Question on FLS on Airbus A320 aircraft

[martin2304]

A320 Pilots, Hello!
When flying non precision RNP APP using FLS outside of temperature range published on chart, do we need to correct minimums and which minimums to use? (LPV, LNAV/VNAV or LNAV)
Or let's say even in the published range, chart says BARO-VNAV not authorized below -45°c, do we need to correct minima
Thank you

[JABBARA]

Assuming A 320 FLS is same as A 350 (which is very likely)

• Surely you have to make correction to DA even you fly with FLS
• Surely you have to make correction to your FAF (platform) altitude even you fly with FLS as informing ATC if you are not under ATC Radar Control
• Technically I know, there is no cold temperature limit applies if you fly with FLS provided above corrections are made, but procedurally it may be requiring, I do not remember any Regulation emphasizing this

All these above because, when airplane symbol hits magenta glide line (and simultaneously green FMS line ascends and merges with it), VD vertical scale start to indicate True Height (almost same with geometric height) and this magenta line ensures geometric clearance with terrain, but barometric height (Barometric Altitude - Threshold altitude) will always show greater than true height. This difference will reduce as descent goes on and equal to zero only at touchdown, so not zero at DA. Therefore a cold weather correction is needed at DA to ensure true height clearance (DH) when visual contact established or GA is initiated

[martin2304]

Originally Posted by JABBARA

Assuming A 320 FLS is same as A 350 (which is very likely)

• Surely you have to make correction to DA even you fly with FLS
• Surely you have to make correction to your FAF (platform) altitude even you fly with FLS as informing ATC if you are not under ATC Radar Control
• Technically I know, there is no cold temperature limit applies if you fly with FLS provided above corrections are made, but procedurally it may be requiring, I do not remember any Regulation emphasizing this

All these above because, when airplane symbol hits magenta glide line (and simultaneously green FMS line ascends and merges with it), VD vertical scale start to indicate True Height (almost same with geometric height) and this magenta line ensures geometric clearance with terrain, but barometric height (Barometric Altitude - Threshold altitude) will always show greater than true height. This difference will reduce as descent goes on and equal to zero only at touchdown, so not zero at DA. Therefore a cold weather correction is needed at DA to ensure true height clearance (DH) when visual contact established or GA is initiated

Thank you very much for the answer

[SamuelCV]

JABBARA It absolutly make sence you comment. In 737 we have to fly LNAV/VNAV whitin temperature range withou any temperature correction, but if we are outsinde limmit we have to fly LNAV with correction to IAF ,IF,FAF and DA/MDA, holding , MSA. But I have a question regarding first par of martin2304 using FLS, when on RNP chart is depicted LPV, LNAV/VNAV, LNAV minimums which one you pick up?...As far as I remember in LNA/VNAV DA is constructed for minimum possible temperature in order to avoid obstacles so in this case applying correstion is not necessary. On the other hand in charts there are notes that for high temperatures GP may much more higher comare to isa deviation GP shoving in FMS/MCDU.

[JABBARA]

SamuelCV

JABBARA It absolutly make sence you comment. In 737 we have to fly LNAV/VNAV whitin temperature range withou any temperature correction, but if we are outsinde limmit we have to fly LNAV with correction to IAF ,IF,FAF and DA/MDA, holding , MSA. But I have a question regarding first par of martin2304 using FLS, when on RNP chart is depicted LPV, LNAV/VNAV, LNAV minimums which one you pick up?...As far as I remember in LNA/VNAV DA is constructed for minimum possible temperature in order to avoid obstacles so in this case applying correstion is not necessary. On the other hand in charts there are notes that for high temperatures GP may much more higher co

Just brief replies

• All answers are available to your questions in DOC 8168 Volume I Flight Procedures(PAN-OPS), at the moment I can not give you reference page by page, but if you cannot find yourself I can do it later
• FLS is not an approach procedure but is a technique trademarked by Airbus
• PAN-OPS says regardless your technique you have to apply Cold Temperature corrections (this is intuitively logical as well as I tried to explain in my previous post)
• PAN-OPS says
  For aircraft with approved automated cold temperature compensation FMS systems, the promulgated
  minimum temperature can be disregarded provided the actual temperature is within the limits of the aircraft
  certification.

  this is an answer to my ambiguous words in my previous post to martin2304' s question; I mean yes you can ignore cold temperature limit on chart if you fly FLS provided minimums are corrected for cold temperature (this is also intuitively logical as well as I tried to explain in my previous post)
• LNAV/VNAV min is a Baro-VNAV kind approach minimum, Whereas LPV isbanyo giderini sökmek completely different and it is not a Baro-VNAV approach and approach path is not effected from temperature (similar to ILS) but still needs barometric correction at minimums . To be able to use LPV minimum, GNSS on board, should have SBAS (Satellite Based Augmentation System) capability. By SBAS, approach path is calculated and flown as 3D GNSS position, so no need barometric path

[SamuelCV]

Simply said ,I kow that LPV is SBAS in which "VNAV" GP is corrected by GPS, but FLS is as well compensated and did the same job in final approach segment using avionc correction of GP. If in DOC 8168 is clearly statet which minimums in this case I must use I will check it. Thanks for your effort JABBARA

[FlyingFlight]

To my knowledge, you still have to select LNAV/VNAV minima, as the LPV is a different kind of approach, for which you need to have certain equipment(in this case, SBAS) and certain certifications/authorizations from the regulator that the A320. Even if the A320 onboard navigations systems are as precise as those in LPV approved aircraft, you're still legally restricted to LNAV/VNAV. Maybe in the future Airbus incorporates this requirements and thus A320s will be able to perfomr LPV approaches.