High-end RNP: flying through a soda straw

[Rotten Apple #1]

Nothing really new here. Just an article from Avionics Intelligence. Below I have quoted the section that specifically mentions WJ.

WestJet dividends


"We were trying to reduce the number of traditional non-precision approaches we were exposed to, and RNP fit that bill perfectly," says Darcy Granley, director of flight technical operations for WestJet. NPAs in mountainous terrain can require maneuvers such as circling (within a valley) to land. High-end RNP design criteria involve narrow, linear, lateral protection areas, and FMS-based flight path guidance. This, plus the ability to add curved segments -- known as radius-to-fix, or RF legs -- enables an aircraft to snake around obstacles rather than overfly them. Minimums can be much lower than those for traditional NPAs and flight paths can be safely shortened, reducing fuel burn.


WestJet can save about 80 pounds of fuel per arrival for straight-in RNP vs. conventional "dive-and-drive" approaches, where the aircraft constantly powers up and powers down as it comes down to the runway. On some approaches the airline can save almost 50 track miles.


RNP allows the Canadian carrier to lift more weight into terrain-rich environments like Kelowna, British Columbia, Granley says. This RNP 0.1 approach involves a number of RF turns through the valley to avoid terrain. RNP also allows WestJet to build departure profiles that allow a safe exit from a terrain-challenged airport even on a single engine. "You can work your way through the valleys...so you're not restricted by obstacles," he explains.


WestJet's B737NGs currently fly 82 RNP procedures -- 78 arrivals and four departures. Carriers tend to have more RNP arrivals than departures. Arrivals are typically more complicated than departures, giving airlines more opportunities to reduce operational risk and increase savings.


WestJet has worked with Naverus in Kent, Wash., on designing its RNP procedures under approval from Transport Canada. The carrier continues to collaborate with Naverus to optimize its RNP procedures. Naverus has added curved segments to some approach procedures so that the aircraft can set up in line with the runway closer in than before. This shortened transition cuts by five to 10 miles, on average, off the approach.


Down in the U.S. carriers would like to get more bang for their RNP buck in busier terminal airspace. According to one expert, if RNP SAAAR is good enough to get to terrain-challenged airports like Vail, Colo., airlines ought to be able to use RNP precision to increase capacity at other U.S. airports. Airlines want to exploit RNP SAAAR's tight lateral and vertical containment to be separated from adjacent traffic and fly much shorter final approaches.


Carriers, in particular, want to be able to fly RNP approaches alongside straight-in, ILS approaches onto parallel runways. The RNP airplane would be able to make the turn onto its final approach precisely enough to keep it at a safe distance from the ILS airplane heading onto the parallel runway. Known as RPAT (RNP parallel approach transition), this concept requires the RNP aircraft to visually acquire the ILS aircraft before crossing the final approach fix.

[looproll]

the future of approaches is here!

[F-16]

Except it's now changed from RNP SAAAR to RNP AR.

Crazy to think that on a RNP-0.1 arrival you could be in a radius-to-fix leg, turning to final as you hit minimums - so many possibilities.

[BEFAN5]

The RNP approaches are great for many reasons (time, less fuel burn, safety etc). But sometimes these approaches do not work into the greater picture of traffic flow. A few too many times I have heard a few pilots get overly agitated at ATC when they are declined the approach they want.

[Rotten Apple #1]

BEFAN5, are you referring to the short gate RNPs specifically? Or do the straight in approaches create the same issue you refer to? I haven't flown with anyone yet who would sound agitated over being declined the approach. Maybe someone was having a bad day?

I flew the RNP approach into Palm Springs last month for the first time when we actually needed the minimums it enables, and it was a thing of beauty. Hopefully the rest of the air carriers out there catch up to the technology available on the market.

[zzjayca]

Sometimes the short gate RNP doesn't work. I for one love it and will clear you for it anytime I can. However, in the last couple of years, I have lost count of the number of agitated responses from Westjet pilots when the short gate isn't available. I sure hope there aren't that many Westjet pilots "having a bad day" on a regular basis.

[The Hammer]

Sort of like buying a ferrari and then driving the 401 at rush hour or living in Iqaluit. Nice to have but it is really appropriate to bitch about not being able to use it to it's fully capabilities ALL the time. Is RNP really going to improve the DFW, ORD, ATL's of the world. Don't get me wrong it a frickin' amazing tool for 75% of WJ destinations. (YYC/YYZ not being great examples of this)

Sounds like when WJ went to YYZ in 2003?? It was hilarious to listen to the radio (ground especially). I understood their frustration but had long since determined that I was not going to let it ruin my day anymore or waste even more 1 second of my life. (At that time, I was either landing or take-off from YYZ on every leg)

Hammertime

[WJ700]

Is it just me? I can't figure out what you are trying to say there Hammertime.