RNP Approach - Loss of Capabilities
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RNP Approach - Loss of Capabilities
Consider the following scenarios:
a) Loss of RNP capability before starting an RNP approach
b) Loss of RNP capability before reaching the FAF
c) Loss of RNP capability on final approach
For A, you can't start the approach and must fly a different type of approach.
For B and C, you can only continue if you have the runway in sight, otherwise you must go around.
Am I right with this or am I having a brain fart?
Having mastered the good old days of NDBs, I just want to remind myself about the technological advances in this industry.
a) Loss of RNP capability before starting an RNP approach
b) Loss of RNP capability before reaching the FAF
c) Loss of RNP capability on final approach
For A, you can't start the approach and must fly a different type of approach.
For B and C, you can only continue if you have the runway in sight, otherwise you must go around.
Am I right with this or am I having a brain fart?
Having mastered the good old days of NDBs, I just want to remind myself about the technological advances in this industry.
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It looks correct in the EASA world, with the proviso that point (b) and (c) in the AMC underneath allow for continuing the approach with specific conditions.
Point (b) if navigation systems offer enough contingency, and point (c) if a downgrade to LNAV is deemed safe above 1000 ft.
Point (b) if navigation systems offer enough contingency, and point (c) if a downgrade to LNAV is deemed safe above 1000 ft.
Originally Posted by CAT.OP Regulation
CAT.OP.MPA.126 Performance-based navigation
Regulation (EU) 2016/1199
The operator shall ensure that, when performance-based navigation (PBN) is required for the route or procedure to be flown:
(a) the relevant PBN navigation specification is stated in the AFM or other document that has been approved by the certifying authority as part of an airworthiness assessment or is based on such approval; and
(b) the aircraft is operated in conformance with the relevant navigation specification and limitations in the AFM or other document referred above.
Regulation (EU) 2016/1199
The operator shall ensure that, when performance-based navigation (PBN) is required for the route or procedure to be flown:
(a) the relevant PBN navigation specification is stated in the AFM or other document that has been approved by the certifying authority as part of an airworthiness assessment or is based on such approval; and
(b) the aircraft is operated in conformance with the relevant navigation specification and limitations in the AFM or other document referred above.
Originally Posted by CAT.OP AMC
AMC6 CAT.OP.MPA.126
Performance-based navigation
ED Decision 2016/015/R
ALERTING AND ABORT
(a) Unless the flight crew has sufficient visual reference to continue the approach operation to a safe landing, an RNP APCH operation should be discontinued if:
(1) navigation system failure is annunciated (e.g. warning flag);
(2) lateral or vertical deviations exceed the tolerances;
(3) loss of the on-board monitoring and alerting system.
(b) Discontinuing the approach operation may not be necessary for a multi-sensor navigation system that includes demonstrated RNP capability without GNSS in accordance with the AFM.
(c) Where vertical guidance is lost while the aircraft is still above 1 000 ft AGL, the flight crew may decide to continue the approach to LNAV minima, when supported by the navigation system.
Performance-based navigation
ED Decision 2016/015/R
ALERTING AND ABORT
(a) Unless the flight crew has sufficient visual reference to continue the approach operation to a safe landing, an RNP APCH operation should be discontinued if:
(1) navigation system failure is annunciated (e.g. warning flag);
(2) lateral or vertical deviations exceed the tolerances;
(3) loss of the on-board monitoring and alerting system.
(b) Discontinuing the approach operation may not be necessary for a multi-sensor navigation system that includes demonstrated RNP capability without GNSS in accordance with the AFM.
(c) Where vertical guidance is lost while the aircraft is still above 1 000 ft AGL, the flight crew may decide to continue the approach to LNAV minima, when supported by the navigation system.
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Consider the following scenarios:
a) Loss of RNP capability before starting an RNP approach
b) Loss of RNP capability before reaching the FAF
c) Loss of RNP capability on final approach
For A, you can't start the approach and must fly a different type of approach.
For B and C, you can only continue if you have the runway in sight, otherwise you must go around.
Am I right with this or am I having a brain fart?
Having mastered the good old days of NDBs, I just want to remind myself about the technological advances in this industry.
a) Loss of RNP capability before starting an RNP approach
b) Loss of RNP capability before reaching the FAF
c) Loss of RNP capability on final approach
For A, you can't start the approach and must fly a different type of approach.
For B and C, you can only continue if you have the runway in sight, otherwise you must go around.
Am I right with this or am I having a brain fart?
Having mastered the good old days of NDBs, I just want to remind myself about the technological advances in this industry.
If you have RNP capability, fly the approach
If you are visual and can maintain it, you can fly a visual approach (why couldn't you prior to the FAF?)
If you're not visual, do something else!
G/A's - Our RNP for the approach is normally significantly higher than for the G/A's. Thus if our ANP falls below RNP (assuming not visual) we G/A and the RNP required goes up. In the absence of updating, our ANP usually falls at a slow rate (thus remaining inside the G/A RNP) and inside that time we can get to a suitable place that we can continue safely conventionally. That's for an aircraft with IRU's etc... If you're in a G/A aircraft I've no idea!
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I fly RNP approaches in a single engine GA aircraft.
In most cases, the airport still has at least one conventional approach for the targeted runway and the RNP and conventional missed approaches are very similar if not identical (differing only on the DA altitude).
And in most cases again, there is no obstacle clearance issue on the missed approach path.
Thus, I always also prepare the conventional missed approach as a backup and, if RNP capability is lost, it's mostly a non-event with a message to the controller stating that RNP capability has been lost and that we revert to the conventional missed approach unless they prefer to give us vectors.
As a counterexample, I fly to Colmar Houssen LFGA which has high ground in the westerly direction.
The airport has kept NDB approaches for runway 19 but only has a RNP approach for runway 01.
For Colmar and specially in IMC, I always write down the safe QDR limit to STR VOR (Strasbourg).
From memory, I think that it's R196.
If I were to loose RNP capability on a RNP 01 approach, I would fly the start of the RNP missed approach using heading, warn the control, and then join the HO hold (NDB) while climbing and while keeping an eye on the QDR to STR.
I don't have the special authorisation for Innsbruck LOWI and I don't know what should be planned for a GPS outage as the LOC R RWY26 approach has a missed approach that uses RNAV with RNP0.3 .
I guess that Innsbruck is only accessible to aircrafts that can fly with an inertial system that is independent of GPS signals.
In most cases, the airport still has at least one conventional approach for the targeted runway and the RNP and conventional missed approaches are very similar if not identical (differing only on the DA altitude).
And in most cases again, there is no obstacle clearance issue on the missed approach path.
Thus, I always also prepare the conventional missed approach as a backup and, if RNP capability is lost, it's mostly a non-event with a message to the controller stating that RNP capability has been lost and that we revert to the conventional missed approach unless they prefer to give us vectors.
As a counterexample, I fly to Colmar Houssen LFGA which has high ground in the westerly direction.
The airport has kept NDB approaches for runway 19 but only has a RNP approach for runway 01.
For Colmar and specially in IMC, I always write down the safe QDR limit to STR VOR (Strasbourg).
From memory, I think that it's R196.
If I were to loose RNP capability on a RNP 01 approach, I would fly the start of the RNP missed approach using heading, warn the control, and then join the HO hold (NDB) while climbing and while keeping an eye on the QDR to STR.
I don't have the special authorisation for Innsbruck LOWI and I don't know what should be planned for a GPS outage as the LOC R RWY26 approach has a missed approach that uses RNAV with RNP0.3 .
I guess that Innsbruck is only accessible to aircrafts that can fly with an inertial system that is independent of GPS signals.
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Yes, you are correct. Here in Canada we would:
Advise ATC and request a traditional or visual approach.
b) Loss of RNP capability before reaching the FAF
c) Loss of RNP capability on final approach
This depends. In radar and non-terrain critical cases, you can continue with the field in sight - just advise ATC. They can then issue you a visual approach clearance so that you can get alternate missed approach instructions. If you're IMC, execute a missed approach and ATC will issue radar vectors and a climb to at least the minimum radar vectoring altitude.
If you've lost capability before the FAF and you're flying a parallel RNP approach, then you have to advise ATC who will give you breakout instructions (a heading and an altitude).
If you're unlucky enough to be in a non-radar environment and you're in the mountains, I would suggest you follow your terrain recovery procedure and haul your butt up to the MSA. Pronto. Hopefully, you still have GPWS information to help you miss all the red and yellow spots. If not, do you have a weather radar that can be set to MAP mode and a co-pilot who can do it for you? Failing all that, you should have your approach chart. If you know roughly where you were and your speed, you can use that knowledge to avoid the hard stuff. We fly a few approaches like this at my airline, and I've certainly asked myself "what about now" through a few of those approaches. It's amazing how a little rain, ice, and/or turbulence can make those questions occur much more frequently.
The same goes for the question Jonty posed: what if your missed is RNP dependent? Here at our computers, I'd argue that is a highly unlikely situation and is the whole reason it is required work at my airline to check both the RAIM NOTAM and the RAIM through the box. Sitting in the airplane when that situation presents itself, who cares if the missed in RNP dependent. It's time to get out of Dodge by the most expeditious means
a) Loss of RNP capability before starting an RNP approach
b) Loss of RNP capability before reaching the FAF
c) Loss of RNP capability on final approach
If you've lost capability before the FAF and you're flying a parallel RNP approach, then you have to advise ATC who will give you breakout instructions (a heading and an altitude).
If you're unlucky enough to be in a non-radar environment and you're in the mountains, I would suggest you follow your terrain recovery procedure and haul your butt up to the MSA. Pronto. Hopefully, you still have GPWS information to help you miss all the red and yellow spots. If not, do you have a weather radar that can be set to MAP mode and a co-pilot who can do it for you? Failing all that, you should have your approach chart. If you know roughly where you were and your speed, you can use that knowledge to avoid the hard stuff. We fly a few approaches like this at my airline, and I've certainly asked myself "what about now" through a few of those approaches. It's amazing how a little rain, ice, and/or turbulence can make those questions occur much more frequently.
The same goes for the question Jonty posed: what if your missed is RNP dependent? Here at our computers, I'd argue that is a highly unlikely situation and is the whole reason it is required work at my airline to check both the RAIM NOTAM and the RAIM through the box. Sitting in the airplane when that situation presents itself, who cares if the missed in RNP dependent. It's time to get out of Dodge by the most expeditious means
