Upcoming developments could pave the way for helicopters to maneuver through even the most obstructive environmental obstacles.
Just in case you missed it, the future of navigation is here and ready to go to work. Once we understand what it can do for us. So before we can figure out where we are going, it makes sense to see where we’ve been and how we got there.
Legacy navigation, a term of endearment for how we navigated from place to place, was predicated on tracking and homing courses from ground-based radio stations. You went where it took you, not necessarily where you wanted to go. Hence the navigation was linear, not trajectory-based, and two dimensional, lacking a vertical path. This necessitated the “Dive & Drive” of descending on an instrument approach. Regretfully, this created the opportunity for controlled flight into terrain (CFIT), leading to catastrophic accidents involving aircraft large and small.
The legacy instrument flight rules (IFR) system was created for fixed-wing aircraft, and the helicopter pilot was further challenged by the inherent restrictions, inflexibilities and limited access IFR provides.
Before a durable system can be created to serve the vertical-flight community, the architects need to understand the limitations of helicopters and challenges encountered while operating in the legacy system. Arguably, the legacy system did not exploit the unique capabilities of the helicopter, being the only conveyance that can travel from point-to-point without the need for roadways, waterways or runways. My own experiences with copter IFR involved significant delays in obtaining an IFR release, wasting valuable fuel and ultimately receiving a clearance that would not resemble what was originally filed or required.
After finally taking off, and receiving vectors two states away, excitement built as the originally planned fuel margins evaporated, moving on to plan B. Ever present is the threat of icing – blade, structural and engine inlet. Clearly the legacy system assisted in creating the very risk and opportunities that IFR flight should avoid.
Further constraining copter IFR is the lack of a single-engine IFR certification program due to Part 27 requirements, which call for the same avionics certification standards for single-engine helicopters that are required for jets in the transport category.
According to industry advocates, among single-engine Part 27 helicopters worldwide from 2001 through 2013, there were:
Single-engine fixed-wing aircraft are not subjected to the same impediments as single-engine helicopters since they are required to follow Part 23 standards. This cultivates several questions. Why the difference? Is this requirement serving the industry or the flying public? Does it facilitate an acceptable level of safety? Do single-engine fixed-wing aircraft sustain unacceptable rates of failure on their components since they are not “protected” by Part 27?
In my experience, operating a single-engine turboprop almost exclusively single-pilot IFR, equipped with contemporary avionics, has demonstrated their robustness and reliability. Their capability has been equivalent to my experiences operating Part 25-certificated transport-category jets. If the requirements outstrip the benefits and the core issues are not being addressed, why continue down this path?
GPS changed all of that. At first, GPS was about the freedom to navigate directly between two points. This paved the way for instrument approaches with lateral guidance — standard instrument departure (SID) and standard terminal arrival route (STAR) — and vertical navigation.
Raw GPS has an accuracy of 10 meters. If the raw signal can be corrected for its local inaccuracies and position errors, the accuracy can be improved to 1 to 2 meters, and with the application of a flight analysis system (FAS) data block, vertical guidance.
Vertical guidance can also be achieved with barometric altimetry or GPS augmentation, known familiarly in the form of the FAA’s wide-area augmentation system (WAAS). There are two methods for delivering GPS augmentation: space-based augmentation (SBAS) and ground-based augmentation (GBAS). WAAS supports localizer performance (LP) and localizer performance with vertical (LPV) instrument approaches.
In the spectrum of helicopter IFR, hospitals and operators have a choice in selecting a service provider to develop, certify and maintain instrument flight procedures. Our goal at Hughes Aerospace has been to adapt the technology we’ve implemented in the air carrier community into the vertical-flight community, wherever it makes sense to do so. We have worked with the FAA over the past several years to examine the benefits of GPS and WAAS. To that end, we’ve been involved in serving the helicopter industry with instrument flight procedures (IFP), built by certificated and experienced terminal instrument procedures (TERPS) engineers, using industry-standard software tools and FAA public criteria.
Proponents are often confused between instrument procedures characterized as special or public procedures and the criteria that were used to develop the instrument procedures as proprietary or public. The vast majority of helicopter IFPs are characterized as special. Depending on your service provider, they can be developed and maintained to either proprietary or public criteria.
When IFPs are developed and maintained to public criteria, you can be assured that they are not restricted to a sole service provider and will be kept updated to the most current and relevant criteria.
Operators can also be confused as to what constitutes IFP maintenance. There are four elements of their maintenance:
As an FAA-authorized service provider, Hughes Aerospace possesses several letters of authorization, allowing it to perform heliport evaluations, IFP validation, as well as certification to develop and maintain IFPs. Hughes is one of two service providers that the FAA has authorized to develop and maintain Part 97 public instrument procedures as well as specials.
Helicopter IFPs typically consist of lateral navigation approaches (LNAV). They are depicted with a minimum descent altitude (MDA) and typically constructed with approach minimums around 450 to 600 feet and 1 square mile of visibility. Using WAAS, we can create instrument approaches with much lower minimums.
We recently developed the first helicopter localizer performance instrument approach, which has lower minimums than LNAV due to the superior accuracy (containment) of WAAS. Many contemporary avionics are capable of providing LNAV+V or LP+V instrument approaches. When you observe a +V, the avionics are providing LNAV with advisory vertical guidance (typically a 3-degree flight path angle, or FPA). This pseudo angle is extremely helpful in providing a stabilized approach, but bear in mind this is not based on a TERPS vertical surface. Oftentimes when you see an LNAV/LP+V procedure, it can be an indication of a possible obstruction that prevented the implementation of an approach with vertical guidance.
Localizer performance with vertical guidance, or LPV, is identical to a precision ILS instrument approach, featuring a DH or decision altitude with minimums as low as 250 feet and 3/4 square miles visibility. We can develop these instrument approaches with a variable geometric path or FPA beyond the fixed-wing standard of 3 degrees. Several contemporary autopilot systems will support FPAs of 7 degrees, allowing increased mitigation of terrain and obstacles.
En route connectivity is provided by helicopter routes, and until recently, helicopters were left using low-altitude “Victor Airways” or TK routes, which are extended transitions of instrument approaches. We have developed these routes independent of the approaches that can be line-selected in the flight management system (FMS). These routes are positioned to more favorably use airspace and mitigate terrain.
Another new element of navigation is the advent of the electronic flight bag (EFB). It supports a paperless cockpit, organizing charts, approach plates and manuals into a simple electronic repository. To better support EFB customers, we developed a digital, color-charting product that includes geo-referenced terrain contouring. Geo-referencing transforms the electronic chart, allowing the GPS feed from the EFB to provide own-ship display on the approach chart. This is a significant improvement in safety, providing the pilot with enhanced situational awareness while navigating the approach. Some EFBs that support automatic dependent surveillance-broadast (ADS-B) can provide weather and traffic overlays on a geo-referenced chart.
In the near future, required navigation performance based on WAAS will further enhance our opportunity to provide improved containment and utilization of airspace for helicopter navigation. This will provide routes and transitions closer to terrain and lower altitudes. Another element of this is the use of radius-to-fix (RF)-segment coding. The RF supports both precise lateral and vertical navigation, also allowing aircraft to safely maneuver around terrain and airspace constraints.
Today, we can go from a pile of dirt to a certificated heliport with advanced instrument procedures in less than a year, in support of safe, all-weather day/night operations.