ILS Cat III

06.10.2005

Submission:

I am trying to determine whether its safe to say that CAT III operations are feasible given that I have an obstacle (the control tower) located in the missed approach segment that yields a CAT II OCA/H of 250m/49m respectively. I have read through Annexes 6 and 14, JAR-OPS, Doc 9365 and even U.S. criteria. I have also had conversations with pilots who fly CAT III procedures but I am still a bit unclear/concerned about certain aspects of CAT III operations.
8168, Vol II, paragraph 21.4.10.2 states that:
Category III operations may also be permitted with a CAT II OCA/H between the height of the inner horizontal surface and 60 m provided the Annex 14 Category II inner approach, inner transitional and balked landing surfaces are extended to protect that OCA/H.
I extended the surfaces to 60 m and they are all clear. So according to PANSOPS I should be able to conduct CAT III operations
ICAO seems to get fuzzy after that.
Annex 6, paragraph 4.2.7.1 states that:
The State of the Operator shall require that the operator establish aerodrome operating minima for each aerodrome to be used in operations, and shall approve the method of determination of such minima. Such minima shall not be lower than any that may be established for such aerodromes by the State in which the aerodrome is located, except when specifically approved by that State.
Note.- This Standard does not require the State in which the aerodrome is located to establish aerodrome operating minima.
Annex 6, paragraph 4.2.7.2 states:
The State of the Operator shall require that in establishing the aerodrome operating minima which will apply to any particular operation, full account shall be taken of :
and then goes on to list numerous considerations of which
obstacles in the approach and missed approach areas and the obstacle clearance altitude/height for the instrument approach procedures (4.2.7.2 f) is one.
So it is up to each operator to come up with its aerodrome operating minima. I know of at least one state that places additional restrictions i.e. the CAT II OCA/H shall be less than 100 ft in determining whether CAT III operations are feasible. It seems like they are a bit uncomfortable with the idea and CAT III operations would not be allowed in my case even though PANSOPS allows for it.
I guess my questions are as follows:
1. Has it been your experience that this is a common situation i.e. extending the appropriate Annex 14 surfaces in order to get CAT III? Does it seem like the prudent thing to do...or is this strictly an operator decision and I should mind my own business.
2. JAR-OPS, Sub-Part E goes into great deal about CAT III DH/No DH, RVR values, Fail-Passive/Fail-Operational but I am still a bit unclear of HOW, with an emphasis on the how, the operators determine their CAT III operating minima [I know there is no OCA/H associated with CAT III operations (8168 Part III, chap, 21, paragraph 21.1.4)]. For example, what is the determining factor(s) for establishing a DH or not having a DH. In a situation like mine what is to limit the operator to CAT IIIA, why not CAT IIIB? Does the majority of the determination shift from an obstacle-based decision to more of an aircraft/aircrew/airport capability for CAT III operations?
3. What mechanism is in place for me, as a procedure designer, to let the operators know about obstacles that penetrate the OAS surfaces or at a minimum what obstacle drives the CAT II OCA/H. If there is not a mechanism should there be or should I as a procedures designer even worry about it. It just seems reasonable that the operators have as much information as possible when determining their CAT III operating minima.
I understand that this issue was a WP for a past OCP meeting but do not know if anything ever came of it.

Just strikes me as a little strange that with less than optimum CAT II minima (163/49m) Cat III operations can be done as long as certain Annex 14 surfaces are extended and clear. I do not even know how the operators determine that they can even try for CAT III if they do not know:

A About the exception in PANSOPS (21.4.10.2) or,
B If the procedure designer checked the extended Annex 14 surfaces in the first place

William Frenz - Procedure designer
Center for Advanced Aviation System Development (CAASD) - USA

Answer or Commentary:

(I.W.

1. Usually for Cat III operations you have Cat II operations with the most critical obstacle being the ground plane.
2. Could some of the pilots and operational people answer this one?
3. The most critical obstacles should be shown on the approach chart, listed in the AIP and shown on the Type A obstacle chart.)