Date: 201910
Location: ZZZZ.Airport, FO
Flight conditions: VMC
Light: Daylight
Aircraft: B747 Undifferentiated or Other Model
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Cargo / Freight / Delivery
Flight phase: Taxi
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Not Flying
Reporter qualification: Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine
Human factors: Communication Breakdown
Anomaly: Deviation / Discrepancy - Procedural Published Material / Policy; Ground Event / Encounter Other / Unknown; Ground Excursion Taxiway
Detector: Person Flight Crew
When detected: Taxi
Result: General None Reported / Taken
Contributing factors: Procedure
Primary problem: Procedure

Narrative: We landed in ZZZ on Runway XR. We taxied abeam Gate XX and shut down as instructed; facing west. Mechanic plugged in the headset and told us that we would tug to Gate Y. He informed us that he would be off the headset while we were being towed; and would plug back in when we parked. I assumed that this was a normal procedure described that this is what we would do. The procedure did not say anything about not having communication with the mechanic or the tug like we normally do. I've never operated into this Gateway before. We had a delay of a few minutes while other aircraft were being pushed back. Once they were clear Ground Control told us to continue. However; we had no communication with the tug. I assumed the tug driver was listening on the Ground Control frequency because we started to roll forward after Ground told us we were clear. I was told later by the gateway manager that the airport usually provides a follow me car for the tug driver. We never saw any follow me car. The turn from the taxiway onto the lead in line for Gate Z was a 90deg turn and it appeared we had plenty of space to make the turn. As we approached the turn the tug driver departed the taxiway centerline to the left. It appeared like he was trying to give himself space to make the turn. I looked to the left and saw that there were no taxiway lights and we had a paved surface and room to go left. Certainly the left main gear and perhaps even the left body gear most likely crossed the edge of the taxiway onto the outer area. At this point I weighed my options of either applying the brakes and stopping the aircraft versus allowing the tug driver to continue. As the surface looked to be flat with no obstructions I chose not to apply the brakes which would surely have damaged at least the towbar; if not the aircraft and tug. Additionally; the aircraft was very light; I assumed the tug driver was familiar with this procedure; and as I previously stated the area off the left of the taxiway appeared flat and free of obstructions. After shut down I asked to see the gateway manager. We had a discussion about this whole procedure being abnormal. I told him we need to have communication with the tug during towing and that the aircraft should never depart the taxiway centerline.




Synopsis: B747 Captain reported that inability to communicate with the tug crew caused the aircraft to momentarily depart the taxiway centerline.