Zone 6: Air Source Off - Modeled?

[fat creason]

2 hours ago, Callsign JoNay said:

Is that going to bust the WCS and turn the cabin into a convection oven? If so, then that sounds like more than a miniscule energy pull.

 

I think you're somewhat confused on how typical fighter aircraft bleed systems work and the bleed system's impact on thrust. You're focusing on the amount of thermodynamic cooling work needed, which isn't very relevant. The reason why high bleed demands can affect thrust is related to the mass flow diverted from the engine to the cabin and avionics cooling ducts, not the cooling work required. The amount of bleed air needed in the F-14 for the ECS and avionics relative to the total mass flow entering the engine is very small. This is drastically different from a transport aircraft with huge bleed demands. Typically the largest consumer of bleed air on an aircraft will be the anti-ice system, assuming it's powered via bleed air and not electric.

Disabling your gun and cooking your HUD, VDI, WCS and other misc avionics to try and outclimb an F-16 isn't a smart play or a cool "trick" to one-up your opponent. We have no documentation or SME knowledge that suggests there is any appreciable thrust increase from turning off the air, and we plan to add consequences for doing so in the future.

[Gunslinger22]

40 minutes ago, fat creason said:

 

I think you're somewhat confused on how typical fighter aircraft bleed systems work and the bleed system's impact on thrust. You're focusing on the amount of thermodynamic cooling work needed, which isn't very relevant. The reason why high bleed demands can affect thrust is related to the mass flow diverted from the engine to the cabin and avionics cooling ducts, not the cooling work required. The amount of bleed air needed in the F-14 for the ECS and avionics relative to the total mass flow entering the engine is very small. This is drastically different from a transport aircraft with huge bleed demands. Typically the largest consumer of bleed air on an aircraft will be the anti-ice system, assuming it's powered via bleed air and not electric.

Disabling your gun and cooking your HUD, VDI, WCS and other misc avionics to try and outclimb an F-16 isn't a smart play or a cool "trick" to one-up your opponent. We have no documentation or SME knowledge that suggests there is any appreciable thrust increase from turning off the air, and we plan to add consequences for doing so in the future.

Just curious, when we get those consequences added will the effects on the pilot be added similar to how Deka have done within the JF-17? 

Edited July 28, 2021 by Gunslinger22

[Callsign JoNay]

1 hour ago, fat creason said:

 

The amount of bleed air needed in the F-14 for the ECS and avionics relative to the total mass flow entering the engine is very small.

 

I understand that it's small, but I also know it's not zero. The laws of physics say you can't do work without energy. We may not have numbers but we know it's not zero, which is how it's modeled in the sim.

 

You say you have SMEs that have claimed it's inconsequential, ok. I have no leg to stand on except for the video I posted and other similar stories from Tomcat aircrew.

 

 

Once again, saying that it's not a good idea to overheat the avionics in combat is missing the point. I don't know why you guys keep bringing that up.

[Wizard_03]

3 hours ago, draconus said:

Air source is changed in pilot's pit and they are buttons.

 

Oh my bad I can't read, I thought we were still talking about mid compressor bypass. 

 

That sounds even dumber, let me take my hand off the stick and burn out all the avionics in the middle of a vertical fight. 

[draconus]

7 hours ago, Callsign JoNay said:

I understand that it's small, but I also know it's not zero.

We also don't have canopy pressure bottles implemented so you can open and close it million times without power.

We also don't take pilot weight into consideration. It's not zero so it adds to the gross weight so it affects the flight model!

Our pilot does not need to eat or sleep.

See where I'm going? They set a line somewhere. They had to. Otherwise it's feature creep. You can't simulate everything so they leave out stuff that does not matter much.

Edited July 29, 2021 by draconus

[captain_dalan]

Academically speaking, how much change in thrust would we be talking about here? 1000-2000pds?

EDIT: and would the change be proportional in dry and wet thrust?

Edited July 29, 2021 by captain_dalan

[Callsign JoNay]

7 hours ago, draconus said:

We also don't have canopy pressure bottles implemented so you can open and close it million times without power.

We also don't take pilot weight into consideration. It's not zero so it adds to the gross weight so it affects the flight model!

Our pilot does not need to eat or sleep.

See where I'm going? They set a line somewhere. They had to. Otherwise it's feature creep. You can't simulate everything so they leave out stuff that does not matter much.

 

 

Can you link me to any former F-14 crew telling cool stories about canopy pressure bottles or how they out flew their opponent by going on a diet? 

 

It's not feature creeping. We have stories of pilots using these zone 6 tricks in training/combat. They are part of the lore and mythology of the Tomcat. One of those tricks, the mid compression CB is one of those tricks already in the sim.

[tspencer227]

35 minutes ago, Callsign JoNay said:

 

It's not feature creeping. We have stories of pilots using these zone 6 tricks in training/combat. They are part of the lore and mythology of the Tomcat. One of those tricks, the mid compression CB is one of those tricks already in the sim.

 

Dude, I don't think you understand the difference between a sea story and a fairy tale (I'll give you a hint, one begins with, "once upon a time"), but needless to say they both tend to be over exaggerations of what may or may not have actually happened.

 

This seems a really dumb hill to die on, ESPECIALLY when you have everybody here with even a slight passing interest or background in thermodynamics, engineering, or aviation maintenance telling you why this wouldn't EVER be a thing. 

[Golo]

1 hour ago, captain_dalan said:

Academically speaking, how much change in thrust would we be talking about here? 1000-2000pds?

EDIT: and would the change be proportional in dry and wet thrust?

NATOPS says operation of MCB reduces thrust by aprox. 3000 lbs per engine on zone 5 takeoff. I think in dry thrust the MCB is inoperative.

 

Now that is only from MCB which is from 7th stage compressor, there are 3 more air bleeds, from 9th, 12th and 16th stage which can be switched off. But If TF-30 is anything like engines I have experience with, MCB would have highest flow mass out the compressor, other bleeds would not help much for thrust gain, and disabling them is really stupid anyways.

 

But in flight MCB would only help in higher AOA regime (as was said) and its not really wort decreasing engine stall margins especially in high AOA/Sideslip (BFM) situations.

[Callsign JoNay]

9 minutes ago, tspencer227 said:

 

This seems a really dumb hill to die on, ESPECIALLY when you have everybody here with even a slight passing interest or background in thermodynamics, engineering, or aviation maintenance telling you why this wouldn't EVER be a thing. 

 

Lighten up man. Is this a discussion forum or a shut up and fall in line forum?

 

I know maintainers and pilots who've told me they can feel the effects of air/enviro and bypass systems in their airframes, admittedly not F-14s.

 

 

[r4y30n]

Performance aside, I had heard somewhere of pilots turning bleeds off or to ram in the groove so they can hear the engines without the ECS noise, any truth to that?

[Quid]

Direct from Hoser:

 

"Zone 6: On command, the RO [sic] would go to standby on the AWG-9 as the pilot would punch "Air Source Off". This produced between 850 to 1125 pounds of additional thrusties: cutting off the TF-30 16th stage bleed air used for AWG-9 cooling, pressurization, and a/c.  Simultaneously, the pilot would unload, roll in the droops and manually sweep the wings to 68 degrees.  Why wait to let the wings blow back (drag) and the lifties were certainly not needed.  And of course, since the task at hand was getting the hell outta Dodge post haste and getting on the deck (thereby shrinking the 9L envelope), the radar was not in the equation since it did not look aft.  'Turk' Pentecost and I discussed these unique Turkey procedures with Monroe "Hawk" Smith (then CO of TOPGUN) and it was mutually decided that although it works, we should keep it close to the vest on a "need to know" level."

 

So, Hoser may not have explained it precisely (reclaiming 850-1125lbs of thrust, rather than producing it), but also note that he specified he would use it as a bug out assist, not going into or already being in the middle of a fight.

[Callsign JoNay]

A lot of comments in here did not age well.

[near_blind]

 

58 minutes ago, Callsign JoNay said:

A lot of comments in here did not age well.

Not a new quote, and not the first time it's been brought up.

 

I'm still going to trust Victory over stories of Hoser trying to flex on the Air Force during the largest peace time inter service dick waving contest of the 1970s. 

[Quid]

26 minutes ago, near_blind said:

 

Not a new quote, and not the first time it's been brought up.

 

I'm still going to trust Victory over stories of Hoser trying to flex on the Air Force during the largest peace time inter service dick waving contest of the 1970s. 

No, not new I used it before as you linked, but the specific question came up, and it was relevant.  Also, that's not a story of Hoser, that was actually Hoser explaining that.  The main reason I even posted it again is because there's quotes in here talking about how it either did nothing, or was never done, or whatever.  It was done.  It did affect the available thrust going out the back of the jet.  As Victory explained, there were significant ramifications for doing so, and like I said in my original post, even Hoser had a very, very narrow use for it, and frankly, there isn't any data as to how much more likely someone was to get out of the 9L envelope in ACE/AIM based on using "Zone 6" or not.  I wouldn't expect any pilot to use it in a real-world combat scenario; ACE/AIM, by admission of several of its participants, basically turned into a Kill-to-Loss competition, so any advantage that could be taken was.  The fact that you could fry electronics beyond the radar doing this makes its practical application in combat operations even less likely.  That doesn't change the fact that people did it under specific circumstances.  I don't know, call me just another nit-picking ass; there's plenty of them to go around in these parts...

[near_blind]

@Quid, my comment wasn't meant to be a slight towards you and I apologize if it came off like that. I'm not against adding the performance increase with bleed air off (assuming it fries your electronics), I just think there are higher priorities when it comes to the FM and engines. Furthermore the whole drama over landing flaps and their damage model has left me rather jaded when it comes to the memetic Tomcat Tactics. After a while, watching people insist that extraordinary gambits were mundane tactics in the face of developers and SMEs explaining to the contrary gets frustrating. 

[captain_dalan]

19 hours ago, Golo said:

NATOPS says operation of MCB reduces thrust by aprox. 3000 lbs per engine on zone 5 takeoff. I think in dry thrust the MCB is inoperative.

 

Now that is only from MCB which is from 7th stage compressor, there are 3 more air bleeds, from 9th, 12th and 16th stage which can be switched off. But If TF-30 is anything like engines I have experience with, MCB would have highest flow mass out the compressor, other bleeds would not help much for thrust gain, and disabling them is really stupid anyways.

 

But in flight MCB would only help in higher AOA regime (as was said) and its not really wort decreasing engine stall margins especially in high AOA/Sideslip (BFM) situations.

Thanks mate, that explains a lot! 

[Quid]

4 hours ago, near_blind said:

@Quid, my comment wasn't meant to be a slight towards you and I apologize if it came off like that. I'm not against adding the performance increase with bleed air off (assuming it fries your electronics), I just think there are higher priorities when it comes to the FM and engines. Furthermore the whole drama over landing flaps and their damage model has left me rather jaded when it comes to the memetic Tomcat Tactics. After a while, watching people insist that extraordinary gambits were mundane tactics in the face of developers and SMEs explaining to the contrary gets frustrating. 

It's good, I didn't really take it as a slight - that last part of my own response was a critique at myself because I realized "holy s&*+, this is a nitpick."  I also understand the frustration, and agree with you that this really should not be a priority in any regard.

[Naquaii]

8 minutes ago, Quid said:

It's good, I didn't really take it as a slight - that last part of my own response was a critique at myself because I realized "holy s&*+, this is a nitpick."  I also understand the frustration, and agree with you that this really should not be a priority in any regard.

 

This is not about being a priority or not, rather it's about not believing it. The amount of thrust talked about in the quote you posted (without source I might add) just isn't believable from just turning off the bleed switch used for the ECS. I'd say it should be around like 100 times smaller and then you can start to see why we're saying it wouldn't be noticable and wouldn't make a difference.

[Quid]

9 hours ago, Naquaii said:

 

This is not about being a priority or not, rather it's about not believing it. The amount of thrust talked about in the quote you posted (without source I might add) just isn't believable from just turning off the bleed switch used for the ECS. I'd say it should be around like 100 times smaller and then you can start to see why we're saying it wouldn't be noticable and wouldn't make a difference.

Source is the book "Hoser Here, Shoot!," by the Tomcat-Sunset staff, page 86 (originally part of a longer conversation at T-S).  In the end, Hoser never said how he got to that number.  As you all at HB has been modelling the plane to a high degree of fidelity, and looking into these kinds of things from an engineering standpoint, it's entirely possible that he miscalculated how much he was getting out of it.

[Victory205]

42 minutes ago, Quid said:

Source is the book "Hoser Here, Shoot!," by the Tomcat-Sunset staff, page 86 (originally part of a longer conversation at T-S).  In the end, Hoser never said how he got to that number.  As you all at HB has been modelling the plane to a high degree of fidelity, and looking into these kinds of things from an engineering standpoint, it's entirely possible that he miscalculated how much he was getting out of it.

Hoser calculate engine thrust? That’s a good one. 
 

I understand that few of you have the background to discern the difference between BS and truth, but understand that there are made up embellishments everywhere, including on the various podcasts and media channels, where even “popular” creators are focused on self promoting for an audience of lay people. 
 

You’d do better practicing your tactical maneuvers than focusing on minutiae that doesn’t matter whatsoever on the battlefield. You aren’t being held back by some misplaced notion of enhanced thrust, it’s your lack of understanding of the geometry and execution of the maneuver. 

[captain_dalan]

On 7/31/2021 at 12:54 AM, Victory205 said:

 

You’d do better practicing your tactical maneuvers than focusing on minutiae that doesn’t matter whatsoever on the battlefield. You aren’t being held back by some misplaced notion of enhanced thrust, it’s your lack of understanding of the geometry and execution of the maneuver. 

I think why many people like to explore or see such claims simulated in the module is mostly because of the peculiarity and love for the plane and the legends around it (or as you dub them here, minutiae), rather then trying to exploit them in tactical situations. Like the people trying to hit mach 2.4+, or the people with the circuit breakers
Many, but not all. I'm sure some would still to make regular practice out of niche circumstantial occurrences

Edited August 1, 2021 by captain_dalan

[Callsign JoNay]

1 hour ago, captain_dalan said:

I think why many people like to explore or see such claims simulated in the module is mostly because of the peculiarity and love for plane and the legends around it (or as you dub them here, minutiae), rather then trying to exploit them in tactical situations. Like the people trying to hit mach 2.4+, or the people with the circuit breakers
Many, but not all. I'm sure some would still to make regular practice out of niche circumstantial occurrences

 

Exactly. Not sure where the extreme disdain is in this thread is coming from. 

[Naquaii]

8 minutes ago, Callsign JoNay said:

 

Exactly. Not sure where the extreme disdain is in this thread is coming from. 

 

No disdain from our side at least. We simply do no agree upon what you and your sources are claiming about setting the air source to off and what it'd do to the thrust.

[Noctrach]

6 hours ago, Callsign JoNay said:

 

Exactly. Not sure where the extreme disdain is in this thread is coming from. 

It's definitely not disdain, but from me personally these kinds of requests come off as people trying to find a way to "one-up" the opposition with one-off tricks, rather than flying a better airplane. I've had similar headbutting with pilots I've RIO'd for who insisted on doing tricks with flaps or manual wing sweep which invariably resulted in disaster, because they would forget to restore normal function under stress. All to get an "advantage" that they wouldn't have needed if they knew how to fly clean and proper BFM.

 

I think the perceived touchiness is a combination of the same shared passion for the product and a fear that these kinds of discussions are just side-tracking for the sake of "shenanigans".