My company also does not have the table about the FPA correction table.

So what guys out there doing on FPA approaches when it comes to corrections to descent angle?

Vilas? You seem to be really knowledgeable about Airbus.

tcasblue
I don't have any information on FPA correction.But cold temperature correction to Final Descent altitude and minima is a must otherwise you'll bust it. FPA if not corrected it will be in error but to safer side and as you carryout Dist/Ht check you will have to keep correcting it. All I can say is with.FLS option installed it is corrected through FMS and is flown in FINAL APP. So Airbus may be leaving it to the operator's.

So basically AB say , ask your FltOps to calculate and produce the data or buy an a/c with FLS capability...

FLS aside - with the advent of LNAV / VNAV there are fewer occasions where cold weather temp correction is required as these charts have a temperature range.

Nick - it's not that straight forward to get FLT OPS to generate a table that is really accurate as the temp correction changes with the height over ground, not height AAL - so it's different for every runway. And inversions (as are common in extreme cold high pressure systems) play with the math again as the cold temperature formulae rely on a uniform decrease in air temp.

Just dial in a few more tenths depending how cold it is and PM monitors high/low and PF adjusts - like any NPA. You are aiming for a CDFA but it doesn't always work, through chart design or adjusted FPA not quite accurate. I just checked some GoPro footage and I made 4 FPA adjustments between 2500' and minima (340') when it was ISA-40ish.

If it helps any, there’s an app called CoolAltitude which will calculate all the relevant corrections for you (screenshot attached). Obviously all the usual caveats apply - for guidance only, doesn’t replace official documentation, etc etc.


https://cimg3.ibsrv.net/gimg/pprune....b3412702d3.png

If you use the same correction like the altitude correction, it should more or less work out. 4% for every 10 degrees below ISA. That seems to be the case in the table posted by itsnotthatbloodyhard.
E.g. OAT -10 = ISA -25 gives a correction of 10%.
If the approach starts at 3000’ AGL, you correct it to 3300’. About 3.3 FPA should bring you at the (corrected) MDA at the right place.

Just remember that (in the 10% case) initially you’ll be 300’ high according the altitude vs. distance table. At 2000’ you’ll be 200’ high etc.
Or you do a bit of extra work prior the approach and you correct the altitude vs. distance table. Remember to calculate the % from the height, not altitude, as this is a common mistake.
​​​

Edit:
By the way, at my previous company, we didn’t correct any altitudes down to -15 OAT. Except for the MDA. I think that at EasyJet it’s down to -10 OAT. I assume it’s because the margin on the published altitudes is probably sufficient down to those temperatures.

Thanks,

Maybe you can input the altitudes and temperature for the approach that was used by the accident aircraft and see what descent angle is required.

I’ve just put some numbers into the cold wx app that we use - temp, elevation, VDA, MDA and it comes out with 3.32deg

HtH

Thanks,

The crew used 3.5 degrees. That might explain why they were low on approach if 3.3 degrees was the angle that should have been used. As we know, there was no crosscheck of altitude versus distance and their company procedures manual(used instead of Airbus issued manuals) did not require them to crosscheck altitude versus distance.

It would be interesting to see the airlines formula table(or whatever it is) that was used to come up with 3.5 degrees as the crew apparently followed this table properly..

Guys why doing so difficult ? There is no table, FCOM or QRH that can exactly tell you what FPA you must use in case of low temperature correction during NPA...keep it easy, do your corrections at minimum and FDP, the rest as usual check your DME/elevation against charted figures.

Mmmm. The problem is that as it gets colder the range/height figures get less and less accurate. At what point are you going to decide that they need correcting? -5, -10, -15? Doing the calculations manually and writing them on a scrap of paper is a right ballsache; using a modern cold wx app is really easy so why not do it?

It appears that this is what one has to do. Your own corrections for each distance/altitude point. If you are fortunate, your company has provided you with a table or an app to make it easy.

But I still don’t understand why the descent angle table is in the A330 manual and not the A320 manual.

Sorry - can’t help with that. Boeing pilot me, in fact I didn’t even know that FPA was a thing until recently!

The FPA correction chart in your QRH is a company specific DU.
Airbus abandoned the FPA correction chart because they don’t want crew to blindly select an FPA and then stop monitoring ‘alt vs distance’. They wanted to avoid the false sense of safety after having extracted a single number from the chart. In the same sense we should not blindly rely on a nominal FPA -3.0 to always do the trick in ISA conditions.
What about hot temperature corrections? And so on......
-You select what you need and adjust, by active monitoring and periodic crosschecking.
-The FPA is baro-inertial and only correct in ISA conditions. (Baro-long term)

Could not agree more. Even during normam ISA standard NPA we do monitor DME/altitude during final and make needed corrections as needed. I cannot understand how you can just get a figure for an FPA from a book and blindly applying it.

I agree. We don’t just estimate the drift angle at the descent point, adjust the heading once and then wait for a runway to appear! Or maybe some operators do?

OPEN DESCENT
Using a cold temperature corrected FPA and not doing D/Ht check are two different things. Both are required. If you set ISA chart FPA and you find you are in error at the first check then after correcting when you go back to the same FPA you will again be in error because FPA is not appropriate. So you start the descent at corrected FPA but still check after I nm. If in error do the required correction and when correct reset the corrected FPA. This way you have better chance of tracking correct vertical path.

I wonder if the above is adequately explained to pilots; i.e. if disturbed, the aircraft will not regain the original "glide-slope" but will parallel it, either above or below.

Certainly on any NPA where visibility is low, (but in limits for the NPA); I would feel extremely uncomfortable NOT checking my altitude at every mile on the way down. How bizarre for an airline to say it was not necessary. Basic piloting and SA, surely?

on the sacrcastic side
 

To pilots, such a thing need not to be explained at all.

Moreover, in case when a company detailed a specific automation drill in their manuals (such as LNAV/FPV 2D APCH in sub-zero temps) and omitted to-reiterate distance/altitude principle for the sake of brevity or whatever, pilots would do it anyhow.

Not to mention any pilot examiner would need to discontinue the bi-yearly check-ride should the applicants ignore such basic protocol.

There is something rotten west of the Denmark's largest island.