November 25, 2019 at 1:59 PM #6546
We were discussing the airliner arrival altitudes yesterday. I am a pilot for Southwest based in Las Vegas. Thanks to everyone at CSS for welcoming me since I have made Crestline my home site. I made the statement that there are no low arrivals. I was wrong about that. I apologize. I don’t fly into Ontario much and I have not been on this arrival for probably a year.
The arrival of concern is the Ziggy 7 from Palmdale. The NOAA charts are all online, but they do not show topography and they are not to scale and don’t lend themselves to visualization. The Jepp charts are the ones we use, but they are not available unless you pay for a subscription. I called Jepp and had them send me the Ziggy 7, I’ll post the other Ont, Lax arrivals when I get home and have my Southwest Ipad.
At the intersection FLAVR we are required to be at 14000 ft, 250 knots, then the flight path goes to lake Silverwood, HITOP intersection, before turning south and flying slightly east of Crestline. The next pertinent altitude is the little 8100 between HITOP AND NITIY. That is called the minimum enroute altitude and it guarantees terrain clearance and radio reception. So the lowest that ATC can clear us is 8100 ft to NITIY, except that ATC doesn’t clear to hundred altitudes, so the practical lowest would be 9000 ft.
However, the little 7.6 above the 8100 is miles between the intersections, so from FLAVR to NITIY is only 23.5 miles, which goes by very quickly when you start at 250 kts, so while ATC might clear us down to 9000, in most cases we won’t be that low by the time we get to NITIY.
Looking at the topography contour it looks like Crestline is about on a line from the “N” in NITIY to HITOP, or maybe a bit west, so the info to draw is that while most airliners won’t be as low as 9000 ft, it is possible that one may be that low behind launch. As long as we are in front of launch 10 or 12 thousand shouldn’t be an issue.
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