Mach number in-game vs Tacview

[diditopgun]

Hi !

 

Starting with a clean (no belly pylons) Tomcat, 50% fuel at 38000ft Mach 1.2 and then noted top speed just before running out of fuel:

 

QNH 29.92;+15°C @SL; FL380; 1340 KTAS (external view); Tomcat airspeed indicator: Mach 2.25 ---> Tacview: Mach 2.35

 

QNH 29.92; -10°C @SL; FL380; 1370 KTAS (external view); Tomcat airspeed indicator: Mach 2.27 ---> Tacview: Mach 2.39

 

So with Tacview I can finaly reach that Tomcat top speed of Mach 2.35 in ISA.

 

How can you explain this Mach number delta between in-game cockpit instrument and Tacview measurement ? :huh:

[Emmy]

Your instruments are affected by temp and pressure. I do not believe TacView takes this into account.

[diditopgun]

That's why I use ISA parameters QNH 29.92 and temperature 15°C at sea level with no wind. I presume Tacview is based on it ?

[Nealius]

Your instruments are affected by temp and pressure. I do not believe TacView takes this into account.

 

Now that's interesting. If that's the case then Tacview isn't quite the valuable tool everyone makes it out to be.

[Eagle7907]

I’ve also noticed the mileage may be off as well. I did Phoenix shots at set distances, they were off in the Tacview by 8-9 miles.

 

 

Sent from my iPhone using Tapatalk Pro

[IronMike]

Tacview is a tactical analytics tool, most and foremost, if you are off by mach .2 in most a2a situations (or high G a2g maneuvering), this will not make any difference from the learning experience. In trainings 29,92 with 15°C is used best to match it anyway. but think of it: could .2 save you from a missile sometimes? sure why not. are you however training for this particular situation? unlikely. tacview lets you rather discover the gaps in your SA, I think it is still very valuable for that.

[diditopgun]

I didn't do it about air combat performance.

I just want to know if you have simulate something particular in your airspeed indicator (like some errors of any kind) or if it could be a bug or something else.

Tomcat max speed is given for Mach >2.3, but in-game I never achieve such speed in level flight.

But with the speed of 1340 KTAS Tacview and airspeed convertors around internet give me speeds of Mach 2.3xxx.

So I just want to understand what could be wrong or not.

[Cruiser18]

I think of it in the way that Tacview shows the truth, because it does not care about the error factors that cockpit instruments are exposed to (damage, misalignment, air pressure, temperatures, inherent inprecision etc).

 

Basically, your cockpit instruments give you their best guess at how fast you are going. Tacview has access to the "truth" and show you how fast you were actually going.

[lunaticfringe]

Tacview interpolates its presentation between data points collected anywhere from ten times a second, to once every second or so, depending on the situation. The polling rate used to be higher, but the data collection appears to have been lessened as the back end techniques have developed. It can actually work at even less polling numbers (every few seconds), but that's not the case here.

 

That said, because the polling is relatively infrequent, specific orientation and performance can be off. Its one thing to take three specific points in three dimensions and calculate the overall speed over time and applied G between pairs of points, and be accurate with the numbers. Its wholly another to be absolute in precision with such limited information, and it's not- you can see it from time to time with severe rolling events when the engine "guesses" you went the opposite direction, making the aircraft look like a pinwheel because you invoked a snap roll.

 

But that's not what Tacview needs to be useful. ACM is about trends over time composed of distance and angular relationships, not absolute precision found between them.

[Yeti42]

Shoot me down if this is @#$%%^% but I'm presuming Tacview uses True airspeed (TAS) and not indicated airspeed (IAS) or it could use groundspeed (GS) you/we could try some calculations to find out what's simulated...

[Bogey Jammer]

I noticed similar issues with the MiG-21 module. The best guess is that the data collected for Tacview comes from a different pipeline than the cockpit instruments which have their own measurements algorithms.