@RobertL18C, sorry, not sure what you are quoting. Is that PART-NCC in the UK?
Yes. I have a DIY GPS-based procedure to my home airfield. It is designed according to PANS-OPS with 250’ obstacle clearance on final approach and 500’ on intermediate approach
For 250ft you have APCH/RNP0.3 annunciation?
I personally descend to 500ft above obstacles on TERM RNAV1, my impression to get 300ft, you legally need APCH RNP0.3 legs? 500ft above obstacles nearby complies with IFR rules and VFR rules for minimal cruise altitudes, circuits, circling….
I am puzzled “surveyed obstacles”, I am assuming anyone who flies IFR know how to find obstacles nearby and add 1000ft? adding x00ft during approach should not create a conceptual challenge to adding 1000ft for off-airway cruise…if one can fly MSA in cruise, I am sure they can fly MSA-500ft on approach 
Ibra wrote:
For 250ft you have APCH/RNP0.3 annunciation?I can descend to 500ft above obstacles on TERM RNAV1, my impression to get 300ft, you need APCH RNP0.3 legs?
The 250 ft is not related to the CDI scaling. It applies to all 2D procedures with FAF. The width of the protected area is of course related to the scaling.
You have to do RAIM and internal checks to fly APR leg, with SBAS you need APCH leg coded, adjusting CDI to 0.3nm does not cut it 
If you have GTN or G1000 NXI Perspective or new IFD you should get APCH leg
Altough on wet compass with nominated heading you can fly down to 300ft above obstacles on stopwatch 2D NPA (you can make that 250ft)
You have to fly on compass HDG bug and GPS RNAV1 OSB bellow MSA, I am bloody sure it’s legal, for instance there is NFW you can leave Cranfield without building your own instrument procedure…there is no departure in GPS database or IAP plates you have to make cuisine out of it and dead reckon your way…I am not sure how people who only fly SID & IAP bellow MSA would manage to depart from Cranfield with 400m RVR and no published and approved instrument procedure, I am sure someone here knows and should be able to tell us more?
Even @gallois is not aware he does 550m or 800m takeoff followed by instrument climb from LFFK without being on an official published procedure, he mostly fiddl4s with avionics like HDG bug and GPS OBS to depart in low weather, I am sure he does DIY departure straight into clouds bellow MSA from LFFK, he just does not know it, the DGAC are fully aware and it’s ok for them, they even approved it
One can always pretend or dream that they only fly SID+CAS+STAR+ILS but they are not based in LeBourget or Farnbrough, so they have to operate IFR in Golf off-airway, including sometimes bellow MSA without procedure, sometimes during low visibility & low ceiling takeoffs flying on crystal ball before getting radar identified…
According to many pilots, making your own departure or arrival in clouds using HDG or OBS bugs without procedure is not legal and reckless, the same pilots tend to use crystal ball and teleportation to stay legit when they are not on published procedures bellow minimal cruise altitudes
Ibra wrote:
You have to do RAIM and internal checks to fly APR leg, with SBAS you need APCH leg coded, adjusting CDI to 0.3nm does not cut it If you have GTN or G1000 NXI Perspective or new IFD you should get APCH leg
@Ibra, it does cut it! :)
I’ve verified it with Garmin manuals – if you manually set up the “track lines” to .3 nm each side, your alerting on a new GNSS devices will go off if the device cannot maintain it. If you don’t touch it and leave it as is, then it will alert only on 1nm+ errors.
So, if you fly your DIY approach with CDI set to 0.3nm, then as long as you main your normal approach standards (deviation is less than have a scale), your are flying in the corridor that is .9nm wide, i.e. .45nm each side (0.3nm CDI + half scale).
I need to read more then about alerts with CDI = 0.3nm but it’s not the same as APCH leg (there is surveyed area for LNAV which has nothing go do with CDI scalling)
I don’t do rocket scientist GPS/VLOC DIY I just descend 500ft bellow my IFR MSA land or go missed, usually to the nearby ILS I have flown 15min earlier, so far no issues legally or operationally, the risks during that 2min are way acceptable compared to legal scud run cruise…
Ibra wrote:
I need to read more then about alerts with CDI = 0.3nm but it’s not the same as APCH leg (there is surveyed area for LNAV which has nothing go do with CDI scalling)
Just read the alerting parts in the GNS-W manual – was news to me.
I am well aware it’s legal to fly in clouds without being on official procedures. The last autumn, I did one takeoff from Dreux with 2000m visibility straight into 300ft ceiling, you fly on HDG & OBS until your MSA or MVA
Ignoring legalities which are crystal clear in France, how does one practically depart with 550m/800m RVR from LFFK without being on published instrument departure? bonus question, why it’s 550m/800m and not 1500m as per the law of arrêté de 2019 you cited? should we get DGAC to fix that typo with the right aerodrome minima?
