IFR Question
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IFR Question
IFR Experts !
I am seeking clarification on some IFR questions which I am not certain on. I am not sure if the explanation below is suffice however as an example. Please feel free to add in any vital information that could clarify such a maneuver if possible :
Wind : 20-30 Northerly
Cloud: Some SCT cloud around the MDA of 800’ Essentially may not be possible to break visual at 800’ MDA
1. Are you allowed to let yourself down on an approach which has a lower MDA e.g. Rwy 18 ILS Avalon even though wind conditions depict the opposite runway to have a greater chance to break visual and then climb to the circling minima for a Cat B aircraft 300' above the highest obstacle. Of course then obey the visual maneuvering laws for circling approach Rwy36?
2. How is the highest obstacle determined? Can you use the airport chart to determine that in order to maintain 300’ above the highest obstacle during daylight? If not how do you calculate the highest obstacle ?
Thanks in advance
I am seeking clarification on some IFR questions which I am not certain on. I am not sure if the explanation below is suffice however as an example. Please feel free to add in any vital information that could clarify such a maneuver if possible :
Wind : 20-30 Northerly
Cloud: Some SCT cloud around the MDA of 800’ Essentially may not be possible to break visual at 800’ MDA
1. Are you allowed to let yourself down on an approach which has a lower MDA e.g. Rwy 18 ILS Avalon even though wind conditions depict the opposite runway to have a greater chance to break visual and then climb to the circling minima for a Cat B aircraft 300' above the highest obstacle. Of course then obey the visual maneuvering laws for circling approach Rwy36?
2. How is the highest obstacle determined? Can you use the airport chart to determine that in order to maintain 300’ above the highest obstacle during daylight? If not how do you calculate the highest obstacle ?
Thanks in advance
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This has been discussed before...at length...with both opposing sides continuing to disagree with the other. Bit hard to pick the correct outcome, even though it's simply spelled out in the AIP. http://www.pprune.org/dg-p-general-a...-approach.html.
By day, you can be below the circling MDA as long as you keep your 300ft etc. It can be dangerous if you don't know the area and the rule needs to be used with caution. Where I fly we have a VORDME straight-in approach which requires circling for the reciprocal runway once we break visual when wind conditions dictate.
How to know where those obstacles are is another matter. The aerodrome operator would have maps, so could the council. Something like a WAC is not nearly good enough.
By day, you can be below the circling MDA as long as you keep your 300ft etc. It can be dangerous if you don't know the area and the rule needs to be used with caution. Where I fly we have a VORDME straight-in approach which requires circling for the reciprocal runway once we break visual when wind conditions dictate.
How to know where those obstacles are is another matter. The aerodrome operator would have maps, so could the council. Something like a WAC is not nearly good enough.
What tmpffisch said, including you must adhere to all requirements relevant to descent below MDA. That might be easier said than done if you're required to keep the landing threshold or items associated with it in sight at 300ft on a runway that could be 3000m long. (youre landing the far end after all).
What they said.
It's pretty much a common sense thing at the end of the day though. Sure you can descend down to 300' above obstacles by day assuming all other criteria is met, but sometimes you just won't feel comfortable doing so if you're local knowledge is lacking.
It's the same with the old "but how do you know if you have 4.2k vis when you break visual"? Well you don't exactly. Its common sense. If you can see enough of the runway to make a safe landing then that is what most people are looking for.
It's where the importance of experience and making command decisions comes into the equation.
It's pretty much a common sense thing at the end of the day though. Sure you can descend down to 300' above obstacles by day assuming all other criteria is met, but sometimes you just won't feel comfortable doing so if you're local knowledge is lacking.
It's the same with the old "but how do you know if you have 4.2k vis when you break visual"? Well you don't exactly. Its common sense. If you can see enough of the runway to make a safe landing then that is what most people are looking for.
It's where the importance of experience and making command decisions comes into the equation.
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Thank you for your replies and tmpffisch for your reference link to a similar question
http://www.pprune.org/dg-p-general-a...-approach.html. which essentially answers (debates) both my queries.
If people wish to continue discussing further ideas please by all means.
Thanks again.
http://www.pprune.org/dg-p-general-a...-approach.html. which essentially answers (debates) both my queries.
If people wish to continue discussing further ideas please by all means.
Thanks again.
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Everyone else has summed it up very well, but I'll add my two cents worth.....
That's the $64,000 question! you would need very detailed information about obstacles withing the circling area. Spot heights on your DAP's would be the best indication.
When doing the oral part of my last renewal my testing officer asked me much the same question, but with a downwind of only 10 knots. We both agreed that doing a circling approach to land into wind is unnecessary and dangerous if the weather is marginal. If the downwind or crosswind component is to much for you aircraft (and your skills) it's better to proceed to your alternate.
That's my view from real world IFR flying, however the AIP does state that you can legally circle if you wish to.
How to know where those obstacles are is another matter.
When doing the oral part of my last renewal my testing officer asked me much the same question, but with a downwind of only 10 knots. We both agreed that doing a circling approach to land into wind is unnecessary and dangerous if the weather is marginal. If the downwind or crosswind component is to much for you aircraft (and your skills) it's better to proceed to your alternate.
That's my view from real world IFR flying, however the AIP does state that you can legally circle if you wish to.
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I think you'll find that by and large that all circling MDA's for a particular aerodrome will be the same... i.e. even if an ILS S-I minima is dramatically lower than say the NDB-A... its (ILS) circling minima will usually be the same as other circling approaches for the same aerodrome.
There is nothing legally stopping you from doing a S-I approach and deciding later to switch to a circling maneuver provided you meet all of the circling conditions (On track until inside the circling area with vis >min along intended flight path with approach end of rwy in sight and above MDA until on normal descent profile). Doing this can enable landing in lower visibility but requires a higher cloud base... however you need to assess the risk of unnecessary circling.
The company I work for actively discourages circling unless there is no S-I approach or it is VMC by day.
There is nothing legally stopping you from doing a S-I approach and deciding later to switch to a circling maneuver provided you meet all of the circling conditions (On track until inside the circling area with vis >min along intended flight path with approach end of rwy in sight and above MDA until on normal descent profile). Doing this can enable landing in lower visibility but requires a higher cloud base... however you need to assess the risk of unnecessary circling.
The company I work for actively discourages circling unless there is no S-I approach or it is VMC by day.
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In reality I would doubt ATC at a busy airport would allow a downwind ILS and circling approach to be made as it would stuff up their sequencing
ATC will nominate an approach that in their opinion will give you the best chance of a successful approach taking into account all the conditions. If you want something different ask and you WILL receive.
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I'm with "Beat Ups". Circling approaches can be dangerous to say the least. If you are unfamiliar with the aerodrome, right on the minima, at night or in any way committed to circling then the safety barriers are quickly been eroded. If you don't fly too close to the ground you can't hit it. Many crash comics talk about IFR approaches that end in disaster after a circling approach. A place like Avalon is a lot safer because ATC can tell you what approaches have been successful but if you are on your own in the sticks or after hours then alternates are life savers!!!
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CAAPs 178-1(1)
If anyone is interested I found CAAPs 178-1(1) useful in understanding how non precision approaches are designed in particular relevance to my question on page 11.
