G Tolerance

[Grob Queen]

As a PPL Student with 34 hours, I am starting 60 degree advanced turns. Would anyone have any ideas on how to "get" g tolerant please? I desperately need too!

Thanks!

[Rod1]

The more you do the better you will get. You can try tensing your stomach muscles which will help. Unusual to have an issue with steep turns though. How many have you done so far?

Rod1

[Grob Queen]

So far I have had two sessions - three weeks apart. Flown about 2 60' and 5 45' turns...and a few aeros (with friends as the P1)

[flybymike]

As a student I found that once established in a steep turn you become unaware of any G at all. To this day I only find short sharp bursts noticeable.
, or for example pulling out of a spin (which were compulsorily trained in my day)
Edit I wouldn't do aeros if you paid me...

[Ultranomad]

Grob Queen, are you sure your problems have to do with g? High g causes blackouts similar to the feelings you can get when suddenly standing up after a long rest or a hot bath, or suddenly stopping after a dash, but these are very unlikely for a healthy person experiencing a 2g overload (60° turn).
On the other hand, nausea is caused by Coriolis forces and/or a visually perceived rotation. You can train yourself to overcome it, but the first thing to do would be to eat the right kind of food before the flight: don't fly on an empty stomach, nor immediately after a hearty meal. Many pilots doing scenic flights recommend their passengers to eat protein-rich food (like steak and eggs).

[BackPacker]

I agree with Ultranomad.

The symptoms of too-high g-forces are loss of color vision (greyout), tunnel vision, blackout and eventually loss of consciousness (g-loc). These symptoms all occur because the brain, and in particular your eyes (which are most sensitive to this) do not get enough oxygen.

Oxygen is delivered to your brain by your blood. It's your blood pressure, generated by the heart, which pumps the blood upwards to your brain. Under normal circumstances, your heart is able to pump blood about one meter upwards (that's the reason that IV bags are hung relatively high). The vertical distance from your heart to your brain is about 25 centimeters. So a normally proportioned, normally fit adult should not suffer from any g effects until reaching, approximately, 4G.

There's a lot more science involved and there are several aerobatics books that cover this in a lot more detail, and with a lot more accuracy. But at 60 degrees bank angle you should only be pulling 2G and that's nowhere near enough to cause g effects. Even if you've done negative g's just before (which you have not). (Although if you go to 75 degrees angle of bank - just 15 degrees more - you need to pull 4G already and that might trigger g effects. But in a typical training spamcan, your cruise, full power and stall speeds are so that you will barely be able to sustain a 4G/75 degree steep turn for long enough for g effects to manifest itself.)

As Ultranomad says, it's probably nausea. You can get desensitized to this easily just by flying a lot, particularly steep turns and other unusual attitudes/aerobatics. There are also several exercises you can do on the ground. Here's a scientific paper on this subject:

http://medind.nic.in/iab/t07/s1/iabt07s1p37.pdf

And here's a site of a doctor that sells DVDs. Haven't seen those myself though (I stumbled on it searching for the link above), but it might be worth a look:

Motion Sickness (Travel Sickness, Air Sickness, Sea Sickness, Car Sickness, Cyber Sickness, Space Sickness) Causes, Symptoms, and Natural Prevention Information on PumaMethod.com (http://www.pumamethod.com/)

[Torque Tonight]

A 60 AoB turn is 2G. My granny could handle that without special training.;)

[FlyingSportsman]

Tense those buns! :E

[chevvron]

I once had a Hunter flight without a g-suit. We did a loop and pullled through at 5.5g, at which point I was greying out. I had previously had a Hawk flight where I experienced the workings of a g-suit, as it involved rapid changes of attitude between -3 and +4.5 g.
I have to admit I puked when we did a negative g barrel roll!

[Pilot DAR]

Grob, you've had some good explanations here. I would think it very unlikely that the G's you would experience in flight at the basic flight training stage, or in the aircraft type you are flying would be the least troublesome. Nothing you should be doing in that plane should be subjecting you to more than 2G, and this should be easily tolerated by any healthy person. Truly, if 2G is a medical problem for you, medical advice is in order.

For myself, back in the old Aerobat days, I found that 4+ was my limit as the passenger, and I could manage 5+ as the pilot. This seemed about the same for my buddy, as we entertained ourselves greying each other out one afternoon. Any maneuver exceeding 3G would be aerobatics, and I suggest that is not the type of flying you should be doing just yet, unless you are the passenger...

[I Love Flying]

Question: would having lower than normal blood pressure (not dangerously low, just lower than average) affect a pilot's/passenger's g-withstanding capability?

[BackPacker]

Yes.

In fact, the Royal Dutch Airforce instructor who taught the course on g exposure etc. (combined with the centrifuge session) noted that people with an unhealthy lifestyle and the resulting high blood pressure, were less susceptible to g effects than people who were really fit and healthy.

(On the other hand, the fit and healthy are more capable of performing the straining techniques that are required to keep the blood in your head, and are able to sustain these for a longer duration.)

And on a related note: I was once asked to fly aerobatics (LAROSA aerobatics, nothing serious, -1 to +4G maximum) with a girl who had a heart condition (leaky valves or something like that). I refused. And when I explained why, everybody understood and the issue was not pressed further.

[lopresto]

Grey/black/blu/strars/red vision... with a PPL aircraft.. well..

BTW... enjoy them :D

[I Love Flying]

(On the other hand, the fit and healthy are more capable of performing the straining techniques that are required to keep the blood in your head, and are able to sustain these for a longer duration.)

Please can you briefly explain these techniques in layman's terms to somebody who is yet to experience aerobatics (but rather fancies it one day, but who also has been told their blood pressure is slightly on the low side)...

[BackPacker]

Please can you briefly explain these techniques in layman's terms to somebody who is yet to experience aerobatics

As noted earlier, an introduction to aerobatics, up to Sportsman level, does not require exceeding -1 to +4G limits even when flying in competition. At +4G the worst you should encounter, even with low blood pressure (I've got that too) is mild symptoms and as the +4G is only sustained for maybe half a second, straining techniques are not really required.

Furthermore, straining techniques are not something you can learn from a book or PPRuNe post. You should practice them with a knowledgeable person present to tell you what you did wrong. Especially since if you apply them in the wrong order or at the wrong moment, you could actually be pushing blood away from your brain instead of pushing towards it.

Having said that, here's what I was taught during that Air Force centrifuge session. It's essentially two things that happen simultaneously. You tense all the muscles in your lower body up to your stomach, and you make sure to keep as much air pressure in your lungs as possible.

Muscles to tense are, from the bottom upwards:
- Toes: Feet flat on the floor, try to curl your toes against the soles of your shoes.
- Lower legs: Push your feet against the floor as if you are extending your feet.
- Upper legs: Try to clench your legs together, at the same time apply a counterforce. Also try to bend your legs, with the floor providing a counterforce.
- Buttocks: clench
- Stomach: clench

At the same time, inhale, block your breath and try to exhale (which you can't). Of course, you need to keep breathing so this is done with quick puffs after which you block/exhale again. (Some people advice you to grunt but really, the sound you make is irrelevant. What's important is to build up the air pressure in your lungs to assist your heart in pumping the blood upwards.)

A very common mistake is to let go of muscle tension as you exhale/puff, which is very dangerous as you can get g-loc very quickly under those circumstances. But you also need to make sure you time the application and amount of these straining techniques properly. If you overdo it, you may actually be more susceptible to g-loc.

The reason for the latter is that in your brain there's a little device (don't know the English word for it) that measures your blood pressure there. If the blood pressure is too low, it tenses the muscles around your arteries. If the blood pressure is too high, it releases the muscles around your arteries. But - and that's an important but - there is a delay of about ten seconds in this reaction.

So if you overdo the straining techniques, or apply them too early, the blood pressure in your brain will rise (since there's no, or not enough g force to counter it). That little device notices this, relaxes the muscles around your arteries to lower the pressure and as soon as the g force comes in, all blood will flow away because you've got no more counterforce to give.

Equally, if you go from, say, minus 3G to an immediate positive, say, 5G, it's extremely dangerous. Even more than going from 1 to 7G, say. This is because under negative G all the blood rushes to your head with rising blood pressure as a consequence. So all your arteries open up. If you then apply positive G all of a sudden, all the blood rushes away.

(The Air Force physician was really surprised to hear that some of the Advanced aerobatics pilots in our group did this. He considered the -3 to +5 situation far more dangerous than the +9 that F16 pilots need to sustain. As there's not a lot of reason to push negative G's in combat, it was something that he had never encountered. They also can't simulate this with their centrifuge.)

Once again, this is only skimming the surface of what's happening in your body and what you can do about it. The lecture we got from this Air Force physician took more than two hours and even after that lecture we did things wrong in the centrifuge - with several g-locs as a result. So please do not assume you can apply the perfect straining techniques just by reading the above text and some practicing in front of the mirror.

[I Love Flying]

Thanks for your reply Backpacker, that's understood. I was just interested to know what you were talking about really.

[Lunchmaster]

Interesting post. Having not flown aeros for more than a year I found myself feeling extremely rotten flying a Chipmunk last week.

Briefed as an aerobatic sortie with spinning, loops and barrel rolls I was flying the aircraft from the front seat with an experienced instructor in the back. Spinning was disorientating to say the least and it took me three attempts to nail the correct recovery technique with considerable height loss - good reminder in how essential it is to only begin aerobatics at a suitable height above the ground.

Next up were some loops. During the third loop I was happily watching the horizon reappear over my head when I found myself get the cold sweats and a dry mouth. Uh oh.

Moving on to barrel rolls and I was very, very queasy so called it a day and flew the aircraft back for an uneventful landing.

I was surprised my tolerance for aerobatics was not higher given previous experience. I'd eaten a decent breakfast, was rested and excited about the flight and well briefed about what to expect.

I don't think it was down to G tolerance but the onset of nausea was something I'd like to reduce or at least delay next time. Would using breathing and straining techniques have helped? Would the nausea be caused by G or just the mechanics of the inner ear?

Lunchmaster

[bsfish2003]

I have noticed that, if someone else is doing the steep turn, you feel the G. If you are doing it yourself you don't notice the G.

[B2N2]

Great post BackPacker :ok:
I was once balast weight on a serious aerobatic sortie in a glider, we went from -1.5 to +4.5, everything that we did prior was fine including inverted flight but this maneuver had me laying on the grass in the shade for a good part of the day.
With practice we could get to (briefly) +7 G's without passing out but vision would be completely gone. Never did develop a taste for negative maneuvers.
Hate them to this day.

As to the original poster;
Did you try the steep turns at the beginning or the end of your flights?
If it was at the end of your flights you may have been fatigued already.
Flight training at this stage of the. game is very exhausting, mentally and physically.
It is not unusual for an instructor to not recognize these symptoms and make the training flights too long.

[flyinkiwi]

I read one incident a few years back when a young and healthy CPL student went up with a fellow student to do some CPL revision after a heavy night out on the town and G-LOC'd doing a max rate turn in a 172. Fortunately the other student was flying at the time so they made it back in one piece. The incident report stated that fatigue, the lingering effects of alcohol consumption, dehydration and a lack of recent experience with sustained G maneuvers were contributing factors.

[Grob Queen]

Thank you everyone so far for all your advice - whether its G or nausea i'm feeling, I know its not pleasant and the sooner I can combat it the better! Haven't been flying since my original post so can't tell you if your advice is working...

Bsfish - you are so right about someone else doing turns and feeling the g more...when my instructor shows me a manouvre (like the Emergency break) its worse than when i then do it.

In answer to B2N2's questions; because we are focusing on steep turns, its throughout the trip. After an hour doing steep turns as well as practising turning onto headings (with normal AoB), I am indeed tired! Exhillarated and on top of the world, but tired! Do you think its just the stage of training I am at that I am feeling it worse than a more experienced pilot? Everyone tells me i'll get through this phase...

And I think it was Backpacker's note (sounds a fascinating lecture) about low blood pressure? I know my blood pressure is very good, so maybe that may be having an effect?

[BackPacker]

I still feel wrung out after I've done half an hours aerobatics. So yes, this stuff wears you out even after a lot of exposure. But trust me, you do get used to it. It just requires a few flights to build up your tolerance.

And no, I don't think low/high blood pressure has a direct effect on nausea, unless the situation is so extreme that it causes all sorts of side-effects. But then you'd probably not fit enough to fly in the first place.

What does have the most effect is feeling well. Well fed (but not overfed), well rested, excited (but not apprehensive) about the upcoming flight, well clothed (not too warm) etc.

[B2N2]

After an hour doing steep turns as well as practising turning onto headings (with normal AoB),

You should not be doing steep turns for an hour.
At the most 3-4 then something completely different.
Do you fully understand the theory and aerodynamics behind steep turns?
Try them will all instruments covered up.

[Grob Queen]

Thanks B2N2.

Thats an interesting point about steep turning with teh instruments covered up. My instructor has not suggested this (although another instructor got me to fly in teh cct witout looking at the RPM and getting me to "feel" and hear the changes of teh engine rather than rely on instruments all the time...so I am trying to spend more time looking out the cockpit; as he said, the Instrument rating is a seperate one!) Why is this a good idea? Has anyone else come accross this ? I guess it may be so that I learn to jusdge the AoB, attitude, engine note etc all by feel just as I was told to for cct flying. Am I right?

I guess we don't actually do steep turns for teh full hour because we do work on flying on headings, ordinary turns, the emergency break (last time we flew) and then of course recover back to the airfield practising cx and my instructor is introducing me to different ways to join the cct. So there is a mix there.

Steep turns theory? Well, I sort of understand it about increased weight and load factor hence the 2g; also that one is flying nearer to the stall because of the high aofa of the wings; so therefore full power needs to be used (Lookout, power, roll, attitude, Bank and back pressure - or PRABB is my motto). I nevr was great at Physics so getting my head around this side does strain the grey cells - but am I along the right lines or is there something else which would hel that I need to know?

[BackPacker]

is there something else which would hel that I need to know?

At your skills test you'll be required to either do a 45 or 60 degree banked turn. To nail that angle, simply glance at the artificial horizon while rolling in. There's markings for these angles, but you have to know which ones.

If you find yourself not pitching enough and thus the nose and altitude lowering, don't try to recover by pitching alone. You're too close to the stall for that. Just roll back upright some 10-20 degrees, then pitch up to bring your nose in the proper attitude, then roll back into the turn again.

When rolling into or out of the steep turn, particularly if you're rolling rather fast, don't forget to apply a bit of rudder otherwise your nose will wander all over the place.

I guess that's about it.

Oh, forgot this one: Don't be intimidated. You are the pilot. Fly the aircraft, don't let it fly you. This is one of those maneuvers where a firm grasp of the controls is in order, to let the aircraft do what you want it to do.

[Grob Queen]

Thankyou Backpacker, that is very helpful.

I only found out from my instructor the other day that the markings on the artificial horizon are opposite to what I thought they were...ie 30' AOB is the top notch not the lowest one! So the artificial horizon has become more useful, but I really should use it more, so particular thanks for that tip.

Looking forward to my next flight, I want to put these tips into practise!

[gpn01]

Thankyou Backpacker, that is very helpful.

I only found out from my instructor the other day that the markings on the artificial horizon are opposite to what I thought they were...ie 30' AOB is the top notch not the lowest one! So the artificial horizon has become more useful, but I really should use it more, so particular thanks for that tip.

Looking forward to my next flight, I want to put these tips into practise!

Haven't read the entire thread so apols in advance and don't know much about power flying but are students really taught at PPL / VFR level to fly by concentrating on the A/H ?

[foxmoth]

Haven't read the entire thread so apols in advance and don't know much about power flying but are students really taught at PPL / VFR level to fly by concentrating on the A/H ?

No, the A/H is (or at least should be), used purely for a momentary check that the visual picture is correct.

[flybymike]

No, the A/H is (or at least should be), used purely for a momentary check that the visual picture is correct.
I think the visual picture is always correct. The AH not necessarily;)

[P-MONKE]

Grob:

It's a bit late in the season, but I heartily recommend a trip to your local gliding club on a "good" (thermic) day - 45 degree turns are the norm and 60 is not uncommon, especially in the UK with it's narrow thermals.
BTW, as most gliders don't have an AH, 45 degree bank can be assessed by comparing the horizon to the mounting screws around the instruments which are conveniently at this angle.

I also agree with everyone else about the perception of G: If you're not in control, it feels a heck of a lot more dramatic than if you're flying yourself. :eek:

B2N2: "You should not be doing steep turns for an hour." - yes, it can be quite hard work, but this is not particularly uncommon for a scratching flight! :ok:

[BackPacker]

Haven't read the entire thread so apols in advance and don't know much about power flying but are students really taught at PPL / VFR level to fly by concentrating on the A/H ?

I only said that you would need to quickly glance at the AH to nail the angles. But once you've got the angle and thus the correct picture, there's no need to use the AH anymore.

Other than this, I think the use of the AH is only taught during the 180 on instruments, which is used in case of an inadvertent entry into cloud.

[Grob Queen]

Hi everyone,

To add to the discussion of the use and trianing of the AH. Please bear in mind that my instructors are RAF, so I may be being taught slightly differently to you guys in civvy clubs! For instance I am taught the Emergency Break - not sure what Civvy instructors call it, but I know it does not appear in my civvy manuals!

I am taught teh L-A-I workschedule so obviously the AH comes into that. I do indeed use the AH in steep turns to GLANCE at to check teh AoB. At this stage, I do it to get into my head just what is 45' and 60', obviously, as my proficiency improves, I will use it less (as I am doing with the RPM, as I am getting used to teh sound of the engine). For instance, I do not check teh AH when banking 15 or 30'...think my instructor would frown upon that at this stage! I knoow its all about looking outside the aircraft and visual attitude.

I think, as one of you said, covering up teh instruments when I get more advanced would possibly be a good idea, and I will suggest it to my instructor.

P-MONKE - i admit firstly that I don't know a thing about Glider flying, but wouldn't seeing how steep turns are flown in a glider confuse me for powered flight? Having said that of course, we do also have a Gliding Club on Station and I would indeed like to have a go at a glider at some point for the experience!!

Another twist to this, what are your thoughts on the use of full flap to take off when on a touch and go??? I'll see what you think then tell you what I have been told...:confused:

[BackPacker]

I think, as one of you said, covering up teh instruments when I get more advanced would possibly be a good idea, and I will suggest it to my instructor.

You'll find you don't have to suggest it to your instructor, but he will nevertheless do so in due time. Although he'll probably be covering up the ASI, ALT and possibly MAP/RPM instead of the AH. After all, judging height and speed is far more difficult than judging where the horizon is on a VFR day...

Another twist to this, what are your thoughts on the use of full flap to take off when on a touch and go???

In most aircraft it's not a good idea as climb performance is pretty marginal with full flaps, and you run the risk of "ballooning" due to the propwash underneath the wings. During the "touch" phase of a T&G you should be configuring the aircraft for take-off as per the POH. That typically (but not always) means no flaps or 1st stage flaps.

Remember that a T&G is a pointless procedure in the normal course of a normal flight. It's only used so you can cram more practice landings and practice take-offs in a single session because you're re-using kinetic energy, and don't have to taxi-back. But a T&G is only an effective training aid if you approach it as three separate stages:
1. Perform a normal landing, in the normal landing configuration (or whatever abnormal/emergency landing configuration you're practicing).
2. During the roll, don't brake any harder than necessary to get below flying speed. Now reconfigure the aircraft for a take-off just as you would do at the hold.
3. Increase the throttle and perform a normal take-off (or whatever type of take-off you would be practicing, ie. short-field).

So if you would not be performing a full-flaps take-off from the hold in your specific aircraft, what would be the point of ending a T&G with a full-flaps take-off?

Having said that, there is another procedure which is not practiced as often as the T&G, and that's the go-around. If the go-around happens rather late in the landing phase, you're almost certainly at full flaps. So you're confronted with an aircraft that is descending, is in high-drag configuration and possibly with carb heat on as well. You've got to arrest the descent and convert it into a climb, reduce the drag without losing control and make sure the engine is developing full power. All in a very short period of time. Arguably a greater challenge than a T&G.

[P-MONKE]

Grob Queen: I don't know much about powered flying either ;) I was just thinking about developing your G tolerance so that you will have a slightly lower workload when practising steep turns in a powered aircraft*. After all, a 60 degree well co-ordinated turn will load you to 2g, whatever aircraft you are flying in.

* And it's fun :)

[Grob Queen]

P-MONKE - I see what you mean now, thanks!....I can get the g tolerance/overcoming nausea practice in the back seat without the need to concentrate on flying...although from what the others have said (and from my own experience) its better when you are actually flying!

But with the gliders so close (too close when on one of our runways!!) it makes sense to pop over there sometime and ask someone!

[Grob Queen]

Backpacker - many thanks for your advice. i think is proabbly what most pilots would say. I have indeed been taught to take up land flap and only use t/o flap when on teh t/o part of a T&G - makes perfect sense (and easier as the aircraft is not so sluggish and the angle of climb less shallow...I seem to be virtually skimming the hedge at the end of one of our runways when I t/o using full flap!)

However, since I had a CFI check, he said that it was perfectly ok to take off with full flap on a t&g - it measn there is less work required during the ground roll. However, I ahev never really had any issues with this and when I ahev done three solo T&Gs, I brought land flap up to use just t/o flap and was fine.

Go-Arounds aren't a problem to me....nose up, full power, t/o flap...and I've done a few!!!!

[flybymike]

However, since I had a CFI check, he said that it was perfectly ok to take off with full flap on a t&g - it measn there is less work required during the ground roll. However, I ahev never really had any issues with this and when I ahev done three solo T&Gs, I brought land flap up to use just t/o flap and was fine.


I am surprised if, as a student, you have been allowed to do solo touch and gos, and dumbfounded if a CFI told you to do so using full flap.

[madlandrover]

Nothing wrong with solo T&Gs, staple part of the UK training. Doing them with full flap isn't ideal though, unless on a very long runway...

[flybymike]

Like so much in life, things have changed since my day....

[madlandrover]

:) No worries. I do insist before sending a solo on seeing/manufacturing at least one landing a little deep into a runway where being able to "go" is in serious doubt, to make sure the assessment of go/nogo is there.

[P-MONKE]

Grob Queen:
That's exactly it. Except students always sit up front! ;)

[BackPacker]

I seem to be virtually skimming the hedge at the end of one of our runways when I t/o using full flap!)

And then you probably haven't flown the aircraft anywhere near MTOW yet. (Unless you're flying a 152...)

Pilot DAR knows chapter and verse on this, but I think the certification requirement is that the aircraft is able to climb at at least 100 ft/min with full flaps and at MTOW. But that's in ISA conditions at 0' DA. On a warm day and a slightly elevated airfield you might not be able to climb over the hedge at all.

If the POH doesn't include performance data for a full-flaps take-off, then that's probably because it doesn't give you the best take-off performance.

[foxmoth]

Like so much in life, things have changed since my day....

Not sure when/where you learnt, but I did my PPL in '73 and we did solo T&Gs then!

[Grob Queen]

Flybymike - If you wouldn't have students flying solo T&Gs, how would you want us to consolidate solo circuits??!!

I was indeed surprised when our CFI said that I could do T&Gs with full flap. Hedge hopping when using our short runway 19 definitely does not feel safe! But then who am I to argue with our many-hours-many-types CFI?!

I have only flown form my home airfield so far so have the joy of landaways to come (maybe Kemble for my first one) :)

[flybymike]

Flybymike - If you wouldn't have students flying solo T&Gs, how would you want us to consolidate solo circuits??!!


I didnt say that I wouldn't have it, only that it wasnt allowed in my day. which was 1983 at Leeds (For once I have the joy of knowing that Foxmoth may be more ancient than me) Circuit consolidation was done by full stop landings with back track if necessary. It seldom was, even though in those days Leeds still had a "short" runway.
Having said that I once did more than a few T&Gs when I deduced that the Tower thought I had an instructor aboard. ;)

[Grob Queen]

Well, I'm glad things have changed. The "old" way seems tougher on the student (and on the airframe!). Must have driven other pilots in the circuit mad...good for taxxiing practice though.

[flybymike]

Relatively speaking, in those days there was bugger all traffic at Leeds.