RA Setting for Non-precision Approaches

[lessaspirin]

Appreciate input on procedure regarding where to set the Radio Altimeter when flying non-precision based approaches?

Same question for approaches conducted to DA(H) when using VNAV.

Our current operational procedure requires crews to set RA to HAT unless known terrain will cause premature or false automated call outs. In the later case, procedure is to bury the RA to a minus value to inhibit automated call outs. Technical pilots are having mixed thoughts about this procedure and we'd appreciate input from the aviation community. :ugh:

B-767 - USA - CAT II/III certified - Honeywell Pegasus FMS

[acebaxter]

Two airlines, two different ways so far.

One we set the actual MDH if possible. If not then we would set 500 feet.

The other we always set 350 feet no matter what.

Different airlines, different philosophies.

As long as you can get your head wrapped around the reasoning for the SOP and you know that it's safe one way is probably as good as another.

As a side note the known obstruction thing brings back memories of Roanoke. When the wx was at minimums the older aircraft, without RA's would get in while the newer ones didn't. Seems there was a bit of a hill just before DH and it would set off the minimums call about 50 feet too early. If you weren't expecting it you could react and go around a bit before you actually had to.

[411A]

200 feet (or DH) for ILS approaches, other wise...200 feet.:}
SCD.

[Lenticular]

Hi,
In the offshore helicopter world during a non precision approach we set MDA/MDH -100ft for the PNF and the PF can set what they like but never below PNF setting. Usually MDA/MDH or the same as PNF.
For a precision approach PNF sets DA/DH - 50ft and again PF can set what they like usually as above.

[BOAC]

We had a go at this way back on PPRune and there was a suggestion that something like 500' would be a good idea to warn of being 'too low' over terrain and that Jepps and Aerad should consider printing terrain minimum clearances on NPA charts.

[tubby linton]

Jeppesen do print a minimum altitude on some npa charts.Have a look at some for Dublin as they have it printed on them, but it may be down to the state to provide the info.The trouble with setting the rad alt is when you are flying an approach to undulating terrain or somewhere by the sea-Heraklion Chania and Manchester on 05 come to mind.It can give you a completely false mental model!

[keithl]

Lenticular - do I know you? If so, come and have a chat!
You can set MDA -100 or MDH-100, either or, but NOT "MDA/MDH-100" as MDA and MDH are usually different numbers.
If you work for the same operator as I do, it is MDH-100.

[TopBunk]

We only set RA for ILS approaches, and then not for standard Cat 1 approaches planned to a manual landing.

RadAlts are great but work based of mapped terrain profiles close in to the runway for precision approaches.

Sure they give you great reminders at 2500' agl to check you have correct altimeter settings and to warn to check FAP etc, but other than that I feel that they may allow you to become fixated on RA rather than altimeter when your MDA is an altimeter based number.

I speak from an airline that has, amongst others, an automated '500' call and could understand why if auto callouts were not available, why 500ft may be set, but certainly not anything lower.

Remember that terrain on the approach is not always higher than the runway (in which case you get spurious early calls), but can be lower (eg when flying over sea on the approach, in which case you get late calls).

No, in my view, I prefer to set a negative RA unless carrying out an autoland, given automatic callouts.

[BOAC]

Remember that terrain on the approach is not always higher than the runway (in which case you get spurious early calls), but can be lower (eg when flying over sea on the approach, in which case you get late calls).
IIRC the object of the previous discussion on PPRune was to alert crews to a lower terrain clearance than you should have on the NPA. I believe the topic started following the AB at Strasbourg.

IF the terrain is below AAL on the approach, then you are less likely to hit it and vice versa, and an 'early call' would NOT be spurious if the correct TC margin were set. No danger of 'RA fixation' either since you are not using it other than for a warning that all is not well.

I've long forgotten the minimum terrain clearance calculated for a NPA - can anyone help, 'cos that is what it might be nice to set?

[JW411]

It is my understanding that (officially) the Rad Alt plays no part in a NPA. Nevertheless, I think most of us would use it just as a reminder.

[BOAC]

I'm sure we ALL understand the SOPs on the use of Rad Alts for minima, but I read the question as how can we enhance SAFETY on a NPA?