Which is the correct Altimeter?

[Charan Kumar]

Two acft arriving from the north on the GOLDN5 arrival, first one for KSFO, the second one in trail for KSJC, we give LOZIT at 11k and DUXBY at 12k respectively. While the Altimeter for KSFO and KSJC won't be that different or hardly any different, but in the cases they are, which is the correct altimeter to give the KSJC arrival? Rule of thumb we give the destination airport Altimeter, but wouldn't it make a difference if the altimeters are different putting the acft at less then <1k difference in altitude? ( I hope I got the last sentence correct).

[Gene Cao]

well, if the altimeter's were way off(IF) then i guess it would matter.....cuz then that sjc guy could truly be at 11k while he thinks hes at 12k...... just my guess

[Jonah Zieske]

You would give them the altimiter of the field they are arriving at...

From FAA Order JO 7110.65T 2-7-2.c4

(Issue the altimiter setting)For the destination airport to arriving aircraft, approximately 50 miles from the destination.

[Charan Kumar]

You would give them the altimiter of the field they are arriving at...

From FAA Order JO 7110.65T 2-7-2.c4
That certainly clears it up...cheers!!

[Chuck Barlow]

My rough math tells me that every .01 difference on the altimeter setting translates into roughly 10 feet of altitude change the pilot would be attempting to fly at. So let's suppose the GREATEST difference we'd expect do see in barometric pressure at KSFO vs. KSJC is like .03 or .04 inches of Mercury (e.g. altimeter settings of 30.01 vs. 30.05), which would be unusual. That's only an equivalent net difference of 40 ft altitude. Wouldn't really keep me awake at night.

Besides, once the KSFO traffic on GOLDN5 crosses LOZIT at 11,000 most of the time you are going to start descending them below 11,000 pretty soon after. While at the same point (after LOZIT) the KSJC traffic is presumably still on their way down to eventually cross DUXBY at 12,000.

[David Carman]

A/c must have an altimeter setting within 100 miles, and preferably their destination if it is close, as the 7110.65 suggests. Nothing wrong with giving them both the SFO one, except that you'd have to give the SJC guy the SJC altimeter at some point before he lands.

[Lucas Dziesinski]

Just a quick side every inch on a "inches of mercury" altimeter is one thousand feet. Every tenth of an inch is one hundred feet.

Personally, if the altimeter at KSFO is two tenths of an inch different (two hundred feet), I would give them KSFO, then later KSJC, like David said. So if KSFO was 29.92 and KSJC was 29.72 for example.

Adds to my safety net ;)

[Chuck Barlow]

Dude. If we EVER see real world conditions where KSFO & KSJC have .20 difference in altimeter readings, then close the airspace. We're talkin' hurricane winds.

[Charan Kumar]

LOL...well add to that the brilliant visibility and fog conditions that can change in our area in a moment's notice.

LD, that's kind of what I was leading to and yes I did mean to ask probably we should give the KSJC acft SJC Altimeter when departing SFO VOR...then again, my mistake was taking the 10th of an inch to the .01 of an inch.

[Lucas Dziesinski]

I use this as a general rule..doesn't have to be just in the bay. Shouldn't become fixated on certain airspace, etc, you should become familiar. That way you can apply your skills to every type of airspace/airport, what have you, not just one.