What is a two- or three-mile base exactly?

falstro
  • What is a two- or three-mile base exactly? falstro

    I frequently hear the tower instruction

    Report a two mile base for runway 5

    What is the intention of that instruction? I realize that under these circumstances that we're not looking for pinpoint precision, but still it would be nice to know.

    For the record, I'm not asking what a base is (or the fact that "left" is implicit), but what two miles are we talking about? Two miles straight line distance from the threshold? A base to a two mile final? On the base leg, two miles from the centerline? (I'm pretty sure the last one isn't it, but hey, I've been wrong before)

  • They basically ask you to report it as a "memory jogger" for themselves so that they can do something when you call in (like clear you to land).

    A standard airport traffic pattern is described in Chapter 7 of the Airplane Flying Handbook as:

    The downwind leg is a course flown parallel to the landing runway, but in a direction opposite to the intended landing direction. This leg should be approximately 1/2 to 1 mile out from the landing runway, and at the specified traffic pattern altitude. During this leg, the before landing check should be completed and the landing gear extended if retractable. Pattern altitude should be maintained until abeam the approach end of the landing runway. At this point, power should be reduced and a descent begun. The downwind leg continues past a point abeam the approach end of the runway to a point approximately 45° from the approach end of the runway, and a medium bank turn is made onto the base leg.

    It looks like this:

    AIM Traffic Pattern

    When the tower asks you to fly a two mile pattern, they want you to fly a pattern that has the downwind leg 2 miles out from the runway instead of the 1/2 to 1 mile that is normal. The base leg would still be turned when 45° from the approach end of the runway.

    In this case, you are either:

    1. Doing pattern work in which case you fly the two mile wide pattern and should report turning base, or
    2. Approaching the airport and the controller would like you to enter the two mile wide pattern on the base leg. You should report the point where you would have normally turned onto the base leg if you were flying the entire pattern (45° to the runway). This would actually be both of your last two scenarios above: Established on the base leg, two miles prior to intercepting a two mile final (which for fun would actually be 2.83 miles from the runway).

Related questions and answers
  • I frequently hear the tower instruction Report a two mile base for runway 5 What is the intention of that instruction? I realize that under these circumstances that we're not looking for pinpoint precision, but still it would be nice to know. For the record, I'm not asking what a base is (or the fact that "left" is implicit), but what two miles are we talking about? Two miles straight line distance from the threshold? A base to a two mile final? On the base leg, two miles from the centerline? (I'm pretty sure the last one isn't it, but hey, I've been wrong before)

  • and told him about it because I was told to "report 3 miles out", not "report 3 mile base." I completely understand that I made my base leg too wide and that caused me to deviate from an ATC instruction..., I established contact with the tower and was told to "enter left base, runway 7, report 3 miles out." I interpreted the "report 3 miles out" as to give the tower a call when I was 3 miles away from... apparently I made it a little too wide because the GPS did not indicate I was 3 miles from the field until I was on final. At this point, I called the tower, reported I was on a 3 mile final and was given

  • are two examples of situations where it would be very useful, and both are real life clearances that I have gotten multiple times: Example 1 - KASE Clearance: N1234, Cleared for the VOR/DME-C approach, cleared to land runway 15 If you follow the step downs until the final approach fix (ZIGBU) you will be at 2,983 ft. above the runway (10,820 ft. MSL) with 2.9 miles to go (9.61 degree... Runway 6 Circle Runway 1 Approach, cleared to land runway 1 If I fly the ILS (localizer and glideslope) until reaching circling minimums, especially in a category C or D airplane

  • to another airport that is within 25 nautical miles from the airport where the student pilot normally receives training The student must be endorsed with something along the lines of: I certify that (First name, MI, Last name) has received the required training of section 61.93(b)(1). I have determined that he/she is proficient to practice solo takeoffs and landings at (airport name... (b) Authorization to perform certain solo flights and cross-country flights. A student pilot must obtain an endorsement from an authorized instructor to make solo flights from the airport where

  • An aircraft's Aircraft Communications Addressing and Reporting System uses line of sight HF via ground stations or satellites to communicate with its base station. This system allows for three... are used to communicate between the aircraft and its base. Various types of messages are possible, for example, relating to fuel consumption, engine performance data, aircraft position, in addition to free text. So, questions: Can ACARS be turned off? Would this generate a warning at the base station? Can ACARS send postion, altitude and heading information automatically? Can ACARS be repeatedly

  • In a flight database that I'm working with on a project, there is a column of data called "flightCategory" with values "C", "G", "T", etc. Any idea what those actually mean? From what I understand, the database is from FAA. But I'm not 100% sure.

  • miles from a VOR. Therefore, when you're within those 22 miles, there's no practical difference between a MEA and a MOCA, right? If that's true, why is there an 1800 foot difference between...As we all know from our instrument training, the MOCA is: MINIMUM OBSTRUCTION CLEARANCE ALTITUDE (MOCA)- The lowest published altitude in effect between radio fixes on VOR airways, off-airway routes, or route segments which meets obstacle clearance requirements for the entire route segment and which assures acceptable navigational signal coverage only within 25 statute (22 nautical) miles

  • a simple explanation of the above case. Edit: I am attaching two screen shots of two sets of equations from two sources. Links to the books are included below. Both sources state... for a small exercise. I understand the control part and its implementation. What I do not grasp is how one acquires the longitudinal equations of motions (which are then used for the control part) which serves as the starting point. What is the starting point or what are the principles used to derive these equations? If I know how to derive these equations for a very simple case, then I know I have

  • Primary target: An aircraft not reporting mode-C, the only thing the controller has is the return on the radar. When a controller reports a primary target as traffic to other aircraft, the controller does not have the altitude of the target. Given this, I conclude that ATC radar does not have the altitude (angle-up) to the target, and only provides azimuth. So then without the altitude, how does the radar-system know where to put the target laterally on the screen? Example, a radar picks up a target that is 10 miles from the station. If the target is 0 AGL, the proper position would be 10

  • Why is it that black boxes don't float? From what I gather the answer is: So they will not float away from a water crash site. The ping can be heard underwater with sonar. Finding the ping, finds the site. But why not have two black boxes one that floats and one that stays with the aircraft? That way if a plane is lost at sea, if we find the black box floating, we could use the data to find the other black box and the crash site. Plus the benefits of having a redundancy are enormous.

Data information