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RNAV (RNP) and RNAV (GPS) minima

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Aircraft Systems, FAA Regulations, Instrument Rating

When I look at RNAV RNP and GPS approaches to an identical runway, I get hung up on this: why would a carrier go through the trouble of obtaining RNP authorization when the published minimums are LOWER for a standard GPS approach procedure using LPV? As an example, I reference ATL's 8R approaches: RNP 0.15 DA is listed as 1370/56, and GPS LPV is 1285/45. Are they anticipating future improvements that will eventually tip in RNP's favor? What's the payoff?

2 Answers

  1. John D Collins on Feb 02, 2014

    RNP procedures are based on Baro-VNAV for vertical guidance. The vast majority of air carrier and high end business jets have this capability. LPV uses WAAS GPS for vertical guidance. The airlines are not equipped with this capability. The only airline I know of that has WAAS and is approved for LPV is Horizon Airline. So they can do approaches that use Baro-VNAV but not WAAS for vertical guidance. On the other hand, most GA piston aircraft don’t have Baro-VNAV capability but many do have WAAS. Air carriers don’t want to spend the extra money to install WAAS capability.

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  2. Lemontree on Feb 10, 2017

    I guess the answer to this question should be found from RNP’s capability to fly the radius to fix (RF). With this capability, the aircraft doesn’t have to establish on the final approach course miles away from the runway, which all the conventional navaids including GPS and ILS still require. Just look at any RNP chart and see how an approach is made directly into the runway from the fixes which otherwise would require a procedure turn or vectors to the gateway (one or two miles away from the FAF).

    Then, what’s the benefits of it? For ATC, it obviously means less traffic congestion and more efficient use of their airspace because they no longer have to send aircraft miles away from the airport before bringing them back. For airlines, it means less flight time, less fuel, and thus less costs. So these are the payoffs of RNP.

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