Air to Air refueling.Would you contemplate it?
Do a Hover - it avoids G
Join Date: Oct 1999
Location: Chichester West Sussex UK
Age: 91
Posts: 2,206
Likes: 0
Received 0 Likes
on
0 Posts
Art
I had in mind a FBW droque with vanes that control it onto the probe as was suggested to Cobham by a bunch of students a couple of years ago. Cobham were well impressed but felt the military could cope as is and so there would be no return on the R&D
BEags
You are dead right about flow rates being higher with a boom of course. But I don't see why a tanker should have an ATC delay on take-off as it would not have to operate from a busy airport.
exvicar
The reason to fly lower (below the trop) is that pollution is a much less of an issue in the troposphere where mixing and washing occurs. Above the trop in the stratosphere pollutants get relatively trapped and build up much more.
I am not arguing in favour of AAR for airliners just trying to stop people being unreasonably dismissive by only listing disadvantages. There are a variety of advantages to the notion and only a properly balanced study will decide whether the idea should be actively studied or shelved pending XYZ..
JF
I had in mind a FBW droque with vanes that control it onto the probe as was suggested to Cobham by a bunch of students a couple of years ago. Cobham were well impressed but felt the military could cope as is and so there would be no return on the R&D
BEags
You are dead right about flow rates being higher with a boom of course. But I don't see why a tanker should have an ATC delay on take-off as it would not have to operate from a busy airport.
exvicar
The reason to fly lower (below the trop) is that pollution is a much less of an issue in the troposphere where mixing and washing occurs. Above the trop in the stratosphere pollutants get relatively trapped and build up much more.
I am not arguing in favour of AAR for airliners just trying to stop people being unreasonably dismissive by only listing disadvantages. There are a variety of advantages to the notion and only a properly balanced study will decide whether the idea should be actively studied or shelved pending XYZ..
JF
Per Ardua ad Astraeus
Join Date: Mar 2000
Location: UK
Posts: 18,579
Likes: 0
Received 0 Likes
on
0 Posts
Sounds a good idea but we will need to resolve a few issues first
Technically possible - without doubt
Within average pilot skills (with given augmentation) - without doubt
Commercially a dead duck. Incidentally Beagle's 'slot delays' were for the receivers.
What does the tanker do? Racetrack or straight line? If the former, there would be multiple loops of the track to take on the quantities we are talking about, with enormous wastage of fuel going nowhere. When No1 in the plan gets delayed by late bags or ATC slot, No2 presumably 'slots in' when it arrives, making No 1 wait while No 2 tanks when No 1 arrives. Assuming gargantuan efficiency in planning, No 3 will then be waiting for his 'scheduled' tank when No 1 gets his. Do we go on? If a 'straight line' tank, poor old No1 cannot catch up with the tanker which has gone off along the route with No2. How much 'redundancy' do you build in for such 'misfires' of the plan? More fuel burnt by the tankers.
Now airspace - for race-track tanking, with one fueling and one waiting, we block off half of the North Sea. I actually do not think there is airspace for it. Having been rolled out in front of a tanker at least once, I can see some of our brethren finding a few difficulties too!
just trying to stop people being unreasonably dismissive by only listing disadvantages
Anyway - who is going to give Ryanair any fuel without a signature....
Do a Hover - it avoids G
Join Date: Oct 1999
Location: Chichester West Sussex UK
Age: 91
Posts: 2,206
Likes: 0
Received 0 Likes
on
0 Posts
Chaps
I understand why practical aviators with AAR and airline experience see so many problems.
However although I consider myself a (former) practical aviator I do not feel I have the intellectual hoprsepower to say 'rubbish' or simply 'no' in the face of the following:
The proposal has been put forward in a report by the Royal Aeronautical Society’s Greener by Design group. The group includes representatives from the Department for Transport, Airbus, Rolls-Royce and Cranfield University.
Of course I WOULD like to ask them a bunch of stuff. In the event they have the right answers I would then say 'Cor!'
JF
I understand why practical aviators with AAR and airline experience see so many problems.
However although I consider myself a (former) practical aviator I do not feel I have the intellectual hoprsepower to say 'rubbish' or simply 'no' in the face of the following:
The proposal has been put forward in a report by the Royal Aeronautical Society’s Greener by Design group. The group includes representatives from the Department for Transport, Airbus, Rolls-Royce and Cranfield University.
Of course I WOULD like to ask them a bunch of stuff. In the event they have the right answers I would then say 'Cor!'
JF
Join Date: Jan 2002
Location: Brisbane, Australia
Posts: 960
Likes: 0
Received 0 Likes
on
0 Posts
Hi guys,
Just to throw a cat among the pidgeons, there are B737NGs currently flying around with both an AAR and Fuel Jettison capability.
You guessed it, they are military modified airplanes flown by military pilots, without paying pax aboard!
Taking into account the very low fuel flow of an 737 at MRC or LRC speeds, these things should be able to stay inflight for a very long time!
Just thought I'd mention it!
Cheers, FD
Just to throw a cat among the pidgeons, there are B737NGs currently flying around with both an AAR and Fuel Jettison capability.
You guessed it, they are military modified airplanes flown by military pilots, without paying pax aboard!
Taking into account the very low fuel flow of an 737 at MRC or LRC speeds, these things should be able to stay inflight for a very long time!
Just thought I'd mention it!
Cheers, FD
One wonders whether the 'Rolls Royce and Airbus' representatives were people with an interest in trying to find some way of achieving 'third party revenue' with the Rental Air Force's proposed AirTanker A330 MRTT a/c when they are not refuelling the remaining handful of serviceable RAF 'fast' jets...??
I still do not understand what the basic reasoning behind such an expensive, fuel guzzling idea is supposed to be......
Regarding lower cruise levels, perhaps the Boeing Pelican 'ground effect' design is the ultimate? They claim that it could transport 750 tons over 10,000 nm when cruising in ground effect, but only 6,500 nm when cruising out of ground effect.
I still do not understand what the basic reasoning behind such an expensive, fuel guzzling idea is supposed to be......
Regarding lower cruise levels, perhaps the Boeing Pelican 'ground effect' design is the ultimate? They claim that it could transport 750 tons over 10,000 nm when cruising in ground effect, but only 6,500 nm when cruising out of ground effect.
Yes, Him
Join Date: Aug 1999
Location: West Sussex, UK
Posts: 2,689
Likes: 0
Received 0 Likes
on
0 Posts
Off topic for a sec, personal bee in bonnet, sorry chaps.
As a pax I'd be more comfortable if there were not a half ton or so of duty free inflammable spirits in glass bottles in the overhead lockers. Buying DF at destination should be adopted.
As a passenger I would be pleased not to have 20 hours fuel on board when any abnormality transpired during take-off.
Join Date: Oct 2003
Location: London
Posts: 182
Likes: 0
Received 0 Likes
on
0 Posts
Whilst it might be technically possible I don't think it would be cheaper than a tech stop, and wouldn't reduce airfares.
The one item missing from the debate is the view of Joe Passenger.
If you talk to a passenger travelling economy after a flight from SIN-LHR or LAX-SYD I don't think the prospect of another 6 or 7 hours sitting in the same seat would have much appeal.
Add to that the whole debate on DVT and I think it is a non starter. Some airlines such as SQ are thinking in terms of an upgraded economy product on their ER aircraft but I cant see the majors taking half the seats out to allow a promenade deck.
It might work for an all business class point to point service from say LHR to SYD with a few extras such as on request oxygen/water vapour masks, and space to walk/shower etc but I have my doubts.
The one item missing from the debate is the view of Joe Passenger.
If you talk to a passenger travelling economy after a flight from SIN-LHR or LAX-SYD I don't think the prospect of another 6 or 7 hours sitting in the same seat would have much appeal.
Add to that the whole debate on DVT and I think it is a non starter. Some airlines such as SQ are thinking in terms of an upgraded economy product on their ER aircraft but I cant see the majors taking half the seats out to allow a promenade deck.
It might work for an all business class point to point service from say LHR to SYD with a few extras such as on request oxygen/water vapour masks, and space to walk/shower etc but I have my doubts.
Seat A1,
As someone who does the UK-Aus trip, let me tell you that the simple fact is you are spending 20 hrs in a seat regardless. The only difference is- are you going through the stress, inconvienience and possibly catastrophic disruption (Tech problems, missed connections, booking foul ups etc. etc.) of getting out of that seat half way, sitting around a terminal for a few hours, then getting back into that seat for the completion of a 32 hr point-to-point trip.
Sit down in London, get up in Sydney? Yes Please!!
As someone who does the UK-Aus trip, let me tell you that the simple fact is you are spending 20 hrs in a seat regardless. The only difference is- are you going through the stress, inconvienience and possibly catastrophic disruption (Tech problems, missed connections, booking foul ups etc. etc.) of getting out of that seat half way, sitting around a terminal for a few hours, then getting back into that seat for the completion of a 32 hr point-to-point trip.
Sit down in London, get up in Sydney? Yes Please!!
Mach 3
Join Date: Aug 1998
Location: Stratosphere
Posts: 622
Likes: 0
Received 0 Likes
on
0 Posts
Hey John,
I've done enough time in R&D to know "Never say "Never"!"
Economics versus Environmental Science?
The balance of power between the two may shift somewhat in the future but I suggest not at $60/barrel and, even then, only when the USA says it should.
Unfortunately.
I'm not a meteorologist, but even at FL370 I come across some pretty significant winds over NW Europe. No doubt aviators up in the 400's do too?
That suggests to me there is some signifcant atmospheric mixing going on even up there... Maybe only in a horizontal sense though?
You're saying there isn't much vertical mixing (How the hell is Steve Fosset going to get to 100,000ft in a glider then?) and the particulate matter can't break through the tropopause?
Doesn't that generalisation really depend on what latitude you're at?
Ignorantly.
If they didn't I rest my case.
Economics versus Environmental Science?
The balance of power between the two may shift somewhat in the future but I suggest not at $60/barrel and, even then, only when the USA says it should.
Unfortunately.
I'm not a meteorologist, but even at FL370 I come across some pretty significant winds over NW Europe. No doubt aviators up in the 400's do too?
That suggests to me there is some signifcant atmospheric mixing going on even up there... Maybe only in a horizontal sense though?
You're saying there isn't much vertical mixing (How the hell is Steve Fosset going to get to 100,000ft in a glider then?) and the particulate matter can't break through the tropopause?
Doesn't that generalisation really depend on what latitude you're at?
Ignorantly.
Join Date: Oct 2002
Location: Heathrow
Posts: 291
Likes: 0
Received 0 Likes
on
0 Posts
Wouldn't the environmentalists complain about stuff in the oceans if we flew lower and it got washed out?
Its interesting seeing this discussion develop. I must admit, I saw the article and thought it must be April Fools day.
I would love to have a go at tanking and it is obviously possible, but on a large scale as suggested?
The guys at Cranfield et al command a huge amount of my respect, but this does remind me of the Cranfield boffs who said we could fly LHR-SYD via space by 2000.
Its interesting seeing this discussion develop. I must admit, I saw the article and thought it must be April Fools day.
I would love to have a go at tanking and it is obviously possible, but on a large scale as suggested?
The guys at Cranfield et al command a huge amount of my respect, but this does remind me of the Cranfield boffs who said we could fly LHR-SYD via space by 2000.
Join Date: Jun 2002
Location: Wor Yerm
Age: 68
Posts: 4
Likes: 0
Received 0 Likes
on
0 Posts
So we take off with bugger all fuel. Then ask for radar vectors so we are in exactly the same piece if air as somebody else (after having turned the transponders to one click less than TA). Then fly MANUALLY (how do you do that?) to make a lump of scaffold pole bumb into an oversize shuttlecock, fill up the plane with probably the most expensive juice known to man and then go to where we could have probably gone in the first place, had we put enough fuel in . And the CAA (amongst others) will say...
I think not!
I think not!
Then fly MANUALLY (how do you do that?) to make a lump of scaffold pole bumb into an oversize shuttlecock,
the same way military pilots have been doing it since the 1950s'!?!
Without looking at the original data, my guess would be that the people who came up with this idea are right, but also wrong.
They are right that the longer you fly, the more fuel per mile you burn, other things being equal - because on an 8000 mile sector you have to carry the last pound of fuel that you burn for 8000 miles. Adam Brown of Airbus used to twit Boeing with the fact that Condit once claimed that ultra-long nonstops saved fuel.
On the other hand, I wonder if they have factored the fuel used by the tanker into the equation, let alone taken account of ascent/descent, allowances for missed refuelings, multiple attempts and so on. At that point, you might save more fuel by making a fuel stop.
They are right that the longer you fly, the more fuel per mile you burn, other things being equal - because on an 8000 mile sector you have to carry the last pound of fuel that you burn for 8000 miles. Adam Brown of Airbus used to twit Boeing with the fact that Condit once claimed that ultra-long nonstops saved fuel.
On the other hand, I wonder if they have factored the fuel used by the tanker into the equation, let alone taken account of ascent/descent, allowances for missed refuelings, multiple attempts and so on. At that point, you might save more fuel by making a fuel stop.
Do a Hover - it avoids G
Join Date: Oct 1999
Location: Chichester West Sussex UK
Age: 91
Posts: 2,206
Likes: 0
Received 0 Likes
on
0 Posts
Some may find enjoyment in shooting messengers but such a practice (however inconveniently) does not of itself invalidate the message. I didn’t invent the physical laws that define the way our atmos behaves so give me a break. In a similar vein the fact that boffins said we could do something by a certain date is not at all the same as saying we would.
SR71 On a more practical point I understand Steve Fossett is looking to use a standing wave which while not occurring too often as high as 100K does happen much more frequently than thermal mixing in the absence of a lapse rate! You were dead right that what we feel is going on (often as CAT) is thanks to the marked horizontal sheers caused by jet stream activity. The height of the tropopause is a most variable feast and I believe has been detected as low as 25 and as high as 55 even though we tend to think of it in ISA terms as about 35. In the end the troposphere and the stratosphere are just bands of atmos inside which certain observed conditions apply that happen to keep them from mixing into one single layer.
Chaps - purely by chance I had to attend functions at the SBAC and Dti today in respect of engineering educational matters. Imagine my surprise (or not) when I was grabbed by senior wheels and had my ear filled to the brim not with the newspaper article (that has clearly got to a few PPRuNers) but with the technical paper behind the article. But for goodness sake don’t read it as I hate to see grown men loose confidence in themselves.
I am so f-ing knackered after today that I can’t believe I am taking this thread seriously again.
SR71 On a more practical point I understand Steve Fossett is looking to use a standing wave which while not occurring too often as high as 100K does happen much more frequently than thermal mixing in the absence of a lapse rate! You were dead right that what we feel is going on (often as CAT) is thanks to the marked horizontal sheers caused by jet stream activity. The height of the tropopause is a most variable feast and I believe has been detected as low as 25 and as high as 55 even though we tend to think of it in ISA terms as about 35. In the end the troposphere and the stratosphere are just bands of atmos inside which certain observed conditions apply that happen to keep them from mixing into one single layer.
Chaps - purely by chance I had to attend functions at the SBAC and Dti today in respect of engineering educational matters. Imagine my surprise (or not) when I was grabbed by senior wheels and had my ear filled to the brim not with the newspaper article (that has clearly got to a few PPRuNers) but with the technical paper behind the article. But for goodness sake don’t read it as I hate to see grown men loose confidence in themselves.
I am so f-ing knackered after today that I can’t believe I am taking this thread seriously again.
JF:
"But for goodness sake don’t read it as I hate to see grown men lose confidence in themselves."
Which 'grown men'?
OK - I'll be blunt. From a country which produced the sort of brains which came up with Concorde and Harrier, this proposal for airline AAR is, quite honestly, barking mad boffin stuff.
An airliner is supposed to fly 3000 miles between AAR sessions, is it, green boffins? Call that 6 hours at a still-air TAS of 500 KTAS. At 5 tonne per hour (typically), that's 30 tonne of fuel. Receiving it at even 2 tonne per minute (pretty optimistic) would take 15 minutes in contact; at tanking speeds that's a still air distance of well over 100 nm. So our airliner takes off, climbs to opt cruise, descends into a 100nm+ AARA, RVs with a tanker, takes on 30 tonne of fuel, then climbs back to opt cruise......and does that every 5 hours on its way to Australia? That'd mean a refuelling bracket in the North Sea, another over Siberia and a final one over the Phillipines. Personally I wouldn't by a ticket for a flight which might dump me in the middle of nowhere after a failed AAR RV - but perhaps the green boffins know better?
"But for goodness sake don’t read it as I hate to see grown men lose confidence in themselves."
Which 'grown men'?
OK - I'll be blunt. From a country which produced the sort of brains which came up with Concorde and Harrier, this proposal for airline AAR is, quite honestly, barking mad boffin stuff.
An airliner is supposed to fly 3000 miles between AAR sessions, is it, green boffins? Call that 6 hours at a still-air TAS of 500 KTAS. At 5 tonne per hour (typically), that's 30 tonne of fuel. Receiving it at even 2 tonne per minute (pretty optimistic) would take 15 minutes in contact; at tanking speeds that's a still air distance of well over 100 nm. So our airliner takes off, climbs to opt cruise, descends into a 100nm+ AARA, RVs with a tanker, takes on 30 tonne of fuel, then climbs back to opt cruise......and does that every 5 hours on its way to Australia? That'd mean a refuelling bracket in the North Sea, another over Siberia and a final one over the Phillipines. Personally I wouldn't by a ticket for a flight which might dump me in the middle of nowhere after a failed AAR RV - but perhaps the green boffins know better?
Do a Hover - it avoids G
Join Date: Oct 1999
Location: Chichester West Sussex UK
Age: 91
Posts: 2,206
Likes: 0
Received 0 Likes
on
0 Posts
BEags
Thanks for that. As ever you have put your finger on the crux of the matter. Such a process will never be certificated unless it is shown to be safe and reliable – as I remarked in my first post.
But in my view all the rest of the objections offered in this thread are invalid knee jerk reactions unworthy of professionals.
We are all entitled to our own best guess as to whether the necessary reliability and safety could be developed and proven (given the costs against and the ‘green’ pressures for). I would guess not, but that is not the same thing as just shouting “Rubbish!”
JF
Thanks for that. As ever you have put your finger on the crux of the matter. Such a process will never be certificated unless it is shown to be safe and reliable – as I remarked in my first post.
But in my view all the rest of the objections offered in this thread are invalid knee jerk reactions unworthy of professionals.
We are all entitled to our own best guess as to whether the necessary reliability and safety could be developed and proven (given the costs against and the ‘green’ pressures for). I would guess not, but that is not the same thing as just shouting “Rubbish!”
JF
Mach 3
Join Date: Aug 1998
Location: Stratosphere
Posts: 622
Likes: 0
Received 0 Likes
on
0 Posts
I don't understand...
In this business you have a 735 which will operate a 1000nm sector and a A345/777ER which will operate a 9000+nm sector. There will come a day soon when 10000+nm is possible. No doubt already is in low density configurations.
There are products which offer you ranges in between the above.
Lets assume that the product you want to operate over the range you need has the right capacity.
Conclusion: AAR not required.
So the question only arises when you want to operate a low density long range route for which no product exists. (I take the view that the A380 has been sized correctly to deal with high density longest range routes. Pretty silly if it wasn't!)
In the long run I cannot see how it is not better to design your aircraft to meet the operating criteria rather than endeavour to get a sub-optimal product to do the job via AAR? This is proposed as a short term fix which will, bearing in mind the objections mentioned already, will require significant investment for what ultimate gain?
Taking a long term view, I just don't see the point of AAR unless the big A and B are going to stop building the aircraft that their customers need.
I can quite believe there is good science behind it but strategically?
In this business you have a 735 which will operate a 1000nm sector and a A345/777ER which will operate a 9000+nm sector. There will come a day soon when 10000+nm is possible. No doubt already is in low density configurations.
There are products which offer you ranges in between the above.
Lets assume that the product you want to operate over the range you need has the right capacity.
Conclusion: AAR not required.
So the question only arises when you want to operate a low density long range route for which no product exists. (I take the view that the A380 has been sized correctly to deal with high density longest range routes. Pretty silly if it wasn't!)
In the long run I cannot see how it is not better to design your aircraft to meet the operating criteria rather than endeavour to get a sub-optimal product to do the job via AAR? This is proposed as a short term fix which will, bearing in mind the objections mentioned already, will require significant investment for what ultimate gain?
Taking a long term view, I just don't see the point of AAR unless the big A and B are going to stop building the aircraft that their customers need.
I can quite believe there is good science behind it but strategically?
Do a Hover - it avoids G
Join Date: Oct 1999
Location: Chichester West Sussex UK
Age: 91
Posts: 2,206
Likes: 0
Received 0 Likes
on
0 Posts
SR71.
I see what you are getting at. The case FOR is as simple as this:
The sums for a cruising aeroplane show a lower fuel burn at a lighter weight.
The fuel used climbing from take-off to the cruise is very sensitive to takeoff weight.
Because of this a technical case has been made that if AAR was used – even allowing for the tanker fuel – then less fuel per pax would be needed on long routes. Toss in the way aircraft could be made lighter if they never had to be capable of containing as much fuel in the first place and very soon a virtual circle develops.
BUT this analysis does not allow for two things.
1 BEag’s safety issue
2 Market resistance to the investment needed (scrap existing types early, develop new versions, develop auto tanking) for a limited advantage.
Without wishing to flog a dead horse we have just about cracked the provision of types that will go half way round the world non stop. So what next? One answer has been for people to say a step change in fuel burn could be achieved using AAR.
JF
I see what you are getting at. The case FOR is as simple as this:
The sums for a cruising aeroplane show a lower fuel burn at a lighter weight.
The fuel used climbing from take-off to the cruise is very sensitive to takeoff weight.
Because of this a technical case has been made that if AAR was used – even allowing for the tanker fuel – then less fuel per pax would be needed on long routes. Toss in the way aircraft could be made lighter if they never had to be capable of containing as much fuel in the first place and very soon a virtual circle develops.
BUT this analysis does not allow for two things.
1 BEag’s safety issue
2 Market resistance to the investment needed (scrap existing types early, develop new versions, develop auto tanking) for a limited advantage.
Without wishing to flog a dead horse we have just about cracked the provision of types that will go half way round the world non stop. So what next? One answer has been for people to say a step change in fuel burn could be achieved using AAR.
JF