Cold WX Altimetry Procedures
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Thankyou to all those who posted comments to ciold wx procedures.
My view.
Regulatory authorities need to define the cutoff for cold wx ops and apply procedures notified on ATIS or by ATC. Lets asume a cutoff of ISA-15. ATIS will state ILS approach 36R cold wx procedures in force. Same process as applies to Cat II/III. Pilots select specially modified cold wx ILS procedure for that runway from the database or printed Jeppesen chart. This will contain higher FAF and crossing alts and minima. Radar will modify descent alts initially to maintain terrain clearance up to the FAF then the ILS is like any other ILS.
The nature of the altimeter corrections means that the approach profile might exceed 1000fpm rate of descent. Especially for some non precision approaches. Further onboard databases would become substantially larger. The new FMS2 Pegacus on Airbus aircraft has the extra capacity but older databases do not. The advantage of having the procedure in the database means a managed approach can be flown with Airbus aircraft. The procedure being ATC initiated means that all inbound flights will be flying the same profiles.
My view.
Regulatory authorities need to define the cutoff for cold wx ops and apply procedures notified on ATIS or by ATC. Lets asume a cutoff of ISA-15. ATIS will state ILS approach 36R cold wx procedures in force. Same process as applies to Cat II/III. Pilots select specially modified cold wx ILS procedure for that runway from the database or printed Jeppesen chart. This will contain higher FAF and crossing alts and minima. Radar will modify descent alts initially to maintain terrain clearance up to the FAF then the ILS is like any other ILS.
The nature of the altimeter corrections means that the approach profile might exceed 1000fpm rate of descent. Especially for some non precision approaches. Further onboard databases would become substantially larger. The new FMS2 Pegacus on Airbus aircraft has the extra capacity but older databases do not. The advantage of having the procedure in the database means a managed approach can be flown with Airbus aircraft. The procedure being ATC initiated means that all inbound flights will be flying the same profiles.
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Like you say yourself Stephan: For an ILS all you have to do is correct the initial altitude, then be aware that your INDICATED alt over FAF will be higher than what says on the plate. Then correct your MDA, and you are safe.
For CANPA approach it will be slightly more complicated as you have check-altitudes all the way down.
To make a special cold-wx procedurre would be the surest way of messing things up. (only works for that specific temperature).
As long as your corrections are right, you fly the exact same profile as a std day. ( no 1000 fpm unless you fly fast
)
The pegasus airbus could probably be programmed with th exact temp to do the corrections for you, though i doubt Airbus will pay for it.
All you have to do is correct the crossing alt over the final waypoints. Our company dont let us fly CANPA in Final App mode, but the vertical dev bar is still there for crosschecking.
Fly safe, and correct your altitude
For CANPA approach it will be slightly more complicated as you have check-altitudes all the way down.
To make a special cold-wx procedurre would be the surest way of messing things up. (only works for that specific temperature).
As long as your corrections are right, you fly the exact same profile as a std day. ( no 1000 fpm unless you fly fast
)The pegasus airbus could probably be programmed with th exact temp to do the corrections for you, though i doubt Airbus will pay for it.
All you have to do is correct the crossing alt over the final waypoints. Our company dont let us fly CANPA in Final App mode, but the vertical dev bar is still there for crosschecking.
Fly safe, and correct your altitude
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CnF and Stephan,
Surely the whole point of the problem about NPAs in cold wx with the Airbus (and I guess the Boeing, but have no first hand experience) is that a managed approach is not possible because the kit is itself trying to establish you at the wrong altitudes. The vert deviation bar (brick or doughnut in the Airbus depending on mod state) will be below you throughout the approach. If you have corrected the final descent altitude correctly and descend at the correct point a normal RoD should put you on the correct profile. Next problem is working it all out since under radar control, as has been pointed out before in the thread, the controller will be making corrections for you. Not sure what would happen in PRC Stephan! Therefore one has to work backwards through the calcs to ascertain actual height and appropriate point for descent. Are there NPAs at Harbin Stephan..gets pretty cold there?
Surely the whole point of the problem about NPAs in cold wx with the Airbus (and I guess the Boeing, but have no first hand experience) is that a managed approach is not possible because the kit is itself trying to establish you at the wrong altitudes. The vert deviation bar (brick or doughnut in the Airbus depending on mod state) will be below you throughout the approach. If you have corrected the final descent altitude correctly and descend at the correct point a normal RoD should put you on the correct profile. Next problem is working it all out since under radar control, as has been pointed out before in the thread, the controller will be making corrections for you. Not sure what would happen in PRC Stephan! Therefore one has to work backwards through the calcs to ascertain actual height and appropriate point for descent. Are there NPAs at Harbin Stephan..gets pretty cold there?
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idg: The vertical dev. bar should be right where it is supposed to be if you have corrcted the alts in the FMGC.
As long as you dont fly it in FINALL APP mode there should be no problem with this. (Database validity problems)
How much i trust the controllers to make corrections i will leave unsaid. But they always let You start the procedure at the Altitude you deem necessary. (Advance notice buys you friends)
Happy Easter
As long as you dont fly it in FINALL APP mode there should be no problem with this. (Database validity problems)
How much i trust the controllers to make corrections i will leave unsaid. But they always let You start the procedure at the Altitude you deem necessary. (Advance notice buys you friends)
Happy Easter
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CnF
Agreed if you have changed the data and are flying selected the info should be good. But can we change the heights at the FF? I will try and re-post!
Agreed if you have changed the data and are flying selected the info should be good. But can we change the heights at the FF? I will try and re-post!
Last edited by idg; 14th Apr 2003 at 07:33.
