CDFA Calculation in Charts
Joined: Dec 2002
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From: Where the Quaboag River flows, USA
In any case, the 1:60 rule says the 5.4* path is 540 ft/nm times ground speed in nm/min. 150 knots equals about 1350 fpm.
Joined: Apr 2009
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From: DM33
Why wouldn't one fly an approach like this in FPA mode? Is it that few aircraft have an autopilot FPA mode or that the mode is there but crews are not trained to use it. (MD-11, B-717, and MD-10 all had an FD/AP FPA mode which is ground referenced, not airmass referenced. No need to observe GS and compute required VS. Just dial in FPA -5.4 at the FAF and change it to -3.0 at 5.5 DME. Yes, of course altitude monitoring is still required.)
Eidolon
Joined: May 2001
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From: Some hole
We flew the VOR 02 in NAV-FPA, as an early stabilized approach, landing config and Vapp at the FAF, make Vapp a speed constraint at the FAF. The approach path was too steep to fly the Airbus CDA where you configure during descent to reach Vapp at 1000 ft. Even being fully configured at the FAF, often with 20 kts of tailwind, you are using a fair bit of speed brake to prevent a flap over speed.
Fleet Manager
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From: various places .....
the 1:60 rule
(With the risk of my being labelled a pita pedant), one needs to keep in mind that the 1:60 rule is a pilot-friendly approximation of the 1:57. (whatever decimals float your boat) rule.
(With the risk of my being labelled a pita pedant), one needs to keep in mind that the 1:60 rule is a pilot-friendly approximation of the 1:57. (whatever decimals float your boat) rule.
Thread Starter
Joined: Aug 2024
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From: Qatar
Thank you all for the replies.
I will take a pic of the actual data base for LOC 02 at VNKT since I'm going there in a few days. We stopped shooting the LOC there cuz the coding of the mcdu leaves you high on the approach flying a A333 with 1T bellow max landing weight (usually). Unlike the VOR which has the correct data in the mcdu to xcheck the chart alt and distance with the actual flight path of the aircraft. As mentioned in another post, we fly it NAV-FPA (No FLS installed) and xchecking the recommended altitudes of the chart while the mcdu has a different coding reduces your situation awareness. Any how, I just wanted to make sure that I was not missing something regarding the math. I'll post the pic of the coding once I have it for those who are interested.
I will take a pic of the actual data base for LOC 02 at VNKT since I'm going there in a few days. We stopped shooting the LOC there cuz the coding of the mcdu leaves you high on the approach flying a A333 with 1T bellow max landing weight (usually). Unlike the VOR which has the correct data in the mcdu to xcheck the chart alt and distance with the actual flight path of the aircraft. As mentioned in another post, we fly it NAV-FPA (No FLS installed) and xchecking the recommended altitudes of the chart while the mcdu has a different coding reduces your situation awareness. Any how, I just wanted to make sure that I was not missing something regarding the math. I'll post the pic of the coding once I have it for those who are interested.
Thread Starter
Joined: Aug 2024
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From: Qatar
It clearly wouldn’t, but the initial post was KLAX 24, not a special aircraft with special crew qualification where one would expect this information would be trained and any required tables issued. Few are going to run Excel spreadsheets on final approach.
In any case, the 1:60 rule says the 5.4* path is 540 ft/nm times ground speed in nm/min. 150 knots equals about 1350 fpm.
In any case, the 1:60 rule says the 5.4* path is 540 ft/nm times ground speed in nm/min. 150 knots equals about 1350 fpm.
Last edited by mabg88; 17th August 2024 at 18:08. Reason: spelling
Eidolon
Joined: May 2001
Posts: 2,244
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From: Some hole
Thank you all for the replies.
I will take a pic of the actual data base for LOC 02 at VNKT since I'm going there in a few days. We stopped shooting the LOC there cuz the coding of the mcdu leaves you high on the approach flying a A333 with 1T bellow max landing weight (usually). Unlike the VOR which has the correct data in the mcdu to xcheck the chart alt and distance with the actual flight path of the aircraft. As mentioned in another post, we fly it NAV-FPA (No FLS installed) and xchecking the recommended altitudes of the chart while the mcdu has a different coding reduces your situation awareness. Any how, I just wanted to make sure that I was not missing something regarding the math. I'll post the pic of the coding once I have it for those who are interested.
I will take a pic of the actual data base for LOC 02 at VNKT since I'm going there in a few days. We stopped shooting the LOC there cuz the coding of the mcdu leaves you high on the approach flying a A333 with 1T bellow max landing weight (usually). Unlike the VOR which has the correct data in the mcdu to xcheck the chart alt and distance with the actual flight path of the aircraft. As mentioned in another post, we fly it NAV-FPA (No FLS installed) and xchecking the recommended altitudes of the chart while the mcdu has a different coding reduces your situation awareness. Any how, I just wanted to make sure that I was not missing something regarding the math. I'll post the pic of the coding once I have it for those who are interested.
GURAS /+11500
C022º 5NM
CL02/+9300
C022º TRK022º 3-5.3º
FF02/+9000
C022º 1-5.3º
LOC11/+8420
C022º 3-5.3º
75LOC/+6720
C022º 2-5.3º
55LOC/+5590
C022º 1-5.3º
45LOC/+5280
C022º 2-5.3º
KTM/4750
This corresponds to the charted altitudes. Linear regression through the altitude/distance table on the Jepp chart works out that they used 5.21 degrees.
That to me looks like the coding inside 55LOC is wrong, should be -3.0º, looked at a machine with xLS, the approach is not in the data base.
This time of year its ISA+25 or more, so your true altitude at the FAF is more like 9500ft despite it indicating 9000ft on the altimeter, the non xLS machines are not temperature compensated. Something like FPA -5.9 will need to be flown to meet the profile. This should be flown in LOC-FPA.
Eidolon
Joined: May 2001
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From: Some hole
The chart has 5.31 degrees between FF02 and 55LOC, then 3 degrees from 55LOC to 3.1 DME for the VDP/MDA. If you were to draw a straight line from the FAF to the KTM VOR it would be a FPA of 4.25 degrees. The chart is designed so that the last 1200 feet is flown at 3 degrees from 55LOC.
Cargo rates into KTM are pretty good, and fuel is expensive (tanker), so it’s common to land near MLW. With the higher density height, TAS is up around 155-160 kts, plus a tailwind, on a 3 degree path you are pushing 900 fpm V/S on short final.
Cargo rates into KTM are pretty good, and fuel is expensive (tanker), so it’s common to land near MLW. With the higher density height, TAS is up around 155-160 kts, plus a tailwind, on a 3 degree path you are pushing 900 fpm V/S on short final.
Joined: Aug 2001
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From: Shropshire
Hi swh
Sorry, I was a bit rushed with my last response. I was commenting on your statement of: "That to me looks like the coding inside 55LOC is wrong, should be -3.0º" (which I agree with from what you have shown). I was wondering whether some manual data input was involved (unlikely, I know) and a gradient of 5.3%, which equates (roughly) to 3° was copied and pasted in error, just a thought.
Cheers
TeeS
Sorry, I was a bit rushed with my last response. I was commenting on your statement of: "That to me looks like the coding inside 55LOC is wrong, should be -3.0º" (which I agree with from what you have shown). I was wondering whether some manual data input was involved (unlikely, I know) and a gradient of 5.3%, which equates (roughly) to 3° was copied and pasted in error, just a thought.
Cheers
TeeS
