|Today’s rotorcraft antennas serve many functions but the most important and most common are communications or navigation. Photo courtesy of Airbus Helicopters
Today’s rotorcraft antennas serve many functions, but the most important and perhaps most common are communications or navigation. There are several ways to accomplish this via transmission or reception of radio waves: VFR, IFR, ILS or GPS/wide area augmentation system (WAAS) GPS. Communication takes place over a number of frequencies based on the communication type. VHF is the most typical communication format for aircraft to tower, or aircraft to aircraft. FM and/or UHF frequencies are used for specialized communications such as police, fire, and search and rescue (SAR).
Like most aircraft, rotorcraft antennas must stand up to the rigors of typical airborne environments including temperature extremes, altitude, waterproofness, etc., but particular attention must be paid to vibration because all rotorcraft have intense vibration cycles and profiles. These profiles must be duplicated in the testing laboratory and the new antenna designs are subjected to them.
Don Jeckell, director of business development at Comant Industries in Fullerton, Calif., says Wi-Fi applications, such as ship-to-shore for instant downloads of flight data, are getting more common. “However, unless you are looking at Internet in the sky for Business Aviation (21 percent of the helicopter market), there may not be a foothold for this communication process until a – to-date unforeseen – shift in market or new product development occurs,” he says. “There will be users of broadband technology in the rotorcraft sector but not on a grand scale as we are currently are seeing on commercial airlines. When Ka-band becomes available on a wide scale it will be only a matter of time before it replaces many Ku-band systems because of its greater capabilities and wider bandwidth. If Ka systems (and their antennas) can be kept lightweight and small, they could find a place in the rotor market. This remains to be seen.”
A persistent problem with antennas and helicopters is the space required to mount them, or the lack thereof. There can be problems with orientation, location or especially with grounding. “Often the profile is more compact,” notes Mark Rose, an experienced pilot and manager of Alpine Lift Helicopters in Albany, Ore. “Top-mounted units use a bent whip [while] bottom-mounted units are ruggedized and compact to prevent ground/snow contact. When antennas are removed, all grounds should be cleaned and resealed.”
Not only do antennas take up room for mounting, but they typically cannot be closer than three feet from one another. Follow factory supplied installation instructions and be sure to refer to the FAA’s AC 43.13-2B for additional information.
|Cobham’s CI 295-300 search and rescue helicopter antenna allows for three main frequency coverages used in SAR and public service fitting into one radome. Photo courtesy of Cobham
One way to fix this issue is to combine antenna functions into one radome if possible, and Comant has done this. “Five to six years ago Comant perfected its ComDat multifunction line of antennas where VHF, GPS and or XM could be placed in one radome saving time, space and installation costs,” Jeckell explains. Comant is introducing a new line of antennas for police, fire, SAR and air ambulance helicopters that combine frequencies typically used in these endeavors into one radome; the CI 295 Series. “Again these antennas will save co-site space, making them easier and quicker to install,” he adds. “This saves money.”
Over the past decade, OEMs have put pressure on antenna manufacturers to design smaller and lighter products. Herefordshire, England-based HR Smith Group’s 13-150 series of antennas offers a significantly reduced visual profile with electrical performance comparable to passive antennas more than twice the size. These antennas are adaptable to multi-band frequency requirements with added UHF functionality already achieved within the same footprint.
|The L-3 SkyWatch collision avoidance system. Photo courtesy of L-3 Communications
New York City-based L-3 Communications’ SkyWatch collision avoidance system also has a single antenna design. “Most other collision avoidance systems require two antennas and the rotor system often creates a problem for that ‘diversity’ top and bottom configuration,” says Steve Henden, senior manager of communications at L-3. “Our single antenna is typically mounted on the belly of a helicopter, giving operators an unobstructed stream of traffic data.” This is important because rotorcraft antennas must be located where they will not interfere with the operation of the aircraft or other aircraft systems.
Cobham Aerospace Communications' VOR/LOC antenna is particularly designed for helicopter use and is generally fitted on the tail boom. It has a towel bar design and includes two radiating elements, each with integral coaxial cable interconnected to a BNC connector in order to provide a single RF output.
With respect to helicopter antenna damage, maintenance crews should always look for obvious signs of a bird strike or signs of an antenna being struck by ground equipment. Jeckell says that if a crew member determines that the antenna is not airworthy, it should be replaced. Rose believes they are a throwaway item, remaining molded and sealed most of the time.
Today’s rotorcraft repair shops have highly skilled and trained technicians, and large inventories to ensure quick turnaround time. Most offer some or all of the below services:
• Component repairs, overhaul, exchanges and maintenance
• Component rework and refurbishment capabilities
• Parts obsolescence management
• Non-destructive testing
• Molding and non-standard repairs
• Ground support equipment
• Instruments, avionics and indicators repairs and overhaul
• Hydraulic component repairs and overhaul
• Mechanical and electrical component repairs and overhaul
|Duncan Aviation performs functions tests on two avionics units. The smaller unit, an AA80 InterVOX, is for intercom systems. Photo courtesy of Duncan Aviation
Oliver Bienz, instrument repair services manager/senior technician at Canadian-based Maxcraft Avionics in Pitt Meadows, BC, says the most common instruments brought into his shop for repair include: tachometers, temp gages, engine monitors, warning and caution panels, altimeters, navigation, and various panel and remote gyros (both VG and DG).
Beinz feels that maintaining a high degree of expertise and increasing repair capabilities for older legacy analog instruments are some of the trends facing Maxcraft today, in addition to pricing. “Customers are still very cost conscious,” he says. As far as the challenges? “Turn times, parts cost escalation, technical publication currency regarding OEMs withholding current pubs and/or charging astronomical prices for revisions,” he responds.
At Maxcraft, Bienz relies on highly trained technicians to complete the many tasks of repairing and overhauling high-precision electro, mechanical rotorcraft components and instruments to manufacturer specifications. “Customer support throughout the process from estimate to follow-up communications on any parts delays to final delivery confirmation” is essential, he adds.
Lincoln, Neb.-based Duncan Aviation is best known for business jet service and support. However, over the past several years, the company has been increasing its capabilities on equipment that comes out of aircraft ranging from general aviation to heavy airliners, including helicopters. The most common rotorcraft units worked on in its repair shop are audio panels or audio mixers. “AA35, AA80 and AMS43 are a few examples, but we see a lot of different models,” observes Dustin Johnson, an ADF team leader at Duncan Aviation.
Like Maxcraft, Johnson sees the most common trend at Duncan to be the request for faster turn times. “This is something we work very hard to achieve and as a result, we are constantly evaluating our processes and looking for ways to turn units more efficiently without cutting corners,” he says. “Customers can schedule a unit for an aircraft on ground (AOG), letting us know the deadline by which they need the unit. We do all we can to prioritize these requests and ensure that we meet the dates promised.”
One way Duncan Aviation has reduced turn times is through repetition. The more the repair shops works on a unit, the more it becomes familiar with its common failures and the more efficient the repair technicians get with the unit. “We have developed excellent efficiency and expertise on all of the units we have capabilities for right now,” says Johnson. “Once we see consistency in part failures, we can then justify ordering bulk inventory of those parts and keep them in-house so we do not have to delay things by ordering parts and waiting for them to be shipped to us.”
While rotorcraft repair shops realize and strive toward shorter turn times for customers, one of the biggest challenges hindering this is the increased difficulty faced in obtaining parts for some of the older units. Most are resourceful and have several channels they can utilize to find these traceable parts.
Another issue rotorcraft repair shops (and their end users) sometimes face is the increase in part prices or required minimum parts orders to a point where a unit is deemed BER (Beyond Economical Repair). “We can often use our contacts and unconventional channels to find ways around it,” Johnson says. “For example, we keep a large inventory of parts and we always look for the best and least expensive options for our customers. We will then present them with all options and let them decide what they would like to do.”
It is via this effective and thorough communication that repair shops are exceeding their customers’ expectations and gaining their trust. Johnson stresses providing options to customers in a very timely manner is crucial. “We do not assume we know what the customer wants because we just don’t know the customer’s exact circumstances,” he says. “We believe it is best to present them with all options.” It’s through this successful customer communication and channel management, along with a staff of highly trained rotorcraft repair technicians, that Richmond, BC-based Vector Aerospace recently delivered a fully refurbished AS332L-1 Super Puma helicopter to Rainier Heli-Lift.
Damaged during the tsunami which hit Japan in 2011, Vector Aerospace fully restored the AS332 to service by having its subsidiary Vector Aerospace Helicopter Services–North America perform a complete overhaul on the aircraft in November 2013.
Vector HS-NA performed a number of MRO operations on the Super Puma, including a complete airframe re-wire, a significant accomplishment requiring over 100 km of wire. A complete 7,500-hour airframe inspection and an internal and external paint job were also performed. Vector HS-NA also performed two main landing gear fitting changes with the assistance of specialists from Airbus Helicopters, who spent five weeks working with Vector technicians to help them achieve this complex repair within the tight project delivery schedule.