.
The 95% navigation accuracy
.
The maximum vertical FTE fixed at 75ft if not demonstrated
.
The ASE
.
The waypoint precision error
.
The vertical angle error
.
The ATIS QNH error fixed at 20ft
The formula to compute the VEB also takes into consideration the temperature correction to the international standard atmosphere and the semi-wing span of the aircraft.
The VEB associated to the nominal vertical flight path defines an Obstacle Clearance Surface (OCS), which must be free of obstacle penetration.
A Missed Approach OCS (MA OCS) with a slope of 2.5% is normally used to analyze obstacles relevant for DA determination. If necessary a higher minimum climb gradient can be established to lower the DA.
The standard RNP value for the Missed Approach segment is 1 NM. However, a lower value can be used to avoid obstacles.
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6. RNP AR Instrument procedures
Getting to grips with RNP AR
6.2. RNP AR PROCEDURE CHARTING
The title of RNP AR procedures on the approach chart is RNAV (RNP). The indication “Special Aircraft & Aircrew Authorization Required” or “Authorization Required” is written in the notes area of the approach chart with other indications relative to the applicable limitations:
.
OAT limitation,
.
Wing span limitation if applicable,
.
Limitation for FMS not capable of RF leg,
.
Missed Approach climb gradient limitations if more than 200ft/NM is required,
.
The RNP value for Missed Approach if <1 NM is required (FAA)
RNP AR approaches cannot be flown with a remote or forecast QNH.
If necessary several lines of minima may be published for different RNP values.
As an example, an extract of a “public” RNP SAAAR approach chart for RNP 0.15 is given
below to illustrate the specific notes printed on these approach charts:
The example of approach chart given below is a study initiated by Airbus for an RNP 0.3 AR Approach in Katmandu designed by CGX AEROinSYS and ENAC. The benefit of this approach compared to the existing published VORDME approach is to replace the step down and steep vertical flight path by a constant 3° flight path angle.
The approach charts for RNP AR have usually a conventional layout with a map and a vertical flight path profile.
Few details deserve attention:
. The FAF (or PFAF) position from where the obstacle clearance is defined relative to an Obstacle Clearance Surface (OCS). Obstacle clearance is only ensured if the aircraft is flying on the defined vertical flight path.
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