Unmanned Aerial Vehicles (UAVs), or Unmanned Aerial Systems (UAS) as the Pentagon prefers to call them, were developed to be three-dimensional creatures, that is military machines designed to conduct “3-D” dull, dirty and dangerous missions deemed too hazardous for humans. However, with increasing interest and operation of drones for public purposes and commercial tasks, UAS are now entering a fourth dimension, that being of a ‘domestic’ nature.
But the snail’s pace in promulgating regulations that would allow for regular flights of military, public-use and civil UAS in the National Airspace System (NAS) is holding back the potential of the unmanned technology and the number of non-military missions envisioned by UAS proponents. And Federal Aviation Administration (FAA) officials appear to be in no rush to establish “rules of the road” for unmanned aircraft operations in U.S. civil airspace.
To make matters worse, the most visible use of non-military drones within U.S. borders was marred by a crash two years ago that raised serious concerns over what is needed before pilotless planes are allowed to operate in U.S. airspace over both populated and rural areas.
Simply stated, an unmanned aircraft is a device that flies with no onboard pilot. UAs can either be remotely controlled from the ground by an operator or preprogrammed to conduct the entire flight without intervention.
Unmanned aircraft come in all shapes and sizes. They range in wingspan from six inches to 246 feet, and can weigh as little as a few ounces or as much as 100,000 pounds. Some fly no higher than rooftops, while others fly well above piloted aircraft altitudes. Today, according to the FAA, more than 50 manufacturers offer nearly 150 UAS products, with many others poised to enter the commercial marketplace.
The one thing they have in common is that their numbers and uses are growing dramatically and “regulatory standards need to be developed to enable current technology for UA to comply with Federal regulations,” the FAA believes.
The National Transportation Safety Board (NTSB) held a two-day forum on the safety of unmanned aerial systems April 29-30 in the NTSB Board Room and Conference Center in Washington, DC. The forum included representatives from the military, industry, the FAA, and government agencies involved in UAS operations.
The forum provided an opportunity for the Safety Board and interested parties to discuss the safety implications presented by the growing use of UAS in the NAS. Issues addressed included: regulatory standards; integration within the NAS; perspectives of current UAS operators; design, certification and airworthiness; human factors; and, future UAS applications.
While military UAS fly at will above overseas combat zones and in controlled military airspace domestically, they are only allowed to fly on a case-by-case basis in non- restricted airspace, the best example of which is the U.S. Customs and Border Protection’s (CBP) use of drones for spotting illegal border crossers and drug smugglers.
CBP operate MQ-9 Predator B UAS in Arizona to monitor the US/Mexico border and will soon stand up a second Predator base in North Dakota to keep tabs on the border with Canada. The law enforcement agency hopes to acquire two dozen Predator Bs for overland and maritime interdiction missions.
It is also developing a capability in which Predator Bs and support equipment would be loaded onto U.S. Coast Guard C-130s to handle catastrophic natural disasters and/or monitor major international sports events. The quick-reaction detail would be pre-authorized to fly in civil airspace.
The forum is a result of the Safety Board’s investigation of a CBP Predator B crash near Nogales, AZ, on April 25, 2006. The drone, which is about the size of a Cessna 152, crashed within 100 yards of a house in a sparsely populated residential area. Luckily, no one on the ground was injured in the non-fatal mishap, but the remotely piloted 66-foot wingspan drone was substantially damaged.
The Board’s October 2007 meeting on this accident resulted in 22safety recommendations to address perceived deficiencies associated with the civilian use of unmanned aircraft.
“The Nogales accident surfaced a number of important questions that need to be addressed if UAS’s are to operate safely in the National Air Space,” said Board Member Kitty Higgins, who chaired the forum.
The Predator B flight originated from the Libby Army Airfield (HFU), Sierra Vista, AZ.
The flight was being flown from a ground control station (GCS) located at HFU. The GCS contains two nearly identical consoles, pilot payload operator (PPO)-1, and PPO-2.
During a routine mission, a certified pilot controls the UAV from the PPO-1 console and the camera payload operator (typically a U.S. Border Patrol Agent) controls the camera from PPO-2. The aircraft controls (flaps, stop/feather, throttle, and speed lever) on PPO-1 and PPO-2 are identical. However, when control of the UAV is being accomplished from PPO-1, the controls at PPO-2 are used to control the camera.
The pilot employed by GA-ASI as part the Predator B turn-key operation reported that during the flight the console at PPO-1 “locked up”, prompting him to switch control of the UAV to PPO-2. Checklist procedures state that prior to switching operational control between the two consoles, the pilot must match the control positions on the new console to those on the console, which had been controlling the UAV.
The pilot stated in an interview that he “got in a hurry and did not use the checklist.” The result was that the stop/feather control in PPO-2 was in the fuel cutoff position when the switch over from PPO-1 to PPO-2 occurred. As a result, the fuel was cut off to the UAV when control was transferred to PPO-2.
The pilot stated that after the switch to the other console, he noticed the UAV was not maintaining altitude but did not know why. As a result he decided to shut down the GCS so that the UAV would enter its ‘lost link’ procedure, which called for the UAV to climb to 15,000 feet above mean sea level and to fly a predetermined course until contact could be established.
But with no engine power, the UAV continued to descend below line-of-site communications and further attempts to re-establish contact with the UAV were not successful.
NTSB investigators said lockups involving either PPO-1 or PPO-2 had occurred 16 times over the four months preceding the accident. Although the presence of redundant control consoles could mitigate the safety risks associated with a console lockup event, repeated reliance on this backup system increases pilot workload and the corresponding risk that an undesirable outcome will result.
Although a backup console is available to the pilot in the event of a lockup of PPO-1, it likely that this backup console will be in the fuel cutoff position when it’s needed to backup PPO-1. Should the UA pilot fail to complete the condition lever reconfiguration step on the console transfer checklist to address the PPO-1 failure, inadvertent engine shutdown is all but assured.
Although some aural and visual indications were provided to the pilot by the Predator B ground control station, the most critical indication during the accident sequence, the engine out condition, was buried among other less critical information in the heads down display making the warning indication inconspicuous to the pilot. When the console locked up during the accident sequence, there was no warning indication presented to alert the pilot to the loss of control.
Rather, the pilot detected the condition using indirect queues such as frozen images on the display screen. These indications do not provide the pilot with the ability to quickly and precisely determine the nature and urgency associated with unsafe conditions such as an engine-out / or console lockup event.
When the engine shut down during the accident sequence, the UA lost its primary source of electrical power and this caused critical systems to revert to battery power to continue operation. However, a momentary surge caused by the immediate transfer of these systems to the battery compelled the system to reduce the load on the battery, and, as a result, electrical power was cut to critical systems such as the transponder and the satellite communication link.
Because the accident pilot sent the UA to its lost link mission following the engine shutdown, communications between the GCS and the UA were discontinued at the time the transponder dropped off line. Without its transponder, no live link to the GCS, and no pilot onboard to report its position, the accident UA was invisible to ATC. The burden of separation was placed solely on other aircraft in the NAS, and their ability to see and avoid a potential conflict with the uncontrolled UA.
An additional concern related to the loss of engine power was the inability to restart the engine during the accident sequence. The investigation revealed that the engine on CBP’s Predator B can only be restarted in-flight if commanded by the pilot using the line of sight, or LOS, communication link between the GCS and the UA. This means that engine restart is not possible when the UA is in lost link mode or when LOS control is lost.
Maintenance plans, procedures, and oversight were also issues identified in this investigation.
A National Transportation Safety Board (NTSB) probe determined that the probable cause of the accident was the pilot’s failure to use checklist procedures when switching operational control from a console that had become inoperable due to a “lockup” condition, which resulted in the fuel valve inadvertently being shut off and the subsequent total loss of engine power.
The Predator B loss “makes it clear that significant design and operational safety improvements must be made before UAS can safely share airspace with airliners carrying passengers, cargo, and crews or fly above populated areas,” says the Air Line Pilots Association (ALPA). “This first-of-its-kind NTSB investigation shows that these unmanned vehicles and ground support equipment simply aren’t designed or built to the same high standard as airliners and that they don’t have the same operational capabilities that ensure safety.”
In opening the UAS public forum, Higgins said more needs to be established regarding UAS operations in the NAS, including a better understanding on potential human and technical failures of unmanned aircraft systems. She said the event provides “a rare opportunity to look ahead and prepare for the future. Safe operation of UAS in the NAS must be assured if the full potential of UAS is to be realized.”
Doug Davis, head of the FAA’s Unmanned Aircraft Program Office, discussed the agency’s roadmap and rulemaking for large and small UAS. He said market surveys indicate that the majority of UAS developed in the next decade will be under 20 pounds. Davis said the rulemaking process will be lengthy with a projected final rule for UAS not due until 2010 or 2011.
Darren Gaines, with the National Air Traffic Controllers Association, said integration of UAS in an already saturated NAS must be done safely. “Everybody wants to play in the NAS. We consider ourselves the referees there to make sure everybody gets along, and more importantly, make sure nobody gets hurt or worse.” He said “controllers are cautious, conservative and skeptical when it comes to new ideas. UAS is all new to us. We’ve got to get a handle on what to expect when you mix UAS with conventional aircraft.”
While many proponents believe that development of “detect and avoid” sensors will allow controllers to mix manned and unmanned aircraft in the NAS, USAF Lt. Col. Dallas Brooks said detect and avoid is not “Holy Grail” technology. “We need to go end-to-end across the NAS to determine what to do procedurally and with technology. I believe many UAS will be capable of achieving a level of safety equal or better than manned systems. The question is how fast we can get there.”
Capt. Ellis Chernoff of the Air Line Pilots Association (ALPA) raised a number of concerns regarding UAS hardware and standards. Regarding pilot training, Chernoff said “ALPA believes a well-trained, well-qualified pilot is the most important safety component of the commercial aviation system. Automation and technology is no substitute for judgement, experience and training. UAS pilots are not at risk in being killed in an accident. Just because they are not at risk does not mean they should not meet the same high standards as pilots that fly manned aircraft. UAS pilots must be licensed and regulated by the FAA.”
Chernoff said “integration of UAS in the NAS is not as simple as many would like to believe. Safety and security of the NAS remains paramount. Industry is trying to gain public acceptance of UAS. That will be lost if UAS introduction fails to be safe or erodes the fabric of aviation safety.”
Michael Kostelnik, a senior official with the CBP, said the Predator B has become “the awkward poster child” for UAS in the NAS. “Nevertheless, it (the crash) does highlight the risks of these systems.” He noted that the crash was caused by human error, not mechanical failure. “We agree with the NTSB accident investigation, and the vast majority of the Safety Board’s recommendations have been completed. We’ve improved our processes a lot,” he told the UAS public forum.