Airbus Industrie Undifferentiated or Other Model
Air Traffic Control Fully Certified
ATC Issue All Types; Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Published Material / Policy
Air Traffic Control Issued New Clearance
Human Factors; Procedure
I issued an Airbus a clearance to descend via the Mash1 arrival. At the time I issued the clearance; the aircraft was over Sector 13's airspace at FL240. The Airbus was supposed to cross FASON at or above FL240. FASON is in my airspace. I observed the Airbus descending so I told the R12/132 Controller to watch the aircraft. I asked the pilot to say altitude and he stated FL240. So; I asked him if he was on the local altimeter setting and he replied affirmative. He went on to say that his company had a new policy to use local altimeter settings as soon as a clearance is issued below FL180. I think the new policy should be reviewed. It seems dangerous to use local altimeters above FL180 even in descent mode. The possibility always exists that the aircraft could be stopped later for traffic while still in the flight levels. If this occurred; the flight crew would have to remember to reset the altimeter to 29.92. I doubt that here is a checklist for this. It seems safer to change altimeter setting when going through FL180. The Airspace and Procedures Office has contacted the subject company about this incident.
Given step down clearance from FL300 to FL260; aircraft descending and during the descent to 260 a descend via clearance given which has an altitude restriction of at or above FL240 over FASON; Captain and I; in error; set local altimeter of 30.37 at approximately FL250 while aircraft descending to 10;000 FT altitude selected in accordance with the descend via clearance. Aircraft continued descent and approaching FASON Captain selected ALT hold at 240 to insure the 'that or above' restriction at FASON was complied with. Our error was to set the local altimeter prior to reaching the FASON Intersection. We should have waited until after FASON to set the local setting during the descent. The Controller asked us what altitude we were at when we leveled at 240 and we explained our altimeter was set to local setting for our descend via clearance. Pay more attention to setting altimeter after complying with crossing restrictions.
ZME Controller described an altitude deviation during a descent clearance; the reports indicating the flight crew entered the local altimeter setting prematurely.