abelenky

I'm a 141 student at BFI in Seattle, WA, which has a Class D airspace underneath SEA's Class B, and right up against Renton's Class D.

While I understand the general shape of BFI's airspace, I was looking for a *precise* map and description of it. Unfortunately, on the TAC chart, the segmented blue line is partially obscured by the clutter of the neighboring and overhead space and all the other chart notations.

I've looked and looked, for either an uncluttered map of the space, or for a text description of the boundaries, so far to no avail.

Do you have any advice on how and where to find more exact answers regarding the details of the airspace?

-abelenky

waflyboy

Very interesting observation! I did a little flying in this area for my private several years ago, but apparently never really noticed this....

Another thing I noticed: there appears to be a 5nm class D ring around KSEA for the airspace below 3000', excluding the class B. I don't think I've seen that anywhere else.

Practically speaking, the information on the TAC should tell you all you need to know: it's probably a good idea to talk to ATC whenever you're close to their airspace boundaries. If you're looking for an academic answer, you might see if you can take a tower tour at BFI and ask a controller or the facility manager. Certainly they know the exact dimensions of their airspace and might be able to tell you about any agreements they have with the neighboring towers with regard to handling VFR aircraft.

If you do get to take a tour, let me know... I might try to tag along!

woodfinx

When they finish this stupid investigation for the Kid Controller at NYC, I'd see if you couldn't arrange a visit to the BFI tower...or SeaTac or Renton for that matter.

The controllers there will most likely be able to show or provide you with a detailed airspace map and you would get to experience a controller's perspective. They may still be able to provide you with something like an airspace map even though you can't visit the facility, but I guess they'd have to walk it out to the gate.

Singlecoil

That's an excellent link you provided there. It looks like you or someone has all the points that define the airspace mapped out with lat/long coordinates. That's probably the best way to go as that is easy to program into a GPS. The actual description is likely to be pretty long, almost like a legal description for a piece of property.

abelenky

In the link I provided in my original message, I highlighted the airspace as best I understand it.

But if you clear out the highlighting, you'll see that parts of the segmented blue aren't actually on the chart, due to chart-clutter.

I'm particularly interested in whats known as the Valley Arrival, from the south, since a little too far east, and you're over Renton's field, and a tiny bit too far west and you're in Seattle's Class B. It looks like a very narrow "gate" for a new VFR pilot to hit.

USMCFLYR

In the good old days of real pilotage I would agree that it make make for a challenge. In today's world of moving maps and GPS - I would think it is as easy as following the golden brick road

USMCFLYR

abelenky

I don't have GPS. I'm flying 6-pack, pilotage and DR. Occasionally I get to use VORs.

waflyboy

Roughly speaking, you can see that I-5 is too far west, and WA-167 is too far east. Personally, if I was going to fly into BFI from the south (say, from Auburn), I'd probably just follow the railroad tracks up the valley at 1,500'MSL. That would keep you right between SEA and RNT airspace and set you up nicely for a straight-in landing north or a left downwind landing south. I'd still talk to SEA approach though.

It sounds like fun actually.

USMCFLYR

I LOVE IT! Congrats.
I use to fly an airplane with INS, backed up by GPS and *usually* with moving maps and it was all I could do to get a student to LOOK OUTSIDE the canopy. I had a guy once start flying off towards Fresno on a departure out of Lemoore that he had flown many, many times before because the system (which had a wrong waypoint entered) told him to fly that way. Total lack of SA of the bigger picture You might not feel like it, but I think you are better off at least initially learning this way, and then make a transition at a later time for greater SA and safety. Then you will be able to merge the two skills together. Best of luck and be careful flying out there. Btw - I think the ideas of visiting the towers involved and getting ATC's input on this question are great ideas. The times that I have gone to ATC facilities they have been very helpful answering any and all questions.

USMCFLYR

abelenky

I sat down with my instructor to go over my airspace questions, and learned some interesting things, summarized here:

• Where a segmented blue Class D line isn't visible, its assumed to follow a higher level (Class B or Class C) boundary above it.

• The "Class D" around SEA (SeaTac) really implies, "If you want to fly beneath our Class B space, staying clear is NOT enough. You have to establish 2-way comms as well." Unlike most Class D spaces, they won't let you to the airport. Instead, they just want to be able to talk to low-level VFR craft in close proximity to their space.

• The boundaries on the map of airspaces can be, and in this case, are quite different from what the controllers understand and go by. Even though BFI's airspace goes right next to Renton's field, if you get that close to Renton without contacting them, they will likely get mad at you. Even though the map shows a dividing line between BFI and RNT out in the water, both towers seem to operate as if the shoreline separates their airspaces.

Overall, it seems the map is a guide, but no substitute for local knowledge and talking with experienced pilots and controllers, who may only be going by the maps in a loose sense.