50 replies to this topic

[Impspeed Gerry]

Hi all,

I notice from photos of older sports racing cars with enclosed front body work and front water radiator, that their radiators are often installed with a pronounced forwards lean (top of rad towards front of car).

What is/are the reason(s) for this? Reducing overall height of the rad? Better airflow into the intake (although I doubt this one)? Better airflow out of the outlet (upwards and over the car with a top outlet, a la GT40)? Or any/all of these factors?

I ask as I am currently mounting the radiator in my '69 Davrian and I have space to put it upright, or canted forward up to around 15 degrees, whatever's best. The air will be vented out of the top of the bonnet.

Thanks

Gerry

Edited by Impspeed Gerry, 10 June 2009 - 13:20.

[Ray Bell]

I believe the idea was to get the air to hit the surface of the fins rather than just skim over them...

Optimum transference of heat was expected that way. Height was another factor, while in the case of Corvette radiators used in competition cars it was also a matter of getting a relatively tall rad down to a level at which it could be useful.

Another reason in some cars was the lack of available space for the inlet, the rad and the top surface outlet.

[Greg Locock]

I believe the idea was to get the air to hit the surface of the fins rather than just skim over them...

Optimum transference of heat was expected that way. Height was another factor, while in the case of Corvette radiators used in competition cars it was also a matter of getting a relatively tall rad down to a level at which it could be useful.

Another reason in some cars was the lack of available space for the inlet, the rad and the top surface outlet.

If you tilt the rad then there is some convective airflow through it even at a standstill.

[Paul Prost]

Here is a reply from myself (with some knowledge in the field) and from a friend who used to be an expert in the field of F1 cooling issues.

There is a difference between radiator efficiency and effectiveness.

A radiator works at its optimum efficiency when the air moves perpendicularly through the core. You don't have to 'turn' the flow at all, and you will get the most mass flow through the core. In the cooling engineers world, the rads would be very large frontal area and very small thickness

Unfortunately, obtaining the necessary heat transfer through this way will usually mean you'll have to build a thick, heavy core, mainly because of constraints based on surface area. In race car applications the available package is so small. As a result, the cross-sectional area is low and so thickness must be larger as the effectiveness of thicker cores drops off pretty fast (basically effectiveness is driven by DT and as the air flows through the rad DT gets smaller and the rate of heat transfer drops off rapidly - hence the desire for big XA and small thickness)

e.g. a sidepod only has a limited area, therefore if your radiator is perpendicular to the flow (i.e. vertical) your cross-sectional area is less, therefore you will need more tubes/fins to acheive the same amount of heat transfer.

It does all come down to surface area but it is how you use that surface area. Thinner cores (with equivalent fin densities) are better at rejecting the heat because DT is high.

You can achieve the same heat rejection via a longer, thinner core that is canted. Although the radiator isn't working as efficiently, you can design the larger, canted radiator to achieve the same effectiveness..which is basically the outlet temperature of the core fluid.

It should weigh marginally less (all good for lap time) and should give you a drag benefit (force normals in the right direction)

This all depends how you define effective and efficient. I'd say for a given engine heat rejection and thinner larger cross section will always be desirable and more effective at rejecting heat. However the efficiency of the thinner large cross section rad may be hampered by poor flow distribution if your aero team stuff up the sidepod ducting. The smaller cross section thick core will be less effective (in a heat rejection to weight sense) because you'll need more surface area to reject the same amount of heat but will benefit in efficiency through good flow distribution. To that end it is up to the rad, aero and dynamics bods to work out where the trade-offs need to happen wrt engine heat rejection, drag and CoG polars. Taking it to the nth degree you'd almost like to tailor the airflow to ensure the coldest cooling air impinges on the hottest coolant sections of the rad and that the coolant flow was managed to maximise heat flow. That however is the realm of academia rather than practical implementation.

Some motorbikes use curved radiators and many use dimpled tubes to promote mixing in the coolant side (although the limiting factor is always the airside)

[Impspeed Gerry]

Thanks guys, very informative.

So do I take it that instead of using the exisiting (40 year old, very heavy) short (8" tall), thick (3.5") rad which is designed to sit up-right, it'd be better all round if I could fit a taller, slimmer, lighter ally one, canted forward?

I looked more closely last night and I reckon I could go to around 30-35 degrees forward tilt with a slimmer rad (say 2"), so basic trig suggests a 9.5" high rad would fit in the same space without bodywork clearance issues. I'll probably make a cardboard mock-up to check this more accurately.

Is there an optimum angle of tilt, or a maximum beyond which the benefits are cancelled out - I would imagine that 35 degrees is well within accepted norms?

Thanks again,

Gerry

[Ross Stonefeld]

I just figured it was as simple as the same reason they angle parking slots on streets

[cheapracer]

As well as Ross above /\, did any of you consider theres brake master cylinders in the way also?

[Tony Matthews]

As well as Ross above /\, did any of you consider theres brake master cylinders in the way also?

If there aren't now, there will be when he hits the wall head-on!

[mariner]

The other thing to consider is the relationship of the radiator face to the bodywork inlet. In a perfect world you want to turn air velocity at the entry into static pressure at the rad. face. There are various rules of thumb around on this. One old one is the entry to face distance must be at least as big as the rad. height. Also then you can reduce the entry size and improve drag which is harder with a short entry to rad. face measurement.

You can go longer but then there is a trade off of building pressure out of velocity versus skin drag inside the rad. duct.

Lastly, literally, is the exit shape and length. Again the theory is that if it is long enough you will re accelerate the air back to oustide velocity and minimise drag. I seem to recall that it has been said by experts that more rad designs are spoilt by poor exiting than poor entry. that is another reason for sloping it forward . It allows an easy exit up into the (usually) low pressure area just behind the nose.

The importance of all of this was proven in WW2 by P-51 Mustang which got its very high performance from a thin laminar flow wing. that in turn was made possible by the clever radiator installation which was in the empty and thus wasted fuselage space behind the cockpit . Air was taken in via a very small duct away from the boundary layer under the cockpit, expanded out in the rear fuselage so as to give good static pressure for a very large/thin rad. then reaccelerated out vis a small exit ( but bigger than the entry). Result enough less drag that the Mustang could fly all the way with the US bombers ( with drop tanks ) and thus make daytime bombing is viable strategy rather than a virtual suicide mission).

[Greg Locock]

The importance of all of this was proven in WW2 by P-51 Mustang which got its very high performance from a thin laminar flow wing. that in turn was made possible by the clever radiator installation which was in the empty and thus wasted fuselage space behind the cockpit . Air was taken in via a very small duct away from the boundary layer under the cockpit, expanded out in the rear fuselage so as to give good static pressure for a very large/thin rad. then reaccelerated out vis a small exit ( but bigger than the entry). Result enough less drag that the Mustang could fly all the way with the US bombers ( with drop tanks ) and thus make daytime bombing is viable strategy rather than a virtual suicide mission).

Real aerodynamicists beg to differ. The surface finish of the wings in production was nowhere near good enough to achieve laminar flow, and the thrust from the radiator was fairly small. Glider pilots hand finish their composite wings in an attempt to get laminr flow, and find that insects or raindrops are enough to wreck it, even at their comparitively slow flying speeds. A wing panel made of aluminium sheet rivetted to aluminium ribs is going to be much worse than that. Then add the effect of propwash. No chance.

But yes, it is a nice story

http://74.125.153.13...G...=en&ct=clnk

For a very reasonable sounding post on the issues

[mariner]

I think I used the phrase " laminar flow" in too loose a sense for the real experts.

The wing cross section used on the P 51 was ofen called " laminar flow" by the people who designed it. The real point was , I think, was that the P 51 wing was much thinner than the conventional wings like the Spitfire etc. and therefore had much less drag. It could only be that thin by moving the radiators completely out of the wing intot the fuselage. The Spitfire had a wing mounted rad ( retractable I think ) which prevented a very thin wing.

I don't think anybody ever claimed any thrust from the rad exit, the benefits were overall system ones - rad in rear fuslage allows thin wing = less drag = more range/speed.

[phantom II]

The wing of the Mustang was just as thick as the Spitfire wing. The thickest part was just further back. Drop tank systems were fitted on some Spitfires which gave them the same range as the P51 and with more powerful RR engines and improved build quality, there was little difference in speed. At high g loads and slow flight, the Mustangs wing flow had adverse effect on aileron efficiency and if these two latest renditions of these planes opposed one another, the higher kill ratio would've favored the Spitfire.
The Mustang wasn't the first plane to have this wing section. (Which worked as it was originally designed on some Reno racer P51s) The Germans invented it and many airplanes used this technology prior to the Mustang including some American bombers.
The energy put into the Mustang radiator (heat) and the shape and size of the outlet caused the outlet nozzle velocity to be higher than the intake. The drag of the cooling system was 30% less than that of the Spitfire. Propwash over the wing root was not a bad thing because it reduced take off roll with higher payloads and delayed stall at higher induced wing loads. Rudder and elevator effectiveness is greater the more the propwash. All this is better in dogfights unless your opponent was a FW 190, with a high laminar flow wing that really worked.

I think I used the phrase " laminar flow" in too loose a sense for the real experts.

The wing cross section used on the P 51 was ofen called " laminar flow" by the people who designed it. The real point was , I think, was that the P 51 wing was much thinner than the conventional wings like the Spitfire etc. and therefore had much less drag. It could only be that thin by moving the radiators completely out of the wing intot the fuselage. The Spitfire had a wing mounted rad ( retractable I think ) which prevented a very thin wing.

I don't think anybody ever claimed any thrust from the rad exit, the benefits were overall system ones - rad in rear fuslage allows thin wing = less drag = more range/speed.

[mariner]

Thank you for all that WW11 plane info. as I am ( clearly) not an expert.

When I went to see the warplanes airshow at Duxford the Mustangs seemed to make a better noise than Spitfires but the Spitfire looks more graceful! I must say the wing section shape must be important as , by the naked eye the Mustang wing does look thinner. I suppose that is because you see the thinner bit at the front.

What sort of amused me comparing all the fighters was how both the Mustang and the Spitfire looked very elegant peices of design but the P 47 Thunderbolt just looked HUGE and totally ungainly. It just seemed as if they had bolted a plane onto the biggest radial engine they could find! However if I understand it right that also could flly all the way with bombers and was fast so maybe there are different solutions in planes to the same probelm.

[phantom II]

The difference in the sound came from the huge 4 blade Standard Hamilton propeller. The Jug was a newer design and could take those other two aircraft in short order together.

Thank you for all that WW11 plane info. as I am ( clearly) not an expert.

When I went to see the warplanes airshow at Duxford the Mustangs seemed to make a better noise than Spitfires but the Spitfire looks more graceful! I must say the wing section shape must be important as , by the naked eye the Mustang wing does look thinner. I suppose that is because you see the thinner bit at the front.

What sort of amused me comparing all the fighters was how both the Mustang and the Spitfire looked very elegant peices of design but the P 47 Thunderbolt just looked HUGE and totally ungainly. It just seemed as if they had bolted a plane onto the biggest radial engine they could find! However if I understand it right that also could flly all the way with bombers and was fast so maybe there are different solutions in planes to the same probelm.

[gruntguru]

Thank you for all that WW11 plane info. as I am ( clearly) not an expert.

When I went to see the warplanes airshow at Duxford the Mustangs seemed to make a better noise than Spitfires but the Spitfire looks more graceful! I must say the wing section shape must be important as , by the naked eye the Mustang wing does look thinner. I suppose that is because you see the thinner bit at the front.

What sort of amused me comparing all the fighters was how both the Mustang and the Spitfire looked very elegant peices of design but the P 47 Thunderbolt just looked HUGE and totally ungainly. It just seemed as if they had bolted a plane onto the biggest radial engine they could find! However if I understand it right that also could flly all the way with bombers and was fast so maybe there are different solutions in planes to the same probelm.

The blunt front presented by an air-cooled radial is certainly nowhere near as aesthetically pleasing as a Sptfire ar Mustang but the appearance of much higher drag is largely an illusion. Most of the air striking the front of course flows (fairly smoothly) through the engine bay, and the heat added in cooling the engine is used fairly effectively by the NACA duct to generate thrust which ecceeds the engine cooling drag.

[phantom II]

Out take, but i think most will enjoy.

Comments from the pilot that flew the 747 with Atlantis back from California.


Walt and all,


Well, it's been 48 hours since I landed the 747 with the shuttle Atlantis on top and I am still buzzing from the experience. I have to say that my whole mind, body and soul went into the professional mode just before engine start in Mississippi, and stayed there, where it all needed to be, until well after the flight...in fact, I am not sure if it is all back to normal as I type this email. The experience was surreal. Seeing that "thing" on top of an already overly huge aircraft boggles my mind. The whole mission from takeoff to engine shutdown was unlike anything I had ever done. It was like a dream...someone else's dream.


We took off from Columbus AFB on their 12,000 foot runway, of which I used 11,999 1/2 feet to get the wheels off the ground. We were at 3,500 feet left to go of the runway, throttles full power, nose wheels still hugging the ground, copilot calling out decision speeds, the weight of Atlantis now screaming through my fingers clinched tightly on the controls, tires heating up to their near maximum temperature from the speed and the weight, and not yet at rotation speed, the speed at which I would be pulling on the controls to get the nose to rise. I just could not wait, and I mean I COULD NOT WAIT, and started pulling early. If I had waited until rotation speed, we would not have rotated enough to get airborne by the end of the runway. So I pulled on the controls early and started our rotation to the takeoff attitude. The wheels finally lifted off as we passed over the stripe marking the end of the runway and my next hurdle (physically) was a line of trees 1,000 feet off the departure end of Runway 16. All I knew was we were flying and so I directed the gear to be retracted and the flaps to be moved from Flaps 20 to Flaps 10 as I pulled even harder on the controls. I must say, those trees were beginning to look a lot like those brushes in the drive through car washes so I pulled even harder yet! I think I saw a bird just fold its wings and fall out of a tree as if to say "Oh just take me". Okay, we cleared the trees, duh, but it was way too close for my laundry. As we started to actually climb, at only 100 feet per minute, I smelled something that reminded me of touring the Heineken Brewery in Europe...I said "is that a skunk I smell?" and the veterans of shuttle carrying looked at me and smiled and said "Tires"! I said "TIRES??? OURS???" They smiled and shook their heads as if to call their Captain an amateur...okay, at that point I was. The tires were so hot you could smell them in the cockpit. My mind could not get over, from this point on, that this was something I had never experienced. Where's your mom when you REALLY need her?


The flight down to Florida was an eternity. We cruised at 250 knots indicated, giving us about 315 knots of ground speed at 15,000'. The miles didn't click by like I am use to them clicking by in a fighter jet at MACH .94. We were burning fuel at a rate of 40,000 pounds per hour or 130 pounds per mile, or one gallon every length of the fuselage. The vibration in the cockpit was mild, compared to down below and to the rear of the fuselage where it reminded me of that football game I had as a child where you turned it on and the players vibrated around the board. I felt like if I had plastic clips on my boots I could have vibrated to any spot in the fuselage I wanted to go without moving my legs...and the noise was deafening. The 747 flies with its nose 5 degrees up in the air to stay level, and when you bank, it feels like the shuttle is trying to say "hey, let's roll completely over on our back"..not a good thing I kept telling myself. SO I limited my bank angle to 15 degrees and even though a 180 degree course change took a full zip code to complete, it was the safe way to turn this monster.


Airliners and even a flight of two F-16s deviated from their flight plans to catch a glimpse of us along the way. We dodged what was in reality very few clouds and storms, despite what everyone thought, and arrived in Florida with 51,000 pounds of fuel too much to land with. We can't land heavier than 600,000 pounds total weight and so we had to do something with that fuel. I had an idea...let's fly low and slow and show this beast off to all the taxpayers in Florida lucky enough to be outside on that Tuesday afternoon. So at Ormond Beach we let down to 1,000 feet above the ground/water and flew just east of the beach out over the water. Then, once we reached the NASA airspace of the Kennedy Space Center, we cut over to the Banana/Indian Rivers and flew down the middle of them to show the people of Titusville, Port St.Johns and Melbourne just what a 747 with a shuttle on it looked like. We stayed at 1,000 feet and since we were dragging our flaps at "Flaps 5", our speed was down to around 190 to 210 knots. We could see traffic stopping in the middle of roads to take a look. We heard later that a Little League Baseball game stop to look and everyone cheered as we became their 7th inning stretch. Oh say can you see...


After reaching Vero Beach, we turned north to follow the coast line back up to the Shuttle Landing Facility (SLF). There was not one person laying on the beach...they were all standing and waving! "What a sight" I thought...and figured they were thinking the same thing. All this time I was bugging the engineers, all three of them, to re-compute our fuel and tell me when it was time to land. They kept saying "Not yet Triple, keep showing this thing off" which was not a bad thing to be doing. However, all this time the thought that the landing, the muscling of this 600,000 pound beast, was getting closer and closer to my reality. I was pumped up! We got back to the SLF and were still 10,000 pounds too heavy to land so I said I was going to do a low approach over the SLF going the opposite direction of landing traffic that day. So at 300 feet, we flew down the runway, rocking our wings like a whale rolling on its side to say "hello" to the people looking on! One turn out of traffic and back to the runway to land...still 3,000 pounds over gross weight limit. But the engineers agreed that if the landing were smooth, there would be no problem. "Oh thanks guys, a little extra pressure is just what I needed!" So we landed at 603,000 pounds and very smoothly if I have to say so myself. The landing was so totally controlled and on speed, that it was fun. There were a few surprises that I dealt with, like the 747 falls like a rock with the orbiter on it if you pull the throttles off at the "normal" point in a landing and secondly, if you thought you could hold the nose off the ground after the mains touch down, think again...IT IS COMING DOWN!!! So I "flew it down" to the ground and saved what I have seen in videos of a nose slap after landing. Bob's video supports this! :8-)


Then I turned on my phone after coming to a full stop only to find 50 bazillion emails and phone messages from all of you who were so super to be watching and cheering us on! What a treat, I can't thank y'all enough. For those who watched, you wondered why we sat there so long. Well, the shuttle had very hazardous chemicals on board and we had to be "sniffed" to determine if any had leaked or were leaking. They checked for Monomethylhydrazine (N2H4 for Charlie Hudson) and nitrogen tetroxide (N2O4). Even though we were "clean", it took way too long for them to tow us in to the mate-demate area. Sorry for those who stuck it out and even waited until we exited the jet.


I am sure I will wake up in the middle of the night here soon, screaming and standing straight up dripping wet with sweat from the realization of what had happened. It was a thrill of a lifetime. Again I want to thank everyone for your interest and support. It felt good to bring Atlantis home in one piece after she had worked so hard getting to the Hubble Space Telescope and back.



Triple Nickel

NASA Pilot

[dosco]

The difference in the sound came from the huge 4 blade Standard Hamilton propeller. The Jug was a newer design and could take those other two aircraft in short order together.

The P-47 could take the P-51? Interesting. I have always understood that the P-47 suffered from maneuverability issues because of its weight. Less so with the P-51 (and Fw-190) by comparison.

[dosco]

What sort of amused me comparing all the fighters was how both the Mustang and the Spitfire looked very elegant peices of design but the P 47 Thunderbolt just looked HUGE and totally ungainly. It just seemed as if they had bolted a plane onto the biggest radial engine they could find! However if I understand it right that also could flly all the way with bombers and was fast so maybe there are different solutions in planes to the same probelm.

Gotta fit that turbocharger and intercooler somewhere.

[phantom II]

It is not really a case for maneuverability, it is that of tactical advantage that the Jug provides. First, the 190 and 109 can shoot at you all day long with their 20mm cannons without damaging the Jug very much, especially from behind, that is if they can catch you going faster and higher than you can with full tanks(drop tanks jettisoned) and full armaments. Then you can dive faster than they can and hit them with all 8 of your very accurate .50 cal guns quite a few times while they run out of fuel and ammo and tricks.
There was a story one time when a 109 kept on shooting at a Jug till the German ran out of ammo. He shot at him for a while at his 6 and then flew up beside the Jug and thought," Vot de Fuk", and got on his six again and let fly with a few more rounds with the same result. He eventually flew beside the P47 and saluted the pilot because he was out of ammo. All the while, the Jug flew straight and level back toward England with his guns empty and the fuel gauges looking at the pilot out of the corner of their eyes.
Discovery or the History Chanel did a 4 part story called "Fighter Pilot." It was the story of a P47 pilot. Excellent, if you can find it.

The P-47 could take the P-51? Interesting. I have always understood that the P-47 suffered from maneuverability issues because of its weight. Less so with the P-51 (and Fw-190) by comparison.

[dosco]

It is not really a case for maneuverability, it is that of tactical advantage that the Jug provides. First, the 190 and 109 can shoot at you all day long with their 20mm cannons without damaging the Jug very much, especially from behind, that is if they can catch you going faster and higher than you can with full tanks(drop tanks jettisoned) and full armaments. Then you can dive faster than they can and hit them with all 8 of your very accurate .50 cal guns quite a few times while they run out of fuel and ammo and tricks.

This was an advantage, to be sure. Grumman birds were renowned for their toughness as well.

There was a story one time when a 109 kept on shooting at a Jug till the German ran out of ammo. He shot at him for a while at his 6 and then flew up beside the Jug and thought," Vot de Fuk", and got on his six again and let fly with a few more rounds with the same result. He eventually flew beside the P47 and saluted the pilot because he was out of ammo. All the while, the Jug flew straight and level back toward England with his guns empty and the fuel gauges looking at the pilot out of the corner of their eyes.
Discovery or the History Chanel did a 4 part story called "Fighter Pilot." It was the story of a P47 pilot. Excellent, if you can find it.

Saw it on "Dogfights" on the history channel. Was an interesting story.

FWIW, I used to volunteer at the Champlin Fighter Museum. Ended up meeting a few WWII aces.

[venator]

20mm>cal.50 (12.7mm)

[Greg Locock]

20mm>cal.50 (12.7mm)

Yes but Weight of fire 0.5">20mm

and MV 0.5">20mm

both are important

[NRoshier]

I'm aware of the story of the P47 that was shot up by light machine gun fire, it is on youtube.
P11 is however somewhat over generous in his estimation of the P47 strength. Getting a load of holes punched in a plane from a 7.9mm machine guns is one thing, getting hit by explosive rounds from a 20 or 30mm cannon is another thing. There is plenty of gun camera footage that shows the effects of these guns and there is little doubt they were far more destructive than a .50.

[GreenMachine]

Gotta fit that turbocharger and intercooler somewhere.

Yes, have a look at where the turbocharger sits, and what is needed to connect it to the engine so it can do its work...

Yanks had a predeliction for remote turbos, see also P38 and one of their big bombers too.

Edited by GreenMachine, 06 July 2009 - 09:37.

[GreenMachine]

Yes but Weight of fire 0.5">20mm

and MV 0.5">20mm

both are important

But probably not as important for knocking down an aeroplane, especially a large aeroplane, and more so one whose vital parts are armoured. For that you need a large round which is individually capable of doing a lot of damage to the structure or mechanicals.

Check out the German MK103 30mm cannon which had both a large round, and a high muzzle velocity. The Germans also used 4 x 30mm MK108 on the Me262, it had a fairly heavy round, but a slow muzzle velocity. They knew what was necessary to knock down a B17.

[NRoshier]

I think that it is telling that post WW2 every country apart from the USA went to cannons for their fighter aircraft and in Korea there was much complaint about the F86 vs the Mig15 in gun effectiveness

[gruntguru]

Yes, have a look at where the turbocharger sits, and what is needed to connect it to the engine so it can do its work...

Yanks had a predeliction for remote turbos, see also P38 and one of their big bombers too.

Very bad for efficiency - lots of exhaust energy lost as heat before it gets to the turbine. Good for cockpit comfort at high altitudes.

[Bill S]

Very bad for efficiency - lots of exhaust energy lost as heat before it gets to the turbine. Good for cockpit comfort at high altitudes.

True, but it was no doubt done for packaging/aerodynamic reasons.

Edited by Pascal, 06 January 2011 - 09:08.

[gruntguru]

True, but it was no doubt done for packaging/aerodynamic reasons.

Yes. turbos were a lot bigger (and therefore difficult to package) in those days.

[phantom II]

This will explain the 10:1 kill ratio in favour of the Saber.

I think that it is telling that post WW2 every country apart from the USA went to cannons for their fighter aircraft and in Korea there was much complaint about the F86 vs the Mig15 in gun effectiveness

[gruntguru]

This will explain the 10:1 kill ratio in favour of the Saber.

Poor commies didn't stand a chance.
Erm - I think even Americans spell that "Sabre" don't they?

Edited by gruntguru, 07 July 2009 - 23:29.

[Dragonfly]

Would someone decode the diagram for us non fighter pilots? Not everything is readable. Why the resultant lines split? I suppose it's a standard performance comparison diagram, self explanatory for the professionals.
Thanks.

[gruntguru]

Would someone decode the diagram for us non fighter pilots? Not everything is readable. Why the resultant lines split? I suppose it's a standard performance comparison diagram, self explanatory for the professionals.
Thanks.

Some kind of "turning" performance envelope. Two vertical boundaries look like stall limit on the left and max speed on the right. Topped off with a hyperbola - probably constant G at a fixed limit imposed by structural strength. Interesting the Mig is a little better there - I would have thought that was important. Don't know what the lower "hump" is. PII??

Edited by gruntguru, 08 July 2009 - 01:20.

[GreenMachine]

This will explain the 10:1 kill ratio in favour of the Saber.

All aircaft (and cars, and women, and ...) have their good points, and not so good points. And that graph illustrates this point very neatly - if I am reading it correctly, it shows some places where the MiG had an advantage, others where the F86 had the advantage.

Actually, the reason for the high 'kill' ratio in favour of the Sabre was less any performance advantage, rather better trained pilots, who knew how to get the best out of the aircraft. That is, use your advantages to combat your enemy's advantages - fight to your strengths, and don't allow the fight to suck you into a regime where you lose that advantage..

This outcome is all the more creditable when the tactical advantages of the MiG flyers are considered- especially their refuge north of the Yalu where they were untouchable.

[Catalina Park]

Australian made Sabres had cannons. The resulting surge when the cannons were fired cause big problems to the Avon engines.

[Dragonfly]

Some kind of "turning" performance envelope. Two vertical boundaries look like stall limit on the left and max speed on the right. Topped off with a hyperbola - probably constant G at a fixed limit imposed by structural strength. Interesting the Mig is a little better there - I would have thought that was important. Don't know what the lower "hump" is. PII??

Yes, that's why I asked (indirectly pII) to explain with words the performance differences and the advantages of the Sabre.

[phantom II]

GG has it right. This is a graph showing turn rate in deg/sec vs mach # Constant density that is not shown (altitude say 25 000) This is the optimum altitude and the numbers change with air density. The turn radius lines are labeled on the graph from 1000 to 4000. The next 3 lines are shown in the margin, 8000, 15,000 and 30,000. It shows that at a given mach number and turn rate, there is a corresponding turn radius. The turn load factor in Gs is plotted against specific turn rates and turn radii.
The higher the Mach no. the bigger the turn radius and the lower the rate of turn.
At first it appears that MiG numbers are superior.
The Sabre shows an advantage in Energy retention in turns and a wider and flatter envelope. Energy management was the fighter pilots main goal. The MiGs energy is quickly spent and leaves Ivan a sitting duck after an evasive maneuver.
The Sabre had hydraulically activated control surfaces, while poor old Ivan did not. The Sabre also had better visibility. The Koreans actually had better tactical training at the beginning of the war. We still used WW II tactics which for jets was obsolete.
We could churn out pilots quicker and when their good pilots got killed, we over whelmed them with Numbers. That is actually how we win wars. We over whelm our opponents with tons of equipment. If you are so inclined and have time to go thru the link below, you may get insight as to how the performance difference of the Sabre can be exploited in the second half of the study.



You may be able to get in here as a civie. Boyds Aerial Attack Study.
http://www.scribd.co...S-Air-Force-orr
This is part of the manual for combat training at the Aggressor Squadron bases and the Navy's Top Gun FPS. A thing of the past now, but the pilots were armed with this information toward the end of Vietnam. McNamara ignored Boyd's pleas for this type of training because dog fights were thought to be a thing of the past. I had a blast for nearly 4 years flying like this. Of course, we didn't have live ammo.
You can see here how two pilots can achieve completely different results in the same plane(F105) using Boyd's T2 line also shown in above graph.

[dosco]

GG has it right. This is a graph showing turn rate in deg/sec vs mach # Constant density that is not shown (altitude say 25 000) This is the optimum altitude and the numbers change with air density.

You may be able to get in here as a civie. Boyds Aerial Attack Study.

Glad that you mentioned John Boyd. I figured the graph was somehow related to Boyd, the Coram book about Boyd talks of "simple graphs in red and blue that Generals could understand." The red and blue on your graph reminded me of that.

Readers interested in Boyd's work will probably find the Aerial Attack Study and other Boyd briefings here: www.d-n-i.net Some of the gents that worked with Boyd post there ... Bill Lind being one of them. Perhaps you know Mr. Lind?

[Dragonfly]

energy is quickly spent and leaves Ivan a sitting duck after an evasive maneuver

Thanks PII

[phantom II]

Boyd's Aerial Attack Study only came after the Korean war. The graph was made on an IBM main frame computer in 61. He of course flew F86s in that war and didn't follow the old WWII tactics that worked for P38s.
To me, it was so obvious what to do when the plane stopped mid air when you tried to turn. Take a modern fighter for instance. F/A 18 Super Hornet. It can retain energy at a 7 G turn with its super critical wing. The newest F18 will be able to super cruise. F22 allegedly has better performance but it is classified as is the Eurofighter.
Boyd designed the F15 and 16. The F16 is his baby.
A F4 on the other hand will loose energy at the rate of 50kts/sec in a 2 G turn. WWII planes were pretty hopeless also. I nearly bought a P51 about 10 years ago, but I was appalled at it's performance compared to my Extra.
I think it was instinctual to keep on unloading the wing to keep the damned thing flying. All maneuvers are done with this in mind. Boyd worked out a T2 specific for the this plane which Itaught. I was pretty conversant with all that stuff at one time but now I know nothing.

Thanks PII

Edited by phantom II, 08 July 2009 - 22:00.

[gruntguru]

Boyd's Aerial Attack Study only came after the Korean war. The graph was made on an IBM main frame computer in 61. He of course flew F86s in that war and didn't follow the old WWII tactics that worked for P38s.
To me, it was so obvious what to do when the plane stopped mid air when you tried to turn. Take a modern fighter for instance. F/A 18 Super Hornet. It can retain energy at a 7 G turn with its super critical wing. The newest F18 will be able to super cruise. F22 allegedly has better performance but it is classified as is the Eurofighter.
Boyd designed the F15 and 16. The F16 is his baby.
A F4 on the other hand will loose energy at the rate of 50kts/sec in a 2 G turn. WWII planes were pretty hopeless also. I nearly bought a P51 about 10 years ago, but I was appalled at it's performance compared to my Extra.
I think it was instinctual to keep on unloading the wing to keep the damned thing flying. All maneuvers are done with this in mind. Boyd worked out a T2 specific for the this plane which Itaught. I was pretty conversant with all that stuff at one time but now I know nothing.

PII is that what the lower (concave down) envelope is - max turn rate with conservation of airspeed? If so the Mig has an advantage in that department below Mach 0.7.

[Dragonfly]

Thanks again PII.
In fact I was trying to make a word joke with my name which is Ivan, but you may have forgotten.
This however led to more explanations from your side for which I am very grateful as a man with interest in aviation but who never had the chance to fly a plane.

[phantom II]

The aircraft were closely matched but you bring the fight to where you have an advantage. In this case above Mach 0.7. So the faster the Sabre goes, the more he can turn in on the MiG. The MiG pilot can't bring the Sabre to its advantage. The fastest plane has the advantage. The contest between a F4 and MiG 21 require the F4 to go low and fast.
I don't know how the numbers would change with altitude, but the Sabre is easier to fly and a lower altitude would make the MiG even harder to fly. You can see that they are only pulling 2g. The first engagements usually are with the best pilots on each side. You survival will depend on how quickly you learn your opponents aircraft's capabilities.
I never had this opportunity. I only had play dogfights.

PII is that what the lower (concave down) envelope is - max turn rate with conservation of airspeed? If so the Mig has an advantage in that department below Mach 0.7.

Edited by phantom II, 08 July 2009 - 23:33.

[phantom II]

Hang around your local glider port and help out where you can. You'll get rides in two seat planes all the time. Even the worst glider is much more fun than any powered single engine plane that you will see at your local airport. Learn to fly a glider and every other plane that you will fly will be an anti-climax.

Thanks again PII.
In fact I was trying to make a word joke with my name which is Ivan, but you may have forgotten.
This however led to more explanations from your side for which I am very grateful as a man with interest in aviation but who never had the chance to fly a plane.

[dosco]

Learn to fly a glider and every other plane that you will fly will be an anti-climax.

Just ask Chesley Sullenberger III.

[desmo]

When I was a kid, my best friend's dad was an USAF colonel- later general- and what struck me in retrospect was how bookish and quiet he was. More like a history prof than a classic military type, but he took us flying and let us see the local AFB up close and personal. Great guy and dad.

[dosco]

When I was a kid, my best friend's dad was an USAF colonel- later general- and what struck me in retrospect was how bookish and quiet he was. More like a history prof than a classic military type, but he took us flying and let us see the local AFB up close and personal. Great guy and dad.

What did he fly?

[slucas]

"If God had meant man to fly ,he would never have given us trains" Swan

Getting back to inclined rads, getting the air out can be a challange in saloon cars what with the windscreen there an all. Is the area in front of the screen a high preasure or low preasure area, or is that a dumb question? There must be more to it than cutting a hole in the hood. What "backyard" solutions are there?

(back to planes if you like)

[desmo]

What did he fly?

He had a Piper Cub, a Cessna and a Beechcraft. I wish I knew more specifically, but I didn't care. He'd let me have the stick/wheel and it was the biggest thrill of my young life. The Cub seemed the coolest to me.

[ray b]

"If God had meant man to fly ,he would never have given us trains" Swan

Getting back to inclined rads, getting the air out can be a challange in saloon cars what with the windscreen there an all. Is the area in front of the screen a high preasure or low preasure area, or is that a dumb question? There must be more to it than cutting a hole in the hood. What "backyard" solutions are there?

(back to planes if you like)

air in front of the windscreen is high pressure
some of the better high speed ramair tricks tapped that
chevy used that trick on the ''W" cars and the z-28's

for getting air out of a front mounted rad look at the ford GT or mac can-am cars
they used a wing shape curve to the bottom ''ramp'' to both extract the air and get some downforce too

one stray thought to tilted rads
has anyone tilted the fins to line up with the total units tilt