PSA: F-14 Performance/FM Development Status + Guided Discussion

[Noctrach]

17 minutes ago, Baz000 said:

Man! "it depends" is the typical fighter pilot answer lol

Honestly, I do disagree with you... If you turn it around and say it is a dive... Who gets to the ground faster and gets there first? I think the same principle applies but in reverse for a climb.

Then all you have to do is somehow prove that thrust-to-weight is decidedly not equal.

In a purely ballistic trajectory with negligible difference in drag, mass doesn't contribute to the result, since the following is true according to the laws of energy conservation:

Kinetic energy at the start = ½ m*v_initial²
Potential energy at the apex = m*g*h_apex

This leads us to:

m*g*h_apex = ½ m*v_initial²
h_apex = m*v_initial² / 2*m*g
h_apex = v_initial² / 2g
since v_initial and g are the same for both aircraft, h_apex will be identical.

The only difference here is thrust, so you'd need to prove that thrust-to-weight is significantly different based on the thrust-to-drag needed to attain a steady-state formation.

As @Katjhelped demonstrate, this means you need to determine the impact of AoA on the thrust setting and energy bleed of both aircraft. This in turn is heavily dependent on the L/D curve.

The impact of AoA will be more severe on the heavier aircraft during the turn, but it will also reduce drag more significantly as it approaches 0 in the vertical part of the climb. Applying the KISS principle I would say: "all things considered, thrust/lift/drag will roughly cancel out in linear fashion". Therefore, we can assume thrust required to attain the same starting speed scales roughly linearly with weight. This would mean thrust-to-drag = thrust-to-weight = equal, in which case both aircraft would reach the same altitude.

Not entirely true for real life, so therefore the real answer becomes "it depends".

 

Bottom line, you cannot easily simplify this, nor test this by just taking two aircraft at the same speed and pulling vertical.

[Baz000]

Because of the same reason that two identical aircraft with one having more of an internal fuel load than the other, given the same exact parameters as Victory205 stated would have one overshoot the other if they were in a dive rather than a climb.

If you fly in formation with someone in DCS and they are your wingman and they have significantly more fuel than you and you chop your throttles to idle and open your speedbrakes... And he does the same at the exact same time as you, he still will overshoot you and pass you because he has way more inertia to have to kill on his plane than you did.

The heavier aircraft does not accelerate nor decelerate like the other aircraft does, there is a difference between the two of them perhaps only marginal and perhaps not and it is significant?

So, how could the inverse not be true when in a climb?

lets say one Tomcat has 10,000 lbs internal fuel and the other has 12,000 lbs (that should be 20% difference in internal fuel) who will travel faster in a dive? And who would hit the ground or the hard deck first?

Thrust to weight is different lol... How can it not be different when one aircraft has a 20% difference in weight?

What has more thrust to weight? A F-14 or a A-4 Skyhawk?

Edited October 29, 2021 by Baz000

[Noctrach]

8 minutes ago, Baz000 said:

Because of the same reason that two identical aircraft with one having more of an internal fuel load than the other, given the same exact parameters as Victory205 stated would have one overshoot the other if they were in a dive rather than a climb.

So does this tell you physics is wrong, or that the dive scenario is not equal to the climb scenario

Bit of a straw-man obviously, but I urge you to write it out for yourself with all forces involved and see where it gets you. I stand ready to be corrected.

Edited October 29, 2021 by Noctrach

[Baz000]

It tells me the same exact physics applies to a dive as does a climb they are merely the inverse of one another.

Much like for example the concept of the "energy egg"

In the case he used as a theoretical example, he stated one plane is 20% heavier than the other... He practically told all of us right there that they have different thrust to weight ratio.

[draconus]

37 minutes ago, Baz000 said:

In the case he used as a theoretical example, he stated one plane is 20% heavier than the other... He practically told all of us right there that they have different thrust to weight ratio.

Might it clear up for you that Noctrach use T in T/W ratio as actual thrust, not the max thrust used commonly for theoretical aircraft performance?

[Katj]

Then all you have to do is somehow prove that thrust-to-weight is decidedly not equal.
In a purely ballistic trajectory with negligible difference in drag, mass doesn't contribute to the result, since the following is true according to the laws of energy conservation:
Kinetic energy at the start = ½ m*v_initial²
Potential energy at the apex = m*g*h_apex
This leads us to:
m*g*h_apex = ½ m*v_initial²
h_apex = m*v_initial² / 2*m*g
h_apex = v_initial² / 2g
since v_initial and g are the same for both aircraft, h_apex will be identical.
The only difference here is thrust, so you'd need to prove that thrust-to-weight is significantly different based on the thrust-to-drag needed to attain a steady-state formation.
As @Katjhelped demonstrate, this means you need to determine the impact of AoA on the thrust setting and energy bleed of both aircraft. This in turn is heavily dependent on the L/D curve.
The impact of AoA will be more severe on the heavier aircraft during the turn, but it will also reduce drag more significantly as it approaches 0 in the vertical part of the climb. Applying the KISS principle I would say: "all things considered, thrust/lift/drag will roughly cancel out in linear fashion". Therefore, we can assume thrust required to attain the same starting speed scales roughly linearly with weight. This would mean thrust-to-drag = thrust-to-weight = equal, in which case both aircraft would reach the same altitude.
Not entirely true for real life, so therefore the real answer becomes "it depends".
 
Bottom line, you cannot easily simplify this, nor test this by just taking two aircraft at the same speed and pulling vertical.

Well, realisticly, if you are in steady state flight and planning to go vertical without touching the throttles you're going to have a decent indicated airspeed and low AoA. Thus the lighter aircraft will "win".

[Victory205]

1 hour ago, Baz000 said:

What has more thrust to weight? A F-14 or a A-4 Skyhawk?

Interesting. 

[Jackjack171]

21 hours ago, maxsin72 said:

But it is risky in case of one engine failure so not possible for safety and in any case not possible at max weight.

 

It is not risky at all. If that were true, you'd have to explain the A-4 and A-7! Navy aircraft, including the F-14A launched just fine under mil power! I'm not a pilot, just an old Flight Deck Chief. As far as I can tell, it depended on what they were loaded out with. Don't trust everything that you find on the internet!

There is also footage of Tomcats being shot off of the Coral Sea on YouTube.

[Snappy]

In other news, world wide popcorn prices are spiking to unheard-of levels,  due to an unexplicable sudden surge in global demand..

Maybe it would be better if you guys just stated that you don't know the answer and we can return to the original topic.

Edited October 29, 2021 by Snappy

[maxsin72]

1 hour ago, Jackjack171 said:

It is not risky at all. If that were true, you'd have to explain the A-4 and A-7! Navy aircraft, including the F-14A launched just fine under mil power! I'm not a pilot, just an old Flight Deck Chief. As far as I can tell, it depended on what they were loaded out with. Don't trust everything that you find on the internet!

There is also footage of Tomcats being shot off of the Coral Sea on YouTube.

Please read the attached document, i think the data were provided by the Navy.

[IronMike]

1 hour ago, maxsin72 said:

Please read the attached document, i think the data were provided by the Navy.

Jackjack is a voice of the Navy, as he worked on a carrier deck for a living. There is no 1-answer to most things aviation. Most answers start with "it depends" - this is good to keep in mind when sourcing information. Especially with the Tomcat there is many contradicting stuff out there, which sometimes even amounts to just both being true, depending on various circumstances. Approaching the Tomcat with an ounce of "this is one piece of the puzzle only" mentality is very helpful to get the full picture in the end.

[maxsin72]

57 minutes ago, IronMike said:

Jackjack is a voice of the Navy, as he worked on a carrier deck for a living. There is no 1-answer to most things aviation. Most answers start with "it depends" - this is good to keep in mind when sourcing information. Especially with the Tomcat there is many contradicting stuff out there, which sometimes even amounts to just both being true, depending on various circumstances. Approaching the Tomcat with an ounce of "this is one piece of the puzzle only" mentality is very helpful to get the full picture in the end.

Ok, i have understood there is many contradicting stuff out there about the Tomcat and i trust mens who have real life experience

[Baz000]

https://www.grc.nasa.gov/www/k-12/airplane/climb.html

https://www.grc.nasa.gov/www/k-12/airplane/exthrst.html

https://www.grc.nasa.gov/www/k-12/airplane/fwrat.html

https://www.quora.com/What-is-a-thrust-to-weight-ratio-in-simple-terms

"Why We Care
If an engine produces more thrust than the vehicle weighs, it can overcome gravity and accelerate when pointed straight up. (Thrust overcomes weight, lifting it straight up from the Earth.)

If an engine produces less thrust than the vehicle weighs, the vehicle must rely on something else to overcome weight. This is usually from aerodynamic lift. (Thrust moves the vehicle forward, creating air flow. Air flowing over the wings creates lift, which helps... lift... the aircraft into the air, as long as there is enough lift to overcome the weight.)

Examples

• Saturn V rocket, Stage 1 = 94.1 (LOTS of thrust to put stuff in orbit)
• F-15 = 1.06 (with full thrusties on... a.k.a. afterburner, it can accelerate straight up. Without burner, uses aerodynamic lift.)
• A-10 = 0.49 (will decelerate fast if pointed straight up. Relies on aerodynamic lift to get and stay airborne.)"

Ask, and ye shall receive

Seek and ye shall find

Knock, and the door will be opened unto you

https://man.fas.org/dod-101/sys/ac/a-4.htm

https://man.fas.org/dod-101/sys/ac/f-14.htm

F-14A: 20,900 pounds (9,405 kg) static thrust per engine;

F-14B and F-14D: 27,000 pounds (12,150 kg) per engine

vs.

Single, Pratt & Whitney, J-52-P-408A non-afterburning, turbojet engine that develops 11,220 pounds of thrust on the A-4

F-14 maximum takeoff weight 72,900 pounds (32,805 kg)

F-14 maximum payload

Up to 13,000 pounds F-14 wingspan 64 feet (19 meters) unswept, 38 feet (11.4 meters) swept A-4 Maximum takeoff weight: 24,500 pounds A-4 Wingspan: 26 ft 6 in provided FAS is giving out correct numbers this means a single F-14B engine alone could theoretically provide the A-4 excess thrust at maximum takeoff weight to have in excess 2,500 pounds of thrust available. but the A-4 didn't have that, it had a Pratt & Whitney, J-52-P-408A non-afterburning, turbojet engine that develops 11,220 pounds of thrust. So it is at a deficit of approximately 13,000 pounds of thrust at maximum takeoff weight. the F-14 when empty weights about around 10,000 pounds less than 2 A-4s at maximum takeoff weight loading. the F-14 also has just under x3 the wingspan of the A-4 when unswept and still a larger wingspan when swept back   The majority of this discussion over the last 2 pages has revolved primarily around the aerodynamic lifting forces imparted on the wings predominately. But, the F-14 used several different simultaneously combined elements to generate it's incredible pitch rate and ability to climb (at least for 70s aircraft design) The sheer brute force thrust provided by x2 afterburning engines, the large wingspan, the lifting force of the "pancake" area and the large moving stabs which are larger than the wings on some plane designs. all of these come together like pieces of a puzzle, or if you like... Like the different parts of an orchestra playing a symphony of smacking other aircraft around dogfighting in the sky. If you don't think the F-14 could dogfight effectively in the right skilled hands, then you don't know the F-14 .really. So, again... Let's ask the question 2 F-14s go into a zoom everything is identical except one is 20% heavier... Who will zoom faster? And who will zoom the highest? If they start together in formation at whatever engine power setting they were both stabilized in formation with (hint, they aren't at the same engine RPMs, one has more than the other) and they both used the same pull and hold the same pitch in the climb. Maybe this is some kind of USNTPS joke, like a version of which came first... The Chicken or the Egg? We haven't really even started to talk about the meat and potatoes of "thrust to weight" or "wing loading"  Why can't a T-38 win a fight starting dead on the 6 of a F-14, F-14 in a completely defensive situation?... If the F-14 breaks hard into him, levels his wings and plugs the burners in and pitches up into a climb. The T-38 can't follow him into the zoom, why? Same reason why one F-14 will zoom faster and higher than the other in our original question. Someone has more E than the other, despite being in identical airframes. I use the T-38 situation as an example to highlight the difference in energy available vs maneuverability capabilities at said energy state. (Granted they have different airframes and thus lift generated by the wings) But the T-38 is way way lighter than a F-14! So why'd the T-38 not be able to follow the zoom? When you understand the principal of why this ^^ you will understand how to answer Victory205's original question using the same airframes. To further solidify my point, the F-14 maximum takeoff weight is 72,900 pounds are the wings on the F-14 when fully extended forwards generating at least a minimum 72,900 pounds of lifting force? Or are there more variables at play here? Even the new F-14 pilots were surprised by how the plane could perform.

Edited October 30, 2021 by Baz000

[maxsin72]

2 hours ago, Baz000 said:

 

Starting min 13:50, has F14 full flaps?

[Baz000]

8 minutes ago, maxsin72 said:

Starting min 13:50, has F14 full flaps?

Honestly, I can't tell... I'm guessing you are wondering how he is reversing his turn so quickly to attack the F-4?

Really interesting touch and go landing only on the rear wheels only at 16:08(doesn't look like any float in ground effect or excessive "ballooning" in the climb for the go around... Looks like he is just flying to hold AOA in the climb prior to the turn)

Takeoff at full flaps at 12:45 look how nice and smoothly the plane gracefully gets into the air, again... No massive ballooning tendency pitching the nose up.

I don't know what these planes carry as internal fuel loads... Clearly, they are clean jets with nothing externally mounted. The best I'd guess is the fuselage tanks are full and internal wing tanks are empty.

Also notice the refueling probe covers are missing.

Edited October 30, 2021 by Baz000

[maxsin72]

6 minutes ago, Baz000 said:

Honestly, I can't tell... I'm guessing you are wondering how he is reversing his turn so quickly to attack the F-4?

Yes, you are right. Anyway, looking better at the video, probably F14 wasn't using full flaps.

[Baz000]

I'd imagine at best, maneuvering flaps as deployed automatically by the jet?(or manual override by the pilot)

If the Aux flaps are down too, then it isn't the maneuvering flaps... It is impressive how he turns like that to chase after the F-4(the F-4 can't make a turn like that F-14)

If you look at his stab movement on takeoff (assuming his stabs were positioned in the same position shown on the taxi scene just prior)

It looks like he just rotates the nose up and eases back pressure on the stick once positive rate is established. (You see the stabs deflect TEU and then TE stabs come down a bit as back stick is relaxed upon rotation but at no point do you see TE come down so far to a point that the LE shows up like as tho the pilot is jamming his stick forward and fighting the plane from climbing in a "ballooning" state.

I can't tell if he is in burners, I'd take an educated guess that in the interest of conserving fuel for the actual training, they are probably just in MIL.

I wish our bird in DCS could takeoff ashore so gracefully with full flaps, and do touch and goes like that, which looks so smooth... His nose wheel never even touches the ground. In DCS, I can't even land the Tomcat on just the mains without the nose coming to the ground immediately.

Edited October 30, 2021 by Baz000

[TLTeo]

1 hour ago, Baz000 said:

It is impressive how he turns like that to chase after the F-4

You see, the reason the Tomcat can turn that well is that it was designed purely as an interceptor, and they needed the turn performance so that stern conversions during intercept got done faster. That and only that

But yeah, it doesn't look like flaps (beyond maybe maneuvering?) are deployed to me. I think the lighter paint scheme can cause some confusion though.

Edited October 30, 2021 by TLTeo

[Baz000]

1 hour ago, TLTeo said:

You see, the reason the Tomcat can turn that well is that it was designed purely as an interceptor, and they needed the turn performance so that stern conversions during intercept got done faster. That and only that

But yeah, it doesn't look like flaps (beyond maybe maneuvering?) are deployed to me. I think the lighter paint scheme can cause some confusion though.

 

Yeah, I think it was maybe the paint too...

Well, you see the Tomcat supersonic interceptor airframe was designed to turn like that so it could give the Ruskie Bear bomber crews a good view of the Phoenix missiles loaded inside the tunnel. After performing such a "look under my belly" bat turn the Bear bomber tail gunner would answer in kind with a "look at her belly, comrade" playmate of the month centerfold picture in kind.

After both planes were finished with this interception dance, the supersonic interceptor Tomcat would return to the boat to then land at around 125-ish knots onto an area that only gave 2-1/2 feet of wing clearance if off centerline of the landing area and roughly 300 ft long... Stopping only when grabbing a 2 1/2 inch cable with a hook that was able to slow the plane down at maximum power to a dead stop.

Yeah, purely a supersonic belly flashing "look what I carry" interceptor indeed...

 

Here, learn something about the Tomcat here during a demo at a Miramar NAS airshow from the 80s listen to the Navy narrator of the demo flight and learn some things.

 

Edited October 30, 2021 by Baz000

[andyw248]

EDIT: Actually my below statement was wrong. These were actually F-14B's (or "F-14A+") - VF 101 received their A+ models in April 1988. But I'll leave the post up because the footage in that video is really an eye candy for F-14 lovers.

---

On the topic of F-14A's taking off at MIL power: I just came across an interesting video showing F-14's doing carrier qualification on USS Coral Sea in late '88 or early '89. As you can see, they are taking off without AB. Since this was carrier qualification their fuel load must have been within carrier landing limits, and as you can see they didn't carry any ordnance.

 

Edited October 30, 2021 by andyw248

[Baz000]

Are you sure those aren't A models? Because the engine exhaust shape doesn't look like Bs like we have in DCS.

[Victory205]

Good grief people, it isn’t rocket science. The A had a max gross weight for mil power cat shots, based on SE fly away for the existing conditions. Above that weight, you needed a burner shot.

The B didn’t use burner for cat shots due to additional thrust available at mil (roughly equal to zone 2 on an A), single engine control issues at typical end speeds, and cat interface depending again, on conditions, what ship, etc.

The B engines had a slightly worse SFC than the A, but not having to use burner for takeoff saved fuel overall for a typical flight.

[Baz000]

SE= single engine, right? When you say SE fly away

Not sure what SFC stands for tho -surface fuel consumption?

in addition didn't the B in AB also cause temp problems for the JBDs too?

The A didn't get an asymmetric thrust limiter, but that was introduced later with the B to prevent asymmetric AB light off, right?

Not being in AB for takeoff saves like a crap ton of fuel, right... Like 4x more fuel flow at AB than what is used at MIL

Edited October 30, 2021 by Baz000

[Raven (Elysian Angel)]

2 hours ago, Baz000 said:

Not sure what SFC stands for though -surface fuel consumption?

Specific fuel consumption, would be my guess.

[Baz000]

Oh, okay thanks much... Didn't know.