Max Q
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In Flight Refuelling Question

Mon Jul 29, 2013 5:45 am

Can Military Aircraft be refuelled in flight to a higher maximum weight than allowed for take off ?
The best contribution to safety is a competent Pilot.
 
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moo
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RE: In Flight Refuelling Question

Mon Jul 29, 2013 10:27 am

Yes, it happens all the time with the B-52 et al.
 
nomadd22
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RE: In Flight Refuelling Question

Mon Jul 29, 2013 10:52 am

Takeoff weights are often restricted by runway length and other factors. Refueling right after takeoff lets you operate from bases that couldn't handle MTOW ops.
I'm not familiar with 52s. Can they operate at higher weight than they can take off at from any runway, or would they just need a three mile long runway at maximum?
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studedave
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RE: In Flight Refuelling Question

Mon Jul 29, 2013 7:45 pm

I have seen this not only with B-52s, but also with jets (mostly F/A-18s) off of aircraft carriers.
It's one reason I think that 'replacing' the A-6 with lawn darts was a bad idea...
With the Intruder you could carry a lot of everything.
With the Hornet you carry fuel or the stuff that goes boom.
You don't get both. (and Hornets like fuel)





StudeDave
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Legs
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RE: In Flight Refuelling Question

Mon Jul 29, 2013 8:22 pm

Quoting moo (Reply 1):
Quoting studedave (Reply 3):

Are any of those cases actually refueling up above the MTOW of the airframe, or are they just trading payload and runway performance for fuel on board, knowing there's a tanker waiting?

[Edited 2013-07-29 14:12:40]
 
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kc135topboom
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RE: In Flight Refuelling Question

Mon Jul 29, 2013 9:16 pm

Almost all airplanes have a high max gross weight than their MTOW would indicate.

In the case of the B-52G/H, they had a MTOW of 488,000 lbs., but could refuel up to a max weight of about 520,000 lbs. inflight. However refueling beyond 488K did reduce the B-52's maneuverability to about 1.7g. It then had to burn down the extra fuel to 488K to get back to a 2.5g.

Other airplanes like the EC/RC/KC-135, KC-10, E-3, E-6, E-8, C-141, C-5, and C-130s would also refuel beyond MTOW if their mission requirements dictated that..
 
Max Q
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RE: In Flight Refuelling Question

Tue Jul 30, 2013 4:40 am

Quoting legs (Reply 4):

Are any of those cases actually refueling up above the MTOW of the airframe, or are they just trading payload and runway performance for fuel on board, knowing there's a tanker waiting?

That's the question I meant to ask !

Quoting KC135TopBoom (Reply 5):


In the case of the B-52G/H, they had a MTOW of 488,000 lbs., but could refuel up to a max weight of about 520,000 lbs. inflight. However refueling beyond 488K did reduce the B-52's maneuverability to about 1.7g. It then had to burn down the extra fuel to 488K to get back to a 2.5g.

Other airplanes like the EC/RC/KC-135, KC-10, E-3, E-6, E-8, C-141, C-5, and C-130s would also refuel beyond MTOW if their mission requirements dictated that..

Thanks KC, how much above MTOW could they go ?
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GST
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RE: In Flight Refuelling Question

Tue Jul 30, 2013 6:14 am

Quoting KC135TopBoom (Reply 5):

Other airplanes like the EC/RC/KC-135, KC-10, E-3, E-6, E-8, C-141, C-5, and C-130s would also refuel beyond MTOW if their mission requirements dictated that..

Does anyone know if any of those aircraft are unable to dump fuel? It would be an odd situation for MLW to exceed MTOW, and some emergencies won't let you loiter to burn fuel.
 
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kc135topboom
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RE: In Flight Refuelling Question

Tue Jul 30, 2013 1:41 pm

Quoting Max Q (Reply 6):
Thanks KC, how much above MTOW could they go ?

It depended on the airplane type, but generally between about 5% and 8%.

Quoting GST (Reply 7):
Does anyone know if any of those aircraft are unable to dump fuel? It would be an odd situation for MLW to exceed MTOW, and some emergencies won't let you loiter to burn fuel.

Most of those airplanes I listed can dump fuel if need be. I know all of the Boeings, except the B-52 can dump fuel. I am not sure about any of the Lockheed types. The KC-10 can also dump fuel.
 
rfields5421
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RE: In Flight Refuelling Question

Tue Jul 30, 2013 2:14 pm

Back in 1972 when I was stationd at NAS Agana Guam, some guys renting the house next door to ours were B-52 crew members.

The aircraft for Linebacker and Linebacker II took off from Andersen at MTOW with the largest possible bomb load, and less fuel due to the weight of the ordnance load.

They tanked soon after takeoff for the maximum fuel possible as they had to make a 5,000 nm round trip. They also had to tank at least once more, possible twice - to complete the mission.

Should an aircraft tanked above MLW have to return to Andersen quickly, they would have dropped the bomb load over the ocean to get the aircraft weight lower.
 
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ptrjong
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RE: In Flight Refuelling Question

Tue Jul 30, 2013 2:21 pm

Quoting KC135TopBoom (Reply 8):
It depended on the airplane type, but generally between about 5% and 8%.

Because there's just no room for cago and fuel left, or because the aircraft can't safely do any manoeuvring any more? Are there maximum gross weights for aircraft in the air? And overload weights maybe for special missions (the Vulcan raids)?
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nomadd22
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RE: In Flight Refuelling Question

Tue Jul 30, 2013 7:22 pm

I've heard so many stories of the reason SR-71s always refueled after takeoff, I'm not sure which are true. Leaky tanks until the skin warmed up, wanting to takeoff and get up at lower weight, inefficient takeoff and climb, lower GTOW than gross operational or a combination of all of them. I think they usually took about 5,000 lbs right after takeoff.
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rc135x
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RE: In Flight Refuelling Question

Wed Jul 31, 2013 1:58 am

Quoting KC135TopBoom (Reply 5):
Other airplanes like the EC/RC/KC-135, KC-10, E-3, E-6, E-8, C-141, C-5, and C-130s would also refuel beyond MTOW if their mission requirements dictated that..

The prototype KC-135E 59-1514 and KC-135R 61-0293 were both equipped for receiver air refueling from prior configurations. This allowed them to refuel during flight testing to absolute max gross weight which was well in excess of max gross takeoff weight (MGTOW). Age and amnesia have affected my ability to recall the specific numbers.

MGTOW was a function of engine capability rather than airframe fuel capacity. IIRC, the KC-135A "steam jet" was around 297k but the KC-135R was up around 322.5k. TopBoom be sure to check my weight & balance sheet!

In the TF33-equipped RC-135S we would takeoff at 285,000 MGTOW but after air refueling would be at 310,000, which was still below the in-flight max. There was little need to go to in-flight max and the stress it placed on the airframe as TopBoom mentioned with the B-52.

Quoting rfields5421 (Reply 9):
Should an aircraft tanked above MLW have to return to Andersen quickly, they would have dropped the bomb load over the ocean to get the aircraft weight lower.

This was not always the case. My dad aborted a B-52D mission out of Guam and they burned fuel to reach max gross landing weight while retaining the weapons load. Just prior to landing my dad announced over the intercom "Don't worry if any bombs fall off during the landing---they will explode under the tail and we'll be just fine." Silence. After landing the gunner finally spoke: "Thanks, pilot."  
KC-135A, A(RT), D, E, E(RT), Q, R, EC-135A, C, G, L, RC-135S, U, V, W, X, TC-135S, W
 
solarflyer22
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RE: In Flight Refuelling Question

Wed Jul 31, 2013 3:02 am

Quoting studedave (Reply 3):
With the Intruder you could carry a lot of everything.
With the Hornet you carry fuel or the stuff that goes boom.
You don't get both. (and Hornets like fuel)

Yeah, I've heard similar from a friend when they retired the Tomcats which had great range by comparison.

Quoting ptrjong (Reply 10):
or because the aircraft can't safely do any manoeuvring any more?

Yes, its already down to 1.7 G which means you can barely turn. Plus it stresses the wings and frame. You could hit turbulence for example above MTOW and no one is looking to fall apart.

Quoting nomadd22 (Reply 11):

I've heard so many stories of the reason SR-71s always refueled after takeoff, I'm not sure which are true. Leaky tanks until the skin warmed up, wanting to takeoff and get up at lower weight, inefficient takeoff and climb, lower GTOW than gross operational or a combination of all of them

My SR71 tour guide said it was leakage from the tanks that required tanking but they also flew very long missions as well.
 
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kc135topboom
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RE: In Flight Refuelling Question

Wed Jul 31, 2013 2:52 pm

Quoting ptrjong (Reply 10):
Quoting ptrjong (Reply 10):
Quoting KC135TopBoom (Reply 8):It depended on the airplane type, but generally between about 5% and 8%.
Because there's just no room for cago and fuel left, or because the aircraft can't safely do any manoeuvring any more? Are there maximum gross weights for aircraft in the air? And overload weights maybe for special missions (the Vulcan raids)?

In the case of the B-52, it was because it was refueled to 'full tanks'. But flying it at just a 1.7g restriction really limited the ability to defend itself, to.

IIRC, the only times this was authorized for the B-52 was for test flights and for EWO/SIOP. The position on the attack route was critical for this weight. The bomber had to cross the HHCL (Higher Headquarters Control Line, or more commoningly know as the 'Fail Safe' point) at the max inflight weight. This gave them time to burn down to a more maneuverable weight before penetration.

In the case of the FB-111 on an EWO/SIOP mission, the long tanker would refuel them well past the HHCL. This put the tanker at great risk, but it extended the range of the FB-111 to have an adequate fuel reserve over the recovery base. The FB-111 would also burn then shed its external fuel drop tanks, then use its external weapons first (as did the B-52) to decrease drag, thus save additional fuel.

I cannot go into additional information about the SIOP missions.

The Avro Vulcan B2 version was also capable of refueling above the MTOW.
 
aklrno
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RE: In Flight Refuelling Question

Wed Jul 31, 2013 10:03 pm

Quoting solarflyer22 (Reply 13):
My SR71 tour guide said it was leakage from the tanks that required tanking but they also flew very long missions as well.

I was at the official retirement ceremony at Beale AFB some years back. They flew one ceremonial mission and then parked the plane by the grandstand set up for speeches. As the generals droned on the plane cooled, and started to leak. By the end of the speeches it was raining fuel at an astonishing rate. IIRC they used a special low volatility fuel to avoid fires at the beginning or end of a mission. I suspect that if Beale is ever abandoned by DoD the toxic chemical cleanup bill will be astronomical due to years of spilled fuel.
 
flyingturtle
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RE: In Flight Refuelling Question

Wed Jul 31, 2013 10:47 pm

OT:

When we are talking refuelling and the KC-135 - has the NTSB, the USAF or a Kyrgyz investigation board already issued an interim report about the KC-135 crash in Kyrgyztan??


David
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windy95
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RE: In Flight Refuelling Question

Thu Aug 01, 2013 2:41 pm

Quoting flyingturtle (Reply 16):
the USAF or a Kyrgyz investigation board already issued an interim report about the KC-135 crash in Kyrgyztan??

Yes they briefed the CINC about a month ago and have released it to the safety depts but have not released the full one to the public yet. I heard it focuses on the -3 flight control section saying to review before flight. I think they are pointing at pilot error with Rudder deflection.

Quoting ptrjong (Reply 10):
Because there's just no room for cago and fuel left,

Yes limited by actual fuel tank size.



There had been missions out of places like Guam when we would do MITO departures and as soon as we had been airborne we (the KC-135) would accelerate ahead of the Buff's. At which point the boom would go to work and we would give them fuel on climbout. We would dump around 125,000lbs of fuel and peel off and head back home and land. Mission time for us would be around an hour and we would go from 285K in weight down to avout 130 to 140K just like that.
 
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kc135topboom
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RE: In Flight Refuelling Question

Sat Aug 03, 2013 9:05 pm

Quoting windy95 (Reply 17):
There had been missions out of places like Guam when we would do MITO departures and as soon as we had been airborne we (the KC-135) would accelerate ahead of the Buff's. At which point the boom would go to work and we would give them fuel on climbout. We would dump around 125,000lbs of fuel and peel off and head back home and land. Mission time for us would be around an hour and we would go from 285K in weight down to avout 130 to 140K just like that.

I never got a chance to fly one of those missions.
 
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moo
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RE: In Flight Refuelling Question

Sun Aug 04, 2013 4:42 pm

Quoting nomadd22 (Reply 11):

Col Richard Graham, an Sr-71 pilot, explains it fairly well in his book - while it was indeed leaky as a sieve, it wasn't the reason for it tanking soon after take off.

Infact, it used to fly a lot of missions from Kadena with full tanks without tanking.

The reason it used to tank on a lot of missions was because the single engine performance was so poor it was deemed to be too dangerous for missions where a tanker could be used.
 
AWACSooner
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RE: In Flight Refuelling Question

Tue Aug 06, 2013 9:57 am

We do it all the time in the E-3...since we have those awesome JT3 (TF33) engines  
 
10boomer
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RE: In Flight Refuelling Question

Fri Aug 16, 2013 9:58 pm

Quoting KC135TopBoom (Reply 5):
Other airplanes like the EC/RC/KC-135, KC-10, E-3, E-6, E-8, C-141, C-5, and C-130s would also refuel beyond MTOW if their mission requirements dictated that..

Both the MTOW and In-Flight Gross Weight for the KC-10 is 590,000
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kc135topboom
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RE: In Flight Refuelling Question

Sat Aug 17, 2013 6:20 pm

Quoting 10boomer (Reply 21):
Quoting KC135TopBoom (Reply 5):Other airplanes like the EC/RC/KC-135, KC-10, E-3, E-6, E-8, C-141, C-5, and C-130s would also refuel beyond MTOW if their mission requirements dictated that..
Both the MTOW and In-Flight Gross Weight for the KC-10 is 590,000

Is that a change? Back in the 1980s, IIRC, we would refuel the Gucci Bird to 615K or 625K, I cannot remember which one. When they were loaded with cargo, we would fill them to full tanks.
 
connies4ever
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RE: In Flight Refuelling Question

Sat Aug 17, 2013 7:10 pm

Quoting aklrno (Reply 15):
I was at the official retirement ceremony at Beale AFB some years back. They flew one ceremonial mission and then parked the plane by the grandstand set up for speeches. As the generals droned on the plane cooled, and started to leak. By the end of the speeches it was raining fuel at an astonishing rate. IIRC they used a special low volatility fuel to avoid fires at the beginning or end of a mission. I suspect that if Beale is ever abandoned by DoD the toxic chemical cleanup bill will be astronomical due to years of spilled fuel.


The low volatility fuel was designated JP-7 and required a chemical additive (I think triethylborane but I might be wrong) to get it to ignite. Apparently you could toss a lit cigarette into the JP-7 with impunity. I believe a dedicated subfleet of tanker, KC-135Qs, were tasked with supporting the A-12/SR-71 fleet.
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windy95
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RE: In Flight Refuelling Question

Sun Aug 18, 2013 1:36 pm

Quoting connies4ever (Reply 23):
I believe a dedicated subfleet of tanker, KC-135Qs, were tasked with supporting the A-12/SR-71 fleet.

Correct. The Q had two refueling manifolds. One for the JP-7 for the body tanks and one for the JP-4 and the wing tanks. They had been based at Beale and then overseas at Okinawa and Mildenhall.
 
10boomer
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RE: In Flight Refuelling Question

Sun Aug 18, 2013 4:48 pm

Quoting connies4ever (Reply 23):
Is that a change? Back in the 1980s, IIRC, we would refuel the Gucci Bird to 615K or 625K, I cannot remember which one. When they were loaded with cargo, we would fill them to full tanks.

As long as I've been with the 10 (1992-) that's been the limitation. The max in-flight weight is actually a Warning.
Fly Gucci
 
connies4ever
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RE: In Flight Refuelling Question

Sun Aug 18, 2013 6:57 pm

Quoting 10boomer (Reply 25):
Quoting connies4ever (Reply 23):
Is that a change? Back in the 1980s, IIRC, we would refuel the Gucci Bird to 615K or 625K, I cannot remember which one. When they were loaded with cargo, we would fill them to full tanks.

Not my post, was TopBoom's.
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