F-14B acceleration correct?

[Cab]

1 minute ago, Mistang said:

https://www.military.com/video/military-aircraft-operations/aviation-accidents/f-15-in-flight-breakup/661029574001
 

the f15 might actually break apart at pretty low sustained g.

chock, thank you.

No, not really. It's a 9g jet.

[Mistang]

4 minutes ago, jcdata said:

No hard limiter on the 15 either.. like the 14..the limiter is the person yanking on the pole

Sent from my SM-G998U using Tapatalk
 

Are we talking about an abstract new aircraft limit or the actual? Because most real life aircraft are extremely old and fatigued. 

[GGTharos]

18 minutes ago, Mistang said:

Not sure.

 

from the dcs manual

 

 

included airframe improvements that increased G limits for production F-15A/B/C/D from 7 to 9 Gs,

 

The CAS is the control augmentation system which does very neat things, but has zero limiters ... for g or AoA.   The F-15A received no air-frame improvements that I know of (but who knows?), just the OWS which made it a 9g jet.

There's no limiter on F-15A-D, you can pull as many Gs as the maximum deflection of the horizontal stabs will give you at a given speed, period.  That g has been determined to be 12.5 or so.

 

I don't know why you keep clinging to the glove vanes on the F-14, they are completely meaningless and it makes you look like you really don't understand the very thing you wish to argue about.

[Mistang]

Just now, GGTharos said:

 

The CAS is the control augmentation system which does very neat things, but has zero limiters ... for g or AoA.   The F-15A received no air-frame improvements that I know of (but who knows?), just the OWS which made it a 9g jet.

There's no limiter on F-15A-D, you can pull as many Gs as the maximum deflection of the horizontal stabs will give you at a given speed, period.  That g has been determined to be 12.5 or so.

 

I don't know why you keep clinging to the glove vanes on the F-14, they are completely meaningless and it makes you look like you really don't understand the very thing you wish to argue about.

If we're taking about a new build tomcat in 2021 flying to Siberia to dogfight a PAK, sure. But in real life these aircraft are completely depreciated and die at 6g.

[GGTharos]

11 minutes ago, Mistang said:

https://www.military.com/video/military-aircraft-operations/aviation-accidents/f-15-in-flight-breakup/661029574001
 

the f15 might actually break apart at pretty low sustained g.

chock, thank you.

 

That was a faulty longeron, fatigued after much use.  So no, it might not break apart at low sustained g.  The problem was identified and fixed in other aircraft which received faulty longerons.

[Frosty2124]

1 minute ago, GGTharos said:

 

The CAS is the control augmentation system which does very neat things, but has zero limiters ... for g or AoA.   The F-15A received no air-frame improvements that I know of (but who knows?), just the OWS which made it a 9g jet.

There's no limiter on F-15A-D, you can pull as many Gs as the maximum deflection of the horizontal stabs will give you at a given speed, period.  That g has been determined to be 12.5 or so.

 

I don't know why you keep clinging to the glove vanes on the F-14, they are completely meaningless and it makes you look like you really don't understand the very thing you wish to argue about.

he kinda doesn't, and refuses to acknowledge it

[IronMike]

2 hours ago, Mistang said:

Anyway whatever I appreciate the effort but I still don't get why it would say the glove vanes allow 7.5g.

 

Ok, let us try to understand what glove vanes do, besides the simple fact that they add extra lift. (But then I am really off to bed! )

First we need to understand what mach tuck and trim drag are. But let us get a bit more basic than this first, to have a better understanding of it. Btw, I asked Fat Creason to explain it to me again, because, you see, not even I dare to make assumptions shooting from my hip in such matters, as I have not studied this. He has, and he has worked with this stuff all his professional life. It is important to verify such things with ppl, who understand it much much more in depth than we do. Never dismiss the input from a real subject matter expert.

How an aircraft performs is mostly defined by how much lift it can generate and how much drag it has. AOA is a primary driver for both lift and drag. The more lift, the more "upward" force available (and therefore G available), the more drag it gets decreases ability to maintain speed or ability to accelerate. The ability to increase AOA (and therefore lift/G) comes from the elevators in the rear of the F-14, which will "pick up" the nose and increase AOA. However, the elevators are pretty large and at large deflections they add drag.

What is AOA? AOA is the difference between where you're (nose is) pointed (at) and where you're going, or the direction of incoming wind relative to the nose, if you like.

 

Now, understanding this, we can take a look at what happens at speeds above Mach 1.2 - M 1.4. Each aircraft has a center of lift and a center of gravity. When you go faster than Mach 1.2 - 1.4, your center of lift moves aft. But your center of gravity stays the same, out in front of the center of lift. This causes a small problem: when the lift moves aft, you get a nose down moment, which is known as mach tuck.

You can counter this by increasing stab deflection in the back to "pick up" the nose, but doing so adds drag and decreases lift (which is known as trim drag). Another way to solve this is to add lift near the front of the aircraft (like glove vanes, which are kind of canards that don't move), which simultaneously picks up the nose (increases AOA) and adds lift at the same time. Another side effect is that you don't need as much elevator deflection in the back, which decreases the drag caused from elevator deflection. Because there is less elevator needed to keep the nose up due to the glove vanes "helping out", theoretically there is more elevator travel available to further increase "G available" at these higher speeds. So this is what the glove vanes are for. They counter mach tuck and the resulting trim drag.

This also helps with pulling Gs as mentioned. Lift allows you to pull Gs in the first place, hence extra lift (glove vanes) allow you to pull extra Gs. In return they also allow for more stab travel (at these higher speeds) as you didn't need to use it all trying to trim additional nose up.

Adding extra G to the airplane is all about getting your AOA higher (aka adding lift, wich is almost 100% a function of AOA). And you can get your pitch moment higher from the stabs and/ or glove vanes, or canards like in the Viggen.

However, at the end of the day it became apparent that the benefits of the glove vanes were outweighed by their maintenance burden so they were welded shut and deleted from later F-14 production runs.

I hope this helps you understand the glove vanes better. As you can see, they have nothing to do with a G-limiter. Please simply trust us: the Tomcat did not have any kind of g-limiter.

Good night!

PS: maybe to add a line how Gs and lift are related: If my aircraft weights 1 lb and I'm generating 1.5 lb of lift, my current G load is 1.5G.

Controlling the F-14 in pitch goes like this:

Pilot pulls stick aft > elevator deflects more > nose goes up > AOA increases > more lift from AOA > more lift = higher G > pilot reacts to G or pitch angle > Pilot changes stick input

-> Elevator is directly related to stick position. Elevator will give as much G as the pilot can pull.

On a G-limiter type system like the F-16 (first jet to have one in the mid 70s):

Pilot feels G or wants pitch to change > pilot pulls stick > stick commands G > system decides if G is safe to command (the automatic limiter part) > system moves elevator to push nose up, increasing AOA/lift, with a controller closing on commanded G.

-> Elevator is being modulated by a computer to set a desired lift amount/G, within safe limits.

Edited June 18, 2021 by IronMike

[GGTharos]

Just now, Mistang said:

If we're taking about a new build tomcat in 2021 flying to Siberia to dogfight a PAK, sure. But in real life these aircraft are completely depreciated and die at 6g.

 

No, they don't.  Stop making things up and changing the subject.  This is really simple:  The 6.5g limit in NATOPS is not considered to be the limit of the airframe capability due to other sources.  In other words, it's now on you to refute this with documentation, not making stuff up about new tomcats, glove vanes, engineers or anything else.

[Cab]

2 minutes ago, Mistang said:

If we're taking about a new build tomcat in 2021 flying to Siberia to dogfight a PAK, sure. But in real life these aircraft are completely depreciated and die at 6g.

The only F-14s flying these days are in Iran.

 

They are pretty old.

 

[maxsin72]

49 minutes ago, Mistang said:

That's different because the eagle simply has a limiter.

 

Anyway whatever I appreciate the effort but I still don't get why it would say the glove vanes allow 7.5g.

I think you need to read the attachment

v002t02a001-82-gt-5.pdf

Edited June 17, 2021 by maxsin72

[Mistang]

5 minutes ago, maxsin72 said:

I think you need to read the attachment

v002t02a001-82-gt-5.pdf 1.65 MB · 9 downloads

 

Great pdf, thanks.  I know the compressor stall is mainly related to aoa. But sustaining a turn requires aoa so it's the same problem. 

[maxsin72]

8 minutes ago, Mistang said:

Great pdf, thanks.  I know the compressor stall is mainly related to aoa. But sustaining a turn requires aoa so it's the same problem. 

I also hope it is clear that gloves help really much F14 tu pull high G at supersonic speed

[G.J.S]

And (because I just can’t . . . ), the glove vanes - pretty sure they were to destabilise the aircraft as at Mach speeds the aircraft is a little too stable in pitch, thereby hindering pitch authority.

They could also be selected “out” whilst in “bomb” mode by the pilot, as at subsonic speeds they also acted to stabilise the aircraft a little.

 

Maybe @Victory205 can come in on this regards the vanes? Although, to be honest, I doubt he would want to be having to deal with this amount of sh1t.

 

Also, the G limit thing being a hard limit, passed by no one? . . . The F-4 (sorry IronMike eta al) was limited to 6 positive. I’ve seen 10 transient, and sustained 7 through a little more than half a turn with no ill effects, and no really long downtime as a result. Tornado is a 6.5 bird, and again can and did do more, it’s just with the installed thrust, it wouldn’t be turning with anybody really - more of a hit’n’run mentality.

Edited June 18, 2021 by G.J.S
Was the preceding picture too much?

[Mistang]

2 minutes ago, G.J.S said:

And (because I just can’t . . . ), the glove vanes - pretty sure they were to destabilise the aircraft as at Mach speeds the aircraft is a little too stable in pitch, thereby hindering pitch authority.

They could also be selected “out” whilst in “bomb” mode by the pilot, as at subsonic speeds they also acted to stabilise the aircraft a little.

 

Maybe @Victory205 can come in on this regards the vanes? Although, to be honest, I doubt he would want to be having to deal with this amount of sh1t.

 

Also, the G limit thing being a hard limit, passed by no one? . . . The F-4 (sorry IronMike eta al) was limited to 6 positive. I’ve seen 10 transient, and sustained 7 through a little more than half a turn with no I’ll effects, and no really long downtime as a result. Tornado is a 6.5 bird, and again can and did do more, it’s just with the installed thrust, it wouldn’t be turning with anybody really - more of a hit’n’run mentality.

Tornado has basically the same t/w and loading as the cat. 

[Frosty2124]

Just now, Mistang said:

Tornado has basically the same t/w and loading as the cat. 

go on, which tornado

[G.J.S]

Just now, Mistang said:

Tornado has basically the same t/w and loading as the cat. 

Ask me about the Tonka, I had a few years in it.

 

F-14 and Tornado are not in the same league. They both have VG wings, but that’s where the similarity ends.

5 minutes ago, Frosty2124 said:

go on, which tornado

I think he’s thinking about the ones that lift freight trains and levels homes in the American Midwest?

[Mistang]

Just now, Frosty2124 said:

go on, which tornado

https://en.m.wikipedia.org/wiki/Panavia_Tornado
 

• Wing area: 26.6 m² (286 sq ft)
   
• Empty weight: 13,890 kg (30,622 lb) ^[358]

that's 105 lb per ft.

 

 

• Powerplant: 2 × Turbo-Union RB199-34R Mk 103 afterburning 3-spool turbofan, 43.8 kN (9,800 lbf) thrust each dry, 76.8 kN (17,300 lbf) with afterburner

 

https://en.m.wikipedia.org/wiki/Grumman_F-14_Tomcat#Variable-geometry_wings_and_aerodynamic_design

 

 

Wing area: 565 sq ft (52.5 m²) wings only

• Empty weight: 43,735 lb (19,838 kg)
   

78 lbs per ft.

Powerplant: 2 × General Electric F110-GE-400 afterburning turbofans, 16,610 lbf (73.9 kN) thrust each dry, 28,200 lbf (125 kN) with afterburner

 

tw is 1.3 tomcat vs 1.1 tornado. .74 vs .67 dry.

 

So it should be at best like a 20% difference.

 

[Frosty2124]

Just now, Mistang said:

https://en.m.wikipedia.org/wiki/Panavia_Tornado
 

• Wing area: 26.6 m² (286 sq ft)
   
• Empty weight: 13,890 kg (30,622 lb) ^[358]

that's 105 lb per ft.

 

 

• Powerplant: 2 × Turbo-Union RB199-34R Mk 103 afterburning 3-spool turbofan, 43.8 kN (9,800 lbf) thrust each dry, 76.8 kN (17,300 lbf) with afterburner

 

https://en.m.wikipedia.org/wiki/Grumman_F-14_Tomcat#Variable-geometry_wings_and_aerodynamic_design

 

 

Wing area: 565 sq ft (52.5 m²) wings only

• Empty weight: 43,735 lb (19,838 kg)
   

78 lbs per ft.

Powerplant: 2 × General Electric F110-GE-400 afterburning turbofans, 16,610 lbf (73.9 kN) thrust each dry, 28,200 lbf (125 kN) with afterburner

 

tw is 1.3 tomcat vs 1.1 tornado. .74 vs .67 dry.

 

So it should be at best like a 20% difference.

 

that's not how wing loading works, that's not how wing loading works at all

 

also, wikipedia

[Mistang]

Just now, Frosty2124 said:

that's not how wing loading works, that's not how wing loading works at all

 

also, wikipedia

Ok sure. I'll take whatever you give.

[G.J.S]

Stop being a Wikipedia-Warrior.

 

That is a public resource, edited by the public, and monitored for accuracy by no one.

[Mistang]

Just now, G.J.S said:

Stop being a Wikipedia-Warrior.

 

That is a public resource, edited by the public, and monitored for accuracy by no one.

So is dcs. 

[Frosty2124]

1 minute ago, Mistang said:

Ok sure. I'll take whatever you give.

mate, i've tried being helpful but you wouldn't listen, its time to learn to you you're own research. come back to us with the correct answers

[IronMike]

2 minutes ago, Mistang said:

So is dcs. 

 

Not true, DCS is anything but a public resource (far from it, we will never be able to share everything with you), and it is not edited by the public, but by professionals, and it is being monitored for accuracy by a plethora of ppl, not the least including SMEs.

He is trying to help you, you know. He is someone with first hand experience. Personally, when in presence of SMEs, I define my sole job as "listening" and "asking the right questions". Just a word of advice.

Edited June 18, 2021 by IronMike

[Mistang]

2 minutes ago, IronMike said:

 

Not true, DCS is anything but a public resource (far from it, we will never be able to share everything with you), and it is not edited by the public, but by professionals, and it is being monitored for accuracy by a plethora of ppl, not the least including SMEs.

He is trying to help you, you know. He is someone with first hand experience. Personally, when in presence of SMEs, I define my sole job as "listening" and "asking the right questions". Just a word of advice.

 

I don't see SMEs besides that one implausible anecdote from okie.

 

Heatblur is Swedish. He's not a tomcat pilot. 

[Frosty2124]

Just now, Mistang said:

I don't see SMEs besides that one implausible anecdote from okie.

 

Heatblur is Swedish. He's not a tomcat pilot. 

heatblur ain't a person

 

G.J.S is a tonka SME

 

I am a Typhoon SME

 

even tho we don't know the cat aswell as some. we know aviation

 

 

there are ex USN lads in here who are Tomcat SME's

 

when Creason or iron mike open their mouths about the cat WE Listen

 

god gave you 2 ears and one mouth, i suggest you use em in that order