How is f-14 maneuverability?

[RaceFuel85]

During ODS Alphas actually had to plug into burner in order to maintain speed and angels when refueling due to the high altitude, thin air and hot conditions.

 

The A+'s didn't have that issue, obviously.

[turkeydriver]

For maneuvering and acceleration under G the TF-30s were not suited, but I'm pretty sure the TF-30 out performs the F-110 at high speed and altitude. Given you're rarely in those conditions, but the charts I looked at had the TF-30 above angels 30k and above Mach 1.4 maybe? start making more thrust and start walking away with more acceleration until the placard limit. I don't know how much testing time was devoted to getting the ramp scheduling set for max acceleration at altitude though for the F-110. I do know the B/D had the reputation for the best acceleration on the NTTR range during detachments- easily first jet to Mach 1.6(max speed at the range AFAIK). This is prior to the F-22 and Eurofighter coming on the scene. Feel free to shoot me down with science. I'm all about the F-110 being an actual fighter engine that performed better in 90% of the envelope, I'm pretty sure that the TF-30 took the altitude and speed numbers though.

[BlackLion213]

For maneuvering and acceleration under G the TF-30s were not suited, but I'm pretty sure the TF-30 out performs the F-110 at high speed and altitude. Given you're rarely in those conditions, but the charts I looked at had the TF-30 above angels 30k and above Mach 1.4 maybe? start making more thrust and start walking away with more acceleration until the placard limit. I don't know how much testing time was devoted to getting the ramp scheduling set for max acceleration at altitude though for the F-110. I do know the B/D had the reputation for the best acceleration on the NTTR range during detachments- easily first jet to Mach 1.6(max speed at the range AFAIK). This is prior to the F-22 and Eurofighter coming on the scene. Feel free to shoot me down with science. I'm all about the F-110 being an actual fighter engine that performed better in 90% of the envelope, I'm pretty sure that the TF-30 took the altitude and speed numbers though.

 

Yes, there were conditions where the TF30 was very powerful and capable, but fighters need to adapt to a wide variety of conditions and medium to high altitudes were not so good for the TF30.

 

Things were far from hopeless at high altitudes, Tomcats regularly cruised on cross-countries at 40,000'+. But the aircraft were generally clean and climbed to that altitude slowly. Thrust was also rather speed dependent: higher KIAS led to better engine response and thrust. At sea-level and mach 0.9, the TF30 pumped out 28,000 lbs of thrust (nearly as much as the F110 that makes 30,000 lbs under the same conditions).

 

It seems that the fundamental flaw in the TF30 design was a large fan unit/low pressure compressor that was not optimized compared to later designs (or perhaps the interface between the LP and HP compressors since porting the HP compressor stabilized airflow). Makes sense, the fundamental design dated to 1958 and fluid dynamics were MUCH better understood by the late-70s and early-80s when the advanced turbofans were entering service.

 

This inefficient LP compressor was heavy, so it would block airflow during rapid engine transients (accelerates slower due to its mass). It also was not nearly as good at delivering air to the high-pressure compressor as later designs. So during conditions where flight delivers a good stream of air (high speeds, dense air at low altitudes, or both) the engine was very powerful and dependable - especially in zone 5 burner. But create conditions where the stream was not so good: low airspeeds, high AOA, or very high altitudes - thrust suffered since the compressor was not delivering adequate airflow and stall would occur if things got bad enough. Hence high-altitude performance and thrust was not so good at medium to low airspeeds. But some conditions would give the TF30 a big boost while the F110 had little gains or losses from external conditions (a sign that the F110's compressor would deliver optimally irrespective of conditions).

 

Interestingly, the TF30 would rarely flame-out after a stall (perhaps a byproduct of all the modifications to improve stall margin), but the engine would instead fail to respond the throttle commands and eventually catch fire when TIT climbed enough (generally took about 30 seconds of a "hung-stall"). It generally had to be shutdown to clear a hung-stall.

 

Also, forcing the F-14A into a high-AOA flight regime would not only bleed airspeed due to high AOA drag, but also because it would open the mid-compression bypass valve of the TF30 and cost the engine another 15% of thrust (it opened between 11 and 16 units of AOA depending on speed). This improved stall margin at high AOA, but cost thrust. From what I've heard, pure AOA related stalls were uncommon unless airspeed was quite low (like 100 KIAS), but the beta movements caused by wing drop and yaw above 20 units AOA was a real concern.

 

Still, the F-14 didn't need high AOA to generate an excellent ITR (one of its virtues) and high AOA performance was also hindered by wing-drop and yaw - so high AOA was not necessarily the way to go for any F-14 model. Really the limiter for the F-14A was energy and effective energy management could keep it in the fight against any opponent. Its worth mentioning that exchange rates between F-14As and F-14B/Ds in training flights were actually fairly close (with F-14As routinely defeating F-14B/Ds in training flights). But there is no question that the F110 made the F-14 a much easier aircraft to use and much safer.

 

I have also heard that the TF30 Tomcats were "faster" - meaning they could break mach 2 easier. Above ~mach 1.8 the TF30 made more thrust.

 

However, the operational difference between the TF30 and F110 was even bigger than the numbers might suggest because the military power outputs at medium-high altitudes (where most fighters fly) was so much better.

 

-Nick

[Hummingbird]

Another neat thing the F110 engines made possible was that now the aircraft could take off from carriers on dry thrust alone, where'as the TF30 equipped cats had to go full afterburner - the latter not being particularly good if you didn't want to attract any unwanted attention at night.

[probad]

something's very wrong if you have unwelcome parties within visual range of a carrier.

[captain_dalan]

Ok guys, finished that second set of calculations, this time only at 35000ft (because i'm lazy) at mach 0.7 and 0.9. I looked at 2 cases for each, at Ps=0 (i.e. a sustained turn) and above (when possible close to Clmax.

 

At mach 0.7 F-14A still sustains better (about 2.25g) then the F-15C (about 1.9g). In a 3g break (close to Clmax for the F-15), the F-14A has a L/D about 3 times better, while the F-15C has a T/W about 2.2 times better, which still means, the F-15 will probably bleed faster.

 

At mach 0.9, the F-14A sustains about 2.2g and the F-15C about 2.5, clearly outperforming the Tomcat.In a 5.3g break (close to Clmax for the F-14A) the F-14A has L/D advantage of about 1.2 times and the F-15C has the T/W advantage of about 1.5 times. So the F-14A will bleed faster for the same turn. This is all in a horizontal fight of course.

 

In the context of that manual, i can see the tactics work in the case of the initial states for both AC at the high subsonic-transonic region, the F-15 initiating a break, making the F-14 bleed until about mach 0.75 - 0.80 or so and then hitting the vertical? However, pressing the horizontal bellow mach 0.8 seams like a bad idea as the F-14 will soon be able to sustain (and recover) much better, even this high up, as long as the engines don't die.

 

One final note, this high up, this entire fight is placed between 250 and 320 KIAS. So, the initial states won't last long either way.

 

Now what changes for the F-14 between mach 0.75 and 0.9? The only thing i can think of is the wing sweep (the T/W gets better of course). I wonder what would happen if the wings were set to 22-50 degrees sweep manually. Would that help the L/D enough to level the playing field a bit? I'd guess not.... after all at low alpha, the 68 degree sweep actually gives better L/D values.

 

Well, maybe someone else can do the math.

[Hummingbird]

something's very wrong if you have unwelcome parties within visual range of a carrier.

 

Visual range is quite far if you have jets lighting up the carrier though, I believe up to 40+ km. I remember it being discussed as a concern regarding enemy low level surprise attack runs which rely on visual contact, but it was no doubt a bigger concern then than it is now.

Edited June 2, 2017 by Hummingbird

[captain_dalan]

Visual range is quite far if you have jets lighting up the carrier though, I believe up to 40+ km. I remember it being discussed as a concern regarding enemy low level surprise attack runs which rely on visual contact, but it was no doubt a bigger concern then than it is now.

 

Yeah, the increased visibility/detectability during night launches cannot be over stressed. Especially in the middle of the ocean.

[Buzzles]

That's not going to really matter for multiplayer DCS missions though :)

[turkeydriver]

Yes, there were conditions where the TF30 was very powerful and capable, but fighters need to adapt to a wide variety of conditions and medium to high altitudes were not so good for the TF30.

 

Things were far from hopeless at high altitudes, Tomcats regularly cruised on cross-countries at 40,000'+. But the aircraft were generally clean and climbed to that altitude slowly. Thrust was also rather speed dependent: higher KIAS led to better engine response and thrust. At sea-level and mach 0.9, the TF30 pumped out 28,000 lbs of thrust (nearly as much as the F110 that makes 30,000 lbs under the same conditions).

 

It seems that the fundamental flaw in the TF30 design was a large fan unit/low pressure compressor that was not optimized compared to later designs (or perhaps the interface between the LP and HP compressors since porting the HP compressor stabilized airflow). Makes sense, the fundamental design dated to 1958 and fluid dynamics were MUCH better understood by the late-70s and early-80s when the advanced turbofans were entering service.

 

This inefficient LP compressor was heavy, so it would block airflow during rapid engine transients (accelerates slower due to its mass). It also was not nearly as good at delivering air to the high-pressure compressor as later designs. So during conditions where flight delivers a good stream of air (high speeds, dense air at low altitudes, or both) the engine was very powerful and dependable - especially in zone 5 burner. But create conditions where the stream was not so good: low airspeeds, high AOA, or very high altitudes - thrust suffered since the compressor was not delivering adequate airflow and stall would occur if things got bad enough. Hence high-altitude performance and thrust was not so good at medium to low airspeeds. But some conditions would give the TF30 a big boost while the F110 had little gains or losses from external conditions (a sign that the F110's compressor would deliver optimally irrespective of conditions).

 

Interestingly, the TF30 would rarely flame-out after a stall (perhaps a byproduct of all the modifications to improve stall margin), but the engine would instead fail to respond the throttle commands and eventually catch fire when TIT climbed enough (generally took about 30 seconds of a "hung-stall"). It generally had to be shutdown to clear a hung-stall.

 

Also, forcing the F-14A into a high-AOA flight regime would not only bleed airspeed due to high AOA drag, but also because it would open the mid-compression bypass valve of the TF30 and cost the engine another 15% of thrust (it opened between 11 and 16 units of AOA depending on speed). This improved stall margin at high AOA, but cost thrust. From what I've heard, pure AOA related stalls were uncommon unless airspeed was quite low (like 100 KIAS), but the beta movements caused by wing drop and yaw above 20 units AOA was a real concern.

 

Still, the F-14 didn't need high AOA to generate an excellent ITR (one of its virtues) and high AOA performance was also hindered by wing-drop and yaw - so high AOA was not necessarily the way to go for any F-14 model. Really the limiter for the F-14A was energy and effective energy management could keep it in the fight against any opponent. Its worth mentioning that exchange rates between F-14As and F-14B/Ds in training flights were actually fairly close (with F-14As routinely defeating F-14B/Ds in training flights). But there is no question that the F110 made the F-14 a much easier aircraft to use and much safer.

 

I have also heard that the TF30 Tomcats were "faster" - meaning they could break mach 2 easier. Above ~mach 1.8 the TF30 made more thrust.

 

However, the operational difference between the TF30 and F110 was even bigger than the numbers might suggest because the military power outputs at medium-high altitudes (where most fighters fly) was so much better.

 

-Nick

Thanks Nick- great read!

[turkeydriver]

Ok guys, finished that second set of calculations, this time only at 35000ft (because i'm lazy) at mach 0.7 and 0.9. I looked at 2 cases for each, at Ps=0 (i.e. a sustained turn) and above (when possible close to Clmax.

 

At mach 0.7 F-14A still sustains better (about 2.25g) then the F-15C (about 1.9g). In a 3g break (close to Clmax for the F-15), the F-14A has a L/D about 3 times better, while the F-15C has a T/W about 2.2 times better, which still means, the F-15 will probably bleed faster.

 

At mach 0.9, the F-14A sustains about 2.2g and the F-15C about 2.5, clearly outperforming the Tomcat.In a 5.3g break (close to Clmax for the F-14A) the F-14A has L/D advantage of about 1.2 times and the F-15C has the T/W advantage of about 1.5 times. So the F-14A will bleed faster for the same turn. This is all in a horizontal fight of course.

 

In the context of that manual, i can see the tactics work in the case of the initial states for both AC at the high subsonic-transonic region, the F-15 initiating a break, making the F-14 bleed until about mach 0.75 - 0.80 or so and then hitting the vertical? However, pressing the horizontal bellow mach 0.8 seams like a bad idea as the F-14 will soon be able to sustain (and recover) much better, even this high up, as long as the engines don't die.

 

One final note, this high up, this entire fight is placed between 250 and 320 KIAS. So, the initial states won't last long either way.

 

Now what changes for the F-14 between mach 0.75 and 0.9? The only thing i can think of is the wing sweep (the T/W gets better of course). I wonder what would happen if the wings were set to 22-50 degrees sweep manually. Would that help the L/D enough to level the playing field a bit? I'd guess not.... after all at low alpha, the 68 degree sweep actually gives better L/D values.

 

Well, maybe someone else can do the math.

 

Great analysis!!!

[probad]

Visual range is quite far if you have jets lighting up the carrier though, I believe up to 40+ km. I remember it being discussed as a concern regarding enemy low level surprise attack runs which rely on visual contact, but it was no doubt a bigger concern then than it is now.

 

discussed by whom? more people trying to pull reasons out of their rear end for the sake of making things sound good?

 

bugs are somehow okay with using abs on shots, and everyone still lights the blowers on landing. if it was even half as significant as you'd like it to sound you'd think there'd be some major requirement changes to aircraft design, but there aren't.

 

when billions are spent on an aircraft with a 200nm+ standoff radius plus escorts, not to mention the costs of the training and procedures to make it all work, either the united states is really stupid or you're really reaching if it all comes down to <1minute windows of eyeballing the carrier at 20nm.

Edited June 2, 2017 by probad

[captain_dalan]

Great analysis!!!

 

Thanks mate! :thumbup:

[BlackLion213]

everyone still lights the blowers on landing.

 

They certainly lose a lot of style points for this and it is not actually that common. Navy fighters see little to no benefit to lighting the burners in terms of wave-off performance (at least for the F-14 there is no real difference). I suspect these blower landings are pilots who hit the deck having corrected a high ball and touched down at lower RPM than normal. They get get nervous and push into the AB detent. Not normal procedure and generally a sign that something went wrong.

 

bugs are somehow okay with using abs on shots, and everyone still lights the blowers on landing. if it was even half as significant as you'd like it to sound you'd think there'd be some major requirement changes to aircraft design, but there aren't.

 

I don't think anyone said it was a design requirement, but it is a desirable trait. If the USN didn't care about light discipline, they wouldn't operate at night with three small lights on the boat or use red ambient lighting on deck (though this may have changed in the 2000s). It is not ideal that an enemy would be so nearby undetected or undeterred, but it would also suck if you then painted your position for all to see when they may have passed you by without notice. If the Navy didn't care, the carrier would be brightly lit to improve aviation safety, controlling light emissions is important just like controlling electronic emissions.

 

So if the Navy can launch an aircraft without using the burners, it will and it prefers it that way (which Hornets often do BTW along and F-14As did under GW of 60,000 lbs). But if it needs the burners for a safe launch, it will do what is needed.

 

If it is raining outside, you still go to work right? Better to have an umbrella, but the lack of it won't stop you - helpful, but not mandatory.

 

The real benefit of the F110 was the reliability and thrust; the other stuff was just "nice" and helped justify the program to budget oversight. Even the fuel economy stuff proved to be a wash. The F110 powered Tomcats got off the cat with another 500-600 lbs of fuel because they didn't need burner, but burned another 100-200 lbs/hour on station. Though fuel economy would be more noticeable during ACM due to the better thrust-specific consumption in burner.

 

Plus the F-14B/D was notable for NOT being able to launch in burner. The JBDs couldn't take it. There is actually a special procedure for testing installed F110s on the deck by individually staging up each engine and holding for 15-30 seconds with at least a 30 second cool down for the JBD between runs. The Hornet need not worry about this because...well....you know (yes - I am suggestively flexing my small finger as I write this). :P

 

-Nick

[BlackLion213]

Great analysis!!!

 

I second! :)

 

Thank you for doing the math Captain Dalan - very helpful! :thumbup:

 

-Nick

[Hummingbird]

Beat me to it BlackLion213, but yes ofcourse light discipline is important as you can't always guarantee that an enemy doesn't slip by your sensors and it would be foolish to just presume so. The Navy has to be preemptive in that respect.

 

The afterburners could afterall be seen from over 40 miles (not km) away, just checked up on that. So depending on who you expected could be watching, which in turn depends on the area in which you operate, then launches would be without burners if possible AFAIK. Been a long time since I talked to an acquaintance of mine who flew for the Navy during the 80's, but that's vaguely what I remember him telling me. How things are today I have no clue, but I'd imagine the same rules apply.

Edited June 3, 2017 by Hummingbird

[FWind]

They certainly lose a lot of style points for this and it is not actually that common. Navy fighters see little to no benefit to lighting the burners in terms of wave-off performance (at least for the F-14 there is no real difference). I suspect these blower landings are pilots who hit the deck having corrected a high ball and touched down at lower RPM than normal. They get get nervous and push into the AB detent. Not normal procedure and generally a sign that something went wrong.

 

 

 

I don't think anyone said it was a design requirement, but it is a desirable trait. If the USN didn't care about light discipline, they wouldn't operate at night with three small lights on the boat or use red ambient lighting on deck (though this may have changed in the 2000s). It is not ideal that an enemy would be so nearby undetected or undeterred, but it would also suck if you then painted your position for all to see when they may have passed you by without notice. If the Navy didn't care, the carrier would be brightly lit to improve aviation safety, controlling light emissions is important just like controlling electronic emissions.

 

So if the Navy can launch an aircraft without using the burners, it will and it prefers it that way (which Hornets often do BTW along and F-14As did under GW of 60,000 lbs). But if it needs the burners for a safe launch, it will do what is needed.

 

If it is raining outside, you still go to work right? Better to have an umbrella, but the lack of it won't stop you - helpful, but not mandatory.

 

The real benefit of the F110 was the reliability and thrust; the other stuff was just "nice" and helped justify the program to budget oversight. Even the fuel economy stuff proved to be a wash. The F110 powered Tomcats got off the cat with another 500-600 lbs of fuel because they didn't need burner, but burned another 100-200 lbs/hour on station. Though fuel economy would be more noticeable during ACM due to the better thrust-specific consumption in burner.

 

Plus the F-14B/D was notable for NOT being able to launch in burner. The JBDs couldn't take it. There is actually a special procedure for testing installed F110s on the deck by individually staging up each engine and holding for 15-30 seconds with at least a 30 second cool down for the JBD between runs. The Hornet need not worry about this because...well....you know (yes - I am suggestively flexing my small finger as I write this). :P

 

-Nick

 

JBD？？？

[Emmy]

Fascinating discussion gents...

 

Thank You to those brining solid intel and first-hand knowledge to bear.

[punk]

JBD？？？

 

Jet Blast Deflectors if that is what you are asking. They raise up behind the aircraft taking off so people, aircraft and equipment behind them don't get toasted and/or blown backwards when the engines rev up.

 

<Salute>

Punk

[captain_dalan]

I second! :)

 

Thank you for doing the math Captain Dalan - very helpful! :thumbup:

 

-Nick

 

Always a pleasure mate! :pilotfly:

[FWind]

Jet Blast Deflectors if that is what you are asking. They raise up behind the aircraft taking off so people, aircraft and equipment behind them don't get toasted and/or blown backwards when the engines rev up.

 

<Salute>

Punk

 

Thanks :thumbup:

 

-Nick

[FNU LNU]

I only have moderate knowledge of the Tomcat, but I had a crashpad roommate a few years ago who was a Tomcat driver and we used to talk about the jet all the time. He said that in most cases, the D was prohibited from launching in AB because the higher thrust engines increased Vmca to an airspeed where rudder authority was insufficient to compensate for an engine failure during the cat stroke. Hence MIL thrust takeoffs.

 

He never mentioned an explicit Vmca value - and I never asked - but he did say they could push it to AB once the jet was climbing away. I don't know whether the same restriction existed on the B.

 

What is a typical cat end speed for a B/D, anyway?

[BlackLion213]

I only have moderate knowledge of the Tomcat, but I had a crashpad roommate a few years ago who was a Tomcat driver and we used to talk about the jet all the time. He said that in most cases, the D was prohibited from launching in AB because the higher thrust engines increased Vmca to an airspeed where rudder authority was insufficient to compensate for an engine failure during the cat stroke. Hence MIL thrust takeoffs.

 

Yeah, the rudder authority was an issue too, especially for shore operations. From my readings, there were 3 factors that compelled the USN to require mil-thrust-only cat-shots for the F110:

 

- The burners would over-heat the JBDs and lead to failures (internal plumbing failures iirc)

- As you said, the Vmca was climbed a fair bit (I think to 170-180 KIAS, I need to check my references).

- The aircraft could easily overspeed the gear doors unless pilots were very prompt in commanding gear up on shore take-offs. Also true during carrier ops, pilots would usually retract the gear before selecting AB with the F110s. As you can see here:

 

He never mentioned an explicit Vmca value - and I never asked - but he did say they could push it to AB once the jet was climbing away. I don't know whether the same restriction existed on the B.

 

What is a typical cat end speed for a B/D, anyway?

 

It was the same for both the B and D, I think around 170-180 KIAS, but I should double check that. I have the F-14D NATOPS around here somewhere....

 

-Nick

[Top Jockey]

VERY good article of Caesar's from CombatACE:

 

http://combatace.com/blog/5/entry-89-knight-syndrome-and-the-f-14-tomcat/

 

Says tons about F-14's maneuverability.

[Robert31178]

Jockey, real good read!! Thank you for posting.

 

~Rob