Class D airspace question.

[BushwickBill]

Quick question on class D airspace. Is there a set distance? Or is it up to the individual airport?

Yes I ran a search. The first result was "will pilots be replaced by UAV's?" I don't get on with flightinfos' search engine.

Here is the situation. On a visual into an busy airport without an approach control I checked in a 4.5 miles. The radio was out of control busy. 6 aircraft in the pattern, loads of them don't speak english very well. Corporate mixing with training aircraft. Nightmare. Captain says I checked in inside of airspace. I always thought class d was 4 miles but I can't find a set distance in the FAR. Checked 91.129.

Thanks for your time...

 

[erj-145mech]

You may have been inside the Class D whne you contacted the tower, or you may not have been. Generally, and I use the term loosely, the diameter is 4 miles, but there may be extensions for IFR approaches. This is from the AIM:

3-2-5. Class D Airspace
a. Definition. Generally, that airspace from the surface to 2,500 feet above the airport elevation (charted in MSL) surrounding those airports that have an operational control tower. The configuration of each Class D airspace area is individually tailored and when instrument procedures are published, the airspace will normally be designed to contain the procedures.
b. Operating Rules and Pilot/Equipment Requirements:
1. Pilot Certification. No specific certification required.
2. Equipment. Unless otherwise authorized by ATC, an operable two-way radio is required.
3. Arrival or Through Flight Entry Requirements. Two-way radio communication must be established with the ATC facility providing ATC services prior to entry and thereafter maintain those communications while in the Class D airspace. Pilots of arriving aircraft should contact the control tower on the publicized frequency and give their position, altitude, destination, and any request(s). Radio contact should be initiated far enough from the Class D airspace boundary to preclude entering the Class D airspace before two-way radio communications are established.
5. Aircraft Speed. Unless otherwise authorized or required by ATC, no person may operate an aircraft at or below 2,500 feet above the surface within 4 nautical miles of the primary airport of a Class D airspace area at an indicated airspeed of more than 200 knots (230 mph).
c. Class D airspace areas are depicted on Sectional and Terminal charts with blue segmented lines, and on IFR En Route Lows with a boxed [D].
d. Arrival extensions for instrument approach procedures may be Class D or Class E airspace. As a general rule, if all extensions are 2 miles or less, they remain part of the Class D surface area. However, if any one extension is greater than 2 miles, then all extensions become Class E.

 

[time builder]

ERJ mech. got to it first, so I'll edit my response:

So, in answer to your question, it depends on the airport. They can designate further out, but my experience is that if they are extending controlled airspace for an approach, they usually designate it class E.

 

[BushwickBill]

Niiiiiiiceeeeeeee

Cheers - I owe you guys a beer.

 

[atldc9]

I'm gonna be a smart ass, so take this with tongue-in-cheek. You could always look at the chart for the airport you are going into to. Even the Jepp L charts show the Class D shape and size.

 

[Mr. Irrelevant]

If you were 4.5 s.m away, you probably called in the airspace. If 4.5 nautical, you were probably outside. Ring is typically 4.4 nautical miles or 5 statute miles from the center.

Mr. I.

 

[FL420]

A little ancient history here.

Before all the airspace was reclassified to make our fellow ICAO members happy, I suppose, airspace around airports with control towers were called Control Zones with lateral dimensions of 5 statute miles(plus IAP extensions) and vertical dimension of surface to, but not including, 2500' AFL. People complained for years about the use of statute miles for distances when everbody used nautical miles for navigation. DME distances were expressed in NM instead of SM.

I guess when they reclassified the airspace they changed the regulation to read 4 NM instead of 5 SM so the distance never really changed but the wording did. Apparently they decided to ignore the fact the visibilities and cloud clearances were still expressed in SM instead of NM. Go figure.

 

[PURPLEHAZE21]

Not to be a Smart -Ass but I believe the AIM States "General" dimensions, but ends the statement with "or as depicted". This means what you see on the chart or map. I have seen class D be only 2-3 miles in certain portions. If you look at a sectional you can probably find other airports which dont meet the criteria (NY sectional) good luck.

 

[pilotsh]

On the flipside of what Purplehaze said, some Class D airspace is much larger than the typical. One example is BMI (bloomington, IL). My guess is that there isn't enough traffic to deem it a Class C, but the type of traffic and the airports around BMI facilitate the need for a much bigger Class D. Just eyeballing it, it looks about 6-7 miles in diameter.

 

[Flymach2]

Hi,

Class "D" airspace is determined by a simple formula. This formula is located in FAA Order 7400.2F. The dimension is determined by measuring the distance from the ARP,(Airport Reference Point), to the end of the furthest runway then dividing that distance by 6076. Then by adding 3.5, this will give you the radius for that specific airport. Hope this helps.

Regards