NCYankee wrote:
The comment on legality is specified in the GPS AFMS, under limitations. In US regulation, the limitations section is regulatory and must be followed. The approach procedure must be loaded from the database and the data in the database entry must be current. Several things don’t occur if you just manually enter the approach waypoints, the integrity and alerting does not occur, the CDI guidance is not automatic, missed approach guidance is unavailable
Is that the same in Europe? This is EuroGA, after all.
The US is going to define LPV with a DA at 250 or lower to be a precision approach….so pilots must plan to use the NPA LNAV minimums of 800-2 Although LPV vertical and lateral guidance will have a very high availability, LNAV will be much closer to 100% and does not depend on SBAS even operating
Thanks, I guess for Part91 (not 121 or 135)?
Here, NCO (91) & CAT (135) have few divergences for planning but NCO are heavily penalised as they have no other mean to maintain RNAV1 without GPS or VNAV without SBAS (except one or two aircrafts out there), currently someone operating NCO can’t treat RNP LPV as precision with available LNAV or SBAS during planning: 1/ they have to plan CONV at destination/alternates or ensure good weather prevails and 2/ they have to ensure TAF ceiling > LNAV MDH at destination or > LNAV MDH+200ft at alternate (+1000m on visibility)
My understanding this will get phased in 2022Q2 where one does not even need to plan conventional approach at all (just some “extraction”) but they get hit by beefed up ceiling & visibility VMC++ even beyond what is needed for VFR/SVFR, which seems closer to US planning
Is that the same in Europe?
Indeed, same in Europe lot of stuff will be in the AFMS for IFR GPS install with RNP APCH approval (except in two “VFR Robin” with 2*G5+GTN in my AeroClub which does not have those sections, they fly ok in clouds though on VOR but I doubt legal for approach on GPS 
), I think some even say to fly AP coupled LPV you have to be PIC sitting in LHS? I need to check which AFMS (TB10? or TB200? or TB20?) had this but I find it shocking…
@NCYankee "APV approach with vertical guidance is defined in ICAO doc 8168 as:-
“An instrument procedure which utilizes lateral and vertical guidance but does not meet the requirements established for precision approach and landing operations.”
In various diagrams these include LNAV/VNAV and LNAV + V. In most of the PBN documents I have seen they seem to treat LNAV/VNAV and LNAV + V as interchangeable.
Graham wrote:
Interesting – is there a reference to where in regulations it says you must load the approach in the box and use the various features? I thought the point of PBN was that it was just a concept of navigational accuracy/reliability standards and it wasn’t so prescriptive about how you met them?
The AFMS for an IFR certified GPS is a supplement to the Airplane Flight Manual and will have a limitations section. In US, they are required to be FAA approved and are regulatory.
23.2620 Airplane flight manual.
The applicant must provide an Airplane Flight Manual that must be delivered with each airplane.
(a) The Airplane Flight Manual must contain the following information –
(1) Airplane operating limitations;
(2) Airplane operating procedures;
(3) Performance information;
(4) Loading information; and
(5) Other information that is necessary for safe operation because of design, operating, or handling characteristics.
(b) The following sections of the Airplane Flight Manual must be approved by the FAA in a manner specified by the administrator –
(1) For low-speed, level 1 and 2 airplanes, those portions of the Airplane Flight Manual containing the information specified in paragraph (a)(1) of this section; and
(2) For high-speed level 1 and 2 airplanes and all level 3 and 4 airplanes, those portions of the Airplane Flight Manual containing the information specified in paragraphs (a)(1) thru (a)(4) of this section.
91.9 Civil aircraft flight manual, marking, and placard requirements.
(a) Except as provided in paragraph (d) of this section, no person may operate a civil aircraft without complying with the operating limitations specified in the approved Airplane or Rotorcraft Flight Manual, markings, and placards, or as otherwise prescribed by the certificating authority of the country of registry.
(b) No person may operate a U.S.-registered civil aircraft –
(1) For which an Airplane or Rotorcraft Flight Manual is required by § 21.5 of this chapter unless there is available in the aircraft a current, approved Airplane or Rotorcraft Flight Manual or the manual provided for in § 121.141(b); and
(2) For which an Airplane or Rotorcraft Flight Manual is not required by § 21.5 of this chapter, unless there is available in the aircraft a current approved Airplane or Rotorcraft Flight Manual, approved manual material, markings, and placards, or any combination thereof.
As an example, this is an excerpt from the limitations section of the Garmin GTN 750 AFMS:
2.8 Navigation Database
GPS/SBAS based IFR enroute, oceanic, and terminal navigation is prohibited
unless the flight crew verifies and uses a valid, compatible, and current
navigation database or verifies each waypoint for accuracy by reference to
current approved data.
“GPS”, “or GPS”, and “RNAV (GPS)” instrument approaches using the
Garmin navigation system are prohibited unless the flight crew verifies and uses
the current navigation database. GPS based instrument approaches must be
flown in accordance with an approved instrument approach procedure that is
loaded from the navigation database…
2.10 Instrument Approaches
a) Instrument approaches using GPS guidance may only be conducted when the
GTN is operating in the approach mode. (LNAV, LNAV +V, L/VNAV, LPV, LP, or LP +V
b) When conducting instrument approaches referenced to true North, the NAV
Angle on the System -Units page must be set to True.
c) The navigation equipment required to join and fly an instrument approach
procedure is indicated by the title of the procedure and notes on the IAP
chart. Navigating the final approach segment (that segment from the final
approach fix to the missed approach point) of an ILS, LOC, LOC-BC, LDA,
SDF, MLS, TACAN approach, or any other type of approach not approved
for GPS, is not authorized with GPS navigation guidance. GPS guidance can
only be used for approach procedures with GPS or RNAV in the procedure
title. When using the Garmin LOC/GS receivers to fly the final approach
segment, LOC/GS navigation data must be selected and presented on the
CDI of the pilot flying. When using the VOR or ADF receiver to fly the final
approach segment of a VOR or NDB approach, GPS may be the selected
navigation source so long as the VOR or NDB station is operational and the
signal is monitored for final approach segment alignment.
d) Advisory vertical guidance deviation is provided when the GTN annunciates
LNAV + V or LP +V. Vertical guidance information displayed on the VDI in
this mode is only an aid to help flight crews comply with altitude restrictions.
When using advisory vertical guidance, the flight crew must use the primary
barometric altimeter to ensure compliance with all altitude restrictions.
e) Not all published Instrument Approach Procedures (IAP) are in the
navigation database. Flight crews planning to fly an RNAV instrument
approach must ensure that the navigation database contains the planned
RNAV Instrument Approach Procedure and that approach procedure must be
loaded from the navigation database into the GTN system flight plan by its
name. Pilots are prohibited from flying any approach path that contains
manually entered waypoints.
gallois wrote:
In various diagrams these include LNAV/VNAV and LNAV + V. In most of the PBN documents I have seen they seem to treat LNAV/VNAV and LNAV + V as interchangeable.
They are in no way interchangeable. +V is advisory and not ever to be used as APV.
Airborne_Again wrote:
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.
I agree that the SBAS Navigator will have the capability, but it depends on the installation and if a baro-corrected altitude is an input the Navigator.
boscomantico wrote:
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?
My expectation is that it would behave the same as if SBAS was enabled.
@ NCYankeeTaken from the latest version of UK CAA CAP 773 you will notice some differences to the FAA PBN. In this version on first glance LNAV +V has been deleted altogether.
3.5.5 Vertical Navigation
At the time of publication (Autumn 1014), RNAV (GNSS) approaches with vertical
guidance provided by the GPS+SBAS (APV or LPV) are limited in the UK. There are a
number of approaches published with LNAV/VNAV minima shown on the chart. Approach
to the LNAV/VNAV minima may only be flown using a BARO-VNAV installation approved
in accordance with EASA AMC 20-27A.
Aircraft fitted with a GNSS navigation system using SBAS for vertical navigation and
approved in accordance with AMC 20-28 ARE NOT authorised to fly these approaches to
the published LNAV/VNAV minima.
At the time of writing the use of SBAS for vertical navigation on approach is only permitted
where the approach is designated with defined LPV minima. The body responsible for the
approach (normally the airport authority or approach sponsor) is required to meet a
number of additional requirements in order to provide information about the availability and
integrity of the approach for use with the EGNOS SBAS signal. Without these additional
measures, the availability, integrity and accuracy of the vertical guidance cannot be
assured. On an RNAV (GNSS) approach, other than a notified LPV approach using SBAS,
the primary vertical reference must, therefore, be the aircraft pressure altimeter at all times and not the GPS derived vertical guidance.
2.7.3 LNAV/VNAV (Lateral Navigation / Vertical Navigation)
This is a 3D Approach Procedure with Vertical Guidance (APV). The lateral navigation
guidance is provided by GPS and Aircraft Based Augmentation Systems (ABAS) such as
RAIM in the same way as for LNAV. The vertical guidance is provided by a Barometric
Altimeter. This type of approach is commonly known as APV/Baro VNAV. Lateral guidance
is normally linear with accuracy to within +/- 0.3 NM parallel to either side of the final
approach track. Some aircraft systems may provide angular guidance, however, and pilots
should be aware of the display format of their system.
Vertical guidance derived from the barometric data in the Flight Management System
(FMS) is based on normal altimetry and any displacement from the indicated glidepath
represents the same altitude error throughout the final approach. This is fundamentally
different from the angular indications such as on an ILS glidepath.
WARNING! At the time of writing this document (Autumn 2014), the use of SBAS to
provide augmentation for the VNAV element of a notified LNAV/VNAV approach is not
permitted in the UK. Notwithstanding any certification for RNAV VNAV approach
operations using SBAS, aircraft which are not certified for the use of barometric VNAV
data are currently precluded from flying approach operations to LNAV/VNAV minima.
These aircraft are not authorised to continue RNAV approach operations below the
published LNAV-only minima.
2.7.4 LPV (Localiser Performance with Vertical Guidance)
This is an Approach Procedure with Vertical Guidance (APV). The Lateral and Vertical
guidance is provided by GPS and SBAS. Lateral and vertical guidance are angular with
increasing sensitivity as the aircraft progresses down the final approach track; much like
an ILS indication.
NOTE: The instrument approach procedures associated with RNP APCH are entitled
RNAV (GNSS) to reflect that GNSS is the primary navigation system. With the
inherent onboard performance monitoring and alerting provided by GNSS, the
navigation specification qualifies as RNP, however these procedures pre-date PBN, so
the chart name has remained as RNAV.
So it looks like there might be slight differences between different countries.
I believe in France all RNAV approaches are going to be identified as RNP in the future. I believe this is going to evolve when a plate changes.
Ibra wrote:
For going missed with turn right after some altitudeAdding to nerdy questions: how does TSO146 box with SBAS/WAAS switched off know you have crossed your (barometric) altitude terminator, let alone calculate the turn after, especially if it does not have Baro-VNAV feeds
If there is a barometric altitude corrected for local QFE input to the SBAS Navigator, then whether or not one is inside a SBAS service volume or SBAS is turned off, the altitude is known. An installation that has an altitude input is more typical with a glass PFD which has ADHRS type digital outputs whereas a typical steam gage panel is not likely to have this. With the latter, you get multiple suspends, one at the MAP, and once you unsuspend, another if an altitude must be achieved before a turn. After selecting the missed approach guidance, this is what the GNS530W says:
Note that within a few seconds of pressing
OBS to release suspend mode and start the
missed approach sequence, “SUSP” re-appears
above the OBS key as the 500W-series unit
returns to suspend mode. This is normal when
flying a “course from fix to altitude” leg and
indicates that automatic leg sequencing is
suspended.
