Widebody Transport
Flight Crew Air Transport Pilot (ATP)
Situational Awareness; Distraction; Confusion; Communication Breakdown
ATC Issue All Types; Deviation / Discrepancy - Procedural Published Material / Policy
Air Traffic Control Issued Advisory / Alert; Flight Crew FLC complied w / Automation / Advisory; Flight Crew Became Reoriented
Procedure; Chart Or Publication
Informational report only...high potential for altitude deviations due wrong Transition Level on ATIS (EGSS) and QNH altitude given London Approach. EGSS ATIS (radio; digital not available at this location) advertised a transition level (TL) of FL055. Inbound with London control; we were given a descent to 6;000 feet with a QNH of 1034 hPa (hectopascal). As we descended through about FL090; I asked the controller what the Transition Level (TL) was due to the information on EGSS ATIS. He responded we needed to have 1034 set by 7000 feet and go to 6;000 feet. We complied with no issues. Upon landing at EGSS; we queried the ground controller as to the differences in Transition Levels used by ATIS and London Control. He said standby; he'd ask his supervisor. Upon return; he stated 'we did everything right' and we were 'technically correct' with regard to the TL issue. He then said; 'in their defense; they issue 6;000 feet 200 times daily'. Problem is with the differences between the TL with 1013 and barometric altitudes of 1034 hPa; we were looking at a rather large error of over 600 feet had we used the advertised TL of FL055.  Had we not verified exactly what London Control wanted; we may very well have descended to an inappropriate altitude using 1013 at 6;000 feet rather than the advertised 1034 causing a violation or worse. The key words to trigger my query was we were given an altimeter setting of 1034 and the altitude of 6;000 feet. We then re-verified the ATIS information and caught their discrepancy. It appears either ATIS was wrong or London Control was wrong as they were both using a different TL. The TL should be higher than the TA (Transition Altitude) and both should be on the same page as this location; the TL is 'by ATC'. Further aggravating the issue is the perception of 'no big deal'. High frequency saturation and unusually high work load is common in England which can cause problems. Multiple ATC agencies not using the same Transition Level with a very large difference in altimeter settings due to high pressure system (1034 HP). Agencies need to coordinate better and verify Transition Levels.
A Captain questioned the EGSS FL055 ATIS transition level while descending to 6;000 feet and was told it should have been FL070. A transition at FL055 would have resulted in a 600 foot altitude error.