The tolerance tresholds and levels of performance required vary greatly for the use of a GPS module depending on the phase of flight. Although we (the company) have been able and trained to conduct LNAV approaches where applicable, the introduction of VNAV/LPV technology brings up a completely new dimension (yup, 3D approaches!) So training for the use of the GPS for approaches and a quick review of the related rules was incorporated in the ride.īefore we go any further, I would strongly suggest that you read the first part of this article (if you have not done so already) to familiarize yourself with a few terms and basic underlying principles. As it happens, our fleet of PC12NGs is getting a software update, which will eventually allow us to complete LPVs approaches virtually everywhere. Also note that the missed-approach point (MAPt) is passed the runway! In other words, the aircraft is in no position to land when becoming visual at the MAPt.I recently had the “pleasure” to complete my yearly recurrent ride. This is how non-precision approaches were conventionally flown, you can imagine that this isn’t the preferred method of flying an approach with a Boeing 747, flying level at a few hundred feet with flaps and gear out… That is why this approach is not authorized for Cat C & D. Here is an example of an old non-CDFA approach. You can create a pilot derived DA/H by adding a margin for decision making and altitude loss in case of go-around (the +30/50 ft addition as described above). No matter what the chart manufacturer calls those, they are in fact MDA/H, in other words you are not allowed to descent below that altitude so you need to make the decision before passing the MDA/H. Nowadays most NPA approaches are flown as CDFA approaches but the requirements for minima on those approaches have not changed. Non-precision approaches are conventionally flown as non-CDFA (Continuous Descent Final Approach) meaning that an aircraft would descent to the MDA/H, level-off, fly level to the missed-approach point (MAPt) and then decide whether to land or go-around. The reason for this has to do with history. For bigger aircraft its probably more but its up to the operator to establish those. Minimaīe aware that the DA/H on a LNAV or LP approach is actually a MDA/H, Jeppesen publishes these minima as DA/H (at least in Europe) but those have no margin built in for altitude loss in case of go-around so you have to make the decision above this DA/H, we add +30 ft for turboprops in our fleet and +50 ft for jets. Usually en-route = RNP 5, terminal operations = RNP 1, approach = RNP 0.3. Otherwise the meaning is the same, RNP 5 or RNAV 5 (also called BRNAV) means that the Total System Error (TSE) should be less than the RNP number (example RNAV / RNP 5 = 5 nm) for 95% of the flight time. In the diagram below you can see the different approach categories, conventional procedures, RNP approach procedures, RNP AR (approval required), and GLS (GPS Landing System).Īll approaches are labelled RNP nowadays, the only real difference between RNP and RNAV is that for RNP there must be a alerting system available, warning the pilots in case of loss of RAIM (Receiver Autonomous Integrity Monitoring), loss of position (FMS in dead-reckoning mode) or Actual Navigation Performance (ANP) exceeding the Required Navigation Performance (RNP). In the basis ICAO has prescribed 2 types of approaches, one type with minima of 250ft or higher (further divided into Non-Precision Approach (NPA) and Approach with Vertical Guidance (APV)) and approaches with a minima below 250 ft (Precision Approaches ¶). VOR = VHF Omnidirectional Radio Range ICAO Approach Classifications SBAS = Satellite Based Augmentation System ![]() LPV = Localizer Performance with Vertical Guidance ![]() ABAS = Aircraft Based Augmentation System
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