Hello Ivan,
Itīs nice of you to answer being off the net but using your Ipad with its typing inconvenience. You donīt have to worry if time passes until you can answer more easily from your computer.
Thanks for confirming that the problem is the single-speed CFS1 turbocharger.
Let me see if I can explain a little better how Iīm trying to get around this and what is happening right now:
We are not only moving things around, but also taking out speed peak which was completely out of place, 2100 ft below critical altitude, which was also much higher than the normally expected critical-altitude peak. Another way of interpreting it is that the critical altitude dropped by about 2100 ft because of the very low Boost Gain setting. AirEd info refers to this in a very vague way.
The only way to correct this is by increasing Boost Gain, and to do this without a resulting speed surge above critical altitude, we must reduce Drag. This of course entails reducing speed at 500 ft to aproximately S.L. Speed, and consequently S.L. Speed unavoidably also goes down. Also, mid-altitude speed goes down, but high-altitude Hp and Hg readings are more in line with reality.
Granted, I agree that the useless peak is still there, but without the speed, and also, that with the Drag increase, Iīm moving the whole envelope down. However, then I can increase the excessively low Boost Gain again to recover the desired power at 15000 ft, eliminating the speed surge at 10000 ft. The unwanted peak has the same Hp as before, but speed is slower by aproximately the mph subtracted from the 500 ft speed due to the Drag increase. This way the plane doesnīt shoot off at 326+ Mph, 2100 ft under critical altitude, now obediently staying put at 320 mph, the same speed it has at 15000 ft, before and now. Then, the restly critical altitude peak is as before.
Hereīs a comparison chart. The two side-by-side values in each column are before and after the Drag/Boost Gain increase. (I put Boost Gain up from 2.085 to 2.221).
You will notice that the low Boost Gain had not only lowered critical altitude, but also given poor power levels above that, which is now corrected. Of course speed there has stayed the same, which was mandatory. Speed below critical altitude was exorbitantly high, and correcting this was the objective.
I did some more tests for 8000, 9000 and 11000 ft.
__500 ft: 44.0-44.0 Hg 1700-1700 Hp 296.0-290.0 mph. - Now 6 mph under
_4500 ft: 44.0-44.0 Hg 1754-1755 Hp 309.7-302.8 mph. - Now 7 mph under
_6700 ft: 42.0-42.0 Hg 1696-1695 Hp 313.7-304.8 mph. - Now 9 mph under
_8000 ft: 42.0-42.0 Hg 1715-1714 Hp 320.5-310.5 mph. - Speed surge removed
_9000 ft: 42.0-42.0 Hg 1728-1728 Hp 324.2-316.8 mph. - Speed surge removed
10000 ft: 42.0-42.0 Hg 1742-1742 Hp 326.6-319.9 mph. - Speed surge removed
11000 ft: 40.2-42.0 Hg 1674-1757 Hp 324.9-322.3 mph. - Speed surge reduced
12000 ft: 38.6-41.2 Hg 1612-1735 Hp 323.7-323.7 mph. - Speed same as before
12500 ft: 37.9-40.4 Hg 1586-1703 Hp 323.1-323.5 mph. - Speed effectively same as before
15000 ft: 34.3-36.5 Hg 1447-1555 Hp 319.8-320.0 mph. - Speed effectively same as before
Notice the low previous Manifold Pressure at 11000 ft is lower than it should be, as itīs below critical altitude. Also, if you press the WEP button here, you should get 42.9 Hg, but it was ineffective previously, which also shows how critical altitude was incorrectly low before.
The new criteria for WEP is now Take-off Power only, and not for flying around all the time, so I only did tests with WEP for lower altitudes. Nevertheless, perhaps the new criteria could include a permitted WEP power climb upto 6700 ft? This could also compensate the lower performance.
4500 ft, 44 Hg, 1755 Hp, 302.8 mph - WEP perhaps allowable?
6700 ft, 44 Hg, 1786 Hp, 311.4 mph - WEP perhaps allowable?
Curiously and expectedly, using WEP now at 8000 and 9000 ft gets very close to max. speed, so definitely no WEP there!
8000 ft, 44 Hg, 1805 Hp, 317.6 mph - WEP not allowable.
9000 ft, 44 Hg, 1820 Hp, 319.5 mph - WEP not allowable.
Use of WEP further up, at 10000 or 11000 ft would seriously distort the flight envelope of the plane - albeit not as much as before... co convenient comments in the Readme would perhaps make simmers abstain from using WEP after say 7000 ft. I havenīt tested WEP for 10000 ft or 1000 ft yet.
Anyway, I think all in all itīs much better. Of course, now itīs a little slower lower down, but 326 mph at 10000 ft was terrible! ...unless of course it wasnīt... (!!), and the critical altitude was all wrong!
I know you perhaps donīt like the lower S.L. performance, but maybe this is the lesser of evils.
Anyway, we are trying to curb the shortcomings of CFS1 īs single-speed blower, so we could interpret the use of WEP here as a manually implemented extra boost, only to be used below 7000 ft.
If we permit it for take-off and prohibit it later, we might as well include it upto 7000 ft to compensate for the lower power at lower altitudes. Iīd say itīs a valid argument, whouldnīt you agree?
Cheers,
Aleatorylamp
Last edited by aleatorylamp; June 2nd, 2016 at 00:40.
Hello Ivan,
Sorry about the long post.
I was trying to argument things as best as possible, and it just kept getting longer! The idea of course isnīt perfect and has its flaws.
On the MkIIIA itīs not working - Boost Gain here is lower still, with a shorter speed-span, and everything just gets worse.
Iīll perhaps try the balanced increase in torque and friction graphs, to see what happens higher up.
Cheers,
Aleatorylamp
I was just testing your Mitchell-C .air file to see what you mentioning about the peaks.
From the speed information you quoted in one of your previous post, I deduce your testing protocol for speeds as being perhaps 80% fuel and no bombs, or perhaps 50% bombs and 50% fuel.
I see the your point. It doesnīt look like the peaks are too bad, which would mean that the peaks in my case wouldnīt be so bad either! If I could only somehow correct the erroneous peak 2000 ft below critical altitude, it would be perfect.
The performance curve on the Mitchell-C does look very good!
As the Baltimore is lighter and wing area smaller, the change in dimensions and weight required Drag and Boost Gain adjustments that have originated the current problem.
Iīm working on it, to try to avoid sacrificing in the S-L. performance.
Hello Ivan,
At least the increased Boost Gain has eliminated the "false peak" below critical altitude, and following on from the possibly acceptable peak criteria, I lowered Drag a bit to push up the whole envelope a bit. This got me an extra 3 mph at 500 ft., and is at 292.8 mph now, still 3.2 below the desired 296, but nonetheless slightly better.
I couldnīt push it up any further, as the altitude peak, previously already at 323.7 mph, has now increased by another 4.3 mph.The shape of the pčak starts at 9000 ft with 320 mph, progresses up to 328 at 12000 ft, and dwindles slowly down to 324 at 15000 ft again.
So, for the Mk.V, we have a possibly acceptable speed envelope:
- 8 mph faster at peak,
- 4 mph faster at specified max. speed 15000 ft
- 3 mph slower at 500 ft
Then, for the MkIIIA, it still wonīt work! Any Boost Gain increase to kill the "bad peak" makes altitude performance shoot up so much that it canīt be compensated with a Drag increase. As soon as I find a balanced way to eliminate the peak, Iīll post some numbers. ...but not as extensively as last time, ha ha!
Should you have any suggestions or ideas, I would be glad to hear them. Possibly you may have mentioned something before, which I have missed. Thanks very much in advance!
Take your time - thereīs no hurry at all for an answer!
Update:
By the way, I had already tried to compensate the 2100 ft loss in critical altitude due to the low Boost Gain by raising Critical Altitude to 15000 ft (overcompensating just to be safe), but it had absolutely no effect.
Cheers,
Aleatorylamp
Last edited by aleatorylamp; June 3rd, 2016 at 15:04.
I am back home again tonight but will be heading out again tomorrow morning.
The shape of the power curve (and thus the performance curve) for a CFS supercharger is going to be the same shape in all cases as I understand it.
I see no way of getting around it.
There will be a low at Sea Level at a particular MP level.
There will be a critical altitude at which the same MP is achieved as at sea level. (This is the engine's critical altitude.)
There will be a peak about 2/3 (somewhere around 2/3 from my vague interpretation) of the distance between Sea Level and Critical.
The fitting of the curve to best match the performance of your project is up to you.
In the first case, your peak was below the aeroplane's 15,000 feet critical altitude (Aeroplane's not Engine's critical altitude).
In the second case, your critical altitude was higher but the SL power started lower, so the peak was closer to where you wanted it.
The choice of 6 mph faster at medium altitudes or 6 mph slower at SL is entirely up to you.
Pick the one that appeals to you the most.
As for WEP, I believe the WEP Boost Modifier set to Zero makes the most sense, but again, it really is up to you.
The big problem is that this simulation of "Through the Gate" really doesn't make much sense when compared to reality.
On a real aeroplane, running Through the Gate at Sea Level will stress the engine.
Running Through the Gate above Critical Altitude makes much less difference and above a certain altitude makes no difference whatsoever.
Thank you for your helpful comments and your long answer!
So at the moment, that seems to be the state of the situation.
Interesting, and it will obviously require a decision as to what approach will be more appealing.
Thanks for the clarification about the 2 different critical altitudes - one for the engine and one for the plane... I get the gist, but it seems rather odd. Then, ceiling is yet another different thing...
Meanwhile, back at the workshop, there is some mysterious new activity going on:
Record 505: Parameter "Supercharger Low Altitude" Related?
-AirEd info:
>Usually 1.0000 if Turbocharged
>Large values (~100000) Inc MP/HP at SL
I looked into this in my current Baltimore Mk.V experiment, where:
- normal max. MP= 42
- WEP increase = 44
- Boost Gain = 2.221
and found that the following WEP and non-WEP MP readings came up at S.L. and/or 500 ft for the following different Supercharger Low Altitude increase entries, and have listed their corresponding MP readings:
Original setting and MP values:
_____1: 42.0 and 44.0
Testing new settings for their MP values: (all at S.L. or 500 ft, first non-WEP and then WEP))
__2500: 42.2 and 44.1
__5000: 42.3 and 44.3
_10000: 42.6 and 44.4
_20000: 43.3 and 45.1
_30000: 43.8 and 45.7
_33000: 44.0 and 46.0 This +2 Hg setting could be of use? Perhaps a cunning plan...
_40000: 44.4 and 46.4
100000: 48.1 and 50.1
First of all, 3 comments:
1) It seems that if throttle is at 99% instead of 100%, all values will default to 48.1 and 50.1 !!
2) The altitude at which only 0.1 Hg WEP/non-WEP difference happens, was 10000 ft. With Boost Gain at 2.27 like on the Mitchell-C, this difference occured was 10500 ft.
3) At and after critical altitude, also for the second Boost Gain setting, MP readings matched those obtained prior to any changes in the Supercharger Low Altitude increase parameter. Now Iīm waiting for my mechanics and engineers to build some modifications into the supercharger, to see if and how this effect can be of any use. At the moment, there is a huge argument going on.
The idea is to try to use a 33000 setting and reduce Normal Manifold pressure from 42 to 40, so that with WEP for Take-off, they will get the required 44 Hg, but later, without WEP of course after mid-altitude (we continue to prohibit WEP for normal flying higher up), expectedly the pre-critical altitude peak will be 2.0 Hg lower!!! Now some of the staff are still shouting, but a few have just scuttled off to the drawing board, lathes and planes, to quickly build something before the place gets burnt down!
At least they are happier with the new plan than with the previous Drag trials... Letīs see what happens!
Another thing have just asked, is how about an Emergency Power Pressure Change Rate MINUS value instead of Zero?. Would that vary with altitude? I told them we can only try one thing at a time. That will have to come later.
Letīs see about the Low Altitude Supercharger effect first.
Cheers,
Aleatorylamp
Last edited by aleatorylamp; June 3rd, 2016 at 23:45.
Reason: typos
It is hardly a nice day out. I am trying to take care of my mom and she does not have computers or Internet access at her house.
She is barely mobile at this point, so life is not so easy. Not to mention that she tends to constantly ramble about a lot of odd things, but the rambling is pretty much the way she has been for decades.
She is pretty old but still coherent so that part isn't so bad.
I have my laptop computer, but no Internet unless I set up my cell phone as a wireless hotspot.
Problem there is that the communications speed would be VERY slow. It probably is not quite enough for easy browsing.
I tried it in the car a few months ago when we were doing a college visit for my daughter.
I know of the parameter you are describing but have never experimented with it.
I have always wondered if this was a "Supercharger as versus Turbocharger" setting.
If you are getting increasing MP values with altitude, I cannot see how this is beneficial or even useful.
What you are really trying to tune is the Engine Output because the MP settings that stay constant with increasing altitude are not THAT much of a problem.
You asked about my speed testing protocol.
I actually start with 100% Fuel and Zero Bomb Load and do not worry as I burn off Fuel during the test.
Weight does not seem to matter very much when testing speed, but matters a lot more when testing climb rates.
When differentiating between different models of the Baltimore, keep in mind what the differences were in reality.
I ran into this problem also with my P-38 Lightning:
The claim is that the WEP speed of the J Lightning is supposed to be around 445 MPH.
The F Lightning is slower at maximum speed but actually has less drag than the J because with the same power settings and very similar engine output at cruise settings, it is faster.
The problem is that with the SAME drag in the AIR file, the F is way too fast.
This tells me that the actual WEP speed of the J is probably not quite as fast as the reports claim because the numbers simply do not add up.
The alternative ideas simply do not add up very well.
Whenever we build an entire series of aeroplanes, we run into this problem where the test reports do not match exactly with the physics that we know MUST be true and sometimes with the aeroplanes' reputations.
I hit this with the P-40 series as well and that is why the flight testing with the P-40N is so strange.
Need to go find a few things before I leave the house for the day.
- Ivan.
Hello Ivan,
Thanks for your detailed reply!
What you say about different models of a plane is definitely the case!
This whole supercharger business is not only getting very interesting but also very exciting!
The truth is, that I only want to increase Power at low altitude, to recover S.L. speed, and then, try to get the altitude peak down!
So the Low Altitude Supercharger increase parameter is just what we need.
Boost Gain is now even lower than it was before, and this helps mid-altitude speed, and also, it will not warrant WEP after Take-Off! So we must prohibit that because using it will give more than specified maximum power as of 5000 ft!!
My workers have all run into town to party with their family or girlfriends to celebrate. They are all criticizing the test pilot because did the tests with full tanks and half the bomb load, but they decided to let him off...Here are the results of the test-flights:
__500 ft 44.0 Hg 1700 Hp 296.7 mph >>>> WEP only here. Take-off, and a little while after...
_4500 ft 42.0 Hg 1666 Hp 305.2 mph
_6700 ft 42.0 Hg 1696 Hp 315.1 mph
_8000 ft 42.0 Hg 1714 Hp 322.6 mph
_9000 ft 42.0 Hg 1728 Hp 324.4 mph
10000 ft 41.5 Hg 1718 Hp 326.8 mph
11000 ft 39.8 Hg 1655 Hp 325.8 mph
12000 ft 38.3 Hg 1598 Hp 324.8 mph
12500 ft 37.5 Hg 1568 Hp 323.8 mph
15000 ft 34.0 Hg 1431 Hp 320.1 mph
I think this is quite a lot better than before!
Now my own family is angrily calling me to lunch.
Back later!
Update:
Well, lunch was wonderful. My wife being in the middle of her 2-year cookery course at a technical high-school downtown has its advantages...
Looking after old people is hard. At least your Momīs mind hasnīt gone like my motherīs did. We were lucky enough to get a place for her in a social-security old-peopleīs home specialized in caring for cases of senile dementia in her last few years. I remember when my 2 brothers came to the Island to visit for a week each, one after the other, she recognized them, but the day after they were gone sheīd forgotten the visit. However, I suppose thereīs an emotional memory that somehow works when the conscious one doesnīt. Then she broke her hip at 85 and the unavoidable operation was too tough for her. Anyway, such is life. Everyone agrees, old age is only good if you are reasonably mobile and lucid...
I donīt know much about cell-phones because mine doesnīt even have a camera or a touch-screen, and I wouldnīt know how to use one which did... Iīm sure they are useful... but I need my reading glasses for the phone, so it puts me off.
Anyway, you can try the "new" parameter on the Mitchell-C - maybe you can iron out the high altitude peak after critical altitude.
What I still want to figure out is how to compensate the other peak about 2/3 before critical altitude, although in this case, it helped with getting S.L. and mid-altitude speeds back in place.
I wonder what approach the MkIIIA will require - this has a speed envelope very similar to that of the Mitchell-C, but itīs more difficult because very similar speeds need to be achieved with slightly weaker engines, but with a considerably lighter and smaller airframe and just over half the payload. Iīll see.
Cheers,
Aleatorylamp
Last edited by aleatorylamp; June 4th, 2016 at 08:00.
Using my Cellular Phone as a Mobile Hotspot definitely works because that is how I am online at the moment.
You don't have to follow MY testing protocol.
If you want to do testing under different conditions, that is fine as long as you are consistent.
One thing we have not discussed is how long to wait for the maximum speed to become stable.
I generally record the value if it has not increased in 15-20 seconds.
If you wait longer in your tests, your speed reading may be 2-3 MPH higher.
Which value are you actually changing now for the supercharger?
I don't happen to have AirEd on my laptop but if you tell me what the Record:Offset value is, I can look it up in my copy of FDECtrl.txt which I do have here.
I am guessing it is Record 505 Offset 64 as a Double Precision Floating Point.
I am not so sure I agree with your results though.
From what you have listed, it seems like your current results are quite a bit worse than what you were getting before.
Your engine's critical altitude is only at 9000 feet.
You are getting your target airspeed at 500 feet but you need WEP engaged to do it. It wasn't needed before.
Your Manifold Pressure is way low at 12,000 feet.
You reached target airspeed at 15,000 feet, but the power and speed before that are quite high.
Hello Ivan,
Glad your Mobile Hotspot is in operation. Modern technology at work indeed! As yet, out of my abilities...
I also did Mk.IIIA trials with 100% fuel and 50% payload, for the sake of consistency. From what you said it seems OK for the purpose. Itīs about 1000 lb heavier than with no payload + 100% fuel, which we will use once climb tests start.
I forgot to thank you for helpful suggestion on the 15-20 seconds for speeds to settle during test flights. I have adopted this method too and it makes life simpler, but usually a final check is 30 seconds just to make sure it stays put.
In AirEd.ini, in record 505, it is:
11=40,double,*Supercharger Low Altitude Boost Related ?
11h=Usually 1.0000 if Turbocharged|Large values (~100000) Inc MP/HP at SL
In FDE it is Unknown 505 - 64, so it is the one you say. Default is 1.
This value wonīt affect critical altitute. In fact I thought it would help correct it, but it doesnīt.
The one that lowers critical altitude is the Boost Gain, which unfortunately has to be low so as to keep high altitude speeds (11000-15000 ft) from shooting up beyond spec. speed.
I donīt understand your present comment that I now need WEP for 500 ft and didnīt before.
I thought that we were aiming precisely at 44 Hg for Take-off, as well as for 500 ft with 296-297 mph, for which we need WEP. Otherwise we only get 42 MP.
Was that not precisely the point we needed - to have WEP only for Take-off? It would not be used to for the rest of the flight envelope you were describing so as to protect the engine, and that would be non-WEP at 42 Hg until it went down.
So I understood something quite different from what you meant.
There is already so much power in the engines with 42 MP that it wouldnīt really need the 44 Hg WEP for take-off anyway... or anywhere else, for that matter, but OK... So, in a nutshell, do you mean that the 296-297 mph at 500 ft should happen under 42 MP?
This will probably unfortunately distort the envelope even more, because Drag will have to go down further, to get S.L. speed without WEP up to what it is now with WEP. Reducing Drag always creates havoc at higher altitudes. Boost Gain will have to go down even further, so critical altitude will drop even lower. It is really set for 12100 ft, but CFS only respects it if Boost Gain is more or less at or above 2.25 - otherwise it either ignores it or multiplies it down.
My manifold pressure is way down low at 12000 ft. Yes, it is, and I have mentioned several times before, that it was a real the problem: With higher MP values there was excessive power, and speeds rise to beyond 330 mph. Curing this with Drag caused very low S.L. power and speeds, so it was a big problem.
Power and speed at 15000 ft are OK but before that, quite high. Yes they are, but I canīt find a way to iron that out. You had mentioned in your last post that the 2/3 altitude peak is impossible to eliminate, so I really donīt know what you mean. If I could find a way to iron that peak out or put it up a bit without messing other things up, Iīd do it. I did say that I was still working on it. I thought you said it was a problem inherent in CFS.
Without lowering Boost Gain and without using the Low Altitude Boost increase, we get a different type of flight performance envelope that is has problems elsewhere, which I have mentioned several times before.
Anyway, I finally did manage to get the Mk.IIIA .air file going in a similar way to the last Mk.V one.
However, from your comments I gather that you wonīt really like this one either, but here goes:
Aims:
288-289 mph at 500 ft (284 mph specified for S.L.)
305 mph at 11500 ft
100% fuel and 50% bombs and 50% ammo trial
__500 ft 44.0 Hg 1660 Hp 288.0 mph >>>>WEP only here.
_4500 ft 42.0 Hg 1626 Hp 296.0 mph
_6700 ft 42.0 Hg 1656 Hp 303.5 mph
_8000 ft 42.0 Hg 1674 Hp 308.4 mph
_9000 ft 40.9 Hg 1637 Hp 308.6 mph
10000 ft 39.3 Hg 1576 Hp 307.0 mph
11000 ft 37.7 Hg 1517 Hp 305.7 mph
11500 ft 37.0 Hg 1492 Hp 305.1 mph >>>> Mk.IIIA Spec. speed
12500 ft 35.4 Hg 1435 Hp 303.3 mph
15000 ft 32.2 Hg 1306 Hp 299.6 mph
With the even lower Boost Gain required here to keep speed from shooting up at altitude, critical altitude for the engine is also very low - 8000-9000 ft!
Well, so much for that. Letīs see if it will be possible to adjust both .air files to get the 500 ft speeds happening with 42 Hg MP instead of 44. So WEP boost is meant to be independant from all this... Hmmm...
As you saw by the SEFC for the Vultee Vengeance, even for the same model engine, there is quite a lot of flexibility.
Your opinion is as good as mine in this case considering that neither of us has found a SEFC for the Baltimore yet.
I have my own tuning preferences. Yours do not have to be the same.
I also have my own testing protocols (which are in a state of change for climb testing).
Again, yours do not have to be the same.
At the moment, you are playing with a parameter that I have never experimented with, so I am not in a position to give advice especially since I have no access to a simulator to even experiment to see if I can understand what is happening.
I knew what my goals were in my testing for the Mitchell and achieved the majority of them.
I have no idea anymore what your goals are with the various Baltimores.
Hello Ivan,
Thanks for your post. Yes, I agree with you on the flexibility and the goals.
The testing protocols are easy to change and I can really use whichever are more convenient - they wonīt change the shape of the curve anyway. 1000 lb lower weight is just 1 point lower on the Zero Lift Drag in AirEd. Iīd just forgotten to empty half the tanks and was half way through the test before I noticed, so I just went on, also for the 2nd model, especially after your comment. So like you say, that really doesnīt matter. Next time Iīll subtract it from the .air file and that will prevent me from forgetting!
What does matter, is that the graph shape just doesnīt seem to want to come out right, even using some of the more obscure parameters that at first sight seemed to have been beckoning towards a solution.
How would one arrive at the best solution with single-speed blowers instead of two-speed ones?
Whatīs more important, the speed of the plane in the sim or its MP or Hp readings?
You said a while back that you were more inclined towards getting closer to the performance rather than the numbers, so that means Mph, and not Hp or Hg so much, and then, performance along as many parts of the curve as possible, not only at the beginning and at the end.
I thought that my goals were clear, even despite the non-existence of a SEFC for the Baltimore, but anyway, here they are again:
MkV: S.L.: 291-292 mph, 296-297 mph at 500 ft, 320 mph at 15000 ft, with a higher peak just at 12500 ft.
MkIIIA: S.L.: 284 mph, 288-289 mph at 500 ft, 305 mph at 11500 ft, with a higher peak just after.
PLUS: As few aberrations as possible along the rest of the line!
The fact that suddenly a 2nd Baltimore has come up is because I thought the performance curve on that one would be easier to achieve given its shorter speed-span, but in fact itīs even more out than the first one. So, I can forget about it and try to get the first one right.
Had the Mk.IIIA been easier I would have discarded the Mk.V.
Problems?
A) I didnīt understand the 44 MP Take-Off WEP thing you had in mind and put that into the 296-297 mph instead of leaving it separated from the curve. Solution? Try out further.
B) Boost Gain has lowered critical altitude and CFS ignores the parameter specifying it. Solution? I dunno! This is the condicio sine qua non. For the smaller wings, lighter airframe but similar engines this doesnīt seem to be coming through as nicely as on the Mitchell-B/C.
C) High speed Manifold pressure is to low, but has ALWAYS been too low. Solution? Not important for my goals, but MP must be correct at S.L. and until correct critical altitude which it is.
Conclusion:
The Baltimore is conditioned to the possibility of my being able to move the engine peak onto the other side of the correct critical altitude, in other words, my possibility of correcting the stupid position that the simulator incomprehensibly forces critical altitude into after providing the seemingly obvious solution of lowering Boost Gain for performance adjustments after Take-off. Like George Orwell said in 1984: "Two plus two is four. Once that is granted, all else follows".
Not to worry, and not to hurry! As they say here, "There are more days and more pots", so Iīll continue tinkering around until you get the chance to try out this "unused" parameter and see what you can say about it.
Update:
Maybe all these musings are useless beatings around the bush, a pile of codswallop, as the English say (best not to explain what it really means!), because most probably, what is in reality going on but nowhere to be found, is that the R-2600-29 has a critical altitude of 15000 ft, with WEP Hp rating of 1850 Hp, and a normal 1700 HP rating at 12500 ft! Iīm quite certain that putting this into the .air file will work. Actually, it will be the only thing that works!
There being two editions of the -29 engine may mean that the 1850 Hp version had the 1850 Hp at 15000 ft in the normal max. rating, and was just a nomenclature change, not a real change, so it was the same, identical engine.
Bets anyone?
Then perhaps, the Mk.IIIA .air file not working for a completely different reason, being that I have not actually tested it yet using the normal approach without all the extra (for this case useless and even pernicious) new parameter experiments.
Cheers,
Aleatorylamp
Last edited by aleatorylamp; June 5th, 2016 at 02:06.
Hello Ivan,
Following on from my last message, to make sure how the normal approach would work on the MkIIIA beforeperhaps erroneously discarding it, I did a very precise test.
Aims were:
1) 500 ft: 288-289 mph with 42 Hg.
Experiment result: 1574 Hp at 288.8 mph - Fine!
2) 500 ft WEP at 44 Hg: 1660 Hp.
Result: 1660 Hp at 305 Hp. Hp is PERFECT!
Is a 15 mph increase over non-WEP fine? WEP MP increase is at 2, and Emergency Pressure Change Rate is at zero.
3a) Max speed 305 mph at 11500 ft, WEP making no difference.
Result with Boost Gain 2.27: 42 Hg, 1724 Hp, 330.1 mph. Hg/Hp good, Mph TERRIBLE!!
Result with Boosh Gain 1.85: 35 Hg, 1400 Hp, 304.7 mph. Hg/Hp low, Mph VERY GOOD!
Adjusting Boost Gain more finely, Iīm sure exactly 305 mph can be reached, but thereīs no point.
3b) Critical altitude is 11500 ft, i.e. peak performance is here.
Result with Boost Gain setting 2.27: Peak at 13500 ft. TERRIBLE!
Speed continues to rise to 331 mph at 13500 ft, and at 15000 ft it is still at 329 mph. Thereīs no point in investigating where it goes.
Result with Boost Gain setting 1.85: Peak at 7000 ft. TERRIBLE!
Exactly at 5528 ft, 305 mph max speed is reached too soon, and later, speed comes down to 305 mph again at 11500 ft, which should be critical altitude, after which it continues going down.
Obviously a Boost Gain setting that fits the required 11500 ft altitude does exist, and may be at around 2.2 or so, but it will also have a very high speed peak, so itīs not even worth trying out.
Comments:
Wahtever I do, the curve shape is very distorted. Obviously this, like you said, is the CFS single-speed supercharger at work.
Iīm terribly sorry, this wonīt do at all. Unless there is a way to get this reasonably bent into shape using whatever criteria may be useful or reasonably effective, which I donīt have, I can forget about this version again.
It seems we are going around in circles. I think you are looking for a "Magic Bullet" and I doubt you will find it.
CFS is what it is and although it was a great improvement over FS98, it also has its limitations.
You brought up a lot of points. I will try to address a few.
Priorities are Performance, Manifold Pressure, Horsepower in that order.
There are a few cute little ways to do fine tuning but I don't want to bring those up because on this project they are almost certainly not necessary.
On something like the FW 190D that I used for my tutorial, I believe they would be unavoidable.
Don't worry if you are 3-5 MPH off.
The parameters in the simulator are not that granular and sometimes that is as close as you will get.
The fine tuning such as with Propeller Tables can help, but I do not recommend you go there.
Changing multiple parameters at a time is unwise.
For the SEFC we got from the B-25C/D, we can gather the following:
Take-Off Power is around 1700 HP at 44.0 inches Hg and 2600 RPM.
There is a small rise in power above Sea Level so that 1700 HP is reached again with only 42.0 inches Hg.
The 12,000 feet power rating is PAST its critical altitude because only 41.0 inches Hg can be reached.
Perhaps I am wrong and it is a limitation of the High Speed Supercharger gear, but I am treating it as beyond critical altitude.
The Aeroplane reaches a high speed of 315 MPH at 15,000 feet but this is way above critical altitude which is not uncommon.
For your Mk.III Baltimore, if it is hitting maximum speed at 11,500 feet, its engines' critical altitude is quite a bit lower.
(Otherwise it would go even faster if you went higher.)
From the SEFC of the B-25C/D, it appears to me as a reasonably educated guess that those engines had a critical altitude in High Blower of around 11,500 feet, so an earlier version with less supercharger would probably be below that.
(This probably is like saying the typical Basketball player is PROBABLY taller than I am.)
I have data limits on cell phone, so that's it for now.
Hello Ivan,
Thank you for making me un-dizzy again, I must say! ...with the added merit of your message coming out of the the miniaturized Iphone technique which Iīm useless at.
Iīm glad that at least I tried to look through the tangles in the quagmire and decipher something, because I have learnt a bit about what some of the more obscure and unused (and probably useless) parameters can and canīt do, and what they really should do and donīt do!!
So whereīs the magic bullet? It just crossed my mind that until someone else wrote decent CFS .air files for the Baltimores, I could provide simpler FS98 ones to do the trick for the time being! (Honestly no sarcasm meant). This way I could chicken out and just build...
However, Iīd be missing out on how interesting it will be to see if, or rather how, eventually something usable DOES come out of a CFS .airfile for the planes. So, lead on, Mac Duff, the journey has yet to improve!
Hello again, Ivan, I was fearing that I was getting heavy with this business and that you were going to get fed up, so I am quite glad and relieved to have the sensation that this is not the case. After your reassuring comments on the Mk.V and Mk.IIIAīs different engines, I have just made some small adjustments and conducted another precise flight test on the Mk.IIIA.
___16 ft 44.0 Hg 1663 Hp 283.7 mph __500 ft 44.0 Hg 1669 Hp 284.1 mph >>>> Mk.IIIA 284 mph S.L. Spec. Speed very good _4500 ft 42.0 Hg 1635 Hp 293.1 mph _6700 ft 42.0 Hg 1665 Hp 299.8 mph _8000 ft 42.0 Hg 1663 Hp 304.2 mph _9000 ft 41.8 Hg 1690 Hp 308.2 mph >>>> peak better here than before at 7000 ft. 10000 ft 40.2 Hg 1627 Hp 307.1 mph 11500 ft 37.8 Hg 1533 Hp 305.0 mph >>>> Mk.IIIA Spec. Speed exact. 12500 ft 36.4 Hg 1483 Hp 304.0 mph 13500 ft 34.9 Hg 1426 Hp 299.8 mph
Evidently the difference between S.L. and 500 ft is not as much as Iīd expected when I extrapolated data from what we had agreed on for the Mk.Vīs 296-298 mph at 500 ft.
This has allowed an increase in Zero Lift Drag to get S.L. speed correct. I still donīt understand your comment on the low S.L. performance i.e. WEP or non-WEP for 500 ft, so I went for the specification S.L. 284 mph and tested over the water at a hair-raising 16 ft.
I got exactly what I needed, or think I needed, and discovered that speed increase for this aircraft from S.L. to 500 ft is actually only 0.4 mph. This makes 42 Hg tests here, in my view, irrelevant, unless of course Iīm completely wrong, which canīt altogether be discarded!
This has also allowed an increase in Boost Gain to 2.0, thereby fortunately raising the CFS imposed critical altitude to 9000 ft, much better than the previous 7000 ft.
Performance at 11500 ft matches 305 mph specification speed as before, which is still a great satisfaction, but a greater one is that speed peaks below and above 11500 ft critical altitude have disappeared!
Can it be said that this is as good as it can get? If not yet, then Iīm sure it can be improved, judging by your comments. If so, we have the pleasing situation whereby the Mk.IIIA is back on the drawing board and will resume AF99 production.
The next step will in any case be to see about the Mk.Vīs chances of achieving the same.
Thanks again, Ivan, for your steadfast and encouraging help! Cheers Aleatorylamp
Last edited by aleatorylamp; June 5th, 2016 at 14:37.
Your Baltimore Mk.IIIA performance actually looks pretty good.
I don't believe you will significantly improve on the performance curve you currently have.
Here is an interesting thing for you to consider:
Your Sea Level speed run is ENTIRELY INVALID! <Grin> Unless you tested at Death Valley or some place below Sea Level.
Perhaps they go faster because swimming with the fishes scares them??? Naaah.
Here is why: Ground Effect.
Hubbabubba and I touched on a somewhat related subject a few years ago.
In Ground Effect, The reduction in Induced Drag changes the speed significantly.
No one actually tests at Sea Level. They test at a convenient altitude and use a mathematical correction to get equivalent Sea Level performance.
Another invalid test (The part Hubbabubba and I were discussing) is to go from a higher speed DOWN to the maximum speed.
It doesn't seem logical, but is how things really work.
During the wary, Bombers would climb a bit and then go down to sea level in a shallow dive.
When they reached as low as they dared, they would be in ground effect for long over-water flights AND
the speed would stabilize a couple MPH above where they would have been had they accelerated UP to that speed from below.
Whether it makes sense or not, this is what really happened.
Time to cook dinner.
My family just finished visiting at my mom's house about an hour ago.
I was just doing a daredevil 16 ft test on the Mk.V to establish the basis for correct 500 ft performance.
It seems to have clarified WEP use and speeds for S.L. and/or 500 ft performance somehow, although the actual numbers for 16 ft height were not going to be respected by anyone!
Would 288 mph for 500 ft then have been indeed closer to the truth? It would however not have helped towards the correction of critical altitude. Anyway, thanks to this the performance envelope is pleasing!
So testing downwards can be misleading. I had that feeling, so when I do test going downwards, I let out the landing gear and pull it in again to slow down to a point where speed has to rise for that altitude. This way itīs quicker too, but itīs convenient to eliminate Landing Gear Pitch Moment for the test...
So bombers saved fuel in ground effect! Flying boats did as well. So itīs the Induced Drag that decreases. I always wondered why the dynamic air cushion under the wings could make Drag decrease.
Like the ekranoplan Caspian Sea Monster! I wonder if anyone would want a "Korabl Maket" KM4 for CFS1. Probably not... Extraordinary 500-ton Leviathans from 1964 as big as a 747 doing 500 mph at 40 ft above the water.
A breathtaking sight, these incredible machines. Take-off using 10 Turbojets, 8 of them just behind the cockpit, which had cups that could blow the jetstream downwards to increase ground effect under its short but wide wings. Once airborne, they cruised in Ground Effect on just the two tail engines below the tall T-Tail, with stabilizers necessarily above Ground Effect. The front ones were sometimes left idling to be able to use them quickly enough to "jump" over suddenly appearing obstacles.
The .air file has a stronger Ground Effect Graph 400, and a severe cut in peak of the Wing Lift Coefficient vs. AoA Graph 404 to prevent it from flying above ground effect. Flap control tandems flaperons with jetstream angle for Take-off. Wierd but effective.
Anyway, hereīs a picture of my FS98 Caspian Sea Monster meanwhile!
Cheers,
Aleatorylamp
Last edited by aleatorylamp; June 5th, 2016 at 15:58.
Reason: wording
Check Record 400 for Ground Effect Graph.
The increase in CL will let the wing lift more at a lower angle of attack but drag is matched with angle of attack
so because of the reduced AoA, the induced drag is less.
Regarding lower SL speeds:
Remember that the engine power output curve does not really match a two speed supercharger power curve.
It peaks where in reality it should be pretty low.
I figure the best approach is to best match the two curves so it doesn't deviate too far at any one point.
It will then be too low at SL too high at middle altitudes and perhaps too low again at critical altitude.
Because of the ram effect and because of where people typically test for speeds, I will not reduce the critical altitude speed much if at all.
If you think your graph matches badly, look at the one for the FW 190D that is in my tutorial.
If there is a better way to do things in CFS, I don't know it.
Just think about it though:
In the history of CFS, developers generally have not cared much for duplicating actual performance or perhaps most folks really did not have any idea how to do it.
The fact that we spend a little effort along these lines and are getting fair results is a vast improvement.
Pity we can't meet for a long lunch or dinner discussion.
Typing responses is a bit slow.
Hello Ivan,
Interesting, yes... and also, when coming down during test flying instead of going up, because of the lower angle of attack and the downward descending movement there might be an increased cushion of air underwing, causing what we could call a "Coming-down Effect" i.e. a pseudo Ground Effect.
A lunch would be great, wouldnīt it? Spring rolls, fried Wan Tun, and fried rice for me please. The last time my wife and I ordered this, here in a Chinese Restaurant, the Owner almost didnīt serve us, arguing unpleasantly that none of these were main courses, and only served us what we wanted because otherwise we would have left. Sweet and sour prawns (done in Tamarind sauce) would have been a good main course, but we werenīt so hungry that day.
My current experiments with the Mk.V seem, surprisingly and unexpectedly for me (but Iīm sure not for you), to be going rather well. The lower S.L. performance resulting from my hair-raising 16ft test flying appears to be working!! ...sheer luck! Results resemble your current curve description:
- Slightly low at S.L. (exactly like the Mk.IIIA),
- Speed peak Critical Altitude at 10000 ft (this must go up to 11500 ft as yet by correcting Boost Gain).
- 317 instead of 320 mph at proper 15000 ft critical altitude. (this will go up to 320 if I correct Boost Gain).
(Update: Neither of them did...)
Interesting, how well this is finally going - and without either strange speculations or using other misleading and obscure parameters! I suppose I was a bit hard on our CFS, and I do thank my lucky stars that it still works in this day and age, and what it does is quite remarkable for what it is!
Time for breakfast and getting the kids to class. My wife is off to a practical cookery exam - the third in 7 days.
Update:
The kids donīt have to go to class, theyīre studying for exams.
Iīd forgotent that... My memory resembles a 2nd. hand EDO module.
So, here are the new results of the Mk.V flight test, and the shape of the curve is exactly as you said!
("Of course", you will say, ha ha!)
Increasing 15000 ft speed to spec. 320 would come at the price of an extra 3 mph at the 10000 ft peak. Now speed is nicely acceptable, so it may stay there. In after-thoughts predictably, I havenīt managed to move the peak to 11500 either...
100% fuel and 0% bombs
___16 ft 44.0 Hg 1694 Hp 292.9 mph >>>> This one just for fun now, but also helps to get my bearings.
__500 ft 44.0 Hg 1700 Hp 293.5 mph >>>> Predictably slightly low (should be 296-298 mph)
_4500 ft 42.0 Hg 1666 Hp 300.6 mph
_6700 ft 42.0 Hg 1696 Hp 308.9 mph
_8000 ft 42.0 Hg 1714 Hp 316.4 mph
_9000 ft 42.0 Hg 1728 Hp 321.2 mph
10000 ft 41.7 Hg 1729 Hp 323.2 mph >>>> Peak still here, but weaker.
11000 ft 41.0 Hg 1670 Hp 322.0 mph
11500 ft 39.3 Hg 1639 Hp 321.4 mph
12000 ft 38.5 Hg 1609 Hp 320.8 mph >>>> Critical altitude set at 12100 ft (but ignored?)
12500 ft 37.7 Hg 1579 Hp 320.7 mph
15000 ft 34.2 Hg 1431 Hp 318.0 mph >>>> Should be 320 mph. Probably I should go for it and raise Boost Gain ever so slightly once more. It would then possibly be 326 mph at 10000 ft. From what you say in your last post, I gather that itīs just what you would do in your case.
... but itīs looking nice!
Thanks again for your summed-up indications! Now we can have 2 Baltimores! ...at least...
What blows my mind is how you knew that this was what the curve was going to more-or-less look like if done correctly... Flabbergasting!
Cheers,
Aleatorylamp
Last edited by aleatorylamp; June 6th, 2016 at 00:28.
Actually there is nothing that is really "Flabbergasting" about the end result.
For the most part, tuning the CFS engine is pretty predictable.
You actually were at this point a couple months ago when I first sent you my MitchellC AIR file and you modified it.
The differences between where you were then and now are pretty minor.
Keep in mind though that you have worked on flight models of this type a couple times,
but I have done this several hundred times.
It doesn't mean I know everything because I do not. There are things I have been meaning to experiment on such as the Propeller Tables.
I should be home this evening and if I am not too tired, I will try a couple things out.
First task is conduct a proper Service Ceiling Test for the B-25B/C Mitchell.
My current protocol is closer to an Absolute Ceiling Test.
I shudder to think of how the results and change of protocol will affect other projects.
I know for sure the Mitchell's flight model will change to some extent.
Recommend you increase Supercharger Boost Gain slightly because not only will it increase your speed at critical altitude, it will also bring the Manifold Pressure up a touch. Perhaps you will still not get to 41.0 inches Manifold Pressure but you will be closer.
Also as a side note, there is a "Critical Altitude" parameter in Record 505, but I don't think it actually does anything.
On my P-40N and others I have worked on, changing that number doesn't seem to affect anything.
Also, the actual critical altitude on my P-40N is around 12,100 feet but the parameter is set for 12,500 feet so the two don't really match though they are close.
Hopefully you are now getting a good "Feel" for how changing parameters affects engine power.
If you think back on all the things we have covered since you first started posting here, there is almost nothing regarding tuning AIR files that I know how to do that has not been discussed at one point or another.
Hello Ivan,
On the way home on the tram (itīs impossible to park downtown so I donīt drive to work) I thought back on how similar the present .air file was to the one you have just referred to.
Back then, the 326.5 mph at 10000 ft seemed awful to me because I didnīt know much about supercharging in CFS, and stubbornly kept on trying out all sorts of different things to see if I could get it any better. Now it turns out that this new one is very similar, and "only" perhaps a bit better after my topsy-turvy investigation. However, it has been a very fruitful experience, as you also say, because now I understand much more about what is actually going on!
What I have learnt about engines in all this time since the beginning, represents a huge improvement for my FS FD building, and my knowledge about the development of aircraft engines since the early times, a subject that has always been one of my favourites. So thanks a lot for your patience in repeating things when I didnīt quite get them until I did!!
Next will come the building itself, and then some testing along the lines you are at present working on.
So, thereīs interesting material on the horizon!
Later today Iīll post the new test resuts after slightly pushing up Boost Gain. I wonder if the "false ceiling" will also crawl up ever so slightly...!!
I have one more class this afternoon and then Iīll be free again.
Cheers,
Aleatorylamp
Hello Ivan,
Here are the Baltimore Mk.V new slightly-pushed-up-Boost-Gain Flight Test results,
with a little something interesting added below... Humm humm, what could that be now?
...but first the results:
187 Baltimore Mk.V Trial No. 7
Friction: 32.6
Torque: .535
Oswald: 6750
Zero Lift Drag: 68
Boost Gain: 2.125 This is the value for exactly 320.0 mph specified speed at 15000 ft.
Supercharger Low Altitude Boost increase: 1.0
100% fuel and 0% bombs
___16 ft 44.0 Hg 1694 Hp 293.2 mph
__500 ft 44.0 Hg 1700 Hp 293.3 mph >>>> (now 0.2 mph lower still),
_4500 ft 42.0 Hg 1666 Hp 300.7 mph
_6700 ft 42.0 Hg 1696 Hp 309.5 mph
_8000 ft 42.0 Hg 1714 Hp 316.7 mph
_9000 ft 42.0 Hg 1728 Hp 320.9 mph
10000 ft 42.0 Hg 1743 Hp 323.4 mph
10500 ft 41.8 Hg 1742 Hp 324.7 mph >>>> peak has moved 500 ft up! AND to 41.8 Hg!
11000 ft 41.0 Hg 1710 Hp 324.4 mph
11500 ft 40.2 Hg 1683 Hp 323.5 mph
12000 ft 39.4 Hg 1652 Hp 323.4 mph
12500 ft 38.6 Hg 1621 Hp 323.4 mph
15000 ft 35.0 Hg 1479 Hp 320.0 mph >>>> exactly as per spec.
Now for the little new something:
If we enter -15000 (minus fifteen thousand) into the Supercharger Low Altitude Boost increase parameter
- yes, negative values are indeed allowed - then we get the following:
___16 ft 43.1 Hg 1653 Hp (WEP)
__500 ft 41.1 Hg 1574 Hp (WEP)
_4500 ft 41.1 Hg 1626 Hp
_6700 ft 41.1 Hg 1655 Hp
_8000 ft 41.1 Hg 1673 Hp
_9000 ft 41.1 Hg 1686 Hp
10000 ft 41.1 Hg 1701 Hp
10500 ft 41.1 Hg 1708 Hp
Entering -16500 would have given exactly 1.0 Hg less, but my maths was wrong, (typical!) because entering -33000 you get 2.0 Hg less. (Mpsi = Manifold Pressure per Square Inch perhaps, of mercury being implied)
And from the Peak upwards, i.e. the critical altitude which for this plane seems to be 11.000 ft, the Manifold Pressure and Horsepower values remain unchanged.
So! Can this be true? Is this really our Low Blower Speed here, for low altitudes?
I knew it had to be somewhere, but the question is, can we use it?
Oh yes! Probably... But with what values?
Of course, perhaps there are different planes that have a High Speed Blower for low altitudes, for which then positive numbers in this parameter are obviously intended. But do High Speed Blowers for Low Altitudes really exist? I wouldnīt know. If not, the intention behind this parameter has been misinterpreted in the info file.
This could well be used to limit power on the throttle gated Gotha Grossflugzeuge and Staaken Riesenflugzeuge, setting Boost Gain so that critical altitude were only at 4000 and 7500 ft, below which full throttle was not allowed.
Hereīs a picture of the toy Baltimore racing along at 16 ft above sea level just for fun. Itīs made of wooden blocks and blue cardboard, with transparent gelatine canopy, turret and cabin, all very primitively shaped, just to get the feel of the looks and the stance. Terrible, you would say, but at least the props turn!
Possible Baltimore Mk.V low altitude Booster correction
Hello Ivan, My mechanics and engineers have been doing their homework, or rather their work-shop work, tinkering with the pressure regulating mechanism on the blower, so that below critical altitude, the blower RPM go down to deliver less MP than before, and if WEP is engaged, the RPM increase is higher than before, so the MP delivery for WEP is the same as before. Then, at critical altitude, the blower automatically reverts to its normal state, which doesnīt change with WEP.
What they donīt know exactly yet, is how much the MP reduction should be below critical altitude, and they eye-balled and said "OK, letīs go down 1 Hg and see if it works.", though Iīm sure your engineers will know more exactly what it should be for the Baltimore Mk.V.
Anyway, previously we had at S.L.: non-WEP: 42 Hg. WEP: 44 Settings: 1-Manifold Pressure: 42 2-Supercharger Low Altitude Boost related: 0 3-Emergency Power Change Rate: 0 4-Emergency Power Manifold Pressure Increase (inches): 2
Now, below 11000 ft critical altitude, for the case of a 1 Hg MP reduction below critical altitude: non-WEP: 41 Hg. WEP: 44 New Settings: 1- Manifold Pressure: 42 (same as before) 2- Supercharger Low Altitude Boost related: -16500. (This will reduce normal MP by 1 Hg below critical altitude). 3- Emergency Power Change Rate: 0. (This remains unchanged. Using this for WEP here to compensate the 1 Hg reduction for seems not to work, at least not at S.L.). 4- Emergency Power Manifold Pressure Increase (inches): 3. (This compensates the reduction of 1 Hg normal MP, so that we get the full 44 Hg MP with WEP at S.L.).
This seems to work very well, and the Beckwith Testing Gauge gives the readings! A rough climbing test gives 5 minutes to 10000 ft, but I havenīt got a stop watch and will have to check better. One of the Specs I have says 4.8 min. to 10000 ft
Here are 2 pictures of a single-stage and a 2-stage supercharger, just out of curiosity.
The single stage one looks like a simple one without modifications for 2 speeds. Would they connect an altitude sensor to a slip-clutch mechanism? Maybe it was manual, and not automatic in reality, or perhaps even a turbocharger that would be altitude-regulated acting on the waste gate, but I donīt know if they existed at the time. Interesting anyway... The parameter in the .air files seems to cater for both.
Cheers, Aeatorylamp.
Last edited by aleatorylamp; June 7th, 2016 at 01:49.
Firstly: OOooppsss!
My post #173 has a mistake in the 500 ft line with the lower manifold pressure values.
In the second line power corresponds to a non-WEP setting. Sorry!
With WEP, MP would be 43.1 as well, and Hp would be almost the same as for S.L.
Later, I conducted another test with the reduction value for 1 Hg (-16500), WEP power at 500 ft delivered 1700 Hp. exactly and was almost the same at S.L.
Anyway, the subject of this post now:
Practically and mathematically, the "possible Boost correction" with a -16500 (-1 Hg) reduction entry is possible, but as I said, only an approximation. It gives a Normal Max. MP of 41 Hg below Critical altitude.
I have the sensation that it is bit insufficient to achieve correct RoC, but engine power is too much for Ceiling, so evidently, a ceiling adjustment will be mandatory first. You had already mentioned the need for a ceiling test several times in the last few weeks, and I can anticipate your answer to my question yesterday, which could probably be "The correct reduction setting will depend on what RoC you want to achieve with engine performance corrected for ceiling."
OK, then. Donīt hurry for an answer, take your time, as Iīm sure you are conducting your own tests.
Thereīs no hurry in the hobby - it wouldnīt be a hobby if there were any hurry!
Cheers,
Aleatorylamp
Last edited by aleatorylamp; June 7th, 2016 at 22:23.
Reason: Ooops!
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