HS 125 Series
Air Traffic Control Fully Certified
Communication Breakdown; Confusion; Situational Awareness; Human-Machine Interface
Airspace Violation All Types; Deviation - Altitude Overshoot; Deviation / Discrepancy - Procedural Clearance
General None Reported / Taken
Human Factors; ATC Equipment / Nav Facility / Buildings
I was working the high altitude sector accepting southbound departures off SAT from the low altitude enroute sector. AR614 was active 250B270 with a flight of 2 which is a factor for southbound departures; often necessitating leveling the departure at FL240 until clear of the aerial refueling tract. The Hawker was the second of two departures in a row and low altitude had assigned a speed restriction to this aircraft of 290 KTS or less (290). I was not privy to the clearance as issued by the low altitude controller or the read back from the pilot; but I assume all was handled per 7110.65. Normal procedure would be for the Hawker to be assigned FL230 from the Low Controller and then after hand off completion; he would be changed to my frequency for continued climb (in this case only an additional one thousand feet until clear of the refueling tract). Often; these aircraft require a point out to the high altitude sector which lies north of my airspace (Sector 76) especially if they climb quickly. This aircraft's Mode C was quadruple 'X'ing due to his exceptional vertical rate. Therefore; there was no indication to either the Low or High Controller when he was reaching FL230; naturally; we try to avoid unnecessary intermediate level-offs. The aircraft would normally be switched as soon as separation issues are resolved and the hand off is accepted by me but prior to reaching FL230. In this case; there was no way to know altitude leaving without a pilot report. So; Low shipped the aircraft as soon as they had resolved their issues; which included speed restricting the aircraft to 290 or less for traffic ahead. The Hawker checked on to my high altitude frequency leaving FL232 climbing to FL290. Even swapping over to EDARC would not provide me with this altitude information until I heard it directly from the pilot. Coordination was quickly accomplished with the high altitude north of me (Sector 76) whose airspace the pilot was deviating. We acquired control and expedited the aircraft above the refueling tract. He topped the tract and separation was not lost. This appears to be a pilot deviation; but without hearing the tape I cannot be sure. Clearly; the pilot interpreted a speed assignment as an altitude assignment. This was a foreign pilot and it did not sound like English was his native language. Display Mode C information at all times and notify the Controller if something is outside of expected rates. ERAM already solves this problem with its EVRI (Exceptional Vertical Rate Indicator). Had we known all along what his altitude was; we would have transferred communications prior to him reaching FL230. In his initial check on; it was clear that he was climbing to FL290. This would have been much less of a problem if he had checked on leaving FL190 climbing to FL290 because there would have been time to correct the situation before he violated his assigned altitude of FL230. However; without any way to see this information; the low altitude Controller was 'in the dark' as to whether the aircraft was about to level at FL230.
ZHU Controller described an apparent pilot deviation involving an altitude assignment; the reporter noting the lack of Mode-C information contributed to the confusion.