I have seen a video from a french ex-Rafale pilot. He was saying it was important to try to get a kill as soon as possible as the high G's wear you out quickly. And the Rafale sure can pull high G's. I suppose that's where the movies differ from reality (aswell)
F-14 Questions Answered - Ask Away
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I could pull sustained six G all day long (well, OK, for several minutes, there is a fuel consideration).
But over that, as the level of straining went up, it becomes very difficult.
A pilot loses consciousness under G because the heart isn’t able to get blood to the brain. First symptoms occur in the visual cortex - “grey out” as color is lost. You’re on the ragged edge of losing consciousness if you lose color vision. After 5-10 seconds of insufficient blood, the brain shuts down from lack of oxygen.
Fighter pilots wear a g-suit. It covers legs and abdomen. The airplane pressurized it under G, with pressure proportional to G, and the inflation of the bladders in the suit squeezed blood from lower legs and abdomen back to the heart. It added about 1.5 G of tolerance to the average pilot.
The rest of the tolerance comes from straining. By flexing calves, thighs, abs and chest, and taking in a deep breath and holding it while squeezing your thorax, you could raise your blood pressure enough to get blood up to your brain against gravity that was pulling it down. You had to let the breath go, take another very quickly, and get on the pressure/muscle contraction again to keep the pressure up. Lose blood pressure to the brain, and you’re unconscious in seconds.
I’m 6’1”, with low blood pressure. 90/60 at the time. So, basic physiology is against me. Longer column height from heart to brain. Takes more pressure to get it up there and I didn’t have a lot to begin with.
Just sitting, in the centrifuge (where we learned how to handle G, and how to do the straining maneuver) I was good to about 3 G. Not much. Shorter pilots had it easier.
So, with G suit, anything over about 4G and I had to get on the straining. It was a real workout. I generally started to strain, lightly, as I got close to 4 G, to stay on top of the oxygenation challenge. By 6 G, I was working very hard. Again, my physiology. I was good up to 9G, and experienced 10G in an F-16, but I was greying out.
At high G, you needed the muscle strength to be able to strain effectively enough to raise your blood pressure enough to get the blood up to your brain. But it was hard work. Like wrestling, a whole body effort. You needed good aerobic capacity to keep up that level of muscular activity.
So, most of us lifted weights for the strength, and did cardio for the aerobic capacity. You absolutely needed both.
Incidentally, at about 7.5 G, again my physiology, the capillaries in the skin on the back of my legs would burst from the weight and the blood pressure. I would feel the “tingle” and I had little blood spots (bruises, that looked like freckles, or measles) on my legs for a couple days. In the Hornet, this was useful, as the stress limit was 7.5G. I rarely hit that number in the Tomcat, as the stress limit was 6.5G, and if I felt the “G measles” I knew I was beating up the jet.
In the F-16, I felt them every flight, often multiple times.
I think the Rafale can go to 11G, the SU-57 even higher alledgedly. So with what you say this isn't something you can do all day long... I usually have high blood pressure, lowest I ever measured was 120/90 IIRC. But I'm not a pilot so I'd rather have lower blood pressure
9G is about all a pilot could take in my day. That’s G-suit, straining, and a seat angle in the F-16 that lowered the column height. Some pilots were in better shape than others, and GLOC* was a real issue.
Positive pressure masks (“Combat Edge”) that force the O2 into your lungs, improved G -suits, can raise that a bit...but 11G is an astonishingly high stress limit. Considering that the F-35A and F-22 were built to 9G and the F-35C and F/A-18 were built to 7.5.
The Combat Edge positive pressure mask and improvements in G suits weren’t intended to allow higher stress limit airplanes, they were to reduce the number of GLOCs. GLOC was generally fatal.
*G-induced Loss Of Consciousness.
Positive pressure masks (“Combat Edge”) that force the O2 into your lungs, improved G -suits, can raise that a bit...but 11G is an astonishingly high stress limit. Considering that the F-35A and F-22 were built to 9G and the F-35C and F/A-18 were built to 7.5.
The Combat Edge positive pressure mask and improvements in G suits weren’t intended to allow higher stress limit airplanes, they were to reduce the number of GLOCs. GLOC was generally fatal.
*G-induced Loss Of Consciousness.
I was an an air show seeing the USAF Thunderbirds with their crew putting on their G-suits. They turned it into a big show for some reason. It didn't seem like they really needed to do it in front of all the spectators.
Heard the Blue Angels don't do that because inflation could interfere with the center stick flying in really tight formation. Something about tensing up muscles to prevent blacking out.
The Blues do rely solely on the straining maneuver I described to manage G. They pull up to 7.5, sustained, and that’s about the limit. Human body can’t sustain more than that without help.
They have had a fatal mishap from GLOC. Kevin Colling, a former squadron mate, was among those lost.
I take it that it's not a big issue for normal flying with a G-suit and a center stick.
If that was an issue, all fighters would be designed with a side stick or no pilot of a center stick aircraft would wear a G-suit. I think the Blues don't wear them because they don't do enough sustained G's to need them. A Blue Angels pilot once admitted to that after first saying it was because Naval Aviators don't need them. Lol.
As for the Thunderbirds, if I were the commander, I'd never let anyone fly an F-16 withoiut a G-suit. Plus, one of the solos always does a 9G turn as part of the performance.
I was recalling from memory, but the official answer is that it's to reduce the chances of inflation causing a "un-commanded aircraft movement". It's Q&A #15. I suppose it's not so much of a problem having a slight unintended input as long as there isn't another plane a few feet off your wingtip.
G-suits are designed with air bladders (pockets) that inflate and deflate to keep a pilot's blood from pooling in the pilots' legs while executing sharp, unpredicted combat maneuvers. Unlike combat flying, the Blue Angels demonstration pilots know the maneuvers they will fly prior to execution, so each pilot knows when one will be experiencing heavy gravitational forces. Anticipating the changes in gravitational forces allows the Blue Angels demonstration pilots to combat G-forces with muscle contractions. Additionally, G-suits would detrimentally impact flight safety.The Boeing F/A-18's control stick is mounted between the pilot's legs. The Blue Angels have a spring tensioned with 40 pounds of pressure installed on the control stick that gives the pilot a "false feel." This allows the pilot minimal room for un-commanded movement. The pilots rest their right arms on their thighs for support and stability while flying. Therefore, inflating and deflating air bladders in a G-suit would interrupt this support and stability, causing un-commanded aircraft movement.
Sounds like they refined that answer since I was a good bit younger and asked the pilot. Lol. Pretty sure the T-Birds used them in Phantoms and T-38s. Never heard of that causing an issue. But then again, I've never flown any of these jets, so I can't be sure.
Just curious when it was acceptable to take your mask off. Of course movies show pilots taking them off all the time, but I thought at high altitude it would lead to hypoxia. I was reading some comment from a former US Navy pilot saying that he might take off his mask to smoke, which I supposed was allowed back then.
I've seen video of demonstration pilots flying without masks, but just a boom mic.
I've seen video of demonstration pilots flying without masks, but just a boom mic.
As I recall, Navy Instruction that governs all flying, known OPNAV 3710, required that O2 masks be on from takeoff to landing in tactical jets. It further required that the mask be on when taxiing an airplane on the Carrier flight deck. The Blues had an exemption, just like they were exempt from G-suits.
Lots of guys took the masks off in flight.
I wasn't one of them.
I had a squadron mate - known for lots of bozo moves - get the bends one night flying out of Oceana. The bends. They had to rush him to the hyperbaric chamber (which the Navy has for divers) to save his life. Had he been on O2, the N2 would have been purged from his blood he would have been fine. He was too "cool" to wear the mask...which didn't work out that well for him.
An F-14 was lost to hypoxia. The crew had taken off their masks for a photo shoot with their wingman. The wingman lost sight, and the jet hit the ground fifty miles later. They were strapped in their seats in the wreckage, masks off.
High-performance airplanes are a risky endeavor. I reckoned it was in my best interest to stack as many factors as I could in my favor. I wore the gear that was provided, properly and diligently. G-suit, helmet, O2 mask, and yeah, that horribly uncomfortable dry suit that we wore over the water in cold weather. Sure did suck. But being in a raft on the ocean without it would have sucked a whole lot worse.
Seriously though, I’ve been on a few combat ships and yeah they look lived in. I sat in the captain’s seat on a destroyer and it was Naugahyde and uncomfortable as heck. The best part was the 6’6” Chief Petty Officer showing us how he ducked getting around.
Very good video showing F16 Pilot having to work really hard evading missiles over Iraq. His breathing tells you just how taxing those high G manoeuvres must be. These guys are peak of physical fitness too. Also somewhat stressful is the fact he could die any second.
Also i was not aware of the auto gcas. It saved this pilots life.
Also i was not aware of the auto gcas. It saved this pilots life.
WOW!
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Astro would definitely be better to answer, but I think problem is not taking off as much as landing is with that load.
Max takeoff weight is the same for both field and carrier. For the F-14, it was 72,000 lbs. That gave you about 9-10,000 lbs of ordnance/weapons with full internal fuel and full external tanks, carrying 20,000 lbs of fuel.
Max normal landing is the same as well, 54,000 lbs, but a minimum sink rate landing can be done at a field at a greater weight than normal landing.
The old max takeoff weight for the F-14 had been 69,800. The extra 2,200# additional weight was added in the very early 90s to allow for more air-ground payload. But you could not bring back all of it, some of it would have to be delivered or jettisoned for landing.
Max normal landing is the same as well, 54,000 lbs, but a minimum sink rate landing can be done at a field at a greater weight than normal landing.
The old max takeoff weight for the F-14 had been 69,800. The extra 2,200# additional weight was added in the very early 90s to allow for more air-ground payload. But you could not bring back all of it, some of it would have to be delivered or jettisoned for landing.
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Still my favorite airplane and a beautiful jet. BITOG is closing older threads, most of which are no longer relevant, so this is just a bump to keep this particular thread alive, just in case folks are interested in talking more about it.
Cheers,
Astro
Cheers,
Astro
Great thread!
Don't be sad, @AutoMechanic - the threads will be closed for new replies, but can still be searched and read. Better to start new threads for new discussions.
This thread, however, isn't really affected by time. We are talking about an airplane that first flew in 1970 and was retired in 2006. The discussion remains accurate and relevant.
