modesto2
Posts: 2671
Joined: Sun Jul 16, 2000 3:44 am

Sadde 6 Arrival

Tue Dec 19, 2000 5:07 am

Correct me if I'm wrong, but the arrival chart for Sadde 6 shows SMO 068 radial. However, ATC clears aircraft on the 070 radial. Why is there a discrepancy? Thanks.
 
Ralgha
Posts: 1589
Joined: Tue Nov 09, 1999 6:20 pm

RE: Sadde 6 Arrival

Tue Dec 19, 2000 6:09 am

ATC doesn't have to follow a STAR, a STAR is there to ease workload on ATC if they choose to use it. Often they will use it, but they will also often modify it facilitate the traffic flowl. 
09 F9 11 02 9D 74 E3 5B D8 41 56 C5 63 56 88 C0
 
timz
Posts: 6121
Joined: Fri Sep 17, 1999 7:43 am

Correct Me If I'm Wrong, But...

Tue Dec 19, 2000 8:38 am

...don't they actually clear them to depart SMO heading 070? (You recall that's not the same as the 070 radial.)
 
AAR90
Posts: 3140
Joined: Fri Jan 21, 2000 11:51 am

RE: Sadde 6 Arrival

Tue Dec 19, 2000 9:47 am

>...don't they actually clear them to depart SMO heading 070?

Correct. Why? I don't know... ATC just does it.
*NO CARRIER* -- A Naval Aviator's worst nightmare!
 
modesto2
Posts: 2671
Joined: Sun Jul 16, 2000 3:44 am

RE: Sadde 6 Arrival

Wed Dec 20, 2000 2:25 am

Could you please explain the difference between 070 radial and a 070 heading? Thanks!
 
Ralgha
Posts: 1589
Joined: Tue Nov 09, 1999 6:20 pm

RE: Sadde 6 Arrival

Wed Dec 20, 2000 9:15 am

Heading 070 means turn until your heading indicator shows you facing 70 degrees magnetic. Different types of airplanes use different types of heading indicators, but they all show magnetic headings.

Radial 070 is a bit more complicated. I'll assume that you don't know much about VOR stations in the following explanation, if you do know much about it, overlook what you already know 

A VOR station is basically a radio transmitter. A typical station, physically, is a low, round building, with a large cone shaped antenna sticking up out of the center, and a series of small antennas around the top perimeter of the building.

VOR stands for VHF Omnidirectional Range. The VOR station projects (transmits) straight line courses (radials) in all directions. Imagine a bicycle wheel, the VOR station is the hub, and the radials are the spokes (though in reality there are infinatly many radials).

For navigation purposes, we are only concerned with the radials that correspond to whole degrees, and we number them starting with 1, which is the radial that goes away from the VOR in the direction that is 1 degree east of magnetic north. We then number each radial according to it's corresponding degree value (from magnetic north).

Therefore, radial 070 is the radial that has a direction 70 degrees east of magnetic north, starting at the VOR station and proceeding away from it.

Hope this makes sense and is helpful  
09 F9 11 02 9D 74 E3 5B D8 41 56 C5 63 56 88 C0
 
timz
Posts: 6121
Joined: Fri Sep 17, 1999 7:43 am

More On The Difference

Wed Dec 20, 2000 9:41 am

Like he said, "070 heading" means the aircraft is pointed 70 degrees east of magnetic north. If there's no crosswind the aircraft will track the 070 radial, but if there is it won't.
 
Guest

RE: Sadde 6 Arrival

Wed Dec 20, 2000 11:52 am

My understanding is that ATC doesn't usually direct an aircraft to fly an odd heading (as opposed to a rounded heading, i.e. 160), such as 068. They just round it up to 070... For short distances, two degrees won't make much of a difference anyway.
 
timz
Posts: 6121
Joined: Fri Sep 17, 1999 7:43 am

Come To Think Of It...

Thu Dec 21, 2000 3:00 am

... I guess it's pretty common for the STAR to show a final track along a radial and the controllers to assign a heading instead. You recall that Modesto arrivals into SFO are invariably told to depart CEDES heading 230 or whatever, and HADLY arrivals usually depart HADLY heading 360, etc.

Who is online

Users browsing this forum: No registered users and 9 guests