The Heat Is On!

[Dadtallica]

I never know how deep the realism is in regard to the real life vs. the simulation. I have many questions but today’s is about engine temperature.

• How closely models is it?
• Does “warming up engines” make a big difference?
• Is the same for fighters and bombers?

If you have any other nuggets of wisdom to add for this topic then please do!

[OLtos]

I have been in the online flying community since the 1990s.  I was an AirWarrior Junkie back then because I could never figure out how to play Warbirds on a Telnet connection.

That said, the word was that all the flight models had come from the "pilot notes" from the WWII program, during and after, wherein all the enemy planes were tested.  The program existed but tracking that information down was impossible.  It was in The Sarah Clark Collection and I found that at the National Archives, but it was a real mess, and no such notes were indexed at all.

I then went to the restoration facility for Smithsonian Air and Space asking about where it might be.  He said it really didn't matter!

You see field conditions were such that any given AIRPLANE let alone airplane type, could vary in perfomance, UP or DOWN by as much as 10 % simply because the ground crew or pilot did something a little different that day.  An example, you can markedly increase the top speed of an airplane simply by waxing the lower surface of the wing.

In any event. Aces High here is from War Birds, I believe it is the same flight performance data.   The thing to remember is that the closest you will get to any kind of accurate field performance is plus or minus 10% - 20%.  So the reality is that it isn't real because these are all "book" values, and NO WWII airplane flew to book values.

In the end though Aces High has the best most accurate book values in the flight sim genre.

Engine Heating:  This is very "standardized".    You only overheat if you are on WEP.  There is no need to warm up engines.  That is presumed as you are in a "ready 1 min" standby mode.

Oddities.  WEP some planes like the P47 and P-38 didn't really HAVE WEP.  They were "turbo" charged no "super" charged.  A turbocharger running off of the engine exhaust could be adjusted on the ground to a very wide degree.   The pilot could then "over boost" the engine.   But it wasn't WEP and heat only played a roll at certain altitudes in certain models of the same plane.

So a little "hedging" occurs in game because of that.  But, it isn't critical and only WWII plane junkies like me would even know this.

So get back IN.  Aces hasn't changed the flight models since it's begginings as far as I know.

[TryHard]

Alright every fighter plane that fought in WW2 was the very least single stage supercharged (if your manifold pressure is higher than 30 inHg at wide open throttle the engine has some form of forced induction). The P38 and P47 had a first stage supercharger behind the "carburetor" and a second stage turbo charger with an intercooler feeding the "carburetor".

However the P47 and later P38 models did have WEP in the form of water methanol injection which lowers cylinder head temperatures and allows you to run higher manifold pressure (boost) before detonation and or preignition occur which will damage the engine very rapidly. An with water meth injection the R2800-C in the P47M/N thunderbolts will produce 2800HP at sea level. The intresting thing is the F4U-4 corsair uses the same engine but with out a turbo charger and instead has 2 speed 2nd stage supercharge in addition to the first stage(technically 3 speed if you count neutral as a gear) and would also make 2800HP but wouldn't hold that power as consistently with altitude as the turbocharged P47. Some mechanics in the field would turn up the turbocharger regulators in the P47Ms to produce up to 90 inHg of manifold pressure which is somewhere north of 3000Hp but that's a field modification and not verified, also even 150 octane fuel being sprayed with water/meth will eventually detonate with enough boost and you really only wanted to push that much power if you really had to and pray the engine doesn't ping cause its game over as soon as it does.

[JimmyD3]

Very interesting discussion gentlemen, I learn something new every day. Thank you for the explanation.

[Dadtallica]

Hey thanks for the detailed responses fellas. So I think I’m hearing the answer is no lol.

[SIK1]

Very good answers from Oltos, and TryHard, just a few things to clarify.

Hitech uses flight test data for the flight models of his aircraft, as pilot notes can be anecdotal at best.

In Aces High engine management is greatly simplified. There is no mixture, or cowl flap adjustments. There is no thermal, or detonation damage to the engines. You can run the throttle firewalled all day long without damaging the engine.

Jugs, Hellcats, Corsairs, as well as many others used the R2800, and like the airframes the engines were improved, and refined throughout the course of the war. That’s one of the reasons you see a performance increase in the P-47’s and F4U’s as they progress. All production Corsairs used a two stage blower, the performance increase of the F4U-4 over the earlier marks has more to do with improvements of the engine, and induction system. Notice the chin intake on the -4 variant, as well as a four bladed propeller. There were also improvements to the supercharger that aren’t visible. I’ve always wondered why they didn’t use a four bladed prop on earlier F4U’s since the P-47’s used one from the beginning.

 

[Dadtallica]

Keep ‘em coming!

[potsNpans]

Great stuff, 

[TryHard]

I could be wrong but since the corsair has a bent wing it's engine sits higher than the P47 which means it can use a large 3 bladed prop rather than a smaller 4 bladed one.

The more blades you add to a prop the more drag it induces, technically the best propeller would be a huge 2 blade prop but it would need to be so large that it would hit the ground on landing which is why they came out with 3 and 4 blade props. In other words a 3 blade propeller is better than a 4 blade one as long as you can make it large enough to transfer all the power into thrust, which is why early corsairs all had 3 blade props. When the -4 came around the added horsepower would require a larger propeller which wouldn't fit so thats why they added another blade.

[SIK1]

The corsair has a bent wing because they wanted to use a thirteen foot propeller, and with a straight wing the landing gear struts would be to long (weak) for carrier use. So the engineers put a bend in the wing to shorten the struts.

I understand the number of blades/drag issue. What I'm questioning is why, when the P-47 had a thirteen foot propeller, (only an inch shorter than the corsairs) did they use a four bladed prop on the jug, and a three bladed one on the hog?

I know that there is a noticeable climb performance increase from the -1 to the -1A, mostly attributed to the change from the toothpick propeller blade to the paddle blade. In AH both have WEP, and the -1A will outclimb the -1. Iirc the birdcage actually has a slightly higher top speed, and that would be due to drag as the birdcage has a slightly smaller frontal area, and of course the toothpick blade propeller. I just wonder if there would be any performance advantages to adding a four bladed prop to a pre -4 corsair?

 

[TryHard]

Perhaps the reason the jug used a 4 blade propeller maybe because it was better at high altitude?

Is the P47D11 modeled with the "toothpick" prop or the improved paddle prop design? it seems like it climbs rather well for what it is.

[Dadtallica]

All great answers thank you. I was more referring to buffs and charging up the engines on the runway before taking off the brakes. I have had more than one person tell me this will help climb faster and larger bombers.

[Lusche]

All great answers thank you. I was more referring to buffs and charging up the engines on the runway before taking off the brakes. I have had more than one person tell me this will help climb faster and larger bombers.

Revving up the engine before releasing the brakes just gives you a few feet of extra runway space (more so in jets as they spool up much slower), but it has no impact on rate of climb after you get airborne.

[The Fugitive]

All great answers thank you. I was more referring to buffs and charging up the engines on the runway before taking off the brakes. I have had more than one person tell me this will help climb faster and larger bombers.

The B29 is a plane you do this in. Apply brakes, run up the throttle, give it a minute to get to max RPM, release brakes with a notch of flaps and it will get off the runway (most aren't long enough). For climbing faster, NO.

The idea is that if you dont run up the engine to full RPM first your burning a few hundred feet of runway getting up to full RPM and you might not have enough runway. But if you think about it, full RPM in the air are full RPMs. Your not going to climb faster. For quicker climbing you need a lighter load. Then that leads into what are your mission needs? Bombing a town? better to take 500 lbers, good splash damage and a good spread. Bombing hangers, 1000 lbers , a single drop in a formation, or reset your salvo to 3 and a single can drop them easy peasy.

The physics are modeled well in this game. flight models, aero, weight,effect, gravity on both planes and bullets. Some of the "details" are removed to make the game fun, and not a chore like adjusting cowl vents or throttle management so you dont blow an engine and so on. 

[Mongoose]

First, the flight models are based on the engineering specifications and real world testing of  the aircraft.  According to Hitech, "The physics of the airplane are as detailed and realistic as we can make them."  He also said (I am summarizing) that there are some things you just can't simulate accurately sitting at a computer desk as opposed to sitting in a real airplane.  That's why we have things like the pitch ladder.  Real WWII airplanes didn't have a pitch ladder, but in real airplane you feel the g forces through the seat of your pants, but you can't get that same feeling sitting at your computer desk. 

Second, Aces High does not include engine management because it would make the game very complicated.  I can fly a P-51, then land, and take off in a ME110 without having to learn all the engine management of the two airplanes.  Find some pilot manuals for WWII planes, or even modern planes, and compare the procedures for starting the engines and taking off.  You will find they can be very different.  This would be even more difficult since you are simulating this with a computer keyboard, and not the real controls in the different airplanes.  Best to leave engine management behind, and let us get on with the fun of flying the airplanes.

As has been pointed out, the P-38 and P-47 did have WEP.

No one has asked about the flight characteristics of the bullets.  Just like the airplanes, Hitech models the ballistics of the weapons as closely as possible, except that the bullets disappear when they run out of energy so the computer doesn't have to track them all the way to the ground.

Hope this helps.