Why can't I achieve more than 258 kts airspeed?

[LeCuvier]

I have set up a mission for basic A-A gun training, where I pursue a bunch of C-130 Hercules transport aircraft. I cannot catch up to them, in fact they outrun me. With throttle full and propeller at 2700 RPM, my max airspeed in F-10 view is displayed as 258 kts why the C-130 show 338 kts. (level flight at about 6,000 ft altitude).
What am I missing?

[Saxman]

250kts Indicated or True?

[LeCuvier]

2 hours ago, Saxman said:

250kts Indicated or True?

It's the speed I see indicated in the cockpit. The value indicated in the F10 view is about the same-

[felixx75]

41 minutes ago, LeCuvier said:

It's the speed I see indicated in the cockpit. The value indicated in the F10 view is about the same-

https://en.wikipedia.org/wiki/Airspeed

[DrDetroit]

57 minutes ago, LeCuvier said:

It's the speed I see indicated in the cockpit. The value indicated in the F10 view is about the same-

That’s indicated air speed (IAS), not kts or mph. 250 IAS is more like 310mph. 

[cw4ogden]

7 hours ago, LeCuvier said:

I have set up a mission for basic A-A gun training, where I pursue a bunch of C-130 Hercules transport aircraft. I cannot catch up to them, in fact they outrun me. With throttle full and propeller at 2700 RPM, my max airspeed in F-10 view is displayed as 258 kts why the C-130 show 338 kts. (level flight at about 6,000 ft altitude).
What am I missing?

The correct answer is it's currently not clear why the flight model is doing some things regarding airspeed / engine management.  There are a number of theories, one of which is that everything is fine, and "you just don't understand the principles of true airspeed", or, the other flavor of the same argument "you need to convert Knots to MPH" etc.  

At the very least War Emergency Power is very bugged, needing a mouse input on the prop governor, which is completely un-bindable.  It set's the engine rpm to about 3500, which is inaccurate. 

The lingering question is how accurate is the Flight model?  It feels to me like there is excess drag coming from somewhere.  And the engine modelling is a bit of a hot mess still.  The trim feels off as well.  I don't think the amount of trim adjustment required for minor airspeed changes is accurate.  And either the F4U is off, or every other WW2 DCS module is.  There's no plausible physics or aerodynamic reason I can think of, for the F4U to be so significantly different.

Edited June 30 by cw4ogden

[felixx75]

4 minutes ago, cw4ogden said:

At the very least War Emergency Power is very bugged, needing a mouse input on the prop governor, which is completely un-bindable.  It set's the engine rpm to about 3500, which is inaccurate. 

No it's not. WEP = Mil. Power + Water Injection, wich is implemented. You can reach the listed MP settings. Max. permissible RPM in a dive is 3060. 3500+ RPM is a BUG. You can bind the Prop Lever without any problem. Max setting for the lever is 2700 RPM.

Edited June 30 by felixx75

[cw4ogden]

2 minutes ago, felixx75 said:

No it's not. WEP = Mil. Power + Water Injection, wich is implemented. You can reach the listed MP settings. Max. permissible RPM in a dive is 3060. 3500+ RPM is a BUG. You can bind the Pro Lever without any Problem. Max setting for the lever is 2700 RPM.

Well if you are saying everything is fine with regards to the flight model, as long as you don't use the 3500rpm exploit / bug, I disagree.  

[felixx75]

9 minutes ago, cw4ogden said:

Well if you are saying everything is fine with regards to the flight model, as long as you don't use the 3500rpm exploit / bug, I disagree.  

That's not what I said at all. I've never flown a Corsair, so I can't say whether the flight model itself is correct. What I can say, however, is that everything seems to be ok with the engine, as all the values listed in the corresponding tables are achieved in exactly the same way in the simulation.

At speeds of 3200+ RPM the engine would normally die within seconds. RPMs of 3200+ are simply a BUG.

Edited June 30 by felixx75

[cw4ogden]

12 minutes ago, felixx75 said:

That's not what I said at all. I've never flown a Corsair, so I can't say whether the flight model itself is correct. What I can say, however, is that everything seems to be ok with the engine, as all the values listed in the corresponding tables are achieved in exactly the same way in the simulation.

At speeds of 3200+ RPM the motor would normally die within seconds. RPMs of 3200+ are simply a BUG.

Agree that is a bug, but the OP is asking why he and many others can't achieve performance numbers they should be able to.  And while some may be attributable to a layperson understanding of the concepts, the answer to his question, is we don't know for sure.  There are still too many fixes needed to be in a position to do much beyond speculate.

Edited June 30 by cw4ogden

[Mike Busutil]

15 minutes ago, felixx75 said:

 

You should make that your profile picture. You have posted it about 46 times... 

[felixx75]

7 minutes ago, cw4ogden said:

Agree that is a bug, but the OP is asking why he and many others can't achieve performance numbers they should be able to.  And while some may be attributable to a layperson understanding of the concepts, the answer to his question, is we don't know for sure.  There are still too many fixes need to be in a position to do much beyond speculate.

What you would need is a performance table that lists the achievable speeds for Max. Cont. Power, Mil. Power and WEP at the corresponding altitudes.

[cw4ogden]

5 minutes ago, felixx75 said:

What you would need is a performance table that lists the achievable speeds for Max. Cont. Power, Mil. Power and WEP at the corresponding altitudes.

Which exist, and which I'll be more than happy to test after a patch or two.  It's a great module, don't get me wrong.  But the answer to his question and the answer that will surely send you chomping at the bit to argue more is: we don't know.  Have you done the testing?

[felixx75]

13 minutes ago, cw4ogden said:

Which exist

Do you have a link or a picture? Would be nice and would simplify many discussions.

[Saxman]

44 minutes ago, cw4ogden said:

The correct answer is it's currently not clear why the flight model is doing some things regarding airspeed / engine management.  There are a number of theories, one of which is that everything is fine, and "you just don't understand the principles of true airspeed", or, the other flavor of the same argument "you need to convert Knots to MPH" etc.  

This case is a combination of BOTH:

First, he's reading it in Knots and not MPH. Second, he's reading IAS and not TAS.

258kts IAS is about 300kts TAS at 6000ft, depending on exact conditions. And 300kts is about 345mph, which is right around where the 1D's TAS at 6000ft should be.

@LeCuvier Your Corsair is going EXACTLY how fast it should be at that altitude once you factor in all the conversions.

[hind75]

In a system riddled with bugs, where does the belief come from that the current RPM gauge is accurately displaying engine revolutions?

[felixx75]

Just now, hind75 said:

In a system riddled with bugs, where does the belief come from that the current RPM gauge is accurately displaying engine revolutions?

...because all engine values fit together (apart from the temperatures, which are known to be still wip)

[hind75]

Quote

13 minutes ago, felixx75 said:

...because all engine values fit together (apart from the temperatures, which are known to be still wip)

 

Most sources only provide information about maximum speed, with no mention of acceleration, making it impossible to assess whether it has been accurately programmed. The only thing we can do is make direct comparisons with existing aircraft.

 

 

Edited June 30 by hind75

[felixx75]

6 minutes ago, hind75 said:

Most sources only provide information about maximum speed, with no mention of acceleration, making it impossible to assess whether it has been accurately programmed. The only thing we can do is make direct comparisons with existing aircraft.

 

 

There are tables that show how many MP should be achieved, at which RPM and which blower level and at which altitude. So far, it all fits together.

The only thing the video shows is that by taking advantage of the bug, you can fly faster. And that's no wonder when you look at the absurdly high values (MP/RPM) that can be achieved in this way.

[GTFreeFlyer]

Maybe not the most accurate source of info, but Wikipedia shows cruise speed 215 mph, max speed 446 mph (which could be the do-not-exceed speed in a dive, or maybe the max TAS at altitude, but unclear).

It also says the Corsair reached its highest speed at 19,900 feet.  
 

Just throwing that out there. I’m just a Googler.  Perhaps someone will have better info to share.  

[hind75]

8 minutes ago, felixx75 said:

There are tables that show how many MP should be achieved, at which RPM and which blower level and at which altitude. So far, it all fits together.

The only thing the video shows is that by taking advantage of the bug, you can fly faster. And that's no wonder when you look at the absurdly high values (MP/RPM) that can be achieved in this way.

Then why is it significantly slower even compared to the P-47, which also operates at 2700 RPM?

[GTFreeFlyer]

Also, to add to my comment above, engine shaft power is equal to torque times RPM.
 

 If you flatten the propeller pitch in order to get more RPM, two things happen:

 

 1.  You might reduce the torque, thereby negating any effect (with respect to more power) from increased RPM.  Usually though, not always, the drag buildup on the prop airfoil (causing torque) rises quicker with RPM than the falloff from flattening the pitch.  So usually, torque will increase with RPM, but not always.  Just imagine a scenario where flattening the pitch to zero and you would get no thrust, and some dumb number like 10,000 RPM.  You wouldn’t go anywhere without the thrust, even though you would have lots of torque and RPM.
 

 2.  You take less bite out of the air and less thrust as mentioned above.
 

These could translate to less total power, and slower airspeed.

I also expected the Corsair to be faster, but it’s totally plausible than 200-250 kts is in the correct ballpark in the thick low atmosphere.  

9 minutes ago, hind75 said:

Then why is it significantly slower even compared to the P-47, which also operates at 2700 RPM?

Even Wikipedia specifically calls out that the Corsair was 13 mph slower than the P-47.  Again, you cannot equate RPM to airspeed.  Some RC planes have props that spin 10,000 to 15,000 RPM and they aren’t any faster than the F4U  

[Hayrake YE-ZB]

I would like to hear what a 10,000 rpm R2800 sounds like (before it explodes).

[GTFreeFlyer]

25 minutes ago, Hayrake YE-ZB said:

I would like to hear what a 10,000 rpm R2800 sounds like (before it explodes).

Me too

Quick math for the Corsair prop means the blade tip would be traveling just a tiny bit fast, about 4,600 mph!

Edited June 30 by GTFreeFlyer

[Saxman]

58 minutes ago, GTFreeFlyer said:

max speed 446 mph

That's for the F4U-4, which has a different block engine and a four-bladed paddle prop providing substantially more power.