Landing credit is the holy grail of the avionics industry. For operators and manufacturers, lowering decision altitudes – or rendering them obsolete – is the true pay-off for a long and costly investment in synthetic and enhanced vision devices.
Honeywell believes it is close to receiving landing credit from the US Federal Aviation Administration (FAA), based on a new breakthrough in synthetic vision technology. Though the emphasis for nearly a decade has been on certificating enhanced flight visions systems, Honeywell found a simpler path to obtaining landing credit: software.
“We have a proof of concept set of flight tests put together that actually gets us through the decision heights that we want to get down to for a Category One landing,” says Bob Smith, chief technology officer at Honeywell Aerospace.
Honeywell has always steered an alternative path in flight visualisation technology. Lacking an in-house manufacturing capability for head-up displays (HUDs), all of the company’s systems are based on a head-down philosophy to piloting the aircraft in conditions where human eyesight is not enough.
“I’m very comfortable with having this technology,” Smith says, “because I believe the eventual state is we’re going to get into having a combined vision system. It’s a capability that is the next state, which actually goes and fuses data on to the synthetic vision.”
The company’s SmartView synthetic vision system (SVS) is already installed in Epic- and Apex-equipped cockpits. While improving the crews’ situational awareness by presenting a graphical representation of a terrain database, SmartView does not lower the minimum decision altitude – 200ft (61m) for an instrument landing system approach.
That means if the pilot can’t see the runway at the minimum decision height, an SVS-equipped aircraft cannot land.
Honeywell is now racing its rivals in the avionics industry to develop sensors to eventually replace human eyesight and abolish airport closures caused by poor visibility for good.
That technology is at least a few years away, and, in the meantime, Honeywell is offering a partial solution.
The SmartView SVS renders a graphical representation of terrain and obstacles, but it doesn’t by itself deliver a landing credit from the FAA or other regulator.
A sensor-based system could eventually allow pilots to land aircraft in blind conditions.
Until then, Honeywell has proposed to upgrade the SmartView SVS to allow the pilots to descend closer to the runway before deciding if a visual landing is possible. The system is called the SmartView Lower Minimums (SVLM).
“What we’re getting here with SVLM is landing credit,” Smith says. “Now we’re actually going to allow you – not only will it be a safety feature from the standpoint of situational awareness, now I’ve got the capability to get into airports I couldn’t get into otherwise.”
The SVLM relies on the localiser performance with vertical guidance (LPV) approach system. While highly accurate, the LPV is not perfect. It requires independent verification, which is currently performed by the eyesight of the pilot. In conditions where the pilot’s visibility is nil, the SVLM software takes over.
SVLM independently verifies the navigation accuracy of the LPV system through a clever adaptation of the onboard inertial reference system (IRS).
Honeywell has installed four, software-enabled monitors in the IRS. The monitors cross-check the LPV’s navigation signal. The software creates a runway data integrity monitor, a delta position monitor, an approach deviation monitor and an altitude monitor.
“I have different monitors that are trying to make sure and cross-check that what I am seeing there is accurate,” Smith says. “It’s doing that integrity monitoring of the system to make sure it’s very, very accurate. That way, I can claim that lower minima requirement.”
The landing credit Honeywell is seeking from the SVLM would lower the pilot’s decision altitude to 150ft on a Category 1 approach with a runway visual range (RVR) of 1,400ft.
Honeywell launched a series of demonstration flights last May using the company’s Dassault Falcon 900EX, with the onboard EASy II integrated avionics suite modified with the SVLM software.
The flights are part of a proof of concept demonstration for the FAA. The agency is expected to thoroughly review the technology and the results versus Honeywell’s claims. The goal is to launch a certification programme that leads to establishing the landing credit for all aircraft equipped with SVLM.
“We’re flying it right now,” Smith says. “It’s the first step of a certification path. We want to say, ‘Here it is, we’re ready to offer it’.”
Honeywell already has plans to roll out the capability on several fleets of aircraft operating its flagship Epic and Apex avionics suites. These include Gulfstream’s product range, the Dassault product range and the Embraer 170 and 190 regional jet family.
“We’re looking at places you can apply that but obviously you go with places that currently have synthetic vision systems today,” Smith
says. “So every place we have there we’re going to be looking at talking with those customers as to whether we’d go apply it on their platform. I would say in general every place that we have a synthetic vision offering you would expect us to take to SVLM.”
New aircraft programmes are a key focus, as Dassault unveils the Falcon 5X and Gulfstream prepares to release the secretive P42 programme. Meanwhile, Embraer has already selected the Honeywell Epic flightdeck for the next generation E-Jet family called the E2. “We’re hoping to put it on E2,” Smith says.
After Honeywell delivers SVLM, the next step is to move the technology forward with what the company calls a combined vision system (CVS), which is also known as an enhanced flight vision system.
“If you go to the next step and now you fuse in data,” Smith says, “so, in other words, you take some kind of sensor – generically an infrared sensor or a millimetre wave sensor – then I can actually fuse that data in.”
The technology is hoped to abolish minimum decision heights for ILS approaches, meaning the pilot can land the aircraft and roll to a stop solely depending on the sensor image overlaid on the synthetic vision display.
Honeywell began working on the technology several years ago, as the US Army searched for ways to help helicopter pilots in Afghanistan and Iraq cope with brown-out landings.
A programme called Sandblaster – backed by the Defense Advanced Research Projects Agency –allowed Honeywell to overlay a millimetre wave radar image onto a synthetic display.
“Effectively, it’s trying to in real-time process all the data that’s associated with what those radar reflections are and then correlating it to your known database of terrain and obstacles,” Smith says.
The difference between Honeywell’s approach on CVS and all other avionics players is the absence of the HUD – a decision the company defends reflexively.
“We believe that a head-down approach is the right one for the vast majority of applications and provides the most amount of benefit,” Smith says.
A head-up display and associated equipment, including a projector, is mounted to the primary structure in the nose of the aircraft. It may seem a relatively small addition, but, in Honeywell’s view, it’s anathema. Aircraft weight and balance are disproportionately effected on both ends of the pressure vessel, Smith says.
“It’s several hundred pounds,” he says. “From an aircraft integration standpoint, being able to integrate that into the aircraft adds complexity and weight in a place where they want complexity and weight.”
Last June, the FAA proposed a new rule to allow operators to use an enhanced flight vision system (EFVS) to land on a straight-in instrumented approach. Though the FAA specified an EFVS based on a HUD or an “equivalent display”, the language in the rule appeared to make Honeywell uncomfortable.
“The FAA is unnecessarily limiting the future systems that may be capable of meeting the performance-based criteria,” Chris Benich, Honeywell’s vice-president of aerospace regulatory affairs, wrote in a comment submitted to the FAA docket on 15 October.
For example, the company notes that some “advanced aircraft designs” that may appear in the future “may not have conventionally designed front windows”.
Honeywell’s airframe partner, Gulfstream, also added a note to the docket. Gulfstream has spent more than a decade working on a supersonic aircraft, accumulating a small library of patents.
“For advanced aircraft designs of a high speed nature,” Gulfstream wrote in a comment submitted on 15 October, “a significant potential exists with the reduction or limited use of the front window design. The FAA’s limiting of an equivalent display would prohibit the use of EFVS and CVS type technology with the current language.”