Graham wrote:
Perhaps you should write exam questions for EASA ;-) They love this stuff.
Well, I am a university teacher by profession so I know both how to explain things and how to ask questions.
Seriously though, it’s avionics learning not PBN learning. An instructor or examiner might be interested in exactly when you unsuspend, but as with many things in aviation that’s a different issue to how one operates in the real world.
It is not avionics learning. Certainly what particular button to push is avionics dependent, but when you should push it is not – it’s in the TSOs. With the same reasoning you could say that there are no principles involved in using an ILS or VOR – it’s just “avionics learning” as different boxes have their knobs and buttons in different places. Of course there are.
The answer to my previous question is that if you have a non-SBAS navigator and the missed approach begins with a turn at a specific altitude, then you should not unsuspend until reaching that altitude. If you do, then you will be given course guidance for an immediate turn. If you (or the A/P) follows this guidance (remember this a high workload situation) you may hit something and die. So this is very relevant to how you operate in the real world.
If you have an SBAS navigator, it will know that you should be given guidance for a straight course until the relevant altitude is reached so you can unsuspend at once. The same if the missed does not start with a turn.
(Of course this has nothing to do with the SBAS capability as such, but that non-SBAS and SBAS boxes have different TSOs.)
Airborne_Again wrote:
The answer to my previous question is that if you have a non-SBAS navigator and the missed approach begins with a turn at a specific altitude, then you should not unsuspend until reaching that altitude. If you do, then you will be given course guidance for an immediate turn. If you (or the A/P) follows this guidance (remember this a high workload situation) you may hit something and die. So this is very relevant to how you operate in the real world.
This much was obvious to me, because your exact position when going missed (and your rate of climb thereafter) is a moveable feast and therefore only you can decide when to begin the turn, not the box. The distance travelled between going missed and beginning the turn is variable – it’s the one part of the whole thing that the box can’t do on its own and needs you to tell it when you’re ready for it to begin giving direction again. I didn’t understand your question to be honest and didn’t think you were asking something so basic.
If the next thing it’s going to tell you to do (after you unsuspend) is turn, then you don’t want to do that until you’re ready to turn, i.e. have reached the altitude. Or you could unsuspend and then ignore the course guidance until you are ready to turn.
This is what I mean when I say I’m flying the plate, not the CDI. And again, because I’m flying without an A/P I don’t have the issue that the box directly dictates what the aeroplane does. In the EGBJ RNP Rwy27 example, I’m going to climb to 1,500’ straight ahead before beginning a right turn (not before the MApt) in the climb to 2,800’. If the box (for some reason) told me to turn before I reached 1,500’ then I would ignore it. Who’s in charge, you or the box?
In the EGBJ RNP Rwy27 example, I’m going to climb to 1,500’ straight ahead before beginning a right turn in the climb to 2,800’. If the box (for some reason) told me to turn before I reached 1,500’ then I would ignore it. Who’s in charge, you or the box?
Actually, you are right for EGBJ RNP Rwy 27, you have to disregard all box indications (it’s an RNP approach where the missed is flown with paper plates with an ADF neddle or Radar vector), however, that is a very rare exception not the norm for PBN/RNP/GPS, elsewhere you are expected to fly an RNAV1 missed as per box guidance: properly understandood and set it up, I am sure someone will say it’s a fail in FAA, DGAC, German tests and it could be a fail in real life (in terrain without radar), if one can do it without any box at all, it’s even better !
Graham wrote:
This much was obvious to me, because your exact position when going missed (and your rate of climb thereafter) is a moveable feast and therefore only you can decide when to begin the turn, not the box. The distance travelled between going missed and beginning the turn is variable – it’s the one part of the whole thing that the box can’t do on its own and needs you to tell it when you’re ready for it to begin giving direction again.
An SBAS box can very well decide on its own when to begin the turn. Which is what I wrote. I’m starting to feel that people are not bothering to read what I’ve actually written.
I didn’t understand your question to be honest
I think you still don’t understand the question.
At some point you have to unsuspend if you want the navigator to give you guidance for the missed approach. The question is when. Usually you would want to do this as early as possible to ensure continuous course guidance. The case where it matters is when the missed approach starts with a climb to a specified altitude (as opposed to a specific point) and then a turn. If you have a non-SBAS box you should wait with the unsuspend until reaching the specified altitude, if you do not the navigator will give incorrect course guidance. An SBAS box doesn’t have that problem, you can unsuspend as soon as you wish.
and didn’t think you were asking something so basic.
If that’s basic to you, fine. It certainly wasn’t obvious to me.
Airborne_Again wrote:
At some point you have to unsuspend if you want the navigator to give you guidance for the missed approach
The calculated base/missed turn in SBAS/NonSBAS boxes or CNF points are just small tiny details of the iceberg, what you missed (no pun intended) is that is not how RNP training or execution is done in UK, almost every RNP missed is flown on legacy NavAids or Radar vectors, whatever the reason behind that funky choice of PBN implementation: GPS reliability, airspace CAS busts, love of NDB, ATC protection, AD NAV protection, CAA level of expertise? it is not helping when you want to talk about how you would universally fly an RNP in say Mexico as per PBN/ICAO
AFAIK, the few “pure RNP” exceptions are: Kemble, Sywell and Cardiff, the latter being the only one you can practically fly during an IR test…the lack of understanding is not an issue with UK flat terrain and aisrpace: you can turn and fly as you wish uncontrolled and in airspace you will be on radar but I have been in cockpit with few instructors & examiners, you will need advanced CRM when they start touching GNS/GTN to insert a hold or go missed…
Ibra wrote:
The calculated base/missed turns in SBAS boxes or CNF points are just small tiny details of the iceberg,
Well, sure, but I had to pick some example of essential but non-obvious knowledge.
what you missed (no pun intended) is that is not how RNP training or execution is done in UK, almost every RNP missed is flown on legacy NavAids or Radar vectors,
I know that, but that’s hardly relevant in a general discussion, involving not only people from the UK but also from e.g. France.
Airborne_Again wrote:
An SBAS box can very well decide on its own when to begin the turn. Which is what I wrote. I’m starting to feel that people are not bothering to read what I’ve actually written.
Yes sorry, I thought we’d delved far enough into that to establish that we were discussing a non-SBAS scenario. My apologies for not stating that my statement applied to a non-SBAS scenario.
The point is the beginning of the turn for such a missed approach procedure is not defined as a fixed point in space. It is defined by criteria (e.g. on reaching 1,500’ on the runway heading, not before the MApt) and a box giving vertical guidance (i.e. SBAS) can establish when these have been met and tell you to begin the turn but when you’re 2D-only it requires the pilot to look at the altimeter and decide when they’ve been met. Thus it stands to reason that, if the procedure involves something that the box can’t establish for itself then you wouldn’t want it to start giving directions (or more accurately you wouldn’t want to start following them) until you’d established for yourself that the altitude criteria had been met.
Again, primarily flying the plate. The CDI is very useful, but it is not God. I don’t know about you, but I only follow its commands if I’m expecting those commands at that time. It does not overrule my own knowledge of where the aircraft is pointing and where it should be pointing.
Ibra wrote:
RNP training or execution is done in UK, almost every RNP missed is flown on legacy NavAids or Radar vectors, whatever the reason behind that funky choice of PBN implementation:
My guess is it’s to avoid extra design and certification cost. If the missed approach procedure to that runway already exists with legacy navaids then it is easy to reuse it as-is and avoid the (no doubt rather unnecessary anyway) costs of having the exact same path through space defined in an RNP context.
Well is it the SBAS or the introduction of RF legs coming with SBAS :-), which in fact was an upgrade of the ARINC 424 path and terminator standard?
This question can be asked the same for a SID which is programmed into the KLN90B without the RF leg if you follow that then you immediately turn in stead of flying the RF leg available on WAAS (SBAS) box…
The lesson I think airborne is trying to propagate, read the TEXT and apply this to the capabilities of your navigator, which can be a mix of using your legacy nav boxes and GPS…to figure out the distance or altitude need before the turn can be made as written in the textual description of the missed……….
From the FAA for the complete approach phases including missed:
RF turn capability is optional in RNP 1 eligibility. This means that your aircraft may be eligible for RNP 1 operations, but you may not fly an RF turn unless RF turns are also specifically listed as a feature of your avionics suite.
The related nerd question would be: what about an C146 box with WAAS switched off? Will it behave like an “SBAS box” or like a non-SBAS box in terms of the missed approach sequencing behaviour?
