Effects of Radio Frequency Coupling in Multiple Remote Tower Operation on Pilots

Abstract

Multiple Remote Tower Operation (MRTO) is a further development of Remote Tower Operation (RTO) that changes the way air traffic service (ATS) is provided at airports. Using MRTO, a single Air Traffic Controller can provide air traffic services to two or even more small airports with light traffic simultaneously, increasing efficiency, service utilization and cost-effectiveness. MRTO concept has been thoroughly proven to be feasible from the controllers’ point of view, but there are some issues that remain to be resolved from the pilots’ perspective. In order to safely apply MRTO, controller stated, that it is needed to “cross-couple” the radio frequencies of the served airports and to slightly adapt the standard radiotelephony phraseology by stating the relevant airport’s name in each radio call. Although these changes may appear to be only minor, their implications and effects on pilots have not been investigated scientifically, which motivated this study. In a human-in-the-loop real-time simulation experiment, 25 private and commercial pilots flew a Cessna C172 light aircraft at Braunschweig-Wolfsburg airport in a within-subject experiment design: one flight in an MRTO setting with coupled radio frequencies, and the other in a traditional RTO setting. The data analysis showed that the pilots’ overall mental workload was below an optimal medium during flights in both the RTO and MRTO cases. Workload differences were slightly, but statistically significantly higher in MRTO than in RTO, closer to but still below an optimal medium value. The measured situation awareness followed the opposite pattern, with slightly yet significantly lower ratings in the MRTO environment than in RTO. Attitudes towards MRTO were predominantly positive before and after performing the experiment. There were no mistakes or confusions in either flight performance or radio communication that could be attributed to the MRTO frequency cross-coupling. Therefore, the observed effects on mental workload and situation awareness are thought to be caused as well by the MRTO concept-driven higher number of radio calls that each pilot experienced during radio frequency cross-coupling. In summary, the effects of frequency cross-coupling in an MRTO environment compared to an RTO environment are statistically significant but slight, and did not impact the pilots’ mental workload and situation awareness to an extent which would affect their performance. In conclusion, frequency cross-coupling did not interfere with safe and efficient flight operations, and MRTO using frequency cross-coupling is therefore considered an appropriate and beneficial concept for small airports and airfields controlled or uncontrolled.