14.12 Can anyone tell me what a procedure turn is?
From FlightSim
A procedure turn is a published (on the approach charts) procedure to align the aircraft with the final approach course, typically used when the inbound course to the final approach fix is not approximately aligned with the course and, depending on terrain, obstructions, etc. may be left or right. For example if the final approach course is 350º and you arrive at the fix on a course of 125º, you need a mechanism to line up.
Typically, you proceed outbound on the inverse of the approach course for one minute, 45 deg. turn, go for one minute, 180 deg turn away from airport. This gives a 45 deg. intercept angle to the approach course. Then intercept the approach course and fly the approach. All turns are standard rate, not to exceed a 30 degree bank angle (of course this is generally true of IFR flight). A standard rate turn is the 2 MIN marking on the turn coordinator (takes 2 minutes for a 360).
A more specific example might be, given a final approach course of 350 degrees, to track outbound (170 degree course) on the navaid being used for the approach for one minute, then a standard rate turn to the left (if that's what is published) for a HEADING (no wind) of 125º. Fly for one minute then turn RIGHT (away from the field) 180 degrees back to a heading of 305º. This puts you on a 45 degree intercept to the 350 degree inbound course.
Now you can intercept the navaid and fly the approach. Some published approaches will specify no procedure turn authorized, so they are not to be used in that case. In today's radar environment in the US, radar vectors usually (not always) are used instead. This procedure may be used for any type of approach for which it is published -- VOR, NDB, ILS, etc.
If my rust is showing, additional input is welcomed. If the big iron has modifications, I'd appreciate that input also.
Larry N.
I'll take a stab at the explanation:
1. A Procedure Turn is designated so as it is a well defined procedure which
when followed allows a method to reverse course in order to intercept the the ILS LOC or Inbound course(non-precision approaches i.e. NDB). There are two procedures: Most common and most used is the 45/180, the second and most challenging is the 80/260( the comments below are geared to the 45/180 as it is the most common. The 80/260 is another beast).
2. The 'procedure' is as follows:
- Establish the aircraft on the outbound segment which is 180 deg
opposite of the inbound course. This is started from the IAF (initial
approach fix), and is generally the NDB associated with the appr.
- Initiate a 45 degree turn in the direction indicated on the plate, and
start timing. This segment should be flown for 1 minute (light aircraft
with appr speeds of 120kts or less or 1 minute 15 sec for a/c with
higher appr speeds. The speed referenced is 1.3 times the stall speed)
- At 1 minute, begin the 180 degree turn back to intercept the inbound
course. The 180 turn is initiated opposite direction of the 45. I.e.
if the 45 was to the left, the 180 will be to the right.
Note: the 180 turn must be completed within the defined distance. It's
specified on the appr chart, and is typically 10nm
- Once you roll out on the intercept heading (after 180 deg of turn),
fly this hdg for 1 minute and then turn to the desired final appr
course. If intercepting the LOC, this can occur something less than
1 minute, so watch the gauge.
- Altitude restrictions apply. On the plate for the approach there will
be a circle indicating MSA(minimum safe altitude). This is generally
a radius of 25nm from the IAF, and you should be at or higher until
the turn back to intercept the inbound course is initiated. You can
begin your descent in the 180 turn to the initial appr altitude, and
once the IAF is reached again inbound, begin the descent to DH
(decision height). In the case of ILS, you will have GS guidance.
I don't do a good job of putting it all together so I'm sure I've misspoken or led to some confusion on the above. But hopefully it illustrates the base elements of the Procedure Turn, and from this you can understand the term 'Procedure'.
There will be other pilots responding, and probably with clearer explanations.
Joe W. Clemmons,jr
From any direction, say, you come over an overhead/near overhead beacon..
Say, after entering hold procedure over that beacon,
Imagine you leave overhead position of any Navaid(VOR/ADF) which is on the apt on 090deg when the Landing rw is 27. Say you maintain 1500ft AGL. At a comfortable speed with initial set of flaps. Go to about 10 miles on 090 radial/track or to a beacon located at that point. At that point say turn right Hdg135deg fly for a minute or two. Turn left on to 315deg.
If you just plot it , you will find that you are in just near ideal conditions to intercept the ILS for Rwy27. In bad weather, in the absence of radar etc, this procedure gets you on the ILS neatly.
Hence this is called a procedure turn. On similar principle the exact pattern may vary from place to place and is given in the Inst App Charts for that rwy. ATC just has to tell you the procedure and you know what to do. It generally forms part of a complete Inst App Procedure. With a continuously descending height segments, successive a/c can be safely released from the holding pattern for the conduct of ILS.
Simplest of all the procedure turn is what you do just after T/O if you HAVE to land Back when there are no cross runway etc. Turn to either side by 90 deg ,reverse to otherside by 270 deg you are on finals again in opposite direction. you are following a set procedure.
In the absence of radar etc, similar procedures as Larry has elaborated, depending on environment is prescribed for each airfield, by which any number of a/c in a sequence can leave the holding pattern in succession, controlled by the ATC, leave the VOR/NDB etc outbound, turn around and be on finals in a most efficient and safe manner. So everyone would be following a set procedure.
Bala
