Forum: Air Force Life

Oh, and my last few years in the service (got thrown out, who knew 30 years is all they allowed) I got to play with EVERYTHING in the Air Force inventory. To those that have limited their experience to the fighter regime; play a bit more attention to your brethren in the bomber service. I've seen a bomb load out on a BONE that would shame many a Viper load out. Yep, they're that quick out there! Whether your wings swing, are fixed or warp (have you seen the a$$ end of that B-2 wiggle, weird) it's great to play with jets; the ultimate big boy toy!

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The museum here has a squadron bird from UH. Yellow checkerboard tail. Can't make out squadron, it's dark when I go to work. I'm sure the UH folks know the squadron.

Ahhhh--- but could a Vark beat a Thud at a low-level all-out speed contest??????

I had (maybe still have somewhere) an old scratchy photo of an F-111 flight test airplane instrument panel. It shows 890 kts at 3500 ft. level flight. Could a Thud do that?

Redline airspeed for all supersonic fighters is somewhere in the vicinity of 800-820 KIAS. This is due to air loads on the jet. The Vark and Thud are no exceptions. Besides, 3500' ain't low altitude!! To answer your question, I suspect that a Thud could do that. That was one FAST jet down low--and the only thing that could even approach it at low level is a 'Vark.

Didn't say 3500 was low altitude. It just happened to be the test altitude at the highest airspeed I could find from an F-111.
If the F-111 can do 890 at 3500' it can do 890 at SL. No significant difference in air between 0 and 3500. 890 at 3500 is a higher mach number also.
Red lines are not set by airloads on a jet. On an F-16 for example, wing and fuselage loads at 800/SL are significantly lower than at 600/SL. What sets the limit is the USAF spec. The contractor flight test proves that spec can be met safely. The airplane could possibly go faster safely, but unless the USAF pays for it, no additional flight test is done to verify it.

I do know that the last military jet to hold the low-level speed record was the F-4. Later, a civilian F-104 attempted to break the record, but could only do it in one direction. It actually outran the Rhino, but broke and never completed the required opposite run.
I for one would love to have seen both the Thud and Vark go all-out balls to the wall and settle once and for all which jet is the fastest down low. I have no doubt that both could outrun the F-4.
Please enlighten me--how can air loads on the same jet be lower at 800/SL than at 600/SL, assuming all other parameters to be equal? Inquiring minds want to know.

Certainly the air load from drag will be higher at 800/SL, but that is such a trivial load for the structure, that it isn't even considered when determining the thickness of skins, spars, longerons, etc. Maneuvering loads from turns, rolls, sideslips, etc. are not necessarily highest at the highest airspeed. For example, take an F-16 in a 9g turn at 600/SL compared to 800/SL. Total lift is the same, Gross Weight x 9g. But the distribution of the lift (wing, fuselage, tail) is quite different. As speed is increased beyond 600 kt, wing twist reduces the wing angle of attack and wing lift. Since total lift must stay the same, the airplane angle of attack increases a small amount and the fuselage lift increases. So you have reduced wing lift and increased fuselage lift at 800 kt.

The actual structural load on the wing and fuselage is the sum of lift and inertia. The wing inertia is wing weight x 9g and the fuselage inertia is fuselage weight x 9g, both acting down. Wing lift (up) is much larger than wing inertia (down), so at 800 kt, total wing load is reduced. Fuselage lift (up) is much less than fuselage inertia (down), so total fuselage load is also reduced at 800 kt.

I have neglected the horizontal tail lift effects for simplicity - it changes things a little, but not the concept. Also not included is the effect of the wing lift shifting inboard, which reduces wing bending moments at 800 kt.

Not all component loads are reduced at 800 kt. Horizontal and vertical tail maneuvering loads are maximum there.

This is a simplified explanation of a very complex topic, but I hope it clarifies things a bit for you. I appreciate your interest and your question.

Bottom line

Nothing faster down low than an F-111F (without pavetac)

Get over it Twisted Evil

http://www.youtube.com/watch?v=6OWlEDzjk2s

Thanks for the link VarkVet,I'm a big fan of the Vark and still stop whatever I'm doing to watch these impressive aircraft fly over [which is most days]....Pity we [Aust] will put them down in 2010 Bang Head

......Do you guys have any still flying for air shows,displays etc.?...Down here the dump and burn [especially multiple aircraft] is always a show stopper!!! Is there any other aircraft, past and present, that can safely do this??

I remember working FB-111a's at Pease. kinda a love-hate relationship. Loved getting them airborn, hated them on the ground.
I actually had a code 1 flight that turned into a code 3 flight for a mouse in the cockpit...... Never try signing that off by putting "Installed cat" some DCM's dont have a sense of humor.

Last edited by VarkVet on Aug 06, 2007 - 07:48 PM; edited 1 time in total

Quote:

Do you guys have any still flying for air shows,displays etc.?...Down here the dump and burn [especially multiple aircraft] is always a show stopper!!! Is there any other aircraft, past and present, that can safely do this??

No we don’t have any still flying … the USAF got rid of them because nacelle former cracks were starting to develop in the older models. F-111s were also maintenance intensive, and maintenance expensive. The Aussies are famous for the dump and burn. The only USAF dump and burn that I recall (because it made the British news papers) was an incident over Milton Keynes (don’t know time frame) either late “80’s or early 90’s when an E from Upper Heyford had an IFE and had to dump fuel. Since he was at a lower altitude he decided to torch the fuel dump off so it wouldn’t hit the ground. The Milton Keynes newspaper reported the incident as “American Bomber Explodes over Milton Keynes” Laughing

Most modern day jets will not have the dump mast between the engines ... for safety reasons you can not hot pit Rolling Eyes

The -111 will always be one of the coolest birds ever to become operational. Sure there was controversy, which is ever present anytime you bolt, rivet, glue, or mate that many pieces of metal together with all the electronics, hydraulics, mechanical, pneumatic, etc., systems, components, and materials as any jet aircraft has. The guys that crewed the -111 which I have spoken/worked with were/are 100% in support of the bird as a great platform for its mission profile. I am a stinkin civvie, but am an aerospace professional and have worked countless hours in direct support of military flight operations in many regions. Sure the -16 is a great air superiority bird with top notch ground attack credentials also, I only mention this as local GD/FW kinda guy. I would love to go on holiday to Amberly just to see/feel the -111 poking holes in the sky again. No tears, too many neat birds for that, just think the -111 was/is a Sierra Hotel in my book. Clear, Blue and 22 to [Link pending approval]

http://www.f-16.net/modules/Gallery2/ga ... alNumber=2

Forum: Air Force Life

Wing sweeper