Thursday, December 4, 2014
NVIS: Continued Airworthiness and Training
|This NVIS-compatible panel is made by Rogerson Kratos. It is installed aboard a Bell 429 that was on display at the Airborne Law Enforcement Assoc. conference in July, 2014. Photo by Ernie Stephens|
Night vision imaging systems (NVIS) can improve the safety of flying at night dramatically. But the enhanced safety can only be realized with proper implementation of the entire system, and not just the goggle appliance itself mounted on your helmet. This system includes, of course, the night vision goggles (NVGs), cockpit and external lighting modifications, instrumentation (i.e. radar altimeter), a trained crew, and finally, ongoing continued airworthiness and a recurrent NVG training program.
We’ve already discussed the technology that makes night vision possible and how it must be matched with a properly lit cockpit. This maximizes performance and keeps things legal at the same time. (See the August and October 2014 issues of Rotor & Wing.) To recap, displays must be readable during both daytime and night, without adversely affecting the function of the goggles. Displays lit with unfiltered incandescent or light-emitting diodes (LEDs) give off excess infrared (IR) energy, and can cause unwanted haloing and IR reflections in the canopy and cockpit instrumentation. The excess IR energy can also cause the goggles to gain down, limiting their ability to amplify the minimal light of the night sky. The solution is to apply filtering to the lighting so this excess IR energy is attenuated enough that it does not impede goggle performance while still allowing for day and night unaided viewing of the panel.
There are various styles and combinations to choose from when it comes to methods of cockpit lighting modifications, but essentially they can be grouped into one of two categories: external or internal. The choices made at the time of purchase will have an impact on your ongoing maintenance program, so research is a must. Each type of lighting has its pros and cons, and one must consider their aircraft model, the Supplemental Type Certificates (STCs) that may or may not exist for it, the nature of their mission, the quality of the filtered light that each lighting type provides, and what it will cost to purchase and maintain the system.
Incandescent post lights have been around for decades and are an inexpensive lighting option. NVIS modification involves having proper filters installed over the bulbs. Due to their fragility, they tend to require more maintenance over time. They are the least robust form of lighting, and while they may meet the required specification, they may not provide the most uniform lighting coverage.
LEDs have stormed the lighting market in every application, to include NVIS. As post lights, they are more durable than incandescent bulbs, and should last for the lifetime of your aircraft. But they can be expensive to install and to repair, should they malfunction. Like all post lighting, they are a light source external to the instruments and would require that the lighting internal to the instruments be disabled when they are in use during NVG flight.
A variation to post lighting is the bezel ring light. It adds an edge-lit panel overlay to your existing instrument panel. It does not require additional wiring, as it taps into an existing aircraft power source. Possible concerns are added thickness, which may cause readability issues, and additional weight. It can cause excessive aircraft downtime should one light become inoperative, and require an entire rework if you change your panel configuration.
The least intrusive way to make your aircraft lighting compatible with NVGs would be through the installation of external filters over each instrument. They do not change your existing aircraft wiring or lighting system. But some variations of filters can make daytime viewing of the instruments difficult due to their dark color. The overall experience will depend on how good your existing lighting is to begin with.
The most expensive route to take, but arguably the most comprehensive method, would be the internal modification of all your instrument lighting. With this method, the instruments are opened and OEM light bulbs are replaced with the filtered variety.
|Photo courtesy Night Flight Concepts|
Here is where your due diligence in thoroughly reading and understanding the STC will pay off. Consider these examples: 1) If the purchased STC utilizes internal modification of the original instrument lighting, then you become bound to the holder of the STC to make any/all repairs on those instruments to remain legal. If the STC holder cannot make the repair, they will round-trip it to a repair station that can, but then they must put their stamp of approval on it before you get it back. Other STCs that achieve NVG compatibility without modifying the instrument itself (post, bezel, or external filter overlay) can allow instrument maintenance to be done at any OEM-approved repair shop, avoiding this potential hassle and associated costs. 2) If your fleet contains multiple aircraft with the same make and model of NVG compatible instrument, yet they are installed under two different varieties of NVIS STC, you cannot swap that instrument from one aircraft in as a replacement for the other or you will be out of compliance. 3) If you even decide to swap the locations of radios that live in the same radio stack of a single aircraft for any reason, you will be out of compliance until the holder of the lighting STC issues you a new print of the panel to match. All of these scenarios can result in unforeseen cost – in both time and money – to the operator. Do your homework and know what you are buying.
Effect on Operators
Depending on the section of the Federal Aviation Regulations (FARs) you operate under, the depth of compliance you must demonstrate will vary. If you operate under FAR Part 135, take heed, because your NVIS must be included on your Master Minimum Equipment List (MMEL). This implies that should your NVIS contain inoperative equipment, you are unable to fly – even unaided. To remedy this, you must request that FAA Policy Letter 127 be added to your MMEL, which allows for 10 days of flying with inoperable NVIS lighting provided there is no interference with the pilot’s ability to normally view the instruments. Beyond this, as a 135 operator, you are required to provide the FAA with a formalized, approved, continued maintenance program (per FAA Order 8900.1 Volume 6, Chapter 11, Section 22, and OpSpec D093) that will show and ensure compliance with the ICAs of the lighting STC, and the manufacturer’s requirements for maintenance of the NVG appliances. This includes a 180-day inspection of the goggle appliances themselves. Additionally, any alterations that could affect NVIS must be documented, and all maintenance documents must match those mentioned in OpSpec D093.
As a Part 91 operator, you are not required to produce a formalized maintenance program in order to be legal when flying with NVGs. But that doesn’t make you exempt from your requirement to follow FAR part 91.205 related to having proper instrumentation and lighting, and part 91.417 related to maintenance records. Compliance must come in the form of logbook entries documenting all required airworthiness inspections of the NVIS according to the STC ICAs, as well as recording the 180-day goggle inspections.
Night vision goggle training under Part 135 will need to be accomplished according to an approved training/recurrent training program specific to your operation, and further detailed in FAA Order 8900.1 Volume 4, Chapter 7, Section 4.
Consult order 8900.1 for particulars, but basic transition to NVG operation in an aircraft in which you are already proficient requires five hours of NVG ground training and a minimum of five hours of flight training. Ongoing proficiency, as taken straight from Order 8900.1, is achieved as follows:
In order for a pilot to act as a pilot in command (PIC) using NVGs while carrying passengers, the pilot must have performed and documented within the preceding 90 days three HNVGOs (helicopter night vision goggle operations) as the sole manipulator of the controls during the period that begins one hour after sunset and ends one hour before sunrise. These HNVGOs must be performed in the same category, class, and, if a type rating is required, type of aircraft in which HNVGOs will be performed. Each HNVGO must include, at a minimum, the tasks listed by the OpSpec A050. If a pilot has not performed and documented these tasks, the pilot will be allowed an additional 90 days to perform and document them but will not be allowed to carry passengers using NVGs during that time. If the pilot has still not performed and documented these tasks during those additional follow-on 90 days, then the pilot will be required to pass an NVG proficiency check in order to act as a PIC using NVGs.
OpSpec A050 defines what constitutes “helicopter night vision goggle operations” (HNVGO) and outlines additional NVG requirements, restrictions, and limitations. It should also be pointed out that there are differences between the requirements as listed in Order 8900.1, and the pilot currency requirements of FAR Part 61.57. As it is written, Part 61.57 is more restrictive in its requirement of every two calendar months to be current, as opposed to the 90 days listed in Order 8900.1. Operators need to clarify this discrepancy with the principle operations inspector (POI) in charge of approving their program, but erring on the side of safety is never wrong. In all cases, currency flights must be logged and reviewed.
Without the need for an approved training program, Part 91 operators are bound to the certification requirements outlined in FAR Part 61. Part 61.195 explains the qualifications necessary of your instructor pilots, while Parts 61.31 and 61.57 defines the requirements of ongoing currency in verbiage similar to 8900.1 listed above.
|This Bell 407 belonging to the King County (Washington) Sheriff’s Office is equipped with an NVG-compatible instrument layout made by Aero Dynamix. Photo by Ernie Stephens|
Of all the NVIS operational issues, the vast majority are due to unfamiliarity with the rules which cause the NVIS to go out of compliance in one area or another. The de facto resource will be your local FSDO and vendors of NVIS, such as Aero Dynamix, Aviation Specialties Unlimited, Rebtech, and others. They are all staffed by personnel with a wealth of night vision goggle knowledge, and are usually more than happy to answer any questions or concerns. Most of the vendors offer comprehensive flight and maintenance training programs in addition to NVIS STCs. With all of these resources available, it’s never been easier to take flight in the dark of night.