Author Topic: JFK need to fix their Altimeter Settings  (Read 11113 times)

Offline philip

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JFK need to fix their Altimeter Settings
« on: June 29, 2008, 03:50:43 PM »
I've been listening to JFK for a few hours and noticed when the woman for tower says the altimeter it's 29.81 and when the guy on the 13's says it that it's 29.83 and when it changed later on, her's was 29.77 and his 29.79...
That's like an error of 52 feet or somethin...is that normal because of the runways they are controlling being in different areas? :)
Oh and here's a cool webcam with sound for times square I just found so I can see the weather
http://www.earthcam.com/usa/newyork/timessquare/



Offline cessna157

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Re: JFK need to fix their Altimeter Settings
« Reply #1 on: June 29, 2008, 05:03:47 PM »
JFK may be a moderate sized airport, but I don't think a hurricane has a pressure differential of .02" in the area equal to JFK.  Their altimeters should read the same.  But, as what seems to be usual for anything at JFK, LGA, or the NYC metro airspace, they don't live to the same standards as the rest of the country.  They get to make up their own rules quite frequently.

Also, the difference between 29.77 and 29.79 would be 20 feet, not 52.

Offline moto400ex

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Re: JFK need to fix their Altimeter Settings
« Reply #2 on: June 29, 2008, 05:59:28 PM »
Actually its more like 18.6 feet at sea level. :wink:  Not sure if its different for air carriers but as long as your indicating within 75 feet of the field you are good to go.

camrnlendy

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Re: JFK need to fix their Altimeter Settings
« Reply #3 on: June 29, 2008, 08:27:25 PM »
The difference is because of the DASI correction reading.  If the DASI correction is -0.2, you subtract .2 from the altimeter and give that.  I really don't know how it works, but some controllers use the correction and some don't.  There is no direction from the Agency on whether or not it needs to be used.  That is why you heard one controller give one setting, and another give a different setting.  Its just one of those things that Agency does not address or care to make standard to this day.

Offline NY Z Pilot

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Re: JFK need to fix their Altimeter Settings
« Reply #4 on: June 30, 2008, 10:56:15 AM »
in the tower you have an IDS computer, which shows the current ATIS, and other info about the airport (notams) etc...

theres also a DASI which shows the current altimeter. One of them could have been reading it off the DASI, the other off the IDS. Its common that the altimeter goes up/down within the hour of an ATIS report.

Offline iskyfly

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Re: JFK need to fix their Altimeter Settings
« Reply #5 on: June 30, 2008, 12:42:28 PM »

 U.S. DEPARTMENT OF TRANSPORTATION
FEDERAL AVIATION ADMINISTRATION
 ORDER
JO 7210.3V
Effective Date:
February 14, 2008
 
         
Subject:  Facility Operation and Administration
 
 
Section 10.  Wind/Altimeter Information
 

See sections 2-10-3 and on

http://www.faa.gov/airports_airtraffic/air_traffic/publications/atpubs/FAC/Ch2/s0210.html

Offline aviator_06

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Re: JFK need to fix their Altimeter Settings
« Reply #6 on: June 30, 2008, 03:52:16 PM »
cool.

Offline moto400ex

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Re: JFK need to fix their Altimeter Settings
« Reply #7 on: June 30, 2008, 09:13:50 PM »
I think aviator 06 wanted to get to 100 posts today. (I might go for 300 so watch out.) :lol:

Way to bump everything out of order.

Offline Lezam

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Re: JFK need to fix their Altimeter Settings
« Reply #8 on: July 01, 2008, 05:01:56 PM »
I might go for 300 so watch out

Yeah, that wouldn't be too pretty  :)

Offline philip

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Re: JFK need to fix their Altimeter Settings
« Reply #9 on: July 01, 2008, 05:13:02 PM »
Oh my mistake lol...I'm thinking in Millibars from the UK that 1 millibar = 28ft LOL...We seem to have a mixture of Metric and imperial...

Offline KSYR-pjr

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Re: JFK need to fix their Altimeter Settings
« Reply #10 on: July 01, 2008, 05:40:10 PM »
Oh my mistake lol...I'm thinking in Millibars from the UK that 1 millibar = 28ft LOL...We seem to have a mixture of Metric and imperial...

You are in good company.  Rocket scientists have been known to make that mistake as well, but the consequences of their mistake was an order of magnitude larger, say for example the loss of a USD $125 million Mars Lander.

Offline Switch Monkey

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Re: JFK need to fix their Altimeter Settings
« Reply #11 on: July 01, 2008, 11:00:42 PM »
Oh my mistake lol...I'm thinking in Millibars from the UK that 1 millibar = 28ft LOL...We seem to have a mixture of Metric and imperial...
]the loss of a USD $125 million Mars Lander[/url].
Child's play when compared to the loss of an French Ariane 5 rocket because software problems, a USD $500 million loss! oops another rocket scientist mistake.

Offline KSYR-pjr

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Re: JFK need to fix their Altimeter Settings
« Reply #12 on: July 02, 2008, 06:55:28 AM »
Child's play when compared to the loss of an French Ariane 5 rocket because software problems, a USD $500 million loss! oops another rocket scientist mistake.

Was that particular loss also due to a mix-up of metric and English units?

Offline cessna157

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Re: JFK need to fix their Altimeter Settings
« Reply #13 on: July 02, 2008, 09:39:09 AM »
Rocket scientists have been known to make that mistake as well, but the consequences of their mistake was an order of magnitude larger, say for example the loss of a USD $125 million Mars Lander.

Sheesh, I forget to carry the 4 just once and hear about it for years!    :evil:

Offline Unbeliever

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Re: JFK need to fix their Altimeter Settings
« Reply #14 on: July 04, 2008, 12:40:31 AM »
Child's play when compared to the loss of an French Ariane 5 rocket because software problems, a USD $500 million loss! oops another rocket scientist mistake.

Was that particular loss also due to a mix-up of metric and English units?

Nope.  A variable overflow problem.  64 bit floats don't fit well into 16 bit integers.  Primary string popped an exemption of "I can't handle this" and tried to transfer control to the secondary string.  The secondary string, however was running the same code and had already shut itself down on the same error. 

That same code worked well on the Arianne 4, but the velocities were much larger on the Arianne 5.

--Carlos "JPL ALWAYS does metric, why did Lock-Mart think any different" V.