Non-Precision approach with Glide of 3.5
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From: the blue yonder
Non-Precision approach with Glide of 3.5
Just wanted to hear your thoughts/explanations on this: Say a published VOR approach is 06 degrees offset to the runway track and a published descent angle of 3.5 degrees and the descent starts from approx 8nm from the runway threshold with no significant terrain on the approach path , if you carry out a visual approach to said runway, would you therotically still need to maintain a descent angle of 3.5? i.e. slighlty higher rate of descent than 3 degrees. Thanks
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From: IRS NAV ONLY
There's usually a reason why the instrument approach has a steeper than normal glidepath, is offset, or why there isn't one in the first place - could be also noise restrictions, not just obstacles.
Generally the safest bet is to just fly a visual approach as an overlay of the IAP for that runway, joining at a safe distance from threshold.
Generally the safest bet is to just fly a visual approach as an overlay of the IAP for that runway, joining at a safe distance from threshold.
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From: Somewhere at the Milky Way
If the instrumental procedure is offset because of terrain (terrain penetrates the coverage area) and the glide is higher due the same, then a sensible thing to do is to transition to visual, align yourself to the runway. Brief that once visual you will transition to the PAPI, thus for some limited time the vertical speed will be higher, but then you will follow a normal vertical approach.
Thread Starter
Joined: Apr 2007
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From: the blue yonder
If the instrumental procedure is offset because of terrain (terrain penetrates the coverage area) and the glide is higher due the same, then a sensible thing to do is to transition to visual, align yourself to the runway. Brief that once visual you will transition to the PAPI, thus for some limited time the vertical speed will be higher, but then you will follow a normal vertical approach.
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From: Somewhere at the Milky Way
By best judgement means use of all available tools, but not necessarily use them all. For example, you may use the PAPI guidance to follow its descent guidance. In this particular case, since you went below the instrumental vertical path and following a 3˚ descent angle, the altitude vs DME readings won't match but they will converge in the final stages of the approach, and most of the time you will be below the DME vs altitudes readings. That is normal if you are following the PAPI guidance, but remember a visual approach can disregard PAPI guidance too, and you aim for the aiming zone and the runway mid section visually. That's all you need.
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From: Shropshire
Hi Maverick
The final approach gradient is calculated between the final approach fix/procedure altitude and the runway threshold/crossing altitude (usually 50ft above THR) so the gradient doesn't alter with an offset.
It is also worth mentioning (although it doesn't really affect your question) that if the final approach segment is offset by more than 15° from the runway alignment, the circling approach minima will be applied. Between 5° and 15° increased OCAs apply (sorry, I should have checked PANS-OPS before going to print!!)
The above are for PANS-OPS.
Cheers
TeeS
On a second read of your question, I realise I have probably misunderstood it.
The final approach gradient is calculated between the final approach fix/procedure altitude and the runway threshold/crossing altitude (usually 50ft above THR) so the gradient doesn't alter with an offset.
It is also worth mentioning (although it doesn't really affect your question) that if the final approach segment is offset by more than 15° from the runway alignment, the circling approach minima will be applied. Between 5° and 15° increased OCAs apply (sorry, I should have checked PANS-OPS before going to print!!)
The above are for PANS-OPS.
Cheers
TeeS
On a second read of your question, I realise I have probably misunderstood it.
Last edited by TeeS; 21st April 2025 at 22:55. Reason: Poor memory of PANS-OPS for offset approaches!!
Thread Starter
Joined: Apr 2007
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From: the blue yonder
Hi Maverick
The final approach gradient is calculated between the final approach fix/procedure altitude and the runway threshold/crossing altitude (usually 50ft above THR) so the gradient doesn't alter with an offset.
It is also worth mentioning (although it doesn't really affect your question) that if the final approach segment is offset by more than 5° from the runway alignment, the circling approach minima will be applied.
The above are for PANS-OPS.
Cheers
TeeS
On a second read of your question, I realise I have probably misunderstood it.
The final approach gradient is calculated between the final approach fix/procedure altitude and the runway threshold/crossing altitude (usually 50ft above THR) so the gradient doesn't alter with an offset.
It is also worth mentioning (although it doesn't really affect your question) that if the final approach segment is offset by more than 5° from the runway alignment, the circling approach minima will be applied.
The above are for PANS-OPS.
Cheers
TeeS
On a second read of your question, I realise I have probably misunderstood it.
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From: UK
Thanks for the reply, so it means, if I do a visual approach for said runway I will still need to follow gradient of 3.5 degrees? and in case of the VOR approach, once I aligned with runway track and fly visually the approach the gradient of 3.5 degrees will still be applicable ?
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From: Shropshire
Thanks for the reply, so it means, if I do a visual approach for said runway I will still need to follow gradient of 3.5 degrees? and in case of the VOR approach, once I aligned with runway track and fly visually the approach the gradient of 3.5 degrees will still be applicable ?
I come from a helicopter background where, although we generally fly stabilised constant angle approaches, life is rather more flexible than the fixed wing world so I am not best qualified to comment; however, I would think that if you have started on an instrument approach and become visual then it would be better to continue on that flight path angle than to de-stabilise the approach from 3.5° to 3.0°. As JH suggests, if you are flying a visual approach then the instrument procedure is irrelevant.
As an aside, if the instrument procedure is steeper than 3.0° then that is probably due to an obstacle late in the intermediate segment or prior to a step down fix in the final approach segment, that has prevented descent to a lower altitude for the final approach fix.
Cheers
TeeS
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From: Somewhere at the Milky Way
Once visual, you are on your own. You will fly whatever it takes to ensure own separation with terrain and other traffics (and any restricted/prohibited areas). You may follow the PAPI guidance or you may not, you may use the VDEV indicator or not, you may use the DME vs altitudes charts or you may not, its up to what the flight crew has briefed and agreed to by following operator manuals and amendments and own judgement.
Thread Starter
Joined: Apr 2007
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From: the blue yonder
Once visual, you are on your own. You will fly whatever it takes to ensure own separation with terrain and other traffics (and any restricted/prohibited areas). You may follow the PAPI guidance or you may not, you may use the VDEV indicator or not, you may use the DME vs altitudes charts or you may not, its up to what the flight crew has briefed and agreed to by following operator manuals and amendments and own judgement.
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From: Shropshire
Hi again Maverick
No, I wouldn't draw that conclusion. The gradient of the final approach is not designed to avoid obstacles, it is just the slope that takes you from the intermediate segment procedure altitude (which will give at least 492ft clearance from obstacles/terrain in the intermediate segment) to (typically) 50ft above the threshold. Clearance above obstacles/terrain (246ft) in the final segment is provided by the obstacle clearance altitude (OCA) which is used to give the minimum descent altitude (MDA). So, the steady gradient to fly from the intermediate segment altitude at the final approach fix might be 6.1% (3.5°) however, you could fly a 'dive and drive' approach (subject to your national regulations [and limited to 15% (8.5°) by PANS-OPS]) straight down to your MDA and you would still be clear of all obstacles/terrain by at least 246ft.
Don't forget, you could also have a straight in ILS or LPV approach alongside your offset VOR approach @ 3.5°, perfectly lined up with the runway and with an approach gradient of 5.3% (3.0°).
Hope that helps.
TeeS
No, I wouldn't draw that conclusion. The gradient of the final approach is not designed to avoid obstacles, it is just the slope that takes you from the intermediate segment procedure altitude (which will give at least 492ft clearance from obstacles/terrain in the intermediate segment) to (typically) 50ft above the threshold. Clearance above obstacles/terrain (246ft) in the final segment is provided by the obstacle clearance altitude (OCA) which is used to give the minimum descent altitude (MDA). So, the steady gradient to fly from the intermediate segment altitude at the final approach fix might be 6.1% (3.5°) however, you could fly a 'dive and drive' approach (subject to your national regulations [and limited to 15% (8.5°) by PANS-OPS]) straight down to your MDA and you would still be clear of all obstacles/terrain by at least 246ft.
Don't forget, you could also have a straight in ILS or LPV approach alongside your offset VOR approach @ 3.5°, perfectly lined up with the runway and with an approach gradient of 5.3% (3.0°).
Hope that helps.
TeeS
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From: Somewhere at the Milky Way
I 1000% agree with you on this, thats what a visual approach is. but my question or uncertainity is this that since there exist a regulatory approach procedure with a defined glide of 3.5degrees , would it not be wise to consider the glide for the visual approach to be inlined with what is published?
Yet, you can decide to do a visual approach but respecting the charted approach guidance and use that info as a back up to your visual approach. Then distances vs altitudes will match up, the guidance from the instruments will be good enough to follow but the PAPI will show you as high on a 3˚ profile (that is normal but has to be briefed as well).
Or you can fly a full instrumental approach every time and the same as above applies.
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From: My views - Not my employer!
One little side issue. If you load the instrument approach, then fly a visual approach at a shallower angle, you may find your aircraft shouting 'glideslope' at you. This is very aircraft dependent and not all do it, but if your's does then have a plan to get around it....
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From: Village of Santo Poco
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From: USA
One little side issue. If you load the instrument approach, then fly a visual approach at a shallower angle, you may find your aircraft shouting 'glideslope' at you. This is very aircraft dependent and not all do it, but if your's does then have a plan to get around it....
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From: My views - Not my employer!
It's a 787 thing (hence my wording originally). Being below both the glideslope (ILS/GLS) or FMC computed glidepath (NPA's/RNAV) can trigger a warning.
At the end of the day, if you're on a non precision approach on a boggy day, would you not be happy to know there was a little bit of protection?
At the end of the day, if you're on a non precision approach on a boggy day, would you not be happy to know there was a little bit of protection?
