Date: 201504
Local time of day: 1801-2400
Location: ORD.Airport, IL
Flight conditions: VMC
Light: Dusk
Aircraft: A320
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Descent
Airspace: Class E C90
ATC / advisory: TRACON C90
Reporter organization: Air Carrier
Reporter function: Pilot Not Flying; Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Distraction; Communication Breakdown; Confusion; Workload
Second reporter function: First Officer; Pilot Flying
Anomaly: ATC Issue All Types; Deviation - Altitude Crossing Restriction Not Met; Deviation - Altitude Overshoot; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Air Traffic Control; Person Dispatch
When detected: In-flight
Result: Air Traffic Control Issued Advisory / Alert; Flight Crew Became Reoriented; Flight Crew Returned To Clearance; Flight Crew Took Evasive Action
Contributing factors: Procedure; Weather
Primary problem: Procedure

Narrative: Had incorrect barometer (30.27 vs 29.55) setting which resulted in leveling off approximately 700 [FT] below assigned altitude of 13;000 FT while descending into Chicago airspace. Received a message from dispatch prior to descend stating 'Attn crews: ATIS is reporting old info. Please check with dispatch for updated WX. The WX request page is still accurate.' We read the message but did not realize this was 1- specifically for us and 2 was referring to Chicago ATIS. We sent for and received Chicago ATIS just prior to descent which gave the barometer setting as 30.27. We did not notice the time on the arrival information was invalid. Shortly after this we received descent instructions including changes to crossing altitudes and speeds which created additional activities while descending. While inputting the arrival restrictions we passed transition level; set 30.27; completed the checklist and then leveled off at what we thought was 13;000 FT. Approach ATC contacted us; asked to confirm our altitude and informed us the correct altimeter was 29.55. We reset our altimeters and climbed back to 13;000 FT. We requested another ATIS which was completely different from the first one and also incorrect. We listened to the audio ATIS which gave the correct info and said at the end that the ATIS was 'unreliable.'The message from dispatch could have been clearer in describing the problem we were about to encounter which I have never in my entire aviation career encountered before (display of completely incorrect ATIS information). For instance: 'Attn flight X: Chicago digital ATIS is invalid or inaccurate. Here is the current correct weather at KORD: Do not rely on the ATIS from KORD!' Plain language would have alerted us to the gravity of the situation. Chicago should also not send known incorrect WX information via Digital ATIS. They should shut the system down until it works correctly as expectation bias of always receiving the most up to date ATIS crept into this situation compounding it.


Second narrative: Digital ATIS from ORD should have been taken offline or caused to send info that would have lead us to listen to the actual broadcast rather than relying on the ACARS printout.


Synopsis: A crew was on the ORD TRTLL 2 RNAV leveled at 13;000 FT and was queried about their altitude then notified the digital ATIS was wrong and their aircraft was 700 FT low. Digital ATIS nationwide was apparently in error.