Date: 201508
Location: ZZZ.Airport, US
Aircraft: Commercial Fixed Wing
Operator: Air Carrier
Operating under: Part 121
Flight phase: Taxi
ATC / advisory: Ground ZZZ; Ramp ZZZ
Reporter organization: Air Carrier
Reporter function: Ramp
Human factors: Communication Breakdown; Distraction; Physiological - Other
Anomaly: Ground Event / Encounter Other / Unknown
Detector: Person Ground Personnel
When detected: Other During Tow Operations
Result: General None Reported / Taken
Contributing factors: Equipment / Tooling; Procedure; Human Factors
Primary problem: Equipment / Tooling

Narrative: While making a turn within the safe limits on taxiway bravo; the 100 percent Over Steer siren went off. This siren is a poor design function of the supertugs. This siren is so loud that it keeps you from both concentrating on moving the plane in a safe manner and also from hearing and communicating on both our hand held radios as well as our Air to Ground radios we use to communicate with the FAA Tower and also our own Ramp Tower. I feel this is a life and death situation due to the fact that we are crossing active runways and also moving around on active taxiways. This siren will not shut off until we lower the plane and disconnect from the plane.

Callback: The reporter stated he is part of a large Ramp crew that moves and tows over a hundred aircraft every day using equipment known as supertugs that include models from several different companies. Many of these tugs have a selector switch to set up the operation limits required to tow different type of aircraft. The Nose Landing Gear (NLG) wheel/tires are captured in a cradle and raised off the ground and secured in the aft section of the tug frame.The reporter stated an Oversteer Warning System is built into the tug's steering controls to remind the tug operator of the turning radius of the NLG and to look at the back of the tug and check for security of the cradle if the 100 percent oversteering limit warning occurs. He believes the warning system on these machines are not calibrated correctly due in part to their ground equipment mechanics have not had adequate training to properly calibrate the sensors. Many of the oversteers are unwarranted because the tug drivers have not exceeded the 100 percent limits. And yet; the Oversteer Warning System siren still goes off with a loud; shrieking; ear piercing sound inside of a small cab the operator is driving the tug from. The shrieking siren sound overwhelms the Ground Controller; Ramp Controller and tug operator's efforts to communicate with each other on the two hand-held radios the tug operators use during tow operations. The siren cannot be turned off and is a safety hazard interfering with two-way communications required to safely tow aircraft across active runways and taxiways.The reporter stated that with older models of the supertugs; a flashing warning light came on in front of the tug operator's view alerting to the oversteer without interfering with radio communications. He was recently told by one of his Supervisor's the tug manufacturer was informed of the safety concern caused by the severity of the warning siren.



Synopsis: A ramp crew member reports his concerns about a safety hazard caused by the 100 percent Oversteer Warning System siren sounding off inside the cab of their supertugs during aircraft towing operations. The loud; shrieking siren sound overwhelms the Ground Controller; Ramp Controller and Tug Operator's efforts to communicate with each other; especially when crossing active runways and taxiways. The siren cannot be turned off unless the aircraft is disconnected from the Supertug.