Rotor & Wing NVG Article- Army Minimums
 

The most recent Rotor & Wing issue has an article on NVG's and NVG training. The article mentions that in extremely low light environments, the US Army has the following lunar illumination requirements: 23% disc illumination and at least 30 degrees above the horizon.

The article mentioned this in contrast to civilian HEMS operations, which typically make no mention of the moon at all, when setting limitations for NVG use.

My program utilizes NVG's in areas that have no terrestrial illumination whatsoever, and also over water at night.

Does anyone know where I can find a copy of the Army's weather and terrestrial/celestial illumination requirements for NVG use?

Thanks.

23% and 30 degrees has been around for a long time. It does not restrict you from flying in less light levels, but required you to have operational "pink light" installed on the acft. This was a requirement for Army training and operations which are tactical low altitude operations.
Civil HEMS does not perform tactial NVG covert operations. You probably have enroute minimum altitude of 500 feet AGL or higher and can only go below that after performing your high recon of the scene. Totally different environments. You also will have 2 or 3 unfiltered lights to help illumintate the area and if you feel you don't have good enough vision with the NVG, de-goggle and land unaided. NVG are a tool to make your job safer, enroute and at the scene, if you feel that unaided is safer, take the NVG off and proceed unaided. The really nice thing about NVG is you can flip them up and down as you wish and need. You are not limited to only aided or unaided. Get in the air and see which mode is safest for the conditions.
For your overwater oeprations at night, the NVG won't provide you much help unless oil rigs are not lit. I would recommend night overwater be primarily via instruments with altitude alerter set and resume NVG when approaching the shoreline.

The Army does not restrict you from flying NVGs for any illumination conditions currently... IIRC it would only elevate your Risk Assesment level and require a briefing from a higher ranking commander to OK you to fly (a practice done on every flight). That being said, I've flown NVGs on many, many zero-illum nights in featureless environments in both training and actual operations, and found that while it is a huge help to have the goggles, the missions we performed would have been able to be performed unaided, with the goggles simply allowing a greater safety margin and more efficiency of flight (sans of course the blacked-out combat type missions). Goggles aren't as much a tool to allow you to fly when you could not, but rather they allow you to fly safer when you would have already been flying anyways.

Besides, when you turn even the dimmest landing light on at low level, you create your own moon... and then some.

-Mike

Thanks for clarifying that.

I don't agree with the idea that a landing light can be used to illuminate the way while enroute, however....if that was what you were getting at. In my experience, while flying in an area of high humidity over the ocean at night with no moon, the last thing I want to do is turn on an exterior light.

Besides, the landing light does nothing to help you create a visual horizon where the horizon has been lost due to dark water and no moon.... and I do not have IFR to back me up.

I think that the NVG's are a great tool, but for night overwater operations, they are not capable of at producing a horizon 100% of the time.

And there are no off-shore stuctures where I am.:suspect:

NVGs over water are a bit of a problem especially when out in zero light. Unfortunately, you are left with the IFR / NVG blend to keep things safe. Many times over water you may be left with a single target point of reference such as a single distant vessel which is essentially a single point of light on the goggs. This can create gyrosomatic illusions leading to the leans. I know that much of the time the RN will rely on IFR procedures for transit and winching ops.

In fact I've experienced problems in daytime VFR SAR scenarios with reasonable visibility, solid overcast, calm water and no horizon, and little IFR experience to back me up. The only thing that prevented me losing references was back to basics, trust the instruments and find a land reference as soon as possible. These scenarios are very similar to the NVG op, but you have fewer cues and a bigger head scan to complete with the NVGs. Nothing else for it! Get the IFR training and if you can, engage and manage your autopilot at the first possible opportunity.

It's really important to realise that if there is no light there, and you cannot provide your own illumination, you may as well be IFR, for all of the use the NVGs are over featureless terrain or water. Any limitations that the army provides are primarily designed for desert operations, good meteorological visibility and low humidity with few ground references and a high liklihood of recirculation. They are not designed for over water ops.

You don't say what you do with the NVGs over water... or is it so cool you can't talk about it?

Nothing will give you that horizon 100% of the time if the weather is bad - just like during the day.

You say you don't have an IFR option, does that mean you are not instrument trained or don't have an IFR equipped/capable aircraft or have other constraints that prevent you flying on instruments?

We operate low level over the sea day and night in all weathers but we have the advantage of a very good radar and radar operator which will allow us to keep clear of vessels/windfarms/land. We also have a very good AP and fly 2 pilot.

If you are flying overwater at night on goggles without a horizon because the weather is so bad then you are effectively in actual conditions. I trust you have a 4 axis autopilot with a rad alt hold and audio warner - plus a second pilot.

No- the aircraft is single pilot VFR only (nicely equipped, and with radar, but no autopilot).

I am not saying that the weather is bad- generally, it is good- it's just very dark without a moon, most of the time.

Plan B is to turn around before encountering IMC- be that a loss of horizon, or clouds/low viz. Trouble is, it is sometimes darker behind you than in front of you.

What are we doing? Just moving people from Point A to Point B- nothing spectacularly interesting...other than this being a fairly uncommon operation.

Good luck, Velvet. :sad:

Very dark nights flying goggles can at times be IMC while flying VFR (no clouds but no horizon either). NVG flight is much more on the instruments than day flight. I'd be very careful flying in those conditions single pilot/ single person with access to the controls.

Velvet - I can only presume that you are doing something that is either covert, illegal or both since single pilot, VFR flight in an unstabilised helicopter over water on NVG with fare paying passengers is unlikely to be condoned by any Aviation Authority in the world. Is it single engined as well?

Well, nothing covert here- and it's a twin. We are never more than 45 miles from a land mass, but that land mass is rock, and mostly uninhabited (no light).

If anyone can provide me with a reference that states that under FAA Part 135, single pilot, twin engine, VFR, NVG, no autopilot, over water, at night, with fare paying passengers is illegal- I would really like to see that.

Dont know about FAR, but in the UK, rule 20 of the Rules of the Air prohibits VFR flight at night.

I really think that VFR ops overwater at night in an aircraft without automatic height hold acting through a fast-acting input to the collective channel of a 4-axis autopilot is asking for trouble. And using NVG is not a way to convert night to day. The RAF operates a variety of helicopters with an assortment of APs using NVG. All of them, without exception, require two crew in the cockpit for such an operation. That includes the SAR crews who can choose any combination of NVG and white light that gets the job done.

Sven

In the USA, the majority of night helicopter operations are VFR, and are unaided, as well...

Wen you say that VFR is not permitted at night in the UK- I assume that you mean that the aircraft and the pilot must be IFR, not that it must be an IFR operation at night, correct? Otherwise, scene work at night would be out of the question...:confused:

I've done a fair amount of night offshore flying, and IMO NVGs are not the best way to do it. Enroute, it's IFR, if not IMC, and the landing is usually to a very highly-lit platform, where the goggles are not necessary or don't work well. If you can't fly in IMC, then you shouldn't be flying offshore at night, NVG or not, because it will be IMC, sooner or later.

It is interesting that this has not been regulated but the FAA.

The Nov 1991 "Rotorcraft Night Vision Goggle Evaluation" paper that Hawley, Anoll and Green had prepared for the FAA before the implementation of NVG's in the civilian sector did not have much to say about the use of NVG's in off-shore operations, other than they considered off-shore to be an "extremely difficult operating environment".

They did, however, "recommended that the FAA investigate offshore use of NVG's as part of their continuing efforts".

Here is the link to this ancient, but interesting read: http://www.dtic.mil/cgi-bin/GetTRDoc...c=GetTRDoc.pdf

I suspect the FAA had no interest in evaluating the use of NVG's off-shore, and so they just dropped the ball right there...

I have been researching this for months, but I have been unable to find any tangible performance criteria that has been published regarding the use of NVG's off-shore.

Most training criteria that I have been able to get my hands on, is either silent on the issue of overwater use, or merely states that water is "not a high contrast" surface.

I know that military and SAR have been going out there for years under these conditions, but I have not come across any of their findings....perhaps they do not wish to share?

So is civilian use of NVG permitted in the US? If so why don't HEMS use it?

The lack of detail regarding location and employer give me reason to think you know that what you are doing is either wrong or foolish - what about a duty of care for your passengers.

As for sharing, I have already told you how we operate in that environment and what equipment we have - it is exactly as Gomer Pylot says, because you will end up IMC at some point we are equipped and trained to cope with it rather than having a plan B of 'turn around'.

There are a lot of HEMS operations flying NVH in the US. I have done over 100 hours this year. The new changes to Part 61and 91 actually make is a normal operation now, asof 20 Oct 2009. There are qualification requirements, currency requirements, equipment requirements ect... It also does not discriminate fixed vs rotor nor by type of flying. If you have a Cessna 152 and or an R22 and get an authorized NVG modification done, and aquire the proper TSO NVG, you can fly NVG here with the proper training.

Crab,

My comment regarding 'sharing' was not directed at you- it was directed at those agencies/municipalities/organizations/military/etc.. who have conducted technical performance testing of NVG's off-shore and who have documented their testing, but have not made their findings available to the civilian sector, which I believe is in great need of some education as to the limitations of these devices, and how they should not be utilized.

I very much appreciate your comments regarding how NVG's are utilized by you on the job.

Most reputable HEMS operators in the US are now using the the latest generation- Anvis 9 NVG's. It really isn't all that long ago that most HEMS operators did not even require an instrument rating to fly HEMS at night! Now, HEMS pilots all have instrument ratings, but they fly VFR aircraft and only get to practice IIMC procedures and instrument flight once every year when they do their annual recurrent training.

I would say that presently, close to 90% of all HEMS in the US is probably conducted single pilot in VFR helicopters, with no autopilots, and plenty of them still do not have NVG's or TAWS- so they are conducting off-airport operations at night, sometimes in very dark places, completely unaided. Do they like it? No. But that is the job.

My inquiry here was initiated in response to what is being asked of the pilots; the FAA approved the use of these night vision devices with little or no restrictions or limitations.... nothing concrete in the Part 135 Operations Specifications that would limit their use off-shore, which happens to be my primary operating environment.

Velvet - sorry if I appeared too critical but I am honestly shocked that the FAA have allowed this to happen, it seems utterly irresponsible not to impose some regulations or limits to prevent people frightening or killing themselves.

The Met Office in UK produce a light level prediction programme which might be useful but I suspect such a thing already exists within the US. Unfortunatley, although it makes allowances for differing levels of cloud cover, it can't make a go/nogo decision based on weather, it purely deals with starlight and moonlight.

Crab,

I could not agree more- a lack of FAA regulation has left civilian operators a loophole where they can go much too far with the goggles.

Civilians have begun to use NVG's to go places aided, where they cannot go unaided- instead of using them as they were intended, to enhance safety by providing better visual cues during VFR operations. I think that maybe some operators are beginning to lean on NVG's too heavily to get the job done. It is inevitable, of course....

A simple revision could cure that- maybe something like, "aided flight is not permitted in a VFR aircraft when meteorological conditions exist that would prevent a pilot from proceeding unaided..."

I have not seen a pre-flight tool that can assist a pilot in predicting light levels- I know that I would find it very useful in preliminary preflight planning- as a first step to consider before further contemplating and planning an offshore NVG flight.