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Is 59.3 the ideal CG before descent?


Ray Proudfoot

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Fuel can get tight in tanks 1-4 in the last 100nm before the decel / descent starts. The CG range is very tight at high altitudes so the further aft you can get the CG the more fuel you can move forward whilst staying in the limits.

Given CG further back than 59.3 will trigger the audible warning I find if I can get CG to that value it helps me move more fuel forward than if I aim for 59.0.

But I’m not a Concorde pilot so I was wondering if this was the preferred procedure used in r/w flights.

One other question. Fuel often has to be pumped into tank 9 for correct CG when landing. Is this pumped first before tanks 5 and 7 or later in the descent?

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Robert J Toten

Sounds like you're either too tight on gas or having issues managing it. It shouldn't be possible to move the CG further aft than 59.0 after you finish the transfer to Tank 11. Nearing TOD only Trim 11 and Collectors 1-4 will have fuel. From where will you get the extra fuel for 11?
5 and 7 should be long empty. If you have fuel in 6 and 8 you will use it to fill the collectors, just move fuel directly from 9 to 11. If you use the auto transfer then extra from 11 will automatically transfer to 5 and 7.

It's been a while but that's my recollection and understanding. Usually my fuel situation forces my CG forward even before TOD, which will force an early descent if you don't have enough fuel to properly control CG.

Sent from my SM-G950U using Tapatalk

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Fuel is determined by CPS-X so amounts will be accurate. Using manual control it's easy to get the CG further back than 59.0. You can either pump fuel from 1 and 4 to 2 and 3 or switch off the pumps for 1 and 4 when 5 and 7 or 6 and 8 are feeding the four collector tanks.

I don't pump any fuel into 11 other than the amount determined by CPS-X for 59% CG - normally 10,500Kg. I vary the CG only by adjusting the amounts in 1-4.

If you're having to pump fuel from 11 to keep 1-4 above 1Tn it sounds like you haven't loaded enough. What program do you use for fuel calculation?

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Ray, we have discussed this several times but I shall briefly summarise again:

- when CG gets back to 59.2 return the "AFT CG" switch to normal (or when fuel remaining in T6/8 is just greater than the amount required to return all T1-4 to full level)

- when T6/8 are empty all fuel should be in T1-4 and T11, but you must then manually move fuel from T11 into T5/7 until the CG nears the forward limit in order that the wing structure is cooled. When T5/7 are above 100kgs turn on their pumps to pump the fuel into T1-4, giving you more to burn

- when all the above is done, and any one or combination of T1-4 reach 1000kgs, you MUST commence your deceleration and decent as per normal operating procedure

This is the only way it was done, every flight. There is no way to extend range or anything like that which is why fuel checks were crucial and if there was any doubt a diversion carried out long before it got to this stage.

I think your logic of having an aft CG to give you more to move forward won't help you because as I've pointed out before, if the zero fuel CG is further forward it gives best range because more fuel can be carried aft. 

Fuel would only have gone directly into 2/3 if valves or pumps failed or the SEO had made a mess of something because it was needed to cool the structure in this set pattern. 

If you are finding you aren't having good reserves at the end of flights then either you are pushing the limits to begin with or you aren't getting best economy somewhere in your flying which I can't diagnose easily without seeing how you fly the departure/climb etc. Or of course the weather was different in real life to when being planned. 

Does this help?

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Hi Frazz,

Does it help? Yes indeed it does. I am following the procedures you mentioned right up to the point where tanks 6 and 8 are below the threshold when the AFT CG switch is moved to FWD.

What I’m not sure of is the point at which fuel in 11 is moved forward to 5 and 7. I’m delaying it as long as possible until 1-4 are nearing the 1T threshold. Should it be moved earlier?

I shall cease moving fuel around in 1-4 except for balancing purposes.

What is the max capacity of tank 11 in the r/w? Greater than 10.5T? I ask because that’s the limit in P3D. It can be pushed to 11T by opening valves but I don’t do that.

I had around 8-9T remaining today after a flight from Tokyo to Singapore so any deviations from correct procedures aren’t having too much impact.

I engage the a/p once the reheats are cancelled and throttles are retarded by the VFE and 250kts is achieved. I then engage Pitch Mode and gradually increase throttles manually as I climb. After 10,000ft I engage full climb power and engage Max Clb.

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I think I said in my post above when to move the fuel forward... When tanks 6 and 8 are empty and you turn the pumps off you move fuel forward from 11 into 5/7 to cool the wings which now have no fuel in them.  After at least 100kgs is in 5/7 you can pump from 5/7 into the collectors again to give you more fuel to burn. 

Remember that 1000kgs in the collector tanks is the minimum for fuel pressure considerations to avoid pump cavitation etc so you should be slowing and descending by the time the levels reach this point. 

Lateral balance of fuel should be done from tanks 5-8 through the collectors, it should be well in balance with fuel only in 1-4 and 11.

The maximum fuel in tank 11 question I definitely answered before in another thread and talked about how it varies with density etc, I suggest you find that thread and the huge thread where the whole fuel system was discussed in detail a while back as I don't have my manuals to hand at the moment. 

I also shared my fuel system help document which would help you with this stuff if you download it from the downloads section. 

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Robert J Toten

Ray,

I want to apologize for my post earlier, I has misunderstood what you were trying to do, and what issue you were having. I mistakenly believed that you were having problems with exceeding the maximum forward CG and wanted to start aft of 59%. From rereading it, it appears your concern is exceeding the aft limit, and want to start at 54.3% at TOD.

I have CPS-X installed but have yet to use it for a Concorde flight (confession, it's been approx 6 months since I've flown the Concorde but always manually manage fuel). My fuel loading comes from the stock FSL menu. I never get the collectors below 1,000kg and am surprised that you have issues moving the CG with such light fuel loads as at TOD. Of course Frasier is the resident expert here, but I always find that I transfer fuel too quickly and reach the forward bug if I get distracted with the 3 pilot jobs during descent.

My personal technique is to target 55% once I start descent, and then transition to 53.5% for landing. These targets help me manage the CG more easily. Usually this coincides with my withdrawal of fuel from 11 to keep the Collectors at safe levels.

Thanks Frasier for further explaining the wing cooling requirements.

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Hi Robert,

No offence taken. :D My logic in keeping the CG as far aft as possible (59.3%) was to allow me to transfer far more fuel forwards when the collectors were close to 1K. But Frazz has explained the correct way to move fuel so I'm going to try that on the route I'm currently flying - WSSS-RJAA.

If you only fly the routes supplied in the FSL package (JFK, TBPB etc.) then you are missing out on what CPS-X can give you. How could you know how much fuel to load for KJFK-KMCO for instance which is one of my favourite routes down the east coast. I suspect you are loading the maximum amount of fuel which means you don't have the problem of 1-4 dropping below 1K.  Have you flown EGLL-TBPB which is really at Concorde's limit?

I agree that 55% is okay for the descent but CG needs to be around 52% for landing. You could be tail-heavy with 53.5%.

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Contrary to the tutorial I find I can't leave the tanks 1/4 switch in the AFT position until tanks 6/8 have less than 4000Kg of fuel. If left on AFT the CG will go beyond 59.3 triggering the warning. Switch to NORM and it soon goes below 59. So it needs to be constantly monitored and adjusted as required.

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Frazz,

Couple of screenshots attached showing state of fuel when 6 and 8 are empty and shortly after when fuel in 11 has been pumped into 5 and 7.

I note you said fuel was kept in 5 and 7 to cool the wings but what little fuel was moved into those tanks was quickly removed by feeding 1-4. Have I understood you correctly?

I now have a CG of 58.3% and a little more fuel in 1-4 than had I not performed that operation. Still 800nm to go. Hopefully enough fuel because I can't move any more from 11 otherwise CG will go out of limits.

You may have noticed a disparity in tanks 1 and 4. Not of my doing. Must be a bug.

 

Fuel_Tanks 6 8 Empty.png

Fuel into 5 and 7.png

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This was the state of fuel around 30nm before decel. I had to pump a small amount from 2 and 3 into 1 and 4 to prevent dropping below 1K. CG went forward 2 notches to 58.1.

Landed with 12T so plenty left. Very tight though before the decel point. Out of interest I used PFPX to calculate fuel and it came up with 81T, 2T less than CPS-X but I did choose extra taxi fuel so the two seem very accurate.

Tanks 1 and 4 Critical.png

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2 hours ago, Ray Proudfoot said:

Contrary to the tutorial I find I can't leave the tanks 1/4 switch in the AFT position until tanks 6/8 have less than 4000Kg of fuel. If left on AFT the CG will go beyond 59.3 triggering the warning. Switch to NORM and it soon goes below 59. So it needs to be constantly monitored and adjusted as required.

Ray, you didn't read my instruction correctly, I said in my post above to move the switch to normal when CG gets back to 59.2% OR when tanks 6/8 reach the level required to fill T1/4 to normal level. 

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Ray,

i suspect the difference in T1/4 is because you didn't switch the AFT CG switch back to normal early enough so they weren't fully topped up. 

Yes you can transfer fuel from 5/7 as soon as the contents are above 100kgs as it will still cool the structure while moving in and out, plus it is also about cooling the pumps that have sat heating for an hour or so. 

There should be no need to pump from 2/3 to top up 1/4 if you follow my instructions as above and (for the last flipping time..:P) the procedure is you have to start your decel if ANY of the four collector tanks reach 1000kg, you are not meant to start moving fuel arbitrarily to extend your cruise.......!!

What was the fuel load you used for departure?  Could you have taken extra? Was there head winds or high temperatures? 

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28 minutes ago, Fraser Gale said:

Ray, you didn't read my instruction correctly, I said in my post above to move the switch to normal when CG gets back to 59.2% OR when tanks 6/8 reach the level required to fill T1/4 to normal level. 

I read it correctly Frazz. At 59.3 I switched it to normal but as I said in my earlier post it continued to move forward to 58.8 so I turned it back to AFT to keep CG at 59.

And please expand on what “level required” is for 6/8. The manual advises to switch to normal when 6/8 drops below 4000Kg. Are you saying that is not the correct instruction?

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40 minutes ago, Fraser Gale said:

Ray,

i suspect the difference in T1/4 is because you didn't switch the AFT CG switch back to normal early enough so they weren't fully topped up. 

Yes you can transfer fuel from 5/7 as soon as the contents are above 100kgs as it will still cool the structure while moving in and out, plus it is also about cooling the pumps that have sat heating for an hour or so. 

There should be no need to pump from 2/3 to top up 1/4 if you follow my instructions as above and (for the last flipping time..:P) the procedure is you have to start your decel if ANY of the four collector tanks reach 1000kg, you are not meant to start moving fuel arbitrarily to extend your cruise.......!!

What was the fuel load you used for departure?  Could you have taken extra? Was there head winds or high temperatures? 

I don’t know when I need to switch AFT CG back to normal. The manual only gives advice to keep it forward of 59.3 and aft of the forward bug. What is the fully topped up amount for 1 and 4? Hard to stick to rules when I don’t know what they are. ;)

I know I shouldn’t have moved fuel from 2 and 3 but if the system allows me to why is it not allowed? It makes no sense to this amateur pilot. Nothing in the manual saying thou shalt not do it.

Even if I did start the decel early, fuel would continue to be used from 1 and 4 until enough altitude had been lost. Is that early descent procedure the same as a standard decel / descent? I landed with 1T less than that calculated by CPS-X.

Fuel was 82.9T. I did load an extra 500Kg for the long taxi. I wouldn’t know if extra enroute fuel was required. Don’t have sufficient knowledge. I took 87 pax for a 3042nm flight. Average ISA DEV was -16.5C. Departed 09:45 local with air temp 31C.

I thought I did alright on this flight. A little encouragement would be nice. ;)

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I am sorry if I don't sound encouraging it is just that I have typed most of this stuff at least twice before in other threads...

I will try to make this more simple: if you look at your first screen shot above when T2/3 are full you will see they are around 4500kg so T1/4 should be about the same when full. The aft CG system runs T1/4 down to around 2500kg (might be 2000kg).  That means that you need AT LEAST 2000kg to return them back to normal level when you turn the aft CG switch to normal.  If you do this late then you will have problems with levels later on.  In point of fact, rarely will this be an issue because the burning of the fuel from the wing tanks moves the CG gradually aft, so when the CG gets to 59.2 you will have to return the aft CG switch to normal and as you have discovered it will move the CG forward of 59% BUT it will still be moving gradually aft because you are still burning fuel effectively from T6/8 which is why I don't understand why you would have put the switch back to aft as this would eventually cause you to reach the aft CG boundary. 

When tanks 6/8 are empty your CG will be back to 59 if everything is in the right place at which time you move fuel into 5/7 from 11 and set the pumps on in 5/7 as previously described until near the forward CG boundary.  When any tank nears 1000kgs, start your decel. 

If you don't have enough range by doing the above you are not taking enough fuel, regardless of CPS or PFPX.  They are giving you what is called "flight plan fuel" which is the minimum required with legal reserves and about 2500kgs extra. No Concorde pilot that I have spoken to would take that amount of fuel only unless it required full tanks and there was no option and even then they might do a fuel stop.  If you take the maximum fuel as dictated by ZFW, PLTOW or max takeoff weight then it is know as taking "loadsheet fuel".  If the flight plan says to take 82.9T I would probably take 84 or 86 Tonnes depending on weather, and if I could do so without exceeding legal weight restrictions. 

As for your "why is it not allowed" question, I didn't say it wasn't, it just shouldn't be required if you follow all the procedures correctly before hand, but it certainly shouldn't be used to cover insufficient fuel to continue cruise.  I believe I shared the chart that shows minimum fuel for continued supercruise some time ago? 

You asked how it would be done for real and that is what I'm telling you...

Earlier on in the thread you asked about fuel in tank 9 for landing - it would be manually moved there during the approach checks to bring the CG to between 53.5 and 52.5% and there is a chart that gives the appropriate figure. 

I advised you to get the deals manuals on CD a while ago, then you would have all the charts and procedures.

 

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Frazz,

Thanks (again!) for posting this kind of advice on handling fuel manually. I’m going to copy and paste into a document for future reference. But really this kind of info needs to be in a proper document, not buried in a forum where searching for it is time consuming by everyone.

Please, please consider putting it into a document and uploading it here. Consider it an addendum to the tutorial which, although excellent, doesn’t go into this kind of detail as it assumes fuel is handled by the VFE.

I’m moving that 1/4 switch rearward simply to keep the CG no further forward than 59 but crucially I haven’t known until today the full rules regarding that operation.

Of course I’m not going to know I don’t have enough fuel until I’m near the end of the flight. Conditions vary according to where in the world you fly so there are no hard and fast rules. But what I might do is add an extra 2T for flights under 1500nm and 3T over that. That should negate  my tendency to move fuel around the collector tanks.

Thanks for the tip about when to move the fuel into 9 for landing. I know you recommended that CD but I feel I’m okay on most aspects of flying Concorde and only need help with the fuel mgmt in the latter stages of the flight.

So please consider writing a document on how to handle the fuel once 6/8 are empty. That seems the most important part of the flight.

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If I do anything it will be a computer based training module rather than a document.  There was no documents with this amount of detail for the crews other than a part in the flight manual which is why I think the CD would be a good investment for you and you would also have the cruise manual with flight planning figures, fuel burn figures and the performance manual for landing and takeoff figures, all of which would not only help you fly the off-the-beaten-track sectors you like to do, but would also help your understanding of the aircraft.  

I don't doubt that you can confidently fly her but in order to do things "real world" style you really have to have an in depth understanding and the fuel system is one of the most important aspects as well as being relatively less technical to get your head round, mainly because you can see what it is doing.  Some of the other systems like the hydraulics and intakes you can't really "see" what is going on but you still have to know what is going on if you get what I mean.

Please also remember that I have a rather involved day job and that writing a document takes a lot of time, and while I enjoy sharing information with people and helping them, it's not like I'm on a Concorde Flight Manager salary and paid to do so....  I think if this were 17 years ago or whenever I started flying Concorde in the sim I might have been able to justify writing a document for the fuel system primarily for my self but the fact is I know the stuff now because I've read all the manuals cover to cover countless times, and I am not a real authority on the stuff anyway, that should be left to people who went through the BAC conversion course.  Mind you they are all getting on a bit now and another highly respected former captain and manager passed away last week. 

 

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Frazz,

I appreciate you have a day job and time is valuable but I don't know anyone outside the FSL team that know the fuel system better than you. And Andrew et al have all the coding to do so I wouldn't expect them to write this up.

I could buy the CD but then that would only benefit me. If you put together something suitable in whatever format you feel is most helpful then all Concorde-X pilots could learn from it. As I said earlier it doesn't have to be the whole sequence from start-up because that is covered pretty well in the tutorial.

It's the final part of a flight when fuel has to be managed in a certain way that makes all the difference between a successful flight and one that isn't.

I won't labour the point. I just hope you can find the time to create something that will benefit a lot of people who are keen on flying this wonderful aircraft to the best of their ability.

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The thing is Ray, you are the only person who has requested such a document and you might be the only one who really wants such a thing.  Others are probably happy working things out for themselves or more likely have the real manuals and work from them. 

I will see what time I have but I'm not promising and I don't know when.

Please remember you are requesting a lot of work to be done for free (and no I'm not wanting money) when it has all been covered somewhere on here already - would you have done this in your line of work...?

I'll see what I can do.

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Robert J Toten
9 hours ago, Ray Proudfoot said:

Consider it an addendum to the tutorial which, although excellent, doesn’t go into this kind of detail as it assumes fuel is handled by the VFE.

Ray,

Looking at Pg. 7-101 of the manual I see:

Quote

When the wing tanks 6 or 8 contain 4000 kg or less, return AFT TRIM switch to NORM.

I feel the tutorial goes into great detail about manual fuel management. I have never used the VFE in the FSL Concorde, and feel the tutorial gave me plenty of knowledge to handle it successfully. Combined with the fantastic "mastering the Concorde fuel system" YouTube tutorial I feel that I have a strong grasp of the process after 3-4 flights with no VFE. In the particular example you have posted, it appears your low fuel state caused you to loose control over the C.G. and necessitated an early deceleration/descent to adjust the Center of Pressure as required. Depending on where you were this would have resulted in a diversion, as my first attemmpt at the EGLL-KJFK tutorial flight left me landing in KBOS.

In my opinion, you were doing great until you reached the state "about 800nm to go." My judgement, looking at your panel, is that you were just about to loose control of the C.G., and should prepare to descend/decelerate in the very near future. You didn't have 800nm, and had to get creative to stretch the cruise as Frasier suggested.

9 hours ago, Ray Proudfoot said:

Of course I’m not going to know I don’t have enough fuel until I’m near the end of the flight.

Since I have some real aircraft time, I often keep my E-6B sitting by my desk, and find it very helpful when flying certain aircraft in the simulator. If you run the calculations against the remainder of your flight plan you should have a basic idea if you will make your destination by at least halfway through the flight, and a very good estimation for the diversion decision with at least 1/3 of the way to go. I knew I wouldn't make KJFK probably while still east of Canadian airspace.

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Robert,

thanks for your input although what I would say is that the statement about returning the AFT CG switch to normal when 6/8 reach 4000kgs or less is misleading because sometimes the CG would have reached the aft limits by that time depending on load and balance. As Ray knows I have never used the tutorial included with Concorde X but we have discovered a couple of differences shall we say between it and real world ops, like the decel tables having the wrong distance figures for example. 

I'm sure it was written in good faith with the information being as accurate as possible and in fact I have found errors in the real manuals at times as well between different editions etc although they are few and rarely significant operationally.

Ray,

I'm not sure if CPS has this but what you really need is a fuel "how goes it" sheet that the crews had in real life, which had fuel to destination figures for several waypoints along the route. The crew would subtract the fuel to destination from the fuel on board and get a good idea of how much they would have at destination.  If it got below normal reserves (6500kgs + enough to hold or divert somewhere) they would divert to somewhere closer.  This was supplemented at a selected waypoint that the crew would mark on the log as "fuel check" (probably the last one from which a suitable diversion could be made if the results weren't good) where a table in the cruise control manual would be used (latterly I think they had a program on the HP200LX computers they carried, as I now do) to look up distance to go, wind component and current weight against fuel to destination.  I have found these tables to be very accurate. 

Flight plans from PFPX do have this in them although I find their format less clear than the Concorde crew version from real world and I'm not sure how accurate they are with my profile, I would have to do some testing.

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Robert,

I hadn’t lost control of CG at any point in the flight. Unlike other flights I had moved fuel from 11 to 5 and 7 as Frazz suggested and it was that action that caused the  CG to move forward. There was still plenty of fuel in 1-4. 16T in fact. It was only because there was less in 1 and 4 compared to 2 and 3 I needed to get more fuel into those tanks. But of course I couldn’t because that would push CG too far forward.

The fuel in 1 and 4 dropped to 1K around 30nm before my planned decel so had I added another 1T at the outset the situation would have been fine.

The tutorial doesn’t cover the detail mentioned by Frazz about what fuel levels should present in 1 and 4 after 6 and 8 are empty and this needs expanding which is why Frazz’s post was helpful.

I’ve never had fuel problems on the LHR-JFK run. The flight to Barbados is very tricky though. How do you get on with that one?

I’ll revisit that YT video on fuel management as I’d forgotten about it, thanks.

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11 hours ago, Fraser Gale said:

The thing is Ray, you are the only person who has requested such a document and you might be the only one who really wants such a thing.  Others are probably happy working things out for themselves or more likely have the real manuals and work from them. 

I will see what time I have but I'm not promising and I don't know when.

Please remember you are requesting a lot of work to be done for free (and no I'm not wanting money) when it has all been covered somewhere on here already - would you have done this in your line of work...?

I'll see what I can do.

There could be many others wanting to improve their management of the fuel but don’t pipe up. But I take your point that it’s not a 5 minute job to put something together so will leave it to you.

As I said earlier I don’t think you need to start from scratch as the tutorial covers most of the flight. It’s just the final stage after 6 and 8 are below 4000Kg that needs expanding given what you posted yesterday is not something I’ve seen in any FSL document.

Regarding your point about checking fuel consumption against a planned calculation then yes, that is available in PFPX but not CPS-X. I’m able to read that okay too.

Given how close the fuel calculation was in yesterday’s flight using your data in PFPX I can certainly use that as a guide. 

Edited by Ray Proudfoot
Additional info
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If you are going to use the PFPX flight plan then may I suggest that you be sure to add any extra fuel you intend to carry in PFPX so it is accurate and that you do at least two fuel checks down route, one in the first half of the flight and one in the second half - where they are will depend on when you are in range of diversion airfields. If at either of these checks you subtract the fuel to destination from the fuel on board and get an answer that is less that 9,000kg (6,500kgs final reserve plus 2500kgs contingency fuel) then you should divert for fuel.  Normally you should expect the fuel remaining at destination to equal 9,000kgs plus fuel for diversion to alternate or holding especially if the weather is marginal but it looks like you tend not to carry alternate fuel so you can ignore that.  

Just to add to this - even though at a fuel check you look to have enough fuel to land at destination with normal reserves, it doesn't mean you will get to your planned decel point before the collector tanks get down to 1,000kgs.  Even though she is most efficient at Mach 2 you must still slow down if this happens but safe in the knowledge that you will reach your destination as the descent is taken into account in the fuel figures - if PFPX does it properly that is.

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Thanks for that advice Frazz. Having flown a couple of long trips over the weekend I need a short break before my next one. I did take time to watch the excellent video on YT last night and paid particular attention to what should be done when 6/8 drop below 4T. The significance of the Norm / Aft switch in relation to fuel amounts in 1 / 4 is something I had not previously considered critical.

CPS-X looks to be pretty accurate in regard to fuel consumption. In my two recent flights I was only 1-2T out on the estimated fuel usage. Comparing fuel burn to PFPX estimates should be interesting.

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I'm sure for calculating trip fuel CPS is indeed accurate but it doesn't sound like it helps you once you are in the air where conditions can be very different. No matter how accurate either of them are, you want to add on a little extra fuel if you keep getting to low fuel levels before the end of cruise. 

 

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Don't the flight planners already take possible changes in conditions in form of trip reserves into account?  If so, why would you take a ton extra?  More so as on your recent flight from Singapore to Tokyo, there would be plenty of diversion opportunities (Vietnam, Taiwan, etc.) if anything happened, unlike with the EGLL - TBPB route.

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They should take it into account but Ray always seems to get low on fuel before reaching his planned decel point.  I don't know how the planners could factor this in whereas in real life the fuel was calculated on a percentage supersonic/subsonic basis which is quite complicated as the percentages varied depending where on the route you were. I'm not sure I fully understand it and anyway there is not much point in explaining it as our planners don't do this as far as I know. 

The main routes, alternates and routes to alternates all had a standard fuel figure in the navigation manual which was used as the basis to plan a flight.  Any out if the ordinary routes would be planned months in advance by specialist flight planners and performance engineers. Sadly we don't have the staff for that...!

There are planning pages in the cruise control manual that flight crews could use to plan a flight from scratch if they found themselves on the other side of the world without help, and this happened on more than one occasion.  It is those figures that I used for the PFPX profile but I'm sure the crews would have used their "airmanship" to add some extra fuel if the thought they needed it and they had the weight in hand to do so. 

Ray is arriving at destination with the correct fuel so the planners are working, it's just the end of cruise that is slightly off.

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7 hours ago, Konstantin said:

Don't the flight planners already take possible changes in conditions in form of trip reserves into account?  If so, why would you take a ton extra?  More so as on your recent flight from Singapore to Tokyo, there would be plenty of diversion opportunities (Vietnam, Taiwan, etc.) if anything happened, unlike with the EGLL - TBPB route.

I refer you to Frazz's reply who's a lot more knowledgeable than me. I agree with his last sentence - arrival fuel is fine, just how I manage tanks 1/4 when 6/8 are empty.

It would be useful to know what the fuel amounts in 1-4 should be at the decel point. Should all 4 tanks have the same amount and obviously all above 1T or something else? I suppose what I'm asking is is there an ideal tank load we should have at that point. If there is then I can compare my actuals to that and see how close I am.

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There is no real answer to that Ray, other than all should be relatively even and above 1000kgs.

On a New York run I usually land with between 12,000kgs and 16,000kgs depending on weather/holding etc and (off the top of my head) the collectors would have only run down to between 2,000kgs and 2,500kgs again depending on how much I had in the first place and weather. 

On a Barbados however, I would want to land with between 9,000kgs and 11,000kgs (although anything over 6,500kgs is a good day!) and before the decel I would be down to just above the 1,000kgs in the collector tanks. I think I have on around 3 occasions had to start the decel slightly early (only about 50nms or so) because I've reached 1,000kgs in the collectors but still made it to BGI with room to spare. This has never happened to me on any other route that I can think of but you we be favourite for company promotion as you would be known as a "minimum fuel" man whereas I tend to carry at least 1T extra.

 

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Thanks Frazz. I do find when I've used my own fuel manipulation techniques tanks 1-4 contain equal amounts of fuel. I can't recall what stage of the flight but it was during the descent.

I'll practice your recommended procedure on a relatively short flight - EGCC-LPPT and then on longer ones. I have yet to complete a flight to TBPB without fuel dropping below the 1T limit so maybe I should install scenery for Shannon and stop there for a refuel!

Extra fuel requires extra fuel! :)

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Barbados really is a point of no return flight in that after a certain point you are committed regardless.  Before Ian Kirby SEO wrote a computer program and developed graphs/charts that showed accurately the amount of fuel you would arrive with, the BGI did indeed stop in Shannon to refuel.  These were also critical in the case of engine failure. 

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@Ray Proudfoot  I have been thinking a lot about your end of cruise issue and I have come to the conclusion that I am going to have to give you the full, more complicated procedure which until now I haven't, purely because most people won't need it in the simulator and in fact I often don't use it because it increases workload.

Assuming you are in the cruise and have finished the main transfer (T9/10 empty) with CG between 58% and 59% then:

- transfer as soon as possible the fuel from 5A and 7A into 5 and 7 and set the AFT TRIM switch to AFT

- when T5A/7A low pressure lights have been on for 20 seconds, set the pumps to OFF and shut the transfer valves

- monitor CG and if it travels aft of 59% apply the conditional procedure "CG AFT OF 59%" (see next line)

"CG AFT of 59%": open inlet valves to T5/7 and set pumps in T11 to on, moving fuel forward until CG is at 59%

The next bit here is the new bit...

- when T6/8 reach a level equal to the difference in level between 2&3 and 1&4 (round about 2200kgs) set the right hand pump in T6 to off and the left hand pump in T8 to off, stopping transfer into T2/3

This will allow CG to be kept aft for as long as possible

- when T6/8 low pressure lights come on set pumps to off

- when any collector tank falls to 1000kgs, open inlet valves to T5/7 and pump forward from T11 selecting the pumps in T5/7 on when contents above 100kgs

- when CG reaches 57.5% set T11 pumps to auto and close the inlets to T5/7

Cruise can continue until any collector tank falls to 1000kgs at which point you must slow down and go down.

- just before deceleration set the AFT CG switch to Normal, allowing them to be replenished by fuel from T11 via T5/7 when you move the CG forward

At the decel: if CG forward of 57.5% and speed greater than M1.5 wait until M1.5 before selecting forward transfer else as normal

Please note Ray that this wasn't always required and I do believe on the ITVV program the SEO had taken the AFT TRIM off quite a bit before descent probably because he had an aft ZFCG and he knew they didn't need to eek out every bit of supersonic range.  There are other procedures for light flights and short sectors as well.

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Frazz, fantastic post, many thanks. I’m going to have to copy and paste into a document and print it.

Might get a flight in tomorrow to test the instructions but the golf may just interfere. I wish we could download your brain to an SSD! :D

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I think it would be good if we could download anyone's brain to an SSD as memory starts to fade..

Don't feel guilty if you can't be bothered doing all this on every flight because unless they find a way to simulate a virtual pilot allow us to be the SEO it is nearly impossible to do the job of all three crew and not forget to do something! Especially if you are as mad as I am and fill in all the paper work too...! 

Mind you, I still think you should take more fuel :D

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Frazz, your brain is doing just fine. :)

This doesn't sound like a huge amount to learn. When I think back to my decision to learn the fuel management the number of switches and tanks was a bit scary. But now I know it like the back of my hand. There's a reasonable amount of free time when in cruise/climb mode. I have to remember to load the next INS segment of course but fuel management probably takes more of my time than looking at the instruments.

I use Electronic Flight Bag by Aivlasoft which logs tour flight and fuel usage for each waypoint. Much easier than paper work! ;)

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Yeah but I'm not convinced this full procedure was used on every flight even though it's in the manuals.  Incidentally the book says not to use AFT TRIM on short sectors because you have to allow it to complete a full cycle, once selected it must remain selected until the fuel has been reduced to 2000kgs you can't stop it part way.

I only use EFB stuff when flying the Airbus aircraft, I fly Concorde the old way with aerodrome booklets, communications logs, fuel how goes it charts, fuel flight plan charts, takeoff performance sheets, descent and landing data sheets and I even run a technical log!  

The cruise can be quite busy when done like this. After entering new waypoints you must check the distance for each one matches the comm log, after each 10 degrees of logitude you must do a waypoint check to make sure you are where you think you are, at certain waypoints you have to call in a position report on the HF (no ACARS here!) and do fuel checks as discussed before.  On top of all this is working the fuel etc.  The flight goes extremely quickly....

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Sorry Frazz, not ignoring you. Had a busy day with all this nice weather. I’m going to fly EGLL-GCTS tomorrow. That’s 5 hrs in subsonic aircraft and around 2 in Concorde.

Fuel will be around 55T so once it’s loaded I’ll see how it fits in with your recommended procedure bearing in mind shorter flights may not match the ideal fuel handling procedure.

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6 minutes ago, Fraser Gale said:

Does your 55T include diversion fuel? Bearing in mind it's an island and you might have to divert to the mainland if something changes, you would want around 8T for diversion. 

Yes, CPS-X insists you choose an alternate. I've selected GCLP - Las Palmas around 100nm or so away.

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  • Ray Proudfoot changed the title to Is 59.3 the ideal CG before descent?
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