More KC-46A woes....
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Apart from the few USAF tankers fitted with wing pods, all the other options you describe facilitate on single receiver AAR. Refuelling a 4-ship with such a limited system, particular the nightmarish BDA, takes way too long - blindingly obvious to me. Ever tried prodding the BDA? I did so once using a Q-fit (8 missiles and 3 tanks) F-4 against a KC-135 without the benefit of any previous dual training and it was very difficult - as the Italian Air Force Tornado force discovered on Night One of GW1. During which the USN far preferred prodding against the VC-10K with multiple hoses than queuing up behind a USAF tanker - no doubt the letters of thanks are still with the squadron.
Much easier to let fuel flown downhill in an anhedral wing than it would be to pump it up the pronounced dihedral of an A340, given the pressure drop at such a distance from the centre tank - which would probably dictate a need for larger pumps and wider-bore pipes that are required for the A330MRTT . Following the demise of the Valiant, the multi-hose Victor had quite a long gestation period before it was a total a success - and that was with the urgent service need plus the design work of a major aerospace manufacturer rather than some independent contractor touting for profit
The TriStar pod programme foundered on cost and complexity- and in the end was deemed unnecessary due to the preference for modification of the VC10 C Mk 1. Because 'hoses in the sky' are perceived to be of greater importance than the total fuel volume available.
Have you actually studied the wing planform of an A340-233/300 outboard of the outer engines? Quite a narrow chord and winglet, with little structure available upon which to hang a pod pylon between the slats and ailerons or to provide sufficient pod clearance from the slats and ailerons.
Much easier to let fuel flown downhill in an anhedral wing than it would be to pump it up the pronounced dihedral of an A340, given the pressure drop at such a distance from the centre tank - which would probably dictate a need for larger pumps and wider-bore pipes that are required for the A330MRTT . Following the demise of the Valiant, the multi-hose Victor had quite a long gestation period before it was a total a success - and that was with the urgent service need plus the design work of a major aerospace manufacturer rather than some independent contractor touting for profit
The TriStar pod programme foundered on cost and complexity- and in the end was deemed unnecessary due to the preference for modification of the VC10 C Mk 1. Because 'hoses in the sky' are perceived to be of greater importance than the total fuel volume available.
Have you actually studied the wing planform of an A340-233/300 outboard of the outer engines? Quite a narrow chord and winglet, with little structure available upon which to hang a pod pylon between the slats and ailerons or to provide sufficient pod clearance from the slats and ailerons.
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Indeed. Who was the first to point out on the F-35 mega thread that the F-35 was not designed as an air superiority fighter, but as a tactical bomber with fighter-like agility? And got creamed by dozens of folks for saying so. Is there anyone today who doubts that the primary mission of the F-35 is tactical bombing? And who was it who dared contradict Beagle who claimed that with full fuel, the A330MRTT can carry no cargo? I got creamed by the armchair pundits for that one also. But Just this Once recently posted "source data" supporting my position. So yes, I have "history" of going against the flow in a cause celebre where a bunch of armchair pundits are on a roll, like the F-35 and the KC-46. And that just cannot stand. Hence the very personal attacks. For which, despite your best efforts to justify, there is no justification. And that best effort? Weak. Downright feeble. "I have a history." I'm just a "floor sweeper" and not an engineer. Really? That's even weaker than the feeble attempts made on this forum to discredit my service as a USN pilot. Which were proven utterly false.
Oh please. That helmet mounted display subthread/derailment was going strong before I even waded into the fray and it died not long after I entered it because the whole helmet mounted display rubbish was just that. Rubbish and a total distraction. And BTW, if you'd read what I actually wrote you'd know how I knew about the F-35's helmet mounted display system. So you wouldn't have to ask now "how come I knew..."
Let's face it guys, your problem is not with the substance. You're problem is with who is delivering it. And that's just pathetic.
Let's face it guys, your problem is not with the substance. You're problem is with who is delivering it. And that's just pathetic.
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Returning to the scheduled broadcast, the cost of fitting booms, operator stations and remote vision systems to airline-type aircraft (except for those which already have a modification available, such as the A330 and KC-767 / KC-46) is very considerable. People have occasionally asked Omega whether they looked at it, but the €millions needed was the reason why not! Had they deemed the cost/benefit positive, they would probably have invested. But they're run by a very shrewd CEO and he would have needed to see a very sound business plan before doing so.
KenV, I can't recall what you flew in the USN - or when? But if it meant you did some KC-135 BDA jousting, I'm sure you'll know what a PITA that was. As I mentioned earlier, the Italian Tornado force launched 8 jets on Night One; one turned back quite early as it had a problem, of the remaining 7 only 1 was able to prod the KC-135 in the dark turbulent conditions. That brave crew pressed on as a single ship, but were subsequently shot down and taken captive.
On the topic of MRTTs, if a true multi-role tanker still has an availability to carry any cargo with full tanks, the obvious question would be why didn't the designer fit bigger tanks? So that with normal crewing and no cargo, the ZFW would be such that full tanks would take it to MTOW. The trade-off between cargo mass offered and fuel required for the AAR mission has always been an interesting exercise, particularly on trails when the AT planners and AAR planners might not always have seen eye-to-eye...
KenV, I can't recall what you flew in the USN - or when? But if it meant you did some KC-135 BDA jousting, I'm sure you'll know what a PITA that was. As I mentioned earlier, the Italian Tornado force launched 8 jets on Night One; one turned back quite early as it had a problem, of the remaining 7 only 1 was able to prod the KC-135 in the dark turbulent conditions. That brave crew pressed on as a single ship, but were subsequently shot down and taken captive.
On the topic of MRTTs, if a true multi-role tanker still has an availability to carry any cargo with full tanks, the obvious question would be why didn't the designer fit bigger tanks? So that with normal crewing and no cargo, the ZFW would be such that full tanks would take it to MTOW. The trade-off between cargo mass offered and fuel required for the AAR mission has always been an interesting exercise, particularly on trails when the AT planners and AAR planners might not always have seen eye-to-eye...
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Apart from the few USAF tankers fitted with wing pods, all the other options you describe facilitate on single receiver AAR. Refuelling a 4-ship with such a limited system, particular the nightmarish BDA, takes way too long - blindingly obvious to me. Ever tried prodding the BDA? I did so once using a Q-fit (8 missiles and 3 tanks) F-4 against a KC-135 without the benefit of any previous dual training and it was very difficult - as the Italian Air Force Tornado force discovered on Night One of GW1. During which the USN far preferred prodding against the VC-10K with multiple hoses than queuing up behind a USAF tanker - no doubt the letters of thanks are still with the squadron..
Much easier to let fuel flown downhill in an anhedral wing than it would be to pump it up the pronounced dihedral of an A340, given the pressure drop at such a distance from the centre tank - which would probably dictate a need for larger pumps and wider-bore pipes that are required for the A330MRTT . Following the demise of the Valiant, the multi-hose Victor had quite a long gestation period before it was a total a success - and that was with the urgent service need plus the design work of a major aerospace manufacturer rather than some independent contractor touting for profit.
The TriStar pod programme foundered on cost and complexity- and in the end was deemed unnecessary due to the preference for modification of the VC10 C Mk 1. Because 'hoses in the sky' are perceived to be of greater importance than the total fuel volume available.
Have you actually studied the wing planform of an A340-233/300 outboard of the outer engines? Quite a narrow chord and winglet, with little structure available upon which to hang a pod pylon between the slats and ailerons or to provide sufficient pod clearance from the slats and ailerons.
And besides, the point is moot. There's nothing in the fee for services contract that requires WARP in the first place.
http://s0.geograph.org.uk/geophotos/...3_992013ad.jpg
Thread Starter
Nice photo! But I was thinking more about a generic aircraft design than the specific requirements of the services contract. Whoever bids for the contract will presumably have future options in mind?
Pressure drop and the need for higher volumetric flow rates to provide the required pod pressure for the TriStar pod programme led to the need for larger pipe bores than initially specified - getting the fuel all that way to the pod pylon wasn't very easy. Whereas the A330MRTT has the huge benefit of taking advantage of the redundant outboard engine locations of the A340 and the existing fuel feed pipework.
The Victor K2 pods were low to the ground and the wing area where they were located was fairly generous - they weren't mounted at the wing tips either. So low were they that a plan to base the Victor at Scampton was ruled out due to the undulating nature of Scampton's taxiways and the need for much more cleared space adjacent to the taxiways than was required by the Vulcan.
Pressure drop and the need for higher volumetric flow rates to provide the required pod pressure for the TriStar pod programme led to the need for larger pipe bores than initially specified - getting the fuel all that way to the pod pylon wasn't very easy. Whereas the A330MRTT has the huge benefit of taking advantage of the redundant outboard engine locations of the A340 and the existing fuel feed pipework.
The Victor K2 pods were low to the ground and the wing area where they were located was fairly generous - they weren't mounted at the wing tips either. So low were they that a plan to base the Victor at Scampton was ruled out due to the undulating nature of Scampton's taxiways and the need for much more cleared space adjacent to the taxiways than was required by the Vulcan.
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I'm guessing that perhaps the Italian Tornado pilots you mentioned having all that trouble tanking from a BDA equipped KC-135, this was their first experience with the Iron Maiden? That has to be a heart stopper doing that the first time on an actual combat mission with live ordnance.
And about the airplane I flew? You mockingly called it a "mini-jet" or some such. A-4 Skyhawk and finally F/A-18.
On the topic of MRTTs, if a true multi-role tanker still has an availability to carry any cargo with full tanks, the obvious question would be why didn't the designer fit bigger tanks?
Beyond that, you'll have to ask Airbus and the operators of the A330MRTT. Or maybe ask Just This Once. He claims to have "source data" for A330MRTT and might have some "source data" that addresses the reasoning behind this design.
Last edited by KenV; 4th Feb 2019 at 16:42.
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Further, the KC-707 Omega uses has a centerline (i.e. internally fuselage mounted) hose and drogue system. That is a rather unique development not used by any military aircraft I'm aware of. They managed to afford that just fine. How difficult/expensive would it be to adapt that system to the A340? Or for that matter to adapt the existing centerline hose and drogue system on the A330 to the A340? The aft fuselage structure of the A330 and A340 are very similar, if not essentially identical. Depending on the nature of the services to be provided, an A340-500 (the one with the higher TOGW and the higher fuel capacity.) with a boom and centerline hose and drogue system and no WARP would be easy and cheap to develop and provide some eye-watering fuel offload numbers.
Last edited by KenV; 4th Feb 2019 at 16:31.
Thread Starter
Well, the A310MRTT could have had 5 x ACT, but when the numbers were crunched it was realised that an increase in allowable MTOW would have been needed if max fuel was carried - and the Net Flight Path limits at the tanker's MOB were significant even though the RW length was not. So 4 x ACT was the final choice. In the case of the A330 though, it already had a 111 tonne max fuel capability, so it was retained for the MRTT, although with the added structural mass it is rare that 111 tonne can actually be carried, I gather it's normally around 109.
KC-46 needed some centre tank extensions over the base -200ER, but the number crunchers came up with a compromise which met the spec. and still allowed some cargo capacity with full tanks - as was the case with the VC10C1K. Fair enough, but it could have carried more fuel had that been necessary.
With you on the Iron Maiden! Wretchedly horrible device - and if you missed the boomer would then move the thing, losing you the previous visual reference. After my first couple of jousts, I had to ask the young lady driving the boom to keep the darned thing still. Fortunately when in contact the onload rate was vastly superior to that from a Victor. Having completed my Teach Yourself BDA Prodding lesson, the Russians we were after decided to turn for home before we got much further North.
KC-46 needed some centre tank extensions over the base -200ER, but the number crunchers came up with a compromise which met the spec. and still allowed some cargo capacity with full tanks - as was the case with the VC10C1K. Fair enough, but it could have carried more fuel had that been necessary.
With you on the Iron Maiden! Wretchedly horrible device - and if you missed the boomer would then move the thing, losing you the previous visual reference. After my first couple of jousts, I had to ask the young lady driving the boom to keep the darned thing still. Fortunately when in contact the onload rate was vastly superior to that from a Victor. Having completed my Teach Yourself BDA Prodding lesson, the Russians we were after decided to turn for home before we got much further North.
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With you on the Iron Maiden! Wretchedly horrible device - and if you missed the boomer would then move the thing, losing you the previous visual reference. After my first couple of jousts, I had to ask the young lady driving the boom to keep the darned thing still. Fortunately when in contact the onload rate was vastly superior to that from a Victor. Having completed my Teach Yourself BDA Prodding lesson, the Russians we were after decided to turn for home before we got much further North.
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Well, the A310MRTT could have had 5 x ACT, but when the numbers were crunched it was realised that an increase in allowable MTOW would have been needed if max fuel was carried - and the Net Flight Path limits at the tanker's MOB were significant even though the RW length was not. So 4 x ACT was the final choice. In the case of the A330 though, it already had a 111 tonne max fuel capability, so it was retained for the MRTT, although with the added structural mass it is rare that 111 tonne can actually be carried, I gather it's normally around 109.
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KenV , the 'wiki' figure you quote for Maximum Take-Off Weight does not agree with the Airbus brochure figure for the A330MRTT, which is 233T (514 000 lb).
The same figure is quoted by Wikipedia, which further states that the OEW is 125T. Thus 125+111 exceeds MTOW by 3T, so my estimate of a day-to-day maximum fuel figure of 109T was fairly close, assuming rounding errors. Which means that with max fuel it cannot carry any cargo.
I have no idea why the 'normal' 242T MTOW for an A330-200 wasn't used for the MRTT.
Yes, vascodegama the comparison I was making between the KC-135 BDA and the Victor was indeed with the Mk20 wing pods. By choice I would prefer to prod the centreline, but we usually worked in pairs so were stuck with the pods.
The same figure is quoted by Wikipedia, which further states that the OEW is 125T. Thus 125+111 exceeds MTOW by 3T, so my estimate of a day-to-day maximum fuel figure of 109T was fairly close, assuming rounding errors. Which means that with max fuel it cannot carry any cargo.
I have no idea why the 'normal' 242T MTOW for an A330-200 wasn't used for the MRTT.
Yes, vascodegama the comparison I was making between the KC-135 BDA and the Victor was indeed with the Mk20 wing pods. By choice I would prefer to prod the centreline, but we usually worked in pairs so were stuck with the pods.
Beags
The preference was to refuel one at a time on the HUD even allowing for swap over it was far quicker since the HDU had an off load rate 4 times that of the pod. The only time I remember using pods was on a trail when the AARC had planned for that option.
The preference was to refuel one at a time on the HUD even allowing for swap over it was far quicker since the HDU had an off load rate 4 times that of the pod. The only time I remember using pods was on a trail when the AARC had planned for that option.
BEagle
The problems at Scampton were not caused by the wing mounted AAR pods but by the ground clearance below the Underwing Fuel Tanks on the K2. The pods were head high, whereas the clearance below the tanks was only about 18 inches. So low that they were likely to hit any snow depth warning indicators next to taxiways. At Paine Field (Washinton State,USA) my Nav Rad and Crew Chief had to navigate us about 2 miles, on foot, over these as we taxied in to the parking area for an airshow. One other snag at Scampton was the "lumpy" nature of the runway construction which would have had severe consequences for the Victor fatigue life. This together with the need to remove concrete kerbs and refuelling pipes at all the dispersals was too expensive to rectify for the, then, proposed life of the Victor K2.
The choice of using the wing pods or centre line HDU was also a function of the flow rate of the various receiver types. The Mk 20 pod on the Victor, which had an integral 1000lbs fuel tank, had a flow rate of 1500lbs/min whereas the HDU was 4000lbs /min. With aircraft such as the Lightning and Jaguar, which took fuel at 1100 lbs/min, it was quicker to refuel a pair on the pods rather than sequentially on the HDU. The F4 took fuel at 4000lbs/min, so would empty the pod fuel tank fairly quickly, which would not pass any more fuel until it had filled to half fuel again. Hence it was quicker to refuel a pair of F4s one at a time, with continuous fuel flow, on the HDU.
The VC10 had the Mk 32 pod, which did not have an internal tank, and gave a fuel flow of 2800lbs/min, however the VC10 fuel system only allowed 2200lbs/min if both pods were in use together. The HDU was the same on both types. So, again it could be quicker to use the HDU for a pair of F4s than to use the wing pods.
All of the above figures are from memory of 30+ years ago, so anybody with the reference books can challenge me without me getting upset or descending to personal abuse.
The problems at Scampton were not caused by the wing mounted AAR pods but by the ground clearance below the Underwing Fuel Tanks on the K2. The pods were head high, whereas the clearance below the tanks was only about 18 inches. So low that they were likely to hit any snow depth warning indicators next to taxiways. At Paine Field (Washinton State,USA) my Nav Rad and Crew Chief had to navigate us about 2 miles, on foot, over these as we taxied in to the parking area for an airshow. One other snag at Scampton was the "lumpy" nature of the runway construction which would have had severe consequences for the Victor fatigue life. This together with the need to remove concrete kerbs and refuelling pipes at all the dispersals was too expensive to rectify for the, then, proposed life of the Victor K2.
The choice of using the wing pods or centre line HDU was also a function of the flow rate of the various receiver types. The Mk 20 pod on the Victor, which had an integral 1000lbs fuel tank, had a flow rate of 1500lbs/min whereas the HDU was 4000lbs /min. With aircraft such as the Lightning and Jaguar, which took fuel at 1100 lbs/min, it was quicker to refuel a pair on the pods rather than sequentially on the HDU. The F4 took fuel at 4000lbs/min, so would empty the pod fuel tank fairly quickly, which would not pass any more fuel until it had filled to half fuel again. Hence it was quicker to refuel a pair of F4s one at a time, with continuous fuel flow, on the HDU.
The VC10 had the Mk 32 pod, which did not have an internal tank, and gave a fuel flow of 2800lbs/min, however the VC10 fuel system only allowed 2200lbs/min if both pods were in use together. The HDU was the same on both types. So, again it could be quicker to use the HDU for a pair of F4s than to use the wing pods.
All of the above figures are from memory of 30+ years ago, so anybody with the reference books can challenge me without me getting upset or descending to personal abuse.
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KenV , the 'wiki' figure you quote for Maximum Take-Off Weight does not agree with the Airbus brochure figure for the A330MRTT, which is 233T (514 000 lb).
The same figure is quoted by Wikipedia, which further states that the OEW is 125T. Thus 125+111 exceeds MTOW by 3T, so my estimate of a day-to-day maximum fuel figure of 109T was fairly close, assuming rounding errors. Which means that with max fuel it cannot carry any cargo.
I have no idea why the 'normal' 242T MTOW for an A330-200 wasn't used for the MRTT.
The same figure is quoted by Wikipedia, which further states that the OEW is 125T. Thus 125+111 exceeds MTOW by 3T, so my estimate of a day-to-day maximum fuel figure of 109T was fairly close, assuming rounding errors. Which means that with max fuel it cannot carry any cargo.
I have no idea why the 'normal' 242T MTOW for an A330-200 wasn't used for the MRTT.
FWIW, I was hesitant to use the Airbus MRTT brochure because it seems to be a marketing tool, not a technical document. For example, this leading phrase in Airbus' brochure states: "The A330 MRTT can carry up to 111 tonnes of fuel; this is the highest capacity of all tanker aircraft, even those which have additional fuel tanks in the cargo deck." This is total nonsense. Both the KC-10 and KC-747 (granted only two of the latter were built) carry much more fuel (161 / 165 tonnes respectively). Dutch Air Force and Commercial KDC-10 also carry more fuel (159 tonnes). And depending on the source, Il-78 also carries more fuel (138 tonnes).
Last edited by KenV; 5th Feb 2019 at 12:16. Reason: Added IL-78 fuel capacity
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Just this Once... , how does increased OEW with the ARBS make any difference to MTOW? Surely it will simply reduce max fuel weight?
233T MTOW is straight out of 'Global Enabler', the glossy brochure handed out to attendees of the 2013 AMUG in Getafe - a critical audience if ever there was one.
For many years, Airbus used a figure of 0.78 for the fuel SG in its brochures. My suspicion was that this meant that sales brochures could state higher ZFW with max fuel, promising higher payloads. Whereas most military operators assume an SG of 0.80.
The A330MRTT has a max fuel capacity of 139000 litre, so the civil brochure probably stated that max fuel is 139x.78=108.4T, whereas the MRTT brochure uses 139x.8=111.2T. Then it was discovered that with typical ZFW, with 111.2T the aircraft would exceed 233T MTOW - but this doesn't appear to have given the operators any problems.
I found similar issues with early quotes for the A310MRTT where 0.78 had been used and queried why, since 0.80 is the normally accepted value. Trying to turn volumetric figures into typical weight values proved quite a problem...unless accurate SG was taken into account!
233T MTOW is straight out of 'Global Enabler', the glossy brochure handed out to attendees of the 2013 AMUG in Getafe - a critical audience if ever there was one.
For many years, Airbus used a figure of 0.78 for the fuel SG in its brochures. My suspicion was that this meant that sales brochures could state higher ZFW with max fuel, promising higher payloads. Whereas most military operators assume an SG of 0.80.
The A330MRTT has a max fuel capacity of 139000 litre, so the civil brochure probably stated that max fuel is 139x.78=108.4T, whereas the MRTT brochure uses 139x.8=111.2T. Then it was discovered that with typical ZFW, with 111.2T the aircraft would exceed 233T MTOW - but this doesn't appear to have given the operators any problems.
I found similar issues with early quotes for the A310MRTT where 0.78 had been used and queried why, since 0.80 is the normally accepted value. Trying to turn volumetric figures into typical weight values proved quite a problem...unless accurate SG was taken into account!
Last edited by BEagle; 5th Feb 2019 at 11:29.
Beagle is correct SG is important - a change 0 0.05 in the SG figure makes a difference of 0.05 of a tonne