MD-11
Flight Crew Flight Engineer; Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 84; Flight Crew Total 8500; Flight Crew Type 1970
Situational Awareness; Human-Machine Interface; Distraction; Communication Breakdown; Workload
ATC Issue All Types; Deviation - Speed All Types; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Clearance
Air Traffic Control Issued New Clearance
Human Factors; Procedure; Chart Or Publication
We may have exceeded the required airspeed at ROCAB on the [MEM] TAMMY RNAV STAR; landing north transition. The Captain was flying and I was the pilot monitoring. Flight arrived from the west. But first; some aircraft autoflight system background. The MD-11's automation [is programmed to achieve exact compliance with airspeed and altitude crossing restraints at waypoints on such arrivals]. However; it ensures altitudes will take precedence. In other words; it will speed up to comply with altitudes if high on profile; thus exchanging altitude for airspeed. This usually happens when arriving from the west; especially in the winter due to the usual strong tailwinds.Memphis ATC tries to move traffic expeditiously. This is great if given enough notice to allow the airplane to meet the requests. Here is what happened. ATC cleared us direct TAMMY and to comply with the STAR thereafter; which we attempted to do. The Captain used speed brakes; to the best of my recollection; for the entire descent until very close to ROCAB where we were given a heading off of the arrival. The Captain had me ask ATC what speed they desired. They stated to comply with the arrival published speeds. We made the altitude restrictions; but I'm not sure of the speed restriction at ROCAB. In fact I don't believe the speed that ATC wanted us to fly was technically the speed we were required to fly; as I believe the clearance for the heading was immediately before ROCAB; which has a 230 KT speed restriction. The speed restriction on the arrival prior to ROCAB is 290 KTS. We were either at 230 KIAS or close to it; I'm sure we were definitely below 250 KIAS. Regardless; what we thought and what ATC thought were two different things. We assumed the Controller wanted 230 KTS; so that was our target speed. That is also why we asked what speed he; the Controller; desired. He never gave us an exact number.Here's what I recommend as the easiest solution to this confusion; clear us for the arrival; let us fly it; and no short cuts. I would not be writing this report if this were the case. Or else; since we are supposed to depart ROCAB on a 067 degree heading. Let us fly that heading. If something else is desired; then change the procedure or use this type of clearance; 'upon reaching ROCAB; depart ROCAB on heading (insert desired ATC heading). This is very clear to all pilots. When given headings at/around clearance limits; it gets confusing.Have the Approach Controller's jumpseat on our aircraft to see how difficult things get when given 'short cuts.' The airplanes I fly are programmed to fly the most efficient and exact flight profile to save the most amount of gas; and as a result; limit noise pollution.Limit the short cuts for east bound traffic--especially in the winter--to at most 10 track NM; as it is very difficult to comply with both altitude and speed constraints when given short cuts. Note that every short cut we get requires the usage of speed brakes to comply with the clearance.Have ATC provide us information; such as 'expect more direct routing;' as soon as possible; preferably when descending while on center frequency. Knowing what sequence we will be allows us to anticipate ATC's intentions of giving us a shortcut. If we know we are leading the pack; then we can quickly program the FMS to start an earlier descent; which isn't the most efficient; but will alleviate a lot of problems.Pilots need to stop accepting clearances blindly; as sometimes we just can't comply with what they're asking us to do. From a CRM point of view; we need to stop trying to 'make it happen.' Note that most pilots I fly with are mission oriented; which is good for the military; but may not be for civilian flying.
The flight crew of an MD11 experienced difficulty complying with the crossing airspeed restriction at ROCAB on the TAMMY RNAV STAR to MEM when they had previously been cleared direct to TAMMY thence descend via the STAR.