Synthetic Vision for HEMS
Joined: May 2002
Aviation Qualifications: ATP+Mil
Posts: 18,633
Likes: 1,072
From: Downeast
Folks,
There is reality and there is the Rule.
The Rule is quite specific. It clearly states " Visual Surface Light Reference". It does not say "Celestial Light Reference" or "Natural Light Reference".
You can try to twist it all you want....but the truth of the matter remains and that is you must have some house lights, street lights, car headlights or some sort of man made light below you to facilitate your control of the helicopter. That means with "lights" you do not necessarily have to have a "Horizion" in the common definition.
Yes, it is true on a Clear, Bright Moon lit Night, you can fly quite safely over terrain that provides a good horizon. Example....ever flown over snow covered ground, with a Full Moon and bright star light? Seen the sparkling of the Moon Light off the frozen rivers and streams?
Change that to offshore....completely different.
Flying over wooden mountains like we have on the East Coast...on a Moonless but clear night with bright starlight and no surface lights....you have a false horizon as the horizon line will vary with the height of the ridges in front of you...some higher than others which can be a problem as the visible horizon is not the same as that shown on the ADI.
Add an Overcast, a densely forested un-inhabited or very sparsely inhabited area....now how does that affect your visual cues?
We have the Rule and we have commonsense. Obey the Rule in this matter and your chances of having an IIMC encounter are much less.
The same FAA under Part 91 does not impose that surface light requirement.
It limits the requirements to just "Weather Minimums" which to me seems like setting a trap.
My room name here came from having worked at a Large Oil Company in a very sandy place south of Kuwait that had Bell 212's with no SAS doing night flights offshore. As anyone who has flown in that part of the World knows...it gets very Hazy and Overcast, and at night despite there being the required Visibility as required by FAR 91....there is nothing to see for long periods of time, no visible horizon, no lights, nothing but your own big white eyes shining back at you from the windscreen. That is IMC to me....anytime I must control the Helicopter by sole reference to the flight instruments.....but under FAR 91 as interpreted by the Operator....was VFR (based upon weather alone). I was so impressed with that kind of thinking...and the reason the 212's had not SAS which is another story for another time, I picked SASLESS for use here at pprune.
There is reality and there is the Rule.
The Rule is quite specific. It clearly states " Visual Surface Light Reference". It does not say "Celestial Light Reference" or "Natural Light Reference".
You can try to twist it all you want....but the truth of the matter remains and that is you must have some house lights, street lights, car headlights or some sort of man made light below you to facilitate your control of the helicopter. That means with "lights" you do not necessarily have to have a "Horizion" in the common definition.
Yes, it is true on a Clear, Bright Moon lit Night, you can fly quite safely over terrain that provides a good horizon. Example....ever flown over snow covered ground, with a Full Moon and bright star light? Seen the sparkling of the Moon Light off the frozen rivers and streams?
Change that to offshore....completely different.
Flying over wooden mountains like we have on the East Coast...on a Moonless but clear night with bright starlight and no surface lights....you have a false horizon as the horizon line will vary with the height of the ridges in front of you...some higher than others which can be a problem as the visible horizon is not the same as that shown on the ADI.
Add an Overcast, a densely forested un-inhabited or very sparsely inhabited area....now how does that affect your visual cues?
We have the Rule and we have commonsense. Obey the Rule in this matter and your chances of having an IIMC encounter are much less.
The same FAA under Part 91 does not impose that surface light requirement.
It limits the requirements to just "Weather Minimums" which to me seems like setting a trap.
My room name here came from having worked at a Large Oil Company in a very sandy place south of Kuwait that had Bell 212's with no SAS doing night flights offshore. As anyone who has flown in that part of the World knows...it gets very Hazy and Overcast, and at night despite there being the required Visibility as required by FAR 91....there is nothing to see for long periods of time, no visible horizon, no lights, nothing but your own big white eyes shining back at you from the windscreen. That is IMC to me....anytime I must control the Helicopter by sole reference to the flight instruments.....but under FAR 91 as interpreted by the Operator....was VFR (based upon weather alone). I was so impressed with that kind of thinking...and the reason the 212's had not SAS which is another story for another time, I picked SASLESS for use here at pprune.
Last edited by SASless; 5th March 2013 at 11:54.
"Just a pilot"
Joined: May 2001
Posts: 633
Likes: 8
From: Jefferson GA USA
"No person may operate a helicopter under VFR unless that person has visual surface reference or, at night, visual surface light reference, sufficient to safely control the helicopter."
A single point of artificial illumination does not ensure ensure adequate surface reference to safely control the helicopter. Therefore, that phrase in the rule does not prevent night IIMC.
The base requirement is adequate surface reference, and a visual light reference must be on the surface, within field of view. It doesn't say "source of illumination" although that is how it's commonly interpreted and applied by my employer. I am also required ceremonial garb (uniforms) and incantations (standardized verbal communications).
The 'surface light reference' is a regulatory phrasing like 'congested area' in that the legal definition is not invoked without separate cause.
A single point of artificial illumination does not ensure ensure adequate surface reference to safely control the helicopter. Therefore, that phrase in the rule does not prevent night IIMC.
The base requirement is adequate surface reference, and a visual light reference must be on the surface, within field of view. It doesn't say "source of illumination" although that is how it's commonly interpreted and applied by my employer. I am also required ceremonial garb (uniforms) and incantations (standardized verbal communications).
The 'surface light reference' is a regulatory phrasing like 'congested area' in that the legal definition is not invoked without separate cause.
