FLIGHT BELOW MINIMUM ALTITUDES
Descent below MEA or GRID MORA
Diversion procedures for critical cases are established taking into account the topography along the route and the requirements mentioned below (engine(s) failure, depressurisation).
Company routes which transit areas of the world with high terrain exceeding 10.000 feet GRID MORA are assessed for depressurization and drift down compliance. If applicable, critical segments along a route are identified and an analysis of the terrain is carried out using topographical and/or aeronautical charts. In those cases instructions will be published for an escape procedure in case of depressurization or drift down.
Abnormal Operation
It may be necessary to establish diversion procedures for critical cases taking into account the topography along the route and the requirements mentioned below (engine failure, depressurization).
It may be necessary to determine Point(s) of No Return (PNR) and establish appropriate procedures (drift down on course, turn back or diversion outside the track depending on the aircraft position).
Pressurization Failure
For depressurization, it may be necessary to descend below the en-route minimum altitude determined for normal operation in order to cope with passenger oxygen requirements (refer to 8.8). At any time, the aircraft gross (actual) flight path must vertically clear all the obstacles by 2000 ft.
Engine Failure
For engine failure, the net flight path as defined in the FCOM must be considered.
Note: For terrain limited routes, Decompression and Drift Down Procedures are established in the Operations Manual Part C: Route and Airport.
Corrections to Minimum Flight Altitudes and Flight Levels
All published altitudes are TRUE altitudes above MSL. They do not take into account the means of measuring aeroplane altitude. All minimum flight altitudes and flight levels described in OM Part A, Chapter 8.1.1, shall be corrected for the effects of:
Wind Correction in Areas of High Terrain
When flights are conducted within 20 NM of terrain that rises over 2000 ft, the minimum flight altitudes shall be corrected for the wind effect in accordance with the following table:
Note: When flying En-route, MOC over mountainous areas is normally applied during the design of the routes and is stated in the AIP. For the Terminal Areas the states may provide guidance; it is up to the Commander to evaluate whether the combination of terrain, wind strength and direction are such as to make a correction for wind. When this is done the controller shall be notified.
Temperature Correction
For operational procedures refer to OM Part B, 3.7.2 Low Temperature Corrections.
The calculated minimum altitudes must be corrected when the OAT is much lower than that predicted by the standard atmosphere. The correction has to be applied on the height above the elevation of the altimeter setting source. The altimeter setting source is generally the atmosphere pressure at an airport, and the correction on the height above the airport has to be applied on the indicated altitude. The same correction value is applied when flying at either QFE or at QNH.
Low Altitude Temperature Correction
1) Approximate correction: Increase obstacle elevation by 4% per 10ºC below ISA of the height above the elevation of the altimeter setting source or decrease aeroplane indicated altitude by 4% per 10°C below ISA of the height above the elevation of the altimeter setting source.
This method is generally used to adjust minimum safe altitudes and may be applied for all altimeters setting source altitudes for temperatures above 15ºC below zero.
2) Tabulated corrections: For colder temperatures, a more accurate correction should be obtained from the following table calculated for a sea level aerodrome. It is conservative when applied at higher aerodrome.
High Altitude Temperature Correction
The graph given hereafter has to be used en-route for high altitude operation. It does not take into account the elevation of the altimeter setting source. In theory, this correction applies to the air column between the ground and the aeroplane. When flying above high terrain, the use of this correction gives a conservative margin.
Pressure Correction
When flying at levels with the altimeter set to 1013 hPa, the minimum safe altitude (MSA/MEA) must be corrected for deviations in pressure when the pressure is lower than the standard atmosphere (1013hPa).
A conservative correction method of 30 ft per hPa below 1013 hPa shall be used.
Example:
Given: Indicated altitude = 20000 ft, ISA, local QNH = 995 hPa;
Find: Geometrical (True) Altitude = ___ (Answer: 20000 - (18 x 30) = 19460 ft).
The following table gives more accurate data. The correction is to be applied to the indicated altitude (reference 1013 hPa) to determine the geometrical aircraft altitude. When the pressure is higher than the standard atmosphere (1013hPa),
Criteria for Determining the Usability of Aerodromes
Departure, Destination and Alternate aerodromes to be used for operations must be adequate for the type of aircraft and operation concerned. To be selected for conducting an operation they should be suitable at the time of the operation.
- When navigating by the use of a radio navigation aids, descent below the MEA or GRID MORA to the MSA may be made when overflying the navigation aid from which an approach-to-land will be conducted, provided the aeroplane's position can be accurately established as being within 25 NM from the navigation aid upon which the minimum sector altitude is based.
- When being radar vectored (unambiguously announced by radar controller, e.g. »RADAR CONTACT, THIS WILL BE (RADAR) VECTORING...«), descent below the MEA or GRID MORA to the MSA may be made, provided the aeroplane's position can be accurately established as being within 25 NM from the navigation aid upon which the minimum sector altitude is based.
- When conducting radar vectored instrument approaches (unambiguously announced by radar controller, e.g. »RADAR CONTACT, THIS WILL BE (RADAR) VECTORING...«), clearance to descend below the MSA may be accepted provided the Commander is able to monitor the aeroplane's position using the available navigation aids.
- In certain instances the MSA for a given sector may be higher than MEA established for a particular route segment between fixes or for a holding area within that sector. In such cases descent below MSA down to the MEA is permitted, provided the flight is conducted along the respective route or within the holding area.
- Aeroplane proceeding laterally and vertically in accordance with published SID is safe in respect of terrain and other restrictions on any level included in the SID or otherwise assigned by ATC.
- MEA published for subsequent segments of a departure route shall be observed by commencement of climb sufficiently in advance to ensure that the point from which the higher MEA applies is crossed not below such altitude.
- During an off-route departure, level flight may only be accepted at or above applicable MSA or GRID MORA.
- An aeroplane being radar vectored during departure may be flown below MEA/MSA/GRID MORA, provided the Commander is able to monitor the aeroplane's position using the available navigation aids. Radar vectoring procedures shall only be accepted if unambiguously announced by radar controller (e.g. »RADAR CONTACT, THIS WILL BE (RADAR) VECTORING ...«) when positive radar control is established and maintained.
Diversion procedures for critical cases are established taking into account the topography along the route and the requirements mentioned below (engine(s) failure, depressurisation).
Company routes which transit areas of the world with high terrain exceeding 10.000 feet GRID MORA are assessed for depressurization and drift down compliance. If applicable, critical segments along a route are identified and an analysis of the terrain is carried out using topographical and/or aeronautical charts. In those cases instructions will be published for an escape procedure in case of depressurization or drift down.
Abnormal Operation
It may be necessary to establish diversion procedures for critical cases taking into account the topography along the route and the requirements mentioned below (engine failure, depressurization).
It may be necessary to determine Point(s) of No Return (PNR) and establish appropriate procedures (drift down on course, turn back or diversion outside the track depending on the aircraft position).
Pressurization Failure
For depressurization, it may be necessary to descend below the en-route minimum altitude determined for normal operation in order to cope with passenger oxygen requirements (refer to 8.8). At any time, the aircraft gross (actual) flight path must vertically clear all the obstacles by 2000 ft.
Engine Failure
For engine failure, the net flight path as defined in the FCOM must be considered.
Note: For terrain limited routes, Decompression and Drift Down Procedures are established in the Operations Manual Part C: Route and Airport.
Corrections to Minimum Flight Altitudes and Flight Levels
All published altitudes are TRUE altitudes above MSL. They do not take into account the means of measuring aeroplane altitude. All minimum flight altitudes and flight levels described in OM Part A, Chapter 8.1.1, shall be corrected for the effects of:
- High wind speed in areas of high terrain;
- Temperature variations from standard;
- Pressure variations from standard.
Wind Correction in Areas of High Terrain
When flights are conducted within 20 NM of terrain that rises over 2000 ft, the minimum flight altitudes shall be corrected for the wind effect in accordance with the following table:
Note: When flying En-route, MOC over mountainous areas is normally applied during the design of the routes and is stated in the AIP. For the Terminal Areas the states may provide guidance; it is up to the Commander to evaluate whether the combination of terrain, wind strength and direction are such as to make a correction for wind. When this is done the controller shall be notified.
Temperature Correction
For operational procedures refer to OM Part B, 3.7.2 Low Temperature Corrections.
The calculated minimum altitudes must be corrected when the OAT is much lower than that predicted by the standard atmosphere. The correction has to be applied on the height above the elevation of the altimeter setting source. The altimeter setting source is generally the atmosphere pressure at an airport, and the correction on the height above the airport has to be applied on the indicated altitude. The same correction value is applied when flying at either QFE or at QNH.
Low Altitude Temperature Correction
1) Approximate correction: Increase obstacle elevation by 4% per 10ºC below ISA of the height above the elevation of the altimeter setting source or decrease aeroplane indicated altitude by 4% per 10°C below ISA of the height above the elevation of the altimeter setting source.
This method is generally used to adjust minimum safe altitudes and may be applied for all altimeters setting source altitudes for temperatures above 15ºC below zero.
2) Tabulated corrections: For colder temperatures, a more accurate correction should be obtained from the following table calculated for a sea level aerodrome. It is conservative when applied at higher aerodrome.
High Altitude Temperature Correction
The graph given hereafter has to be used en-route for high altitude operation. It does not take into account the elevation of the altimeter setting source. In theory, this correction applies to the air column between the ground and the aeroplane. When flying above high terrain, the use of this correction gives a conservative margin.
Pressure Correction
When flying at levels with the altimeter set to 1013 hPa, the minimum safe altitude (MSA/MEA) must be corrected for deviations in pressure when the pressure is lower than the standard atmosphere (1013hPa).
A conservative correction method of 30 ft per hPa below 1013 hPa shall be used.
Example:
Given: Indicated altitude = 20000 ft, ISA, local QNH = 995 hPa;
Find: Geometrical (True) Altitude = ___ (Answer: 20000 - (18 x 30) = 19460 ft).
The following table gives more accurate data. The correction is to be applied to the indicated altitude (reference 1013 hPa) to determine the geometrical aircraft altitude. When the pressure is higher than the standard atmosphere (1013hPa),
Criteria for Determining the Usability of Aerodromes
Departure, Destination and Alternate aerodromes to be used for operations must be adequate for the type of aircraft and operation concerned. To be selected for conducting an operation they should be suitable at the time of the operation.
FLIGHT BELOW MINIMUM ALTITUDES
Reviewed by Aviation Lesson
on
10:08 AM
Rating:
Reviewed by Aviation Lesson
on
10:08 AM
Rating:
No comments: