes his second victory on May 8th 1944 with, "This was the hairiest combat I was ever in. On this day Cutler was probably smiling in anticipation as the two of us turned to attack 20 plus 109's, but I was scared ****less. Anyway, when I got that second 109 down on the deck it was hairy as he would turn around buildings so I couldn't pull lead on him. Finally we got into a just-above-stalling Lufbery and it was him or me just a few feet above the ground. I was very thankful when he broke out and I got the final burst in. As I dove in to take a picture of him, my coolant boiled over and came right back on the windscreen. I pulled up and in reflex automatically jammed the coolant door open. I climbed to 10,000 feet, heading home, and made a blind call on the radio that I would most likely bail out, but that I got two 109's. We had been way south of Berlin, and I chose 10,000 feet as it was too high for the light stuff and too low for the big guns. I was real concerned that my engine would quit over the Channel, but she kept going and I got home with it. The tech rep couldn't believe I'd flown for two hours after popping my coolant. He surmised that I'd saved a fraction of coolant and it turned to steam, providing the necessary cooling to keep the engine from seizing up."

Here is a link to the page (interesting look at the flight history of a Jug pilot).

http://www.warbirdsresourcegroup.org/URG/heller.html

[Oldman731]

I add the following account from Roger A. Freeman’s Bible of 8th AF operations, “The Mighty Eighth,” at page 125.  Note altitudes.

This occurred on the March 6, 1944 mission to Berlin.  At the time Mahurin, of the 56th FG, had 16 victories:  

   Captain Walker Mahurin, leading Red Flight, said:  "At the time of the attack, we were unaware of the actual presence of the E/A.  We first noticed them when we began to see the flashes of the 20-mm shells bursting around the firsts division of bombers....by the time we got into the combat vicinity the concentrated attack had been dispersed leaving the E/A flying singly and in twos and threes down on the clouds at 7,000 feet.
   "I noticed three of these E/A about 11 o'clock to me down low:  after considerable manoeuvring, I was in a position to attack one of these E/A, a single Me109.  As I came down on him he saw me, and after one turn to the left, he headed down for the clouds.  I found myself closing on his tail.  I fired several short bursts, none of which hit him.  He finally disappeared into the clouds.
   "When I pulled up from this attack, I sighted a single FW190 at about 9 o'clock to my flight, heading down for the deck.  This Jerry also saw me.  As soon as the element of surprise was gone I knew I would be forced to follow him before he straightened out, before I could make a proper attack.  We milled around and around in a turning circle to the left, until suddenly the 190 straightened out and headed for one of the half-mile-in-diameter clouds which covered the area.  As he did so, I closed in behind him and started to fire.  By this time we were both in the cloud and it turned out to be considerably thinner than either one of us had anticipated.  I could still see the Hun, and when I fired I saw many hits on both of his wings, as well as a few on his fuselage.  I was close enough to him so that my hits did not converge to a point.  I was then forced to break off the attack as the cloud obscured him.  This 190 I claim as probably destroyed, because I hit him quite heavily.
   "By this time the flight had worked itself down to about 3,000 feet and were darting in and out of the clouds trying to spot more Huns.  The Huns were darting in and out of the clouds trying to evade Thunderbolts.
   "As we climbed back towards the bombers, I looked over the side of my ship and spotted a Thunderbolt in a turning circle to the left with an FW190 on its tail.  I immediately called on the R/T to tell the '47 to break left, however, I later discovered that it was a ship from the 78th Group and on a different frequency to ours.  I led the flight into attack the 190, which was all silver and with a large black "V" painted on its side.  He saw us coming, because he broke the attack and began to turn left to save his own hide.  I throttled back and closed in behind him, but held my fire until he, too, would straighten out.
   "In the turn itself I was only just able to stay with him, both of us would stall a bit and then recover.  However, when I added water I was able to out-turn him and also able to go around the circle faster than he did.  I got within 150 yards of him and stayed there.  After we had both gone around the circle several times, he pulled up into a steep climb.  I followed and was able to get in a few shots, as I closed on him in the climb.  As he fell off, he rolled over in order to pull the old stand-by of the Luftwaffe - the split S.  I followed this also, gaining on him in the dive.  When he pulled out of the dive he headed straight for the clouds in the same manner as the other Jerry had.  I was able to pepper him soundly, seeing many hits on both wings and fuselage.  The Jerry appeared to be having difficulty in flying his ship.  He made a 180 degree turn to the left, and as I pulled up I saw his canopy fly off and saw him jump over the side."

[HoHun]

Hi Star,

>However, the information I have used from them in the past was verified by other sources, and I have always found them to be fairly reliable.

>http://www.warbirdsresourcegroup.org/URG/p47.html

Roger, exactly that page was quite helpful in preparing a general overview :-) That's my data compilation from 3 sites (I checked out a dozen sites or more that didn't have any useful information):

P-47B

powerplant: Pratt & Whitney R-2800-21 2000hp*
12-foot 2-inch diameter Curtiss Electric C542S-A6 propeller***
weight, loaded: 12,245 lbs*
max speed: 429 mph at 27,000 ft*

P-47C

powerplant: Pratt & Whitney R-2800-21 2000hp WEP*
powerplant: Pratt & Whitney R-2800-59 2535hp WEP*
powerplant: Pratt & Whitney R-2800-59 2300hp**
Curtiss Electric C542S propeller, 12 ft 2 in diameter***
weight, loaded: 13,500 lbs*
max speed: 433 mph at 30,000 ft*

P-47D/G

powerplant: Pratt & Whitney R-2800-59/-63 2535hp WEP*
P&W R-2800-21W or -51W Double Wasp,  2,300 hp or 2,535 hp**
weight, loaded: 14,600 lbs*
max speed: 429 mph at 30,000 ft*

D-1, D-2, D-3: water injection retrofittable***
D-4-RA, D-5-RE, D-6-RE: R-2800-21, water injection, 15 gal, 2300 HP***
D-10-RE and D-11-RA: R-2800-63***
P-47D-20-RE: R-2800-59*** power same as -63, 2300 HP WEP***
P-47D-25-RE and P-47D-26-RA: First bubble top, paddle blade***
P-47D-27-RE: Dorsal fin***
P-47D-30-RA: Rockets***

P-47D-25-RE: R-2800-59 of 2535 hp. 429 mph at 30,000 feet, 406 mph at 20,000 feet, 375 mph at 10,000 feet, 350 mph at sea level. Initial climb rate was 2780 feet per minute. Climb rate at 30,000 feet was 1575 feet per minute. 14,600 pounds normal loaded***

P-47M

powerplant: Pratt & Whitney R-2800-57(C) 2800hp /w water injection*
weight, loaded: 13,275 lbs*
max speed: 400 mph at 10,000 ft, 453 mph at at 25,000 ft, and 470 mph at 30,000 ft*
rate of climb: 3500 ft per minute at 5000 ft and 2650 ft per minute at 20,000 ft*

P-47M-1-RE: 400 mph at 10,000 feet, 453 mph at at 25,000 feet, and 470 mph at 30,000 feet. Initial climb rate 3500 feet per minute at 5000 feet and 2650 feet per minute at 20,000 feet.***

P-47N

wing area: 322 sq ft*
powerplant: Pratt & Whitney R-2800-57(C)/-77 2800hp /w water injection*
weight, loaded: 16,300 lbs*
max speed: 397 mph at 10,000 ft, 448 mph at 25,000 ft, and 460 mph at 30,000 ft*
rate of climb: 2770 ft per minute at 5000 ft and 2550 ft per minute at 20,000 ft*

P-47N-5-RE: 397 mph at 10,000 feet, 448 mph at at 25,000 feet, and 460 mph at 30,000 feet. Initial climb rate was 2770 feet per minute at 5000 feet and 2550 feet per minute at 20,000 feet. 16,300 pounds normal loaded***

* http://www.ww2guide.com/p47.shtml
** http://www.warbirdsresourcegroup.org/URG/p47.html
***http://home.att.net/~jbaugher1/p47.html

Regards,

Henning (HoHun)

[HoHun]

Hi Star,

>I also thought this writeup was interesting, considering how poorly the P47 was supposed to perform "on the deck".  Its a personal recollection of Edwin Heller.

Hm, with coolant lines being hit and coolant boiling, wouldn't that description probably stem from a P-51 mission?

Regards,

Henning (HoHun)

[rshubert]

Originally posted by StarOfAfrica2
I also thought this writeup was interesting, considering how poorly the P47 was supposed to perform "on the deck".  Its a personal recollection of Edwin Heller.



Here is a link to the page (interesting look at the flight history of a Jug pilot).

http://www.warbirdsresourcegroup.org/URG/heller.html

Something's wrong here.  THe jug had an AIR cooled engine.  No coolant.   None.

Maybe this guy changed over to ponies?

[StarOfAfrica2]

He did.  My fault lol.

[HoHun]

Hi again,

Based on the data above, I have tried to figure out P-47 performance.

Here's one set of data based on the "Baugher" P-47D-25 (429 mph @ 30000 ft):

1570 HP: 613 km/h @ 12.0 km, initial climb 08.0 m/s*
2000 HP: 663 km/h @ 10.3 km, initial climb 11.6 m/s
2300 HP: 690 km/h @ 09.2 km, initial climb 14.0 m/s**
2535 HP: 703 km/h @ 08.3 km, initial climb 15.8 m/s
2850 HP: 716 km/h @ 07.3 km, initial climb 18.3 m/s***

*maximum continous
** Baugher's data point
***Johnson's settings, but D-25 airframe

The performance of the 2535 HP P-47D-25 is about the same as that of the P-51D with V-1650-7 at 67" Hg. The P-47D has a 10 km/h speed advantage from 8.5 km up, the P-51D has a speed advantage of 0 - 20 km/h below that.

Of course, results depend on the specific condition and equipment of each plane so only take this as a general impression :-)

The P-51B with a V-1650-3 should handily outperform the P-47D-25 at high altitude with a top speed of 724 km/h @ 8.9 km - 30 km/h faster than the Thunderbolt.

Of course, the Jug had twice the firepower :-)

Regards,

Henning (HoHun)

[Kurfürst]

Originally posted by HoHun


The P-51B with a V-1650-3 should handily outperform the P-47D-25 at high altitude with a top speed of 724 km/h @ 8.9 km - 30 km/h faster than the Thunderbolt.
 

Indeed, I think the statements on the P-47`s relative high alt performance are quite a bit overstated, or at least they are based on the late 1943, when they saw the most combat and Axis/Allied contemporaries were truly not as fast as it - something that changed in `44 with Spit XIVs, P-51Bs, late 109Gs/Ks.. ie. the high(er) manouveribility can be only true if the plane was considerably faster than the others, as regardless of the turbocharger, the thunderbolt had extremely high wingloading, making it unlikely to be as goodwilled as a spit when manouvering well above the clouds.

The numbers you posted on perfomance seem exactly right to me, btw.