Dollehz
6th May 2014, 09:23
Hello,
I stumbled upon some confusing values when comparing ICAO doc 8168 to Jeppesen and Lido.
According to ICAO:
The MOC value to be applied in the primary area for the enroute phase of an IFR flight is 300 m (1000 ft). In mountainous areas this shall be increased, depending on: Variation in terrain elevation
Between 900 m (3 000 ft) and 1 500 m (5 000 ft) MOC: 450 m (1 476 ft)
Greater than 1 500 m (5 000 ft) MOC: 600 m (1 969 ft)
Jeppesen:
Grid MORA values clear all terrain and obstructions by 1000 feet in areas where the highest elevations are 5000 feet MSL or lower. MORA values clear all terrain by 2000 feet in areas where the highest elevations are 5001 feet MSL or higher.
LIDO:
Minimum Grid Altitude (MGA) (= grid MORA)
MGA represents the lowest safe altitude which can be flown off-track.
The MGA is calculated by rounding up the elevation of the highest obstruction within the respective grid area
to the next 100ft and adding an increment of
• 1000ft for terrain or obstructions up to 6000ft or
• 2000ft for terrain or obstructions above 6000ft.
Imagine obstacles at 5000ft; Icao says 1500ft obstacle clearance for mimimum obstacle clearance altitude so minimum alt 6500ft. But according to Jepp/LIDO the lowest possible safe altitude (grid mora) I can fly is is 500ft lower (MOC of 1000ft) so i can fly at minimum 6000ft.
Shouldn't ICAO be the most restrictive? I know i compare enrout MOC to grid mora, but obstacle clearance is obstacle clearance.. Or am i really missing something here?
I stumbled upon some confusing values when comparing ICAO doc 8168 to Jeppesen and Lido.
According to ICAO:
The MOC value to be applied in the primary area for the enroute phase of an IFR flight is 300 m (1000 ft). In mountainous areas this shall be increased, depending on: Variation in terrain elevation
Between 900 m (3 000 ft) and 1 500 m (5 000 ft) MOC: 450 m (1 476 ft)
Greater than 1 500 m (5 000 ft) MOC: 600 m (1 969 ft)
Jeppesen:
Grid MORA values clear all terrain and obstructions by 1000 feet in areas where the highest elevations are 5000 feet MSL or lower. MORA values clear all terrain by 2000 feet in areas where the highest elevations are 5001 feet MSL or higher.
LIDO:
Minimum Grid Altitude (MGA) (= grid MORA)
MGA represents the lowest safe altitude which can be flown off-track.
The MGA is calculated by rounding up the elevation of the highest obstruction within the respective grid area
to the next 100ft and adding an increment of
• 1000ft for terrain or obstructions up to 6000ft or
• 2000ft for terrain or obstructions above 6000ft.
Imagine obstacles at 5000ft; Icao says 1500ft obstacle clearance for mimimum obstacle clearance altitude so minimum alt 6500ft. But according to Jepp/LIDO the lowest possible safe altitude (grid mora) I can fly is is 500ft lower (MOC of 1000ft) so i can fly at minimum 6000ft.
Shouldn't ICAO be the most restrictive? I know i compare enrout MOC to grid mora, but obstacle clearance is obstacle clearance.. Or am i really missing something here?