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Why Does Ksea Have Class D Airspace  
User currently offlineQxeguy From United States of America, joined Nov 2003, 81 posts, RR: 0
Posted (10 years 4 months 1 day 18 hours ago) and read 7995 times:

They are also (for those that don't know) the primary airport surrounded by Bravo airspace. Why do they have both?

Some possibilities..
History..it had D (or the D equivalent) long ago, pre bravo, and they just kinda kept it. But why?

Proximity..very close to 2 other converging class D airports (BFI and RNT). But wouldn't the B still take care of that?

Because it has a tower..and as a general rule, if you have a tower, you have D. I have been too lazy to get my other sectionals to see if other major airports in B airspace also have D, but I don't remember seeing any. I am sure there are others.

Any help in answering this would be wonderful. It has been bugging me for years.

[Edited 2005-06-16 04:15:36]

I fly boxes. Boxes don't bitch. Boxes don't barf. Boxes don't get drunk and do a number 2 on the beverage cart.
7 replies: All unread, jump to last
User currently offlinePilawt From United States of America, joined Dec 2003, 103 posts, RR: 0
Reply 1, posted (10 years 4 months 1 day ago) and read 7925 times:

You can't have Class B and D existing simultaneously in the same airspace, but a Class D may (and often does) exist below the floor of Class B.

Class B airspace extends from the surface to 10,000' at KSEA. The Class B floor rises incrementally to the outer edge of the area, in an irregular circular shape up to 30 NM from SEA VORTAC, but the top is 10,000' over the whole area. Class D does not exist at KSEA itself. Class D airspace exists to 5-NM radii around KBFI and KRNT from the surface to the floor of KSEA's Class B or to 2,500' MSL, whichever is lower. The Class D airspaces around KPAE, KTIW, KTCM and KGRF also underlie the KSEA Class B, but the tops of those areas do not extend high enough to reach the Class B floor.

If all the satellite airports were included in Class B airspace, it would be an ATC nightmare, as each aircraft would require Class B clearance and separation. VFR operations at the satellite airports would be much more difficult.

Class D can also exist under the floor of Class C, such as at Pearson Field in Vancouver, WA (KVUO), where Class D exists below the floor of the Class C area of KPDX. KVUO, by the way, is an example of Class D at an airport where there is no tower at all. (KVUO is also the nation's oldest active airport, and will celebrate the centennial of its first aircraft operation on 24 September 2005.)

User currently offlineHaveBlue From United States of America, joined Jan 2004, 2160 posts, RR: 1
Reply 2, posted (10 years 4 months 16 hours ago) and read 7866 times:

We have 2 very recent additions here at DAB. The OMN airport within the last year and a half and EVB within the last few months both became Class D airports below the umbrella of DAB's Class C.

Here Here for Severe Clear!
User currently offlineQxeguy From United States of America, joined Nov 2003, 81 posts, RR: 0
Reply 3, posted (10 years 4 months 15 hours ago) and read 7868 times:

Thank you for your response, but it didn't answer my question at all (incidently Seattle Tower and Boeing Tower don't know either..it is called "the great mystery" by both)

Check the Seattle Sectional..better yet the Seattle Terminal Chart...SEA, BFI and RNT have converging Class D. It is depicted by a dashed blue line. I fly out of BFI, and I can tell you that although the surface area of Seattles Bravo is clearly Bravo, SEA certainly does have an outer ring of Delta. I am wondering why D exists there at all.

I fly boxes. Boxes don't bitch. Boxes don't barf. Boxes don't get drunk and do a number 2 on the beverage cart.
User currently offlineRalgha From United States of America, joined Nov 1999, 1614 posts, RR: 5
Reply 4, posted (10 years 4 months 15 hours ago) and read 7864 times:

It's so you can't bust in real close to the airport without talking to anyone. The inner circle of B at Seatac is less than 4 NM radius, so they fill out the remainder with D.

09 F9 11 02 9D 74 E3 5B D8 41 56 C5 63 56 88 C0
User currently offlineOPNLguy From , joined Dec 1969, posts, RR:
Reply 5, posted (10 years 4 months 14 hours ago) and read 7858 times:

You might try calling SEA ARTCC during M-F biz hours and ask for "airspace and procedures"...

User currently offlinePilawt From United States of America, joined Dec 2003, 103 posts, RR: 0
Reply 6, posted (10 years 4 months 4 hours ago) and read 7816 times:

Whoa, you're right ... I completely missed that outer ring on the chart, and missed the whole point of your question. Sorry.

That's why I usually file IFR when going into BFI; so I don't have to worry about all those sneaky little lines.  blush 

User currently offlineHAL From United States of America, joined Jan 2002, 2606 posts, RR: 52
Reply 7, posted (10 years 3 months 3 weeks 5 days 2 hours ago) and read 7679 times:

If you look at the chart, you can get within a mile of Sea-Tac airport to the northeast and still be outside the class B airspace. They did that because of the concentration of general aviation traffic coming in and out of Boeing field. However since both Sea-Tac and Boeing are 24-hour tower controlled fields, they still have class D airspace around them to the normal distance of about 5 miles to ensure the required visibility, cloud clearance, and communication regulations are met. That class D airspace includes all the area that isn't taken up by the class B airspace. So even though you can fly up the Auburn valley at 1500 feet within 2 miles of Sea-Tac and not enter the class B airspace, by the time you pass the south end of the field you're in class D airspace and had better be talking to one of the towers (Sea-Tac, Boeing, or Renton), and be following the class D visibility and cloud clearance requirements.


One smooth landing is skill. Two in a row is luck. Three in a row and someone is lying.
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