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Subsonic Flights - Is 55% CG always the rule?


Ray Proudfoot

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It is certainly possible to adjust the fuel burns for different registrations, but doing so would require detailed information about the factors that contributed to the variation in fuel burn. For instance, you stated that G-BOAF was the lightest Concorde, so this aspect could be accommodated quite easily by entering a lower empty weight in the respective aircraft.cfg (and making no other changes). As far as the other Concordes, how does one know whether a higher or lower fuel consumption is due to aerodynamics or engines?  Anything engine related can be easily tweaked by modifying the fuel flow scalar or the thrust specific fuel consumption. That is, if the fuel burn was higher or lower at all stages (idle, taxi, T/O, cruise, etc.). If there was a difference in fuel burn during specific flight stages only (e.g. Mach 2 cruise), one would need to alter the parameter(s) that impact the fuel burn at this stage the most (e.g. editing the fuelburn.ini-table). If the variation in fuel burn is of aerodynamic nature, it would require tweaking the aircraft.cfg and Concorde.air-file and leaving any engine parameters alone. 

As I said, adopting the idea of having different registrations burn slightly different fuel amounts is generally possible, but without precise information about the details (e.g. from a real former Concorde pilot), it would only be a matter of guess, which I don't think would be completely satisfactory for some.

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Fraser Gale

The issue here is that even talking to a "real former Concorde pilot" which I could do, will not help because unless they have the weight certificate that was held on each airframe or have an exceeding good memory even they won't know exact details. I can try asking. 

Plus, I would suggest that even the manufacturers couldn't have answered some of what you are because after all, they were trying to make them all fly exactly the same and it was only through in-service experience that these things were discovered. All the manuals were the same for all the fleet but the flight planning computer that was held at Boedicea House asked for the specific aircraft that was flying the service because it used it's specific weight to aid planning the weights. They wouldn't vary by huge amounts but every little counts in a Concorde. 

Perhaps we could just have slight variances between each one to make it more interesting without it being exactly true to life, after all, the weights of the fleet all changed in 2001 which is when they were all re-weighed after the grounding. 

I might alter mine and have a play with it, if I can get the whole fleet to appear in my aircraft list....!

Frazz

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Fabrice Estienne

Ray + Frazz,

Ray, first, thanks for your INS files.

I do not use the concerned file to program the reheats, I was not aware about them.

I did not use reheats as regards this flight since I had stated in my previous post..

I planned to fly at FL340 / M.95, the target IAS is 338 kt.

Therefore I climb IAS HOLD 338 kt with full throttles to reach gently the cruise speed without judder. One teaches all IR pilot students this technique.

IAS 338 kt as you can see in CC_flyby_MEDOG is not the VMO, but the speed which matches the Mach 0.95 at FL340. Otherwise the VMO is 404 kt in this case according the GW of Concorde and the altitude.

My enhanced FSX / P3D is able to provide accurate VMO for a particular aircraft too.

Cheers,

Fabrice

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Ray Proudfoot

Hi Fabrice,

Interesting that you climbed at 338kt rather than 395 then adjusted the speed to match M0.95. But it does guarantee you won't go supersonic as I did briefly on my earlier attempts. :wacko:

Did you use real weather? I always fly with AS16 so as to get the correct air temps. I'll report back once I've flown with afterburner's modified files. I'm looking forward to seeing how much of a difference they make.

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Fraser Gale

Fabrice,

Whilst I respect that you may teach IR students to fly like that, none of them will be Concorde pilots in the near future and what you describe is normal for any other type of aircraft. Concorde however is vastly different and has to be handled in a very different way. The reason the conversion course was so long (6 months in total) was because "normal" pilots had to unlearn many things and learn to do them in a different way as well as the complexities of the aircraft systems. 

The correct procedure would be to hand fly with full power up to VMO (barbers pole) then engage the AFCS in MAX CLIMB until you get to Mach 0.95 when you would engage MACH HOLD on the AFCS with ALT ACQ set to capture your cruise altitude. The autothrottles should both be engaged in standby (no mode selected) at this stage so that they maintain M0.95 when the autopilot captures the altitude. This procedure saves time, fuel and a lot of money due to the high climb rate, passenger comfort came last in these priorities and besides, most people expected it to be more exciting on a light weight charter, that's what they'd paid for! 

Interestingly, one of the main reasons for the high failure rate on the conversion course in the early days (better selection procedures were introduced later on) was the lack of use and understanding of the automation. Many of the old RAF/Navy type pilots couldn't keep up and had a reluctance to fly her using full performance automatically.

Frazz

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Ray Proudfoot

I've just completed EGLL-EIDW using afterburner's modified air file and fuelburn.ini.

Here are the fuel remaining figures for various waypoints with yesterday's in brackets.Much improved, thanks @afterburner

EGLL 24531 (25158)

CPT 21326 (19116)

OKTAD 16681 (14730)

MEDOG 15545 (13733)

LANON 14518 (12658)

ABLIN 14055 (12314)

LAPMO 13438 (11022)

Fuel used 13425 (16493)

CPS-X estimated 14,800 after landing; I had 12,567.

I don't suppose any further improvements can be made to the air and ini files can they?

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Fabrice Estienne

Ray + Frazz

Ray, target speed 338 kt on IAS HOLD + ALT ACQ FL340 protect her she will not get into upper Mach. What's more I made this choice since 338 kt is a speed approaching the best min lift/drag ratio speed.

Frazz, I agree that you are absolutely right; the other solution is to climb VMO / M.95, MAX CLIMB segment at VMO to M.95 conjunction, then MACH HOLD segment to desired altitude. Nevertheless I prefer the first way personally because in this case I have not to monitor the M.95 conjunction where there's a risk go get into upper Mach (in desktop simulation I am alone). Now the FMS does the job, to give the A320 as example : Climb 250 kt / 300 kt /.78.

In the real world the two processes can be performed by the Concorde's crews.

Regards

Fabrice

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Ray Proudfoot

Fabrice,

You are climbing 57kts slower than the aircraft is capable of. If the Mach Hold worked on Concorde-X then it wouldn't be a problem climbing that fast. I accept the speed can get away from you very quickly but don't you enjoy the challenge of throttling back manually to maintain Mach 0.95? ;)

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Fabrice Estienne

Ray,

Just achieved the VMO / M.95, MAX CLIMB segment at VMO to M.95 conjunction, then MACH HOLD segment to FL340.

After I took the screen shot as regards VMO / M.95 I activated the MACH HOLD.

Maintain full throttles.

This AFCS function seems work properly but while reaching the desired altitude I had to tune the Mach manually from M.963 to M.951 with the IAS ACQ function of the Auto Throttles.

For the record the VMO computed in my simulation is the one of the real Concorde according her GW and the current altitude. The FSLabs simulation of Concorde ADC does not consider the GW of the aircraft and in your simulation you should obtain a VMO of 400 kt at FL285, then a VMO around 420 kt at FL340.

AT armed mode is of course incompatible with AFCS MACH / IAS HOLD: "both channels of the autothrottles will disengage".

Fabrice

CC_Conjunction_VMO_M.95_at_FL285.PNG

CC_Conjunction_338kt_M.95_at_FL340.PNG

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@Ray

I am glad to hear that you had a more accurate fuel burn on your last EGLL - EIDW flight with the modified files. I would not worry too much about the apparent discrepancy between the remaining fuel calculated by CPS-X and what you had left in your tanks after landing. I haven't used CPS-X, and I don't know what algorithm/formula it uses. However, I have calculated manually using available real-world figures that consuming 10 tons overall on the flight from EGLL to EIDW (which is what CPS-X has suggested) is only possible under ideal conditions, i.e. no wind, no noise abatement procedure, climb at maximum power, flying at the optimal altitude and no delays whatsoever. Factors like prolonged taxi time, taking off from runway 09 L/R, head wind and instructions by ATC to hold an altitude extend the flight time and the total fuel consumption. I would say that a total fuel consumption of 12 tons for the route shouldn't be too bad...

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Ray Proudfoot
44 minutes ago, Fabrice Estienne said:

Ray,

Just achieved the VMO / M.95, MAX CLIMB segment at VMO to M.95 conjunction, then MACH HOLD segment to FL340.

After I took the screen shot as regards VMO / M.95 I activated the MACH HOLD.

Maintain full throttles.

This AFCS function seems work properly but while reaching the desired altitude I had to tune the Mach manually from M.963 to M.951 with the IAS ACQ function of the Auto Throttles.

For the record the VMO computed in my simulation is the one of the real Concorde according her GW and the current altitude. The FSLabs simulation of Concorde ADC does not consider the GW of the aircraft and in your simulation you should obtain a VMO of 400 kt at FL285, then a VMO around 420 kt at FL340.

AT armed mode is of course incompatible with AFCS MACH / IAS HOLD: "both channels of the autothrottles will disengage".

Fabrice

Hi Fabrice,

I've just remembered that MACH HOLD is different to MACH ACQ. I guess when you select it it will hold the current Mach speed. Probably best left alone until you have levelled off at 340. I'll try it on my next test flight. I don't understand your comment about AT armed mode is incompatible with MACH / IAS HOLD. I can see AT1 engaged on your screenshot.

I appreciate you have a modified Concorde and not the same as the rest of us. Some things will obviously be different as you mention.

One final thing. Watch your CG. ;) That looks like 56% to me.

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Ray Proudfoot
35 minutes ago, afterburner said:

@Ray

I am glad to hear that you had a more accurate fuel burn on your last EGLL - EIDW flight with the modified files. I would not worry too much about the apparent discrepancy between the remaining fuel calculated by CPS-X and what you had left in your tanks after landing. I haven't used CPS-X, and I don't know what algorithm/formula it uses. However, I have calculated manually using available real-world figures that consuming 10 tons overall on the flight from EGLL to EIDW (which is what CPS-X has suggested) is only possible under ideal conditions, i.e. no wind, no noise abatement procedure, climb at maximum power, flying at the optimal altitude and no delays whatsoever. Factors like prolonged taxi time, taking off from runway 09 L/R, head wind and instructions by ATC to hold an altitude extend the flight time and the total fuel consumption. I would say that a total fuel consumption of 12 tons for the route shouldn't be too bad...

CPS-X uses accurate real-world Concorde data provided to Pierre by a former AF Concorde pilot. It also uses either NOAA or AS16 weather so that side will be accurate. Taxi fuel is estimated at 1000Kg but is user changeable. You can also load extra fuel should you feel the need. Give it a go. It's donation-ware and the new version is out next Friday. It's a really nice piece of software.

The files you provided have improved things no end. I might ask @Pierre Chassang if he thinks your files might be recommended over the default ones.

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Fraser Gale

Fabrice, 

the fact that your VMO may be different to mine really doesn't matter, we use what the instruments say just like any Concorde pilot would and in this case it's where the barbers pole is. 

If you are cruising with reference to Mach number just like all the subsonics do, you should be using Mach hold not IAS ACQ as this is to capture the IAS after which you would select IAS hold, all this should be done with both autothrottles engaged where they operate in a master and slave method. The autothrottles on the real aircraft were the best ever built because they didn't just try to hold a speed, they had inputs from longitudinal accelerometers and incidence so that they could predict power requirements through an acceleration term during any attitude change. 

I would suggest around 1000ft before top of climb you engage pitch hold on the AFCS followed by Mach hold on both autothrottles. You can then use the datum adjust to level off gradually without a change in speed - you might need to reselect ALT ACQ after pressing pitch hold. This would only be done in the last thousand feet of the climb though because up until then the AFCS has been using pitch adjustment to hold Mach 0.95

Frazz

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Fabrice Estienne
11 hours ago, Ray Proudfoot said:

Hi Fabrice,

I've just remembered that MACH HOLD is different to MACH ACQ. I guess when you select it it will hold the current Mach speed. Probably best left alone until you have levelled off at 340. I'll try it on my next test flight. I don't understand your comment about AT armed mode is incompatible with MACH / IAS HOLD. I can see AT1 engaged on your screenshot.

I appreciate you have a modified Concorde and not the same as the rest of us. Some things will obviously be different as you mention.

One final thing. Watch your CG. ;) That looks like 56% to me.

Hi Ray,

My screen shot 'CC_Conjunction_338kt_M.95_at_FL340" is after she levelled, this is why you see I selected AT1/ IAS ACQ mode to tune the speed, AT / MACH ACQ is not provided on Concorde. Then I should've selected either AT1 / IAS HOLD or AT1 / MACH HOLD. Another word,  AT / IAS HOLD mode is a sub routine of the AT / IAS ACQ mode.

I made this comment since the segment AP / MACH HOLD from the conjunction M.95 / FL285 to FL340 is a conventional 'Flight Level Change' segment which prevents the AT to be armed. The AP steers the aircraft on a selected speed (IAS or Mach) by changing the pitch, in other words the aircraft exchanges her potential energy between her kinetic energy at unchanging thrust, nevertheless the pilot may manually adjust the thrust if he observes the climb rate does not suit.

There's a difference between AP / MACH HOLD or AP / IAS HOLD modes and the AP / MAX CLIMB mode. The second follows the VMO which, in turn, varies according the GW and altitude, then ends with the AT / IAS HOLD when levelled. So to speak the AP / MAX CLIMB is a managed mode.Otherwise both AP / MACH HOLD and AP / IAS HOLD are not managed modes.

I do not hold a modified Concorde but my sim core is somewhat different since the real world speeds (included VMO) are provided to the add-ons.

Roger for the CG 56%, I fly her taking the VFE into service.

Cheers

Fabrice

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Ray Proudfoot

Hi Fabrice,

When you say "Flight Level Change segment which prevents the AT to be armed." do you mean in the real Concorde or this simulated one? We both agree that MACH HOLD in the simulated Concorde doesn't work. Maybe by design, maybe a bug? I'm guessing a bug because I can't see any logical reason why you would have a control that doesn't do what it should.

I've found that on very light loads MAX CLB is far too powerful and the climb rates can be excessive. Maybe fun for the pax but not for a simulator captain like me. ;) It's much more realistic on longer flights with more fuel.

Interesting discussion. Thanks for taking part. :)

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Fraser Gale

Ray,

MAX CLIMB is realistic and was used in the way I have stated but I can understand why you might get "behind" the aircraft if you are busy with other things.

The speed hold modes in general are not as accurate as they used to be on Concorde X, I don't know why but it is beginning to irritate me especially on descent when she won't hold 350kts accurately.

Frazz

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Ray Proudfoot
21 minutes ago, Fraser Gale said:

Ray,

MAX CLIMB is realistic and was used in the way I have stated but I can understand why you might get "behind" the aircraft if you are busy with other things.

The speed hold modes in general are not as accurate as they used to be on Concorde X, I don't know why but it is beginning to irritate me especially on descent when she won't hold 350kts accurately.

Frazz

The biggest problem is the fuel can't be pumped aft quick enough and I soon get a CG warning. The only way to overcome that is to either set a take-off CG > 52.5 (maybe 53.5?) or reduce the climb rate. I'm guessing the former is better.

I don't find it's too bad on descent but yes, it does vary a bit. A future bug fix may help.

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Fraser Gale

Take-off CGs of 52.5% are not authorised. You had three choices: 53% 53.5% or 54%.

If TOW less than 140000kg use 53%, if maximum fuel required with reasonably high load use 54% else use 53.5% this was not variable.

My advice would be to start pumping rearward slightly early, as soon as the rear bug starts to move. 

I did a short flight EGLL - EGCC the other day and with a take-off weight of around 114T had no trouble flying up to FL330 and achieving a CG of 55%.

Frazz

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Ray Proudfoot
3 minutes ago, Fraser Gale said:

Take-off CGs of 52.5% are not authorised. You had three choices: 53% 53.5% or 54%.

If TOW less than 140000kg use 53%, if maximum fuel required with reasonably high load use 54% else use 53.5% this was not variable.

My advice would be to start pumping rearward slightly early, as soon as the rear bug starts to move. 

I did a short flight EGLL - EGCC the other day and with a take-off weight of around 114T had no trouble flying up to FL330 and achieving a CG of 55%.

Frazz

Thanks Frazz. I'll bring this to the attention of @Pierre Chassang as CPS-X may need checking.

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Fraser Gale

It may be that AF did it differently (one of the reasons I have not used CPS) but if they did then I don't think they would have had much "flap effect" from the elevons as their trim must have been set to almost 0 to compensate for the forward moment. It also creates more room for error during calculations of takeoff performance which is why BA had three options and no more. 

Originally there were only two options, 53 and 53.5 but BA told the manufacturers they wanted more payload and hence Brian Trubshaw and (I think) John Cochrane tested to a more aft CG. They cleared 54% but on the understanding that this was THE LIMIT and no further aft CG on take-off was possible due to stability. 

Frazz

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Ray Proudfoot

Well Pierre is French as you probably guessed and he has access to a former AF Concorde pilot for info. :D

I have no idea what the AF Options are for CG but as he stores your preference for either AF or BA to produce the take-off and landing cards maybe he can work his magic with CG rules.

And bear in mind you can select your preferred CG in CPS-X. You just need to know the rules but being an expert that won't be a problem for you. Give it a try. It's out next Friday.

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Ray Proudfoot
3 minutes ago, Fraser Gale said:

Oh I know Pierre is more than capable of producing very accurate data from an AF perspective but even his AF pilot will only know how AF did it, if you see what I mean...

Frazz

Of course. :)

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Fabrice Estienne
22 hours ago, Ray Proudfoot said:

Hi Fabrice,

When you say "Flight Level Change segment which prevents the AT to be armed." do you mean in the real Concorde or this simulated one? We both agree that MACH HOLD in the simulated Concorde doesn't work. Maybe by design, maybe a bug? I'm guessing a bug because I can't see any logical reason why you would have a control that doesn't do what it should.

I've found that on very light loads MAX CLB is far too powerful and the climb rates can be excessive. Maybe fun for the pax but not for a simulator captain like me. ;) It's much more realistic on longer flights with more fuel.

Interesting discussion. Thanks for taking part. :)

Hi Ray,

The real Concorde and the Condorde-X prevent AT Armed (of course engaged) if the crew selects AP / IAS HOLD or AP/ MACH HOLD, that makes sense and it's in the nature of the sixties autoflight systems. This feature is a subset of the Concorde's AFCS. Now, the present auto flight systems are capable of synchronizing almost anything between the AP and the AT functions. Today Airbus holds the most complex set of managed modes ever made; sometimes their aircraft are not completely obvious for the crews and it is advisable to hold an electrical engineering education before the ATPL syllabus, in my humble opinion.

It seems that the AT / MACH HOLD of Concorde_X correctly works as long as she flies in subsonic (holds the existent Mach number), but in supersonic that's another story.

This is because of two reasons : (i) the sim core Mach Hold feature of FSX / P3D  does not work at Mach >=1; (ii) the Concorde AT / MACH HOLD function is specific when engaged in MAX CRUISE to prevent an overspeed situation developing, actually it is not a classical Mach Hold function but a very discerning feature.The difficult part of this business is to write a simulation code in a old-fashioned platform.

Concerning the relationship between AP and AT and the AT / MACH HOLD in MAX CRUISE, I suggested Lefteris + Andrew some AFCS enhancements to be compatible with the real Concorde (2017 January 6) :

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

"Hello Lefteris and Andrew,

Flying Concorde v1.39 I would like to suggest some features as regards the AFCS that the simulation does not currently permit while the real aircraft provides them unless I am mistaken.

1) The crew can adjust the pitch in MAX CLIMB state with the autopilot pitch datum adjust (airspeed +- 16 kt, 0.9 kt/s first pressure, 2.85 kt/s second pressure).

2) When the pilot selects another vertical mode (PITCH HOLD, ALT HOLD, VERT SPEED, ALT ACQ) in MAX CLIMB this drives the AT on IAS HOLD and when back to MAX CLIMB the AT returns armed.

3) In the MAX CLIMB + MAX CRUISE state the MACH HOLD shall lock itself on the CRS (Cruise Reference Speed which corresponds either to the CAS of Mach 2.00 if  MMO >= 2 or to the CAS of TMO)  + 5.4 kt and when the throttles are on the electric stop block + (CAS – CRS <= 2.7 kt) the MACH HOLD is canceled.

4) Just as a VS heel of 600 fpm is progressively added in 60 seconds on condition that the throttles leave the electric stop block. If the throttles go back to the stop block then the VS heel is in turn canceled after a while of 60 seconds.

Regards

Fabrice ESTIENNE"

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

Cheers,

Fabrice

 

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Fraser Gale

Fabrice,

with all due respect to your knowledge, we CANNOT compare modern Airbus aircraft to Concorde in any way. The systems were completely different, the training was different, the lift worked in a different way, the philosophy of operation was different, I could go on and on about the differences. 

Whilst what you have written to the developers of Concorde X is accurate, most people who use the addon would not be aware of these intricate details far less insist on them being modelled in a desktop simulation that is now several years old, yet mainly a very accurate representation of an aircraft that was the most complex ever built. I too have a list of "squawks" that I would like fixed but we have to accept that the developers have other things to do and we just have to hope at some point in the future they return to revise Concorde X. 

Now, can we please return to how to use what we've got rather than pointing out it's faults, after all, that's what airline crew do every day isn't it? 

Are you using both autothrottles yet? 

Frazz

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Fabrice Estienne
On 08/04/2017 at 0:54 AM, Fraser Gale said:

Fabrice, 

the fact that your VMO may be different to mine really doesn't matter, we use what the instruments say just like any Concorde pilot would and in this case it's where the barbers pole is. 

If you are cruising with reference to Mach number just like all the subsonics do, you should be using Mach hold not IAS ACQ as this is to capture the IAS after which you would select IAS hold, all this should be done with both autothrottles engaged where they operate in a master and slave method. The autothrottles on the real aircraft were the best ever built because they didn't just try to hold a speed, they had inputs from longitudinal accelerometers and incidence so that they could predict power requirements through an acceleration term during any attitude change. 

I would suggest around 1000ft before top of climb you engage pitch hold on the AFCS followed by Mach hold on both autothrottles. You can then use the datum adjust to level off gradually without a change in speed - you might need to reselect ALT ACQ after pressing pitch hold. This would only be done in the last thousand feet of the climb though because up until then the AFCS has been using pitch adjustment to hold Mach 0.95

Frazz

Hi Frazz,

I do not think myself that adding inputs from longitudinal acceleration and pitch attitude is distinctive as regards Concorde AT. It was long though that the design of AT should consider the longitudinal acceleration to prevent a needless action of the AT when the acceleration is <= 1 kt (TAS) /s. In other word one makes neither thrust correction nor AP pitch correction if the aircraft is + 40 ft and her speed reduction under 1 kt, vice versa if her is - 40 ft and her speed increase above 1 kt. This as regards subsonic. Now in supersonic condition (Mach 2) the altitude gap is around 100 ft for 1 kt/s. Finally one allows the AT and the AP to exchange themselves their energies, potential for the AP and kinematic for the AT.

Let's say rather the demonstration is easy to do, but I won't say it is nothing easier; write the thrust equation and identify the derivative to result  delta h = (TAS / g) x  longitudinal acceleration.

Somewhere else, as you noticed, I observed she won't hold 380 kt (I use this speed) accurately on descent. I am guessing that the problem comes from the FSX / P3D sim core which is not able to provide a genuine CAS especially at Mach > 1. The lift  and drag result from the internal sim variables (mainly CAS, Mach, temperature, altitude, and of course GW) while Concorde-X hold its own derivation of CAS which is captured by its featured AP. This leads one to assume the issue.

I will perform the flight and hark back over.

Cheers

Fabrice

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Fabrice Estienne
1 hour ago, Fraser Gale said:

Fabrice,

with all due respect to your knowledge, we CANNOT compare modern Airbus aircraft to Concorde in any way. The systems were completely different, the training was different, the lift worked in a different way, the philosophy of operation was different, I could go on and on about the differences. 

Whilst what you have written to the developers of Concorde X is accurate, most people who use the addon would not be aware of these intricate details far less insist on them being modelled in a desktop simulation that is now several years old, yet mainly a very accurate representation of an aircraft that was the most complex ever built. I too have a list of "squawks" that I would like fixed but we have to accept that the developers have other things to do and we just have to hope at some point in the future they return to revise Concorde X. 

Now, can we please return to how to use what we've got rather than pointing out it's faults, after all, that's what airline crew do every day isn't it? 

Are you using both autothrottles yet? 

Frazz

 

Frazz,

I'm sorry, it's not very clear.

You blame me for for taking part of the discussion which naturally deals with various points and issues of the simulation while, in turn from your part, you wrote "The speed hold modes in general are not as accurate as they used to be on Concorde X, I don't know why but it is beginning to irritate me especially on descent when she won't hold 350kts accurately."

When all is said and done what's your intimate objective ?

Fabrice

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Fraser Gale
5 hours ago, Fabrice Estienne said:

 

Frazz,

I'm sorry, it's not very clear.

You blame me for for taking part of the discussion which naturally deals with various points and issues of the simulation while, in turn from your part, you wrote "The speed hold modes in general are not as accurate as they used to be on Concorde X, I don't know why but it is beginning to irritate me especially on descent when she won't hold 350kts accurately."

When all is said and done what's your intimate objective ?

Fabrice

What I'm trying to say in as nice a way as possible, is that the faults of both the simulation platform and the addon simulation are generally well known by the people on this forum and that we can't do anything about them, so let us concentrate on how to use the simulation to the best of our abilities rather than concentrating on microscopic details of things we can't change. 

We are not test pilots who report issues back to the manufacturer. You have chosen the one comment in around 300 posts I have made that mentions a weakness of the simulation and you have every right to do so, but I think after all the procedural help and knowledge I have attempted to share over the time I have posted on this forum I can be forgiven for that, if you don't think so then that is fine.

Let us get back to helping each other be better virtual Concorde pilots rather than constantly taking apart the equipment or each other please.

Frazz

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Guys, I am doing some more refinements on the fuelburn.ini-file to match the fuel burn figures with the real counterpart even better. In the current state, the overall figures are closer to what the values should be, but the fuel burn at heavy weights and lower altitudes is lower than the original, while at low weights and high altitudes, it's higher. There is also a higher deviation for altitudes that are outside the optimal altitude curve. Once I will finish the correction, I will list the measured values for a range of altitudes and masses and compare them with the old fuelburn/air-file, as well as with the values for the real Concorde according to the "Niveau de Vol"-chart. Stay tuned!

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Seth Goodwin
On 4/4/2017 at 11:40 AM, Ray Proudfoot said:

I did try MAX CLB briefly but with such a short flight and light fuel load it was climbing at over 8000fpm. I decided that wasn't very good for the pax. 

I realize I'm late to the party, but I also don't know how much I'd worry about this either. Vertical speed rates aren't really discernible from a passenger prospective.

What is more discernible are 1) sudden changes in rate that cause g forces. and 2) Cabin pressure changes. To the first, as long as you easing into the climb and not making sudden "jerking" movements to chase the needle, a passenger isn't going to have any idea if a plane is climbing at 2,000 feet per minute or 6,000. Obviously 8,000 is a bit different as their will certainly be a higher climb angle in the seat than most are used to, but as far a passenger comfort goes that doesn't impact anything. As to the cabin pressure, given Concorde's higher cabin pressure differential you could basically keep cabin pressure near sea level for most subsonic cruising altitudes, again mitigating another potential discomfort.

 

 

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Fraser Gale

Indeed you are correct MrNuke and in fact when I was talking to a Captain about something similar his reaction was, and I quote:

"it doesn't matter, the passengers can't see because of the small windows" 

so only reasonably firm manoeuvres would cause distress. This did happen on one occasion when Concorde was flying charters at an air show and the captain at the time, carried out some quite violent manoeuvres with 100 passengers on board. The co-pilot went to see the passengers off and he saw one lady who looked seriously ill and asked her if she had enjoyed her flight. She said:

"I've spent most of the flight being sick in the toilet, but I loved every minute of it!" Shows the hold Concorde had on people.

Another info snippet: a captain on one of his last training flights out of London told me he hit an area of turbulence in the subsonic cruise and they were bouncing around a bit. He went to turn the seat belt sign on when the training captain stopped him and said not to bother as it would hardly be felt in the cabin - the flex of the airframe meant the flight deck bounced around more than the cabin. It is also responsible for the slight delay in pitch manoeuvres because the wing changes and the flight deck follows a second or so later after the fuselage flexes!

Frazz

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Ray Proudfoot
1 hour ago, MrNuke said:

I realize I'm late to the party, but I also don't know how much I'd worry about this either. Vertical speed rates aren't really discernible from a passenger prospective.

What is more discernible are 1) sudden changes in rate that cause g forces. and 2) Cabin pressure changes. To the first, as long as you easing into the climb and not making sudden "jerking" movements to chase the needle, a passenger isn't going to have any idea if a plane is climbing at 2,000 feet per minute or 6,000. Obviously 8,000 is a bit different as their will certainly be a higher climb angle in the seat than most are used to, but as far a passenger comfort goes that doesn't impact anything. As to the cabin pressure, given Concorde's higher cabin pressure differential you could basically keep cabin pressure near sea level for most subsonic cruising altitudes, again mitigating another potential discomfort.

 

 

My primary concern was not for my 'virtual' passengers but my ability to get fuel aft to keep CG within limits. Hence why I'm reluctant to engage MAX CLB with such a light fuel load.

However since that flight I have learned that a take-off CG of 52.5 is not correct. It should be 53. Using that combined with pumping fuel aft earlier may be enough to keep CG within limits.

I leave cabin pressure to the VFE. I haven't learned how to do all the tasks of pilot and FE yet. ;)

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