Date: 201501
Local time of day: 0601-1200
Location: ZZZ.Airport, US
Flight conditions: Marginal
Aircraft: EMB ERJ 145 ER/LR
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Taxi
ATC / advisory: Tower ZZZ
Reporter organization: Air Carrier
Reporter function: First Officer; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Situational Awareness
Second reporter function: Pilot Not Flying; Captain
Anomaly: Ground Event / Encounter Loss Of Aircraft Control; Ground Excursion Taxiway
Detector: Person Flight Crew
When detected: Taxi
Result: General Flight Cancelled / Delayed
Contributing factors: Airport; Human Factors; Procedure
Primary problem: Airport

Narrative: Flight was normal until the landing rollout. Braking action was reported as good by the previous arrival. ATIS reported thin; patchy ice on taxiways and ramps; and stated that the tower would give specific taxi instructions upon landing due to numerous taxiway closures. As I applied the brakes normally on landing; I noticed one slick spot on the runway; with the rest of the runway being dry. At 80 knots the captain took the aircraft; slowed the aircraft and turned off on taxiway B; as all high speed taxiways were closed. Taxiway Bravo was a 90 degree turn off with a slight downhill incline. As we turned off onto Bravo we slid slightly but were able to regain control for a few feet; then began sliding again. The captain and I were both on the brakes and he deployed the thrust reversers to try to stop the airplane; and he had the tiller over to try to regain directional control. Despite our efforts to stop; the airplane continued to slide into the grass until we came to a stop. Nobody was injured and the aircraft was undamaged. The event occurred because of the poor conditions of the taxiways. The braking action on the taxiway was nil; but was not reported as such. Although our speed was very slow upon turning off the runway; the ice on the taxiway and the slight downhill incline rendered directional control impossible. The condition of the taxiways was not accurately reported; which is also why two other aircraft slid into the grass that morning. Although the runway was bare and dry with good braking action; none of the taxiways had the same snow and ice removal priority. If conditions are bad enough that aircraft controllability becomes an issue; that information must be clearly and accurately disseminated to aircraft before landing. The difference between a NOTAM for 'patchy thin ice on taxiways' and an advisory for 'braking action nil on taxiways' is monumental; and could have resulted in either delaying the flight until airport operations cleared the taxiways or canceling the flight.


Second narrative: ...airport operations personnel came out to get us out of the grassy area we were in. They needed a lot of sand to provide traction for the tug. At one point during the [subsequent] pushback on to the taxiway the tug and airplane almost slid back down into the grassy area again due to the extreme icy surface conditions. We had to apply full brakes to prevent another incident. Everything that happened that day occurred at very low ground speeds.


Synopsis: Although braking action was good on the runway as advertised the taxiway where the EMB-145 exited the runway had not been sanded or otherwise treated; directional control was lost and the aircraft slid into an adjacent grassy area from which it was eventually towed to the gate. No damage or injuries. One of three similar instances that day.