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Guest tre1039

ATC - Not enought time to descend?

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Guest tre1039

Last night I flew from KBUF to KJFK for jetBlue flight 6 on an A320 (Wilco/Feelthere). During my descent into JFK, as I recall, ATC required that I was at FL120 and 250 knots by 40 miles from KJFK. I hit that mark. The problem however, is that I don't think ATC gave me enough time to descend to 1,900 feet to intercept the marker and follow the glideslope to the runway 22L. ATC lined me up downwind at 230 knots and base at 210 knots as it was supposed to, however, I was at maximum open descent rate (I think? about 1000 ft per minute) with my configuration/speed and ATC turned me towards the marker about 5 miles away when I still had more than 3,000 feet to go to hit 1,900 ft. In 3 minutes, according to my rough calculations, I would have flown approximately 12 miles at that speed, thus missing the target altitude for localizer interception -- and the final approach.If I slow the plane below the 230 and 210 knot speed restrictions once I'm in the pattern, I am slowing my descent rate as well, so it appears that my approach speeds are not the problem?It seems to me that the problem is that I am not given enough time to descend and that ATC should have started my descent further away from the traffic pattern.I am using FSX with SP2 and the following add-ons:Wilco Airbus Volume 1USA Ground EnvironmentUltimate Traffic (at 100%)AI SmoothRadar ContactFTG ACARSAny advice or thoughts would be greatly appreciated.

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I use the 737NG which is similar. You should have no problem descending to almost sea level from 12,000 feet (not FL120 - transition altitude in the U.S. is globally 18,000 feet) 40 nm out. The pattern speeds given by RC are caps. If I'm too high I slow to 180 on base with ten to fifteen flaps and increase from 25 to 35 turning final and before the OM go a full 40 slowing to Vref 40 +10 with gear down. While it is true while flaps apply lift, they also apply drag, particularly in the last stages, the last stage being specifically drag. You therefore can speed descent by applying less thrust, increasing your pitch down, and using flaps to keep speed down and decease your Vref to Vrefflaps (in effect reducing your stall speed + 30%), You can also drop your gear earlier to increase drag if necessary.RC generally applies intercept vectors so that you intercept the localizer further out than the OM. Which runway were you landing on and from what direction? I'll look at the procedure. Were you using an IAP flying the plate?You can also elect to use the NOTAMS feature for the airport which let you deviate from assigned altitudes once in approach without ATC complaint.

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Perry,<...I was at maximum open descent rate (I think? about 1000 ft per minute)...>>If I understand you correctly and you were descending at only 1000fpm no wonder you were too high. A descent rate of 2000fpm is quite normal and if maintained would get you down with room to spare.Cheers,

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Guest tre1039

Thanks for your response. 1000fpm was all the autopilot was giving me at 210 knots and flaps 10 in a vnav open descent profile on the airbus. I have to recheck the configuration on my next approach to make sure I am not missing something.

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Guest tre1039

Thanks. I was landing runway 22L coming from the NW. ATC turned me approx. 45 degrees downwind to enter the pattern and then approx. 100 degrees base to intercept the localizer and yes -- it was further out than the OM as I recall. I was not using an IAP flying the plate.

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If you're in VNAV mode are the altitudes in the FMC set realistically for the remaining waypoints?On a downwind, base approach I always have plenty of time to get down. It's only with straight-in approaches such as a landing on 35L at Milan from the south you really need to bring back the speed to 190kts whilst still 15+ miles out.

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Guest tre1039

At that point, because I am following ATC's altitude assignents, I am in an open descent vertical mode, which is selected rather then managed by the FMC. I incorrectly used the term VNAV in a previous post.Thanks.

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Hi Perry,From an earlier post I see you were approaching 22L from the NW. That would involve a downwind and base leg so you have plenty of time to get down to 1900ft.But your descent rate must be greater than 1000fpm. I don't know how familiar you are with the Airbus and the FMC but what you're describing is quite possible providing the descent rate is adequate. Ensure your final waypoint around 13 miles out has an altitude of 3000ft and you should easily get there. Without sitting alongside you it's difficult to know how your flying this.As with many things practice is the key. :-)

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I am not familiar with the Airbus terminology but once receiving vectors I assume you have something similar to Boeing's MCP control of the autopilot with auto-throttle by a speed setting, altitude setting, and vertical speed (descent) mode available. Among these controls along with a flap schedule you should be able to maintain a proper descent profile without any spoiler/speed brake deployment at the pattern speeds I mentioned unless steep descents are required due to terrain obstacles.

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Perry,One more consideration to take into account is the wind componant during decent. While it is unusual to have very strong winds during approach, the possibility of such an event (even 20, 30, 35kts) headwind or tailwind can have a effect on your decent rate.The wind factor wasn't mentioned so far so just wanted to remind you keep an eye on the wind vector display as well.Subs

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