Fuel feed and negative G, worldwide.

[XBe02Drvr]

I would add, that I've flown zero-G arcs in training in float-carbed Beechcrafts, Cessnas, Grumman Americans, Mooneys, and Pipers, and in a T-28A with nary a missfire or engine sputter.
It's a great orientation and confidence-building maneuver for students. (Properly supervised and properly done, of course!)
Cheers,
Wes

 

[greybeard]

Wes,

thanks for your comments. I guess postwar float-type carburetors did have some significant improvement in respect of earlier ones. Unfortunately, there's still a lack of knowledge, IMO, about this not negligible aspect of WWII aerial fighting. Our discussion have at least raised some hint, like "well documented" Dutch complaints about D.XXI powerplant and mention about Russian pilots having similar problems. At same time, it seems that maneuvering so to avoid negative G cutout was second nature for period aviators - which looks logical - and perhaps explain why it's so hard to find such kind of comments. Nevertheless, I think would be interesting to have routinely more info - maybe extracted from relevant manuals - about fuel feed of each aircraft, its limits and features.

Cheers,
GB

 

[Venturi]

Negative Gs are very hard to tolerate for pilots. I think that is the real reason you don't hear much about it. I understand -3g will cause a red out, but it becomes extremely uncomfortable long before that.

The physiology behind this is pretty simple. Unlike positive Gs which pull blood from the blood vessels in the brain and prevent blood coming from the heart to travel to the brain, which deprives it of oxygen... negative Gs cause engorgement of the blood vessels in the brain as it prevents blood from leaving it, and accelerated blood traveling to it from the heart in addition.

The brain autoregulates the tone of the cerebral vasculature to prevent the higher blood pressure from bursting the vessels and causing a stroke, up to a point. But rapid onset of negative Gs overcomes this mechanism, and -3G is too powerful enough in any case to prevent the effects.

Imagine having a blood pressure of 275/200 primarily effecting your head, and you can see why negative Gs aren't popular.

 

[XBe02Drvr]

On the other hand, exhibition and competition acro pilots often get addicted to the "negative G rush" and get a kick out of it.
I find negative one G (inverted flight) mildly uncomfortable to begin with, but distressing if prolonged. Experienced -2 1/2 G briefly once in the back seat of an F-4 that was forced to level off abruptly from a max performance climb due to an air traffic conflict. (Clueless civilian blundering into the control zone) Not real pleasant. Banged my shins on the instrument panel, pinned my hands to the canopy, my helmet hit the canopy, I got an instant headache, and my vision went clear - rosy - pink - RED. Just like that. If I'd been flying, I doubt that I'd have maintained control of the aircraft. When I got myself back together I could hear the pilot chuckling. Apparently we had passed about 500 feet under a very surprised Bonanza pilot.
Cheers,
Wes

 

[Venturi]

Yep, not good for retinas, either...

 

[XBe02Drvr]

Maybe that's why I've got glaucoma now!?