F-14 Questions Answered - Ask Away

[Astro14]

RichardH - It's been 18 years now since I last flew the big fighter...and I'm on the road...so, we're going to have to press on with only memory on this...when I'm next home, I'll see if I can't drag out the old NATOPS for the F-14A and see if I've got the numbers correct...

First, a bit of history...

DLC was installed in the F-14A due to the slow engine response of the TF-30. It was the result of test pilot critique of the airplane's carrier landing handling qualities. To compensate for slow spool up time (which led to adding too much power and going high, or led to too great a power reduction in response to being high), DLC was designed to control lift directly, so that glideslope could be controlled directly with DLC and not with thrust.

Great in theory.

Somewhat different in practice...

In the F-14A, engaging DLC (depress stick button with landing flaps selected) put all 4 spoilers to an intermediate position (11 degrees...I think...). You still flew the "donut". You still flew on-speed. However, with DLC engaged, on speed was now 6 knots faster than when clean due to disturbed flow over the wing...

Forward thumbwheel (down) deployed all 4 spoilers to 17 degrees (again...I think), which added drag and spoiled a bit of lift to bring the airplane down. Aft thumbwheel retracted the spoilers, reducing drag and cleaning up the wing. Spoiler response to thumbwheel response was linear...a bit of thumbwheel told the roll computer to put out a bit of spoilers...

But the effects on the airplane of UP DLC were not rapid enough to correct a low/slow condition on the airplane, so we never used it...an LSO would never allow the airplane to be underpowered for that long, either. So, we used down DLC if, and only if, we needed to correct for being a bit high/fast. But full down DLC was a modest effect, so we used it sparingly, and in conjunction with appropriate power corrections.

When the F-14A+ came out (later re-named the F-14B) with the GE F110-400 engines, it was really, really easy to get overpowered.

So, NAVAIR and Grumman made a few changes to the -A+/B model, those changes were retrofitted to the -A model in Air Frames Change 735, which included some gun gas modifications and changes to DLC.

With AFC 735, engaging DLC put only the inboard two spoilers up to 17 degrees. Forward thumbwheel deployed them up to 55 (max deflection) and aft thumbwheel retracted them. Those two spoilers moving throughout their entire range was more effective than the four spoilers going to 17 degrees.

Engaging "mod DLC" added 8 knots to on-speed and we still flew the donut. Still flew on-speed AOA. We had to adjust the aircraft recovery bulletins - the engineering documents that regulated the landing limits (winds, aircraft weights, aircraft speeds, arresting gear engine settings) to compensate for the increase of 2 knots with mod DLC.

I've got over 500 carrier landings, was a CAG LSO, and have a few top ten hook awards...so, the above represents an experienced opinion...but there is some opinion in it...

Your NATOPS link is for the F-14D model, after the DFCS modification was installed. I didn't fly that jet, but the description in your NATOPS describes exactly how DLC worked after AFC 735...so, I think I've got it right...

So, to precisely answer your questions:
1. yes. exactly the same AOA. But 6 knots faster for that AOA with old DLC, and 8 knots faster with mod DLC.
2. The inboard spoilers were effective above 10 degrees AOA, it wasn't until about 18 degrees AOA that spoilers became ineffective...that was well into wing rock.
3. See 2...the outboard spoilers worked well for roll control until about 18 AOA...but the mod DLC (appropriate for your F-14B) had them retracted for approach, unless lateral stick was used.

Hope this helps!

Cheers,
Astro

 

[Astro14]

Originally Posted By: Benito
I successfully shot an SR-71.

/forums/graemlins/shocked.gif



............... with my camera at the Cali Science Center in Los Angeles, Cali.

/forums/graemlins/banana2.gif

Does this make you a plane spotter?

 

[53' Stude]

Astro14: was the F-14 the most enjoyable plane hands down you ever flew?

 

[DeepFriar]

Thanks for this Astro. Great read and thankful we have guys like you who flew them. One question from me. Did you guys feel like the Backstop/Amos and later were direct copies thanks to our Iranian friends having passed the AIM-9 et al to the Russians?

 

[Astro14]

Originally Posted By: car51
Astro14: was te F-14 the most enjoyable plane hands down you ever flew?

I really like the Hornet. Great jet.

But comparing the two was like comparing a '68 L88 Vette and a new Miata...

The Hornet had great ergonomics, nice cockpit, intuitive weapons system, fine handling, better reliability (partly because it was newer). But it was slower, by a lot. It couldn't carry as much. Decent range when on profile, but poor endurance regardless.

Most of these issues were addressed in the Super Hornet redesign.

The Tomcat was a handful behind the boat, not easy to fly, but it was fast, carried a lot, had a powerful radar and the longest range weapon in the world...the jet itself had long range and great endurance.

Very different machines.

I'm a Tomcat guy.

 

[Astro14]

Originally Posted By: DeepFriar
Thanks for this Astro. Great read and thankful we have guys like you who flew them. One question from me. Did you guys feel like the Backstop/Amos and later were direct copies thanks to our Iranian friends having passed the AIM-9 et al to the Russians?


Well...one need only look at the AA-9 AMOS to know why we called it "Phoenix-ski"...

Russia has great engineers and great designers - but not everything they built was original...

 

[cjcride]

After all that great flight time in great aircraft is it still fun to fly 172's?

 

[Astro14]

Originally Posted By: cjcride
After all that great flight time in great aircraft is it still fun to fly 172's?

True confession: I've flown a 172 only once in my life, with my kid brother (who was USAF for a while). It was fun...but not the visceral thrill that you experience in a fighter.

On my bucket list is a Van's RV-8. I want the speed (relative) and short field performance, so that my wife and I can go places, and I want the simple aerobatic capability, too...more appealing to me than a 172, which has greater cargo/pax capacity, but less of what I miss...

 

[Papa Bear]

I have been seeing lately on our Canadian television that GE (and perhaps R-R) have built large test facilities for cold weather proofing their jet engines in Winnipeg & Thompson, MB.

Are you aware of those installations and do you ever feel "homesick" for some cold weather living or mosquito swatting ??

 

[Cujet]

Originally Posted By: Astro14

True confession: I've flown a 172 only once in my life, with my kid brother (who was USAF for a while). It was fun...but not the visceral thrill that you experience in a fighter.

On my bucket list is a Van's RV-8. I want the speed (relative) and short field performance, so that my wife and I can go places, and I want the simple aerobatic capability, too...more appealing to me than a 172, which has greater cargo/pax capacity, but less of what I miss...

As you may recall, we operate a number of fun aircraft, including Extra 300L's. And I have experience with the various RV series of aircraft. I even flew an RV-Super 6 (with 300HP 6 cylinder) . A good friend has an 300HP F1 Rocket, another a 315HP Extreme Air (aerobatic) and another an MX-2 (also 300HP)

I do like the RV-8, it's a good blend of economy and speed. But it's still a 4 cylinder aircraft, and therefore, does not have that "jet" feeling. The variants with the big engines actually do feel more jet-like.

I'd guess that you might be more satisfied with an Extra 300L. More room, much tougher, equal speed and so on. It has a jet-like feel. Wanna go up, sure! Up we go.

The MX-2 is an amazing performer, but it's thin carbon construction is known to fail. 2 recent catastrophic inflight disintegrations.

The F1 Rocket is a 300HP RV-8 "type" aircraft. (based on RV-4) and now has a different "evo" wing. Really climbs well, every bit as fuel efficient as the 8 and super fast. My friend was telling me his speeds. I called Baloney on that one and took my GPS along. OMG, 225Kts TAS. We actually flew base-leg outboard of a G-IV, turned in to land parallel runways and landed first! Climb is great, at over 4000FPM.

Yes, I know those are not really jet climb rates, but forward momentum is lower too, so the "feel" is similar. They will climb at steep angles.

Our experimental Extra 300L, with big 340HP engine will actually hover for a bit! That's a good thrust to weight!

 

[Astro14]

That's a great looking airplane. I'm aware of them, but budget might be a factor for me...that Extra of yours is sure an impressive performer...I'll have to keep it in mind....thanks for showing us!

 

[Cujet]

Astro,

I wish that Extra were actually "mine" It's owned by my boss. I own a mighty Cessna 177RG (such a joke by comparison)

As always, budget is the limiting factor. Even so, there are used F1 Rocket's and Used RV-8's on the market from time to time. Sometimes there are bargains!

That "Super Six" I flew was purchased for about half what you'd expect. (well less than 50)

And better than that, aircraft loans are low rate and long term. Payments are often quite low. A friend is financing an old Cessna 170 right now. Payments are less than $200/month!

 

[Astro14]

Thanks for the clarification. I still fly pretty good airplanes right now (757/767) so,I don't "need" an airplane yet, and with kids in college (well, one in medical school, one in college) my balance sheet isn't where I need it to be to begin considering airplanes...but, someday, I will...someday...

;-)

 

[RichardH]

Thanks Astro14 that's exactly what I needed. Also I think your memory is better than you give it credit for as the numbers you quote look pretty much right to me.

What you've given me is answer to the questions I asked but also enough information to get a feel for whether it's working right or not. I'm now building the aerodynamic tables from NASA-TM X-62244 figure 12 effect of direct lift control (spoilers).


The extra speed makes sense aerodynamically, but am I right to think that even +6 kts isn't the best for trap weight and therefore it counts against the idea of using DLC in the first place. Is DLC one of those things that looked like a good idea but didn't work out being used that often?

One other question; do both pairs of spoilers (inbound and outbound) control roll in the normal (non DLC) flight regime?

Thanks again
--Richard

 

[Astro14]

Originally Posted By: RichardH
Thanks Astro14 that's exactly what I needed. Also I think your memory is better than you give it credit for as the numbers you quote look pretty much right to me.

What you've given me is answer to the questions I asked but also enough information to get a feel for whether it's working right or not. I'm now building the aerodynamic tables from NASA-TM X-62244 figure 12 effect of direct lift control (spoilers).

The extra speed makes sense aerodynamically, but am I right to think that even +6 kts isn't the best for trap weight and therefore it counts against the idea of using DLC in the first place. Is DLC one of those things that looked like a good idea but didn't work out being used that often?

One other question; do both pairs of spoilers (inbound and outbound) control roll in the normal (non DLC) flight regime?

Thanks again
--Richard


Richard - The extra speed was a Navy decision. The airplane no longer met its original contract/specified landing speed, but as the airplane matured in service, the Navy brought out the NIMITZ-class carriers. Along with the NIMITZ came the MK7 Mod 3 arresting gear.

So, a couple of effects from the NIMITZ class. The ship itself was able to generate more wind over the deck through higher speed through the water. The higher capacity of the Mod 3 gear allowed the airplane to land with lower headwind. So, the Navy solved the problem of extra approach speed created by DLC through upgrades and improvements, though on older ships, landing speed was still an issue for the F-14.

The Navy's engineering folks in Lakehurst, NJ, published what were known as Aircraft Recovery Bulletins. ARBs covered the engineering limits of arresting gear/ship/airplane as a system. Mod 2 gear, along with the Tomcat, the biggest, heaviest, airplane to come aboard, was always critical in terms of wind. The USS AMERICA still had Mod 2 Gear on it when I waved (acted as LSO) during carrier qualification back in about 1994-1995. It had higher headwind requirements than the USS THEODORE ROOSEVELT, which, as a NIMITZ-class, had Mod 3 gear.

Now, back to your topic: the F-14. The F-14-B/D models had the GE F110-400 engine, which had considerably more thrust than the TF-30 in the F-14A.

To keep the airplane within the engineering limits defined in the ARBs, the F110 was adjusted by a system known as RATS, (Reduced Arrestment Thrust System...I think...).

When a -B/D had both the hook down, and weight on wheels, (conditions that are only present during an arrested landing) the core speed was limited to 92% RPM (again, going off memory here). Then, the F110 made about the same thrust that a TF-30 did during the arrested landing rollout, and the system would not have to compensate for the added energy from the additional thrust.

The Gear was normally set to 54,000# for a Tomcat if using single weight settings. That was normal. If an F-14-B/D had a "RATS light" (caution light in the cockpit indicating a problem with RATS), then the minimum wind over the deck (headwind) requirement went up by several knots, and the arresting gear had to be set at 58,000# to compensate for the extra pull from the F110s during rollout.

Now you know why RATS is in the airplane...

On to the other question. Yep, all four spoilers were available for roll control in flight, regardless of flap position, until the wings were back at about 57 degrees of sweep.

That changed with weight on wheels, however...and you only had inboard spoilers available with flaps up, or flaps in maneuver position when there was weight on wheels. I think this was to keep the outboard spoiler module from overheating on the ground. The outboard spoiler module created the hydraulic pressure to operate the outboard pair of spoilers.

It would only run on the ground with the flaps in the full/landing setting.

One other flying point: full flaps were fine for takeoff, and were required for a carrier catapult shot. But the airplane was also allowed to take off with flaps up, or flaps in maneuver setting when on land.

We liked maneuver flaps. Less drag when airborne, higher rotation speed, flatter transition to flight with maneuver flap. An F-14A in full AB, or an F-14 B/D in mil (AB takeoff was prohibited for a variety of reasons, including landing gear door overspeed, VMCA and others) would get airborne in about 1,800' at medium weight, zero wind, full flaps. Maneuver flaps made that distance about 2,500 feet...so, you still had lots of time to stop on a regular 8,000' runway...

Cheers,
Astro

 

[Shannow]

Great read
Thanks all

 

[lubricatosaurus]

Awesome thread here! Thanks Astro14 and RichardH, all the rest!

Originally Posted By: Astro14
On to the other question. Yep, all four spoilers were available for roll control in flight, regardless of flap position, until the wings were back at about 57 degrees of sweep.
Did the horizontal differential tail help with low-speed roll, in addition to spoilers, at low speed? (Understood that tail did all the high-speed roll control.) And what airspeed did the transition occur? "Transition" here meaning phase out spoilers for high speeds over some threshold.

Originally Posted By: Astro14
I flew an F-14B (with the F-110 engines) to 60,000 feet. At 1.5 IMN, and roughly 325 KIAS, it was still climbing over 1,000 feet per minute at that altitude. We started out in W-72, at about 150 miles away, but pointed back towards Oceana. I always made certain that I was pointed back towards "home plate" whenever I was trying something out...much easier to sort out a problem if you're already heading home...

Must have had a low stall margin in that flight regime! Level wings please, no spins today. ... Was more mach buffet gradually apparent as altitude increased or like a sudden surprise at some point? Seems like those shock waves would be dancing around at high AOA's there.

Interesting discussion of carrier landing techniques. For those reading that, remember its not how civil aviation airplanes are flown on approach. The following is a little oversimplified, yet serves to illustrate landing control technique differences:

Navy: Fix alpha, control flight path with engines (airspeed) and DLC (sometimes).
Others: Fix airspeed, control flight path with stick or yoke.
Summary at https://flighttraining.aopa.org/magazine/1998/May/199805_Features_Yoke_or_Throttle.html

Navy advantage: At least non-minimum phase pitch maneuvers near the deck don't bother you guys: Flare? What flare? The rest of humanity had better learn to fly with it.

 

[Astro14]

Lubricatosaurus - the horizontal tails on the F-14 were big. They had to account for the shift in center of pressure at high supersonic speeds. So, they were very effecive in pitch throughout the flight envelope.

In roll, they worked well at high speeds, while at low speeds, they were agumented with the spoilers. They still controlled the jet, even at low speeds, but the spoilers sure helped. At high AOA, and particularly in a departure (from controlled flight), they were very effective controls for recovery, including spin recovery. Spins in this airplane are a whole discussion topic unto themselves...

The spoilers worked normally, no change in gearing/deflection, until the wings were at 57 degrees (I think, still gotta' go look that one up!), but as the wings sewpt aft, the effectiveness of the spoilers was reduced.

High mach flight is an interesting topic. Stall margin at 325 KIAS at high altitude is about the same as it is at 325 KIAS at lower altitude. But there are some big differences in the airplane's performance. The wings were at 68 degrees (full aft sweep), so the stall margin was reduced/AOA increased by the sweep angle. The airplane flew fine at 68 degrees, but at 325 KIAS, it was flying at pretty high AOA, so the stall margin was reduced. I should point out that we considered 300 KTS a minimum/SOP airspeed for wings at 68, but lots of times we would fly the jet much slower at that sweep angle for a good reason, like cool pictures in flight...

But the greater consideration was the mach number. First, at 1.5 IMN, the center of pressure is pretty far aft, the wings move it further aft, so to achieve level/balanced flight, you have to have considerable nose-up trim. Like 10 degrees up on the stabs, almost a third of their full travel. This induces considerable trim drag. The F-14A had glove vanes to shift the CP forward and reduce trim drag, but they were eliminated in the -B/D models.

Next, the TAS of the airplane is about 900 KTS, so while you've got 325 KIAS acting on the surfaces, you've got a body moving through the air at very, very high speeds. So, to change pitch, or direction, took considerable force. Pure physics. Bank the airplane and pull a 2G turn, and the heading isn't really changing...because the airplane is going 900KTS and at that speed, the turn radius is simply enormous... It's acting a lot more like a bullet than an airplane...

 

[lubricatosaurus]

What I like about flying is that one has to cut right to the core of what all the complicated flight physics are doing.

Sure we engineers take our time on the ground (as in designing control laws for autopilots and stability augmentation), yet flying means one has to develop techniques and skills without juggling actual differential equations or being forced to remember everything in real-time. Yes, F-14's have entered wicked spins, yet we know the pilot had a lot on his mind at the time.

For the reader, I recommend anything "Stengel". See http://www.princeton.edu/~stengel/MAE331Lecture6.pdf for a rundown of the topic of flying, height, speed, air density, forces, etc.

The fact that Astro14 is able to reflect on what happens is remarkable from a human factors view. A pilot has to cut through the clutter, stay in control, make decisions in real time, without being bogged down in too much over-thinking-it while up there. .............. Its a balancing act.

As an engineer in the past dealing with subjects that drive pilots crazy, like roll coupling, non-minimum phase pitching, wind disturbance, wing twist, night blindness, the list goes on, automation from on-board computers running sophisticated control laws can make an airplane handle predictably and easy. Remember, especially for a combat aircraft, the pilot is also playing a chess game with the enemy, so the more the pilot concentrates on winning the chess game, the better. Leave flying to computers (OK, controversial, but engineers composing control laws love that kind of heresy!!)

Simply put, a pilot should only have to think of where he wants the flight path velocity vector and speed, and the computer makes it happen. Fun for engineers; pilots, not so much. Actually it promotes the pilot to commander in chief of the tactical situation in war time.

 

[Win]

I meant to ask last time this thread was active, but forgot, what is the noise level in the cockpit?

Do you have any noise cancellation devices, or is it just well insulated, or is it loud as heck?

Stupid question, probably, but it is pressurized? Do you have climate control with a/c, or just heat?

What happens as you transition across the speed of sound and back? Bump? Or just punch through like nothing happened? Is the wing loading / weight enough that you get a smooth ride? Or can you feel the air you're flying in?

What kind of comm radios did you have? VHF/UHF aeronautical band? Satellite? HF? All of the above?

Thanks for taking the time to answer all these questions.