PepperJo wrote:
If I read this correctly it would not allow to fly a VOR or NDB approach with the GPS (like in the US?). At least not if VOR/NDB are used in the final approach segment:
It does allow that so long as the conventional approach aid is monitored.
JasonC wrote:
It does allow that so long as the conventional approach aid is monitored.
Meaning you would need the VOR or ADF which defeats the purpose of substitution.
PepperJo wrote:
Meaning you would need the VOR or ADF which defeats the purpose of substitution.
If they are in the final approach segment in the US you also need an ADF. This will allow substitution in the missed for example. The US doesn’t allow complete substitution unless there is an overlay approach.
There is usefulness for all the RNAV approach where the missed approach is based on a NDB (a UK favorite) or to fly DME arc
Meaning you would need the VOR or ADF which defeats the purpose of substitution.
Exactly; it makes this worthless because if equipment carriage is required that’s what we have now, and “everybody” flies it using a GPS, and because the GPS is not officially used, it doesn’t have to comply with any requirements 
There is usefulness for all the RNAV approach where the missed approach is based on a NDB (a UK favorite) or to fly DME arc
That’s a fairly marginal case though, Europe-wide.
Does this mean that if you have a straight NDB approach, say LDLO or many other places, you still have to carry an ADF?
The change makes it consistent with the US approach to the subject.
In that case I struggle to see the use of it in Europe, unless Europe develops official overlay approaches, which is exceedingly unlikely due to the required resources.
Often, the “Threads possibly related to this one” links below a thread are worth a look, and here we have this one where much of this was done before
I found this a bit strange, in section 4.3.1 of the NPA:
It is notable that the difficulty of LVTO is likely to scale with the speed of the aircraft. A take-off in an RVR of 300 m in an aircraft with a 65-knot rotation speed might be compared to a take-off in an RVR of 600 m in an aircraft with a 130-knot rotation speed.
Isn’t take-off/rotation distance a quadratic function of speed, like landing distance (i.e. double the touch-down speed and we roughly quadruple the braking distance)?
Also, does anyone know where the proposed 150 m LVTO RVR came from? In touring aeroplanes with half-decent performance do we really need to see enough runway to take off and land again?
Fortunately, none of this is readily enforceable down in this forgotten corner of the PRJ.
If they are in the final approach segment in the US you also need an ADF.
Seems not to be true any more:
It’s somewhat moot anyway since I doubt if there are any approaches which haven’t long since had a GPS overlay.
Jacko wrote:
Isn’t take-off/rotation distance a quadratic function of speed, like landing distance (i.e. double the touch-down speed and we roughly quadruple the braking distance)?
Sure, but they’re not talking about aircraft performance but rather about what visibility/RVR the pilot needs for a safe take off. That would depend on the time it takes for the aircraft to travel a length of runway and that in turn is directly proportional to takeoff speed.
