B767-300 and 300 ER
Air Traffic Control Fully Certified
Situational Awareness; Communication Breakdown; Confusion
ATC Issue All Types; Deviation / Discrepancy - Procedural Published Material / Policy
General None Reported / Taken
Human Factors; Procedure
ZTL was running an experimental arrival procedure called Raptor 1. This arrival allows aircraft to descend from their cruise altitude to a low altitude in a very efficient manner. In order to achieve this efficiency; aircraft must fly the procedure in a very coordinated way. The aircraft are required to fly over several way points within a certain altitude range and at specific airspeeds. This procedure has gone through several revisions throughout the last several months due to problems ranging from aircraft performance; lack of crew understanding of required procedures and training; lack of understanding and training by air traffic controllers; and lack of expected aircraft conformance. On this night; ZME was issuing the Raptor 1 arrival to aircraft and providing required spacing to ZTL through the use of assigned airspeeds.  This was a change in the way we have been handling this procedure until now. B767-300 was handed off to the Rocket Sector already assigned the Raptor arrival and a Mach number. The airspeed assignment was to provide needed spacing with CRJ-200. The Rocket Sector did not think they were going the need more spacing between the aircraft; so they slowed B767-300 to Mach .75 and vectored the aircraft to the northeast. CRJ-200 was told to maintain 280 knots and given a pilot discretion descent to FL250. A short time later; B767-300 was turned back onto the arrival and given a clearance to descend at pilots discretion to FL250. When I took the hand off on both aircraft at DALAS; the spacing looked tight but I assumed the airspeed would quickly become comparable as the aircraft started to meet the speed requirements of the arrival. I issued a clearance to both aircraft to descend via the Raptor 1 arrival. Both aircraft were descending out of approximately FL280 at this time and should have started to fly the vertical portion of the arrival meeting all altitude and speed requirements. After a few minutes I noticed that the speed on B767-300 was not decreasing; but instead increasing as he descended. I instructed B767-300 to reduce to 250 knots in an attempt to maintain spacing between both aircraft. A short time later I asked B767-300 if he had begun his transition from Mach to indicated airspeed. He stated that he was assigned Mach .75 and that was 'what was in the box' and that was what he was flying. That was stated by the pilot when the aircraft was at FL215. Based on the training I was given on this procedure; and the training I have had from the FAA (7110.65) on when to expect an aircraft to transition out of Mach and start using indicated airspeed; this seemed to be a very low altitude. The 7110.65 states controllers should expect a transition no lower the FL240 and the information provided by the Airspace and Procedure office stated that we can expect a transition of this arrival between FL290 and FL240. I turned B767-300 30 degrees right off course; in order to maintain minimum spacing; but the turn was not issued early enough and separation was lost. After talking with management and the Captain of the aircraft several things were discovered that may have contributed to this event. The pilot was not informed that ZTL was using OPD arrivals. After the last test phase of this program it was determined that pilots should be made aware through their company's Dispatch office that they may be assigned the Raptor arrival. This procedure was implemented to ensure that pilots can become familiar with the arrival before reaching ZTL airspace. This did not occur with this flight. The pilot also asked if ATC issues a descend via clearance does that overrides any airspeed assignments given to him previously. This led me to believe that he did not understand what was expected of him during the descent phase of this arrival. After this conversation I looked up what Mach .75 would equate to in  knots at FL220 on a standard temperature day and I found it would equal 334 knots. The front aircraft was assigned 280 knotsuntil Rome VOR so this would explain the airspeed difference of approximately 60 knots between the two aircraft. Recommendation; I would recommend that there be more training for pilots and controllers on what phraseology is used and what the meaning of the descend via clearances mean. The procedure itself should state an altitude that all aircraft are required to be operating at indicated airspeed. The speed restrictions on the arrival plate should also be more prominent and not in a note at the bottom of the plate. I have heard from several other controllers that aircraft are consistently missing these speed requirements. I would also recommend that more restrictive altitude limits be implemented in order to keep aircraft at similar airspeeds.
ZTL Controller described a probable loss of separation event when traffic assigned the Raptor 1 OPD 'Optimum Profile Descent' did not comply with published restrictions.