Once the exclusive domain of the military and, with few exceptions, flying outside controlled airspace, unmanned aerial vehicles (UAVs) are now slowly nudging their noses under the civil tent. Already, USAF RQ-4 Global Hawks routinely fly across the U.S. on their way to undisclosed overseas destinations, but they pose little threat of conflict since they cruise above FL650 and get up there using a steep spiral climb over Nellis AFB in California.

Computer-controlled from taxi to full-stop landing, the $30 million, turbofan-powered, DC-3-size Global Hawk is a star performer, cruising at better than 300 knots for more than 35 hours with a full load of highly classified reconnaissance and covert communications gear.

But the coming generation of UAVs isn’t going to be quite as agile or, so far, quite as big, and the major concern now is that many of them are designed to operate in Class-A airspace between FL180 and FL450. What’s more, few of them will be as autonomous as the Global Hawk, and almost all will be controlled by pilots at distant locations on the ground. How distant? Citation-size Predator UAVs, some armed with air-to-surface missiles, fly missions every day over Iraq and Afghanistan under the control of pilots at Nellis, more than 7,500 miles away, via satellite communications links.

But UAVs don’t need to be quite that sophisticated. In April, the Charles County, Md., Sheriff’s Office used an $8,500, four-foot-wingspan UAV to monitor an 8,000-strong biker rally at the local fairground. Equipped with GPS, a video camera, a VHF radio link and controlled by an operator on the ground using a handheld joystick, the “CyberBug” cruised over the event at 500 feet, looking for unruly behavior, traffic problems and accidents in the area.

Yet even a four-foot wingspan is still a fairly large machine to the UAV community, where micro-UAVs with spans of less than a foot are being developed. These midgets are planned to fly in quiet “swarms,” and their tiny artificial intelligence brains will exchange information with one another and the ground control station, to better define the situation below. Both the military and the Department of Homeland Security (DHS) are reportedly extremely interested in this form of covert surveillance.

So how much of a threat would UAVs pose if they were to fly in civil airspace? That’s a question the FAA and the government/industry RTCA organization have been wrestling with for some time, as did  high-level European task force in 2003.

The Europeans didn’t feel that UAVs would be a threat, provided that they and their ground-based “flight decks” complied with all airworthiness standards, carried all required navcom and surveillance avionics, required no special ATC handling and were controlled from the ground by appropriately certified pilots.

ATC communications with pilots would be over radio datalinks on appropriate ATC voice frequencies, and the unmanned character of the vehicle would be “transparent” to controllers. Currently, it seems likely that FAA policy and the conclusions of the RTCA study will echo the European position.

Obstacles to Civil UAVs

On paper, civil UAV operation looks good, but four vexing issues remain unresolved. These are collision avoidance, pilot qualifications, communications failure and emergency procedures, and the risk of hijacking by hackers.

Collision avoidance–called “sense and avoid (S/A)” in proposed UAV IMC operations–is challenging because while most UAVs will carry ATC transponders as well as some sort of weather-penetrating radar or other sensor to give the ground-based pilot the “eyes” to carry out evasive maneuvers, few of them could afford to carry TCAS.

Consequently, in an encounter between a TCAS-equipped aircraft and a non-TCAS equipped UAV, the pilot of the latter, instead of correctly remaining level while the TCAS aircraft first interrogated and then avoided the UAV, might also use his or her own S/A sensor to attempt an uncoordinated avoidance maneuver, with potentially disastrous results. An A320 was forced last year to make a last-moment steep turn over Kabul to avoid a small, transponderless military UAV that was approaching head on but difficult to see.

This raises the question of UAV pilot qualifications. Current thinking favors possession of a private pilot’s license and an instrument rating but does not stipulate appropriate levels of previous experience. However, current thinking does not seem to address the question of how capable such individuals would be in high-speed, medium- to high-density traffic situations. It seems likely that professional airspace users will demand that UAV operators have experience in busy jet airspace.

UAV Navigation

Similarly, until recently the UAV community felt that programming the UAV’s FMS and autopilot to alter course immediately to the nearest diversion airport or to the GPS coordinates of open ground effectively addressed the possibility of communications failure. However, a recent incident over Afghanistan raises questions about the appropriateness of the procedure. After losing its communications link, a Global Hawk failed to divert and the pilot never regained control. The UAV has not been found. It is assumed to have fallen into a remote, uninhabited area.

The suspected cause of the incident is an onboard computer glitch, but the failure of both the com link and the onboard flight system has raised questions about whether conventional airworthiness integrity levels are sufficiently stringent for unmanned flight.

The fourth issue is the risk of computer hackers breaking into and taking over communications uplinks to the vehicle. Taking control of a UAV could be a major coup for hackers. Military systems are said to employ encryption techniques to prevent such an event, but there is little evidence that civil UAV advocates are planning such protective measures.

A frequently stated goal of the UAV community is to achieve an equivalent level of safety (ELS) to manned aircraft, but the lack of  human pilot in some situations, such as a critical system failure or other emergency on final approach, could cause authorities to set the bar higher for the ELS for unmanned operations.

When will UAVs start to appear in Class A airspace? The Access 5 consortium, which includes NASA, the FAA and six UAV manufacturers–Aerovironment, Aurora Flight Sciences, Boeing, General Atomics, Lockheed Martin and Northrop Grumman (collectively called the UAV National Industry Team, or Unite)–aims to achieve “file and fly” approval within five years for routine operations above FL450 and anticipates extending that to FL180 some years later.

But we can expect a good deal of test flying at all altitudes well before then, although the FAA will probably require a chase plane to follow a UAV flying above FL180. Last year, in fact, the DHS was already flying UAVs along the Arizona/Mexico border looking for illegal immigrants, and the UK Ministry of Defence recently placed a $1.5 billion order for a large number of UAVs to patrol its coasts and its overseas military installations. More recently Thales and Elbit demonstrated a large UAV in Wales.

Unquestionably, then, UAVs are coming, but professional pilots must insist that with their entry into civil airspace, safety is never compromised.