Final Approach Fix

[Mikehotel152]

I was chewing the cud on a flight the other day and was asked a question to which I could only give a common sense answer because I couldn’t put my finger on any rules.

For example: you’re flying a VORDME non-precision approach and ATC don’t give you timely descent. You cross the FAF 400 feet high and regain the appropriate profile and speed a mile or so later. For arguments sake you’re IMC, but there are check heights after the FAF and you’re happy with the profile thereafter.

Do you have any thoughts on legalities, with references, about proceeding if you’re above the profile at the FAF? And how high is too high?

Looking forward to your views. Thanks.

[FullWings]

Initial thoughts are that if you can comply with whatever SAC you operate under, then there are no obvious restrictions. You don’t want to go below published altitudes or infringe terrain clearance between checkpoints, so by necessity will be at or above - it is a NPA, after all. If ATC have delayed your descent (maybe for good reason) then being a bit high might be unavoidable. If you were capturing an ILS glideslope from above, being high at the OM wouldn’t necessarily be a problem either, as long as you could comply with SOPs.

As far as references go, I can’t find much, apart from in our OM A using RNAV/RNP, where there is a subtle difference between below path deviation, max 75’ at all times, and above path deviation, which is 75’ but only below 1,000’ AAL, so no restriction further back.

Depending on temperature and whether you are correcting for it or not, you are going to be following different paths through the sky, anyway.

[Check Airman]

I was chewing the cud on a flight the other day and was asked a question to which I could only give a common sense answer because I couldn’t put my finger on any rules.

For example: you’re flying a VORDME non-precision approach and ATC don’t give you timely descent. You cross the FAF 400 feet high and regain the appropriate profile and speed a mile or so later. For arguments sake you’re IMC, but there are check heights after the FAF and you’re happy with the profile thereafter.

Do you have any thoughts on legalities, with references, about proceeding if you’re above the profile at the FAF? And how high is too high?

Looking forward to your views. Thanks.

How high is too high? I’m not aware of any regulatory restriction, but your company will say you’re too high if you’re unable to meet their stable criteria.

[awair]

Stable Approach Criteria
GPWS Sink Rate
Intercept from above
Distance from threshold
VNAV vs basic modes?

The only one of these criteria that might be considered regulatory would be GPWS Caution. All the others would be Company SOPs.

Some airlines have a very different attitude towards airmanship!

[Mikehotel152]

Thanks for the replies. Interesting.

Aside from obvious issues with GPWS cautions, ‘gates’ and minima, I can’t see anything to prohibit being high at the FAF, much as you might capture a glide from above.

Obviously nobody plans to be high at the FAF, but it can happen due to ATC or environmental factors. Airmanship involves avoiding such events but presumably also safe recovery, which doesn’t always mean flying a missed approach.

[rudestuff]

Old-school NPAs used to be of the Dive & Drive variety, being careful not to go into any shaded bits. We try to fly these as a CDFA nowadays for noise and fuel burn, but as long as your lateral taking is good, you can be high most of the way down, just don't go below MDA(H) - its a NPA after all. Set -1500fpm and ride it down, if you haven't caught up with the profile by 1000agl go around. It helps to start configuring as soon a you know they've kept you high.