Aces High Bulletin Board
General Forums => The O' Club => Topic started by: AquaShrimp on April 16, 2007, 08:13:47 AM
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I've seen B-1b bombers do rolls at airshows before. What is the g-limit on these aircraft? I think one also did a loop one year at an airshow, but I couldn't tell for sure. I know it did a vertical climb of about 15,000 feet from the deck.
For a bomber almost the size of a B-52, the B-1 sure is an amazing aircraft. Early models were more than capable of flying at mach 2+, but this was limited by redesigning the air intake to be more stealthy. Mach 1 is still achievable on the deck though.
Theres talk of updating the B-1s, which use the same engine as the F-16, with the engines of the F-22. This would double the non-afterburning power of its engines (from 14,000lbs of thurst in mill to 29-33,000 lbs).
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A loop or a roll doesn't take a tremendous amount of G's.
(http://www.707sim.com/images/texrole.jpg)
I would venture a guess that the B1 could pull 7 or 8...
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Wow, 7 or 8gs, thats pretty good for the old B1b! Especially since the F-14 could only pull 6.5gs. But then again, the air force knows how to build'em.
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Just out of curiosity....what is the G limit of the human frame?
I was under the impression that todays fighter aircraft could hold out for longer than thier pilots can under G load.
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Depends on duration.
9gs leads to unconsciousness in about 10 seconds.
20 to 40gs can be withstood for less than 1 second.
200gs have been withstood for milliseconds (though the retinas may temporarily detach causing blindness for several hours).
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The F-14 has little canards that extend at ss speed to unload the tailplanes so that it can pull up at 7.5G at mach 2. 6.5 G is the amount it can hold in a consistant turn without flow seperation.
I've pulled 4 in a Citabria and that wasn't close to design load.
In order to race at Reno, Unlimited warbirds have to be certified to be able to pull 6 G's.
7 or 8 is not out of the question on the design board. I would say the B1's standard flight envelope is a bit more conservative.
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Tex pwns. That is "the Barrel roll, of Barrel rolls".
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I don't think the "bone" can pull that many G's. I do know that overseas the pilots "over G" the air craft all the time wich causes many many head aches to the mait. crews.
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If I had to *guess*, I would say the Air Force puts the g-limit at 3.5 or 4 on the Bone. The Russian version, the Tu-160, which is a gargantuan airplane, is limited to 2.5gs. But I've seen the Bone do some intense maneuvers at airshows.
Old duke cunningham (crooks don't get their names capitalized by me), pulled either 12 or 14 gs in his F-4 and broke the flap hinges. The F-4 is only rated at 8gs I believe.
Eagle, our resident F-15 pilot, said he once over-g'ed his plane. He said he had to pull all kinds of panels off the plane with the groundcrew to check for damage (translation: he ate icecream sandwhich after icecream sandwhich while relaxing underneath the wing while they checked the panels).
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Shrimp you a funny guy :)
A B-1 is limited to about 3 Gs. A B-1 would probably break up if the pilot attempted a loop (a loop in a B-1 would probably require 4-5 Gs and the plane would accelerate extremely quickly on the backside) but a roll would not be a problem at all.
As for human endurance, a properly trained person can withstand 9 Gs for significantly longer than 10 seconds, however it is very fatiguing and not a healthy thing to do. With proper anti-G equipment, 9 Gs can be held for quite some time.
Anytime you're over about 4 Gs there is some risk of injury, and above 9 Gs there would be significant risk of injury (broken bones, soft tissue damage, burst blood vessels, etc) especially if it was sustained more than a few seconds. I blew out a disc in my lower back (L5-S1) very early in my flying career even though I was flying the F-15E which is not exactly a high-G sustaining sort of aircraft like the F-15C, F-16, or F-22. Many fighter pilots I know have some some sort of back injury as a result of their flying career.
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Originally posted by AquaShrimp
Wow, 7 or 8gs, thats pretty good for the old B1b! Especially since the F-14 could only pull 6.5gs. But then again, the air force knows how to build'em.
b1b aint old
http://youtube.com/watch?v=idtPVZsC0A0
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Depends on your definition of old. Its 25 years old, thats old for a warplane.
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http://youtube.com/watch?v=idtPVZsC0A0
not a loop but...
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When the 707 came out way back when one of the test pilots did a roll with it when it did an over flight of some buyers. I think the guy lost his job but I bet it was a heck of a ride.
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Holy 757 did you see the video after the inverted B-1B you posted?
http://www.youtube.com/watch?v=fYZOByowrlU
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The 707 roll with interview.
http://www.aviationexplorer.com/boeing_707_roll.wmv
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Thanks for posting that wolf, good to know the guy didn't end up losing his job.
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Originally posted by LePaul
Holy 757 did you see the video after the inverted B-1B you posted?
http://www.youtube.com/watch?v=fYZOByowrlU
I saw an RNZAF 757 do that high speed pass into a near vertical climb manoeuvre at an air show a couple of years ago. As it got slower and slower and topped-out I was half way expecting to see a hammerhead on the end of it...but it levelled off, although it looked pretty mushy.
Judging by the way they throw their 757's around I think the RNZAF are missing not having the nimbler faster toys
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Gs are not all in all bad,
I have pulled 7gs max in the Pitts and -4 which translates in to -5 when you calculate the fact that you start out at +1. I make it a point to stay within the G limits of the aircraft for obvious reasons. And only occasionally hit these limits mistakenly.
Not sure if the military builds to the same specs, but the General Aviation G rating is such that it will allow for a 1 1/2 times the Gs before some kind of potential structural failure.
So in the pitts that is rated for +6 , -3. The structure was rated at 6, -3 because at 9 and -4.5 Gs something failed.
As for the Gs while rolling, if done right they should be all positive and not exceed 2gs.
For a loop it is not necessary to pull more than 3.5 to 4 gs all of which are utility category numbers.
The problem is, FK up the loop or roll and you could find yourself over G very quickly and that is a big problem.
You also have to look into high G cycles and the materials being stressed. Many of the military aircraft out there that have aluminum spars etc have a set number of G cycles and after that the aluminum is weakened to the point of failure. Do a search on Beech T34s and wing spar failure.
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I was thinking the Pitts was rated for more than 6gs. Kinda disappointed now. I believe Patty Wagstaff has pulled 12 or 13 gs in her Extra 300.
Yeah, aluminum has what is known as a fatigue memory. It is permanently weakened after its specifications are exceeded. However, the Soviets used to add some type of rare earth element to their aluminum, to make it stronger for aircraft use.
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Mine is a 2B, I believe the 1s have a bit higher G rating. While many of the components can take more Gs it is what they certified it at. What are you disappointed about? It still does all the maneuvers. :aok I have flown an Extra 300 and the Pitts S2C comes closer to it with the stiffer wing.
BTW the extra is only rated and certified for +/- 10 Gs
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At 10gs, is it even possible to keep your eyes focused on a g-meter? Extra 300s dont have flight control computers, so it would be up to the individual pilot to limit themselves.
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You have to remember these are not sustained G loads. If they hit 10 Gs, and they do, it is only for a couple of seconds. But it still takes it's toll.
I know a guy who flies an Edge 540 and when he comes down his G meter is usually +10 -9 and when you look at him his eyes are all red and watery etc. The negatives at that level are what really hurt, or so I am told. :) I know -4 is uncomfortable but not a big deal, unless your doing back to back outside maneuvers.
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Originally posted by Bluedog
Just out of curiosity....what is the G limit of the human frame?
"in the verticle axis...83G known to produce fatal incapacitation". This is a comment in a F-16 mishap investigation report from November 2006.
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Originally posted by Holden McGroin
A loop or a roll doesn't take a tremendous amount of G's.
(http://www.707sim.com/images/texrole.jpg)
I would venture a guess that the B1 could pull 7 or 8...
God I HATE the sound of axial-flow jet engines:furious
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A roll in a 707 is only 2G 's