As Ally Pally says, NVG's need some light to work.. .The light limits, for peace time, are about 2 millilux. This is about the amount of light coming from the sky on a clear night with no moon. A quarter moon gives about 7mlux. If there is no moon and the sky is overcast then there is obviously less light.

Over European type populated areas, this is not such a great problem as the light from houses, streetlights etc is reflected from the clouds(especially low cloud), and artificially boosts the light levels.

However, in remote areas, away from any domestic lighting and with an overcast sky it is VERY dark and you literally cannot see your hand in front of your face! NVGs just do not work in these situations.

Some of the more specialised US helos are equipped with FLIR(Forward Looking Infra Red). As these "see" minute changes in temperature, it's possible to fly using them where it's too dark for goggles. I think some may also have terrain following radar as well.

Unfortunately, we can't afford fancy stuff like that. <img src="mad.gif" border="0">

[ 24 February 2002: Message edited by: MightyGem ]</p>

Possibly the reason is the aircraft arnt NVG compatable. . .That is the cockpit and other aircraft lighting has to be modified so as to take out all white light.. .The slightest pinpoint of white light can severly effect the gogles..you can imagine unmodified annuciator lights or others lights comming on can effectively blind you.. .It's a major job to get airctaft NVG compatable.

Doogs <img src="smile.gif" border="0">

Av8R,. .I think you will find that the internal lighting of all RAF SH aircraft has been NVG compatible for some time now.

VfrPb,. .NVG only amplify existing lighting, as already stated (imagine them working a bit like a hearing aid. If there is no sound, then there is nothing to amplify into audible sound). Once in the mountains, the only light is from above rather than from all around as in more populated areas. If there is cloud cover and no moon then there is unlikely to be enough light to allow the gogs to do their stuff. The theoretical minimum light levels are great to bear in mind but the only effective way to assess the light levels is to put the gogs on and see if they work. Unfortunately this can put a crew at risk, and I can tell you from experience that there is nothing more frightening than when you lose visual reference on goggles at a critical moment. Aircraft can use IR searchlights for low and slow stuff but not for cruise flight. However, anyone with an IR gunsight can see the light source...

The FLIR kit isn't affected by low light levels as it works by converting heat into visible light.

I don't know anything specific about this incident but during the Indonesian conflict in the 60s in Borneo, a RAF single Pioneer pilot ran out of duty hours on his way back to Labuan and landed at a deserted airstrip and spent the night in his aircraft, no radio call to anyone. At 5 am I was invited to search for him and about 8 am, I heard his radio call for clearance to enter CTA. On asking why he spent the night in the bush, he stated war or no war, he could not exceed his duty hours!!. .PS I was not in the RAF!! <img src="eek.gif" border="0">[/LIST]<img src="rolleyes.gif" border="0"> <img src="rolleyes.gif" border="0">

Vfrpilotpb; where did you read about this originally?

This was well reported in the papers and on the radio.

Good morning , from the rainswept, quagmire called Lancashire, . .Harpooner,. .As Mighty Gem pointed out it was in many newspapers , I think I saw it in the "Times", but it was only a very small item , more of a attention grabber than the normal sort of Times reporting.. .I was under the impression that NVG would work in Zero lighting, but thanks to the ocean of knowledge that the Ppruners have I now know a little more.. .Thank you all.

My Regards. .Peter B :)

I know nothing of the origin of the post but, an observation, If I were comming from a training area of very few very tall mountains into an area such as Afganistan, with very tall mountains and very dark shadows (the shadow is an area of less light than the minimal you are flying in), I would be very hesitant to commit folks to flying in that environment with out lots of train-up time.

Have no idea if this was the case. Just an obsrvation.

Mighty and VFR; I seem to have missed such news recently as my floating grey hotel was out of range of the paperboy!

The truth of the matter is exactly as gem stated (light levels at Zero) you can practice in any environment you choose but faced with flight anywhere in black velvet bag conditions it is best to skip the odd job - least you end up with a belly full of sand, and no one will thank you for that.

Hello there, I saw this post, thought I would reply. As posted earlier, a good reason a NVG flight could not be made in a particular aircraft would be the cockpit not NVG compatable. As stated earlier would be the presence of white light. But red light is deffinatly worse with blue/green lighting prefered. And the NVG's are passive, they need some ambiant light in order to function. In absence of sufficient light a "pink" light is usually incorporated. The light is just a IR filter that is attached to the searchlight (ie UH60) and turns the passive system to active so the use is normally not considered "stealthy". . As for FLIR, dry/cool atmosphere yields the best results. Humidity seems to adversly affects thier performance.. . j

Hi think you will find tandemrotor's comments the most pertinent.

fyi the peacetime limit is 1 millilux. however i reckon allcrews who have operated will agree that there is no real definitive way of stating whether it is 1 millilux or less/more. in reality you lift and fly to the limits of you and your crew and if someone is not comfortable he will say so. lack of sufficient ambient light may have been a reason, but the RAF crews in theatre will be v exp in v low-light conditions and it would have to be practically nil for them to have aborted.

same with CDP and whilst it exists and is used in the RAF it is cited by others as an example of lack of flexibility. far from it, it is a system which is ideal for peacetime and durting ops is taken account of in the planning and if unexpected ops are anticipated, then that will form part of the pre-op planning to ensure the potential commitments can be met.

nvg helicopter
 

if you have NVG compatible helicopter,you must have special lights on helicopters(possition lights), some helos even have one's on rotor blades,so they are seen thrugh NVG glasses.

Didn't see the clip; however it's quite common.

Rock dust blown up by rotor blades may cause minor sparking as it interacts with the metal leading edge protection strips. This causes light which is amplified by the NVGs. At worst it can appear as a halo effect; not good as it makes the aircraft a clear target in the military sense.

We get the same effect to a lesser degree when landing at airfields where there is lose rock dust, our aircraft has titanium blade protection strips and the sparks are white and very visible without NVGs. I believe it is the granite used in many concrete mixes that causes the brightest sparking effect. Even though we don't operate our aircraft into dusty sites very often (UK mud instead), our leading edge strips are rough to the touch, caused by the resulting erosion.

The effect is astounding, and is even visible with the naked eye at times.

I believe the effect is piezoelectric, that is the production of energy when a crystal is squeezed or distorted. The sand paticles hit the blade and glow fiercely in the rebound. I don't think the metal on the blade is an important part of the equaton.

Try this: get into a very dark environment let your eyes dark adapt fully (20 minutes). Then hit a sugar cube with a hammer and watch the glow.

We ran a long thread on this a few months back.

Nick,

I tried that. Don't think I waited for my eyes to fully adjust. hit my thumb instead. No spark of light, but the air turned blue.

Colin :D

Nick,

Not discounting your piezo-electrics but I think the metal type of the leading edge protection does play a part in the effect. Perhaps there are two different effects / causes.

The S-76, the S-70 Blackhawk and the CH-53 all do it, especially in dusty conditions. Certainly on the S-76 you can see little white sparks bouncing off the underside of the blades with the naked eye even ground taxying at an airport but other types I have flown with stainless steel protection as opposed to titanium (flown into the same locations) don't seem to do it, even when shrouded in dust.

BTW, Have you seen the titanium studded knee-sliders that motorcyclists use to deliberately throw up a shower of white sparks on corners? Oh, sorry, you don't have corners in Florida do you? :D ;)

Anyone know what type of LE protection the Chinook has?

Can't wait till dark, got my 14lb lump hammer and box of cubes at the ready, not to forget the steel / titanium toecaps and eye protection. :eek:

Nothing to do with this really, but open carefully a self-seal envelope in the dark and the adhesive surfaces glow blue.

Snag is you can't read the letter:confused:

wintogreen lifesavers have a more noticeable effect, but thats because there are other things going on. Same idea initially, quickly break a crystal and you have an uneven distribution of charge. Electrons jump to equal the charge and in doing so emit a light whose color depends on the type of crystal, blue for sugar i think. Didn't know it was called piezoelectrics...learn something every day.

I saw the clip on cnn of a chinook landing through nvg...was very surprised how noticeable the effect was in Afghanistan. Seen it many times before both with and without NVGs, never that noticeable.

Unrelated: Best thing to see with NVG are comets. Hale Bopp light up the sky. That one with a Japanese name about a month ago wasn't visible unaided...awesome with goggles.

I've done quite a few jump seat trips in Chinooks while wearing gogs (NVGs) and the effect is very impressive (if a little disconcerting when you first become aware of it!)

Shy torque,

I learn each time I log onto pprune!

There are differences between rotor blades, but the Sikorsky family uses nickel strips, as does Boeing on their family, at least according to the web sites I found about 5 minutes ago. The Bell 430 uses nickel caps on its steel strips, so the actual impact surface is nickel, I think. Perhaps it is that way for the other newer design Bell baldes.

I must say that I don't know if the spark response different than other helos, I hope ppruners can help out. We can guess that CH-47, Bell 430 and H-60's are the same. Are they in reality?


Anyone with specific knowledge of different spark response (under goggles and not), with different helo types under the same operating environment?