In 1918, the U.S. Army started flying airmail. Airmail delivery was a creative gimmick to foster the growth of commercial aviation and develop infrastructure to support it, while at the same time serving as an active testbed for avionics development. None of the companies that were early platform providers exist today as they did then, and the same can be said for those who supplied early sensors, communications systems, etc.
The effort paid off and a commercial aviation industry was developed that has driven unbounded prosperity. We now are repeating history with the push into eVTOL aircraft and urban air mobility. Money is moving quickly into the eVTOL lane, and it is likely that this investment will continue and even accelerate. Just as the Army used airmail delivery as a way to create an ecosystem for commercial aviation in the 1920s, now, 100 years later, the U.S. Air Force is getting behind the eVTOL market. Through the Air Force’s Agility Prime initiative, there will be equipment buys and funded research to provide the bedrock for eVTOL market launch and acceptance.
However, the success of the eVTOL industry is not a foregone conclusion. Developers of these aircraft will have to demonstrate their safety and reliability, as well as find solutions to problems that are unique to the low-altitude urban operating environment. Fortunately, modern telemetry schemes — such as Ethernet via telemetry (EVTM) combined with rugged Ethernet-connected data recorders — can be leveraged to collect all types of sensor data that could assist not only with flight test goals, but also in better understanding issues such as urban weather and radio frequency (RF) multipath interference. Without solving these and other challenges, it is highly unlikely the eVTOL market will mature to revenue realization.
Historically, telemetered test data has been restricted to one-way communication, leaving little flexibility in data being transferred, with no way to change the information on the stream in real time, or change data feed efficiently. EVTM leverages existing telemetry infrastructure and RF channels to allow bidirectional transfer of packetized data over a standard serial stream RF link. The system at either end of the link sees the EVTM as nothing more than a data transfer hub — visualize a long-distance Wi-Fi connection.
Let’s look at how this capability could assist with studying urban weather and multipath interference, considering urban weather first. Operators of eVTOLs in urban air mobility applications will need to contend with “micro-scale” weather including turbulence around and above buildings and structures such as cell phone towers. Compounding this problem is the fact that lightweight eVTOL aircraft will be more susceptible to fluctuations in temperature, icing, wind speed and precipitation than larger conventional aircraft. Yet most business models for these operations hinge on being able to deliver passengers from downtown to the local airport in a timely fashion — which means being able to reliably predict the impact of micro disturbances.
Telemetry flight test campaigns have the potential to collect all types of weather information in real time, recording and transmitting via EVTM. This could help eVTOL developers better understand the impact of micro-scale weather and refine their designs accordingly.
Turbulence around structures isn’t the only challenge facing urban air mobility operators. Today’s urban environment is a quagmire of congested electronic RF spectrum caused by buildings, cell towers and the proliferation of cell phones. Without the resolution of multipath interference, there will be no urban air mobility, as management of large-scale air taxi operations will require the ability to constantly monitor and deconflict these aircraft.
A telemetry technique called adaptive equalization mitigates multipath. Through its utilization, one could test and validate the compatibility of system design focusing on areas such as electromagnetic interference, electromagnetic compatibility, multi-frequency global navigation satellite systems, power and data management. The payoff in resolving urban weather and RF multipath issues early in flight testing is more robust and airworthy eVTOL platforms that would operate at a higher level of safety.
The continuing evolution of communication standards and competitive pressure in the marketplace dictate that communication system architects must start the engineering design and development cycle while standards are still in a fluid state. Robust and comprehensive flight test campaigns can help eVTOL developers compensate for the lack of clear guidance on these fronts. Embracing modern telemetry techniques in the context of professional flight testing will go a long way toward building confidence in these new aircraft — and ensuring that capital continues to flow into this emerging market.