Peter wrote:
Is any value less than 400m proposed to be practically achievable for GA? LVO approval is out of the question.
The NPA which is the very subject of this thread proposes a reduction to 150 m without the need for any LVO approvals. Also, if RVR is not available then it would be up to the pilot to determine if there is sufficient visibility — i.e. no more converted meteorological visibility.
Several of the arguments put forth in this NPA are rather revolutionary. E.g. that it doesn’t make sense that visibility requirements for IFR approaches are higher than for (S)VFR approaches, so the proposed new visibility requirements are never higher than 1500 m, while in the present part-NCO they can be as high as 5000 m.
(Except for approach category C and D aircraft which also makes sense as 1500 m viz for (S)VFR is only applicable with IAS ≤ 140 kt.)
Interesting.
One had stuff like that with e.g. the UK IMC Rating requiring 1800m vis for takeoff or landing, when you could fly VFR in 1500m 
Don‘t agree – that‘s actually one of the few points where imho the authors of the NPA show that they have little practical experience in small aircraft IFR flying.
One of the challenges with IFR approaches especially in small aircraft with single pilot cockpit, bumpy rides, etc. is the change from the instrument to the visual part of the approach. I‘ve seen so many recreational IFR pilots that undershoot the minimums because they look up out of the front screen trying to identify the runnway and before they actually can make a go/nogo decision they are below minimums.
A VFR pilot doesn‘t has to make this change.
Therefore in my eyes it does make sense that in some situations the IFR minimus are slightly higher than the VFR minimums to Accomodate for the instrument/visual change. Or, like one of my former instructors put it: „The 300m between 1800 und 1500 is the distance the aircraft travels while you look out of the windows to make sure vis is not below 1500m“
Malibuflyer wrote:
Don‘t agree – that‘s actually one of the few points where imho the authors of the NPA show that they have little practical experience in small aircraft IFR flying.
I think you are completely wrong here. But at least one of the authors (if there are more than one) is active on EuroGA so he can answer for himself.
The 1.5km does make a lot of sense for landing as well as terrain/traffic as it goes along aircraft speed, vertical performance…
Putting these aside for takeoff you can argue that all you need is 0m (practically 10m 
) or runway lenght for those more conservative, after all you are not going to fly beyond the threshold bellow 50ft ?
How will you judge when rwy distance remaining is sufficient to abort takeoff ? The commercial multi-engine crew have V-speeds, but what do we have ?
Ibra wrote:
Putting these aside for takeoff you can argue that all you need is 0m (practically 10m )
How can you maintain lateral control visually during takeoff with 10 m RVR?
I know that you can do a 0/0 takeoff using the DI for course guidance (and I’ve done it myself under the hood when training for the IR) but the consequence of any mistake would be an almost certain runway excursion at high speed.
airways wrote:
How will you judge when rwy distance remaining is sufficient to abort takeoff ?
If you say you need 400m to takeoff and clear 50ft obstacles then isn’t that all you need as visibility?
Asumming you can clearly identity that 400m (hard to do without horizon)
Now eventualities:
- if you wanna factor an extra 200m to stop it is the same VMC or IMC but high likely you will lose control in IMC
- if you can’t make stopping distance on ground roll then outcome is the same IMC or VMC
- engine failure after takeoff bellow 300ft will be dead ahead anyway on ASI (high likely outcome is better if you “just fly” without seeing anything)
- engine failure above 300ft, I agree that is where VMC starts to matter
Airborne_Again wrote:
How can you maintain lateral control visually during takeoff with 10 m RVR?
Not serious about that one but surely doable on:
- low nose tricycles on DI/SV instrument and wide airline runways
- high nose tail-wheels with big wood pannel and tight GA runways
Malibuflyer wrote:
One of the challenges with IFR approaches especially in small aircraft with single pilot cockpit, bumpy rides, etc. is the change from the instrument to the visual part of the approach. I‘ve seen so many recreational IFR pilots that undershoot the minimums because they look up out of the front screen trying to identify the runnway and before they actually can make a go/nogo decision they are below minimums.
A VFR pilot doesn‘t has to make this change.Therefore in my eyes it does make sense that in some situations the IFR minimus are slightly higher than the VFR minimums to Accomodate for the instrument/visual change. Or, like one of my former instructors put it: „The 300m between 1800 und 1500 is the distance the aircraft travels while you look out of the windows to make sure vis is not below 1500m“
An interesting point, and I don’t disagree that there are challenges associated with the IFR to VFR transition. However, the key issue is the choice between VFR and IFR in particular conditions.
Consider an aerodrome with no approach lights and a straight in GNSS LNAV approach with a 400 ft OCH with FAT offset by 20 degrees. In a visibility of 1500 m, is the safer arrival likely to be an IFR arrival on the GNSS approach, or a VFR join downwind followed by a visual circuit? If you, like me, believe the former is safer, why would you assign a minimum RVR of 1800 m to the IFR arrival (according to GM3 NCO.OP.110) but allow a VFR arrival in 1500 m?
Note that if the approach is not offset, there is already, in the existing rule, a 1500 m cut off on the RVR required for Cat A and B is already applied. So the change affects only unusual cases.
