Jet Pilots, Red-Outs, and High G-Turns

Anti-G suits. At high-G turns, the blood tends to rush to the lower extremities. It's the lack of blood and oxygen to the brain that causes the pilot to black out. At high-G forces, the bladders in the anti-G suit inflate and compress the limbs, preventing the blood from rushing into them so that there will be sufficient blood and oxygen supplied to the pilot's brain.

Hello Guest,

Your standard healthy, fit (inexperienced) pilot can endure maybe 2-4 G of acceleration in a quick turn before his vision and mental faculty are affected (a bit more acceleration for a female.) First remarkable symptom is loss of color vision and peripheral vision and it will progress up to complete black-out (unconsciousness.) This occurs as the person's blood flows from the head (and brain) into the torso and lower extremities, depriving the brain of oxygen.

The pilot can gain a couple more G's of endurance by strengthening the muscles of the abdomen, chest, back and legs. Then, when experiencing higher Gs, contract those muscles as much as possible (which can itself interfere with piloting) constricting blood vessels and providing less volume for blood to flow into and through, therefor leaving more blood in the brain.

A variety of other conditions can influence or assist the pilot. One is the pilot's level of stress and restfulness. (It is best the pilot is up on sleep.) Increased oxygenation of the blood (by breathing oxygen) is helpful. Configuration of the pilots seat (the pilot's position and level of support) is significantly influential. Genetic factors are also influential (some pilots simply endure more acceleration than others.) It is worthwhile, also, to be aware that onset of symptoms requires some amount of time. If high-G transients are sufficiently short they will not incapacitate. (Enduring high-G conditions, such as some types of spin, can last long enough to overcome all preparations.)

There are external means of assistance, as well. Anything that prevents blood flow out of the brain is helpful. One such system involves inflatable bladders positioned over thighs, back and abdomen which are engaged pneumatically when the aircraft enters a maneuver. These are sometimes called "G-suits."

Aerospace medicine references will say that with all these things optimized the pilot can handle up to 7.5 G of acceleration. In many cases experienced combat pilots can improve on this, occasionally to the point of being still conscious as the airframe is overstressed.

Perhaps these will be more helpful: Some views by others, on g-induced Loss Of Consciousness, on g-Suits, and on Space and Aerospace Medicine.

finally, a very thorough Powerpoint presentation from the US Navy's Medical Training Command's Naval Operational Medicine Institute on G-Tolerance Improvement Program (which I think is public domain.)

...unable to answer...ENVY...overpowering me!

Thank you.

This is no bulls#*t!!! If you're a Russian fighter pilot, you drink lots of vodka, smoke, and eat anything fatty and salty that will give you high blood pressure. Although they use G-Suits, they believe that the high blood pressure give them an extra edge against blackout. Perhaps they're right!

Hey Vermin!

That's great!!! I want to become a Russian fighter pilot. Where do I apply?

PD: I think they will need many new fighter pilot just like me after their last military parade (few days ago) At the red square, I fit perfectly. Last time I flew a military airplane was 22 years ago, same age of those airplanes they flew at the parade. Furthermore, It's only going to be a cold war again, so what can I loose?

(I'll certainly loose the Vodka if I don't.)

Wangito.

How's that volcano treating you? I know your country is like a bazillion mile long and about twenty feet wide, so you may not be anywhere near it. However, it sure looks nasty!!!

You damn right.

It surely is nasty... predominant winds are south-west so ash is being blown to Buenos Aires (No more... as buenos aires means good air in Spanish.) Argentina. so being about 1000Km north, we hardly notice it.

However my country is very very small, and the smoke there is coming from totally different source...But both sources, volcanoes and bombs, seem to be uncontrollable and have no immediate solution...

Wangito.

You guessed it. I am from Israel.

When Heikki Kovalainen crashed into the tyre wall at 140mph in the Spanish F1 race the deceleration was recorded at 24g yet he was uninjured & will be racing again this weekend in Turkey. A testament to both the fitness of the driver & the design of the car.

Remove the pilot from the aircraft and 2 things happen:

1. They don't die or get captured; since you don't lose pilots, you can keep the best one's for combat.......read about the effect that the battle of Midway had on Japanese pilot skill level present at the Marianas Turkey Shoot.

2. You can design the aircraft to perform at G forces that would kill a human, if the human were on board;

Oh Yeah, you can eliminate all of the biomass support systems(windscreen, oxygen systems, visual displays, etc) which will reduce the cost and weight of the aircraft.

Above replies address black outs but not red outs.

Black outs are caused by positive G's that force blood from the brain, and red outs are caused by negative G's that force excess blood into the brain.

Above is an image of a P52, a dual fuselage aircraft with a pilot in each fuselage. During a rapid snap roll, one pilot would black out and the other would red out.

In effort to minimized these effects, fighter aircraft designers place the pilots as close as possible at then the center of rotation and pitch.

Snap-roll or any other roll.

Both cockpits will turn the same direction, hence same sign "g" loads. Only that one pilot will have different "g" factor being in different arc position. In order to get different sign (negative or positive,), one cockpit must make an inside turn (positive) while the other must make an outside turn, (negative) or one pilot flies up-right and at the same time the other flies inverted. that, fortunately, for the pilots (and the airplane) doesn't happened.

Just so that you understand the procedure For Snap-roll:

1. Fly strait and level, At the maneuver speed (different for each airplane).
2. Pull hard on the stick all the back.
3. When the nose is 30° to 40° over the horizon,
4. Push hard left or right rudder all the way in, keeping the stick all the way back,
5. Once back in up-right position, release pressure on the stick and the rudder,
6. Resume strait and level flight.

Where did they split directions?

Wangito.

If you're going to turn, I want you to take it outside, young man!!!

wangito,

Unless I have forgotten how to fly. Your procedure is for a barrel roll which does not require ailerons. When ailerons are applied, one wing moves up and one wing moves down. In the P-82, the cockpits for the pilots are not on axis with the centerline of a roll, they are in the wings. Therefore, one pilot moves up and one pilot moves down.

Hey Snave!

You wrote:Unless I have forgotten how to fly

Maybe you have, but Assuming that you haven't, there are two possibilities, Either you have never done neither barrel roll or a snap-roll (which is probably the case),or that we are talking about two different maneuvers...(Which probably is not the case...)

Quote: "The barrel roll is a maneuver in which the aircraft rotates 360° around the longitudinal axis while the nose of the aircraft describes a circle around a reference point real or imaginary. The circle described should be of constant radius around the reference point." unquote (Van sickle's Aerobatic flight maneuvers, p.439). The same description of a barrel rolls appears in various other flight maneuver guides both military and civil. Hence the name, the aircraft flight path describes a flight around an imaginary barrel.

If you can fly a barrel roll as described here without the use of ailerons than you must know something about flying that no one else but you knows. Actually in a not high performance airplane, such as the Stearman, Great Lakes or a Decathlon, if you do not apply full aileron you will never finish the roll and will soon find yourself in a steep dive nose down...

This is nothing personal you are simply wrong.

Wangito

CPL,CFI, SE and ME CFIH CFII. since 1968

But why two pilots?! And what determines who gets to steer?

Why wasn't it built like a P-38 with one pilot?

I have to speculate as you probably understand I wasn't part of the design team...

I do believe though that this was an operational issue. the same that later was behind the two pilot crew on almost all large "F","B"and "P" aircraft.

1. four eyes are better than two. These are the days of the pre fully computerized WDS (weapon delivery system) So while one flies the other is responsible for WDS.
2. number two has enough flying skills to bring the bird back home in case of #1 becoming impaired. pilot redundancy.
3. lower pilot work load. Fatigue and overload are the Fighter pilot worst enemies. I believe this was the main reasoning behind this especially on long range missions.
4. During the Vietnam war Back sit F4's pilots were also called "navigator" same for later F15's, but they were tandems. not side by side.
5. Who gets to steer? The designated PIC (pilot in command).The navigator or weapon officer will usually be a lower ranking officer, or if same rank than usually with less seniority. and will fly the airplane whenever told to do so.

That reminds me of the standard practice at the officer's mess. "Always squeeze the lemon in the direction of the lower ranking officer, Always!"

Wangito.

You should see the collection of WWII vintage birds flying into Moffet Field today...

B-17s, B-29s, P-51s, and a whole bunch of others I can only guess at. There's one B-17 that you can ride for donating to charity. Once air-born, you're welcome to unstrap and roam around!

Why two pilots?

The P82 was developed during WWII. There was no time to design an aircraft from scratch. The P51 was very successful. Taking two production P51 Mustangs and sticking them together got the required increase in range that was needed and was quick to get it into production as it only required designing a wing section to join the two fuselages and a section of tail. They could be built on the same production line as the P51 and new production tooling was minimal. These birds saw no action in WWII as the war ended. They did see a little action during Korea. The problem that the pilots could red-out/black-out while flying evasive maneuvers and the fact that jets were starting to become viable, made the plane obsolete.

Hello Snave,

Excuse me for being inquisitive, but I am sure your insistence on the positive/negative issue is based on some info that I don't have. Can you give the link to where you read this? I am very curious.

Wangito.

Hello wangito,

I do not have an internet site to offer, but I did email my dad a WWII vet (8th Army) and USAF vet (graduation class of 49C). As a base commander, stationed state side during the Korean War, he had flown with the P82 and also debriefed the pilots. This is what he had to say:

I worked with F 82 in many interceptions which was called the twin Mustang. I had them come out to our radar site to beat up the base so the guys could see for them selves these planes and feel like they were in the Air Force as we were at Pacific Beach, WA. I put them on the base PA system so the guys could hear the pilots talk and get into the mood. We used them for base alert so it was like real. We had a cook in white who was hiding behind a log and the guys said. I just nailed the cook in white hiding behind a log. They were way below the radar sail so right on the deck and below hill at ocean level at the base at time.

The F 82 was hard to land as instead of 3 points on the landing gear, it had 4 points so some time would bounce back between the four wheels. Guys were careful not to roll too fast as not to black or red out each other. I was working with one (F-82) on an intercept when the pilot said he wanted to abort the mission. I asked why and he said his R/O (Radar Operator) wanted to come home as his engine quit.

Another twin engine aircraft that my dad is studying is the Bell Airacuda. He is sending me an article and after I get it I will be able to site another source that describes black out / red out. For the mean time my dad wrote ... the Bell Airacuda [article] talks about the lousy design and engineering problems it had. This plane had a twin engine pusher type design where the two gunners sat in the engine nacelle with the guns they fired. This was way out side of the center line so the gunners either blacked out or red out on a fast roll. Bail out was bad as it took 6 seconds to stop the props so the guys could bail out. This was long time for that stuff. You will see what a nutty plane this was. It was abandoned at Wright Paterson and just forgotten as a bad dream. I guess they finally scrapped the thing.

My dad also adds some interesting observations about the human body's reaction to G-forces. In a plane like a F 51 trainer or a T-33, the guy not flying would black out before the guy flying would as a passenger would not tense up as well as the guy flying. I remember a guy showing me how he made gunnery passes and I would always black out and not see what he wanted to show me and vise versa.

I will provide more if you are still not convinced.

Hi Snave.

Read your dad's mail carefully. He never said that one pilot would black-out while the other would red-out. Or maybe my English is failing.

1. More than 1g (+ or -) loads will only happen in an accelerated flight.
2. During a constant velocity at any speed there's 1g. and they both will have the same g. which is their own weight.
3. In order to increase g-loads to more than one, be it plus or minus, you need to accelerate or decelerate. Increase your speed, lower your speed, pull Up,or down, turn, or any combination thereof.
4. If both pilot are flying the same trajectory they will always be under the same g-loads. I have never seen an airplane where one pilot goes to war while the other at the same time in the same airplane flies back home...
5. The difference in g due to different radius is very small. and again , it is the same sign g.

Sorry pal, you didn't convince me.

Wangito

On the other hand, if we were talking a tandem UFO, then say no more!!! You could have aliens blacking-out, redding-out, even greening-out! Whoa!!! The possibilities are endless!!!

Did anybody get a peak at the Airracuda?! What a vomit-comet ride that must have been!!! "Hey I was just about to shoot that guy! Why'd ya turn?!"

Dear PhysicsProf,

I agree that there is much information available on the internet and in text books, but you make some wild assertions.

You state "Our guest has already obviously read all that stuff." and then conclude with "They obviously were looking for personal experience that goes beyond what they already have available to them." I have read and re-read the guest posting and do not see how you read your observation into the question and then draw the conclusion that you do. I read "…experiencing red-out due to high G-turn?" and observe an error in his question as a "red-out" is caused by pulling negative G's while a "high G-turn" provide positive G loading and draw no conclusions but suspect that (1) guest has not done their homework, (2) English is not a native language, or (3) guest is careless with details.

Professor, I hope you teach better science (conclusions based on careful observation) than you have demonstrated here. I think that the rain is on your parade as you are the one that is wet.

Oh, dude! Don't talk like that! I mean they're out there, man! They're after us, man! Ya can't be too careful these days! For all we know they might be reading our minds right now! Oh no, man!!! I can feel 'em!!!

That's my best Dennis Hopper impersonation.

Ouch! Who put the tack in that extremely WET diaper of yours Snave? Are you really THAT naive? Truly?! Honestly?! More evidence that this place isn't worth my time!

That is why you have not registered?

Dear all

What are de limits and priciple of red-outs? (all the blood flows to the head, why a delplation of oxigen?)

Are the g-suits for red-out?

what are the limits a person can bear in red-out? any data?

The F16 is limited at 9g is an F15 not limited?

Thanks

the F-16 is a fly by wire computer limiting system that will only allow the acft. to pull G's as conditions allow. the F-15 is only limited to the pilots ability to handle the load.

Farman - I extracted these words from the Encyclopedia Britannica:

"Negative acceleration stress occurs when the direction of acceleration is from feet to head. This causes a slight displacement of the internal organs in the abdomen and chest and a rush of blood to the face accompanied by the feeling of congestion. As the acceleration increases the congestion increases and throbbing pains are felt throughout the head. When the…"

AND "...and there is a gritty feeling under the eyelids because of swelling in the small blood vessels. There may be temporary loss of vision or all objects may appear red; this latter condition is known as "red-out." The mental confusion that develops at high accelerations may lead to unconsciousness."

Because a G-suite applies pressure to the outside of the body to push the blood up from the legs and abdomen toward the head, they only help pilots withstand positive G forces for a longer period of time before experiencing brown, grey, then a full black-out. I do not believe that there is any device to help offset the effects of negative Gs. Readers, correct me if I am wrong.

:...You wrote: "correct me if I am wrong"

OK than :

"G" suit partially stops blood streaming. by "embracing" the large blood vessels. Works both ways, Centrifugal and centripetal.

Wangito.

They have these new, big, puffy hats that squeeze the blood out of the brain to prevent red-out. I think they've been testing them in Washington for the last eight years.

Yah, I have heard about it...

After the proof of concept and R+D are all done they promised to use it on almost all of the world's leading heads. I just hope it will not to late for some million or more Burmese. However I know it will, as these guys, even when their blood flow is perfectly OK they still can't think.

Wangito.

wangito,

Correction appreciated. I gave you a vote because you taught me something.

Thanks,

You're very welcome sir.

Wangito.

I was watching the Red Bull air race on tv at the weekend. The speed and G force for each run was displayed and the fastest competitors were pulling in excess of 11G when pulling up to turn in order to run the course in reverse. They were doing this 3 times within about 5 minutes which seems amazing.