AWACS Refueling Question [Archive]

BenThere

23rd Jul 2006, 11:43

KC-135 and KC-10 tankers are both probe and drogue capable. The problem on the KC-135 is the drogue must be attached on the ground, making mixed boom and drogue refueling on one sortie impossible. There is a mod to attach drogue pods on the wings to allow both types of receivers. The KC-10 can use, I believe, drogue pods and the boom concurrently in flight.

Another key limitation is the rate of fuel offload to the receiver. The drogue on the KC-135 allows only one of four hydraulic pumps to operate, at a theoretical rate of 1600 lbs/minute and a practical rate of about 1,000 lbs/minute. The boom, with four pumps, offloads at 6400 lbs/minute.

In the case of the E3 AWACS, an operational offload of say, 80,000 lbs, would take about an hour with a drogue, while a boom would get the job done in 15 minutes.

BEagle

23rd Jul 2006, 12:12

The RAF E-3D has both probe and receptacle. As far as I'm aware, it is the only bisexual receiver in RAF service; every other reciver uses the 'male' probe-and-drogue technique rather than the 'female' boom-and-receptacle method.

The BDA is a truly dreadful device. I had to prod against it with a Q-fit Phantom (8 missiles, 3 tanks) once without ever having had any dual instruction.... You are supposed to make contact very slowly, then push until valves at both ends of the adaptor open; the hose ends up in a sort of S-bend shape and is highly likely to snap the probe off as allowable positional tolerance is much less than with a proper hose - and if you miss on the approach to contact the boom person is likely to move the damn thing. It doesn't have any hose response system and seems to rely purely on hose flex to compensate for receiver movement. It truly sucks!

I don't think that any large aircraft are cleared to use the BDA - and detcos in Incirlik certainly weren't happy to let some UK aircraft prod against it.

BenThere

23rd Jul 2006, 12:16

I remember doing refueling certification and training for the Tornadoes at RAF Cottesmore over a decade ago. My 135 came back with a Tornado's probe still attached. Not cheap.

brickhistory

23rd Jul 2006, 13:23

KC-135 and KC-10 tankers are both probe and drogue capable. The problem on the KC-135 is the drogue must be attached on the ground, making mixed boom and drogue refueling on one sortie impossible. There is a mod to attach drogue pods on the wings to allow both types of receivers. The KC-10 can use, I believe, drogue pods and the boom concurrently in flight.
Another key limitation is the rate of fuel offload to the receiver. The drogue on the KC-135 allows only one of four hydraulic pumps to operate, at a theoretical rate of 1600 lbs/minute and a practical rate of about 1,000 lbs/minute. The boom, with four pumps, offloads at 6400 lbs/minute.
In the case of the E3 AWACS, an operational offload of say, 80,000 lbs, would take about an hour with a drogue, while a boom would get the job done in 15 minutes.

I lost out on this one a while back; a lot of the -135s have been modded with drogue pods so they are no longer either/or.

Kidderminster Kid

23rd Jul 2006, 19:21

French E3s have seen the light, and have fitted blanks over their probes!

L J R

23rd Jul 2006, 19:45

Beenthere,

Some KC-135s have wing pod mounted baskets AS WELL as the centreline Boom. In this configuration, they can refuel any commer. I acknowledge that often the single CL Boom may have the BDA (What a laugh it is trying to get connected to that contraption for those who haven't tried!!!).

....just a point of order!

BenThere

23rd Jul 2006, 20:21

I defer to your more current knowledge and stand corrected. I've been out of the game a few years and only know my reserve tanker unit had only the center line drogue to attach to the boom last time I checked a few months ago.

The fact remains though, the boom is the only way to go for refueling heavy receivers.

ImageGear

23rd Jul 2006, 20:33

On a recent visit to RIAT, I had a close look at the FR Aviation, KC10 (or equivalent) with the Cobham pods but with what appeared to be a blanking plate bolted over where the boom assembly should be.

Looked a bit temporary but how would I know ?

Did anyone else have a good view?

Imagegear

BEagle

23rd Jul 2006, 20:59

Ben There, clearly the success of probe-and-drogue refuelling on OP BLACK BUCK in 1982 didn't actually penetrate the redneck media?

ImageGear, presumably you're referring to Global Airtanker Services' ancient DC10-40s with FR pods? Intended to be flown by ex-USAF mercenaries in support of the USN? I hear that some have 80000 hours on them - the a/c that is!

L J R

23rd Jul 2006, 21:04

Image,

The KC-10 that FR are converting is to complement a standing contract with a pair of Irish businessmen who (I believe) are buying 10-12 of the KC-10s, in addition to the KB707 they already utilise for the US DoD. I understand that the single KB707 has off loaded more fuel this year than the entire UK based RAF refuelling fleet. - heresay only, I dont have the verified facts....

brickhistory

23rd Jul 2006, 21:09

Ben There, clearly the success of probe-and-drogue refuelling on OP BLACK BUCK in 1982 didn't actually penetrate the redneck media?

Ah, BEagle, cheap drive-by on your part...Ben is over 18 so he can speak for himself, but nowhere in his posts did I find him referencing, discussing or denegrating probe-and-drogue. Wonderful that it works, good job on BLACK BUCK (no it didn't/doesn't get much publicity over here, but then how much did/does it really get in the UK or Europe?), but the fact remains that a boom can pump one helluva lot more per minute than trailing a drogue. Handy to have if one is in a B-52 or E-3 or the like.

sonicstomp

23rd Jul 2006, 21:30

As the E3F no longer has a probe capability, I believe the E3D is the only heavy jet, indeed only a/c (I think) capable of both P&D and Boom.

Sentry is cleared to refuel from VC-10, Tristar (Centre-line basket), US KC135, US KC-10, French KC135 and Dutch KDC-10.

Boom is preferred due to higher flow rate (as previously mentioned), however is more difficult for the receiver pilot (smaller envelope = tighter formation required)....However, to maintain compatibility with national tankers, the E3D retains its probe capability.

All CR Sentry skippers are now required to maintain currency on both disciplines, day and night..(it used to be boom only, basket where possible)..although this can be a bit of a challenge with the scarcity of the mighty VC-10 & Tristar for receiver upgrade trg and currency sorties.

BEagle

23rd Jul 2006, 21:32

"....the boom is the only way to go"

Would seem to imply that there is no other way. Which is nonsense.

Hardly surprising if indeed the American mercenaries in their old 707 have offloaded a lot of fuel compared to the UK-based RAF AAR fleet - as it spends so much time in either the Malvinas or various $hitholes in the sandpit, thanks to the simpering little poodle's love for Dubya and all his wars.

brickhistory

23rd Jul 2006, 21:39

Hardly surprising if indeed the American mercenaries in their old 707 have offloaded a lot of fuel compared to the UK-based RAF AAR fleet - as it spends so much time in either the Malvinas or various $hitholes in the sandpit, thanks to the simpering little poodle's love for Dubya and all his wars.

Bad day today?

That's two post with the "mercenaries" tag applied. Why? It is accurate I would agree, but how is it different from your own circumstances? They sell their experience and skills to a company willing to pay them. And that's different from you because.....?

BEagle

23rd Jul 2006, 21:57

You really can't see the difference?

Oh well.

PFI aircrew, 'sponsored reservists', call them what you will, but they are simply mercenary civilian aircrew flying military missions.

Maybe note quite in the same league as 'Air America' was - or whoever it is who flies those clandestine airliners of yours around bringing happy campers to your torture camps.

NutherA2

23rd Jul 2006, 22:02

[
The BDA is a truly dreadful device...... You are supposed to make contact very slowly, then push until valves at both ends of the adaptor open; the hose ends up in a sort of S-bend shape and is highly likely to snap the probe off as allowable positional tolerance is much less than with a proper hose - and if you miss on the approach to contact the boom person is likely to move the damn thing. It doesn't have any hose response system and seems to rely purely on hose flex to compensate for receiver movement. It truly sucks! ]

Thanks for the memory, Beags, I had the “pleasure” of refuelling an F4 from a KC135 with BDA just once in about 1972; as pantomimes go it was an unforgettable experience. The briefing amounted to being told which towline to go to and to see how the tanking worked out. The first few attempts to contact the drogue reduced my navigator to tears of laughter as they all resulted in random misses all around the clock. Eventually I noticed a crewman in the tanker’s big rear window. When I asked their driver what this fellow was doing he responded, “He’s the boom operator and is trying to get the drogue on to your probe”. After I asked that he be persuaded to stop doing this the operation went much better and we did leave with more fuel than we had on arrival. :ugh: :ugh: :ugh:

brickhistory

23rd Jul 2006, 23:49

.......to your torture camps.

Just another example of the "one people separated by a common language." What you call "torture camps" we call orthodontists. :E

D-IFF_ident

24th Jul 2006, 03:37

See Farnborough link here:

http://www.ainonline.com/Publications/farn/farn_06/omega_8_D3.htm

Maybe mercs would be better than nothing? And unless the PFI ever gets signed, nothing is what the "second best" air force in the world will end up with.

West Coast

24th Jul 2006, 04:53

As I've said before, yer just not a real man till you have tanked while flying a helo. Yes beag's, that includes you.

ORAC

24th Jul 2006, 05:21

The BDA doesn´t have a lot of flexibility, hence the restrictions on its use. Not suitable for those with spindly probes.

The Lightning used to practice quite a bit, and all I can say is thank god for frangible tips. There were times I thought the USAF must have more of them than the RAF. I can remember a period when the KC-135s seemed to only get through 2 or 3 receivers before someone left one in the basket and they had to go home to change it.

The F-4s, on the other hand, IIRC, seemed to prefer to take the basket home with them. But it was all a long time ago.....

BEagle

24th Jul 2006, 05:41

Yes, Westie, it certainly seems that the technique for prodding from a helicopter is similar to the technique porcupines use for making little porcupines....

....with great care! Or risk severe probe damage...:eek:

But the RAF doesn't yet even have a helicopter AAR capability of its own....:confused:

As for using mercenaries for core military requirements, sorry, but I don't agree. Organisations such as the ANG are one thing, 100% contractor-operated quite something else.

ImageGear

24th Jul 2006, 06:57

Thanks, LJR,

So it is a blanked off boom window then ?

I suppose it could easily be restored ?

Imagegear

beerdrinker

24th Jul 2006, 07:23

Sonicstomp.

Many thanks for that complete reply to my query. Much appreciated.

BD

D-IFF_ident

24th Jul 2006, 15:27

Omega have bought 20 DC10-40s from JAL, all with around 80 000 hours on the frames. They have recently received certification for the pods, but the boom is still in development. I believe that their plans are to fill the capability gaps that appear to be opening in both the US and UK forces. I agree that Mercs are not acceptable Beags, but I can understand Mr McEvaddy's idea to make money out of our leaderships' lack of foresight. Some of our own were toying with the idea of buying a 707 or two a few years ago, to sell fuel back to the RAF... If the PFI with Airtanker does get signed then we can take a good look at the contract to see if the definition of mercenary has been blurred to accommodate the shambles that the whole scheme appears to be.

Since AAR assets are regularly part of an overall package of airpower, they MUST be flown by combatant military personnel and recognised under the Geneva Convention. If the tanker is flown by hired civilians then we might as well let them fly the fighters and bombers too.

For the original question - I think the E-3D is the only receiver capable of taking fuel either way; the KC-10 always has a centreline hose available, and a high capacity, high flow rate boom available, wing pods are attached as required. Oh, and NKAWTG etc. ;)

brickhistory

24th Jul 2006, 16:06

I agree that combat missions, to include the AAR crews, should be performed by uniformed, however, what is inherently military about AAR? It's my, albeit limited, understanding that the USN contracted for civilian support during exercises. Is there a contract for the shooting end of the spectrum?

If not, how is civilians providing AAR any different than the companies that tow the DART for the fighters or the CRAF or contracted guys who move the troops into/out of country?

Not a wind up, genuinely looking for the difference.

Art Field

24th Jul 2006, 19:41

What is inherently military about AAR?. It depends how you present it. Sit up somewhere safe, flying orbits, thumb in proverbial then very little. Being tactically aware, flexible to receivers requirements, relaying radio calls, positioning to the advantage of the overall situation and a can do approach to the task means the day to day training sorties are just as military as the combat ones. Would one argue that a fighter pilot could be a civie on a training sortie because he does not fire his weopons in anger?.

BEagle

24th Jul 2006, 20:21

And for those who don't know, Art Field probably knows more about probe-and-drogue AAR than anyone else on this website. He started back in the days of the Valiant and was totally involved with all aspects of UK AAR until he retired.

Some of us who had more 'reactionary' ideas were frequently tempered by his sage views, so what he says I would endorse as being the voice of experience and sound advice.

Even if he did pinch most of the landings off his co-piglets....:p

Magic Mushroom

24th Jul 2006, 21:35

Further to Sonicstomp's comprehensive reply,
RAF E-3Ds (technically the French E-3Fs could easily have their probes refitted) are indeed the only aircraft in the world capable of drogue or boom refuelling on the same mission. From an AWACS mission crew point of view, boom is always the preferred option due to the faster flow rate which greatly reduces time off station if conducted mid-mission.

As SS says, until recently boom and drogue current captains were few and far between although I completed at least one mission during Allied Force where we took fuel from both boom and drogue on a single trip.

It's also worth noting that KC-135/KC-767 wing frogue pods are not compatible with heavy aircraft.

However, for sheer bizarre AAR methods, the now retired Soviet wing-tip to wing-tip method (conducted via Badgers and Bison IIRC) wins hands down!

Finally Brickhistory,
In many recent ops (especially OEF and OIF) AAR assets, in common with many other combat suport types such as AWACS, SIGINT and JSTARS, operated for extended periods outside of friendly airspace. A suggest a contractor would charge rather a lot for such a service. AAR is a military task. Period.

Regards,
MM

brickhistory

24th Jul 2006, 22:14

MM,

As a until recently qualified AWACS and JSTARS crewdog (motto: "One g and a cup of coffee!), I am fully aware of aircraft positioning in the theaters.

I also agree that AAR is, usually, a military function, and that to train uniformed crews to fly the missions in war that one needs realistic training; however, if other military support functions can and are contracted out, then why would refueling be so off limits in some scenarios? It was, mainly a hypothetical, but also to learn from others as well as, maybe refute BEagle's "mercenary" comments.

(As an aside, dear old departed Dad was a SAC tanker toad for his 23 yr career - KB-50s, KC-97s, KC-135s. Trust me, I heard about tankers!).

---------------------------------------------------------------------------------------------
edited to acknowledge D-IFF's point in a later post.

phil gollin

25th Jul 2006, 09:27

I posted this originally on the PPRUNE "Aviation History and Nostalgia" forum.

I only really only really re-post it to give the book reference for anyone interested in a technical history of Flight Refuelling Limited, from their successful pre-war civil work through to their latest efforts.

"QUOTE :-

Tiger Force air-to-air refuelling

I have often wondered about what was actually planned for the “Tiger Force” RAF Lancasters and haven’t really found anything (any references out there ?)

There is a recently published book “History of Air-to-Air Refuelling” (which isn’t what it says, but is really a TECHNICAL history of Flight Refuelling Limited).

Here is a summary of what it says about the Tiger Force Lancasters and flight refuelling (there are pages and pages of technical drawings and explanations showing how the system worked) from pages 24 to 34.

Following on from the successful pre-war "looped-hose" system, in 1942 the US Army Air Corps placed an order for a set of tanker and receiver equipment for a B-24 tanker and B-17 receiver aircraft. These conversions were completed and flight trials commenced in April 1943. The B-17’s range being “increased to 5,800 miles with full bomb load”. It was planned to take off from the Aleutians and land in China. These plans seem to have come to naught because of the time required to convert the aircraft and train crews and the coming of the B-29.

In the “latter part of 1943” there were plans made for the RAF to bomb Japan from bases in Burma. By 1944 it was decided that these were to be Lancasters equipped with the pre-war looped hose system (as were the B-17 and B-24). In January 1944 three different designs had been prepared, the third of which was adopted. In this the hose-drum and equipment was placed towards the front of the aircraft and the fuel supply consisted of two 640 imperial gallon (2,880 litres) tanks in the bomb bay.

50 sets of equipment were ordered for development and training. It was then intended to convert a total of 500 tanker and receiver aircraft to mount the long-range operations.

Originally the force was to be called “The Long-Ranged Force”

The prototype tanker (PB.972) and receiver (ND.648) aircraft had both been successfully flown by November 1944.

Not only were the two bomb bay tanks available, but also the Port and Starboard Inboard wing tanks (580 gallons [2,880 litres] in each)

The average fuel transfer rate was “better than100 imperial gallons (450 litres) per minute”.

AND;

“The trials for the Tiger Force operation were carried out with the prototype Lancaster tanker PB.972 and receiver ND.648, using the equipment described, and it proved that refuelling could be carried out at an indicated airspeed of 160 mph at any reasonable altitude, over or in cloud and at night, there being no difficulty in illuminating the receiver’s hauling cable.

Then, due to ”progress made in the Pacific Theatre” the whole programme of the Tiger Force was cancelled.

-------------------

The book later (page 39) states that post war that it supplied the US with sufficient equipment to convert 92 KB-29M aircraft to tankers and seventy-four B-29s and fifty-seven B-50As to receivers and implies that the 43rd Air Refuelling Squadron used this equipment in achieving their air-refuelled non-stop around-the-world flight between 26th February and 2nd March 1948 (???)

Any more info would be gratefully received"

Art Field

25th Jul 2006, 09:44

Guilty as charged on all counts.

BenThere

25th Jul 2006, 11:20

In my dotage I seem to recall the F-105 as having both probe and boom receptacle.

I had a job as a civilian flying Lear 35s under contract to the navy. We flew the admirals around, but also did target towing for navy training, threat simulation with electronic pods simulating Exocet and Silkworm attacks on fleet formations flying overwater at 100 feet, and approaching ships as intentional and inadvertant intruders. The pilot talent on this contract was extraordinary, nearly all of us being retired military pilots, and no active duty squadron was more gung-ho patriotic than our small group. Mr. BEagle would no doubt label us mercenaries, but I think it more accurate to say we were guys who enjoyed making a living while contributing as we could to the military mission. After all, the military often requires retirement at a time point when pilots are still approaching their peak in exerience and talent.

In the same sense, I don't see why civilian tankers couldn't perform, say, the first C-17 refueling out of Charleston in a private tanker, freeing up the limited active duty assets to perform mission refuelings 'over there'. They can also perform training and currency refuelings at home, which take up the biggest chunk of flying hours even during wartime.

As for the probe/drogue versus boom debate, I apparently stepped on BEagle's toes a bit, judging from his response, by saying the boom is the only way to go with a heavy receiver. In my reading, limited to redneck press I suppose, I never did come across the mission referred to, so, in my ignorance I shall stick to my position on the issue.

There are more inherent problems with multiple receivers on the hose simultaneously. Among them:

(a) Can anyone, including the 19 year old boom operator, monitor closure rate and erratic receiver performance on three aircraft at a time?
(b) Suppose TCAS alerts an RA with a climb command from a cruising A380 (hypothetical, of course).
(c) Communication congestion and confusion multiplies when trying to sort three receivers in contact at once. In critical situations, or even routine operations, it could be deadly.
(d) Drogues also increase drag, thus tanker fuel consumption hence offload capability. A single drogue fitted on a KC-135 incurs a 3% fuel penalty for the entire flight.
(e) A centerline refueling is always required for a heavy receiver due to interacting aerodynamics between tanker and receiver.
(f) The boom ably handles refueling speeds from slow for A-10s, C-130s, to fast. Didn't the SR-71 fuel at close to barber pole, 355 KIAS? Care to try that with a basket on a choppy day?

For these and other reasons, I still see boom refueling for heavies as the only way to go, any I have concerns with multiple drogues and concurrent refuelings off the same tanker.
Cheers,

brickhistory

25th Jul 2006, 11:28

BT,

The BLACK BUCK missions were really extraordinary feats of airmanship:

Reader's Digest version: A Vulcan and spare would launch from Ascension with a gaggle of Victor tankers, fly to FI, drop a load of 1000 lb'ers (and one Shrike mission), then come back using the same tankers who in the meantime had RTB'd, gassed up again and met the bomber. They used probe/drogue, had some drama on some sorties, one diverted, interned in Brazil briefly, etc. Great mission, probably not much gained tactically vs effort expended, but it scared the 'tines that a Vulcan could appear overhead Buenos Aires and they kept their Mirages at home for air defense and quit using them on FI strikes.

But, if they'd have used the boom method, it would have gone a lot faster!

ORAC

25th Jul 2006, 12:14

a) Can anyone, including the 19 year old boom operator, monitor closure rate and erratic receiver performance on three aircraft at a time?
(b) Suppose TCAS alerts an RA with a climb command from a cruising A380 (hypothetical, of course).
(c) Communication congestion and confusion multiplies when trying to sort three receivers in contact at once. In critical situations, or even routine operations, it could be deadly.
(d) Drogues also increase drag, thus tanker fuel consumption hence offload capability. A single drogue fitted on a KC-135 incurs a 3% fuel penalty for the entire flight.
(e) A centerline refueling is always required for a heavy receiver due to interacting aerodynamics between tanker and receiver.
(f) The boom ably handles refueling speeds from slow for A-10s, C-130s, to fast. Didn't the SR-71 fuel at close to barber pole, 355 KIAS? Care to try that with a basket on a choppy day?

a. One advantage of P&D is there is no need for a boom operator. The current limit is two receivers (wing hoses, you can´t use all 3 at once - though someone did ask during GW1 and got a short pithy reply from Command). Monitoring 2 never was a problem, you just got one to wait till the first was in contact.

b. I can´t see where it would be more of a problem to do a break from a hose than a boom.

c. USAF tend to use a discrete boom freq, RAF tends to use the same freq as the tanker crew. One way is quieter, the other provides more SA, and you don´t get the hassle of changing freq when close to a formation. Radio discipline seemed to keep it under control, though if the tanker controller had a lot of chicks transiting to and from the towline you did get requests for it to take place on a separate freq and chopped them across at about 30nm, Judy.

d. I presume you are referring to the BDA, the pods on a P&D tanker may give a bit of drag, but I doubt much worse than a boom, and at a lower weight penalty.

e. A very dogmatic statement to a group including L1011 and E3D pilots who have done it on many occasions.

f. Want to show me how a boom tanker handles refueling helos?

A boom gives a higher fuel give away than a hose, but hoses allow more flexibility with 2 FJ receivers at once. FJ refuel transfer rates are invariably governed by the FJ, so the booms greater capacity is no advantage. P&D is also suitable for smaller tactical tankers and buddy-buddy pods, hence their use by the navy. Ever seen a boom equipped tanker on a carrier?

The final point above leads to one of the main shortsighted decisions of the USAF, not to fit P&D pods to all their KC-135s. Hence the RAF having to provide heavy support to the USN/USMC in GW1 and GW2 ten years later. Even now the number so equipped is limited.

You may find this 2006 CRS Report for Congress (http://www.fas.org/sgp/crs/weapons/RL32910.pdf)interesting:

At least five studies have examined the pros and cons of a single boom versus multipoint hose-and-drogues. Because these studies considered different operationalfactors in their analyses and made different assumptions, they came to different conclusions. However, all found that tankers equipped with multipoint hose-and-drogue refueling would refuel combat aircraft more effectively than boom equipped aircraft and could therefore allow a reduction in the tanker fleet. Reduction estimates ranged from 17 to 50 percent....

BenThere

25th Jul 2006, 12:43

Good points, ORAC. You say L1011s and E3s refueled from wing-mounted pods? I didn't know that. Hope they had a very long hose.

I think probe and drogue has a place, and I want to retreat from a conception that I advocate boom only systems. My real point is that the boom system should never be eliminated in favor of a probe and drogue only doctrine.

I'm not comfortable with simultaneous closure and contact of multiple receivers without tanker monitoring and positive, direct communications, even though the receiver is indeed doing all the work.

The breakaway problem with TCAS does apply to boom refuelings, as well, but is complicated further with multiple receivers on the baskets.

ORAC

25th Jul 2006, 13:49

I presumed you meant centreline boom, not centreline hose, my apologises.

No, they cant use the wing hoses, have to use the centreline. The lower wing fuel flow rate wouldn´t help either. Which means the hassle of reeling in the wing hoses and streaming the HDU and then changing it all back out again for the FJs if there are more than a handful.

Art Field

25th Jul 2006, 14:10

The twin refuelling from pod equipped P and D tankers shows a greater advantage over a single boom when you consider the limited on-load rate of certain receivers. I do not know if the Typhoon is limited but the Tornado certainly is. The offload system should limit itself to the on-load capability but there can be problems as tank shut off valves close approaching full.

As far as large receivers on wing hoses are concerned, that really is a no-no. The rolling effect of the tankers wash is much greater the wider the wingspan of the receiver and therefore, though not impossible, is much closer to, if not outside, acceptable safety limits. Has been tried, not nice, not recommended.

BenThere. Twin receiving, indeed all RAF refuelling [English spelling],is monitored using rear facing television.

As far as Black Buck was concerned the maximum offload rate was just over 4000 lb/min but reducing steadily as tanks became full, a receiver limitation. Am I right that the booms max is about 6000 lb/min?. A greater problem was the setting up of the refuelling equipment. The posters managed to move on the experts just before Corporate so the new guys were struggling to adjust the settings correctly which lead to incorrect signal light indications.

BenThere

25th Jul 2006, 15:26

Another aspect is the time from pre-contact to boom engaged versus approach to and latching with the probe.

An experienced fighter pilot can park in pre-contact and move to boom engaged in ten seconds or so, having the advantage of receiver director lights, aircraft markings, and assistance from the flying moveable boom and its operator. Empirically speaking, I think the drogue takes quite a bit longer on average, often after comical contortions.

A wise pilot once told me (in a commercial environment): "The only thing we have to sell in aviation is time." In a military refueling variation of the same concept, the only things we have to sell are range, reach, and time on target." In that sense, very marginal optimizations pay large dividends. I still have to go with using the boom as a preference.

The risk of leaving the probe in the basket, while inconvenient in training scenarios, can be mission critical when it counts, if there is no good 'no AAR' option.

If I had a small air force with only probe receivers, I'm sure I would look at it another way. The only advantage of having a boom would be in multinational ops with boom equipped receivers.

To all, I'm enjoying this good discussion.

D-IFF_ident

25th Jul 2006, 15:51

I don't think the PDIs work until the receiver is in contact - unless the ARO flashes them manually. Time from visual the tanker to fuel flowing depends largely on the receiver pilot, but also on joining techniques. ATP 56/A/B has the receiver join echelon, then move astern - so an substantial overtake can work, the energy being bled in the join. Some nations with Boom refuelling equipment join straight to astern the equipment, demanding a longer, more drawn out 'reverse PAR' from a mile or more. SO I would say getting on a hose is probably quicker. However, once in contact the argument is one of flow rates and simultaneous top-offs. If I flew fighters then I'd look for 2 hoses on one tanker - have us both filled to full at the same time and not taking a great deal of fuel. But, if I was a heavy aircraft pilot I'd look for a boom. Were I to be taking-on 80 tons, I'd rather do it in 10 minutes than 40 minutes.

That's why the boom was developed isn't it? To refuel bombers for 'force extensions', whereas the probe and drogue came about more for small aircraft?

My dear old Dad was an AEO on Nimrods. Believe me, I know nothing about maritime aviation.

Art Field

25th Jul 2006, 16:39

D-IFF_ident. Your dear old dad spent too much time eating pies rather than teaching you maths. If a Tristar transfers 80 tonnes in 40 min by P and D then a KC10 will take 25 min not 10 using its boom. Yes a difference but not that great.

On the joining issue. The echelon join has proved significantly faster every time because of the freedom to manoeuvre right up to the move astern at the last minute.

My dear old dad was an accountant. As a mess sec I soon found out I knew nothing about accountancy.

sonicstomp

25th Jul 2006, 17:16

Art - the reality for heavy receivers is that there is little time saving from an echelon join vs straight-in astern (used for boom)......On the E3 we teach the same closure speeds for both...the echelon join is inherently safer as more of the window is available as an escape exit!:eek:

D-IFF_ident

26th Jul 2006, 04:16

Art,

My apologies; I've got used to thinking in Lbs. Therefore, to clarify:

Tri* offloading 80KKg of fuel at 2200Kg/min - (ATP56(A) - http://www.raf.mod.uk/downloads/documents/Pt2/Pt2Ch10P-UnitedKingdom.pdf)

Time to offload = 37 mins (including a few seconds to push the hose in)

KC-10 offloading 80KKg of fuel at 3630Kg/min - (ATP56(A) - http://www.raf.mod.uk/downloads/documents/Pt2/Pt2Ch10Q-UnitedStatesofAmerica.pdf)

Time to offload = 22 mins (including half a second for the BO to put his playboy down).

That difference seems substantial to me.

Maybe more important though, is the receiver's ability to take fuel at a decent rate - microbore pipes and a P and D, or a big fat tube and all 6 pumps? Fnnarr fnnarr...

It's even quicker if you're download Lbs, isn't it?

Art Field

26th Jul 2006, 14:15

D-IFF_ident. My figures agree, I rounded off to allow for slowdown as tanks fill, as you say receiver plumbing is always relevant. I would have been very grateful for any lessening of on-load times. I still think the flexibility of the P and D system in a mixed fleet like ours is the best solution.

Being now some time removed from the action and never having prodded with the E3 I am wary of jumping in but feel I am a little surprised they do not believe they can join in echelon and get behind the hose any faster than a line astern join. The echelon join worked best for all the other multis I flew.

Brain Potter

26th Jul 2006, 17:11

In recent ops the refuelling slot time required by SPINS to deal with a 4-ship was significantly longer than was routinely achieved by 2 point P&D tankers. I don't know if this is because it takes longer to cycle a 4-ship through a boom or if the slot times were too conservative. I think the higher onload rates achievable by US fighters reduce the disadvantage of only being able to fill one at a time. The lower onload rates of European fighters increases the value of multipoint refuelling. However, it would be an interesting comparison to see if a 4-ship of F-18s cycling through a 2-point tanker would be done quicker than a 4-ship of F-15s taking the same fuel from a boom. Also, I bet that the first F-18 to plug would leave the tanker with an equivalently better fuel state than the lead F-15 - hence the formation as a whole is better placed. If TAC had been the dominant force in the USAF in the 1950s and 1960s would they have retained P&D? As it was, SAC owned the tankers, which were primarily for the bomber force, and the boom was adopted.

TCAS will not cause RAs and breakaways as it should be set to "TA only".

My dad knows nothing about tankers. But would he have agreed to a new tanker that cannot receive fuel itself?

sonicstomp

26th Jul 2006, 17:33

Art - Any speed advantage from the join to echelon is then lost waiting for a clearance and the move to astern....Indeed our SOPs have our overtake on the tanker the same irrespective of whether it is an echelon join or straight to astern...(+30kts at 2nm, +20kts at 1nm, +10kts at 0.5nm - At night we generally will go for +20 at 2, +10 at 1 etc....)

Brain - TCAS will be off as M3 will be strangled on the "Judy/Visual" call at the end of the RV phase and the start of the "join-up" phase.

BenThere

26th Jul 2006, 17:58

The tanker will set TA only, but conflicting traffic will be in TA/RA. The tanker's TA only alert will still display the conflict. If the tanker formation chooses the same judgmental resolution as the conflicting traffic's RA computer demands, there is increased chance for collision. Is the best procedural option to ignore TCAS assuming the bogey will resolve any conflict?

D-IFF_ident

26th Jul 2006, 22:36

Brain, I'll time it and let you know. ;)

I've found that a keen eng with post AAR checks really wakes you up when he switches to TA/RA before the rcvr departs...

Brain Potter

26th Jul 2006, 23:45

Not all receivers switch of their Mode3/C at the Judy/Visual call. In fact leaving it on as long as possible provides good SA for a TCAS equipped tanker, particularly during autonomous joins. The tanker's TCAS must be in TA or an RA could well be generated by the receivers transponder. A large receiver being particularly careful to strangle parrot whilst closing may not cause an RA, but fast movers with high rates of climb certainly would. Departing aircraft would probably also trigger an RA when they switch their transponder back on - as related by D_IFF . Leaving the TCAS in TA/RA would put too far much onus on the receiver to fly a very mild join, switch the transponder off early and be very careful where it was switched back on. Most receivers are not TCAS equipped and so do not really know the parameters that would cause the various alerts. As AAR usually takes place in fairly well protected airspace and an RA with receivers in contact could not be actioned safely within the timescale that the system demands, it is much safer to set TA only. At least a TCAS equipped intruder would not expect a co-ordinated RA. It is exactly the same principle that calls for the TCAS to be set to TA when engine-out etc.

SS - I would expect a large receiver to reduce to a max 30 kts overtake at 2nm, whilst maintaining a 1000' split and then to kill the overtake with a climb to wide echelon commencing at 0.5 nm. It is easy then to slide into close-ish echelon, before being cleared astern. The tanker does not expect to see a perfect close echelon before clearing the receiver astern - just a safe enough postion with no overtake from which the receiver will drop back to go astern. If you make your "Echelon Right" call when you are ready to start moving astern there should be no delay in receiving clearance to move - even if it is from quite a wide echelon and still with some vertical spilt. The tanker just doesn't want you to go behind whilst still moving forward with no escpe route. I guess the pre-contact postion on the boom must have more vertical seperation than that of the centreline hose - allowing an escape route downwards as you join astern.

D_IFF. If the F-15s win then I'll swap the hose jets to F-14s :)

I think the Indian IL-78s can refuel 3 jets simutaneously :eek:

Art Field

27th Jul 2006, 09:49

Brain Potter. many are with your old dads thoughts about a receiver capability for FSTA [should it ever arrive] but in the real world you get what you ask for or more certainly you do not get what you do not ask for. One more example of the "we will never need to do that again" mentality.
I know the Tri motor guys hated the probe, the airflow noise kept them awake.:) :)

BEagle

27th Jul 2006, 15:26

A330MRTT for the OzAF will have a receptacle, but as for the Fictional Strategic Tanker Aircraft, I don't think so.

Unfortunately the USAF is still very boom-obsessed and the boom operator mafia have too great a stranglehold, for my money. If only, as has been said earlier, TAC and the USN had held the upper hand rather than SAC, then perhaps things would be different today....

Even the OzAF were surprised to hear that the RAF operated large aircraft in echelon with no problems; the boom mafia had tried to convince them that the slow join to astern was the only way.

bounce'em all

30th Jul 2006, 17:59

The RAF E-3D has both probe and receptacle. As far as I'm aware, it is the only bisexual receiver in RAF service; every other reciver uses the 'male' probe-and-drogue technique rather than the 'female' boom-and-receptacle method.

The BDA is a truly dreadful device.I had to prod against it with a Q-fit Phantom (8 missiles, 3 tanks) once without ever having had any dual instruction.... You are supposed to make contact very slowly, then push until valves at both ends of the adaptor open; the hose ends up in a sort of S-bend shape and is highly likely to snap the probe off as allowable positional tolerance is much less than with a proper hose - and if you miss on the approach to contact the boom person is likely to move the damn thing. It doesn't have any hose response system and seems to rely purely on hose flex to compensate for receiver movement. It truly sucks!

I don't think that any large aircraft are cleared to use the BDA - and detcos in Incirlik certainly weren't happy to let some UK aircraft prod against it.

BEagle, first of all, my utmost respect to a Phantom driver.
I couldn't have described it better. I guarantee, it's still a b**** on a lighter but fully loaded fighter. No dual instruction as well: first time I had to do it, the colourful brief received wasn't much help really....

BEagle

30th Jul 2006, 19:37

Perhaps I should have added, this was on a live QRA(I) scramble.....

No proper brief, no dual instruction.......it wasn't easy! But having the genial E**c H**p in the back was a great help, he gave me some very good guidance when I was trying to work out what to do...

But what really annoyed me was that the miserable Flt Cdr criticised me for the time I'd taken to get the gas against the infernal donkey cock. Yet a few months later, he had the temerity to signal Gp (after the rest of the Sqn had being doing some dual trips in Charlie fit against the BDA) to say that it was so difficult that dual continuation training was essential. Pricks like that you just don't want to work for - so glad I was off to the pre-VC10K MER a week or so later!

bounce'em all

30th Jul 2006, 23:05