Holding patterns revisited

25.10.2004

Submission:

Reference Pans-Ops Attachment C 3.4 Area reduction for holding and racetrack procedures.

a) In chapter 4, page 3-26, Fig III-4-8, says FTT of 11 sec. Att.C, 3.4 and Fig III-C-17 says nothing about FTT, why?

b) I suppose there must be a 2.5 NM secondary area behind the " wind-spiral" constructed in Fig. III-C-17?

c) Can one use the same method as described in Att C, 3.4 for reversal procedures ( for example for a baseturn)?

Ingar Lie NATAM ( PANS-OPS SECTION ) Norway

Answer or Commentary:

(I.W:

I will try to answer this one as best as I can but it is not an easy one.

a.) In chapter 4 the flight technical tolerance (FTT) is listed as:-

10 seconds timing tolerance

5 seconds bank establishment time

6 seconds pilot reaction time

21 seconds total FTT

If ever you have the excitement of constructing a racetrack template manually you will notice that the beginning of the turning spirals associated with the turn onto the inbound track are positions i2 and i4 (Attachment C figure III-C-6). The distance from g to i2/i4 is (t+21)v ,line 15 table III-C-4. The 21 in the formula is the FTT even though it is not mentioned as such and is included in the holding template. Also notice that an additional 11 sec after the nominal turning point "a" is used to define point "c" which is used in the construction of the wind spiral (refer Attachment C figure III-C-6). These 11 seconds is the pilot reaction time and bank establishment time. When you are constructing the holding area as in figure III-C-17 the aircraft is turning at a fix, so you can ignore the 10 seconds timing tolerance. The construction text for this area says in many places "Place template point "a" on....... and draw curve.....". In so doing you are automatically adding the FTT (5sec + 6sec), as it is included in the template design.

b.) Yes you are right a secondary area should be added as stated in paragraph 4.6.7.

c.) I think you can use the same principle for a base turn. In chapter 4 figure III-4-8 a racetrack is shown with a limiting radial or DME. Notice the intersecting tolerance and then the 6sec + 5sec.

For a base turn, chapter 4 figure III-4-8 shows a base turn with a limiting radial or DME so it is not excluded by Pans-Ops. This diagram also shows the intersecting tolerance and then the 6sec + 5sec. In this case you would have to use the same principle as for a racetrack holding. This would mean that you would have to place the RACETRACK holding template point "a" on the DME tolerance and using the first wind spiral define the outer area. It would have to be the racetrack holding template as the first wind spiral of this template includes the 11 seconds that is required for pilot reaction time and bank establishment time.

Any other thoughts in this area would be appreciated.)