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How to tell ATA/boost without techno chat.

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Posted (edited)
On 5/25/2020 at 4:58 PM, Raven109 said:

 

I think we're in agreement here. Yes, RPM matters as well, and the game does model this. I was just giving an example where reducing ATA, but keeping RPM constant increases the in-game timer. The reason I chose ATA is because MAP starts dropping above FTH, so you can still have max admissible RPM at lower ATA, which in theory should allow you to run your engine for a bit longer than when running at max ATA and max RPM. Of course the time will not be as long as when running at a lower RPM. One more reason why I chose ATA is because IRL reducing RPM before MAP can lead to a catastrophic failure (not sure if this applies to the 109 as well,  although I suspect it does).

 

It is interesting to see that even though some pilots claim to have been running the 109 by looking at the ATA gauge, there are pictures showing 109 dashboards where the max allowable time limits were added to the RPM gauge, which indicates, that at least some pilots had a preference for RPM. There were some pics, but I can't find them now.

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Here is one (note the 3' limit marking next to the 2700 RPM marking):

lDwaof.jpg.e67db52365ad6f9461399495a259737b.jpg

 

IRL it probably makes sense to watch the RPM gauge more than ATA. This is because you want to be conservative. High RPM still stresses the engine, even though your ATA is lower. Maybe this is one of the reasons why later 109 models have the RPM gauge moved higher up, and the ATA lower, but I don't have any sources to confirm this.

 

In-game all you care about is to maximize performance (so what if you have to ditch in the wild Kuban forests?), so then considering ATA makes sense.

 

I don't understand the preference on ATA instead of RPM. ATA depends on altitude, environment temp and pressure and air speed. RPM is always the same for the throttle setting. So RPM is the obvious choice.

 

Considering only ATA above FTH and ignoring the RPM limit is simply a gamble. You will have a unspecified time limit for that engine setting, so engine can die after 1 min, 2 min, 3 min ... you will only find out when it's to late. 

Using higher RPM than allowed above FTH may not be critical at first, but a slight dive might bring you close to FTH, the increasing speed raises ATA even more ... and suddenly you fly at the 1 min limit for RPM and ATA without noticing it.

 

The german boost control might consider this and automatically increase ATA above FTH, I don't know.

 

I know that Merlin boost control does that not, it only keeps the same boost for a throttle setting below FTH. So you have to increase throttle to compensate for the boost drop above FTH. And so I need to decrease it when descending. 

Edited by 41Sqn_Skipper

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Posted (edited)
53 minutes ago, 41Sqn_Skipper said:

 

I don't understand the fixation on ATA instead of RPM. ATA depends on altitude, environment temp and pressure and air speed. RPM is always the same for the throttle setting. So RPM is the obvious choice.

 

Considering only ATA above FTH and ignoring the RPM limit is simply a gamble. You will have a unspecified time limit for that engine setting, so engine can die after 1 min, 2 min, 3 min ... you will only find out when it's to late. 

Using higher RPM than allowed above FTH may not be critical at first, but a slight dive might bring you close to FTH, the increasing speed raises ATA even more ... and suddenly you fly at the 1 min limit for RPM and ATA without noticing it.

 

The german boost control might consider this and automatically increase ATA above FTH, I don't know.

 

I know that Merlin boost control does that not, it only keeps the same boost for a throttle setting below FTH. So you have to increase throttle to compensate for the boost drop above FTH. And so I need to decrease it when descending. 

 

Do you mean my fixation? If you go through the whole thread, you can see that I don't have a preference for either, I even go and talk about pros and cons for each, and post images which might indicate that pilots had preference for one or the other, or both. I think ATA/RPM, at least for the in-game 109, become a concern when you're constantly firewalling the throttle. Which should not be that often (emergencies only?); so most of the time, i.e when flying at the so called combat power setting (named so for a good reason), these two go hand in hand, and you can use either.

 

For example Eric Brunotte is talking about using ATA, almost never RPM (12:11 minute mark):

 

9 hours ago, [=PzG=]-FlyinPinkPanther said:

 

 

Yeah, I took a G4 up last night. The change was instantaneous. I went up to 5000 meters and the same thing. 

 

This is slightly on or off topic. I was looking at the throttle. 

Looking at it there are deisgnations

Zu, P1, P2, and M2. 

Between Zu and P1 are three colors. Red, "Gold" and White. 

 

The Gold appears to be the power needed to taxi. The top starts the plane moving. 

P2. Is Combat 

Between P1 and P2 you have Nominal power. 

I do not know what the 'white" and the P1 is supposed to represent other than "idle power." It doesn't seem right. The ATA 0.6 and below 2000 RPM. 

 

 

 

The Zu, P1, P2, P1+P2 are the positions for the fuel pump selector, which is the lever right next to the throttle lever. You can't directly control it in-game. I never knew what the coloured lines on the left side of the throttle quadrant mean. Some IRL pics show 109s that have them, some don't, there doesn't seem to be a pattern.

Edited by Raven109
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Posted (edited)
24 minutes ago, Raven109 said:

 

Do you mean my fixation? If you go through the whole thread, you can see that I don't have a preference for either, I even go and talk about pros and cons for each, and post images which might indicate that pilots had preference for one or the other, or both. I think ATA/RPM, at least for the in-game 109, become a concern when you're constantly firewalling the throttle. Which should not be that often (emergencies only?).

 

Sorry didn't meant to be rude and changed it to "preference". I understood that you prefer to fly by ATA and ignore RPM (and intentionally exceed the RPM limit above FTH). Which I strongly disagree with, as a general guideline for pilots. As long as the pilot is aware of the dangers of that method it's of course fine.

Edited by 41Sqn_Skipper

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Posted (edited)
50 minutes ago, 41Sqn_Skipper said:

 

Sorry didn't meant to be rude and changed it to "preference"

 

That's fine, no worries. I didn't see it as being rude. I was more confused about the way my posts were understood. Since I also play Il2 CoD from time to time, I'm also inclined to look more at the RPM gauge, since the 109E1/3s there don't have automatic prop pitch control and you need to do it by yourself. After some time and several over revved engines, which resulted in premature ditches, you get the hang of it and start using engine sound.

50 minutes ago, 41Sqn_Skipper said:

I understood that you prefer to fly by ATA and ignore RPM (and intentionally exceed the RPM limit above FTH). Which I strongly disagree with, as a general guideline for pilots. As long as the pilot is aware of the dangers of that method it's of course fine.

 

I was trying to say that it is possible to do all this (use ATA as a guide to go over the 1 minute time limit above FTH). It's definitely not something that new players might want to do, since it's at the edge of the envelope for that plane. I do think that experts (or daredevils) might gain some more performance (or at least the comfort of an increased timer), at the increased risk of blowing your engine up if you misjudge it, of course.

 

New pilots can always take the plane and test it until they are comfortable with it.

 

But, all these are corner-cases. If you want to go back to base in one piece, you should not fly at the edge of the envelope, this means that getting into situations where your max ATA/RPM decides life and death should not be the rule, but rather the exception. If the rule is to get back in one piece, then whether you use ATA or RPM rarely maters.

Edited by Raven109

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Posted (edited)

Interestingly increasing the RPM above the allowed limit will also increase the the available manifold pressure, so when simply looking at the performance it certainly is an beneficial approach.

 

But as you say it rarely matters, we are not talking about maximum performance situations, but rather "cruise" or "economic" power settings. Having a slightly lower boost than "optimal" is not crucial in this case, and in my opinion doesn't justify to increase the chance of engine damage.

Edited by 41Sqn_Skipper

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