F-16 over-performing at low altitude

The Viper seams to be 100 knots too fast on the deck then chart or its intake design allow.

The 1.2 mach is the limit, but in DCS you can go 1.39 with no issue.

Screenshot:

Chart:

1.16

The referenced manual number is lower right, but I did cross reference it with two other charts.

Track:

speedtest.trk

1.2M is the placard limit for KCAS at sea level. The turn performance charts show that it is still accelerating at 0.25G (~0.007M/s) at that speed. I agree 1.41 (highest I have hit) is a bit much, looking at the Ps=0 line it should fall around 1.32.

To prevent administrative action you should remove the chart. Unfortunately it is not allowed to post manuals or parts of it in these forums from or newer than 1980. Tell Bignewy or Nineline, where to find the chart so they can have a look at it.

To the topic: One limit of this aircraft is 800kts. But that doesn't mean it stops its acceleration there. You as the pilot are responsible to keep the aircraft within its limits. And when 800kts is the allowed limit, you won't get information in a flightmanual about what happens above this limit.

Edit: Not saying this is correct behavior of the Sim.

Fox

To prevent administrative action you should remove the chart. Unfortunately it is not allowed to post manuals or parts of it in these forums from or newer than 1980. Tell Bignewy or Nineline, where to find the chart so they can have a look at it.

The charts are public available.

To the topic: One limit of this aircraft is 800kts. But that doesn't mean it stops its acceleration there. You as the pilot are responsible to keep the aircraft within its limits. And when 800kts is the allowed limit, you won't get information in a flightmanual about what happens above this limit.

 

 

Edit: Not saying this is correct behavior of the Sim.

 

Fox

Although, we usual are not sure what happens when limits are passed, for jet engines a good guess is compressor stall or AB starvation.

But one would expect that DEC would step in and actually limit it to 1.2 mach and prevent any damage.

The Viper seams to be 100 knots too fast on the deck then chart or its intake design allow.

I suggest reading Semper Viper; Don't stretch the limits.

Al tho outdated in many ways, it does talk about the why that speed limit is in the manual.

This is a direct PDF link to Semper viper, CODE One magazine. Page 88 has a good article about it. Keep in mind this is on old F-16, some of the details will not apply to the DCS F-16

https://www.codeonemagazine.com/images/C1_SemperViper_1_1271449318_9999.pdf

I suggest reading Semper Viper; Don't stretch the limits.

 

Al tho outdated in many ways, it does talk about the why that speed limit is in the manual.

 

This is a direct PDF link to Semper viper, CODE One magazine. Page 88 has a good article about it. Keep in mind this is on old F-16, some of the details will not apply to the DCS F-16

https://www.codeonemagazine.com/images/C1_SemperViper_1_1271449318_9999.pdf

Excellent text! Thank you! To quote:"This is a very real physical limit. I strongly encourage you to respect it."

I wouldn't mind if a random "engine fail" would be generated with increasing random percent pass 800kts as solution.

Excellent text! Thank you! To quote:"This is a very real physical limit. I strongly encourage you to respect it."

 

I wouldn't mind if a random "engine fail" would be generated with increasing random percent pass 800kts as solution.

Did you read it? The F-16 has been above 800knots. Did you read what he states as the speed limit or the reason that speed limit is in the manual?

The charts are public available.

...

 

That was only a friendly reminder to prevent a warning or suspension for you.

Rules:

 

1.16 Posting of images, file links, file sharing links, and copying and pasting information is prohibited if the source document is from a classified or ITAR controlled source.

When posting aircraft, sensor or weapon information more recent than 1980, you must also include the source of the document showing that it is 100% public and verified as not from a classified or non-ITAR controlled source. To not do so will result in the removal of the message.

 

Posting information from a classified or ITAR-controlled source will result in the message being removed and a 20% warning and one-week suspension (dependent on warning level).[/Quote].

 

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Although, we usual are not sure what happens when limits are passed, for jet engines a good guess is compressor stall or AB starvation.

But one would expect that DEC would step in and actually limit it to 1.2 mach and prevent any damage.

Do you know this is a engine limit? Can be a structural limit before that. Or hydraulics. Or the controlsystem can't handle the aerodynamic changes involved. Many factors possible for this 800KIAS limit.

 

Does the real manual state, that the DEC prevents the aircraft from reaching speeds in excess of 800KIAS? If not, then don't expect it to do so. I haven't found the time to read through the manual yet.

 

Fox

 

 

edit: NineLine was faster.

Did you read it? The F-16 has been above 800knots. Did you read what he states as the speed limit or the reason that speed limit is in the manual?

Yes I did and that is the exact point of the text. Will a car engine blow up if you go 500 rpm in to red line... it won't... but will it blow up for sure if you keep going...

yes... he has been up to 845 knots UNDER test conduction. Also said that he would go over 800 knots if his life depended on it, but also stated to quote: "This is a very real physical limit, I strongly encourage you to respect it"

All in all the text is called "Don't stretch the limits"

The engine is not the limit, the intake is not. The limit is the canopy and the fact that it has not been qualified above those speeds.

The only engine that had a problem was the PW-200, the F-16 stop using that engine over 20 years ago, so engine damage is irrelevant on the PW-220, PW-229 and all GE engines.

Oh well, wish you would have reed the article, is very good. Oh well. Moving on.

Are the FLCS oscillations normal that start to happen <= 15.000ft at around 580kts IAS when low on fuel?

The engine is not the limit, the intake is not. The limit is the canopy and the fact that it has not been qualified above those speeds.

 

The only engine that had a problem was the PW-200, the F-16 stop using that engine over 20 years ago, so engine damage is irrelevant on the PW-220, PW-229 and all GE engines.

 

Oh well, wish you would have reed the article, is very good. Oh well. Moving on.

Car engine was illustration what happens when you go over the red line... No body said that the Viper would blow up at 801 kts... but it will if you keep going.... and the article is clear, "don't stretch the limits!", 800 kts in this case.

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This is a direct PDF link to Semper viper, CODE One magazine. Page 88 has a good article about it. Keep in mind this is on old F-16, some of the details will not apply to the DCS F-16

https://www.codeonemagazine.com/images/C1_SemperViper_1_1271449318_9999.pdf

Thank you. Very interesting!!

Fox

I was already very familiar with the story, I did NOT know it was only the older Pratt motors. So it used to be a physical limit (engine might explode above this speed) which in turn was replaced by an economical limit (we aren't going to test the canopy past 800 because the engine will explode, oh that doesn't happen anymore? well we aren't going to spend money on testing it NOW)

Car engine was illustration what happens when you go over the red line... No body said that the Viper would blow up at 801 kts... but it will if you keep going.... and the article is clear, "don't stretch the limits!", 800 kts in this case.

Why do you ignore that this concerns an early F-16 with a different engine?

Why do you ignore that this concerns an early F-16 with a different engine?

The chart with the limit is of the engine variant we have, also the pilot keeps repeating that 800 kts is a real physical limit and you guys keep ignoring it since it suites you... it's like saying MiG-25 can go 3.2 mach since it did over the Sinai once (but it did blow up the engines) or F-15 can pull 13 g (it can but it warped the air-frame)... what I am trying to say to you, yes, Viper can go over 800, but there are consequences, and the lower you are the bigger they are since of the drag and heat build up. And currently it is over-performing by ~12% without consequences.

-1

SYSTEM AIRSPEED LIMITATIONS

Refer to Figure 5-3, Figure 5-5, and Figure 5-6.

MAXIMUM AIRSPEED OPERATING LIMITATIONS

Refer to Figure 5-3. Maximum operating airspeed is 800 knots from sea level to 30,000 feet MSL. Above 30,000 feet MSL, the aircraft is limited to 2.05 mach.

Refer to Figure 5-6 and TO 1F-16CM-1-2. Maximum operating airspeed/mach may be reduced as a result of system restrictions or stores limitations.

So, lets jump to Figure 5-3, Figure 5-5, and Figure 5-6 ... we see:

Figure 5-3 is ENGINE - OPERATION ENVELOPE (and you will found there the 800KIAS/M1.2 until 30,000ft limitation then M2.05 above 30,000ft on the diagram for the four engines types GE100 GE129 and PW220 PW229)

Figure 5-5 is Cable/Net Arrestment Limits

Figure 5-6 is Airspeed Limitations (Systems) => see below

Canopy Open or in Transit: 70KIAS

LG Extended or in Transit: 300KIAS/M0.65 (whichever is less)

AR Door Opening/Closing: 400KIAS/M0.85 (whichever is less)

AR Door Open: 400KIAS/M0.95 (whichever is less)

Flight in Severe Turbulence (+/-3g) 500KIAS

... nothing here about canopy in-flight limits nor airframe airspeed limits.

-2 SUPPLEMENTAL FLIGHT MANUAL is curves & diagrams and refer back to -1's limitations chapter and stores limitations (see above).

...

I am not a engineer. But as a pilot POV regarding the Dash-1, and, unless somebody prove it wrong, I understand that the max upper airspeed limits of the F-16C (800KIAS) ... is ... an engine limitation.

Regards.

AFAIK, it's a frame limit not an engine limit.

Its temperature limit for the canopy and other frame componenets.

Engine itself is fine. Both the -229 and -129 are used by the F-15E which has higher top speed.

In some contdtions the airframe can give you more then it can handle.

Engine limitations do exist, like engine RPM must remain above some value when supersonic. You can pull throttle to idle, but engine will be maintaining near MIL till speed drops (engine controller logic, just like nozzle maintaining combustion chamber pressure)

The chart with the limit is of the engine variant we have, also the pilot keeps repeating that 800 kts is a real physical limit and you guys keep ignoring it since it suites you... it's like saying MiG-25 can go 3.2 mach since it did over the Sinai once (but it did blow up the engines) or F-15 can pull 13 g (it can but it warped the air-frame)... what I am trying to say to you, yes, Viper can go over 800, but there are consequences, and the lower you are the bigger they are since of the drag and heat build up. And currently it is over-performing by ~12% without consequences.

In both those examples, the aircraft did not spontaneously explode in midair or fail in dramatic fashion. The MiG's engine was replaced when it rtb'd. The F-15 was decommissioned. In the context of a video game, these ''consequences'' are irrelevant.

This is the same mentality that in Il-2 CloD resulted in engines burning out if you WEP'd more than 3 minutes with a scripted action. These are NOT ''hard you die limits''. They are structural and engineering limits because in real life the government doesn't want to pay for a new airplane everytime some neckbeard goes up in the air and decides to do something stupid. In a video game you have a endless stream of fresh aircraft, so many of these limits do not matter.

In both those examples, the aircraft did not spontaneously explode in midair or fail in dramatic fashion. The MiG's engine was replaced when it rtb'd. The F-15 was decommissioned. In the context of a video game, these ''consequences'' are irrelevant.

 

This is the same mentality that in Il-2 CloD resulted in engines burning out if you WEP'd more than 3 minutes with a scripted action. These are NOT ''hard you die limits''. They are structural and engineering limits because in real life the government doesn't want to pay for a new airplane everytime some neckbeard goes up in the air and decides to do something stupid. In a video game you have a endless stream of fresh aircraft, so many of these limits do not matter.

Yeah, people try to "game"/"meme" the DCS all the time when it suite them (usually get cross when others meme them).

the bottom line no body here can say what happens to the viper on the deck above 1.2 mach, but Lockheed Martin and the test Pilot said, DON'T DO IT!!! So there is NO reason why our Viper should be able to do 1.4 mach with no issue (keep in mid that more powerful F-15 is also restricted and can't go over 1.25 on the deck both in DCS and RL)

The charts are public available.

 

 

 

Although, we usual are not sure what happens when limits are passed, for jet engines a good guess is compressor stall or AB starvation.

But one would expect that DEC would step in and actually limit it to 1.2 mach and prevent any damage.

First off..when something is available on the internet it is not a guarantee that it is 'legal'.

Second...are you sure it is an engine limit? I think it is a structural limit.

Yeah, people try to "game"/"meme" the DCS all the time when it suite them (usually get cross when others meme them).

 

the bottom line no body here can say what happens to the viper on the deck above 1.2 mach, but Lockheed Martin and the test Pilot said, DON'T DO IT!!! So there is NO reason why our Viper should be able to do 1.4 mach with no issue (keep in mid that more powerful F-15 is also restricted and can't go over 1.25 on the deck both in DCS and RL)

Nope. The bottom line is that it can and if a stupid pilot will do it the manufacturer won't guarantee structural integrity of the airframe, specifically the canopy being the weakest link.

Therefore ED should model the event of exceeding VnE faithfully, because it can be pilot induced.

Just the same as you can exceed design limit load in airplanes without FBW like the F-14, F-5E, P-51D, etc and the damage model of DCS can and does model the effects of a bent airframe and the structural failures when exceeding ultimate load limit (control surfaces loss, wings breaking etc).

Whether the degradation or failure of structural integrity of the canopy at mach 1.41 is immediate or over time is a different discussion.

Cheers!

Hi!

 

Second...are you sure it is an engine limit? I think it is a structural limit.

Post#17

The 800KIAS/M1.2 (<30,000ft) / M2.05 (>30,000ft) limitation is from -1 F-16 FLIGHT MANUAL in ENGINE OPERATIONAL ENVELOPE diagrams (figure 5-3).

And probably because F-16 don't have a variable geometry inlet.

Airframe structural dynamic pressure limitation is certainly way above that (I hope for F-16 pilots) but it is written nowhere in the book.

Cheers.

Also guys please make a difference of going over the limit up high and down low on the deck, two different things.

For me, it seems like this issue could be better rectified by having it implemented within the DCS damage model, as I reckon it probably doesn't.