Royal Australian Air Force [RAAF] News, Discussions and Updates

[t68]

By all account it appears that KC30A is proving its worth in the ME, with a Flightglobal article it appears the troubled boom may have overcome its hurdles and KC30A should have FOC sometime this year.

An interesting fact that had not really caught my attention is that by (hopefully) by 2023 the only aircraft in service using the hose and drogue will be 24x F/A18F & EA18G all other will be by via the boom which includes the F35A.

I know the USAF has been using the boom method for a number of years on their frontline fighters such as the F16 & F15 and they have large numbers of aircraft available to support their missions, in an RAAF context I am just wondering about operational efficiency between both systems.

Whilst the KC30A in its present state is only available to refuel operationally via the hose it is able to refuel two aircraft at a time. I know fuel discharge rates vary between both systems but from an operational view point for an aircraft to refuel a flight of four time wise is it more efficient using the boom over the hose in time overall to refuel the flight?

 

[John Fedup]

By all account it appears that KC30A is proving its worth in the ME, with a Flightglobal article it appears the troubled boom may have overcome its hurdles and KC30A should have FOC sometime this year.

An interesting fact that had not really caught my attention is that by (hopefully) by 2023 the only aircraft in service using the hose and drogue will be 24x F/A18F & EA18G all other will be by via the boom which includes the F35A.

I know the USAF has been using the boom method for a number of years on their frontline fighters such as the F16 & F15 and they have large numbers of aircraft available to support their missions, in an RAAF context I am just wondering about operational effiancy between both systems.

Whilst the KC30A in its present state is only available to refuel operationally via the hose it is able to refuel two aircraft at a time. I know fuel discharge rates vary between both systems but from an operational view point for an aircraft to refuel a flight of four time wise is it more efficient using the boom over the hose in time overall to refuel the flight?

There was a picture of the A400M refuelling two F-18s. This would be have to be a hose and drogue system. I believe the F-35C will retain the drogue refuelling technique. This is also used with C130 tankers. Perhaps others can correct me if I am in error.

 

[t68]

There was a picture of the A400M refuelling two F-18s. This would be have to be a hose and drogue system. I believe the F-35C will retain the drogue refuelling technique. This is also used with C130 tankers. Perhaps others can correct me if I am in error.

Correct A400M&C130 use the hose and drouge method of inflight refueling as the designed with a ramp which prohibits the use of a boom, F35A from past reports can be either specified with either a probe or receptacle for inflight refueling but it is at the cost of it internal gun.

What I am trying to gather if by using the boom with its higher flow rates is it any quicker to refuel a flight say of four fighter aircraft compared to using the hose which can refuel two aircraft compared to the booms one. The boom system has benefits for aircraft that take on large amounts of fuel at a time in the US case B52 etc but in the RAAF case it's the E7A and also other KC30A aircraft

 

[John Newman]

What I am trying to gather if by using the boom with its higher flow rates is it any quicker to refuel a flight say of four fighter aircraft compared to using the hose which can refuel two aircraft compared to the booms one. The boom system has benefits for aircraft that take on large amounts of fuel at a time in the US case B52 etc but in the RAAF case it's the E7A and also other KC30A aircraft

I remember asking a similar question here on DT many years ago and the answer I received from one of the Def Pros at the time was that whilst the boom has the ability to deliver fuel at a much faster flow rate than the hose method, it is more to do with the ability of the receiving aircraft to accept that higher flow rate.

For example a B-52 has the ability to take advantage of that much higher flow rate, but a fighter for example can't, so the limitation is the receiver aircraft's ability.

It would be interesting to know, for example, how long it would take to fill up an F-35A via the boom on a KC-30A and compare that to how long it would take an F-35B or C via the hose and drogue method.

 

[t68]

I remember asking a similar question here on DT many years ago and the answer I received from one of the Def Pros at the time was that whilst the boom has the ability to deliver fuel at a much faster flow rate than the hose method, it is more to do with the ability of the receiving aircraft to accept that higher flow rate.

For example a B-52 has the ability to take advantage of that much higher flow rate, but a fighter for example can't, so the limitation is the receiver aircraft's ability.

It would be interesting to know, for example, how long it would take to fill up an F-35A via the boom on a KC-30A and compare that to how long it would take an F-35B or C via the hose and drogue method.

That's some usefull info there thank you.

I think the most obvious result there is the flow rate of the boom can exceed the flow rate of the hose, but the question remains is the flow rate of the hose equal to what the maximum rate receiving aircraft can handle. If not then in theory the boom should fill the aircraft faster, but does that translate to greater efficiency when each aircraft has to complete the hook up individually by the time the fourth aircraft is ready to receive fuel.

Also is their any advantage between using the internal gun or as the other variants will use a pod, as the F35A can use either probe or receptacle

 

[John Newman]

That's some usefull info there thank you.

I think the most obvious result there is the flow rate of the boom can exceed the flow rate of the hose, but the question remains is the flow rate of the hose equal to what the maximum rate receiving aircraft can handle. If not then in theory the boom should fill the aircraft faster, but does that translate to greater efficiency when each aircraft has to complete the hook up individually by the time the fourth aircraft is ready to receive fuel.

Also is their any advantage between using the internal gun or as the other variants will use a pod, as the F35A can use either probe or receptacle

Here is an interesting Wiki article on aerial refuelling:


[ame="http://en.wikipedia.org/wiki/Aerial_refueling"]Aerial refueling - Wikipedia, the free encyclopedia[/ame]


I read it years ago (haven't read it lately), but as I understand it the big driving force behind the boom method used by the USAF was Curtis LeMay, the commander of SAC, in that he wanted a refuelling method that would allow all of SAC's heavy metal to be refuelled at a much faster rate, anyway have a read of it when you get a chance.

As to you point about flow rates with fighter aircraft, I suppose it all comes down to the receiving rate that the fighter can accept, again I'd be interested to know if the max receiving rate of an F-35A (equipped for boom refuelling) is more or exactly the same as the receiving rate of either the probe equipped F-35B or C.

If, for example, it's the same receiving rate across all three variants then I'd think that it is pretty clear that a KC-30A would be able to refuel 4 B/C's quicker than 4 A's.

So if that is the case, that is probably a negative for the RAAF when the majority of the fighter aircraft in it's inventory are F-35A's when they are being topped up by the KC-30A.

On the other side of the coin, if the RAAF is involved in some future coalition operation that the USAF is involved in, then it will be a positive going to the F-35A as our aircraft will also be able to refuel from the various USAF KC boom equipped tankers on station too.

As to should there be more KC-30A's in RAAF service, well in my opinion that's a yes! Originally when the 5 aircraft were ordered there was an option for another 3, but as we all know that option wasn't exercised. And today of course it all comes down to funding being made available.

I remember a while ago when the ex Def Min was talking about the increase in the C-17A fleet from 6 to 8 and the possibility of another 2 to take the fleet to 10 airframes, he also mentioned the possibility of another KC-30A being acquired (possibly with a VIP fitout), if that is the case it will take the KC-30A fleet to 6, maybe eventually some other money can be found to take the tanker fleet to 8 airframes.

Just have to wait and see what's in the new DWP!

 

[ADMk2]

Correct A400M&C130 use the hose and drouge method of inflight refueling as the designed with a ramp which prohibits the use of a boom, F35A from past reports can be either specified with either a probe or receptacle for inflight refueling but it is at the cost of it internal gun.

What I am trying to gather if by using the boom with its higher flow rates is it any quicker to refuel a flight say of four fighter aircraft compared to using the hose which can refuel two aircraft compared to the booms one. The boom system has benefits for aircraft that take on large amounts of fuel at a time in the US case B52 etc but in the RAAF case it's the E7A and also other KC30A aircraft

The F-35A has the space availble to accept a refuelling probe on the starboard side of the aircraft, where such is fitted to B/C models. The gun is on the port side and doesn't affect the fitting of a probe.

However, no-one has paid to integrate a refuelling probe on the F-35A and that is the sticking point...

 

[John Newman]

The F-35A has the space availble to accept a refuelling probe on the starboard side of the aircraft, where such is fitted to B/C models. The gun is on the port side and doesn't affect the fitting of a probe.

However, no-one has paid to integrate a refuelling probe on the F-35A and that is the sticking point...

You beat me to it, I was just about to say much the same thing!

As to a probe being fitted to an F-35A, I do remember a while back reading an article about Canada's possible F-35A purchase (and I say possible because who knows when they will eventually make a decision!), but anyway, the point was that because the Canadian Polaris tankers (converted A310's) are only equipped for probe and not with a boom and I think (from memory?) that an LM representative said that a probe could indeed be fitted if required, what extra cost or not, I have no idea.

It would be interesting to know that if a probe was fitted to an F-35A, would the boom receptacle be also fitted or removed? Is it possible for an F-35A to have both installed at the same time?

 

[t68]

Well I finally Found some concrete infomation on refueling rates and capabilty, now it appears that the RAAF has learned the US lesson on mixed fleet and cooperation between service but is still a little baffling on why the A model still use the boom.

I guess it comes down to the fact that the USAF still have a lot of boom equipped aircraft and the time it would take to move over to something like MRTT. If Aussie Digger is right and the F35A can have both the gun and the probe whilst still leaving the boom receptacle would be the best of both worlds. How that affects the handling of the aircraft I have no idea, I also had heard of the Canadians preference for the probe but cannot find any reference about if the gun needed to be deleted


"A single flying boom can transfer fuel at approximately 6,000 lbs per minute. A single hose-and-drogue can transfer between 1,500 and 2,000 lbs of fuel per minute. Unlike bombers and other large aircraft, however, fighter aircraft cannot accept fuel at the boom’s maximum rate. (Today’s fighter aircraft can accept fuel at 1,000 to 3,000 lbs per minute whether from the boom or from the hose-and-drogue.)2 Thus, the flying boom’s primary advantage over the hose-and-drogue system is lost when refueling fighter aircraft."

"by refueling two fighters simultaneously, the time that the fighters spend refueling can be reduced by approximately 75 percent. This reduced refueling time, in turn, would enable the tanker to have considerably more fuel available to off-load to other receivers....The less fuel burned by either the tanker or the receivers during aerial contact, the more that is available to conduct the fighter mission. At fighter refueling speeds, a KC-135A burns something in excess of 200 pounds per minute. Reducing the air refueling time from 40 minutes to 10 minutes (75 percent) makes approximately 6,000 pounds of additional fuel available....the fuel savings in a four- tanker formation could be enough to refuel an extra flight of four fighters or allow the same mission to be accomplished with one less tanker."


"The perceived shortcomings of using a single boom to refuel fighter aircraft is reflected in a 1990 Air Force initiative to standardize DOD fighter aircraft refueling on the hose-and-drogue method. As initially conceived, the initiative consisted of three elements: (1) placing probes on all F-15 and F-16 fighters; (2) incorporating a probe in the design of the F-22A; and (3) adding two drogue pods to at least 150 KC-135s. To provide redundancy and flexibility, Air Force fighters would retain their boom receptacles.4 The 1991 war with Iraq (Operation Desert Storm) heightened DOD concerns over a lack of uniformity in aerial refueling methods. Navy leaders expressed frustration and dissatisfaction with the number of Air Force aerial refueling aircraft capable of employing the hose-and-drogue. Post-conflict analyses recommended that the Navy purchase its own fleet of land-based KC-10-sized tankers to increase the number of hose-and-drogue aircraft and reduce its reliance on Air Force aerial refueling."



http://fas.org/sgp/crs/weapons/RL32910.pdf

 

[John Fedup]

You beat me to it, I was just about to say much the same thing!

As to a probe being fitted to an F-35A, I do remember a while back reading an article about Canada's possible F-35A purchase (and I say possible because who knows when they will eventually make a decision!), but anyway, the point was that because the Canadian Polaris tankers (converted A310's) are only equipped for probe and not with a boom and I think (from memory?) that an LM representative said that a probe could indeed be fitted if required, what extra cost or not, I have no idea.

It would be interesting to know that if a probe was fitted to an F-35A, would the boom receptacle be also fitted or removed? Is it possible for an F-35A to have both installed at the same time?

The boom refuelling method was just another issue that Canadian F-35 critics love to rant on about. The advantage of the boom method, from a Canadian prospective, is it might result in new tankers for the RCAF. Of course, we need to order the F-35s first! If Harper loses the election in Oct., the F-35 purchase will be delayed for sure and outright rejection is also possible.

 

[John Newman]

The boom refuelling method was just another issue that Canadian F-35 critics love to rant on about. The advantage of the boom method, from a Canadian prospective, is it might result in new tankers for the RCAF. Of course, we need to order the F-35s first! If Harper loses the election in Oct., the F-35 purchase will be delayed for sure and outright rejection is also possible.

Hi John, I feel your pain, I really do!

I see your regular comments here and it must be so frustrating being a Canadian who is passionate about defence matters for their country and see such disappointing results.

Whilst here in Oz we may think that Government decisions and procurement process leaves a lot to be desired, but the Government decisions and procurement processes here almost appear 'perfect' in comparison to what appears to be happening in Canada.

I'm a regular reader of the Canadian 'Defence Watch' blog, and sometime contributor too, and I'm continually amazed at the extreme 'venom' against the F-35, it just amazes me, it really does!!

I suppose the biggest difference I see between here in Oz and Canada is that the issue of the F-35 procurement is basically a 'bi-partisan' approach from both major political parties, so there is no political points to be scored either way, but it certainly doesn't seem to be that way in Canada where the selection of the F-35 is such a political 'hot potato'!

 

[John Fedup]

Hi John, I feel your pain, I really do!

I see your regular comments here and it must be so frustrating being a Canadian who is passionate about defence matters for their country and see such disappointing results.

Whilst here in Oz we may think that Government decisions and procurement process leaves a lot to be desired, but the Government decisions and procurement processes here almost appear 'perfect' in comparison to what appears to be happening in Canada.

I'm a regular reader of the Canadian 'Defence Watch' blog, and sometime contributor too, and I'm continually amazed at the extreme 'venom' against the F-35, it just amazes me, it really does!!

I suppose the biggest difference I see between here in Oz and Canada is that the issue of the F-35 procurement is basically a 'bi-partisan' approach from both major political parties, so there is no political points to be scored either way, but it certainly doesn't seem to be that way in Canada where the selection of the F-35 is such a political 'hot potato'!

All your points above are right on the money. BTW, your comment on Defence Watch regarding the lease of a German Berlin class ship is a great idea...thus it is unlikely to happen!

 

[swerve]

Note that the refuelling rates quoted in that document are not entirely accurate. They understate the maximum refuelling rates of hose & probe systems, perhaps because it's a 10 year old US document, which didn't take full account of overseas developments.

Current hose & drogue systems can deliver fuel not at 1500-2000 lb per minute, but at up to 1300 kg (2865 lb) per minute for underwing pods (i.e. about as fast as any fighter can accept, & faster than many), & 1800 kg/3970 lb per minute for centre line mounted hoses, i.e. about twice as fast as that document states. These hose systems are fully operational, in active service, e.g. with the RAF.

IIRC hoses now deliver fuel faster than booms did when booms were adopted because they were faster than hoses.

The question of delivery rate is only significant for large aircraft, configured to accept fuel at very high rates, & for most air forces, these aircraft are few in number.

 

[t68]

Note that the refuelling rates quoted in that document are not entirely accurate. They understate the maximum refuelling rates of hose & probe systems, perhaps because it's a 10 year old US document, which didn't take full account of overseas developments.

Current hose & drogue systems can deliver fuel not at 1500-2000 lb per minute, but at up to 1300 kg (2865 lb) per minute for underwing pods (i.e. about as fast as any fighter can accept, & faster than many), & 1800 kg/3970 lb per minute for centre line mounted hoses, i.e. about twice as fast as that document states. These hose systems are fully operational, in active service, e.g. with the RAF.

IIRC hoses now deliver fuel faster than booms did when booms were adopted because they were faster than hoses.

The question of delivery rate is only significant for large aircraft, configured to accept fuel at very high rates, & for most air forces, these aircraft are few in number.

Cheers thanks for that info, puts it in a bit more perspective.

Also can the RAF Voyager KC3 refuel three aircraft at once or two on the underwing and one at a time on the centreline pod?

Do you think that RAF voyager aircraft will ever get a boom to refuel the P8 Poseidon /RC-135 Airseeker & C17 aircraft?

 

[swerve]

I'm afraid I can't answer your questions.

I can confirm that the RAAF tankers have the same 1300 kg/min wing units as the RAF Voyagers, as well as a 3600 kg/min boom. Note that the boom is 25% faster than the USAF booms referred to in the quoted US document (I think the new B767 based US tankers also have faster booms than in the document), as well as the hoses being almost 50% faster than the top of the hose range mentioned in it.


PS. With regard to the RCAF tankers, from what I've read (e.g. this US document) the usage rates of tankers are generally so much lower than the airliners from which they're derived that airframe fatigue is not an issue, & tankers such as the A310 can be expected to last many years. An A310 is used as a boom testbed by Airbus, so there shouldn't be any technical reason why RCAF tankers can't be fitted with booms. Whether it's better to fit RCAF F-35As with probes, as well as or in place of receptacles, needs more analysis than I can do.

 

[John Fedup]

I'm afraid I can't answer your questions.

I can confirm that the RAAF tankers have the same 1300 kg/min wing units as the RAF Voyagers, as well as a 3600 kg/min boom. Note that the boom is 25% faster than the USAF booms referred to in the quoted US document (I think the new B767 based US tankers also have faster booms than in the document), as well as the hoses being almost 50% faster than the top of the hose range mentioned in it.


PS. With regard to the RCAF tankers, from what I've read (e.g. this US document) the usage rates of tankers are generally so much lower than the airliners from which they're derived that airframe fatigue is not an issue, & tankers such as the A310 can be expected to last many years. An A310 is used as a boom testbed by Airbus, so there shouldn't be any technical reason why RCAF tankers can't be fitted with booms. Whether it's better to fit RCAF F-35As with probes, as well as or in place of receptacles, needs more analysis than I can do.

Of the 5 A310s in use with the RCAF, only two were converted for tanker operations so I guess a boom refit could be done on one of the other 3 as we transition to F-35As (assuming we actually buy them). I am guessing these former Wardair jets are about 25 years old so they do have some considerable service life remaining.

 

[gf0012-aust]

I am guessing these former Wardair jets are about 25 years old so they do have some considerable service life remaining.

its not calendar years that count though, its flight = frame stress hours

 

[John Fedup]

its not calendar years that count though, its flight = frame stress hours

True, however I believe these jets didn't get much use with Wardair as they went bankrupt shortly after delivery. Not sure if Canadian Airlines ever used them before they were aquired by Air Canada. I think the government took possession of them in the early '90s and their duty cycles would certainly be less than US and most allied tankers.

 

[hairyman]

We have five tankers at the moment, and it appears the PM wants one for his own use. How many would be an appropriate number for the RAAF? I have read where five is considered a good training number but thats it.

 

[John Fedup]

We have five tankers at the moment, and it appears the PM wants one for his own use. How many would be an appropriate number for the RAAF? I have read where five is considered a good training number but thats it.

Only two of our A310s are tankers. The other three are general purpose cargo/passenger jets and of these, one is is used for our PM. I would think some of our C-130Js can be configured as tankers.