Turn Out the Lamps

White lamps are giving way to blue lasers as the light source for richer, full-colour simulation visual projectors, and motion cueing systems are being further refined for ever more demanding applications. Rick Adams reports on the technology evolution in front of and under the sim cab.

Mention the word ‘laser’ to a pilot, and he’s likely to become agitated and see green. Irresponsible pranksters who think shining a green laser light at the cockpit windows of a landing aircraft, sometimes temporarily blinding the pilots, have become a detested scourge of the aviation community.

Blue lasers, however, when encapsulated in one of the new laser-phosphor (LP) projectors now being used in flight simulators, are giving off a more pleasant glow for pilot training organizations. A primary advantage is the longer life of solid-state lasers, compared with the light-emitting diode (LED) lamps which have predominated in display systems in recent years. “With a laser-phosphor light engine, we get a much longer life in the 15- to 20,000-hour range, versus the lamps, which you’re replacing every 2,000 hours or so,” said Jon Hester, vice president, Visual Systems, for FlightSafety International.

FlightSafety claims that, in January, it was the first to achieve US Federal Aviation Administration (FAA) qualification for a flight simulator using a laser-phosphor projector, and has deployed multiple LP-equipped devices since.

Rockwell Collins spokesperson Alison Wright told CAT magazine the company “has fielded and certified several systems using JVC VS2300/2500 laser phosphor illuminated projectors. We have been delivering these projectors since Q2 CY15 and certified our first systems in Q3 2015.” Rockwell Collins also recently announced it will use LP technology in three new flight simulators for Turkish Airlines, a Boeing 737NG, Airbus A320 and A330.RSI is agnostic with regard to projection technologies, offering an array of options for its visual systems customers. Alasdair MacPherson, RSI managing director, Sales and Marketing, told CAT, “From its inception RSI has been totally agnostic with regard to projectors. We were the first to introduce an LCOS projector, and we were the first to introduce LED. We just stopped offering lamp-based LCOS and are transitioning to the laser phosphor. We still offer a DLP [digital light processing] LED projector. We constantly evaluate projectors. We have good relationships with the companies but we don’t commit to any so that if a new technology comes along, we’re able to evaluate it, test it against other standards, and deploy it readily.” MacPherson said RSI has provided new simulator and visual system upgrades to “all of the major simulator manufacturers” – CAE, FlightSafety, L3, Lockheed Martin, and Textron/TRU.

For the time being, CAE is sticking with LED technologies. “CAE actively monitors such developments and we will adapt our offerings over time based on the results of our evaluations,” said spokesperson Pascale Alpha. “This may include LED, laser, or laser phosphor as the illumination source, and DLP or LCoS [liquid crystal on silicon] for the imaging device – whatever we determine will allow us to offer visual systems with the best training value.”

Using a laser phosphor light source in conjunction with LCoS projection technology offers higher performance, according to FlightSafety’s Hester: “The contrast of the projectors is definitely higher, and the brightness is much more controllable.”

The longer life of the lasers should also mean greater consistency in simulator visual displays. “With lamps, every time you strike an arc, it’s a little bit different. You have to work to maintain consistent colors and brightness in an integrated multichannel display.” “In some ways,” Hester mused, “It’s like a step back because we’re using phosphor like we used to use in CRTs [cathode ray tubes], but instead of having an electron beam excited we have a laser beam exciting it.”

In fact, laser systems for simulation were first used in the early 1980s by Singer-Link for a US Army Cobra helicopter simulator. The laser image generator was a transition step between crude modelboards and digital imagery. In the 90s, Jenoptik (now part of Rheinmetall) and Evans & Sutherland (now part of Rockwell Collins) pioneered laser display technology, though at rather steep cost, so systems were restricted to military simulation applications.

The IlluminatiLaser phosphor illumination uses a blue laser diode as the light source instead of a high-intensity discharge (white light) lamp. The diode shines laser light onto a reflective aluminum disc, coated with yellow phosphor and rotating at high speed, creating yellow light. Blue laser light passes through an opening in the phosphor wheel. The projector then sends the yellow light through a colour wheel to generate red and green, while the blue laser light passes through a diffusion window. These red, green, and blue colours are then directed onto an imaging surface, which directs the light through a lens and onto the projection screen.

FlightSafety uses LP projectors from JVC’s Visual Systems Division. A year ago, JVC introduced its DLA-VS2500ZG and DLA-VS2300ZG “BLU-Escent” laser projectors, designed to meet both FAA Level D and International Civil Aviation Organization (ICAO) regulatory requirements. “The simulation and training industry has been eager to see projection solutions that offer exceptionable image quality with long life and a reasonable price point,” said Jack Faiman, JVC Senior vice president.

JVC says its BLU-Escent architecture features a reflective phosphor wheel rather than a transmissive one to reduce optical loss and increase luminance efficiency. The result is higher contrast, high brightness, and increased reliability. Lasers output light in a very narrow cone, and do so in a smaller emitting area compared with LEDs or lamps. The result is greater efficiency in delivering light and higher contrast due to less stray light.

Compared with conventional lamp projectors with a tilt-angle limitation, LP projectors can be installed at any orientation through 360-degrees, including vertically, which is ideal for helicopter simulators.

An added environmental bonus: there’s no mercury, as with lamps, eliminating disposal issues.

Sony has announced a new “Z-Phosphor” LP projector designed for simulation, visualisation and training: the VPL-GTZ280 with 5,000 lumens and native 4K (4096 x 2160) resolution. The VPL- GTZ280 will ship in the second quarter 2016. According to Sony, it will use “high-speed motion functions and new high-speed 4K 120Hz signal processing capability for 4K3D 60-Hertz left eye/right eye and reducing blur in fast-motion scenes, in addition to smear and transport delay reduction, infrared light output for night vision stimulation, and vibration resistance.”

Christie offers the DWU555-GS solid-state, single-chip DLP laser phosphor projectors, but for “entry-level” simulation applications. In February, Barco launched what it calls “the quietest laser phosphor projectors on the market,” producing fewer than 35 decibels; the single-chip DLP machines are targeted at the business/office and theatre markets.

Dermot Quinn, director of product development at Digital Projection, said simulation applications benefit from the solid-state reliability and predictability of laser phosphor technology. “I think laser phosphor is going to take market share because it can compete with the overall cost of ownership of existing lamp technology but with all of the benefits of solid-state.”

Resolution EvolutionThe next evolution in simulation displays may already be represented in your den: the “ultra high definition” television, also known as “4K” – not because the resolution is four times that of so-called “full HD” (1920 x 1080 pixels), though that’s a convenient way to think of it, but because the actual resolution is about 4000 pixels wide (in actuality, 3840 x 2160). By the year 2020, 4K TVs are expected to represent well over half of sales worldwide, and as consumer sales drive down production costs the technology becomes more affordable for civil simulation applications

FlightSafety is incorporating 4K resolution into the KC-46 tanker-transport flight simulator it is building for the US Air Force.

Full HD resolution equates to roughly two megapixels, which was a decent-quality mobile phone camera a couple generations back. 4K resolution is 8.29 megapixels, which may prove only a brief stepping-stone to 8K displays (7680 x 4320), or around 33.18 megapixels – 16 times the number of pixels and four times the spatial resolution of HD TV.

Rockwell Collins is planning to deliver “a new software baseline which will provide several technology and functionality improvements” in 2016, according to Wright. “The EP-8100 provides a growth path on a visual system level by supporting higher-resolution projectors and will also accommodate enhanced synthetic environment features. In addition, several image quality enhancements will be introduced to ensure Rockwell Collins continues to supply the highest-fidelity visual systems.”

Movers and ShakersOne emerging area of pilot training which is driving particular attention to flight simulator motion systems is upset recovery and prevention training (UPRT). A new FAA rule requiring UPRT becomes effective in March 2019 for airline pilots. The European Aviation Safety Agency (EASA) has issued a Notice of Proposed Amendment that would encompass not only air transport pilots but light aircraft, private, and commercial pilots as well. The expected compliance date for airline operators is May 2016 and April 2018 for others.

“Motion cueing is particularly critical to UPRT because, as an airplane approaches a stall, it tends to become less stable, hence harder to control. We know that humans rely on immediate feedback to stabilize themselves,” said Dr. Sunjoo K. Advani, president of The Netherlands-based International Development of Technology and Chairman of the International Committee for Aviation Training in Extended Envelopes (ICATEE).

“A stall in an airliner may present different cues depending on many factors – the type of airplane, the altitude, the configuration, turbulence, presence of icing, etc. In some cases, there may be ‘roll off’ as one wing stalls just before the other. In other cases, there may be a characteristic buffet cue, called ‘deterrent buffet,’ that shakes the airplane violently before the impending stall. Presenting these cues accurately is considered important, as in the past they seem to have distracted or misled pilots who applied the wrong control strategy. Regardless of the cues present, the primary task of the pilot is to immediately reduce the angle of attack and then apply the correct recovery procedures.”

Advani recommends that stall models include type-representative considerations and be tuned according to the aircraft they represent. “One challenge is finding subject matter experts who can perform that tuning, since there can be many factors that influence how the airplane behaves during these stalls and upsets.”

FlightSafety is the first manufacturer to field flight simulators which are FAA-qualified for UPRT, a Gulfstream G550 model in Savannah, Georgia, in June and more recently a GV trainer in Wilmington, Delaware. Dr. Nidal Sammur, FlightSafety’s director of Engineering, said, “We have to make sure that upset recovery maneuvers are performed within the limits of the motion system without introducing anomalies. The last thing you want to do is introduce negative cues.”

Sammur said the company has done considerable tuning of their second-generation electric motion system, including “a deeper dive” on ground reaction and aerodynamics models, as well as running the physics-based models at speeds as high as 800 Hz. “I believe the motion performance is now much superior than in the past. The basic equation of any moving object with simulation, whether linear or non-linear, is that the faster you do it the more accurate you are. But you cannot do it without quite a bit of talent and know-how to make sure it works in a simulation-based environment.”

Advani said today’s flight simulators can be used for 58% of the UPRT requirement (when combined with academic knowledge on upsets). Enhancements could boost that to 84%: feedback of the flight envelope to the instructor (to compensate for the lack of g-cueing in the simulator, for example), enhanced buffet representation, and the modelling of the aircraft behaviour as it approaches and exceeds the stall angle-of-attack.

“Instructor feedback should incorporate both the indication of the g-cueing taking place, in order to prevent over-stressing the airframe, and the validated training envelope (VTE). These are the boundaries within which the simulator envelope can be relied upon with varying degrees to represent the real aircraft’s behaviour,” said Advani.

The remaining 17% of UPRT training can be achieved in specialised devices or in aerobatic-capable aircraft: g-awareness, spatial disorientation, and high-amplitude motion cueing.

Helicopter simulator motion and vibration systems continue to be targets for innovation as well. On the first full flight simulator for Bell Helicopter’s 407GX, Frasca International uses 62-inch primary actuators plus a secondary TruCue vibration system, also with six degrees of freedom. However, the instructor station is isolated from the vibration system, reducing instructor fatigue.