A ZME Controller and an F-18 crew describe an altitude deviation during descent from FL350 to 340 causing a TCAS alert in a DC10 at FL330.
Synopsis
A ZME Controller and an F-18 crew describe an altitude deviation during descent from FL350 to 340 causing a TCAS alert in a DC10 at FL330.
Narrative
One aircraft I was working was an F-18. I noticed he was landing NMM; and that he was an F-18; RVSM; and level FL350. At the time; the F-18 was located approximately 50 NM west of JAN. I had to descend him due to the proximity of his destination and the fact that he had traffic at the same altitude. I called R45 and requested FL330; which the Controller unabled. However; the Controller then approved FL340. I quick-looked Sector 45; and noticed that he had traffic east of the F-18; a DC10 (I think this was the type aircraft). I advised R45 that I was going to descend the F-18 to FL340 and turn him twenty degrees right so that that Controller could descend him reference his traffic. I instructed the F-18 to descend to FL340 and turn twenty degrees right for traffic. I confirmed the read back; then switched him to R45's frequency. Thirty seconds or so later; I heard R45 ask the F-18 what his altitude was. I then learned that the F-18 had descended below his assigned altitude and that The DC10 had responded to a TCAS alert. I have no particular recommendations as pilot/controller read back/hear back has been emphasized many times in the past. I confirmed my clearance to the F-18 by hear back; thereby completing my part of the communication with the pilot reference my clearance.
Second reporter narrative
Memphis Center descended us out of FL350 to 340. In the descent to FL340; a vector 30 degrees right; a frequency change followed by a master caution (problem with the airplane) within the cockpit averted my attention momentarily which caused a descent through the assigned altitude. This deviation was immediately corrected as I leveled off at FL340. There was another aircraft below us that we were visual [with] as flight path de-confliction was obtained. Most military aircraft are not RVSM capable and while the F-18 Super Hornet is; autopilot is disengaged while climbing or descending. Although this was pilot error some consideration might be taken in the future to climbing or descending fighter aircraft in close proximity to larger aircraft; as it is much more maneuverable and could possibly set off TCAS easier.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.