That is, if you don't have scavenge pumps and air/oil separators top and bottom in your engine, as any truly inverted system should.
Quotes and Jokes (9 Viewers)
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Greg Boeser
2nd Lieutenant
And how many WW2 era engine models did?
buffnut453
Captain
Stomp on the rudder pedals, "pudding basin" the control column, and tell Heavenly Father that he has control!
Don't know, but I suspect some Japanese fighters did, as I've read accounts of Zeros and Hayabusas flying inverted for extended periods. The Wright 1820 (out of a T28) we had at mech school had scavenge pumps top and bottom.
ThomasP
Senior Master Sergeant
I found out a few years ago that even modern jets (F-14, F-16, MiG-21, etc) can not fly 0g inverted for prolonged periods. Depending on the airframe, the oil system and/or the fuel system will not be able to maintain supply. In my ignorance of modern aircraft design I had assumed that this problem would have been dealt with, but it seems that it is not really considered a problem? IIRC the F-16 is limited to 30 sec in Mil and 10 sec in AB due to the fuel system, while the F-14 is limited to about 30 sec due to the fuel system. I think the MiG-21 is limited by the fuel system.
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It's not only about the aircraft. Operating under sustained negative G is really uncomfortable for the pilot, and 30 seconds is a really long time. Even an aerobatic routine won't likely have sustained negative for 30 seconds.
ARTESH
Chief Master Sergeant
I have heard this from a Tomcat pilot. He told: "The American Instructors warned us to not do aerobatics, 0 and Negative G related flights, unless really necessary." The reason as he told, was impacts on Pilot's health and machine limits as well.
Just as a Question: Could it also be related to different Roles they have? I mean that Tomcat is not a Fighter like F-5 or not a Fighter-Bomber like F-4. In other word, different designs for different usage.
Didn't you mean "negative one G inverted"? Zero G, whether inverted or upright requires an anti-gravity arc flight profile, which is even more challenging than inverted one G for fuel and lubricant systems, as the fluids tend to float in midair and avoid both top and bottom pickups. In any case the geometry of the flight path and the power of the aircraft severely limit the duration of the zero G condition.
This is really a Biff question as far as modern times, but back in Vietnam days there wasn't much utility in prolonged inverted flight, other than rolling over briefly to scan below. If your ECM says you've got a SAM coming up, it's kind of handy to roll over and try to spot it. The strobe on your screen tells you about what direction to look and you should pick it up pretty quick.
ARTESH
Chief Master Sergeant
ThomasP
Senior Master Sergeant
Hey XBe02Drvr,
F-14D manual, from Fuel System section:
"Zero− or negative−g flight longer than 10 seconds in AB or 20 seconds in MIL or less will deplete the fuel sump tanks (cell Nos. 3 and 4), resulting in flameout of both engines."
"AB operation in the 0 to -0.5−g regime may result in air ingestion into the fuel boost pumps, causing possible AB blowout or engine flameout."
From Prohibited Maneuvers section:
". . .
2. During afterburner operations:
e. Sustained 0 to −0.5g flight.
f. Flight from −0.5g to −2.4g's for more than 10 seconds.
3. At MIL power or less: zero or negative−g flight for more than 20 seconds."
The above is similar to limits for the F-16 which is listed as limited to 10 seconds in AB or 30 seconds in MIL.
Under Prohibited Maneuvers, the F/A-18E,F the manual says:
". . .
1. Zero-g except transient (over 2 seconds between +0.2 and -0.2g).
2. Negative-g for more than 10 seconds (30 seconds required between negative-g maneuvers)."
I do not have any of the numbers for other modern AC handy right now. They are in my notebooks in my storage locker.
F-14D manual, from Fuel System section:
"Zero− or negative−g flight longer than 10 seconds in AB or 20 seconds in MIL or less will deplete the fuel sump tanks (cell Nos. 3 and 4), resulting in flameout of both engines."
"AB operation in the 0 to -0.5−g regime may result in air ingestion into the fuel boost pumps, causing possible AB blowout or engine flameout."
From Prohibited Maneuvers section:
". . .
2. During afterburner operations:
e. Sustained 0 to −0.5g flight.
f. Flight from −0.5g to −2.4g's for more than 10 seconds.
3. At MIL power or less: zero or negative−g flight for more than 20 seconds."
The above is similar to limits for the F-16 which is listed as limited to 10 seconds in AB or 30 seconds in MIL.
Under Prohibited Maneuvers, the F/A-18E,F the manual says:
". . .
1. Zero-g except transient (over 2 seconds between +0.2 and -0.2g).
2. Negative-g for more than 10 seconds (30 seconds required between negative-g maneuvers)."
I do not have any of the numbers for other modern AC handy right now. They are in my notebooks in my storage locker.
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ThomasP
Senior Master Sergeant
I am thinking that we are hijacking the Quotes and Jokes thread, and maybe this discussion about fuel feed ability under 0 or negative g should have a thread of its own??
Would the Moderators move the appropriate posts to a new thread??
Would the Moderators move the appropriate posts to a new thread??
ARTESH
Chief Master Sergeant
That was an interesting discussion for me! learnt some new things. Thank you.I am thinking that we are hijacking the Quotes and Jokes thread, and maybe this discussion about fuel feed ability under 0 or negative g should have a thread of its own??
Would the Moderators move the appropriate posts to a new thread??
SaparotRob
Unter Gemeine Geschwader Murmeltier XIII
Panic?
MIflyer
1st Lieutenant
Not only that, but all the stuff they dropped when they were doing PDM at the Air Depot tends to come falling down and fill up the canopy. Nuts, bolts, screws, bits of wire, screwdrivers, wrenches, watches, cigarette butts, ham sandwiches, used condoms, small pets, the owner's manual for a 1976 Volare, you name it.
At OC-ALC they considered installing a removable fabric floor in the A-7D to catch all that stuff.
As for the Spitfire's "unable to push over" carburetor, there were two problems.
1. Simply shoving the stick forward forced all the fuel in the carb float chamber upwards, preventing the engine suction from drawing it from the bottom of the float chamber. This was called the "lean cut." This was fixed by adding a standpipe to the float chamber, thereby giving a path to allow the engine to draw fuel from both the top and bottom of the float chamber.
2. While the engine was not drawing fuel from the float chamber, the float, which had floated up along with the fuel, opened the valve and allowed still more fuel to come into the chamber. When the negative G situation ceased this excess fuel caused a much too rich mixture and the engine power suffered accordingly. This was the "rich cut." The fix for this was devised by a female engineer, inserting an orifice in the line to limit how much fuel could get into the carb.
3. These two fixes were merely stopgaps. The ultimate fix was to Buy American.
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Lucky13
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Snautzer01
Honourably banned
- 43,349
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ARTESH
Chief Master Sergeant
Never watched a F1 or any other sports from TV! there are 2 channels for sports in Iran, IRIB Varzesh and IRIB 3, But only broadcast Iran's Football games or Very important European Football Games! I've leant more clubs from PES / FIFA PC games rather than our own TV! For Olympics and World Cup, No Opening or ending ceremonies are shown! nor every single game! Only Iran's or very important ones! and all of these are only men's games! Women's games are never shown! nor you, as a male, can enter their games, as spectator!
