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Flat light


Roondog
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Flat light happens when the light is diffused by clouds overhead and there is no longer a single piont light source(sun) which creates a shadowless surface environment. It excaserbates uniform surface illusions such as unbroken desert, water, snowy terrain and even grasslands or forests which manifests in a lack of depth perception. In my experience snowy terrain and calm water are the hardest to gauge under flat light conditions. Hope this answers your question. If you've ever been snow skiing on an overcast day you'll know what it is.

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Flat light happens when the light is diffused by clouds overhead and there is no longer a single piont light source(sun) which creates a shadowless surface environment. If you've ever been snow skiing on an overcast day you'll know what it is.

 

been there, done that, can make for a scary downhill run if you don't realize what it is :o

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Flat light (whiteout) conditions can be insidious and overwhelming, even after you KNOW they exist and have claimed TWO aircraft ahead of you! :o

 

You may find these reports interesting... and instructive! :blink: Note that these aircraft were NOT in obscuring phenomena (fog or clouds), but under an evenly lit overcast, over featureless terrain, with experienced crews.

 

ANC99FA139

 

ANC99LA140

 

ANC99LA141

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Flat light (whiteout) conditions can be insidious and overwhelming, even after you KNOW they exist and have claimed TWO aircraft ahead of you! :o

 

You may find these reports interesting... and instructive! :blink: Note that these aircraft were NOT in obscuring phenomena (fog or clouds), but under an evenly lit overcast, over featureless terrain, with experienced crews.

 

ANC99FA139

 

ANC99LA140

 

ANC99LA141

 

Wow that is really interesting, thx for posting

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wow, interesting stuff, the helicopter pilot is always learning!! I only read the first NTSB report, ANC99FA139, but was shocked to learn the pilot had no training on emergency instrument usage, epecially in his environment. But back to flat light, is this something that once you're in it, it can be identified before you end up plowing into the ground?

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wow, interesting stuff, the helicopter pilot is always learning!! I only read the first NTSB report, ANC99FA139, but was shocked to learn the pilot had no training on emergency instrument usage, epecially in his environment. But back to flat light, is this something that once you're in it, it can be identified before you end up plowing into the ground?

 

If you have no depth perception it is virtually impossible to judge your height over the water, snow, sand or ice. I have had a bit of experience in this doing long-line operations in the mountains as well as over water in snow and fog. A good mountain flying instuctor will show you the dangers of such a situation.

 

The best advice I can give is to use a high contrast lense such as the Serengeti sunglasses or other high quality blue light blocker. The prescription ones are expensive, but worth every dime.

 

CDN RH

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Here's my limited flat light advice:

 

- If it's flat light try not to fly into.

- If you must land in flat light pick something to have reference for landing (i.e. something sticking out of the snow: a rock, top of a tree, flagging, person...) and remember the reference may disappear if there is a lot of powder. If there is no reference try to make one.

- Use your landing light to see when you are getting close to the snow.

- Remember that the spot you are landing at may not be flat so do not commit until you know your skids are flat on solid ice/snow. Also, your main/tail rotor may not have clearance above the snow so watch out!

- Always have an out (an area to go around to: a valley with bare rocks, trees, even a cliff that has less snow but you can see it in the flat light...) if you start losing your reference. Flat light will give you vertigo and you can flip upside down without knowing it or slowly run into a gentle rise in the snow which can cause you to flip over.

- Look directly out your side of the helicopter. Open the window (if you have one) so there is no glass between you and the ground. Less distortion this way and you can see more definition.

- Like CA Rotorhead said, get a good pair of high contrast glasses. Even cheap shooting glasses are better than nothing.

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Radar Alt would seem to be a real cheap thing to have rather than 3 down

 

I agree. I think they added those in the new ones since the big 3. I was gone during that time but I've seen the changes they have put forth.

 

One of the problems I see with radar alt is it only shows you your height above the ground directly below you. If you are heading at a slowly rising terrain it will be too late. I have a friend who got a 300 foot alert at night and he did a cyclic/collective yank. We later flew the same route during the day and realized he just missed the mountain by a few feet. Radar altimeters are good but they still have problems. Best thing is not to get into flat light conditions! No landings or take off unless there is good reference!

 

We are having the capstone systems installed in ours this year so that should show better terrain clearance.

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Flat light (whiteout) conditions can be insidious and overwhelming, even after you KNOW they exist and have claimed TWO aircraft ahead of you! :o

 

You may find these reports interesting... and instructive! :blink: Note that these aircraft were NOT in obscuring phenomena (fog or clouds), but under an evenly lit overcast, over featureless terrain, with experienced crews.

 

ANC99FA139

 

ANC99LA140

 

ANC99LA141

 

This is just my opinion but I don't think they were very "experienced crews". There were many other factors that could have lead to those accidents. One of them was inexperience with the type of terrain and the young "get it done" mentality. I do not fault the pilots completely and see there could have been other factors to blame. The human need to try and save your friend is very strong but sometimes the best way to save someone is not to go in after them if the conditions are not ideal.

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Note that these aircraft were NOT in obscuring phenomena (fog or clouds), but under an evenly lit overcast, over featureless terrain, with experienced crews.
Another factor was that none of the pilots had an instrument rating or any (recent) training in IMC flying (the aircraft were all equipped with the instruments required for 135 flight - DG, attitude indicator, ball). This company now lists an instrument rating as a hiring criteria.

 

Note - an instrument rating may not have prevented these accidents, but as evidenced by the changed hiring criteria, it can't hurt.

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Another factor was that none of the pilots had an instrument rating or any (recent) training in IMC flying (the aircraft were all equipped with the instruments required for 135 flight - DG, attitude indicator, ball). This company now lists an instrument rating as a hiring criteria.

 

Note - an instrument rating may not have prevented these accidents, but as evidenced by the changed hiring criteria, it can't hurt.

 

Something to consider when looking at an accident that did not happen to you is that it is human nature to try and believe that an accident cannot happen to you. If I put each of you in the exact same scenario without proper training, most of you would crash given the same flat light conditions. The pilot may have been the one who crashed but the training may have been the real problem.

 

Imagine this: your friend just crashed on a snow covered glacier. You have spent months in the same housing as this friend. You have gone to dinners, had drinks, BBQ's... with this person. Now, that person is possibly injured on a mountain and you are the only one there to save your friend. You take off to search for that friend. You see your friend's crash site looking up into a white valley (flat light). You believe you can fly in there and get your friend. After all you can see the crash site. Do you continue? The answer is NO.

 

The answer sounds easy but it is very difficult without proper training in judgement and regional specific flight training. The urge to save a friend is very hard to overcome. The real cause of the crash might possibly have been the inability to use judgement; not the lack of instrument rating... but what do I know.

 

As a side note: that company does not require instrument ratings. Most tour/utility helicopter operators still don't require the instrument ticket.

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NTSB Identification: ANC06LA025

Nonscheduled 14 CFR Part 135: Air Taxi & Commuter

Accident occurred Sunday, March 12, 2006 in Ilimana, AK

Aircraft: Robinson R44, registration: N7528Z

Injuries: 2 Uninjured.

 

This is preliminary information, subject to change, and may contain errors. Any errors in this report will be corrected when the final report has been completed.

 

On March 12, 2006, about 1355 Alaska standard time, a skid-equipped Robinson R44 helicopter, N7528Z, sustained substantial damage after colliding with snow-covered terrain while maneuvering to land, about 10 miles west of Iliamna, Alaska. The helicopter was being operated as a visual flight rules (VFR) on-demand charter flight by Pollux Aviation, Wasilla, Alaska, under Title 14, CFR Part 135, when the accident occurred. The certificated commercial pilot and the sole passenger were not injured. Instrument meteorological conditions prevailed at the accident site. Visual meteorological conditions prevailed at the time of departure, and company flight following procedures were in effect. The flight originated about 1320, from the Iliamna Airport, Iliamna, and was en route to a remote, off-airport site.

 

During a telephone conversation with the National Transportation Safety Board (NTSB) investigator-in-charge (IIC), on March 12, the pilot said that after departing from the Iliamna Airport, he flew west, en route to a remote drill site. According to the pilot, as the flight proceeded, low fog, reduced visibility, and flat light conditions reduced his ability to discern a horizon. He said that the visibility deteriorated to about 1 or 2 miles, and he was unable to discern any topographic features on the surface of the flat, featureless, snow-covered terrain, and he elected to make a precautionary landing and wait for better visibility. After remaining on the ground for about 10 minutes, he decided to fly towards his destination site. He said that just after takeoff, as the helicopter moved forward, flat light conditions, and worsening fog, contributed to his inability to recognize any topographical features. He reported that while he was attempting to establish a stable hover, and erroneously believing that the helicopter was not moving, the helicopter's right skid struck the snow-covered terrain. The helicopter subsequently rolled to the right, and the main rotor blades struck the ground. As the main rotor blades struck the ground, the helicopter continued to roll onto its right side. The helicopter sustained substantial damage to the fuselage, tail boom assembly, and the main and tail rotor drive systems.

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