45 minutes ago, blingthinger said:

 

So, the user sets a throttle position, the sim calculates what %N1 they're requesting, simulates spool lag to get there, and scales the thrust per mach/alt along the way.

Maybe we can turn this thread about the F14 top speed into some useful suggestions for XP improvements. 🙂

The issue, as it is now, is that turbojet engines in XP are able to continue working at higher EAS/Mach than their RL counterparts, without melting or blowing up. That is the reason for excessive speeds of jet aircraft at low altitude in XP.

So, just as one can specify max structural speeds (Vne, etc.) in Plane-Maker, Austin would also need to add a couple of limit parameters for jet engines as well. I'm thinking max EAS and max inlet temperature. So that the virtual turbojets would fail just like the real ones if attempting Mach 2.0 at sea level.

30 minutes ago, Murmur said:

The issue, as it is now, is that turbojet engines in XP are able to continue working at higher EAS/Mach than their RL counterparts, without melting or blowing up.

*part of the issue...I proved myself partially wrong just now by being able to super cruise (rc3). 😮 These ain't F119's! The turbine maps do need some tweaking.

XP's FADEC doesn't have compressor inlet temp as a target. That would definitely fall under custom job / future improvement.

38 minutes ago, Murmur said:

add a couple of limit parameters for jet engines

I was looking, its not that simple... because the F14 has

http://www.anft.net/f-14/f14-detail-airintake.htm

which afaict is not modelled, either visually or in terms of the engine behaviour.

 

 

7 hours ago, mSparks said:

hence 80% incorrect. because 850KIAS is in virtually no way the determinant of top speed in mach

But we can absolutely rule out any speeds in excess of M2.0 at sea level with a 850kts Vne. Which was the actual conditions we discussed. High mach number / low altitudes

And which my statement addressed, given that LSS is 660 TAS at sea level (ISA conditions). 

These are facts, not some random numbers I pulled out off a hat. 

It's rather interesting that you openly admits the supersonic/ fast jet flight regime is a topic you "don't have a clue about" (your words, not mine), but that doesn't stop you from vehemently arguing with others (who in this case have formal education in the matter). Just an observation, it's a peculiar trait you exhibit.

Edited December 15, 20223 yr by SAS443

3 minutes ago, SAS443 said:

we can absolutely rule out any speeds in excess of M2.0 at sea level with a 850kts Vne.

Why?

Vne - as in the point things like the airframe actually fail - is in true airspeed (aiui, could be wrong, but that hasn't been discussed), and we know it can go in excess of 850kts TAS or it couldn't go Mach 2.0 at 30,000 feet either.

That is why you switch to Mach/MMo, because if you, for example, try to go 400kts IAS in a 747 at FL350 everyone is going home in a coffin (cos you'll be doing 645KTAS/mach 1.1).

1 hour ago, SAS443 said:

But we can absolutely rule out any speeds in excess of M2.0 at sea level with a 850kts Vne. Which was the actual conditions we discussed. High mach number / low altitudes

And which my statement addressed, given that LSS is 660 TAS at sea level (ISA conditions). 

These are facts, not some random numbers I pulled out off a hat. 

It's rather interesting that you openly admits the supersonic/ fast jet flight regime is a topic you "don't have a clue about" (your words, not mine), but that doesn't stop you from vehemently arguing with others (who in this case have formal education in the matter). Just an observation, it's a peculiar trait you exhibit.

I appreciate your persistence, but you're trying to talk to someone who very clearly doesn't even understand what true airspeed is. 

Edited December 15, 20223 yr by 2reds2whites

13 minutes ago, 2reds2whites said:

His rambling about TAS is laughable.

Its a question, you can't have it both ways, if you can't exceed 850kts TAS, you can't exceed mach 1.4 at 30,000 feet.

I'd guess, the failure (not saying there isn't - asking what it is) is that at lower altitudes and higher speeds you end up with supersonic flow into the engine and it cuts out/breaks.

but the airframe itself is more than capable of handling >850kts TAS because no one seems to disagree that it can do Mach 2.0+ at 30,000 feet.

But thank you for your valuable contribution to the conversation, its truly noteworthy the level of intelligence you have brought to it.

13 minutes ago, 2reds2whites said:

Worth giving up I think.

No one believes you had anything to contribute in the first place.

Edited December 15, 20223 yr by mSparks

11 hours ago, mSparks said:

Vne - as in the point things like the airframe actually fail - is in true airspeed (aiui, could be wrong, but that hasn't been discussed)

No V_ne  is a pressure speed, expressed in Knots CAS (IAS corrected for any pressure and/or position errors) in the diagram I posted.

TAS and GS are the only actual speeds in aviation....the rest ( IAS, CAS, EAS) is a pressure.

 

50 minutes ago, SAS443 said:

No V_ne  is a pressure speed, expressed in Knots CAS (IAS corrected for any pressure and/or position errors) in the diagram I posted.

TAS and GS are the only actual speeds in aviation....the rest ( IAS, CAS, EAS) is a pressure.

 

So you disagree with:

https://www.australianflying.com.au/news/vne-and-flutter-explained

Quote

So to recap, IAS is the limiting factor for structural stress, but TAS warns us that we are approaching a speed where flutter is likely to start.

And Murmur's graph that the engines give up at 750kts EAS?

22 hours ago, Murmur said:

 

 

35 minutes ago, mSparks said:

So you disagree with:

https://www.australianflying.com.au/news/vne-and-flutter-explained

I agree with the diagram I posted. Which measures speeds in Knots Calibrated. 

If you disagree, email [email protected] and attach the link that you just googled.

I wish best of luck on your endeavors.

1 hour ago, SAS443 said:

I agree with the diagram I posted.

this one, with a 500kt CAS limit in it? (bottom graph, mach 1.8 at FL410):

Or the one above it with a 550kt CAS limit in it? (mach 2.0 at FL480):

On 12/14/2022 at 1:02 PM, SAS443 said:

 

Whats your estimate for Vne for structural failure in IAS then? Still 850kts?

or

500kts, 550kts Something else?

Maybe the 800kts XP12 uses perhaps, good for most of the range on the top graph - although the engines fail at 750kts IAS for most of that.....

 

Edited December 15, 20223 yr by mSparks

6 hours ago, mSparks said:

Whats your estimate for Vne for structural failure in IAS then? Still 850kts

Actual data for an F14 carrying 8 missiles and 50% fuel load going full AFB at 15.000ft ISA conditions. 
Track design limit speed downwards and you'll cross TMN line at 1.75 and KIAS at around 870:ish. And design limit speed is higher than a V_ne /V_mo

Again contact their support if you are not content. I'm not an expert in military airplanes at all  (although I have logged flight time in one , while performing aerobatics) 

 

20 minutes ago, SAS443 said:

at 15.000ft ISA conditions. 

 

20 minutes ago, SAS443 said:

KIAS at around 870:ish

Try that in Xplane with remove flight surfaces enabled 🤣

Edited December 15, 20223 yr by mSparks

1 hour ago, mSparks said:

Try that in Xplane with remove flight surfaces enabled 🤣

Tweet them and say that you have found inaccuracies in their official performance data sheets for the F14  Tomcat, which can be proven by a 60 USD desktop simulator, if you feel that  there are errors at play here.

https://twitter.com/northropgrumman

Have a fantastic day. 

1 hour ago, SAS443 said:

Tweet them and say that you have found inaccuracies in their official performance data sheets for the F14  Tomcat, which can be proven by a 60 USD desktop simulator, if you feel that  there are errors at play here.

https://twitter.com/northropgrumman

You are mistaken, i said the whole time imma gonna keep doing mach 2 at 200 feet in VR.

you insisted it was 850kts

then insisted that was in cas

then posted a chart showing the airframe can fail at 500KCAS, but you still want to go 850kts CAS and think the sim is wrong when it rips your flight control surfaces off.

Edited December 15, 20223 yr by mSparks