Hi B737,

just curious about which technique you have used to correct the altitudes according to your manufacturer/operator procedures.

Thanks.

Interesting, that would be a different according to our OM/A here. It states quite clearly:

"No corrections are needed for reported temperatures above -15°C or if the aerodrome temperature is at or above the minimum published temperature for the procedure being flown;"

My company are new to RNAV/RNP approaches so they may be a bit confused as I am to this topic.

We are told if the temp is below 0 degrees we cold temp correct all procedure altitudes (platform, MSA, MDH, Dist/ALt ).

I understand that below the stated temp limitation on the chart Vnav can no longer be used.

FWIW our EASA-land OM, paraphrased, for RNAV.../uncompensated VNAV states:

Always fly ATC assigned altitudes without corrections, unless considered unsafe.. etc etc.

If you are at or warmer than the charted minimum temperature for using VNAV then it can be used with no corrections to procedure altitudes.

If it is colder than the limiting temperature, you use the non-VNAV minima if they exist (and vertical mode to be used is V/S or FPA).

If it's any colder than ISA -25 you apply low temp corrections (using an approved table/calculator) to any platform/FAF altitude and MDA/DA. Tell ATC what your Platform/FAF crossing altitude is going to be.

Cold Temperature Altitude Corrections
Extremely low temperatures create significant altimeter errors and greater potential for reduced terrain clearance. When the temperature is colder than ISA, true altitude will be lower than indicated altitude. Altimeter errors become significantly larger when the surface temperature approaches -30°C or colder, and also become larger with increasing height above the altimeter reference source.
Apply the altitude correction table when needed:
• no corrections are needed for reported temperatures above 0°C or if the airport temperature is at or above the minimum published temperature for the procedure being flown
• do not correct altimeter barometric reference settings
• ATC assigned altitudes or flight levels should not be adjusted for temperature when under radar control
• corrections apply to QNH and QFE operations
• apply corrections to all published minimum departure, en route and approach altitudes, including missed approach altitudes, according to the table below. Advise ATC of the corrections
• MDA/DA settings should be set at the corrected minimum altitudes for the approach
• subtract the elevation of the altimeter barometric reference setting source (normally the departure or destination airport elevation) from the published minimum altitude to be flown to determine “height above altimeter reference source”
• enter the table with Airport Temperature and with “height above altimeter reference source”. Read the correction where these two entries intersect. Add the correction to the published minimum altitude to be flown to determine the corrected indicated altitude to be flown. To correct an altitude above the altitude in the last column, use linear extrapolation (e.g., to correct 6000 feet or 1800 meters, use twice the correction for 3000 feet or 900 meters, respectively.) The corrected altitude must always be greater than the published minimum altitude
• if the corrected indicated altitude to be flown is between 100 foot increments, set the MCP altitude to the closest 100 foot increment above the corrected indicated altitude to be flown.

This document http://www.developpement-durable.gou...NSS__ENGv3.pdf says that no temperature corrections are required if the airport is at or above the minimum published on the chart.

If the temperature is below the published minimum then:
"7.5.4 Case of temperatures below minimum temperatures published on the approach chart

On the RNAV(GNSS) approach charts for which there is an APV BaroVNAV approach (presence of LNAV/VNAV minima), a minimum temperature use is published.
As a general rule, pilots should not use the FMS (Baro)VNAV function when the temperature is below the temperature limit published on the approach chart.
The associated non-precision approach (LNAV) can be performed but management of the vertical plane should use another flight technique (vertical speed (V/S) or flight path angle (FPA).
Pilots should then apply the cold temperature corrections necessary to comply with the different published minimum altitudes, i.e.:
- The altitude heights for the final segment (FAF, SDF, altitude/distance table);
- The MDA/H; and
- The V/S and/or FPA values. "

That is interesting. But it leaves things potentially open to interpretation. They should specifically mention whether the MDA needs to have a temperature correction as this is very important.

You should find that clarification in your company OPS Manual.
Ours says:

"Low Altitude Temperature Corrections
..... These corrections must be applied, as appropriate, when conducting an instrument approach:

To DA (except Baro-VNAV procedures that are published with a temperature limit) and MDA. ...."

Thanks,

But I want official government publication info. I find that ops manuals tend to have a much higher rate of erronous info based on the individuals misinterpreting official information.

Hi JammedStab,
Will Jeppesen do?
http://www.jeppesen.com/download/bri...en00-arnav.pdf See Page 8
"Cold Temperature Limitations. Considering the pronounced effect of nonstandard temperature on BARO-VNAV operations, a minimum temperature limitation will be published for each procedure for which BARO-VNAV operations are eligible.
This temperature represents the airport temperature below which use of the BAROVNAV will not be authorized to the LNAV/VNAV minimums."

Reference Documentation and Cold Weather Ops
 

The reference document for the construction and operational use of BARO-VNAV and temperature limits is: ICAO Doc 8168. For those of you who are using Jepp FD or Jepp FD Pro, this document is available in the manual list. The manuals located inside should be read. There is a wealth of information contained therein.

Jepp. is NOT regulatory material, it so happens that they produce material based on what regulatory and SARPS promulgate.

I've quoted most of the information here directly from Doc 8168.

In essence, when the procedure designers build an approach for BARO/VNAV, limited temperature effects are accounted for on the descent segment. The temperature limits are there to protect the shallow gradients during a managed or IAN type approach. That said however; the DH/DA/MDAs still must be accounted for with the correct non-standard temperature corrections found in the tables. If the temperature is outside of the published limits then the procedure can still be flown but not managed or IAN and all the altitudes in the descent must be corrected for temperature error.

Some aircraft equipment are certified to calculate their own corrections from the FMS to certain limits. If that is the case, then other corrections can be disregarded as long as the temperatures being flown are within the certification limits of the installed equipment.

This is directly from ICAO Doc: 8168

1.2.2 Atmospheric effects

1.2.2.1 Atmospheric errors associated with non-standard temperatures are considered in the design of the approach obstacle clearance surface. When temperatures are lower than standard, the aircraft’s true altitude will be lower than its barometric indicated altitudes.

1.2.2.2 Most existing VNAV systems do not correct for non-standard temperatures. At temperatures below standard, these errors can be significant and increase in magnitude as altitude above the station increases. The gradient of the approach obstacle clearance surface is reduced as a function of the minimum temperature promulgated for the procedure.
Note.— International Standard Atmosphere (ISA) temperature is 15°C at sea level with a lapse rate of 2°C per 1 000 ft of altitude.

1.2.3 Along-track position uncertainty
All RNAV systems have some amount of along-track error. This along-track uncertainty can mean that the VNAV system will start the descent too early and result in an error in the vertical path. This is compensated for in procedure design by relocating the threshold level origin of the approach obstacle clearance surface.

1.2.4 Flight technical error (FTE)
Flight technical error (FTE) is assumed to be contained within the standard non-precision margin of 75 m (246 ft). This is added below the VPA before the obstacle clearance surface is adjusted for cold temperature and along-track error.

1.2.5 Other system errors
Other errors include static source error, non-homogenous weather phenomena and latency effects. These are insignificant compared with the other errors already addressed and are considered as contained within the existing margin.

1.2.6 Blunder errors
Application of an incorrect or out-of-date altimeter setting, either by air traffic control or the pilot, is possible and must be prevented by appropriate operational techniques.

1.3 EQUIPMENT REQUIREMENTS
1.3.1 APV/baro-VNAV procedures are intended for use by aircraft equipped with flight management systems (FMS) or other RNAV systems capable of computing barometric VNAV paths and displaying the relevant deviations on the instrument display.

1.3.2 Aircraft equipped with APV/baro-VNAV systems that have been approved by the State of the Operator for the appropriate level of lateral navigation (LNAV)/VNAV operations may use these systems to carry out APV/baro- VNAV approaches provided that:

a) the navigation system has a certificated performance equal to or less than 0.6 km (0.3 NM), with 95 per cent probability. This includes:

1) GNSS navigation systems certified for approach operations;

2) multi-sensor systems using inertial reference units in combination with certified DME/DME or GNSS; and 3) RNP systems approved for RNP 0.3 operations or less;

b) the APV/baro-VNA V equipment is serviceable;

c) the aircraft and aircraft systems are appropriately certified for the intended APV/baro-VNAV approach operations;

d) the aircraft is equipped with an integrated LNAV/VNAV system with an accurate source of barometric altitude; and

e) the VNAV altitudes and all relevant procedural and navigational information are retrieved from a navigation database whose integrity is supported by appropriate quality assurance measures.

Note.— Acceptable means of compliance can be found in documents such as the United States Federal Aviation Administration (FAA) Advisory Circular (AC) 20-138, AC 20-130A and AC 120-29.

1.3.3 Where LNAV/baro-VNAV procedures are promulgated, the approach area has been assessed for obstacles penetrating the Annex 14 inner approach, inner transitional and balked landing surfaces. If obstacles penetrate these surfaces, a restriction is placed on the minimum value of OCA/H permitted (see 1.1.5).

1.4 OPERATIONAL CONSTRAINTS

1.4.1 Pilots are responsible for any necessary cold temperature corrections to all published minimum altitudes/heights. This includes:

a) the altitudes/heights for the initial and intermediate segment(s);

b) the DA/H; and

c) subsequent missed approach altitudes/heights.

Note.— The final approach path VPA is safeguarded against the effects of low temperature by the design of the procedure.

1.4.2 Temperatures below the promulgated minimum
Baro-VNAV procedures are not permitted when the aerodrome temperature is below the promulgated minimum aerodrome temperature for the procedure, unless the flight management system (FMS) is equipped with approved cold temperature compensation for the final approach. In this case, the minimum temperature can be disregarded provided it is within the minimum certificated temperature limits for the equipment. Below this temperature, and for aircraft that do not have FMSs equipped with approved cold temperature compensation for the final approach, an LNAV procedure may still be used provided that:

a) a conventional RNAV non-precision procedure and APV/LNAV OCA/H are promulgated for the approach; and

b) the appropriate cold temperature altimeter correction is applied to all minimum promulgated altitudes/heights by the pilot.

1.4.3 A VPA deviation chart may be published on baro-VNAV instrument procedure charts, correlating an aerodrome temperature with an associated true VPA. This chart is intended to advise flight crews that although the non- temperature compensated aircraft’s avionics system may be indicating the promulgated final approach VPA, the actual VPA is different from the information presented to them by the system.

1.4.4 This chart is not intended to have the pilot increase or decrease the VPA flown to achieve the actual promulgated VPA. A sample of the chart is provided in Table II-4-1-1.

1.4.5 Some baro-VNAV systems have the capability to correctly compensate the VPA of an instrument approach procedure following an input of the aerodrome (altimeter source) temperature by the pilot. Pilots operating aircraft with this feature active are expected to ignore the VPA chart and fly the system-corrected VPA guidance

I hope that helps. Doc 8168 contains a wealth of information including correct entry procedures for conducting GNSS approaches, something that many still misunderstand.

So, when sitting there in the middle of the night as you're hauling *ss across the NOPAC/SOPAC/NATS or POLAR, haul out the manual and have a look. That's flying!
Seasons Greetings and a safe flying for New Year 2016 to all.

Thanks. The way I interpret the above, is that regardless of the type of Baro-VNAV approach being performed, corrections must be made to all published minimum altitudes/heights.

Corrections to Altitudes/Heights
 

If you are under radar control, there is no need to correct for vectoring altitudes. If you are cleared for a full procedure approach (complete with procedure turn) but you are under radar control, there is no need for corrections for procedure turn altitudes It is good airmanship to be aware of what the correction is, in case of LossComms or automation difficulties.

If using BARO/VNAV andyou are within the temperature limit of the approach, you may descend on the vertical descent path established either 'managed, VNAV/IAN' without having to make any corrections, however; it is a good idea to know what these corrections are (in the case of DME fix or FAF), in-case there is a failure of the automation and you're able to maintain a vertical descent using an alternative method (VS).

What MUST be done is: The DH/MDA/DA must be corrected for temperature for the approach, otherwise you could reach minimums and actually be below the obstruction clearance altitude (due to altimeter error).

If the OAT is colder than the Limit Temperature, the procedure cannot be flown using the automation and an alternative approach would be selected using a constant descent profile...good old VS!

Previously I mentioned referenced Regulatory material...ICAO is NOT regulator, it provides Standards and Recommended Practices (SARPS). From ICAO's documentation and technical publications, performance engineers and procedures engineers develop approach profiles that meet local regulatory requirements.

I hope that helps.

Thank you very much. I think your post is true in every word. Also, the only correct one so far!: O

terpster is correct.

Temperature limits are listed for non-compensated baro, and the cold limit on a 3 degree glideslope is 2.71 degrees.

What is also important are the associated ROC per segment. Initial segments have a 1000' ROC, the intermediate has a 500' ROC, final approach segment tapers from 500' ROC to a 200' ROC. (assuming non-mountanous)

The FAA, in the design criteria, adjusts the FAS ROC per the coldest anticipated temperature at airport, but NOT the intermediate segment, or more important, the missed approach segment(s).
This is important to know when it gets colder, how important the obstacle clearance reduction is, especially with terrain.

Custom criteria may go further in the obstacle clearance criteria with temperature, especially when OEI procedures are considered.

In consideration of the design criteria, the FAA has a special Cold Temp Restricted Airports list, with special instructions.

ICAO criteria in general, looks more like the special cold restictions

Notices to Airmen Cold Temp − Restricted Airports
GENERAL 4−GEN−15

Pilots must make an altitude correction to the published, “at”, “at or above” and “at or below” altitudes on designated segment(s) (see list below), on all published procedures and runways, when the reported airport temperature is at or below the published airport cold temperature restriction.

Pilots without temperature compensating aircraft are responsible to calculate and make a manual cold temperature altitude correction to the designated segment(s) of the approach using the AIM 7-2-3, ICAO Cold Temperature Error Table.

Pilots with temperature compensating aircraft must ensure the system is on and operating for each segment requiring an altitude correction. Pilots must ensure they are flying at corrected altitude. If the system is not operating, the pilot is responsible to calculate and apply a manual cold weather altitude correction using the AIM 7-2-3 ICAO Cold Temperature Error Table. PILOTS SHOULD NOT MAKE AN ALTIMETER CHANGE to accomplish an altitude correction.

Pilots must report cold temperature corrected altitudes to Air Traffic Control (ATC) whenever applying a cold temperature correction on an intermediate segment and/or a published missed approach final altitude. This should be done on initial radio contact with the ATC issuing approach clearance. ATC requires this information in order to ensure appropriate vertical separation between known traffic.

Pilots must not apply cold temperature compensation to ATC assigned altitudes or when flying on radar vectors in lieu of a published missed approach procedure.

Pilots should query ATC when vectors to an intermediate segment are lower than the requested intermediate segment altitude corrected for temperature.

Pilots are encouraged to self-announce corrected altitude when flying into uncontrolled airfields.

Mine is as well, correct the minimum altitudes.

JammedStab:

So was mine. :)

But, mine was limited to FAA-land.

To repeat myself, in FAA-land Baro VNAV final approach segment temperature limits are different than procedural altitude corrections for cold temperature. :ugh:

Regulatory material
 

Guys, I opened the thread with both
ICAO SARPS references AND
EASA regulatory, but not exclusive, references (AMC 20-27)

Said that...I made reference to the new Airbus getting to grips with cold wx Ops,which clearly contrast to EASA AMC...

Company OMs can be on one side or the other but if I have to choose, I would preferably stay more on the safe side (EASA) than Airbus interpretation.

With the line breaks, the OP is a bit difficult to read.

It is important to know, depending on the procedure type, and which criteria, which segments are compensated for, and which one are not.

In reading through the sections, I am not sure I see a conflict...The EASA is a bit more comprehensive...

Copied straight from my FCOM bulletin regarding RNAV GNSS approaches:

Cold Temperature Altitude Corrections
In the design of RNP APCH APV procedures with LNAV/VNAV minima, the
allowable temperature range is specified and the procedure design accounts for
operations and obstacle clearance for any temperature within the specified range
on the approach plate. If the actual temperature is within the specified temperature
range the pilot can fly the RNP APCH APV procedure and no temperature
corrections are needed. If the actual temperature is outside the specified
temperature range, the crew cannot fly the RNP APCH APV procedure.
In this case an RNP APCH NPA procedure with LNAV minima may be used and
the altitude constraints at FMC waypoints on the final approach need to be
modified according BOM 8.3-3, as the procedure design does not take
temperature variations into account.
For both RNP APCH APV (LNAV/VNAV minima) and RNP APCH NPA (LNAV
minima) approaches, the initial, intermediate and missed approach segment flight
plan fixes need to be corrected for cold temperature.
Note: DA/MDA must also be corrected for low temperatures


Makes perfect sense to me!!

Note: in case the temp is below the min temp specified, you can still fly the approach with LNAV and VNAV modes!!! Just not to LNAV/VNAV minima, but to LNAV minima raised for cold wx corrections.
(When temp is below 0 but above temp specified for LNAV/VNAV minima, you still have to raise the LNAV/VNAV minima)