Calculating Subsonic Top of Descent

[Guest cdobison]

How do you calculate where to start your descent from subsonic? Is it done using the same "3 to 1" rule that airliners use? I have to admit, it's been so long since I actually had to "fly" an aircraft on FS that I have forgotten...LDS 767 and the PSS A320/330/340 calculates it for me!!!Chris

[Ray Proudfoot 8,924]

Hi Chris,Concorde had a slightly different set of rules. Naturally, the whole point of flying on this aircraft was to get as quickly as possible from point A to point B whilst staying within the noise regulations.On the EGLL-KJFK route assuming an altitude of FL570 Concorde would throttle back to idle at 215 route miles from JFK until the IAS was 350kts. Once that was achieved it descended at a rate of 3,000fpm whilst maintaining 350kts. At FL150 it reduced speed to 325kts and at 10,000ft would reduce speed to 250kts or less.That route was relatively straight-forward as the approach was over the ocean. The return flight to EGLL would have a slightly different descent profile as Concorde would need to be sub-sonic 30 miles before crossing the north Devon coast. I'm afraid I don't have specific details of that descent profile but at a guess I would start down (from FL570 again) around 230-240 miles from EGLL.The ToD point was calculated very carefully to ensure Concorde stayed as fast as possible for as long as possible to keep flight times to a minimum.Hope that helps.

[Guest cdobison]

Ray,Thank you for such a quick reply.I have been using the DECEL point of the flightplan to descend from supersonic cruise to FL390, 350kts IAS - but wasn't sure how to calculate the next step of the descent. I assume from your email that it is just a continuous descent? I have just flown the route BA001 to JFK and am about to embark on the return flight to Heathrow, so just want to operate it to the most effective way possible.Best regards,Chris

[Ray Proudfoot 8,924]

Hi Chris,As far as I'm aware it was a continuous descent although in r/w ops there were probably times when ATC wanted Concorde down quicker for traffic reasons. Suck it and see. Try the attached FS9 plan based on the r/w route. N42W67 is the Decel point.I do have AERAD charts for Concorde's routes. I'll dig them out later and see what the Decel point is for the return leg.Cheers,

[Guest cdobison]

Hi Ray,According to the flightplan I have, it should be N5022.0 W00845.0 as the Decel point on the return. I have about 1.5 hours of the return flight left so I will try it on a continuous descent and see how close to Min Stack Level + 1 I get by OCK which is what the pilot's would be aiming for on a quiet evening's arrival.Fantastic aircraft by the way, this is only my 3rd flight with it and I am very impressed indeed!Chris

[Ray Proudfoot 8,924]

Hi Chris,According to the AERAD chart there are two Decel points on the SL3 route to the UK - a winter one at N50 13.7, W10 16.2 and a summer one at N50 20.4, W08 58.9. Both slightly different to yours but not significantly so.I haven't flown her recently but feel the hankerings. Mind you, after flying a 737-700 for a while it comes as a bit of a shock to the system! :-eek What PSS have done is remarkable when you consider everything is just a bunch of 0's and 1's!Cheers,

[Guest AF011]

Hello all :) Any chance you can direct me to a location for the AERAD Charts, and can you also post again the attachment? It will no longer download for me. Thanks! Jim French, PSS Pilot for British Airways Virtual.

[Ray Proudfoot 8,924]

Hi Jim,My charts are paper. I don't think it's possible to download AERAD charts - sorry.Here's the EGLL-KJFK Concorde route again.

[pschlute 37]

Could you re-post the zip file, as it appears to be empty.Thank Youpeter

[Ray Proudfoot 8,924]

Peter,The attachments only stay around a few days unfortunately. Here you are...Cheers,

[pschlute 37]

RayThank youPeter

[Guest AF011]

HEllo Ray, Any chance you can make that file avaiable again? jim French

[Ray Proudfoot 8,924]

Here you are Jim.Cheers,