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If you want 2 circle in a F-16, stay above 10000 feet.


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4 minutes ago, oldtimesake said:

 

That is incorrect. 372 knots is around mach 0.56 but not accurately mach 0.56. You are in a sensitive region where small change in turn rate results in much higher change in  ps. 

372knots is 191.4m/s, 7.5G normal load factor results in 7.43G centripedal acceleration, which is 72.84 m / s^2. Turn rate = 72.84/191.4 = 0.3805rad = 21.8deg/sec. From the manual chart at 21.8deg/sec the ps should not significantly exceed 100 ft/sec.

 

Ah, thank you for the correction. I figured there would be additional fuzz here from the speed of sound converting to IAS and some other stuff in there I really don't understand.  So instead of me picking the point based on 7.7 G and 0.56 Mach, I should be converting 7.7 G and 372 IAS to a turn rate, finding that point on the chart, and looking at the Ps. Yes?

 

Can you re-do that calculation for 7.7 G instead of 7.5 G? 7.5 G was my starting and ending load but only because those were point I arbitrarily picked as the start and end of the turn. For the vast majority of the 4 seconds I was between 7.7 and 7.9 G.

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Posted (edited)
20 minutes ago, Xavven said:

 

Ah, thank you for the correction. I figured there would be additional fuzz here from the speed of sound converting to IAS and some other stuff in there I really don't understand.  So instead of me picking the point based on 7.7 G and 0.56 Mach, I should be converting 7.7 G and 372 IAS to a turn rate, finding that point on the chart, and looking at the Ps. Yes?

 

Can you re-do that calculation for 7.7 G instead of 7.5 G? 7.5 G was my starting and ending load but only because those were point I arbitrarily picked as the start and end of the turn. For the vast majority of the 4 seconds I was between 7.7 and 7.9 G.

 

Sure. 

Speed > 191.4m/s (due to IAS)

Normal load factor = 7.7G.

So the centripetal acceleration = square root (7.7^2 - 1) = 7.63G = 7.63 * 9.8 = 74.774m/s^2

turn rate = centripetal acceleration / speed < 74.774 / 191.4, which is 0.39 rad or 22.4 deg /sec.

 

Please check the chart, at 22.4deg/sec turn rate there is no way it gets near 200 ft /sec ps bleed.

 

One more thing: since your are bleeding both altitude and speed, your equivalent ps bleed is in fact higher than 319 ft /sec. (319 is calculated from altitude loss alone)


Edited by oldtimesake
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Just now, oldtimesake said:

 

Sure. 

Speed > 191.4m/s (due to IAS)

Normal load factor = 7.7G.

So the centripetal acceleration = square root (7.7^2 - 1) = 7.63G = 7.63 * 9.8 = 74.774m/s^2

turn rate = centripetal acceleration / speed < 74.774 / 191.4, which is 0.39 rad or 22.4 deg /sec.

 

Please check the chart, at 22.4deg/sec turn rate there is no way it gets near 200 ft /sec ps bleed.

 

Awesome 🙂  Color me impressed. I'll have to turn that into a Excel sheet so I can do the conversion at will.

 

And Tacview is like 1.5 deg/sec off on its turn rate calculation, then.

 

Alright, using the same chart I was pointing to earlier, picking the point 22.5 deg./sec. and mach 0.56,  Ps should be -200. I'm at -319 at best, and that's not counting my 11 knots of speed lost on top of that. So our DCS F-16 is bleeding way too much energy, and this was giving it every advantage possible... below the GW listed on the chart and no 2x AIM-120 that are included in a DI = 0 viper (see table below)

 

image.png

 

file.php?id=13899&sid=445e0254ebefaa7004

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So I slept on it, and I thought I'd use http://www.csgnetwork.com/aircraftturninfocalc.html to see if it agreed with your math, @oldtimesake. And it does.

 

If I enter 372 knots as the speed and 82.55° as the bank angle to force it to give me 7.7 G, it tells me I should be turning 360° in 16.2 seconds. That's 22.2 deg./sec.

 

It's this part that I'm not understanding:

Quote

So the centripetal acceleration = square root (7.7^2 - 1) = 7.63G

 

We're taking out 1 G here? Is that to account for the force of gravity?

 

I noticed that the Aircraft Turn Information Calculator agrees with Tacview's turn rate information on a mild turn at low G, for example holding 4 G at 500 knots. Where it doesn't agree is on my max performance turn where my bank angle is greater than 90 degrees. The calculator and Tacview disagree on turn rate by almost 3 deg./sec, but that's because I have to put 82.62° as the bank angle to force 7.7 G at 368 knots. It thinks my turn rate is 22.8 deg./sec. but tacview thinks I'm at 25.5 deg./sec. at that point. But again, my actual bank angle wasn't 82°, it was over 90°. I'm not sure it's correct to take the sqrt of 7.72 - 1 here to get centripetal force.... is it?

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8 hours ago, Xavven said:

 

Awesome 🙂  Color me impressed. I'll have to turn that into a Excel sheet so I can do the conversion at will.

 

And Tacview is like 1.5 deg/sec off on its turn rate calculation, then.

 

Alright, using the same chart I was pointing to earlier, picking the point 22.5 deg./sec. and mach 0.56,  Ps should be -200. I'm at -319 at best, and that's not counting my 11 knots of speed lost on top of that. So our DCS F-16 is bleeding way too much energy, and this was giving it every advantage possible... below the GW listed on the chart and no 2x AIM-120 that are included in a DI = 0 viper (see table below)

 

image.png

 

file.php?id=13899&sid=445e0254ebefaa7004

 

I am sure you will be more impressed if you test the PS bleed below mach 0.45. It is 3 times as high as that in flight manual.

51 minutes ago, Xavven said:

So I slept on it, and I thought I'd use http://www.csgnetwork.com/aircraftturninfocalc.html to see if it agreed with your math, @oldtimesake. And it does.

 

If I enter 372 knots as the speed and 82.55° as the bank angle to force it to give me 7.7 G, it tells me I should be turning 360° in 16.2 seconds. That's 22.2 deg./sec.

 

It's this part that I'm not understanding:

 

We're taking out 1 G here? Is that to account for the force of gravity?

 

I noticed that the Aircraft Turn Information Calculator agrees with Tacview's turn rate information on a mild turn at low G, for example holding 4 G at 500 knots. Where it doesn't agree is on my max performance turn where my bank angle is greater than 90 degrees. The calculator and Tacview disagree on turn rate by almost 3 deg./sec, but that's because I have to put 82.62° as the bank angle to force 7.7 G at 368 knots. It thinks my turn rate is 22.8 deg./sec. but tacview thinks I'm at 25.5 deg./sec. at that point. But again, my actual bank angle wasn't 82°, it was over 90°. I'm not sure it's correct to take the sqrt of 7.72 - 1 here to get centripetal force.... is it?

 

Your normal load factor = 7.7G. For horizontal turning, you need 1G vertical component to compensate for the gravity, so the horizontal component is slightly inferior than 7.7G.

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Posted (edited)
3 hours ago, Xavven said:

So I slept on it, and I thought I'd use http://www.csgnetwork.com/aircraftturninfocalc.html to see if it agreed with your math, @oldtimesake. And it does.

 

If I enter 372 knots as the speed and 82.55° as the bank angle to force it to give me 7.7 G, it tells me I should be turning 360° in 16.2 seconds. That's 22.2 deg./sec.

 

It's this part that I'm not understanding:

 

We're taking out 1 G here? Is that to account for the force of gravity?

 

I noticed that the Aircraft Turn Information Calculator agrees with Tacview's turn rate information on a mild turn at low G, for example holding 4 G at 500 knots. Where it doesn't agree is on my max performance turn where my bank angle is greater than 90 degrees. The calculator and Tacview disagree on turn rate by almost 3 deg./sec, but that's because I have to put 82.62° as the bank angle to force 7.7 G at 368 knots. It thinks my turn rate is 22.8 deg./sec. but tacview thinks I'm at 25.5 deg./sec. at that point. But again, my actual bank angle wasn't 82°, it was over 90°. I'm not sure it's correct to take the sqrt of 7.72 - 1 here to get centripetal force.... is it?

 

My guess: The turn rate problem in tacview is that it calculates the turn rate, not horizontal turn rate. The former is dependent on aircraft attitude, while the latter is not. If you fly inverted or your bank angle is superior than 90 deg, the former is slightly higher than the latter.


Edited by oldtimesake
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25 minutes ago, oldtimesake said:

 

Your normal load factor = 7.7G. For horizontal turning, you need 1G vertical component to compensate for the gravity, so the horizontal component is slightly inferior than 7.7G.

 

But in this case I'm banked more than 90 degrees. So I'm not trying to counteract gravity at all -- it should be actually helping my turn. Right? And the turn rate I care about is not just the change in magnetic heading, but the change in my nose position in all coordinates including the vertical.

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2 hours ago, Xavven said:

 

But in this case I'm banked more than 90 degrees. So I'm not trying to counteract gravity at all -- it should be actually helping my turn. Right? And the turn rate I care about is not just the change in magnetic heading, but the change in my nose position in all coordinates including the vertical.

 

Not sure about the correct term, but shouldn't it be " pitch rate " ?

HANGAR

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Posted (edited)
2 hours ago, Xavven said:

 

But in this case I'm banked more than 90 degrees. So I'm not trying to counteract gravity at all -- it should be actually helping my turn. Right? And the turn rate I care about is not just the change in magnetic heading, but the change in my nose position in all coordinates including the vertical.

You may get used to the following question:

"what is the ps at air speed v and turn rate omega?"

However, this is not a valid question. The correct question should be:

"what is the ps at air speed v and normal load factor Ny?"

 

This is because the ps is determined by air speed and normal load factor (regardless of the aircraft attitude), but it is not determined by air speed and turn rate (dependent on aircraft attitude).

 

I convert normal load factor to "horizontal turn rate" instead of of "turn rate" because horizontal turn rate, the term alone, implies the attitude is fixed, the turn rate is comparable, and is not dependent by attitude. The following question is valid:

"what is the ps at air speed v and horizontal turn rate omega?"

 

What you are reading from the Tacview is turn rate, not horizontal turn rate. If the airspeed and normal load factor are fixed, the horizontal turn rate is also fixed, but the turn rate is not, it is dependent on the attitude. If you are facing downward (inverted flying, belly up), the turn rate is slightly higher than horizontal turn rate, because the gravity is contributing to the centripetal acceleration.


Edited by oldtimesake
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4 minutes ago, oldtimesake said:

You may get used to the following question:

"what is the ps at air speed v and turn rate omega?"

However, this is not a valid question. The correct question should be:

"what is the ps at air speed v and normal load factor Ny?"

 

This is because the ps is determined by air speed and normal load factor (regardless of the aircraft attitude), but it is not determined by air speed and turn rate (dependent on aircraft attitude).

 

I convert normal load factor to "horizontal turn rate" instead of of "turn rate" because horizontal turn rate, the term alone, implies the attitude is fixed, and the turn rate is comparable. is not dependent by attitude. The following question is valid:

"what is the ps at air speed v and horizontal turn rate omega?"

 

What you are reading from the Tacview is turn rate, not horizontal turn rate. If the airspeed and normal load factor is fixed, the horizontal turn rate is also fixed, but the turn rate is not, it is dependent on the attitude. If you are facing downward (inverted flying, belly up), the turn rate is slightly higher than horizontal turn rate, because the gravity is contributing to the centripetal acceleration.

 

OK, so basically I need to repeat my test but try to get 24.9 deg./sec. of ITR without banking more than 90 degrees, correct?

 

Just now, oldtimesake said:

I am sure you will be more impressed if you test the PS bleed at mach 0.45 or 0.4. It is 3 times as high as that in flight manual.

 

OK, I'll test that.

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Posted (edited)

OK, so basically I need to repeat my test but try to get 24.9 deg./sec. of ITR without banking more than 90 degrees, correct?

----------------

For now I don't think it is necessary.

a) We are more interested in the ps bleed around ps=0 curve which is more frequently used in air combat.

b) With the G load reading you don't need to maintain a horizontal turning attitude. The equivalent horizontal turn rate can be calculated. 

c) PS bleed rate test at Mach 0.4 or 0.45 is a good start, and I suggest you turn on the AOA indicator, read the G load only, ignore the turn rate


Edited by oldtimesake
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Guys, don't use TacView or the ingame indicators to measure your turn rate. They often show quite different numbers and you never know which one to trust.

The best way is to simply make 4 full circles with stopwatches and then divide the 4*360 degrees by the number of seconds it took. This will also average out the small errors in speed and altitude you make while trying to hold it.

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17 minutes ago, Youda said:

Guys, don't use TacView or the ingame indicators to measure your turn rate. They often show quite different numbers and you never know which one to trust.

The best way is to simply make 4 full circles with stopwatches and then divide the 4*360 degrees by the number of seconds it took. This will also average out the small errors in speed and altitude you make while trying to hold it.

 

Yeah, definitely a good trick for STR. Unfortunately, I would hit the ground trying to test instantaneous turn rate. -400 FPS = crash in a few seconds.

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As I said, the indicated turn rate is not horizontal turn rate. Confusing the two results in big error. I never read the indicated turn rate and I calculate the equivalent horizontal turn rate with airspeed and G loading.

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Alright, here are my tests... I check the unlimited fuel box this time, set fuel to 29% and gun to 10%, putting me at 20,004 lbs  22,004 lbs (EDIT: Corrected typo) and I'm locked to it. This is from a clean (pylons removed) F-16 and weather set to 15° C. This time I'm on the DCS 2.7 patch level though, which was released today.

 

I held a level turn at about 270 knots indicated on the HUD, but Tacview inflated that to 281 for some reason. Anyway, pulling 4.6 G and keeping altitude and speed level, I took this screenshot once stable.

 

Iimage.png

 

Checking the chart and ignoring turn rate, just going off of G and speed alone, it puts me close to the Ps = 0 curve (green dot). It checks out.

 

image.png

 

 

 

 

 

Okay, so what about if I pull 5G and descend to hold speed constant? You can see in the screenshot below that I start by holding a 4.6 G level turn at 266 knots, then pull 5G and the turn tightens. I adjusted my descent rate until I could get 5.0 G and 250-265 knots stable and flew it right into the water. In Tacview, it inflated my speed to 276 despite my lower speed on the HUD in DCS. Here's the screenshot as close as I could get it to 2 seconds before impacting the water. My altitude loss appears to be in the vicinity of -100 FPS. This turn was harder to make completely stable and I varied between 4.7 and 5.0 G initially on the way down but it was pretty stable right before I hit the water.

 

 

 

image.png

 

Checking the chart again, I'm at the green dot again. I'm reasonably close to the Ps = -200 line and I'm not seeing more energy loss than that in DCS.

 

 

image.png

 

I'm not trying to put my thumb on the scale to try to be right or anything. I'm genuinely interested in getting to the right answer. Criticism welcome. If I'm flying it wrong, setting up conditions wrong, etc. I'm happy to be corrected. From what I'm seeing it's not crazy off the chart when just looking at G, speed, and altitude loss (or maintenance). I can't speak to AoA requirements though, and whether this EM chart is true to the real life F-16 blk 50 is another discussion entirely.


Edited by Xavven
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2 minutes ago, Youda said:

You say you were loaded to 20,004 lbs, but the chart is for 22,000. Why so?

 

Sorry, that was a typo. Here's a screenshot from the mission editor. I was at 22,004 lbs.

 

image.png

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19 minutes ago, Xavven said:

 

Alright, here are my tests... I check the unlimited fuel box this time, set fuel to 29% and gun to 10%, putting me at 20,004 lbs and I'm locked to it. This is from a clean (pylons removed) F-16 and weather set to 15° C. This time I'm on the DCS 2.7 patch level though, which was released today.

 

I held a level turn at about 270 knots indicated on the HUD, but Tacview inflated that to 281 for some reason. Anyway, pulling 4.6 G and keeping altitude and speed level, I took this screenshot once stable.

 

Iimage.png

 

Checking the chart and ignoring turn rate, just going off of G and speed alone, it puts me close to the Ps = 0 curve (green dot). It checks out.

 

image.png

 

 

 

 

 

Okay, so what about if I pull 5G and descend to hold speed constant? You can see in the screenshot below that I start by holding a 4.6 G level turn at 266 knots, then pull 5G and the turn tightens. I adjusted my descent rate until I could get 5.0 G and 250-265 knots stable and flew it right into the water. In Tacview, it inflated my speed to 276 despite my lower speed on the HUD in DCS. Here's the screenshot as close as I could get it to 2 seconds before impacting the water. My altitude loss appears to be in the vicinity of -100 FPS. This turn was harder to make completely stable and I varied between 4.7 and 5.0 G initially on the way down but it was pretty stable right before I hit the water.

 

 

 

image.png

 

Checking the chart again, I'm at the green dot again. I'm reasonably close to the Ps = -200 line and I'm not seeing more energy loss than that in DCS.

 

 

image.png

 

I'm not trying to put my thumb on the scale to try to be right or anything. I'm genuinely interested in getting to the right answer. Criticism welcome. If I'm flying it wrong, setting up conditions wrong, etc. I'm happy to be corrected. From what I'm seeing it's not crazy off the chart when just looking at G, speed, and altitude loss (or maintenance). I can't speak to AoA requirements though, and whether this EM chart is true to the real life F-16 blk 50 is another discussion entirely.

 

Oh boy you are again reading directly the indicated turn rate...

 

True air speed 282knots = 145.07m/s

Centripedal acceleration =  square root (4.6^2 - 1)G = 44.001m/s^2

Horizontal turn rate = 44.001 / 145.07 * 57.3 = 17.37deg/sec

From the chart it should be around 19.5deg/sec. That is not close at all.

Even the direct turn rate reading is 18.5deg/s and that is still far from being checked out.

 

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Just now, oldtimesake said:

Oh boy you are again reading directly the indicated turn rate...

 

True air speed 282knots = 145.07m/s

Centripedal acceleration =  square root (4.6^2 - 1)G = 44.001m/s^2

Horizontal turn rate = 44.001 / 145.07 * 57.3 = 17.37deg/sec

From the chart it should be around 19.5deg/sec. That is not close at all.

Even the direct turn rate reading is 18.5deg/s and that is still far from being checked out.

 

 

Huh? No, I went to the mach 0.4 line, then found the 4 G line and the 5 G line, counted there are 8 squares between them, and since I was pulling 4.6 G I put my green dot on the 4th/5th line up from where the 4 G line intersects the 0.4 mach line.

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Posted (edited)
5 minutes ago, Xavven said:

 

Huh? No, I went to the mach 0.4 line, then found the 4 G line and the 5 G line, counted there are 8 squares between them, and since I was pulling 4.6 G I put my green dot on the 4th/5th line up from where the 4 G line intersects the 0.4 mach line.

That won't explain the difference of 19.5deg/sec (manual value) and 17.4deg/sec (test value).

The only explanation is that the speed of sound in manual is slightly different from that in DCS, making the mach number slightly different. Only the true air speed (TAS) is reliable.


Edited by oldtimesake
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Just now, oldtimesake said:

That won't explain the difference of 19.5deg/sec (manual value) and 17.4deg/sec (test value).

 

Sorry, I'm not understanding at all. Help me?

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1 minute ago, Xavven said:

 

Sorry, I'm not understanding at all. Help me?

The only explanation is that the speed of sound in manual is slightly different from that in DCS, making the mach number slightly different. Only the true air speed (TAS) is reliable.

Let's calculate the speed of sound in flight manual:

 

pick a point from flight manual: 9G, 0.7Mach, 21.5deg/sec.

 

speed = centripetal acceleration / angular vilocity = square root(9^2 - 1) * 9.8 / (21.5 / 57.3) = 87.653 / 0.3752 = 233.6167 m / s = 0.7 mach

 

speed of sound in manual = 233.6167 / 0.7 = 333.73 m/s

 

speed of sound in DCS = 145.07 / 0.42 = 345.4 m/s

 

 

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1 minute ago, oldtimesake said:

The only explanation is that the speed of sound in manual is slightly different from that in DCS, making the mach number slightly different. Only the true air speed (TAS) is reliable.

 

Oh, I've been using Google to convert mach and knots, and assumed that since I'm close to sea level the numbers are close enough. Whether you use my HUD number of around 270 or the TAS value in Tacview of 282. the mach is somewhere from 0.4 to 0.42. Not enough difference to throw me away from the Ps=0 curve significantly. Are you seeing the numbers differently?

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Posted (edited)
18 minutes ago, Xavven said:

 

Oh, I've been using Google to convert mach and knots, and assumed that since I'm close to sea level the numbers are close enough. Whether you use my HUD number of around 270 or the TAS value in Tacview of 282. the mach is somewhere from 0.4 to 0.42. Not enough difference to throw me away from the Ps=0 curve significantly. Are you seeing the numbers differently?

Let's calculate the speed of sound in flight manual:

 

pick a point from flight manual: 9G, 0.7Mach, 21.5deg/sec.

 

speed = centripetal acceleration / angular vilocity = square root(9^2 - 1) * 9.8 / (21.5 / 57.3) = 87.653 / 0.3752 = 233.6167 m / s = 0.7 mach

 

speed of sound in manual = 233.6167 / 0.7 = 333.73 m/s

 

speed of sound in DCS = 145.07 / 0.42 = 345.4 m/s


Edited by oldtimesake
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