Ju-88 a1 Jumo 211B BETA 1.08.18956

[Chromius]

The poor Ju-88 needs to brought up to spec. It is roughly 40-50kmh slow maybe more, which is also causing issues with the R-22 not being able to hold altitude

At 2250m (peak pre supercharger performance) with ata 1.25 and rpms 2400 on orange and trimmed for level flight @ 11,000 kg weight. I am only able to get 310 IAS which equates to 353 TAS @2250m. (Yes you can get on the step for a slight increase.)

All data available says the A-4 with Jumo 211J engines was slower than the A-1 with 211B engines due to the A4 having extra armor and load capability along with an addition bulge on the fuselage causing drag and the following charts claim A-4 data.

This performance graph corresponds to a Ju88 A-4, which was test flown without charge air cooler. The first two lines were flown at a gross weight of 13750 kg. The extended kg with a total weight 11500

http://www.ju88.equitatura.de/Ju88A-4/Performance/Leistung1.jpg

From http://www.ju88.equitatura.de/performance.htm

And these specs are also based on the A-4

5. Cruise

Enriching lever is in position "Normal".

a) Cruising speeds when mixture control is in position "Lean" ("Arm") and enriching lever in position "Normal":

Altitude V-w Supercharger P2((ATA) n (RPM)
300 350 low gear 1.15 2250
2000 390 low gear 1.15 2250
4000 400 high gear 1.15 2250
6000 400 high gear 1.10 - 1.15 2250

b) Maximum speeds when mixture control is in position "Rich" ("Reich") and enriching lever in position "Normal":

Altitude V-w Supercharger P2((ATA) n (RPM)
300 375 low gear 1.25 2400
2000 410 low gear 1.25 2400
4000 415 high gear 1.25 2400
6000 425 high gear 1.15 - 1.25 2400


In the CEM engine damage model I had the following happen which does not seem right. I was pushing my engines to see what the various limits were when I had a single damaged item, I immediately throttled back and set ata to 1.15 and rpms to 2200 Green/Green.

Engine 2: Water Pump Failure

Had a massive loss of power in engine 2 and much cooler oil temps in eng2
Lost 40-50 kmh in level flight.

Radiator and oil coolers were set the same for 1 and 2, water temps stayed steady.

Throttles were both at 33% for 1.15 ata, rpms and pitch both 2140/73% water 1=84 2=86 identical radiators 30%

Oil temp eng1 84c eng2 32c both coolers at 20%
Oil press eng1 7.4 eng2 8.2

Seems strange that I had some power on 2 but increasing throttle did nothing, yet the ATA matched on both engines set at the same throttle setting? I flew like that with no change to water or oil temps for some minutes.

[CaptainDoggles]

Well since the spits want more speed then the poor Ju-88 needs to brought up to spec.

It shouldn't be about "if they get this then we get that". Editorial comments like this don't help anyone and will just bring trolls out of the woodwork.

If the data shows that the 88 in game is too slow, it should be corrected on those grounds, not because some other aircraft is being corrected too.

[Chromius]

True, edited.

I guess I mentioned it because with the Spits and Hurricanes getting faster top speeds more in line with historical levels it will mean a much easier time of them closing and attacking the Ju-88's from optimal attack angles. At least with the Ju-88 historical higher speed there is a better chance at surviving the impatient fighter pilot.

[Crumpp]

It shouldn't be about "if they get this then we get that".

Exactly. They should be fixed because the performance and behaviors are not an accurate reflection of the aircraft they are supposed to model.

[KG26_Alpha]

Check the He111's performance also :confused:

[Crumpp]

So you quoted that a full day after I agreed and edited the initial statement.

I saw you edited it. I was agreeing with the sentiment and nothing on you.

;)

Here is a translation of the Ju-88 Flugzeug Handbuch a friend gave me.

Maybe it will help out.

[Chromius]

Anyway more Performance charts and testing. Edit: I will have to do some tests at 1.1 ATA and 2100 which will fall much shorter than stated performance.

Ju-88 a1 Jumo 211 B 11,300 kg load 4xSC250

http://img809.imageshack.us/img809/9922/ju88211b11t4x250header.jpg
http://img502.imageshack.us/img502/306/ju88211b11t4x250chart.jpg

Ju-88 a1 Jumo 211 B 12,000 kg load 2x500

http://img689.imageshack.us/img689/1395/ju88211b12t2x500header.jpg
http://img88.imageshack.us/img88/5858/ju88211b12t2x500chart.jpg

The part 1 is performance with bombs climbing and cruise. Part 2 is return flight after dropping the bombs and additional glide times from altitudes. No idea how much fuel was used after dropping bombs. Also fuel usage in litres per hour for different cruise settings are listed.

Note the drag on the loaded flight out to target w/ the 4x250 vs the 2x500.

Ok now my in game testing with no winds in mission builder. My level flight speeds were steady from 5-10 minutes along with the recorded fluid temps with cooler settings.

My conversion to TAS are based on ATAGs conversion which match up with other real world conversions. The IAS-TAS chart on pg 112 of manual is off, so I am not sure how this translates in game.

All 3 altitude/speed readings were from a fresh plane with the following load.

11,025 kg 30% Fuel (994 ltr) 18xsc50, 10xsc50, 2x500

2000M

1.2 ATA 2400 RPM 334 IAS 378 TAS (According to chart in post 1 we should be closer to 422 TAS)
Water 45% 78/83 Oil 35% 84/77 Ambient Temp 12c

2250m

1.2 ATA 2400 RPM 329 IAS 378 TAS (According to chart in post 1 we should be at around 426 TAS)
Water 40% Oil 30% (did not record temps on this one)

2500M

1.17 ATA 2400 RPM 333 IAS 388 TAS (According to chart in post 1 we should be closer to 425 TAS)
Water 40% 80/80 Oil 30% ?/? Ambient 8.5c

With Radiator/cooler full open 100/100 speed dropped 3 km/h to 330 IAS

Note: aircraft flys well at 1.3 ata and 2400-2440 but if you push to 1.35 or more with it warm engine damage happens fast.

Single Engine performance w/ same load as above. (Bombs still on board 11,025kg)

1500m

1.3 ATA 2400 RPM 250 IAS 275 TAS
Water 50% 88 Oil 50% 94

Climb possible 228 IAS .4-.5 m/s

Fuel Weight .756 kg per litre

Fuel

100% = 2019 L
50% = 1648 L
30% = 994 L
10% = 340 L

Note the Max the Fuel Gauges read in position 3 F/R is 837/831 Gauge will not drop till fuel is consumed below this point.

The 4/5 position (Left and Right wing tanks) always read 125/125 even with 0% Fuel. No matter what I do with the fuel switches nothing seems to happen always seems to draw from the F/R. No way to transfer fuel as we have no fuel transfer levers.


I should test it out with the values stated also.

I tested in the range I did as that is the peak performance area for pre supercharger use. It would be nice to test at higher altitudes w/ and without bombs, and lower altitudes with no bombs.

That is it for me 5 cups of coffee later and Saturday spent playing with this, lol. Please add anything you can find. I am interested if the fuel switches do anything at all, I tried every combination. (As per pilots notes.)

It would be nice to come up with fuel use l/h and figure out what is wrong with the IAS-TAS chart that comes with clod and the real world values using standard .02 OAT deviation, and if the clod chart actually matches in game TAS values.

[Varrattu]

The JU88-iL2CoD is still bugged and far away from the original JU88A-1. Here are some examples ...

When the operating lever is turned to position “Elevator and landing flaps” (“Höhenflosse und Landeklappe”) the flaps return to neutral positiion and are retracted.

Setting the main switch of the SAM-Kurssteuerung K4ü --automatic steering device-- to stage 1 the automatic steering takes rudder under contol. Ailerons and elevator are still under control of pilot. This feature should function at stage 2.

Setting the main switch to stage 2 the automatic steering takes rudder ailerons and elevaton under contol. This feature does not exist in the original.

When the automatic steering device is switched on, the signal lamp for the pitot heater simultaneously is switched on. The pitot heater switch is connected to auto steering on/off lamp.

The dive break position is shown in the tail wheel indicator. The original dive break indicators on the wings are missing ...

And so on ...

:confused:

[JtD]

Question regarding the red line in the chart in the OP: Why would an intercooler increase speed above full throttle altitude? I know it's irrelevant for the A-1, but still wondering.

[Crumpp]

Why would an intercooler increase speed above full throttle altitude?

It looks like a line added to the chart.

The principle is correct. The inter-cooler was designed to increase charge density.

IIRC, the general rule of thumb is for every 10 degrees of temperature drop there is a 1.8% increase in power.


The extended kg with a total weight 11500


However, I think the increase has more to do with the weight. If I am reading the post correctly, the extended line is some 2250Kg lighter.

[JtD]

The dotted black line is for 13.75 tons, the solid black is same power for 11.5 tons. The added red line is for the effect of inter-cooling.

Inter-cooling does increase charge density if air supply is unlimited, so for altitudes below full throttle altitude power and speed increase are there (6% in case of the Jumo 211F/J), however, above full throttle altitude air supply is somewhat limited. Very much like ram effects on the inlet side increase manifold pressure, inter-cooling reduces manifold pressure. The effect above full throttle altitude should be somewhat less than below.

In the meantime I've looked up range tables for the Ju 88 where speeds with inter-cooling are only higher below FTH, supporting my point of view. So I'm withdrawing the question, the red line is wrong. Back on topic, good to see a bomber getting some attention.

[CaptainDoggles]

In the meantime I've looked up range tables for the Ju 88 where speeds with inter-cooling are only higher below FTH, supporting my point of view. So I'm withdrawing the question, red line is wrong. Back on topic, good to see a bomber getting some attention.

Did your sources have a graph similar to the one posted in this thread?

I'd be willing to bet that this "red line" is just an intercooler performance line that doesn't drop off fast enough above FTH. Someone just copied the curve from the highest black line.

[Crumpp]

The dotted black line is for 13.75 tons, the solid black is same power for 11.5 tons. The added red line is for the effect of inter-cooling.


Maybe, the instructions are not clear.

Hence engine power stays roughly the same,

Increasing charge density will increase power at the same manifold pressure, above or below FTH.

This is also why aircraft experience increased performance in low density altitude conditions.

The intercooler on the Jumo 211 series functioned under exactly the same principle. Increase the charge density and you will increase power under all conditions.

It is a very simple concept.

Lower temperature means more air molecules in a given volume are required to create a given pressure.

It takes more oxygen to maintain the same boost pressure at a lower charge temperature.

Oxygen is off course what the engine needs to support combustion, more oxygen molecules means more power.

That is why if you look at an actual aircraft power chart for a turbo or supercharged engine, it will tell you to correct power for air temperature at the intake for the same manifold pressure.

The formula on the chart is

HP * SQRT (Temperature ratio)

BTW,

It is actually the density ratio but the chart I posted from the Lycoming O-360 series Operating Manual already corrects for pressure altitude.

If you were not running your power through a chart such as that, then power equals:

HP * SQRT (Density Ratio)

Density ratio is your Temperature ratio divided by Pressure ratio.

reduction of temperature means an equivalent reduction in manifold pressure

I see you edited your post!

The supercharger can produce a give pressure at a given density altitude above FTH. If we increase the charge density with our intercooler, then our power will increase above the same engine without the intercooler at the same manifold pressure and rpm.

It varies according to the standard formulation. It does not matter to the power production if we increase density at any point in the intake before the charge enters the combustion chamber, the effect on power is the same.

So, getting back to the thread and this sidetrack's relevance.

While we disagree on the shape of the curve, JtD and I are in agreement that the red line curve warrants an explanation.

It appears to be added after the fact and the data upon which it is placed on the chart should be made transparent.

[Crumpp]

I'd be willing to bet that this "red line" is just an intercooler performance line that doesn't drop off fast enough above FTH. Someone just copied the curve from the highest black line.'

That appears to be a very large power gain for installation of an intercooler.

I am wondering if somebody did not copy the curve from another graph with a different engine thinking they had the same engine. The Jumo 211 increased in power over its lifecycle like most wartime engines. Not all of the those power increases were incorporated into the JU-88A1 engines.

Make sense?

[JtD]

Did your sources have a graph similar to the one posted in this thread?
No, just figures, for instance, clean A-4:

No inter-cooling, 1.15ata/2250rpm:
300m: 365km/h
4000m: 410km/h
6000m: 425km/h

With inter-cooling, 1.15ata/2250rpm:
300m: 375km/h
4000m: 425km/h
6000m: 425km/h

[CaptainDoggles]

That appears to be a very large power gain for installation of an intercooler.I admit I didn't look too too closely at the graph.
I am wondering if somebody did not copy the curve from another graph with a different engine thinking they had the same engine.

...

Make sense?Yep that's a definite possiblity.

[Crumpp]

No, just figures, for instance, clean A-4:


Do you mind sharing the information source so it can be used?

[torric270]

[QUOTE=Chromius;453995]
100% = 2019 L
50% = 1648 L
30% = 994 L
10% = 340 L

Note the Max the Fuel Gauges read in position 3 F/R is 837/831 Gauge will not drop till fuel is consumed below this point.

The 4/5 position (Left and Right wing tanks) always read 125/125 even with 0% Fuel. No matter what I do with the fuel switches nothing seems to happen always seems to draw from the F/R. No way to transfer fuel as we have no fuel transfer levers.QUOTE]

I get 3304 for 100% fuel (fuel increases once airborne). On fuel switch: #1 is for fwd fuselage tank (not modelled) #2 Outer tanks #3 Inner Tanks #4,5 are oil tanks read in the right gauge 125L per eng, if you get an oil leak u can watch this number decrease (oil consumption not modelled)

To transfer fuel from outer to inner tanks, which are the eng feeder tanks turn on #6 for left outer to go to both, and/or #7 outer to go to both inner tanks. These are what is in the game, not by the book.

[ATAG_Doc]

I'm going to test again but I had a tough time getting the 88 up beyond 5000 meters. The 111 is easy compared to the 88.

[Jam656es]

I was pushing my engines to see what the various limits were when I had a single damaged item
http://www.rdox.info/01.jpghttp://www.rdox.info/02.jpghttp://www.rdox.info/8.jpghttp://www.rdox.info/9.jpg
http://www.rdox.info/0.jpg