Monday, November 1, 2010
Helicopter SAR Technology Update
New equipment and technologies are helping minimize the “search” while maximizing the “rescue.”
Nov. 29, 1945 is a very special day in the history of helicopter search and rescue (SAR) services. If you’re not familiar with it you should be. That was the day, not far from the Sikorsky factory in Connecticut, on a bleak and wind-torn reef in Long Island Sound, when a Sikorsky R-5 performed the first civilian helicopter hoist rescue by lifting two men off of a heavily storm damaged oil barge. That stormy Thursday afternoon 65 years ago not only marked the realization of Mr. Sikorsky’s vision, but it forever changed the course of the role helicopters would play around the world.
Today, the role of a modern helicopter runs the gamut from aerial agriculture to counting whales, but by far the biggest impact these incredible machines have on humanity is saving lives. There’s really no telling how many people have been rescued over these past 65 years, but I can sure bet that whether afloat in the ocean or lost in the woods—the sweetest sound any of them heard was that of the approaching helicopter.
Technology to the Rescue
While today’s helicopters offer speed, range and load lifting capabilities that were just a dream of Igor Sikorsky, the parts of the SAR mission profile that have really exploded are the technologies that flight crews can use to locate and evacuate survivors faster than ever before. And in the SAR game, time is often the difference between a rescue and a recovery.
Emergency position indicator radio beacons (EPIRBs) are basically emergency locator transmitters (ELTs) for boats and ships. Category I EPIRBs are mounted somewhere on a boat or ship so that in the event of a sinking, the EPRIB is automatically released to float to the surface and begin its automatic distress transmission. Category II EPIRBs are manually activated. It’s up to the survivor to activate the signal.
While most modern EPIRBs transmit on both the analog 121.5 MHz and digital 406 MHz signals, there are a few older units that only transmit on 121.5. (More on what that means to SAR teams later on). Personal locator beacons (PLBs) are small, portable units that you wear and are manually activated. PLBs operate exclusively on the 406 MHz frequency, and many of them also have an automatic 121.4 MHz homing frequency transmitter. As an added safety feature many newer PLBs have a GPS capability that adds an embedded GPS positioning code to the 406 MHz distress signal, which gives searchers even more detailed information.
|The Rockwell Collins DF-430 Multi-Mission Direction Finder gives a “spot on” bearing to the beacon. Rockwell Collins.|
With a 121.5 MHz signal, it is covering about a 486-square-mile search area. With a 406 MHz ELT the area is cut down to around 10 square miles. The 406’s increased accuracy is due to its ability to pump out a full five-watt signal compared to the miniscule 0.2 to 0.5 watts coming from your 121.5 MHz ELT. That gets the geostationary satellites a much stronger signal, which leads to greater location accuracy. The Civil Air Patrol and U.S. Coast Guard are both installing 406 MHz direction finders. The Coast Guard has picked up 406 signals from as far away as 106 miles. That can be a huge difference in the success of the rescue.
Some beacons go one better. They have the capability of taking positions from a GPS and sending that spot-on location information as part of its encoded message.
406 ELT: Phone Home
With 406, there can still be a fair share of false alerts, but each beacon has a unique identification number so the SAR teams know who’s ELT, PLB or EPIRB is going off. How? Owners are required by FCC law to register every 406 emergency beacon. With 406 and your 24/7 contact information, one phone call to the owner or contact and the SAR teams will know if there is a problem before they dispatch search crews. If it’s a false alarm the owner can just switch it off and there are no SAR teams put at risk. If there is an emergency situation, often the distress beacon’s owner has left word as to where they were going and that can be a great benefit to the SAR specialists.
Of course, for that capability to be of any use you must first register your 406 ELT, EPIRB or PLB with NOAA. Owners can register 406 MHz enabled devices online at www.beaconregistration.noaa.gov or by calling 1-888-212-SAVE (7283).
A better distress beacon needs a better receiver. Specially designed to receive a 406 MHz distress beacon’s signals, Rockwell Collins’ DF-430 Multi-Mission Direction Finder picks up where the COSPAS-SARSAT satellites leave off. While the COSPAS-SARSAT satellites can give rescuers a pretty good idea where the distress signal is coming from, the DF-430 gives them a “spot on” bearing to the beacon.
Designed to receive a variety of emergency beacon signals including 121.5 MHz, 243 MHz, digital 406 MHz channels as well as ARGOS, the DF-430 targets in on the identification information found in the COSPAS-SARSAT distress messages transmitted by digital ELTs, EPRBs and PLBs at ranges up to 116 nm.
When integrated over the Mil-Std-1552B and ARINC 429 busses, the DF-430 can provide the distress beacon’s lat/long along with its unique identifier to the search aircraft. The flight crew simply enters those coordinates into the flight management system (FMS) and flies directly to the signal’s location. To expand the unit’s capabilities, the DF-430’s embedded synthesized receiver detects and enables bearing determination on any transmission type, including beacon modulation, AM and PM/FM signals over the corresponding frequency range.
|Rockwell Collins DF-430. Rockwell Collins|
The AeroComputers UC-5100 mission management system is in use worldwide by a variety of civil, government and military SAR providers. While the unit offers a wide array of advanced features and capabilities, the UC-1500 has two capabilities that are especially helpful in aiding SAR operations—ViewSync and “breadcrumbs.”
With ViewSync, the flight crew can aim the aircraft’s onboard camera at any location on the ground and the system will display the lat/long/elevation coordinates of that spot on the mapping system. This capability is especially helpful when the helicopter or aircraft can see the survivors but cannot land. By recording the exact location, the flight crew can send the precise location information to surface rescue teams who can quickly locate the victims.
The detailed location information is also very beneficial for post-flight evaluations. Searchers can look at the photo imagery from the aircraft’s camera in greater detail and, because the exact location of the image is available, areas of interest can be quickly identified and relocated. In a major disaster like flooding, the ViewSync can use the UC-5100’s built in mapping and targeting databases to locate the position of streets or houses, even when they are totally covered by water. The UC-5100’s “breadcrumbs” function records the aircraft’s trail along the flight path. Because the feature is always on, all the operator has to do to make a spot of interest is to press a button on the system’s control keyboard. The breadcrumbs capability is especially useful when the SAR crew is en route to a location but flies over other ‘points-of-interest’ along the way. With the simple press of a button, those locations are automatically stored. If the aircraft is equipped with an onboard camera, the breadcrumb locations are used to automatically aim the camera at those locations.
One of the hardest things for a SAR pilot to do is to look for survivors while flying a tight, coordinated search pattern. Kaman Aerospace has come up with a solution. The SH-2G Super Seasprite multi-mission maritime helicopter features a “Coupled Navigation” mode that provides a capability for the crew to select a pre-programmed SAR pattern. To affect this capability, the aircraft mission software is coupled with the automatic flight control system (AFCS) so as to direct the aircraft along the defined flight path.
The operator can either select from pre-defined search patterns loaded in the system’s mission computer or they can create waypoints defining a non-standard search. After the SAR pattern is defined, it is displayed on one of four MFDs at the crew station. Once the helicopter has reached the point of interest, the pilot can engage the coupled navigation mode. When engaged, the mission computer provides steering cues to the AFCS, which directs the aircraft to the first and subsequent waypoints in the pattern.
The three automated SAR patterns available to the crew are ladder, expanding square, and sector. After selecting the desired pattern the operator is able to define specific parameters to tailor the search for the prevailing conditions (e.g., search sweep width, expected drift speed and direction). All patterns originate from an operator-selected reference point; usually the estimated position of the survivor in the water, disabled vessel, or other search object. The operator then can set the pattern orientation, track spacing, leg lengths and initial turn. Once coupled, the aircraft will continue to fly the selected pattern until the operator deactivates the navigation mode for the SAR pattern.
Kaman’s coupled navigation SAR option allows the crew to concentrate more intensely on visual scans and aircraft search sensors, and thereby increases their probability of detecting the search object.
AW’s Hover Trim
Helicopter rescue winch operations face some of the most demanding and dangerous situations a SAR team can experience. Not only is the pilot often challenged with maneuvering the helicopter in tight spaces while the winch operator gives them minute corrections to the aircraft’s position. The challenge of spot-on positioning for the hoist is even harder in larger helicopters due to the distance between the pilot and the winch operator’s location. AgustaWestland has come up with an ingenious aid on its AW101: the Hover Trim Controller.
The Hover Trim Controller is mounted on a small joystick at the winch operator’s location. It gives the operator limited control authority to “fly” the helicopter left/right/forward/aft to accurately position the rescue device near the survivor.
As people keep finding more creative ways to put themselves in dire positions, search and rescue providers are challenged to fly missions into increasingly dangerous situations. Two of the biggest problem areas are reduced visibility, caused by brownouts, fog, rain or whatever; and in-flight obstacles—towers, wires, structures, etc. While some technologies and vision aids including forward-looking infrared (FLIR), shortwave infrared image (SWIR) sensors, light detection and ranging (LIDAR), millimeter wave radar (MMWR) and others have given flight crews some much needed, they all have their drawbacks. Namely, the lack of sharp detail and accurate obstacle range and elevation information. These shortcomings often to what pilots are calling “blobology” images—formless color blobs displayed on the helicopter’s MFD. Flight crews know something is out there, but they’re just not sure what or where it is.
Lockheed Martin’s new-generation Degraded Visual Environment Correlation Tracking & Obstacle Recognition (DEVECTOR) could just be the light at the end of the tunnel. Currently undergoing active flight testing, DEVECTOR uses advanced 3-D synthetic vision technology spawned from a high-resolution digital terrain elevation data (DTED) database and hazard detection sensors to create synthetic images that help flight crews operate more safely in significantly degraded visual environments.
Used alone, or in combination with LIDAR and RADAR, this fused vision/sensor system will provide a huge leap forward for those operating aircraft in marginal environmental and weather conditions.