Document ID: chunk:federal_register_of_legislation:F2023C00696:body:0:p57
Version: federal_register_of_legislation:F2023C00696
Segment Type: other
Provision Reference: 
Character Range: 219726–222726

Section 10.9:   Separation Standards—Applicable to En-route Area Navigation by Aircraft Using Inertial Navigation Systems

10.9.1              Introduction

10.9.1.1         This section is concerned with the horizontal (that is, lateral and longitudinal) separation standards to be employed by ATC in respect of aircraft equipped for en-route area navigation (RNAV) and approved for such operations.

10.9.1.2         The standards must not be applied when ATC is aware that the time since the last opportunity to update the RNAV system's present position exceeds the limit, or after pilot advice of:

(a)         navigation equipment failure; or

(b)         operation of the equipment outside the approved tolerances.

10.9.2              Lateral Separation

       10.9.2.2 For lateral separation the across-track tolerance to be applied is to equal the CEP of the INS/IRS-derived position plus the FTE.

       10.9.2.3 The CEP is determined from the following:

           (a) at departure point the INS/IRS position can be assumed to be within a circle of radius 3 NM;

           (b) the INS/IRS position can be assumed to be within a circle of radius 4 NM at a designated waypoint suitable for updating inertial present position;

           (c) the CEP of the INS/IRS position expands at a rate corresponding to an increase in radius of 3 NM per hour (e.g. for a groundspeed of 300KT, divergence is 1 NM per 100 NM track flown).

       10.9.2.4 The FTE when the autopilot is not coupled to the INS/IRS for steering guidance is ±2 NM across track.

       10.9.2.5 Within the coverage of a short-range radio navigation aid (e.g. VOR, NDB, DME) defining the route, the tolerance applicable to that aid is to be used if it is less than that of the RNAV system.

10.9.3              Longitudinal Separation

10.9.3.1         The longitudinal separation minima based on time are derived by taking the following factors into account:

(a)         the along-track navigational tolerances, assumed to be:

(i)            the same for each aircraft;

(ii)          equal to the magnitude of the radial error of position of the least accurate navigation system; and

(iii)        calculated at the end of a route section, the end being defined as either:

(A)        A waypoint satisfying the parameters for updating present position; or

(B)        A 'gate-in' waypoint marked by NDB, VOR, DME or a combination thereof, for entry into the radio-navigation air route structure; or

(C)        A waypoint beyond which a larger separation standard is specified;

(b)         the tolerance of each aircraft's estimated arrival time at the next reporting point (taken as ±3 MIN);

(c)          an estimation tolerance of ±2 MIN to allow for errors in the ATC's estimation of future positions of the aircraft in conflict;

(d)         a control tolerance of ±2 MIN for control factors such as communications delays, clock errors and human factors;

(e)         each of these tolerances is combined by the