Production rates

[harley]

ORIGINAL: Hard Sarge

Harley, is there anything written in stone about and the size of the tanks ?

pretty much it sort of looks like a 2 for 1 deal, just because the device says it is a 110 gallong tank, don't mean we got to keep it at 50 ? (unless the code does something with it)

No, but if we set the DT's to have endurance factors higher than they currently are then some AC will be unfairly advantaged or disadvantaged. I don't think having different 110gal DT's is the answer...

I just thought of another idea, but better for the Dev forum...

[Hard Sarge]

you may of misunderstood
 
wasn't think of different tanks, just if we increase tank size (okay what a 110 is worth 50, what if we increase the worth of all 110s to 70 ?)
 
you know, in the long run though, we could do a double tank, a 110 DT on a P-47 would not last as long as the same tank on a 51

[fochinell]

We are stuck with the 1 point of Endurance per minute, so the DT's are adding endurance at the rate of 1 minute per 2 Gallons (give or take)

I've also used the 1 for 1 rule of thumb, but applied it generally. With your estimates the XII and XIV would have a fuel-flow of 1.4 gallons per minute.

Looking at it a different way, how fast can a Spit VIII fly on a fuel-flow of one gallon per minute?

2,200rpm at +4lbs boost should give 61 gallons per hour for Merlin 63 or 64-engined Mk VIII. This will give different speeds at different altitudes, from 295mph TAS to 330. This isn't too far from the AFDU's approximate figures for 320mph at 20,000ft on Maximum Weak Mixture Power, which gave the VIII a range of 290 miles (reduced to 130 miles for the IX with it's smaller internal fuel capacity). This could be stretched by flying at the most economical throttle settings to 445 miles or 200 miles. The same source gave a MWMP range of 134 miles for the XIV, at 350mph at the same altitude. A different report from the same source (the AFDU, who should have known what they were talking about) gives figures of 365 miles for the LF.IX, and 375 miles for the XIV.

The same report stats that the 90 gallon ST stretched the range of the LF.IX by 410 miles and the XIV by another 315 miles. Dividing the range figures by half should give some reasonable combat radii.

One of the many problems with this is that I know for a fact in 1942-43 Spitfire V units flew at lower revs and boost until in the combat zone, and then increased to up to 2,650rpm and +4lbs boost. This would equate to a speed increase from around 220mph to 300mph. The engine revs and supercharger boost figures would be identical with the Merlin 60 series, but the speed would be proportionately higher at higher altitudes (as would the fuel consumption - the figures quoted would mean 56 gallons per hour in a Merlin 45/6-engiend Mk V and 71 gallons per hour in a Merlin 63/4-engined MK VIII or IX.

So really there were two cruising speeds - one for climb, assembly and over-water transit, and then another for faster cruise in the combat zone. This ties in with practice with the 8th AF fighter units.

So much for the historical guff, this is no help to you or HS. What seems clear to me is that you should be free to simplify and approximate. I'd suggest keeping high cruising speeds (nobody was going to fly over the Reich at 200mph waiting to be bounced) but stretch the endurance slightly to fudge in a reserve flown at more economic settings.

Set that as the Cruise Speed, the end as the actual tankage and then everyone lines up... It's not perfect, but it's reasonable. The main reason it hasn't been done like this is lack of accurate data on performance...

Now we just need this for all the game types... [maniacal laughter to fade...]

It's fine to have the range, and the estimated cruise, but that means calculating the end from extrapolated data...

You're completely right. But then I don't see how you can avoid this.

There's also the time factor - HS has so much to do on his end, then get it tested. Sometimes it's just easier to make things feel right.

100% agreement here.

[Hard Sarge]

just wondering, when they are talking cruise and boost, are they talking normal cruise or combat cruise

(hassle with alot of US ranges, they are maining based on training ranges, were all is nice and safe)

Hmmmm, some of those stats worry me

okay, remember with something like a 47, it could of carried even bigger drop tanks then it did, but...

main idea for DT's, you still need more internal fuel, then external fuel

does you no good in combat to have 500 miles with of Drop tank fuel, when you only have 160 miles of internal fuel

[fochinell]

just wondering, when they are talking cruise and boost, are they talking normal cruise or combat cruise

The AFDU figures are for "high-speed" cruise when enemy contact was likely. Formations would fly faster when the enemy were actually in sight or when they had radio warning of enemy activity. In theory the figures include a reserve for combat and climb. However, in reality, formation leaders frequently went over those guidelines and even the Group planners seem to have exceeded them on occasion (e.g. escorting the transport lift for Arnhem). The explanation for this seems to hinge upon expanding the length of mission routing which was flown at lower power settings, as well as the appearance of closer diversionary airfields on the continent reducing the reserve requirement. The formation leaders would fly as aggressively as they wanted to.

There are frequent examples of this - like 133 sqn running out of fuel over Britanny, some Spit escorts for the Regensburg/Schweinfurt raids on 17 August '43 actually running out of fuel over the Channel and gliding home. I was looking up evidence for the XIV using DT's and on 6 September '44 610 sqn did a sweep from Lympne to the Rhine across Holland along with the other XIV units in the same wing (402 and 350 sqns), using 90-gallon DT's. The aircraft were in the air for 2 hours, but most of them still had between 40-60 gallons left after landing back at Lympne.

So what does all this verbiage mean for the game? not a lot, and that's unhelpful - the range and endurance figures I've given, while used historically, were not definitive. Which brings me back to harley's point that you've got to approximate as you see fit in the interests of balance.

main idea for DT's, you still need more internal fuel, then external fuel
does you no good in combat to have 500 miles with of Drop tank fuel, when you only have 160 miles of internal fuel

Yup. The internal fuel governs how far the aircraft can fly on the return to base leg. In the case of the Spitfire, it can only fly that far - i.e. as far as it can get on 85 gallons internal fuel for the V/IXC minus take-off and combat reserve from the internal tanks. The DT's can take them to that point, but even if they had fuel for going further, this would be of no help on the return leg after combat, where the DT would have been jettisoned.

[Hard Sarge]

fochinell
 
lets go over ranges again
 
I am not happy with what I have for the Spits at all
 
at a range to target of 248, I am covering the raid from take off to target and back
 
at a range to target of 278, I am making it to the target and a little beyound
 
with a Spit IX, I am showing a Radius of 290, so both of those targets should be well with in my range (the V would be a little shorter, but should still be able to cover most of the way home)
 
(also, I think the form up point is screwing with this, in RL, they would of flown to a point, to join the raid, instead of flying to the take off base, join the raid and then fly to target)
 
 
 
 

[fochinell]

lets go over ranges again
I am not happy with what I have for the Spits at all

What stats do you want to use though? I've provided some historical ones, but I can give you my own if you want those. But whatever you use has to have some internal consistency, which means all the aircraft ranges/endurances need to be worked out along the same lines, whatever those lines are.

at a range to target of 248, I am covering the raid from take off to target and back
at a range to target of 278, I am making it to the target and a little beyound

with a Spit IX, I am showing a Radius of 290, so both of those targets should be well with in my range (the V would be a little shorter, but should still be able to cover most of the way home)

A Spit IX with a 90-gallon DT should manage that, in my opinion, but only by taking into consideration the issue of repositioning vs flying from home base to departure point and then out to the force to be escorted, as you mention.

I'd give the Spit IX a radius of 200 miles on internal fuel (75 mins endurance @ 324 mph cruise divided by two and rounded down), a Spit XIV a radius of 215 miles(72 mins endurance @ 364 mph divided by two and rounded down to nearest multiple of 5). This assumes the Spit IX has 85 gallons of internal fuel, and the Spit XIVC 110 gallons of internal fuel which it consumes 25% more of than the IX per minute in the air. The greater range of the XIV comes from 40% more internal fuel.

Using this means a IX should *get back* from up to 400 miles into enemy territory, assuming it got out that far on external fuel (just possible to believe with a 90-gallon DT), although this is not credible when fuel reserves for combat, etc, are taken into consideration. I'd opt for something like 300 miles to take that into consideration, or 50% more than the basic radius on internal fuel.

The Spit XIV shouldn't manage this proportionate performance, as it carries less fuel externally than internally, but this should be balanced by the faster cruising speed to make the range extension with the drop tank similar. Assuming that it consumes 25% more fuel than the IX, a 90-gallon DT should last it 56 minutes, or 339 miles. Divide that by two (and round down)and you get an extra 165 miles. This is a little optimistic to my taste, so I'd reduce it by 50% to get 80 miles.

This would give the IX a range of 300 miles with a 90-gallon DT, and the XIVC a range of 295 miles with the same. I'd use the XIVC figures for the XII. The variants with more internal fuel complicate this.

Using the same formula used for the IX (same engine, same airframe), the VII and VIII should manage 40% more endurance and range down to the 40% extra internal fuel they carried. So I'd give them a radius on internal fuel of 280 miles (105 minutes endurance at 324 mph, divided by two, rounded down), but the same extension due to a 90 gallon DT as the IX meaning a further 100 miles to the radius. Total of 380 miles.

The IXE should manage even further (150 gallons of internal fuel versus 120 in the VII and VIII, giving 131 minutes endurance at 324 mph, same equation as used above) giving a radius of 350 miles. The XIVE should have a similar benefit from increased internal fuel (175 gallons vs 110 in the XIVC), giving an increase of endurance to 115 minutes and increase in radius on internal fuel to 345 miles.

There are quite a few approximations and fudges chucked into this, but it gives the following figures for radius for the following Spitfires on internal fuel and then internal fuel plus a 90 gallon drop tank:

Mk VII and VIII: 280 miles/380 miles
Mk IXC variants: 200 miles/ 300 miles
Mk XIVC variants: 215 miles/ 295 miles
Mk IXE: 350 miles/450 miles
Mk XIVE: 345 miles/425 miles

On this basis, a Spit IXC should have no trouble getting out to a target 250 miles away using a 90 gallon DT (assuming no combat occurs en route, etc), while a XIVC should be similar. The figures are optimistic for various reasons, up to 20% in some cases to my mind and mostly down to issues like fuel reserves, but then this compensates for the "distance to departure point from home base" effect.

FWIW, the whole basis for my estimates is endurance worked out at about 1 minute per point of endurance for the Spit V, with a 13% decrease in endurance for the Merlin 60 series and then a further 25% decrease for the Griffons, multiplied by the cruising speeds you've used.

[Hard Sarge]

Well, this is not working right
 
this is what the game is telling me on the info pages
    , End, DT, radius, range at 15000 ft
VB, 120,   N ,  270, 510
VC, 120,   N , 274, 516
VII, 165,   Y , 310, 744 (1 75 gallon)
VIII, 155,  N , 383, 736
FIX, 125,  N , 302, 570
LFIX, 125, N , 302, 570
HFIX, 160, Y , 314, 732 (2 100 l, may change tank)
LFIXE, 160, N, 388,
LFXII, 140, Y, 253, 639 (1 75) 
LFXIV, 135, N, 370
LFXIVE, 180, N, 494
 
 
so basicly, but the numbers, I am already past the End, radius that the planes should have, and still they are short
 
I had a lot of trouble getting the 51 to get to where it was suppost to get
 
oh boy
 

[fochinell]

Well, this is not working right

I was hoping there was some internal logic to it....

so basicly, but the numbers, I am already past the End, radius that the planes should have, and still they are short

I don't mind them being shorter-legged than my estimates, at least to some degree. What I'm hoping is that you can get the different models to reflect their proportionate radii and endurance more accurately, without buggering up the gameplay. But I have no idea if it's possible at the end of the day.

I had a lot of trouble getting the 51 to get to where it was suppost to get

Can you repeat the same process, but modify the variables? All of my rantings are contingent upon the game model using basic mathematical models (such as crusing speed x 1/2 endurance equalling range) which in turn can be used with different performance figures derived from the historical performances of the different aircraft types. If that ain't how it works, I'm up s**t creek and none of this makes any difference.

Sorry to hit you with all this, I had no idea it was so difficult. [:(]

[harley]

HS, do you want me to post the exact range calculations?

Gavin - I completely re-jigged the fuel consumption, it was way out of whack previously. If HS says it's OK for public consumption, then I'll run through it...

[Hard Sarge]

Harley
Go ahead
 
Gavin, the hassle is not in getting the ranges right, I can work that in, what it is going to do, is make the planes look like I am a Fan boy trying to help out one side or the other
 
if the plane info says we got a radius of 300, but I got to give it enough end to fly to 300, then I may have to give a radius of 400-450
 
(ahhh, I had most of the planes fined tuned, before Harley got the new fuel system to work, and have not had the time with the right program, to do heavy work on it)