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MarekGutkowski
11-03-2008, 03:21 AM
Something that I'm thinking about for some time now.
In history we have some examples of air frames with radial and inline engines, LaGG-3/ La-5,Yokosuka D4Y1/D4Y3,Focke-Wulf 190A/D and Kawasaki Ki-61/Ki-100
(there are more but ones that did not enter combat I'm omitting as there are not enough data on them) that I know of.
That are the best examples as Jug vs Mustang debate is not too useful for me as those were vastly different planes. Design with vastly different principles in mind,although both were long range escorts.

So far I have those pro's and con's on each engine

Radial engines have simple construction which in it self is an enormous bonus, less parts means less things to go wrong less things to make and maintain.
(Simple also means that when You shoot at it it wont blow up that easily)
Con that I know is that they have large frontal surface there of more drag, more drag equals to less speed.
Also some thing that is both pro and a con.
Air-cooling although it simple it also less effective that liquid-cooling.
Trying too increase it(cooling) effectiveness will also increase the mass dramatically.

Inline engines have smaller cross section(less drag etc...)
But are complicated and require liquid cooling.

That is all I know about the engine design it self.
As for practical application.
Inline engine powered planes performed better at altitude, many planes had a cannon up to 45mm in caliber firing thou propeller hub,some thing one cannot do in a radial powered plane.Inline engines are much less resistant to damage there cooling systems radiators and coolant lines can be destroyed and the whole engine will die.
That is not a problem with radials as they are air-cooled and don't have delicate cooling.

I found debates of inline vs radial with the Thunderbolt vs Mustang debates. Jug was better suited for ground attacks,P-47 had a heavier and tougher airframe and it was not all about the engine althou it helped.We cannot forget the Tempest a great British fighter by many consider best ground attack platform of WWII which had a liquid-cooled inline engine.Il-2 Sturmovik and it successor Il-10 also had inline engines.During the war soviets did make a radial powered Il-2 variant but supply problems with AM-82 engine force them to abandon the project,That may support the "Inline no good for attack plane" argument, but when the war was ending and a Il-10 successor was developed and there was no problems with radial engine supply, it retained the inline liquid cooled power plant.
As for In-line are better interceptors well J2M Raiden build from start as an interceptor had a radial engine, that is not saying much as it effectiveness was never proven or disproven for that matter.


As for the above mentioned planes with radial and inline power plants

LaGG-3 was a plane that had its down sides it was too heavy and was loosing air speed fast in continued maneuvers.Time and time again I found a claim that with attaching a AM-82 radial to the frame a poor fighter was made a great fighter.
What those who claim that are forgetting is that La-5FN the plane that outclassed early Bf-109G and Fw-190A's that had a long development behind it. It first incarnation the La-5 was considered inferior to LaGG as was it next model the La-5F only on the third try did the Lavochkin bested the LaGG-3 and the production of the in line variant was droped.

D4Y Suisei dive bomber with started it life with a in-line later was equipped with a radial that was do the fact that Aichi Atsuta engine was so hard to maintain(the fact that japanise personnel was not familiar with in-line liquid cooled engines didn't help)With the switch of the Atsuta for Kinsei the ceiling and rate of climb improved, higher fuel consumption resulted in shorter range and a slower cruise speed, while the bulky engine obstructed the forward and downward view of the pilot, hampering carrier operations.

As for the Focke-Wulf 190 perhaps the most famous engine switch in aviation history.The D model "was intended to improve on the high-altitude performance of the A-series enough to make it useful against the American heavy bombers of the era"and,compared with the FW 190A-8, Dora-9, had a greater level speed, climb rate, and ceiling.Was much quieter - the Jumo 213A vibrated much less than the BMW 801(It may appear unimportant but less noise less vibration less vibration the longer it will take for some thing to brake of.

The Kawasaki Ki-61-I was a good plane and it next version Ki-61-II equipped with an upgraded engine enterd production. Then a really annoying thing happened the factory that made He-140 engines got bombed by B-29,
So the jap's were sitting with a factory full of airframes with no engines for them. So they did the same thing they did with Judy they put a Keisei in it.
This aircraft build out of necessity turned out to be one of best fighter aircrafts of WWII.
Compared with Ki-61-II it was some 300kg lighter and had the same horse power, there for better everything apart from diving speed.

So do you have an opinion in this matter? Thank for the help.

MarekGutkowski
11-03-2008, 03:21 AM
Something that I'm thinking about for some time now.
In history we have some examples of air frames with radial and inline engines, LaGG-3/ La-5,Yokosuka D4Y1/D4Y3,Focke-Wulf 190A/D and Kawasaki Ki-61/Ki-100
(there are more but ones that did not enter combat I'm omitting as there are not enough data on them) that I know of.
That are the best examples as Jug vs Mustang debate is not too useful for me as those were vastly different planes. Design with vastly different principles in mind,although both were long range escorts.

So far I have those pro's and con's on each engine

Radial engines have simple construction which in it self is an enormous bonus, less parts means less things to go wrong less things to make and maintain.
(Simple also means that when You shoot at it it wont blow up that easily)
Con that I know is that they have large frontal surface there of more drag, more drag equals to less speed.
Also some thing that is both pro and a con.
Air-cooling although it simple it also less effective that liquid-cooling.
Trying too increase it(cooling) effectiveness will also increase the mass dramatically.

Inline engines have smaller cross section(less drag etc...)
But are complicated and require liquid cooling.

That is all I know about the engine design it self.
As for practical application.
Inline engine powered planes performed better at altitude, many planes had a cannon up to 45mm in caliber firing thou propeller hub,some thing one cannot do in a radial powered plane.Inline engines are much less resistant to damage there cooling systems radiators and coolant lines can be destroyed and the whole engine will die.
That is not a problem with radials as they are air-cooled and don't have delicate cooling.

I found debates of inline vs radial with the Thunderbolt vs Mustang debates. Jug was better suited for ground attacks,P-47 had a heavier and tougher airframe and it was not all about the engine althou it helped.We cannot forget the Tempest a great British fighter by many consider best ground attack platform of WWII which had a liquid-cooled inline engine.Il-2 Sturmovik and it successor Il-10 also had inline engines.During the war soviets did make a radial powered Il-2 variant but supply problems with AM-82 engine force them to abandon the project,That may support the "Inline no good for attack plane" argument, but when the war was ending and a Il-10 successor was developed and there was no problems with radial engine supply, it retained the inline liquid cooled power plant.
As for In-line are better interceptors well J2M Raiden build from start as an interceptor had a radial engine, that is not saying much as it effectiveness was never proven or disproven for that matter.


As for the above mentioned planes with radial and inline power plants

LaGG-3 was a plane that had its down sides it was too heavy and was loosing air speed fast in continued maneuvers.Time and time again I found a claim that with attaching a AM-82 radial to the frame a poor fighter was made a great fighter.
What those who claim that are forgetting is that La-5FN the plane that outclassed early Bf-109G and Fw-190A's that had a long development behind it. It first incarnation the La-5 was considered inferior to LaGG as was it next model the La-5F only on the third try did the Lavochkin bested the LaGG-3 and the production of the in line variant was droped.

D4Y Suisei dive bomber with started it life with a in-line later was equipped with a radial that was do the fact that Aichi Atsuta engine was so hard to maintain(the fact that japanise personnel was not familiar with in-line liquid cooled engines didn't help)With the switch of the Atsuta for Kinsei the ceiling and rate of climb improved, higher fuel consumption resulted in shorter range and a slower cruise speed, while the bulky engine obstructed the forward and downward view of the pilot, hampering carrier operations.

As for the Focke-Wulf 190 perhaps the most famous engine switch in aviation history.The D model "was intended to improve on the high-altitude performance of the A-series enough to make it useful against the American heavy bombers of the era"and,compared with the FW 190A-8, Dora-9, had a greater level speed, climb rate, and ceiling.Was much quieter - the Jumo 213A vibrated much less than the BMW 801(It may appear unimportant but less noise less vibration less vibration the longer it will take for some thing to brake of.

The Kawasaki Ki-61-I was a good plane and it next version Ki-61-II equipped with an upgraded engine enterd production. Then a really annoying thing happened the factory that made He-140 engines got bombed by B-29,
So the jap's were sitting with a factory full of airframes with no engines for them. So they did the same thing they did with Judy they put a Keisei in it.
This aircraft build out of necessity turned out to be one of best fighter aircrafts of WWII.
Compared with Ki-61-II it was some 300kg lighter and had the same horse power, there for better everything apart from diving speed.

So do you have an opinion in this matter? Thank for the help.

Freiwillige
11-03-2008, 05:15 AM
Originaly during the late thirty's the common thought was that inline engines producing less drag was the future. Hence the Spitfire and the 109 came out of this very thought process. When Kurt Tank built the FW-190 he only had a choice of Radial engines because all Diamler benz 601 inlines were already slated for the 109. So he built the most aerodynmic cowling he could and reduced the drag on the 801 coupling that with the great power of the new power plant and proved that aircooling still could be used effectivly.
The P-47 with its massive turbosupercharger was an aircooled desighn that boasted superior high altitude performance to its inline bretheren.

I think that most pacific fighters were aircooled given the simplicity of aircooled engines over inline and in general their better low alt. performance.

But in the end one has to conclude that it really is apples and oranges in that either style could be built into a competent frame and be givin performance to match the necesity.

Xiolablu3
11-03-2008, 05:47 AM
The aerodynamic cowling never really worked for the Fw190 and it was abvandoned.

The Fw190 had severe overheating problems in its early days.

The Tempests Sabre had a sleeve vavle engine, does this make it any more resistant to frontal damage? I dont know...

HuninMunin
11-03-2008, 06:23 AM
The cowling of the 190 was the best radial engine fitting of the period.
And highly influential to all later designs.
What was abandoned was the conical prop spinner plate.
The cowling is the stuff that's wrapped around the engine.

MarekGutkowski
11-03-2008, 08:06 AM
Are there any other down sides for a radial powered plane beside bigger drag?Did the overheating problem appear on all double row radials or was it more of a Focke-Wulf issue?

I'm asking as the more I think about the matter the less reasons I find that actually say that an in-line power plant for aircraft is good idea. Right now I'm thinking that, there is no thing that a in-line can do that a radial can't do better.

Freiwillige
11-03-2008, 10:13 AM
The famous FW-190 overheating problem actually comes from the first 190 prototypes using the BMW 139 motor. Its not that the engine was overheating so much (although the first cooling system was deemed inadiquate) but the Originall 190 desighn had the cockpit right up against the engine. Problems with the cockpit location, directly behind the engine, resulted in a cockpit that became uncomfortably hot. During the first flight, the temperature reached 55?C (131?F), after which Focke Wulf's chief test pilot, Hans Sander commented: "It was like sitting with both feet in the fireplace."

The RLM persuaded Tank to focus on the BMW 801 being just devoloped

The 801 engine was similar in diameter to the 139, although it was heavier and longer by a considerable margin. This required Tank to redesign the Fw 190, as a result of which the V3 and V4 were abandoned and the V5 became the first prototype with the new engine. Much of the airframe was strengthened and the cockpit was moved back in the fuselage, which reduced the troubles with high temperatures and for the first time provided space for nose armament.

crucislancer
11-03-2008, 10:30 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Xiolablu3:
The Tempests Sabre had a sleeve vavle engine, does this make it any more resistant to frontal damage? I dont know... </div></BLOCKQUOTE>

Not really. It seems that engine damage is my #1 cause for having to bail out of the Tempest. It's not as bad as the Mustang, but it's still bad.

general_kalle
11-03-2008, 10:31 AM
one thing ive never understood is why the inline was so much for fragile than the radial..
with the big open hole into the engine itself on the front you would think that a few bullets in there could cause tremendeus damage where's the enclosed and maybe armored metal around the inline would protekt it better. especially from frontal attacks.

DrHerb
11-03-2008, 10:43 AM
The fastest Propellor driven fighter (Bearcat) was powered by a Radial Engine.

Inline engines are inherently heavier than radials due to radiator plumbing and radiators.

Radials are also capable of making more horsepower than inlines by adding more cylinders and not taking up as much frontal length.

They are less likely to overheat on ground running as well.

PLUS Radials sound better than inlines http://forums.ubi.com/images/smilies/16x16_smiley-tongue.gif

Mr_Zooly
11-03-2008, 10:53 AM
@ General_Kalle
inline engines weakness was the cooling system (when damaged and the coolant leaked dry the engine overheated to the point of destruction), the radial engine was air cooled (air passes through the engine) which negates the need for liquid coolant).
Also the radial was better\quicker at slowing down which could be an advantage in combat.

Pyrres
11-03-2008, 10:54 AM
Maybe becouse the cylinder block deformed from impacts and it could not run anymore, things were all in one big block of iron and if it was hit it deformed and parts could not move. And the main thing was the cooling system, when radial gets one cylinder shot of it does not lose coolant, cause it has no coolant. When inline gets shot it many times start to loose coolant, without coolant those high power engines canĀ“t run that long.

PanzerAce2.0
11-03-2008, 01:50 PM
The problem with a radial is that if you lose one cylinder, you could very easily lose that entire row. I was reading about a guy racing in the Reno Unlimiteds, lost one of this con rods, and when he landed and stuck his hand through a hole in the block, he discovered that the entire front row had been destroyed/fallen out of the plane.

Bremspropeller
11-03-2008, 02:54 PM
+1 DrHerb http://forums.ubi.com/images/smilies/25.gif

The 190A DID have overheating-problems.
It took a few months in-service to get rid of the problems.
The engine reached a good reliability-record with the definitive BMW 801D-2 engine which was first used in A-3s.

The C-1 and C-2 engines still had a habit of running a little hot and failing every once in a while.


One gotta say the 190 made "strange" noises in-flight. The engine was running a bit rough and the sound of the supercharger switching was like "somebody shifted a heavy truck without hitting the clutch-pedal".
But pilots got used to it and a couple of 190s made their way back over the channel with their engines badly messd up by enemy-fire.

Overall a radial engine certainly is the better coice.

Aaron_GT
11-03-2008, 03:09 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">The fastest Propellor driven fighter (Bearcat) was powered by a Radial Engine. </div></BLOCKQUOTE>

The fastest prop plane is the Tu-94 in absolute terms, with turboprops. The Rare Bear F8F holds the piston low altitude record (which is the way the record is judged), with the previous holder being from an inline engine.

The record is at very low altitude, max 245 ft above sea level, so I'm not sure it would beat some other prop planes at high altitude as it lacks the turbosupercharging of, say, the P-47. I would suspect that if you took a P-47N and further optmised it it would beat the F8F at altitude although to be honest any of the late war prop designs with power eggs optimised for altitude (which rules out the F8F) would end up with very similar top speeds as the limiting factor would be airframe aerodynamics (mach limits).

In fact if you look at the maximums of those late war planes then, fully corrected for pitot issues, they are all doing 485 +-10 mph.

Aaron_GT
11-03-2008, 03:22 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Radials are also capable of making more horsepower than inlines by adding more cylinders and not taking up as much frontal length. </div></BLOCKQUOTE>

I'm unconvinced. The most powerful radials and inline aero engines run up both topped out at 5500hp. Adding additional cylinders to an air cooled inline by adding additional rows has a limit due to air cooling. Four rows seems to be the practical limit on this and makes the engine long. Adding additional cyclinders around the circumference also has a practical limit. In theory a liquid cooled inline could add more cylinders as required as long as the liquid could remove the heat and be cooled.

In the end the limiting factors are things like the ability to construct crankshaft and propellor combinations to be able to absorb the power, and that's a limit for turbprops too, and they don't tend to have greater shp than the big piston engines.

Aaron_GT
11-03-2008, 03:23 PM
Remember, there have been a few (if not very successful) inline air cooled engines (e.g. the Exe).

Rwulf__68
11-03-2008, 03:38 PM
I was speaking recently to a ex-Fleet Air Arm pilot who fly the Swordfish for over a decade through choice- the Sea Fury was too much work as he was also running Yeovilton. We talked about a great many aspects of flying & I felt that tellling him about Il2 was not quite right at that time- odd I know.


Anyway regarding radial engines, the main point he made that I recall was that you get near instant power with a radial, which when ye need to go around again on the flight deck is a tremendous advantage. Fuel economy of inlines tended to be a bit better though.

Will pop in with more memories as the threads seem fit.

DrHerb
11-03-2008, 05:08 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Aaron_GT:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Radials are also capable of making more horsepower than inlines by adding more cylinders and not taking up as much frontal length. </div></BLOCKQUOTE>

I'm unconvinced. The most powerful radials and inline aero engines run up both topped out at 5500hp. Adding additional cylinders to an air cooled inline by adding additional rows has a limit due to air cooling. Four rows seems to be the practical limit on this and makes the engine long. Adding additional cyclinders around the circumference also has a practical limit. In theory a liquid cooled inline could add more cylinders as required as long as the liquid could remove the heat and be cooled.

In the end the limiting factors are things like the ability to construct crankshaft and propellor combinations to be able to absorb the power, and that's a limit for turbprops too, and they don't tend to have greater shp than the big piston engines. </div></BLOCKQUOTE>

Turboprops are slightly against the spirit of this thread but Ive worked on GE T-64 turboprops that were fitted on DHC-5 Buffalos, that engine is capable of 4,750 shp.

Later Pratt & whitneys R-4360 got 4300 hp after adding on 2 large turbochargers on top of using a supercharger. However, no R-4360's have been mounted on fighters as far as i know.

stalkervision
11-03-2008, 05:19 PM
Very hard to turbo charge radials. Withness the p-47's size! http://forums.ubi.com/groupee_common/emoticons/icon_eek.gif

Aaron_GT
11-03-2008, 05:37 PM
Yes, turbprops, in terms of shp, seem to have topped out at the same point as piston engines, pretty much, and I am presuming that this is due to practical/cost-effective limits on shafts and props, although there are a few of those funky flower props.

Part of the reason why there probably weren't any production liquid-cooled inlines to rival the R-4360 was because one of the big firms developing inlines was Rolls-Royce and it abandoned the Eagle in favour of jets and turboprops. Ditto Napier. That only really left Allison but orders were cut after WW2 and their engines weren't then in many planes, and it moved out of piston engines too.

The likes of the late inline engines like the later Sabres have better hp/lb dry weight than the big radials and with smaller displacement although I am not sure what the total package weight would be (engine, oil, coolant, radiators, superchargers, etc and fuel for a given hp rating for a given time with rammed air for a given airspeed).

R_Target
11-03-2008, 07:02 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by DrHerb:
Later Pratt & whitneys R-4360 got 4300 hp after adding on 2 large turbochargers on top of using a supercharger. However, no R-4360's have been mounted on fighters as far as i know. </div></BLOCKQUOTE>

F2G Corsairs used the R-4360 "corncob." Of course they only made ten of them.

Crikey2008
11-03-2008, 08:54 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Aaron_GT:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">The fastest Propellor driven fighter (Bearcat) was powered by a Radial Engine. </div></BLOCKQUOTE>

The fastest prop plane is the Tu-94 in absolute terms, with turboprops. The Rare Bear F8F holds the piston low altitude record (which is the way the record is judged), with the previous holder being from an inline engine.

The record is at very low altitude, max 245 ft above sea level, so I'm not sure it would beat some other prop planes at high altitude as it lacks the turbosupercharging of, say, the P-47. I would suspect that if you took a P-47N and further optmised it it would beat the F8F at altitude although to be honest any of the late war prop designs with power eggs optimised for altitude (which rules out the F8F) would end up with very similar top speeds as the limiting factor would be airframe aerodynamics (mach limits).

In fact if you look at the maximums of those late war planes then, fully corrected for pitot issues, they are all doing 485 +-10 mph. </div></BLOCKQUOTE>

In the pitot and outside it the P-47D officially got to 398 mph while the F8F got to 375 mph.
If the F8F had a 2-stage supercharger it may well have competed with other types at altitude since its service ceiling was about 38 400 ft while the 47D effecive only got to 30 000 ft and that's with turbocharging.

Despite claims the F8F never saw combat it was sold to the French who used it in Indo China in the early 1950s

After overcoming heating issues the P-40 was one of the first inlines to demonstrate that radials did not deserve their almost complete dominance in aircraft design pre-war.
Even so, the need for radiator flaps jutting into the slipstream had its disadvantages and -apart from coolant damage as a factor in overheating - even a faulty fuel supply sent inlines into overheating on the ground.

The long noses of the inlines often meant a curved landing approach and a higher nose up attitude in turning than for radials.
Inlines seem to have dived better than radials across the board.

Freiwillige
11-03-2008, 11:36 PM
"Inlines seem to have dived better than radials across the board."

Ehem....ever heard of a P-47? http://forums.ubi.com/images/smilies/10.gif

KIMURA
11-04-2008, 12:38 AM
It seems that many compares pears and apples. Surely the WWII radials had more toal HP output, but viewing HP/litre ratio the inline is far superior to any radial, hands down.

Above the Rare Bear was hold up as a example that the radials is superior and the Rare Bear would be faster than the P-51 Dago Red. AFAIK the Dago Red still flies it's common prop and flies the civil variant of the V-1650 with the same displacement as the WWII Mustangs had. Rare Bear flies a R-3350 instead of the wartime R-2800 and is fitted out with a P-3 Orion prop to get enough prop sureface to overcome the drag of the cowling. Both engines has the same HP output of roughly 4000hp, the samller Merlin 622 with 27litres disp. and @150"hg, whereas the much bigger R-3350(43litres) is doing the same @140"hg.

WOLFMondo
11-04-2008, 04:41 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by DrHerb:
The fastest Propellor driven fighter (Bearcat) was powered by a Radial Engine.
</div></BLOCKQUOTE>

Rarebear is no fighter, its a highly modified racing plane which has little to do with a WW2 carrier based fighter aircraft.

A factory fresh bearcat was quite allot slower than a Dehavilland Hornet which used two handed Merlins.

There were quite a few inlines faster than the bearcat even at the bearcats best heights. Probably the fastest radial engined plane to see service were the fighter variants of the Hawker Seafury. The later versions of the Tempest with the Sabre VA were also extremely fast.

TinyTim
11-04-2008, 05:05 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by DrHerb:
The fastest Propellor driven fighter (Bearcat) was powered by a Radial Engine.
</div></BLOCKQUOTE>

The fastest propeller driven aircraft is Tu-95 (but it uses turboprops, not piston engines).

Bearcat is the fastest piston engine aircraft.

M_Gunz
11-04-2008, 05:09 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Freiwillige:
"Inlines seem to have dived better than radials across the board."

Ehem....ever heard of a P-47? http://forums.ubi.com/images/smilies/10.gif </div></BLOCKQUOTE>

P-47 has lower critical mach than say P-51 and certain FW's?
But until then the situation can vary widely as has been demonstrated.

The original poster has some ideas about P-47's and radials and altitude.

WAR DEPARTMENT, AIR CORP, MATERIAL DIVISION, Acceptance Performance Tests
Wright Field, Dayton, Ohio, June 18, 1942
P-47B Airplane, A.C. No. 41-5902 at 34,000 ft reached TAS 412 mph.
At 35k climb is less than 500 ft/min.

Mach TAS lowers with increased alt and the P-47 has a lower critical mach.
That plane ain't just puttering along near stall, best climb is 305mph at just under 500fpm.
That's a bit higher speed than stall only, still over 100mph envelope at 34k ft -- Mid 1942.

And combat capable at over 30k ft isn't exactly stick to the low ground, P-47's at high
alt were very capable esp in the long dives -- Gunther Rall got shot that way in a 109.

There's a later one Wright Field, Dayton, Ohio, 11 October 1943
P-47D-10 Airplane, AAF No. 43-75035 reached 404mph at 38k ft, no best climb TAS given for 500fpm.

What is the ceiling of P-47's? Maybe loaded with bombs, rockets, fuel....

M_Gunz
11-04-2008, 05:14 AM
If only, if only someone had decided to add extra fuel capacity to the P-47 design and....

swept the wings back to compensate for CoG change http://forums.ubi.com/images/smilies/winky.gif the P-47 would have have even
better dive performance through accidental higher critical mach. Any sweep helps....

stalkervision
11-04-2008, 05:36 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by M_Gunz:
If only, if only someone had decided to add extra fuel capacity to the P-47 design and....

swept the wings back to compensate for CoG change http://forums.ubi.com/images/smilies/winky.gif the P-47 would have have even
better dive performance through accidental higher critical mach. Any sweep helps.... </div></BLOCKQUOTE>

Then the tail would have fallen off.. http://forums.ubi.com/images/smilies/winky.gif

Aaron_GT
11-04-2008, 10:52 AM
A few figures to help things along, although I wish I'd noted down hp and weight too and exact engine model...

Anyway - format is

engine/hp per cubic inch/hp per lb dry weight

DB601*/0.56/0.89
R-4360**/0.99/1.11
R-2800/0.75/0.89
Sabre VA/1.36/1.29
Merlin 66/0.95/1.21***
Griffon 65/0.91/1.03
Centaurus/0.77/0.94
V-1710/0.77/0.92
Proteus/-/1.28
T56/-/2.75

* Without MW-50
** Late version with 4000hp. B-29 versions rather less hp so worse power:weight etc.
*** Last is WEP but hp/in^3 is without WEP.

Two turboprops shown for comparison.

As I noted before the real weight to look at is with all the superchargers, oil, fuel, cooling, ducts, etc. That is what WW2 designers considered which is why you see some planes with less powerful engines because the total package has a better power:weight ratio (e.g you have the Sea Fury with a Centaurus rather than the more powerful late Sabres, even though it has lower overall power and lower power:weight). This especially true for longer range when a small improvement in fuel efficiency makes a big difference. Plus there will be issues regarding altitude performance affecting best cruise altitudes and range, etc. Many, many factors!

Viper2005_
11-04-2008, 11:22 AM
When calculating weight drag, remember that the inline powerplant is engine + radiator.

The radial is just the radial

Well designed radials are very competitive with inlines in terms of total drag and also in terms of weight once you consider the whole powerplant.

Obviously maintenance is simplified by the fact that there's no water cooling system to break...

***

Inlines can win if you want a short dash at high power because you can use the coolant as a heat sink; the specific heat capacity of water is awesome.

That allows you to under-size the cooling system substantially and attain very impressive performance for a short period of time; great for racing, or for a fighter in a short dogfight - provided that you keep an eye on the temperature gauge!

If you want to cruise however you'll have a very hard time beating the radial.

Aaron_GT
11-04-2008, 12:27 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">When calculating weight drag, remember that the inline powerplant is engine + radiator. </div></BLOCKQUOTE>

I noted that, but the exact weight of the full installation of radiators etc varies, just as installations of the same radial vary (cf F8F and P-47!). Getting that sort of information is beyond my skills/patience.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">If you want to cruise however you'll have a very hard time beating the radial. </div></BLOCKQUOTE>

The P-51, Lancaster and Mosquito seemed to cruise well enough with their Merlins http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif

Viper2005_
11-04-2008, 02:42 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Aaron_GT:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">If you want to cruise however you'll have a very hard time beating the radial. </div></BLOCKQUOTE>

The P-51, Lancaster and Mosquito seemed to cruise well enough with their Merlins http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif </div></BLOCKQUOTE>

Not with the best SFC on record; nor the longest of TBOs...

Gumtree
11-04-2008, 03:58 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Aaron_GT:

DB601*/0.56/0.89
R-4360**/0.99/1.11
R-2800/0.75/0.89
Sabre VA/1.36/1.29
Merlin 66/0.95/1.21***
Griffon 65/0.91/1.03
Centaurus/0.77/0.94
V-1710/0.77/0.92
Proteus/-/1.28
T56/-/2.75

* Without MW-50
** Late version with 4000hp. B-29 versions rather less hp so worse power:weight etc.
*** Last is WEP but hp/in^3 is without WEP.

</div></BLOCKQUOTE>

From these figures you can see why the Merlin was such a winner. Tiny capacity for the performance it puts out. Surely this would also help with the airframe handling as it has less weight to throw around for the given hp.

Crikey2008
11-04-2008, 05:59 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by M_Gunz:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Freiwillige:
"Inlines seem to have dived better than radials across the board."

Ehem....ever heard of a P-47? http://forums.ubi.com/images/smilies/10.gif </div></BLOCKQUOTE>

P-47 has lower critical mach than say P-51 and certain FW's?
But until then the situation can vary widely as has been demonstrated.


...Mach TAS lowers with increased alt and the P-47 has a lower critical mach...
...

And combat capable at over 30k ft isn't exactly stick to the low ground, P-47's at high
alt were very capable esp in the long dives -- Gunther Rall got shot that way in a 109.


... </div></BLOCKQUOTE>

The elliptical wing of the early Spitfires got to mach 9.2 in a dive which is superior to some wing profiles.
If we accept that the P-47 has an elliptical wing (or effectively an elliptical wing) this may have enhanced its performance in a dive or may have impeded its performance.

Let's speculate:

Even at just below Mc there is an increase in the drag coefficient (wave drag from compression at or near supersonic velocity of the airflow over the wing).

If the region where the surface velocity is higher than that distant from the surface is not very extensive then wave drag is not great even though the actual velocity at the surface may be great.

However, compressibility problems in a dive are more of a problem where the thickness of the cord of the wing is more aft. A symmetrical wing profile fares better than a cambered wing profile. But thin profiles with max thickness to the rear produce intense supersonic regions over the whole surface and begin to develop compressibility problems on the under surface with increasing M leading to loss of lift in the dive.

Since you state that the P-47 has a lower Mc can it be adduced from that that the P-47 wing may suffer from increasing drag with increasing M in a dive? That would certainly be the case if its wing profile happened to produced a bow wave under airflow compression.

But these considerations do not explain the performance of the Spitfire elliptical wing in reaching 0.92 mach or thereabouts (I believe the wing was used on a British early design test jet).

Aaron_GT
11-04-2008, 07:05 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">If we accept that the P-47 has an elliptical wing (or effectively an elliptical wing) this may have enhanced its performance in a dive or may have impeded its performance. </div></BLOCKQUOTE>

It's the thinness of the Spitfire wing that is more critical than it's elliptical nature. The need for thin wings at high mach (absent sweep) was used in planes such as the X-1 and F-104.

Aaron_GT
11-04-2008, 07:07 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">I believe the wing was used on a British early design test jet). </div></BLOCKQUOTE>

No, that was the wing from the Spitfire-derived Spiteful on the Attacker. But the Spiteful wing was non-elliptical, laminar flow, and was totally different from the Spitfire wing. It is more closely associated with the P-51 design.

Crikey2008
11-04-2008, 08:43 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Aaron_GT:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">I believe the wing was used on a British early design test jet). </div></BLOCKQUOTE>

No, that was the wing from the Spitfire-derived Spiteful on the Attacker. But the Spiteful wing was non-elliptical, laminar flow, and was totally different from the Spitfire wing. It is more closely associated with the P-51 design. </div></BLOCKQUOTE>

Wings of late model spits all deviated from the elliptical principle to laminar flow. Therefore, if its correct that a laminar flow wing was the wing that achieved 0.92 mach then the source I quoted (a test pilot who called it elliptical) was mistaken.

Crikey2008
11-04-2008, 08:48 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Aaron_GT:
...It's the thinness of the Spitfire wing that is more critical than it's elliptical nature. The need for thin wings at high mach (absent sweep) was used in planes such as the X-1 and F-104.... </div></BLOCKQUOTE>

Not quite. The profile of the wing chord is the critical factor in compressibility effects. A thin wing will still be subject to having areas of its surface subject to subsonic and supersonic pressures. Where the pressure occurs determines the nature of the drag coefficients.

Kettenhunde
11-04-2008, 10:23 PM
This myth will not die! I bet somebody reads a report and takes it a face value with little understanding of the science behind it. That will get you into trouble with airplanes and lead to wrong conclusions..

Here is what the RAE said about the test that measured the Spitfire mach .92 performance!

http://img368.imageshack.us/img368/3981/spitfiremiracledivefk0.jpg (http://imageshack.us)
http://img368.imageshack.us/img368/spitfiremiracledivefk0.jpg/1/w777.png (http://g.imageshack.us/img368/spitfiremiracledivefk0.jpg/1/)

http://img368.imageshack.us/img368/5914/spitfiremiraclediveiiri2.jpg (http://imageshack.us)
http://img368.imageshack.us/img368/spitfiremiraclediveiiri2.jpg/1/w1163.png (http://g.imageshack.us/img368/spitfiremiraclediveiiri2.jpg/1/)

What does this mean? As the RAE concludes, the speed measurements are a failure. Well nobody was able to really accurately measure speed in the transonic realm until well into the post war years.

Sure your Spitfire could do mach .92 as it was measured. However an airplane traveling exactly the same speed right next to it might come out with a "measured" speed of mach .79!

How much do you know, Crikey, about normal shock formation and the velocities of the wave? I think knowing the properties of normal shock formation would greatly assist in your understanding of how the RAE made this error.

All the best,

Crumpp

Kurfurst__
11-06-2008, 06:34 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Aaron_GT:
As I noted before the real weight to look at is with all the superchargers, oil, fuel, cooling, ducts, etc. That is what WW2 designers considered which is why you see some planes with less powerful engines because the total package has a better power:weight ratio (e.g you have the Sea Fury with a Centaurus rather than the more powerful late Sabres, even though it has lower overall power and lower power:weight). This especially true for longer range when a small improvement in fuel efficiency makes a big difference. Plus there will be issues regarding altitude performance affecting best cruise altitudes and range, etc. Many, many factors! </div></BLOCKQUOTE>

Very true, especially when you consider how much auxilarry stuff an engine actually needs to become a complete POWERPLANT.. propellers, cooling radiators, piping, fuel, superchargers, intervcoolers - they all add up tremendous weight. Ie. a German report on the Merlin 61's complete weight - alone the cowling weights 53 kg, the whole powerplant and its subsystems some 1191 kg, to which there is a about 100 kg worth of coolant and lubricant weight as well.

http://i38.photobucket.com/albums/e133/Kurfurst/Merlin6x_complete_weight.jpg

For example in a radial vs inline comparison, comparing the bare engine blocks does not reveal the fact that there is also a rather bulky cooling system for the inline engine, that also adds some cooling drag, working against the lighter and smaller front area of the inline engine block in comparison to air cooled radials.