boscomantico wrote:
My take on that approach: you either have an approach-approved GPS (and use the overlay) or you have not (i.e. only an ADF, nothing else)In the first case, you can use the GPS distance from the threshold to do the CDFA.
In the latter case, you turn inbound after the procedure turn, and as soon as established on the final approach track, you descend to the MDA (and go missed after reaching the NDB again). Since you don‘t have the distance from the threshold, you can‘t do the CDFA (no way to monitor it).
You’re right, so for the OP’s approach plate you can’t make approach without approach-approved GPS since the plate specifies only CDFA.
You are confusing two different elements of minima. If flying a precision approach you make the decision to go around at the DA which means that you will descend below this altitude during the missed approach procedure. It is recommended that you add 50ft for PEC to avoid altimeter errors which could mean you descending into a dangerous position. However, if there is no reference to the PEC error in your POH there is no requirement in the UK to add the additional margin, it is just recommended and I would suggest advisable on a test or revalidation flight. If flying a non precision approach you must not descend below the MDA on the missed approach and therefore would commence the missed approach procedure above the MDA when flying a CDFA to avoid descending below minima.
The general rule of thumb (maybe not rule of law?) is to add 10% of RoD to get DDH from MDH on a 2D NPA flown as CDFA, at -500fpm that make it 50ft for 100kts aircraft on 3deg path, for risks real or imagined of dipping bellow MDH on the go-around, I think worth reading Airborn_Again article
PEC error is 50ft for altimeter on ILS if nothing in POH but it’s rather academic recommendation
My minima is 50ft + plates, if there is anything sensible to add it’s on the x-axis not the z-axis (3km visibility is a good start, with 10km visibility flying down to any OCH value is piece of cake, in 2km visibility, you can be out of clouds at 1000ft but can have a hell of time spotting the runway: good luck with hours of looking at 300ft flown as MDH let alone split seconds while looking on 200ft DH 
)
Peter wrote:
Just checked – APM book 5, page 476, step 2: “For precision approach add 50 feet PEC (nil correction for a non-precision approach)”.This one? That’s the old Trevor Thom books.
I am surprised
That’s the one! The same one that says that you cannot go below MSA (obstacle height+1000ft within 5nm radius) at your destination unless there is a procedure there…
If you have an IR and are current then you should be capable of hand flying to minima, 200ft and 800m on a precision approach. You may choose to set yourself higher minima if you feel out of practice but don’t get into the mindset of saying that it is difficult to see the runway when flying to minima. This is the purpose of having an IR.
JohnR wrote:
However, if there is no reference to the PEC error in your POH there is no requirement in the UK to add the additional margin, it is just recommended and I would suggest advisable on a test or revalidation flight.
This seems like another cultural thing. I’ve never heard of any requirement or recommendation to add a PEC if there isn’t one in the POH until I read posts from UK pilots in this forum. It was certainly neither taught nor tested on either my initial (1987) IR or my renewed (2014) IR in Sweden.
If flying a non precision approach you must not descend below the MDA on the missed approach and therefore would commence the missed approach procedure above the MDA when flying a CDFA to avoid descending below minima.
Is I wrote above, that is far from clear both from a regulatory or safety point of view.
Airborne_Again wrote:
This seems like another cultural thing
Does anyone know where it comes from?
I’ve wondered if its just come from ‘bramston and Birch’ and then passed into IMC folk law
I find it very strange that someone could fail an IMC/IR test if they use DA/MDA as published on the jepperson chart as they didn’t add 50 feet PEC for a precision approach.
I love the bit where you add 50 feet to the ILS system minima which then makes it the same as for the none precision localiser only approach.
U.K. AIP AD
4.6 Altimeter Error4.6.1 When calculating Decision Height (DH), account must be taken of the errors of indicated height which occur when the aircraft is in the approach configuration. Details of the Pressure Error Correction (PEC) should be available from the aircraft Flight Manual or handbook. In the absence of this information a PEC of +50 FT has been found to be suitable for a wide range of light aircraft and should be used. This addition of 50 FT need only be applied to DH. The required RVR should be calculated prior to applying the PEC.
MattL wrote:
4.6 Altimeter Error
4.6.1 When calculating Decision Height (DH), account must be taken of the errors of indicated height which occur when the aircraft is in the approach configuration. Details of the Pressure Error Correction (PEC) should be available from the aircraft Flight Manual or handbook. In the absence of this information a PEC of +50 FT has been found to be suitable for a wide range of light aircraft and should be used. This addition of 50 FT need only be applied to DH. The required RVR should be calculated prior to applying the PEC.
That only means that UK authorities recommend the +50’ in the absence of information in the POH.
