B737 flight crew missed an assigned crossing restriction during descent into TPA. A late clearance and the distractions of weather and approach preparation were cited as contributing factors.
Synopsis
B737 flight crew missed an assigned crossing restriction during descent into TPA. A late clearance and the distractions of weather and approach preparation were cited as contributing factors.
Narrative
We were given an early; non-standard (not what the arrival says to expect) descent restriction from ZJX right after I had started getting ATIS; gate; and programming the performance computer. We made that restriction (FL250) and; as soon as we did; ATC gave us another; 'Cross fifteen miles south of JAYJA at or below FL210; descend; and maintain FL200.' The Captain was trying to program the FMC (we were in VNAV); but was having problems because EDISN is eleven miles south of JAYJA. I went ahead and put 200 in the MCP window as I needed to verify that before I got back to my performance computer and I thought we needed to get started down. The Captain realized the same thing and just selected Level Change at 280 KTS. I don't remember how far we were from EDISN at that moment; but I thought it would take about twelve miles to get from FL250 to below 210 and I thought the 280 KT Level Change would do it. I got back to my performance computer and didn't do anything to verify making the restriction. A few minutes later; ZJX came on the radio and asked; 'You are fifteen miles south of JAYJA. Are you below FL210?' I looked up and we were descending through FL229. I answered that we were passing that altitude. ZJX told us to tell him when we were below FL210 and called out traffic fifteen miles south of us at FL220. We cleared FL210 when we were about ten miles from that traffic based on TCAS.Going into a place like TPA with thunderstorms in the vicinity; I should have gotten my pilot not flying duties done earlier in anticipation of some deviations and non-standard descents. We both need to set up some way to monitor the restriction after we get the descent started (in this case) based on our old-school math. Afterwards we discussed putting JAYJA in the Fix page and putting a fifteen mile ring around it. All that said; I think ZJX set us up for this. He knew this was a tight descent; but gave us the instructions that alleviated him from having to monitor us and possibly do more work. In my opinion; a good Controller would have said; 'Descend and maintain FL200. Expedite through 210;' maybe even adding on the traffic call at that point. This would have gotten us started down right away and if we were not going down fast enough; he would have given us a vector. Obviously; there are times for these crossing restrictions; but I think this was an instance where some old-school controlling would have been safer for all involved. We were given a restriction that we physically could have made and we did not.
Second reporter narrative
We were flying the DADES 2 Arrival into TPA. ATC assigned five miles north of JAYJA at FL260. ATC then revised the clearance to cross JAYJA at or below FL260; cross fifteen miles south of JAYJA at FL210; and maintain FL200. The flight had a tailwind and there was convective weather in the area. The normal altitude at JAYJA is FL270. We made the original restriction of five miles north of JAYJA at FL260; and crossed fifteen south of JAYJA at FL225. It was a normal approach and landing.ATC needs to stop issuing these complicated clearances and expecting compliance with tight altitude restraints. We were simply not able to comply. By the time we realized it; we were approaching the restriction. If a restriction is required; twenty miles from the point does not give us enough time to comply. These clearances need to be given farther out.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.