The effect of voice communications latency in high density
D. Michael McAnulty
Randy Sollenberger, PhD.
Sollenberger, R. L., McAnulty, D. M., Kerns, K. (2003). The effect of voice communications latency in high density, communications-intensive airspace (DOT/FAA/CT-TN03/04). Atlantic City International Airport: Federal Aviation Administration William J. Hughes Technical Center.
The Federal Aviation Administration (FAA) Next Generation Air-Ground Communications program plans to replace aging analog radio equipment with the Very High Frequency Digital Link Mode 3 (VDL3) system. VDL3 will implement both digital voice and data link communications and will include special features such as controller override, antiblocking, and a transmit status indicator. There are two human factors concerns with the VDL3 system: voice quality and voice throughput delay. Previous research has determined that digital voice technology is highly intelligible and acceptable for Air Traffic Control (ATC) operations. Researchers from the National Airspace System Human Factors Group () of the FAA William J. Hughes Technical Center conducted a high fidelity, human-in-the-loop simulation to examine the impact of voice throughput delay on ATC operations. The communications equipment simulated the VDL3 system with controller override, antiblocking, and transmit status indicator features. The researchers examined ground system delays of 250 ms (current specification), 350 ms (practical alternative), and 750 ms (to demonstrate the sensitivity of the simulation measures) each with their appropriate airborne system delays. Ten controllers from Level 11 and 12 Air Route Traffic Control Centers participated in the study. The results indicated that there were no significant differences between the 250 ms and 350 ms delay conditions. However, the 750 ms condition did produce a significant increase in controller overrides, and the controllers rated it as interfering with some aspects of their communication (e.g., providing optional services). The researchers concluded that the VDL3 system with controller override, antiblocking, and a transmit status indicator can be implemented with a 350 ms ground system delay without causing problems for controllers.