Descent below MDA in NZ
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Descent below MDA in NZ
Some debates on this topic have come up at work. There are some differing interpretations of the way the AIP defines the rules for descent below MDA, particularly WRT to circling approaches.
Assuming you meet all the criteria for descent below MDA (vis, reference to airfield etc) when would you say it is acceptable to actually descend? Once established on glidepath? On centreline? As required in order to fly an approach using normal descent rates and manoeuvres?
On a related topic, if you were to arrive at MDA and meet the minimum vis requirements for the approach but cannot see the airfield because, for example, of weather between you and the airfield, would you consider flying a visual approach? That is assuming you can maintain visual reference to the ground and have a reasonable assurance that you can complete the landing.
Remember these are q's as specific to the NZ regs which are different to Aus. I'm interested in any opinions and company rules you have to offer....
Assuming you meet all the criteria for descent below MDA (vis, reference to airfield etc) when would you say it is acceptable to actually descend? Once established on glidepath? On centreline? As required in order to fly an approach using normal descent rates and manoeuvres?
On a related topic, if you were to arrive at MDA and meet the minimum vis requirements for the approach but cannot see the airfield because, for example, of weather between you and the airfield, would you consider flying a visual approach? That is assuming you can maintain visual reference to the ground and have a reasonable assurance that you can complete the landing.
Remember these are q's as specific to the NZ regs which are different to Aus. I'm interested in any opinions and company rules you have to offer....
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I can remember the old Tokoroa NDB approach (off the 1413 radio station), at minima, vis 5 Km, but still another 6.5km to get to the airfield.
Remember the rule throws in the "pilot must have resonable assurance he can make the landing using normal manouvers and rates of descent"
Remember the rule throws in the "pilot must have resonable assurance he can make the landing using normal manouvers and rates of descent"
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Why would descent below MDA have anything to do with your position in relation to glideslope / centreline? (Why also would someone use precision approach terminology when referring to circling and non-precision approaches???)
An MDA exists to ensure terrain clearance while IMC - so if you meet all the criteria for descent below MDA, you are therefore in VMC, and able to provide that terrain clearance visually.
When can you descend below MDA? When you meet the criteria for descent below MDA.
If you ask me, sounds like they have some VERY interesting rules in the land of sexy sheep.....
An MDA exists to ensure terrain clearance while IMC - so if you meet all the criteria for descent below MDA, you are therefore in VMC, and able to provide that terrain clearance visually.
When can you descend below MDA? When you meet the criteria for descent below MDA.
If you ask me, sounds like they have some VERY interesting rules in the land of sexy sheep.....
The side step off the ALFA at Vegas created some variations in interpretations too.
I forget the particulars. Maybe someone can detail them, as that approach should be a good platform to use in discussing the rules governing descent below MDA.
I forget the particulars. Maybe someone can detail them, as that approach should be a good platform to use in discussing the rules governing descent below MDA.
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Just because you meet the requirements for descent below MDA; does not mean in anyway that you are in VMC. Some approachs give MDA's and minimum vis which are well below that whcih Part 91 stipulates as being VMC.
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Sexual Chocolate I think you will find that the sheep in Aus are sexier;
You got no grass to feed them, and no water either, so they are supermodel slim!!
Why do you think we all come over for our holidays
You got no grass to feed them, and no water either, so they are supermodel slim!!
Why do you think we all come over for our holidays
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Sexual Chocolate, I think you'll find the rules in Oz are pretty interesting too, looks like you need to go read them. Once you've done that, try thinking about them. You'll find that your position relative to glidepath and centreline are both critical when electing to descend below MDA - even though you're flying a non-precision approach.
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I confess I don't have much experience in this area - less than a thousand hours IFR. But having scared myself once at WK, I have reread the rules quite carefully.
It seems to me that you can't descend below MDA if you don't have the runway or approach lights in sight, regardless of whether the weather meets minimums.
I don't think continuing on a visual approach is OK either, because a visual approach requires VFR met - 5000m and 600' agl cloud. If you've got that, you've probably got the runway in sight (or can continue at MDA on final approach track until you do.)
I would not descend below circling MDA until on late downwind / base, because it seems that's what the rule says. But if someone else reads it differently, I wouldn't argue with them!
cheers to all,
O8
It seems to me that you can't descend below MDA if you don't have the runway or approach lights in sight, regardless of whether the weather meets minimums.
I don't think continuing on a visual approach is OK either, because a visual approach requires VFR met - 5000m and 600' agl cloud. If you've got that, you've probably got the runway in sight (or can continue at MDA on final approach track until you do.)
I would not descend below circling MDA until on late downwind / base, because it seems that's what the rule says. But if someone else reads it differently, I wouldn't argue with them!
cheers to all,
O8
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Thanks for your thoughts, Oktas8. You're quite right in saying:
However this I don't think is right:
As I read the rules, as long as you can see the ground and you are reasonably assured you can complete the landing, you're good to go for a visual approach. No requirement to comply with VFR met minima - nor to be able to see the airfield! This is probably not how the rule was conceived, but that's how it's written.
I agree with you here:
I wonder what others think? Cheers,
It seems to me that you can't descend below MDA if you don't have the runway or approach lights in sight, regardless of whether the weather meets minimums.
a visual approach requires VFR met - 5000m and 600' agl cloud
I agree with you here:
I would not descend below circling MDA until on late downwind / base, because it seems that's what the rule says.
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Cant say Ive ever heard of a met minima on a visual approach???? As far as im aware the only requirement to take a visual approach in uncontrolled airspace is that you have the ground in sight and have reasonable assurance that a landing can be made.
My guess is that this is what lead to the 'dive and drive approach'.
My guess is that this is what lead to the 'dive and drive approach'.
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W.E. - sorry bro no offense intended. It was just that your thread looked so lonely with only 1 reply, two days after posting!
It's a little sad but sometimes it takes a less-than-well-thought-out response and a bit of mud slinging (the sheep thing) to get the debate going.
No one likes to offer advice but people LOVE to correct someone who's wrong, especially when that person's an arsehole
It's a little sad but sometimes it takes a less-than-well-thought-out response and a bit of mud slinging (the sheep thing) to get the debate going.
No one likes to offer advice but people LOVE to correct someone who's wrong, especially when that person's an arsehole
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Flyby kiwi,
What would be the minimum cloud/viz requirements then? I seem to recall a passage of text along the lines of "when carrying out a visual approach (either ATC cleared or in uncontrolled airspace), the pilot is initiaing visual flight and the visual met minima applicable to that operation apply" - that minima depending on your aircraft/operation and in thus being line with part 91, 135, 125 or 121. I may be wrong, but that is the way I interpret a visual approach. Reason being I find a statement like
quite a scary prospect if a pilot sights a hole below MDA on an approach and just takes it without regard to any minima by just 'doing a visual approach.' We are professional pilots and should not want to negate all the protections and buffers built into things such as MDA's by carrying out willy nilly visual approaches.
Anyway, Mr Johns was referring to circling visually off an instrument approach, not when on a visual approach. The requirements for descent below MDA should be known by us all from Part 91. In addition, for a circling approach from PANS OPS Vol. 1 part III, Chapter 4, it is said that once visual reference has been established at MDA, descent may be continued at PILOT DISCRETION if:
1) Visual reference can be maintained throughout the circ. app.
2) The pilot can see the runway threshold lights, approach lights or any markings identifying the approach end of the runway (I always wondered in the case of doing for example a 07 approach and then circle to land on 25 what the 'approach' end of the runway was!)
3) {probably most pertinent to Capt Johns} the required obstacle clearence can be maintained to a point from where a constant rate of descent can be held to the intended touchdown point.
If circling at MDA depending on speed/category, obstacle clearance is assured at that altitude within 1.68, 2.66, 4.2 or 5.28nm circ. radius from the threshold of 295ft for Cat A,B and 394ft for Cat C,D (PANS OPS). Personally I would not go below MDA UNNECESSARILY whilst circling until somewhere around final/maybe base to comply with 3) above, but that statement IMHO does give leeway to go below MDA before final (base or even downwind) depending on where your "point from which a constant rate of descent to touchdown" is. Of course min vis, visual obstacle clearance, and pilot discretion (probably airmanship here) dictate too.
With regard to
(and for the old Tokoroa and similarly Nelson's Appleby approach and others) I read the rules as saying that you can continue past the missed approach point AT MDA if you have visual reference and the minimum viz but cannot descend below MDA until the requirements (that big list in part 91) of some part of the runway/airport is distinctly visible and identifiable to the pilot. So at Tokoroa could carry on past the 6.5km MAP not below MDA with at least 5km viz and could then descend when the requirements for going below MDA are met. Because of this I would not fly a visual approach in that situation because if I can't hold MDA till I see the airfield I probably don't wont to be doing it on a visual approach either! As I said earlier, I also consider I have met minima to comply with in the case of a visual approach.
Ok let the attacks begin.
Cant say Ive ever heard of a met minima on a visual approach????
As far as im aware the only requirement to take a visual approach in uncontrolled airspace is that you have the ground in sight and have reasonable assurance that a landing can be made.
Anyway, Mr Johns was referring to circling visually off an instrument approach, not when on a visual approach. The requirements for descent below MDA should be known by us all from Part 91. In addition, for a circling approach from PANS OPS Vol. 1 part III, Chapter 4, it is said that once visual reference has been established at MDA, descent may be continued at PILOT DISCRETION if:
1) Visual reference can be maintained throughout the circ. app.
2) The pilot can see the runway threshold lights, approach lights or any markings identifying the approach end of the runway (I always wondered in the case of doing for example a 07 approach and then circle to land on 25 what the 'approach' end of the runway was!)
3) {probably most pertinent to Capt Johns} the required obstacle clearence can be maintained to a point from where a constant rate of descent can be held to the intended touchdown point.
If circling at MDA depending on speed/category, obstacle clearance is assured at that altitude within 1.68, 2.66, 4.2 or 5.28nm circ. radius from the threshold of 295ft for Cat A,B and 394ft for Cat C,D (PANS OPS). Personally I would not go below MDA UNNECESSARILY whilst circling until somewhere around final/maybe base to comply with 3) above, but that statement IMHO does give leeway to go below MDA before final (base or even downwind) depending on where your "point from which a constant rate of descent to touchdown" is. Of course min vis, visual obstacle clearance, and pilot discretion (probably airmanship here) dictate too.
With regard to
On a related topic, if you were to arrive at MDA and meet the minimum vis requirements for the approach but cannot see the airfield because, for example, of weather between you and the airfield, would you consider flying a visual approach?
Ok let the attacks begin.
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Capt on Heat......
There are no cloud base / viz requirements.
This from the AIP........
4.23 Visual Approach — Uncontrolled Airspace
4.23.1 Pilots in uncontrolled airspace may carry out a visual approach
provided the pilot:
(a) can maintain visual reference to the terrain; and
(b) the ceiling is not below the initial approach level; OR
(c) the pilot has reasonable assurance at the initial approach level or at
any time during the instrument approach procedure that the
meteorological conditions will permit a visual approach and landing
to be accomplished.
4.23.2 For a visual approach at night, it is essential that the pilot has the
runway lights in sight. Sighting only of the aerodrome beacon, REIL or
approach lights is insufficient.
This from the AIP........
4.23 Visual Approach — Uncontrolled Airspace
4.23.1 Pilots in uncontrolled airspace may carry out a visual approach
provided the pilot:
(a) can maintain visual reference to the terrain; and
(b) the ceiling is not below the initial approach level; OR
(c) the pilot has reasonable assurance at the initial approach level or at
any time during the instrument approach procedure that the
meteorological conditions will permit a visual approach and landing
to be accomplished.
4.23.2 For a visual approach at night, it is essential that the pilot has the
runway lights in sight. Sighting only of the aerodrome beacon, REIL or
approach lights is insufficient.
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Yes, yes, but regarding (c), How can the pilot have reasonable assurance? What ARE the meteorological conditions that permit a visual approach and landing to be made? What weather do YOU base requesting (or if in 'G' airspace, carrying out) a visual approach on? Surely it's not just if you can see the ground?!!!
I see it that the meteorological conditions that permit a visual approach to be made are Visual Meteorological Conditions, VMC.
From CAR Part 1, "Visual Meteorological Conditions means meteorological condtions expressed in terms of visibility, distance from cloud and ceiling equal to or better than specified minima." So what are the specified minima? CAA/airways might have dropped the ball on this one but I see them as those pertaining to VFR as per the applicable rule for the aircraft/operation. Am I unsafe for thinking this? Where is any other minima specified? I hope it's not hidden in the depths of a still applicable reg from 1953 or a CASO. I suppose what we are really bitching about is the inaccuracy, incompleteness and ambiguity of the rules etc. I'd like to think that most pilots would apply a generous amount of airmanship to the apparent lack of guidance/clarity from the authority.
Also an amendment to my earlier post. DURING a circling manoeuvre the pilot must have an identifiable part of the aerodrome in sight at or above MDA or a missed approach must be executed (from AIP ENR 1.5, 4.17). Certainly (in the case of for example the Appleby approach at NS) this would negate my previous comment-apologies. For other approaches though it may depend on when you interpret the circling to have commenced........!
I see it that the meteorological conditions that permit a visual approach to be made are Visual Meteorological Conditions, VMC.
From CAR Part 1, "Visual Meteorological Conditions means meteorological condtions expressed in terms of visibility, distance from cloud and ceiling equal to or better than specified minima." So what are the specified minima? CAA/airways might have dropped the ball on this one but I see them as those pertaining to VFR as per the applicable rule for the aircraft/operation. Am I unsafe for thinking this? Where is any other minima specified? I hope it's not hidden in the depths of a still applicable reg from 1953 or a CASO. I suppose what we are really bitching about is the inaccuracy, incompleteness and ambiguity of the rules etc. I'd like to think that most pilots would apply a generous amount of airmanship to the apparent lack of guidance/clarity from the authority.
Also an amendment to my earlier post. DURING a circling manoeuvre the pilot must have an identifiable part of the aerodrome in sight at or above MDA or a missed approach must be executed (from AIP ENR 1.5, 4.17). Certainly (in the case of for example the Appleby approach at NS) this would negate my previous comment-apologies. For other approaches though it may depend on when you interpret the circling to have commenced........!
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I'd like to think that most pilots would apply a generous amount of airmanship to the apparent lack of guidance/clarity from the authority.
How about this for an interpretation - If you can see where you are and where you're going and you're not going to hit anything, or break any of the other rules, you should be fine. Works for me, and I don't have to try to remember anymore meaningless numbers
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Yes discretion is great and our judgement is why we're payed the big bucks, but
I think aviation has matured a bit from that.
Exactly.
you should be fine
How much guidence do you need?
or break any of the other rules,
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There might be some confusion here between a "visual approach" and descending below MDA on an "instrument approach".
these are two very different approach methods and require different condidtions to be met during both day and night.
QUOTE
Part 91.413(c)
Operation below DA, DH, or MDA. Where a DA, DH, or MDA is
applicable, no pilot-in-command shall operate an aircraft at any aerodrome below the MDA, or continue an instrument approach procedure below the DA or DH prescribed in paragraph (b), unless—
(1) the aircraft is continuously in a position from which a descent to a landing on the intended runway can be made at a normal rate of descent using normal manoeuvres that will allow touchdown to occur within the touchdown zone of the runway of intended landing; and
(2) the flight visibility is not less than the visibility prescribed under Part 97 for the instrument approach procedure being used; and
(3) except for a Category II or Category III precision approach
procedure prescribed under Part 97 for that aerodrome that
includes any necessary visual reference requirements, at least
one of the following visual references for the intended runway is
distinctly visible and identifiable to the pilot—
(i) the approach lighting system; or
(ii) the threshold markings; or
(iii) the threshold lights; or
(iv) the runway-end identification lights; or
(v) the visual approach slope indicator; or
(vi) the touch down zone or touchdown zone markings; or
(vii) the touchdown zone lights; or
(viii) the runway or runway markings; or
(ix) the runway lights.
....
(e) Missed approach procedures. Each pilot-in-command shall
immediately execute the missed approach procedure prescribed under Part 97 if—
(1) the requirements of paragraph (c) are not met at either of the
following times:
(i) when the aircraft is being operated below MDA; or
(ii) upon arrival at the missed approach point, including a DA
or DH where a DA or DH is specified and its use is required, and any time after that until touchdown; or
(2) an identifiable part of the aerodrome is not distinctly visible to
the pilot during a circling manoeuvre at or above MDA, unless
the inability to see an identifiable part of the aerodrome results
only from normal manoeuvring of the aircraft during approach.
If you want the rule for "visual approaches" let me know..
these are two very different approach methods and require different condidtions to be met during both day and night.
QUOTE
Part 91.413(c)
Operation below DA, DH, or MDA. Where a DA, DH, or MDA is
applicable, no pilot-in-command shall operate an aircraft at any aerodrome below the MDA, or continue an instrument approach procedure below the DA or DH prescribed in paragraph (b), unless—
(1) the aircraft is continuously in a position from which a descent to a landing on the intended runway can be made at a normal rate of descent using normal manoeuvres that will allow touchdown to occur within the touchdown zone of the runway of intended landing; and
(2) the flight visibility is not less than the visibility prescribed under Part 97 for the instrument approach procedure being used; and
(3) except for a Category II or Category III precision approach
procedure prescribed under Part 97 for that aerodrome that
includes any necessary visual reference requirements, at least
one of the following visual references for the intended runway is
distinctly visible and identifiable to the pilot—
(i) the approach lighting system; or
(ii) the threshold markings; or
(iii) the threshold lights; or
(iv) the runway-end identification lights; or
(v) the visual approach slope indicator; or
(vi) the touch down zone or touchdown zone markings; or
(vii) the touchdown zone lights; or
(viii) the runway or runway markings; or
(ix) the runway lights.
....
(e) Missed approach procedures. Each pilot-in-command shall
immediately execute the missed approach procedure prescribed under Part 97 if—
(1) the requirements of paragraph (c) are not met at either of the
following times:
(i) when the aircraft is being operated below MDA; or
(ii) upon arrival at the missed approach point, including a DA
or DH where a DA or DH is specified and its use is required, and any time after that until touchdown; or
(2) an identifiable part of the aerodrome is not distinctly visible to
the pilot during a circling manoeuvre at or above MDA, unless
the inability to see an identifiable part of the aerodrome results
only from normal manoeuvring of the aircraft during approach.
If you want the rule for "visual approaches" let me know..
Last edited by 123567; 9th Nov 2005 at 05:01.
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There might be some confusion here between a "visual approach" and descending below MDA on an "instrument approach".
And Part 97 or is that Part 19!