Project Martin A-30 Baltimore

[Ivan]

Hello Aleatorylamp,

You are inventing things at this point.
Sometimes you have to, but I believe in this case you really do not need to.

What does the actual throttle quadrant on a R-2600-13 engine actually look like?
Do any of them have the "Gated" Throttle that you are proposing?

You do realise of course that having a voluntary 90% non-WEP limitation is really no limitation at all, right?
Nothing stops the pilot from running continuous 100% power.
Perhaps that is what you are trying to do.
I personally don't like the idea because I believe that in this case WEP should have a limitation.

WEP durations vary all over the place:
The DB 601Aa engines and their derivatives had a 1 Minute Take-Off setting
The Merlins had typically 5 minute limits
The R-2800 Ws had 10 minute limits because of anti-detonant supply
The BMW 801D-2 series in later versions had pretty much as much WEP as "needed"
There really isn't a standard but from a practical standpoint, I believe there should be a restriction of some kind.

If you are really intent on doing something like a gated throttle, perhaps you should consider revising the AIR file so that the extra 10% power is controlled by the F10 key rather than a voluntary throttle setting.
Your gated throttle is really no restriction and has the same issue as the CFS implemented WEP anyway.
If you are going to increase critical altitude with WEP anyway, why not do it via the CFS mechanism?

I actually still prefer the numbers I was getting with the B-25C but mostly that is because I was tuning it to get the flavour *I* wanted.
I get the impression that your goals may be a little different.
Keep in mind that the actual flight performance is the goal here.
No one out there besides a couple fanatics will be measuring your engine output anyway.

- Ivan.

[aleatorylamp]

Hello Ivan,

Thanks for your post! I agree that there is a point here. You do realize that I value your opinion and ideas very much, and I will act accordingly. Yes, I was inventing things, but the reason was to find a viable solution - which seems not to be so viable after all! Not to worry, however. Let´s see if there´s a different way!

I know that probably no one will be measuring my engine output in reality, but that´s not really the point. I want to see if it is possible to get the engine running more correctly, closer to the real thing.

The reason I was developing this idea a bit further was because of the F10 WEP giving an exaggerated, unreal power increase at high altitudes, in fact well over 200 hp, and that this does not happen if WEP is incorporated into the normal full travel of the throttle lever. I thought I had indeed arrived at performance figures which were more realistic than with a WEP achieved through F10.

Of course this idea relies on the user´s knowledge that in reality, an excessively long use of this kind of WEP, would in reality destroy an engine. On reflection now, however, this seems to be impractical after all, because it facilitates an unreal prolonged use of WEP!

Well, I´ll see if I can find a way with F10 WEP, to control the afore-said altitude power surge in a different way! ...Possibly by further curbing boost gain values... In any case, the experiments are interesting!

Update:
The main problem with F10 WEP is that in order to get the right Manifold Pressure readings at altitude, WEP and NON-WEP require different Boost Gain entries in the .air file!
Rather frustrating, I must say! I´ll have to see if there´s a way round this... That´s why it worked so much better with the WEP-Within-Throttle-Lever.
At the moment I´m drastically reducing Emergency Power Press Change Rate parameter, which seems to be doing something. I wonder...

Thanks again, and cheers,
Aleatorylamp

[aleatorylamp]

Hello Ivan!

I´m beginning to seriously doubt whether the R-2600-13 engine actually had WEP as such, given the difficulty in implementing it in CFS1. What kind of engine WEP did the CFS1 programmers have in mind when they implemented WEP with superchargers in this simulator? Of the 3 kinds available, water injection, methanol-water injection and supercharger boost, the only one that occurs to me as being of any use here is the supercharger boost, but perhaps that is also not really the case.

The blower on the R-2600-13/29 is in use all the time, either in low or high, for all different flying powers, so the blower itself is not a WEP thing, but seems more like a general booster without any extra WEP Boost.

Perhaps this would explain why it was working so well with the 44 MPSI Max Manifold Pressure setting, without any WEP implemented.

At the moment, with 39 MPSI Max Manifold Pressure and 5 MPSI Emergency Power Manifold Pressure Increase, even the Emergency Power Press Change Rate reduced from 0.52800 top 0.10000 is really helping only slightly.

I´m looking for more precise information regarding the use of the 1700 hp military power. From what I have seen so far, it seems to have been 5-minute Take-Off power as well as 5-minute Emergency maximum, although the 5 minute are my own conjecture, as I haven´t seen any comments regarding the length of its use.

Have you got any rather more specific views on the issue of this particular engine?
By the way, I did notice the absence of any WEP implementation in the MitchellC .air file that you sent.

Not that I want to argue... I just find this rather confusing.
Sorry to be such a pain, but I´m starting to go round in circles.

Cheers,
Aleatorylamp

[aleatorylamp]

Hello Ivan,

The investigation continues... It´s getting interesting again: Maybe there IS light at the end of the tunnel.

Halving Emergency Power Pressure Change Rate value had produced no satisfactory results, and leaving it at one tenth was better, although I didn´t understand what was happening very well, so I left it at zero, discovering that above critical altitude, WEP falls off very rapidly! This seems to point towards a possible solution.

Update:
Leaving it at zero left insufficient manifold pressure at 12000 ft, which the Data Sheet specifies at 41, so I set it at 0.064, to get this exact. Even the 1726 Hp reading is very near the 1700 Hp specified here. Nevertheless, at 15000 ft, the 0.064 entry is too low to get the specified 39 MPSI here, although the 1544 Hp reading here is very near the specified 1500 Hp reading for 15000 ft.
Then, increasing it to 0.1, I got 37 MPSI here, which is still a bit low, although the HP reading is very good. Now the 12000 ft MPSI is at 41.6, which could be acceptable. I´ll just double check the Hp readings and see what comes out.

Presumably this behaviour for this kind of booster is in reality quite correct, so this adjustment of Emergency Power Pressure Change Rate seems to be hitting the nail right on the head!

What would you say? Have you ever experimented with this parameter?

Cheers,
Aleatorylamp

[aleatorylamp]

Hello again!
Of course, critical altitude being 13500 ft, is just between the two reference altitudes with their Hp and MPSI values given in the Specific Engine Flight Chart, the lower one at WEP and the higher one at Maximum Continuous:
12000 ft, 1700 Hp, 41 Mpsi Boost, WEP
15000 ft, 1350 Hp, 39 Mpsi Boost, NON-WEP
Now the thing is to find the ideal Emergency Power Pressure Change Rate value (which affects WEP) and Boost Gain value (which affects non-WEP), to get both above mentioned Mpsi values right! Not exactly a piece of cake, but not an excessive mouthfull either, I suppose.

Update:
-------
There are two more reference altitudes, also with WQEP and without WEP, namely:
4500 ft (WEP
6700 ft (NON-WEP)
...albeit with LOW-Blower (the higher altitude reference numbers were for HIGH Blower) - but we only have ONE Blower speed...
Also, There seem to be 2 types of extra boost (WEP): Take-off, with 44 Mpsi, and then Emergency Maximum, with 41 or 42 MPSI depending on altitude, but only one WEP is possible, so it will have to be with 44 Mpsi. Some values are just not possible to get, because there is only one blower speed, and one WEP. However, despite this, the results of my efforts are quite pleasing:

Performance Aims:
WEP (For take-off and Emergency Maximum):
Sea Level: 1700 Hp, 44.0 Mpsi, 305 mph or higher
4500 ft: 1700 Hp, 42.0 Mpsi
12000 ft: 1700 Hp, 41.0 Mpsi, approx 320 mph
15000 ft: 1547 Hp, 36.4 Mpsi, approx 320 mph

NON-WEP max.
6700 ft: 1500 Hp, 38.0 Mpsi
15000 ft: 1350 Hp, 39.0 Mpsi

Entered values:
Boost Gain 2.15
Max Manifold Pressure: 38
WEP Pressure Change rate: 0.0625
Manifold Pressure Increase for WEP: 6

Performance Results:
WEP:
Sea Level: 1701 Hp, 44.0 Mpsi, 310 mph
4500 ft: 1757 Hp, 44.0 Mpsi, 316 mph
6700 ft: 1785 Hp, 44.0 Mpsi, 320 mph
12000 ft: 1726 Hp, 41.0 Mpsi, 323 mph
15000 ft: 1547 Hp, 36.4 Mpsi, 318 mph

NON-WEP max:
Sea Level: 1481 Hp, 38.0 Mpsi, 302 mph
4500 ft: 1485 Hp, 38.0 Mpsi, 307 mph
6700 ft: 1558 Hp, 38.0 Mpsi, 310 mph
12000 ft: 1584 Hp, 38.0 Mpsi, 318 mph
15000 ft: 1497 Hp, 35.4 Mpsi, 317 mph

So now this is a little bit better, I would venture to say!
Cheers,
Aleatorylamp

P.S.
An interesting next step would be to fill in the speeds corresponding to the rest of the operating Conditions indicated in the Specific Engine Flight Chart, below the Take-Off, Emergency Maximum and Maximum Continuous, like Economical Maximum, Minimum Specific Consumption, Minimum Cruising and see what happens with the Conditions to Avoid.
A.

[Ivan]

Hello Aleatorylamp,

A couple days ago, you pointed out that my B-25C Mitchell AIR file did not have WEP implemented at all.
You are of course correct.

Please take a look back at Post #48.
I was stating back then that you needed to make a few choices as to what you were trying to achieve.

A Take-Off Rating IS a an emergency rating of sorts.. Typically it is of very limited duration.
I chose to ignore the time limitation on my implementation of the MitchellC AIR file, BUT
I also left the Sea Level power only at 1618 HP instead of the 1700 HP Take-Off power level.

The reason I did this is (as I have stated in many places) that I want a "Best Fit" of the power curve rather than an exact match at only one or two points. This is the reason I don't like the "1%" solution of matching performance very closely at just two points in the altitude range.
With only 1618 HP at 500 feet, the power at intermediate altitudes will still be way over 1700 HP.
Of course it will also be a touch low at Critical Altitude but the PERFORMANCE will be a closer match in most places.

You are going for 1700 HP at Sea Level and are not far off 2000 HP at intermediate altitudes which is why I think it makes sense for you to have a limit of some kind.
I figure that at worst, I am about 80 HP too high or too low.
I figure that your AIR file is more like 250 HP too high in places which is why a WEP limit makes more sense.

My goal is generally to use this game as a simulator. I want a 400 MPH Japanese Zero but also realise that it makes no sense from a historical or tactical perspectie, so I have never bothered to create it.
Just keep in mind that the Baltimore was an early war commercial bomber.
It wasn't a world beater and it wasn't a speed demon.
If it were, it may have remained in service much longer than it actually did.

- Ivan.

[aleatorylamp]

Hello Ivan,

Thanks for your post and your instructive thoughts and explanations on the Mitchell C power distribution. I agree that for the 600 Baltimore MkV units produced with the souped up 1700 Hp engines, an F10 WEP implementation is more fitting!

As you say, with the Baltimore, I was getting strong 250 Hp excesses at different altitudes. That´s why I had eliminated F10 WEP, although this of course then allowed for erroneous continuous use of Emergency Boost like you pointed out.

Nevertheless, as far as the power curve was concerned, the Baltimore .air file, like your Mitchell .air file, seemed to be closer to the correct power readings without F10 WEP in it, and these were still better than the ones I am getting now.

I have re-impemented F10 WEP, having managed to find possibilities for correction not only with Boost Gain adjustments like you said, but also with WEP Press Change Rate to curb the F10 WEP peaks, and this has now improved the .air file considerably.

The 250 Hp peaks you mention have long since gone, both in the non-F10 WEP version and the present F10 WEP version.

Now the only real problem-peaks are the 127 Hp excess at 15000 ft and the 85 Hp excess at 7600 ft, but in contrast, these peaks don´t affect the speeds, which lie within the expected performace range for the MkV model, so perhaps they are really not a big problem, depending on one´s appreciation of the whole thing, of course.

Although speeds are OK, RoC could be too high in some places, (which I still have to test), and I could go a bit more conservative and reduce the whole envelope by about 75 Hp (compensating with Zero Lift Drag to maintain the speeds), although this would make Hp go a bit under in some other places.

However, I don´t know if that is a good idea, because as you say, this simulator has a game facette which is also to be taken into account. What would you think?

So... F10 WEP or non-F10 WEP? It´s like the English say: "Sixpence of one or half a shilling of the other", although in this case F10 WEP is better, I suppose.

Cheers,
Aleatorylamp

[aleatorylamp]

Hello,
Just a short correction: I missed a very obvious indication on the R-2600-13 Specific Engine Flight Chart in the right column, stating a maximum of 5 minutes for TAKE-OFF and EMERGENCY MAXIMUM operating conditions. Sorry about that!
Cheers,
Aleatorylamp.

[aleatorylamp]

Hello Ivan,
In tune with your endeavour of fitting the whole power curve as opposed to only a couple of points on it, I have been tweaking the engine parameters, and with some minor adjusting (2.15 boost gain, 0.0625 Emergency Power Press Change rate, 0.54 Zero Lift Drag), I have managed to considerably reduce the excessive power in the areas where I was over specification. I also ever so slightly increased the friction graph, and gave the torque graph a tiny reduction. The results I believe look very pleasing indeed:

S.L.
WEP: 1701 hp 44 mpsi 309.5 mph (1 hp over)
Non-WEP: 1435 hp 38 mpsi 297.3 mph

4500 ft:
WEP: 1754 hp 44 mpsi 315.0 mph (54 hp over)
Non-WEP: 1482 hp 38 mpsi 305.3 mph

6700 ft:
WEP: 1787 hp 44 mpsi 318.5 mph
Non-WEP: 1511 hp 38 mpsi 308.0 mph (11 hp over)

12000 ft:
WEP: 1723 hp 41 mpsi 320.9 mph (23 hp over)
Non-WEP: 1582 hp 38 mpsi 316.6 mph

15000 ft:
WEP: 1483 hp 35.4 mpsi 315,6 mph
Non-WEP: 1533 hp 36.4 mpsi 317.3 mph (33 hp over)

Probably, it can´t get much better, I´d wager.
Thank you very much indeed once again for your inestimable and motivating help and comments!
Cheers,
Aleatorylamp

[Ivan]

Hello Aleatorylamp,

I must congratulate you for pointing something out that should have been obvious but that I and everyone else had overlooked.
SERIOUSLY: THANK YOU!!!!

Back at Post #78, you did some experimenting with "Emergency Power Press Change Rate".
Although you did not get the results you were looking for, it got me to thinking and experimenting a bit.
I now have some useful (though in hindsight rather obvious) information to convey.

This number (whatever it is called) has the same 0.5280 value in every single stock AIR file that has WEP with the exception of the stock FW 190A. This aberration can be easily ignored because it is pretty much common knowledge that the WEP doesn't actually work on the stock FW 190A.
If the stock AIR files were implemented correctly, this value should be 0.0000 for the P-47D which it is not.
Without basic knowledge, one has to study existing flight models and one has to presume that the existing values are as they should be.
This simple fact caused me to overlook the actual purpose of the value and conclude that the WEP implementation in CFS was simply incorrect.

I now feel quite stupid and a bit embarrassed for having made that statement so often and with such certainty.
At some point I will have to go back and post this in the Engine Tuning Tutorial as well as the Warhawk thread.

The supercharger implementation in CFS actually works reasonably well if the parameters are specified correctly.
The value you have been adjusting is actually the WEP Additional Supercharger Boost Gain.
It is the additional boost gain over the normal supercharger boost gain when WEP is engaged.
For gated throttles such as on the Spitfires and Mustang, it would have some fractional value because the critical altitude is increased when the throttle lever is pushed "Through the Gate".
On regular Anti-Detonant type WEP implementations, it should have a value of 0.0000 because supercharger boost gain does not change at all.....

I will need to go back and fix quite a few AIR files to correct for this factor.

On some AIR files, it makes almost no difference while in others such as the P-40 series, it makes a great difference.

- Ivan.

[Ivan]

Hello Aleatorylamp,

I am a bit curious as to where you are getting your performance data for the Baltimore Mk.V.
Specifically, I am wondering how you came to the conclusion that the Sea Level speed was something over 305 MPH.
What do you think of the accuracy of the Page 112 Data Table regarding Sea Level Speeds?

- Ivan.

[aleatorylamp]

Hello Ivan,
Thank you for your posts! I´m glad that I have been able to contribute with my little grain of sand, (as the Spanish say). It did seem a bit strange that with all the provisions available for superchargers, some aspects didn´t seem to work quite correctly in CFS1, and by chance or out of curiosity, I started poking around in this "new" WEP parameter, and discovered that it helped tremendously. I´m also glad that your P-40 will benefit from this find!

Now, contrary to my previous insistence, it seems that F10 WEP does actually work much better than implementing WEP in the last 10% of the normal throttle travel, like I was saying before with all my insistent certainty. I suppose it is normal that we all defend our arguments until new information appears which makes us change our minds.

Another example is the Baltimore 305 mph sea-level maximum speed.
I know that for the early Baltimore MkI it was 284 mph, and at altitude, 305 mph.
For the souped up MkV model, I have to say that I have found no concrete information about sea-level speed. My 305 mph speed here is an educated guess which well might be wrong, but is fundamented on the following:
Several sources state a max. speed of 320 mph for altitude (12000 or 15000 ft).
One source says even says 329 mph, but we can ignore that one.
Quite a few other sources just state a maximum of 305 mph for the MkV without specifying altitude, so I took this one to be the sea-level max. speed, and also, because of the statement about this machine´s top speed being generally above 300 mph.

At the moment my .air file is slightly over at 309 mph for sea-level and just under at 317 mph for 15000 ft, but now that I have found a way to separate WEP and non-WEP speeds, and I am still trying to get it down a little more for sea-level, and up a bit for 15000 ft, so I´m not quite there yet.

Update:
A better reasoning to calculate sea-level speed could be:
As MkI = 287-305 mph, diff.=18, then MkV = 320-18=302 mph.
But then again, we do not know how they souped up this engine to 1700 Hp. Was only by increasing WEP turbo-boost? ...or did they increase turbo-boost throughout? ...or also non-WEP power? Another detail could help: Cruise was 225 mph for the MkV, and 230 mph for MkI/II, so they must have increased non-WEP too...

But there´s a problem for the moment:
If I reduce S.L. top speed to 302 mph, the 12000 ft 320 mph speed also goes down to 315.5 mph, and the 15000 ft top speed even more, as it is already 3 mph slow.

Another thing: I´m afraid don´t have the Page 112 information you mention, to know the correct speed which it should have at sea-level. I´d appreciate your pointing out where this page 112 is.

Cheers,
Aleatorylamp

[aleatorylamp]

Hello Ivan,
I remember now that Smilo posted a Page 112 Data Table, but unfortunately the resolution was such that I could not read it, and he mentioned a few things on it - translating from Polish.
You then mentioned that you have a better copy which would of course come in handy.
Incidentally, I also found another text, stating 320 mph for the MkV at sea-level, so there are all sorts of data which could well be way out, ...or not... I don´t know.
Well, we´ll see...
Cheers,
Aleatorylamp

[Ivan]

Page 112 Part 1.

[Ivan]

Page 112 Part 2

[Ivan]

Now for the discussion.
Hopefully I can finish this before I get kicked off the computer.

Up until last night when I edited it to put in changes in description, FDECtrl.txt had a note that this WEP Additional Boost Gain field was typically either zero or 0.528 but without further explanation as to function. Even AirEd does not have any useful help on this field.
It actually took me a little while to figure out what the actual effect of this field was after you gave the hint that it changed the WEP effect above critical altitude.

The AIR file still has a lot of things that are not readily done such as WEP time and effects, Direction of propeller rotation, etc.
Or perhaps we just don't know where to adjust things yet.

Time for more exploration into AIR files.

Hopefully this version of Page 112 Tables is more legible. I can read my copy fine but the upload may reduce quality.

Smilo already pointed this out: At the bottom of the table, it mentions the Sea Level speed of the early Marks as 284 MPH.

So what can we do with that information assuming that we believe it to be correct?

From a quick observation of the Baltimore in various versions, the shape is basically the same.
There are obviously some differences with the Mk.IV with a Boulton-Paul 4 x .303 cal machine guns.
The drag would be quite a bit higher with such a prominent gun station.
The Mk.V was a little better off with a Martin 2 x .50 cal turret in its place.
The bottom line is that from an eyeball analysis, the drag of all the versions was pretty comparable with a slight advantage to the very early version.

In looking at the Engine outputs, they varied from 1600 HP, 1660 HP, to 1700 HP.
The difference from low to high was not more than 100 HP or so.
So why was the Mk.V faster at altitude if the power output was similar?
The simple answer is that the critical altitude was raised presumably because of a better supercharger.
The same power in the thinner air gave a bit better speed.

So how do we estimate SEA LEVEL speed?
Air density is the same, and drag is the same, so the difference will be entirely due to power differences.
(and some negligible to minimal effect from Prandtl and Glauert.)
So with a maximum difference of 100 HP Take-Off / Emergency rating, the speed increase would be the cube root of the power ratios.

Assuming 285 MPH on 1600 HP, that would give approximately 291 MPH on 1700 HP.
Note that if it is really 285 MPH on 1660 HP, 1700 HP would only give 287 MPH....

This is on the assumption that drag is unchanged, but in reality, it is probably higher for the Mk.V because of the turret and also because it probably was a heavier aircraft and also the cube root estimate is an ideal case.

That is why I was guessing that the Sea Level speed was probably the same or pretty close.

Hope that makes sense.
I am curious about the other testing reports you mentioned.

- Ivan.

[aleatorylamp]

Hello Ivan,
Yes, the attachment is legible. Thanks a lot!

Your careful reasoning sounds very plausible too - more than just an educated guess. Actually, I remember a similar line of thought you expressed a few weeks ago along the same lines, only that I was still a bit stubborn in my idea of keeping the speed a bit above 300 mph.

Presumably the contradictory information available has its origin, as so often happens, in errors along the chain of reports coming from reports, or probably even worse, inventing information to fill in gaps where the data was only available for some models and not for others.

So, in a nutshell, you are suggesting a WEP 291-320 mph speed range between sea-level and 12000 ft for the MkV. In effect, the MitchellC .air file, with correspondingly adaptated weights and fuel, would give a very similar result of 270-316 mph for a MkI supposition.

Very good. I´ll see what I can do.
At the moment, after increasing Drag to get sea-level speed down to 291 mph, of course the problem remains that altitude speed is too low, and not even playing with Induced and Zero Lift Drag, does it improve. The low manifold pressure specified at 41 for WEP at 12000 ft is the culprit here, I increased that to 44 there, like it is in the specs for lower altitudes, but of course, then the Hp shot up from 1723 to 1851, which is a bit much, and I´m still 6 mph under the desired 320 mph for 12000 ft.
Update 1:
---------
What I´ll have to do then is to reduce power and drag. This way I´ll get the speed up and reduce the power peak at altitude, although it will reduce sea-level power a bit, but as speed will be OK, it won´t matter there. Well, we´ll see how it goes.
Update 2:
---------
The best I can get is 292-316 or 295-317 mph, and that with only 1628 Hp at SL and a surge of 1791 Hp at 12000 ft - a difference of 163 Hp.
The difference here is similar to that in the MitchellC .air file, which was 1618-1780=162 Hp.
I would tend to be reluctant to accept CFS1´s lack of capability in reproducing an accurate engine performance envelope, but, what is amiss here? Why can´t we get 1700 Hp at sea level with 291 mph and 44 Mpsi, and 1700 Hp at 12000 ft with 320 mph and 41 Mpsi -(OK, I´m flexible and allow 44 Mpsi here...). Something must either be wrong with the published specifications, or with the simulator aerodynamics.

Now I´ll try putting friction at 125 and adjusting torque accordingly... I wonder...

Anyway, it is turning out to be a very interesting exercise indeed, the Baltimore supercharger implementation!

Thanks very much again,
Cheers,
Aleatorylamp

[aleatorylamp]

Hello Ivan,
I´ve tried everything possible, but I can´t get the difference between S.L. speed and altitude speed any larger than about 13 mph, without creating a tremendous Hp difference as well.
The Torque and Friction increase didn´t work either. Nothing works. What I want to avoid is having 1620 Hp at Sea-Level and 1780 Hp at altitude. Why does it need such a huge discrepàncy with reality? A simulatioin is supposed to simulate something that´s real, and this isn´t. It´s uncanny - it seems that the air or its oxygen content in CFS1 is completely different.
Cheers,
Aleatorylamp

[Blood_Hawk23]

Hey Guys,

Question; Are you able to adjust the drag?

If you can adjust the parasitic drag or fuselage drag in anyway then you might be able to gain the extra that you need.

Something else to look at if you are able is the Prop.

I'm not sure what you can and can't do in CFS1 but thats what I've got. If you need the prop specs let me know. I can work on one for you.

[aleatorylamp]

Hello Blood Hawk!

Thanks for the suggestion. Yes, it´s possible to gain a little by playing with the induced drag as opposed to the Zero Lift Drag - from what I gather, this one reduces with altitude so it gives a greater difference higher up. I´ll have to try that.

I suppose you mean to reduce the pitch. The prop pitch angles are adjustable in CFS1 but it´s so complicated that I´ve only had a go at fixed props, not CV ones. A scalar parameter to manage all angles at once would of course be of great use, but I think scalars were introduced later into .air files.

However, there´s a flight dynamics Editor called AAM that shows all the graph curves for the prop blade angles, so one could change the pitch angle of each curve, moving a weaker curve to a stronger angle, I suppose. I´ll have to look into that.

Cheers,
Aleatorylamp

[Blood_Hawk23]

I'll pm you my email. send me a copy of the airfile and I'll run the numbers. I'll need as much of the engine and prop data as you can get. From there I can get rather close. I've done this on some of my WWI airfiles and had great results.

[Ivan]

Hello Blood Hawk.

Welcome to the show.
I would also be interested in your propeller tuning process.
I have a couple projects stuck for lack of a proper propeller.
I believe I have a workable method, but the tuning is all manual at this point
It is mainly Table 512 that causes all the difficulty.

Hello Aleatorylamp.

Please check back on Post #58.
I believe you already had a pretty good result back then that only needed some minor tweaking.
The Sea Level Speed just needed to be up by a couple MPH and the Critical Altitude speed needed to be down a couple.
Both were easy things to tune.

More Later.
Gotta Run.
- Ivan.

[aleatorylamp]

Hello Bloodhawk,
Out of curiosity, what exactly would it be that needs to be done on the propeller tables? Is it that it has to be generally more feathered, or more efficient? As the problem I have is altitude-related, I suppose that the propeller gives too much power in the thinner air hhigh up, or alternatively, too little in thicker air lower down.

Hello Ivan,
Re. my post 58: The problem with the results here is the very low Hp at Sea-Level and the rather high Hp at 12000 ft, which is what I´m trying to avoid, because I can´t imagine that the numbers should be so way out on this simulation. It must be possible to get it better... but of course I may be completely wrong.

What I´m trying to get is a maximum WEP power of 1700 hp at 2600 RPM, both at Sea Level and at 12000 ft,
but the Sea-Level speed would be 291 mph with 44 Mpsi and the 12000 ft one,320 mph with 41 Mpsi.

For the moment the best I´ve been able to get is:
Sea-Level, 1678 Hp with 309.5 mph and 44 Mpsi, and at
12000 ft, 1700 Hp, 320 mph and 40.9 Mpsi

If I set it for 1700 Hp at Sea Level with 291 mph, then it increases to 1721 Hp at 12000 ft, which wouldn´t be too bad, but then it won´t get above 303 mph. To do so, it needs 44 Mpsi, and Hp soots up to 1863 Hp, but maybe this power difference can´t be helped...

Well, we´ll see.
Cheers,
Aleatorylamp

[Ivan]

Hello Aleatorylamp,

Part of the problem is that your goals are not really correct in my opinion.
Here is a slightly larger version of the relevant table from Page 112.
The important things to note here are:
1. The Red Circle marks the single piece of data I believe is incorrect on this table.
2. You are trying for 320 MPH at 12,000 feet while the data shows 320 MPH at 15,000 feet.

The maximum speed is achieved quite a bit above the engine's critical altitude.
One doesn't know the Ram effect on this aeroplane and how it might affect things.

Here are a few interpretations using my pidgin Polish based on my mediocre German and phonetic translation of Polish to Russian. Use at your own risk!!!!

Footnotes:
* Turret Boulton-Paul Mk.III
** Turret Martin 250 CE
*** Speed maximum at level of sea 284 MPH

Note that the Mk.I and Mk.II show 308 MPH at 13,000 feet
Note that the Mk.III loses 6 MPH presumably because of the Boulton-Paul turret.
Unfortunately we do not know the altitude.
Note that the Mk.IIIA is only 3 MPH down with the change to the Martin turret.
Note that the Mk.IV shows basically the same speed with the same power.
Note that the Mk.V shows 320 MPH but at a much higher 15,000 feet instead of 11,500 feet.

Note that your testing will be at 500 feet instead of Sea Level.
Figure the difference is worth perhaps 5 MPH, and of course your mechanics are the best there are, so if you get 295 MPH to 300 MPH, it should be about right.
Figure that the actual Sea Level speed of a Mk.V is only about 288-290 MPH by my guess.

BTW, All of my numbers are "Educated Guesses".
If you have actual reliable test data use it instead.

- Ivan.

[aleatorylamp]

Hello Ivan,

Thanks for your preoccupation, I definitely appreciate that.
Not to worry, my "Sea-Level" testing is at always 500 ft, ever since I ran into a hill with the Zeppelin Staaken Riesenflugzeug RVI back then!

The problem with the 15000 ft max. speed is that setting it at 320 mph there, with the lower Manifold Pressure there, the power surge just before critical altitude is even greater, and things just get out of hand. It was just an "educated" fiddling... But anyway, I´ll keep on trying.

You also have a point about the Boulton-Paul Turret of course, and this would set S.L. Speed a little lower to what we decided a couple of days ago. OK. I´ll note that as well.

I´ve just tried something out along these lines (WEP):
15000 ft: 44 Mpsi, 1917 hp and 316.6 mph
12000 ft: 44 Mpsi, 1870 hp and 312.6 mph
Sea-Level: 44 Mpsi, 1701 Hp and 289 mph

Trying to squeeze out another 3.4 mph at 15000 ft would mean increasing Sea-level speed to just over 292 mph. Not a piece of cake, this exercise!

Trying to set altitude speeds with 41 Mpsi for 12000 ft (1724 Hp) as per the Specification Chart only gives 307 mph, and leaves only 36.4 at 15000 ft (1546 Hp), with 304 mph, although the Hp readings are really very good!
Incidentally, lowering the critical altitude from 13500 to 12500 ft makes no difference.

You mentioned feathering the propeller a bit a week ago, I believe. Would this be manually done, something like reducing the 15º and also perhaps 20º column and moving all the others one or two columns to the right (or is it to the left?) on both propeller tables?
Let me see if my reasoning is correct: At altitude the propeller needs a greater pitch-angle than at Sea Level because the air is thinner, so the J values in the columns have to be increased, but if I´m trying to reduce the power surge there, I have to reduce the values corresponding to certain pitch settings, but which ones? The 15-20º ones or rather the 40-50º ones?.

Cheers,
Aleatorylamp