Pilot G-limit compared to the Bf 109 and Fw 190

I'm going to end this rubbish.

 

The G effect from the incline in these WW2 fighters is infinitesimal. The Incline in F-16 was only about 1G, so no 109 or 190 is going to be getting 1.5 or even 2 G out of this. Crumpp, it is hard to believe you don't know this.

Great and very informative post Ark', but I think you would also need to look at the leg position, not just the seat position effect on g-tolerance.

I'm going to end this rubbish.

 

The G effect from the incline in these WW2 fighters is infinitesimal. The Incline in F-16 was only about 1G, so no 109 or 190 is going to be getting 1.5 or even 2 G out of this. Crumpp, it is hard to believe you don't know this.

 

But lets cease with the angle mongering and just cut to the actual date:

 

 

I measured the inclines of the two seats, and in the 190 you have about 20 degrees to the P-51s 14 degrees. Pilot posture would alter this in meaningless ways. At 20 degrees, you brain blood pressure would be so low as to make no meaningful difference in G tolerance.

 

"In a study in which 250 centrifuge runs were made on human volunteers, it was demonstrated that systolic blood pressure in the radial artery held at eye level was reduced by 32 mm of mercury for every G added to the ± G2 force. Visual disturbances occurred when the systolic blood pres- sure at the base of the brain was reduced to 50 mm of mercury and complete loss of vision occurred when the pressure was reduced to 20 mm of mercury. Loss of consciousness occurred when the systolic pressure at brain level was reduced to zero. This would be equivalent to a five ± G pull, i.e., 5 x 32 = 160, where the blood pressure at the base of the brain would be reduced to zero if the systolic blood pressure in the subject was 160 at the heart level."--historic.aerobatics.org Eoin Harvy, MD.

 

Complete loss of vision occurs at a brain BP of 20. COMPLETE LOSS. So you would need at least 35 degree, double what is shown here, to get even a single solitary G of tolerance.....and you would be on the very edge of a complete blackout. So no, you are not going to get 1.5 to 2G of tolerance from this. And in order to pull the 6.5 to 7 G posted earlier, you would need to have a angle of 45 degrees....

You most certainly can get some significant G tolerance out of pilot seat position.

I would welcome an intelligent mature discussion and thank you for posting. I think it would benefit the community.

I think I have this report. You are absolutely right and the data is correct but can you link the entire report so all can examine the details.

It can be deceiving without the onset rate and disposition of the test subjects.

I have multiple reports on pilot G-resistance so we can "get to the bottom" of this to see why every modern fight designer considers seating position effect on G-tolerance.

You will have excuse me though for the next few days. I am at the frontside of a 4-day and will be home from work till the end.

Great and very informative post Ark', but I think you would also need to look at the leg position, not just the seat position effect on g-tolerance.

How big is the distance between the lower and upper pedals on the 109 and 190? I can't imagine it being large enough to have a massive effect, but even the ability to pull an extra 0.1G helps in combat.

I don't think there is a lot to talk about in case of WW2 aircraft though, differences between 190 and 51 are very little and so there will be practially no difference between pilot's G force handling. And adding to it that American pilot would have a G-suit, which was becoming common in 1944 for Mustang pilots, shows that its the P-51 that should be better at high speed maneuvering.

Great and very informative post Ark', but I think you would also need to look at the leg position, not just the seat position effect on g-tolerance.

And as my pic's shown, the p51's pilot and 190's pilot leg position are near identical.

NATO round up of High Physiology research:

RECLINED SEATS

As one factor determining blood pressure at head level is the vertical height between the head and heart, reclining the seat back away from the vertical will result in greater

blood pressure at this site.

Crossley and Glaister (71) studied back angles of 70, 45, 30, 25, 20 and 15 degrees from the horizontal. At 70 degrees from the horizontal, GOR and ROR tolerance levels, determined by PLL, were 4.5 and 3.3 G, respectively. The tolerance levels were 7.3 and 5.7 G, respectively, at 15 degrees. The grey-out threshold was found to be proportional to the inverse of the vertical eye-heart distance (distance calculated as the sine of seat back angle

from the horizontal) and the threshold was significantly improved when the back angle was 45 degrees or less from horizontal. Wearing a G-suit further increased relaxed G

tolerance even though the thighs were positioned above, and the heels positioned level with the hips. This action may have been due to an increase in peripheral vascular

resistance. It was concluded that the near supine position with a G-suit can provide relaxed thresholds between 6-8 G while permitting adequate forward visibility. Bums (31) found no difference in G tolerance between the control seat back angle of 13 degrees from vertical and 30 degrees. At 45 degrees from vertical, tolerance increased by 0.5 G. At 75 degrees, the tolerance of 8 G represented a 100% increase over the control level. The

thighs and legs were below hip level. Heart rate and the intra-thoracic pressure required to maintain the visual field were decreased with greater seat back angles. Tolerance

was again highly correlated with the inverse of the eye aorta distance.

 

A reclined seat produces a greater +GX component on the body with greater respiratory difficulty during G, therefore Glaister and Lisher (98) used PBG to help raise the anterior chest wall. With a PBG schedule of 5 mmHg/ G to 35 mmHg maximum, the relaxed grey-out threshold of 3.49 G in the conventional seat was increased to 4.89 G with the seat angled 65 degrees from vertical. As found earlier, the addition of the G-suit increased G threshold and

each increment of pressure in the G-suit schedule added protection. The normal expiratory reserve volume at 1 G was maintained at 4 G with PBG, suggesting that a similar

work of breathing was restored. Gillingham and McNaughton (87) used visual field limit tracking during relaxed GOR profiles to 7 G. Complete visual loss occurred at or near 5 G when the seat back angle was 13 degrees from vertical. At 45 degrees, there was complete visual loss at or near 6 G. When the seat back was at 65 degrees, substantial vision emained at 7 G.

Glaister and Lisher (100) utilized a psycho-motor performance test with a high motor demand to assess the benefits of inclination to 60 degrees from the vertical compared to 17 degrees. With a pressurized G-suit and PBG at 5 mmHg/G to a maximum of 40 mmHg, performance at 6 and 8 G improved in the reclined seat, equivalent to 1 -2 G of additional protection. Heart rate was similar at 8 G reclined compared to 5 G upright.

Following-up with a psycho-motor test with greater mental effort, Lisher and Glaister (140) studied seat back angles of 17,52, and 67 degrees from vertical. Compared to the 17 and 52 degree positions, 67 degrees raised the acceleration level at which a performance decrements occurred by 1.4 G.

Glaister (92) reviewed published data on the effect of seat back angle on G tolerance in relaxed and unprotected, protected with G-suit only, and G-suit with straining or PBG conditions. G tolerance in each condition was described by a different mathematical relationship but all were proportional to the inverse of cosine of the angle of seat back and the G vector. Independent of the condition, the regressions predicted that seat back angles of 58, 69 and 74 degrees would deliver 1, 2 and 3 G increases in grey-out tolerance, respectively, compared to the upright seat. Tolerance would be further increased by 1.21 G with the G-suit and by 3.15 G with full protection from the Gsuit and straining or PBG.

 

Burton and Shaffstall (49) measured increases in endurance time of 38, 98, and 218% in the SACM profile when the seat back angles were 30,55 and 65 degrees from

vertical, respectively, compared to the control value at the 13 degree position. Heart rate 120 seconds into the profile was significantly less at the 55 and 65 degree angles.

Cohen (64) reported that seat reclination to 75 degrees increased relaxed G tolerance by 3.12 G. If used with a Gsuit and/or straining maneuver, reclination offered the

same increase in protection.

 

Bums and Whinnery (35) radio-graphically measured the hydrostatic distance between the eye and aortic valve at seat back angles of 30 and 65 degrees from vertical, each posture with a headrest geometry of 12,25 and 45 degrees up from the reclination line. Relaxed G tolerance significantly correlated with the inverse of this hydrostatic distance.

While headrest geometry had no effect on G tolerance at a seat back angle of 30 degrees, lowering the head from 45 to 12 degrees at the 65 degree back angle, increased mean tolerance by 1.7 G. Nelson (155) has calculated that the aortic valve is the most appropriate

reference position for the hydrostatic theory of visual blackout.

G tolerance is significantly improved with seat reclination beyond 45 degrees from the vertical but the position causes practical problems (17,192) of vision difficulties and breathing impairment, and would require a rc-dcsign of the cockpit. PBG could alleviate the respiratory problems.

In summary....

0-15 degrees incline is considered vertical seating with little to no effect. Think about it...nobody sits a 90 degree upright seat even at most dining room sets. :smilewink:

16-30 degrees was found to be a good compromise between G-tolerance effects and degradation of the pilots vision and breathing found at high incline angles.

30(+) resulted in vision scanning impairment and breathing difficulties

Only one report found no difference between 13 degrees and 30 degrees. The other reports list noticeable effects due to seat angle and all found a similar mathematical relationship. A function of the vector resolution over the distance from the eyes or brain to the heart.

The basic relationship is approximated by the inverse of the cosine of the angle and the G-load. Using the 14 degree and 25 degree found by ARKROYAL measurement of internet drawing, I technique I do not recommend for gathering data...

That is proportional to 7% at 1G and 40% at 6G as noted by Burton and Shaffstall.

As for leg elevation:

PELVIS AND LEGS ELEVATION

In addition to investigating various seat back angles, Voge (191) measured the effect of changing the position of the legs on PLL threshold. At a seat back angle of 45 degrees from the vertical, and the thighs at 59 degrees from vertical, there was no difference in G tolerance, 6.3 compared to 6.5 G, when the lower legs where at 115 degrees

from vertical or hanging vertically, respectively. The addition of a G-suit increased the G tolerance in each position, in agreement with other findings (71). The greatest G tolerance, 11.1 G, was obtained with the seat back at 75 degrees and the thighs resting on the chest

("fetal" position), however this posture produced complaints of tiredness, pressure on the chest and legs, and general discomfort.

Approximately a 0.4 G increase in relaxed grey-out threshold can be achieved by elevation of the feet (172). This is believed to be a result of decreased vaso-dilatation and veno-distension in the lower legs. Others suggest that elevation of the feet has no anti-G benefits (42).

The data is divided. Some show a benefit while others do not.

http://ftp.rta.nato.int/public//PubFullText/AGARD/AG/AGARD-AG-322///AGARD-AG-322.pdf

Dirkan Says:

Hello there!

 

I found that the blackout limit (where the pilot starts to black out) is around 5 Gs for the P-51D, 6.5 for the Bf 109 and 7+ for the Fw 190.

 

I find this to be a bit unfair... If anything, they should be at the same level, considering they're still humans in the cockpit. Any probable reason as to this, or is it just overlooked?

Dirkan,

The results are absolutely believable.

The results of a completely upright pilot without an G protection could withstand 15G's without blacking out while a 30 degree incline pilot blacks out at 5 G's is also possible.

You are missing the most important factor...ONSET RATE. Without it, the claim:

I found that the blackout limit (where the pilot starts to black out) is around 5 Gs for the P-51D, 6.5 for the Bf 109 and 7+ for the Fw 190.

Is totally meaningless. :(

Lastly, the G-suit effects are also listed in the report I posted. Early Anti-G protection ran the gamut from meaningless to effective.

Finding some good data on the USAAF G-suit protection results vs Onset Rate would be very good.

Crummp: Are you sure you are reading your data correctly? From what you yourself posted, I am reaching a whole different conclusion. The numbers alone don't match anything that we have in any of the WWII birds. (with regards to the seat angle and leg position)

You are correct...the details matter. I draw my conclusions after examining the reports. Understand too that onset rate, pilot disposition (relaxed, trained, untrained, etc), and equipment also matter.

Most importantly, the mathematical relationship is applicable. The 40% I listed is not an absolute but an illustration of the general mathematical relationship.

It is also not threshold but endurance. Two different things but can lead the casual observer to the wrong conclusion. Although both pilots may pass out at a 5.5G threshold at a given onset rate, the fact one can endure it longer won't make much difference to the average player. He will just note that one pilot passed out and the other did not.

Onset rate changes everything, the details matter, and seat inclination is important to G-tolerance. That is the generalization the studies show us. It is not as simple as "seat inclination = X number it G increase under all conditions".

That is why fighter and aerobatic aircraft designers pay attention to seat angle.

I hope we hear from Yo-Yo on this matter. It still seems to me that the discrepancy between the G limit tolerances is way too large between the different aircraft.

I hope we hear from Yo-Yo on this matter. It still seems to me that the discrepancy between the G limit tolerances is way too large between the different aircraft.

I would welcome it too. The original posters assertion is meaningless without more measured data.

I think we need to present that measured data, draw a conclusion, and then submit a bug report if necessary before we ask Yo-Yo to drop working on other things we need like maps and more aircraft (like my P-47 :smilewink:).

I personally would like to know more details and find the original documentation on the USAAF G-pants.

I have gazed the topic with real interest... :) so many theories, such a long discussion.

But did somebody measure the GLOC for the planes IN EQUAL conditions - 2-4g turns for both before the test, descending spiral to maintain 5-6g for a sustained turn, etc?

 

The point is that all WWII planes now have no G-suit. P-51 initially had but it was removed to place the planes in equal positions in MP.

Thanks for taking the time to clarify, much appreciated.

I have gazed the topic with real interest... :) so many theories, such a long discussion.

But did somebody measure the GLOC for the planes IN EQUAL conditions - 2-4g turns for both before the test, descending spiral to maintain 5-6g for a sustained turn, etc?

 

The point is that all WWII planes now have no G-suit. P-51 initially had but it was removed to place the planes in equal positions in MP.

Thanks Yo-Yo! Good to know about the USAAF G-suit.

Whoever test's this, please make a track and if you record the time from 1g to peak g-load we will have the onset rate too.

The point is that all WWII planes now have no G-suit. P-51 initially had but it was removed to place the planes in equal positions in MP.

If this was about balance then why is the 67"hg P51D going up against late 1944 BF 109 K4 and FW 190D9(with EZ42 gunsight)? :huh:

I have gazed the topic with real interest... :) so many theories, such a long discussion.

But did somebody measure the GLOC for the planes IN EQUAL conditions - 2-4g turns for both before the test, descending spiral to maintain 5-6g for a sustained turn, etc?

 

The point is that all WWII planes now have no G-suit. P-51 initially had but it was removed to place the planes in equal positions in MP.

I only wonder how does this "balance" a thing.

So a plane that is slower, turns worse, climbs worse and is planced with both late war limited production German aircraft, is striped from its one real advantage that it should have regardless of balance!

First you say that planes are not made to be balanced and that I should deal with my 67'hg Mustang against most rare versions K4 and D9... now you say its balanced out by taking out the G-suit? The historical equipment used by allied pilots? Great. Cool. Thx for update YoYo.

If we had G6 and Fw190A8 I would be fine with it. I would say, yeah june 1944, not all units had it... but against those two monsters?!

It balances the G-limit, which is the topic here.

Fine, be it your way. I've just said that its unfair towards the plane, and the principle of the game not beeing balanced and its up to the mission maker to balance it out. But ok. I am wrong this time I guess.

Now that I know the G-suit was removed, I will be putting in a feature request to make it an option like the MW-50 fuel and such. I like options.

Making it an option is a great solution.

Add to that list, high octane gas, gunsight, max manifold, and post WW2 weapons. Easy peasy:music_whistling:

Mustang turns better in the region of instanteneous turns where G-suit gives it an additional benefit. G-suit does not help in the region of sustained turnes where -51 is worse than 109 and almost equal to Dora.

Yes, I know that, thats exactly what I mean. P51 is a worse turner(because of sustained turn), having ability to pull more Gs without G suit negates itself and gives very little if no advantage to the Mustang, and thats the point. In any other aspect the plane is inferior, so why make it less superior in the one thing that it actually does better?

If the pilot can't go over 5G for a sustained G, that means that the 109 having worse high speed turn can follow it as I have to loosen the turn not to black out and 109 is going to gain on me at that time. Its only useful in scissors, but I can't just make a wide over 5G turn. This means that we emphasise the 109's sustained turn advantage and take away from the P-51's instantaneous turn advantage.

Basically the one thing Mustang has better, that beeing high speed maneuvrablity is impaired by the lack of G resistance. Especially taking into consideration that 109 pilot is not getting tired with heavy stick forces in the game, so he can do it all day.

I agree with Sithspawn, if the code was already there, it could be very well an option. Its also historically correct for the P-51 pilots in 1944 especially late to have those G suits on.

We should probably hold off on comparing the BF-109 with the P-51, till after the update. The BF-109 is getting a more refined flight model. Once we have that flight model, it will allow us to better assess our future Mustang tactics against the K4 and visa versa, sans the G Suit and all. :thumbup: MJ