RNP Approaches

SennaP1

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I've only started hearing of these "Required Navigation Performance" -is that right? approaches as of a few months. Seems like AK is the airline that started/pioneered it, am I right in saying that? What exactly is a RNP approach and are there actual approach plates for it? Of what I've read its like a typical RNAV/GPS approach with both LNAV and VNAV functions? Do you need FMS for it? What about INS/IRS? Is it like a WAAS kinda idea? Anyhow seems pretty interesting, any enlightenment, I'm asking becuase it seems like a good ground discussion for my instrument students.
I hear that the approach into Juneau is a RDP as they have no radar there.

Thanks in advance.

:)
 

AK737FO

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RNP

RNP approaches were indeed pioneered by Alaska. They are GPS approaches that require no other ground based nav systems. They are autopilot / autothrottle approaches. The only thing the pilot does is add flaps and gear at the appropriate speeds. At minumums you either click off the autopilot and land or you press TOGA and the jet flys an RNP miss.

Most of Southeast Alaska, where RNP is a valuable tool, is a non-radar environment below about 8,000 feet. The company is currently working on RNP into DCA and SFO as well.
The approaches are RNAV and VNAV, they require FMS as well as IRS. The computer is constantly checking RNP (required) with ANP (actual) position. If you were to suddenly loose all GPS input, the IRS is accurate enough (coasting) to safely fly the miss.

As far as I know, the approach plates are custom made for us by Jepps.

There is a lot of typing envolved in setting it up. If you are planning to fly from JNU to SIT - a very short leg - you have the entire flight plan in the box at the gate at JNU - including the approach brief at SIT. Then you just sit back and watch...

The approaches can be curved, can have a dog-leg in them or can be straight in like an ILS. Flying the back door into JNU is very impressive. You watch the jet fly the purple line down the middle of the channel while the EGPWS paints red mountains on both sides. Pure magic.
 

cpritchie5

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Most airlines do RNP approaches. you don't need special approach charts. As long as the airplane is GPS equiped and the approach is in the FMS data base all you have to do is change the RNP value to .3 which is standard unless something is different on the chart.
 

AK737FO

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Not the same...

What your talking about is flying a NDB or VOR approach through LNAV and setting the RNP value to .3. You are correct in that if any land based approach is in the box you can LNAV it.

That is not the same as what Alaska does with stand alone RNP approaches. The approach plates say RNP (and nothing else), they are gps only approaches needing no input from ground based nav equipment. We are the only pilots I have ever seen with these types of approach plates and they are custom tailored for us. The approach can be hand flown only if using minimums predicated off of .3, they must be autopilot / autothrottle flown if you want the lowest available minumums with are predicated off of .15.
Back in the day when we could actually have other airline pilots in our jump seat they were impressed with our RNP approaches and had never seen anything like it. To the best of my knowledge Alaska is the only airline flying RNP approaches. I heard United is interested in the technology especially since we will soon be using it in SFO but I doubt if they will be spending any cash on new technology any time soon.
 
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