Pilot's Guide to Avionics 2012-2013 - 29

PILOT’S GUIDE

Current certifications for operational credit require the integration of the sensor and existing aircraft flight data on a HUD. The certified systems are approved for use under FAR 91.175, which provides an alternative means via EFVS to operate during low-visibility conditions that equates to the human eye. Today, using IR cameras, only two EVS sensor manufacturers are approved for credit when displayed on a HUD. Appropriately qualified EFVS operators may conduct WAAS/LPV, ILS or NP approaches and then complete Category I lower landings in poor-visibility conditions today. More than 1,200 aircraft are currently outfitted with either Elbit/Kollsman or CMC EFVS systems able to take advantage of various operational credits. Many more aircraft operate in the NAS with stand-alone EVS and SVS configurations. It has taken nearly 70 years to break the limit of 200-foot landing minimums for Category I or less, achieved by our old friend ILS. While Category II and III operations are possible for some, they require additional aircraft equipage, aircraft, crew and ground infrastructure recertification plus maintenance. Another positive is that CV operations are not limited to certain airports or runways. As with WAAS LPV, the limit is the straight-in approach, aircraft equipage and operational certification, not the ground infrastructure. While the WAAS LPV can bring you down to ILS like DH/ DA limits, a CVS certified as EFVS can transition the aircraft to land during low visibility. RNP approaches may later provide for the same transition. NextGen implementation includes CV-based operational improvements mapped out for time-based implementation. The NextGen Implementation Plan 2012 (NGIP 2012) is available on the FAA’s NextGen website. Appendix B maps the various NextGen operational improvements referencing surface, approach and takeoff, all during low visibility. SOME IMPORTANT POINTS TO UNDERSTAND EVS sensors on their own cannot be certified for operational credit but are very useful for situational awareness. There is only one type of sensor currently approved for use with the HUD and together certified as EFVS. This sensor uses cooled InSb technology. This type of technology with a sensitivity level as low as 3mK provides sufficient sensitivity to perform approved low-visibility operations, while able to “see” the approach lights. Uncooled sensors operating in a different section of the IR band cannot see approach lights and have a lower detection level, typically at or above 35mK. An example of an uncooled camera is the Kollsman GAViS using a vanadium-oxide sensor operating between 8-14 μm wavelength and with a sensitivity of 35mk. Meanwhile, its cooled counterpart, the Kollsman EVS-II, is standard on many Gulfstream business jets and FedEx wide-body aircraft. This IR camera operates between 1-5 μm with a published sensitivity of 5mk. Note the sensitivity ratio is not linear, so the EVS-II is significantly more sensitive than its uncooled GAViS counterpart. While you may read and hear of plans for “heads-down” or “SVS on HUD heads-up” operational credit during lowvisibility conditions, today, only the aforementioned cooled IR cameras displayed on a heads-up display have achieved such credit. Significant effort is underway, however, to eventually receive credit for “SVS on HUD” as found in the recently delivered Bombardier Global 5000 Rockwell Fusion cockpit. Effort by Honeywell is also underway for similar credit using a combination of EVS and SVS on a HDD. Recent tests by NASA and others have provided interesting results. In Europe (EASA), the term EVS applies to systems used for both situational awareness and operational approval. The operational approval, though similar, is different in Europe as it is RVR and not DH based. The U.S. is moving in a similar direction with 1,000-foot RVR credit set to replace or supplement the 100-foot DH/DA credit based on the specific aircraft operational category. In an approach light environment needed for EFVS operations, IR-based EVS cannot see LEDs. The FAA, supported by ongoing SAE G20 committee effort, has two IR-LED prototype solutions about to begin evaluation for introduction into the MALSR environment estimated from 2014. Currently, no MALSR (or ALSF) may migrate to LEDs until a resolution has been found and approved by the FAA. From a general aviation perspective as opposed to business and commercial aircraft, EFVS is not much help today because of size and cost limitations. This is primarily because of the approved sensor technology and the need for a heads up display. Even the new Rockwell HGS 3500 set to enter the upcoming Fusion cockpit markets will most likely be limited to business jet size aircraft. Smaller and lighter low-cost EVS sensors by L-3, Lexavia, Max-Viz, Kollsman and CMC are perfect for situational awareness, but to reinforce the point, have no relation whatsoever to the higher-cost sensors used for EFVS. There are many high-quality STCs available for these uncooled EVS stand-alone systems. Meanwhile, CV in its varied forms will continue to migrate into smaller cockpits providing significant enhancement, even if the systems are not yet to be certified for operational credit during low-visibility conditions. q

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Pilot's Guide to Avionics 2012-2013

Table of Contents for the Digital Edition of Pilot's Guide to Avionics 2012-2013