Multiple approaches, approaches in icing, and a few tricks.
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Multiple approaches, approaches in icing, and a few tricks.
Reading the NWA thread brought up a few good points about multiple approaches, icing and dive and drive non precision approaches.
Some companies I've worked for had a 2 approach rule. I also adopted that in the other companies that didn't have it.
Multiple approaches in icing are a great way to stall during the landing.
To make non precision approaches easier (safer) some companies (like Jazz) use an SCDA (standard constant descent angle) where you hit the FAF, descend at a pre calculated descent rate using provided graphs (ground speed, altitude across the FAF, and distance to threshold gives you a descent rate) and treat MDA as a DH. The idea is you have a constant descant angle/rate from the FAF to the runway. No messing with speed/power - no more dive and drives. You’re on speed and power, gear and flap set and once you reach MDA you either continue to a landing or go around. No configuration changes, works great.
Another technique is using a VDP - visual descent point. For a 3 degree path to the runway from MDA use the 1 in 3 rule (1 mile back, 300 feet AGL). Example, if your MDA is 400’ at 1.3 miles back from the threshold you should see runway – IE PNF say “VDP runway 12 o’clock, decide” or “VDP no contact, decide” if you don’t see runway you can continue to the MAP and go missed, or commence the missed at that point. Either way you’re going around. The difference between this type and a SCDA is you need to descend fast to MDA get stable prior to VDP. This requires more configuration changes, and some approaches have a very short span from the FAF to threshold making this a challenging maneuver. I prefer the SCDA.
Another trick I used to use during a black whole approaches or when the weather was crap and I was on the visual portion of the approach was REF and sink rate calls – IE “Ref plus 5, sink of 700”. I found I didn’t need to cross reference the instruments near as much as I was concentrating outside, made my job easier as the PF.
IMHO, I think TC should mandate some of these (SCDA) as law as it reduces a lot of the workload thereby making them safer.
Some companies I've worked for had a 2 approach rule. I also adopted that in the other companies that didn't have it.
Multiple approaches in icing are a great way to stall during the landing.
To make non precision approaches easier (safer) some companies (like Jazz) use an SCDA (standard constant descent angle) where you hit the FAF, descend at a pre calculated descent rate using provided graphs (ground speed, altitude across the FAF, and distance to threshold gives you a descent rate) and treat MDA as a DH. The idea is you have a constant descant angle/rate from the FAF to the runway. No messing with speed/power - no more dive and drives. You’re on speed and power, gear and flap set and once you reach MDA you either continue to a landing or go around. No configuration changes, works great.
Another technique is using a VDP - visual descent point. For a 3 degree path to the runway from MDA use the 1 in 3 rule (1 mile back, 300 feet AGL). Example, if your MDA is 400’ at 1.3 miles back from the threshold you should see runway – IE PNF say “VDP runway 12 o’clock, decide” or “VDP no contact, decide” if you don’t see runway you can continue to the MAP and go missed, or commence the missed at that point. Either way you’re going around. The difference between this type and a SCDA is you need to descend fast to MDA get stable prior to VDP. This requires more configuration changes, and some approaches have a very short span from the FAF to threshold making this a challenging maneuver. I prefer the SCDA.
Another trick I used to use during a black whole approaches or when the weather was crap and I was on the visual portion of the approach was REF and sink rate calls – IE “Ref plus 5, sink of 700”. I found I didn’t need to cross reference the instruments near as much as I was concentrating outside, made my job easier as the PF.
IMHO, I think TC should mandate some of these (SCDA) as law as it reduces a lot of the workload thereby making them safer.
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Re: Multiple approaches, approaches in icing, and a few tricks.
Fantastic Points KAG. I aswell have a 2 approach rule for myself. Anymore than that and I am just trying to hard.
Re: Multiple approaches, approaches in icing, and a few tricks.
Is there a way of calculating a table for the SCDA for any aircraft. I have seen the charts for RJ but the aircraft I fly does not have such a chart. I currently use the 1 in 3 rule which generally works ok. Have wanted to use the constant descent approach but wouldn't know how to calculate the rate of descent etc. Anyone have a formula?
Re: Multiple approaches, approaches in icing, and a few tricks.
It largely depends on how the approach is designed, not so much about the aircraft itself. For example, if the FAF is closer to the runway and there is a lot of altitude to loose, you will need more than 3 degrees. On the other end, if the FAF is farther away and there is not much altitude to loose, you'll need LESS than 3 degree.
The rate of descent for a groudspeed/dive angle are published behind the CAPs.
The rate of descent for a groudspeed/dive angle are published behind the CAPs.
Be careful NOT to treat the MDA like a DH as the DH takes into account the time for the power to bite, raise the nose and the subsequent dip below DH (roughly 50' usually). You should add 50' to you MDA if you will consider this as a DH.KAG wrote: To make non precision approaches easier (safer) some companies (like Jazz) use an SCDA (standard constant descent angle) where you hit the FAF, descend at a pre calculated descent rate using provided graphs (ground speed, altitude across the FAF, and distance to threshold gives you a descent rate) and treat MDA as a DH.
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Re: Multiple approaches, approaches in icing, and a few tricks.
KAG, I thought that was a darn good post except for one point
And I agree with everything else yo say including the idea that it reduces workload.
IMHO, I think TC should mandate some of these (SCDA) as law as it reduces a lot of the workload thereby making them safer.
Always running to TC for more regulations will not make unsafe people do safe things. Canadians, more than anyothers I have experienced always want mother government to look after them. And pilots is particular want someone to make their decisions for them. Seems we cant take responsibility for our own actins without it being regulated.
And I agree with everything else yo say including the idea that it reduces workload.
Accident speculation:
Those that post don’t know. Those that know don’t post
Those that post don’t know. Those that know don’t post
Re: Multiple approaches, approaches in icing, and a few tricks.
They do to get lower vis in the approach ban. http://www.tc.gc.ca/CivilAviation/Regse ... htm#703_41 -KAG wrote: IMHO, I think TC should mandate some of these (SCDA) as law as it reduces a lot of the workload thereby making them safer.
http://www.tc.gc.ca/CivilAviation/Regse ... htm#704_37 - http://www.tc.gc.ca/CivilAviation/Regse ... htm#705_48
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Re: Multiple approaches, approaches in icing, and a few tricks.
One thing to clarify first; A 'DH' is a decision height (ie: CAT-II or CAT-III, 100 feet or 50 feet absolute altitude, which is determined off the radar altimeter). A 'DA' is a decision altitude (ie: CAT-I, off the pressure altimeter).AuxBatOn wrote:Be careful NOT to treat the MDA like a DH as the DH takes into account the time for the power to bite, raise the nose and the subsequent dip below DH (roughly 50' usually). You should add 50' to you MDA if you will consider this as a DH.
Air Canada Jazz CRJ AOM Volume 2:
(in regards to SCDA approaches)
"The MDA is treated as a Decision Altitude (DA). If adequate visual reference exists at DA, no change in vertical speed should be required. If insufficient visual reference exists at DA, a go-around is immediately commenced. MDA is treated like a DA, therefore, during a go-around the aircraft will descend slightly below the MDA. Descent below this altitude must be minimized as much as possible."
Re: Multiple approaches, approaches in icing, and a few tricks.
Maybe according to AC, but not according to TC :sdjfkosdjf wrote:
One thing to clarify first; A 'DH' is a decision height (ie: CAT-II or CAT-III, 100 feet or 50 feet absolute altitude, which is determined off the radar altimeter). A 'DA' is a decision altitude (ie: CAT-I, off the pressure altimeter).
I know calling the CAT I minima a DH doesn't make sense, but this is still the way we call it, until TC ammends its regs. There is no mention of DA in the CARs (that I know of).CARs 602.128 wrote: 602.128
....(1) No pilot-in-command of an IFR aircraft shall conduct an instrument approach procedure except in accordance with the minima specified in the Canada Air Pilot or the route and approach inventory.
....(2) No pilot-in-command of an IFR aircraft shall, unless the required visual reference necessary to continue the approach to land has been established,
........(a) in the case of a CAT I or CAT II precision approach, continue the final approach descent below the decision height; or
(amended 2006/12/01; previous version)
........(b) in the case of a non-precision approach, descend below the minimum descent altitude.
....(3) Where the pilot-in-command of an IFR aircraft conducting an instrument approach does not establish the required visual reference referred to in subsection (2), the pilot-in-command shall initiate a missed approach procedure
........(a) in the case of a CAT I or CAT II precision approach, at decision height; and
(amended 2006/12/01; previous version)
........(b) in the case of a non-precision approach, at the missed approach point.
....(4) Notwithstanding anything in this Division, no pilot-in-command of an IFR aircraft shall conduct a precision approach to CAT II or CAT III minima unless
........(a) the flight crew has received the training specified in the Manual of All Weather Operations (Categories II and III); and
........(b) the aircraft is operated in accordance with the procedures, the equipment requirements and the limitations specified in the manual referred to in paragraph (a).
Again, this is wrong. You can't legally do it. To me, it's the same as letting down below MDA to get visual with the runway environment. Re-reading 602.128 (2)(b), we can see : in the case of a non-precision approach, descend below the minimum descent altitude.sdjfkosdjf wrote: (in regards to SCDA approaches)
"The MDA is treated as a Decision Altitude (DA). If adequate visual reference exists at DA, no change in vertical speed should be required. If insufficient visual reference exists at DA, a go-around is immediately commenced. MDA is treated like a DA, therefore, during a go-around the aircraft will descend slightly below the MDA. Descent below this altitude must be minimized as much as possible."
In the subsequent paragraphs, there is no provision for using the MDA like a DA.
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Re: Multiple approaches, approaches in icing, and a few tricks.
I agree with the first part of your rebuttal but not the second. For those operators who have the ops spec to conduct SCDA approaches part of it allows for descent below MDA to allow for the sink rate as power is applied for go around, just like conducting an ILS to mins with a go around at DH.AuxBatOn wrote:Maybe according to AC, but not according to TC :sdjfkosdjf wrote:
One thing to clarify first; A 'DH' is a decision height (ie: CAT-II or CAT-III, 100 feet or 50 feet absolute altitude, which is determined off the radar altimeter). A 'DA' is a decision altitude (ie: CAT-I, off the pressure altimeter).
I know calling the CAT I minima a DH doesn't make sense, but this is still the way we call it, until TC ammends its regs. There is no mention of DA in the CARs (that I know of).CARs 602.128 wrote: 602.128
....(1) No pilot-in-command of an IFR aircraft shall conduct an instrument approach procedure except in accordance with the minima specified in the Canada Air Pilot or the route and approach inventory.
....(2) No pilot-in-command of an IFR aircraft shall, unless the required visual reference necessary to continue the approach to land has been established,
........(a) in the case of a CAT I or CAT II precision approach, continue the final approach descent below the decision height; or
(amended 2006/12/01; previous version)
........(b) in the case of a non-precision approach, descend below the minimum descent altitude.
....(3) Where the pilot-in-command of an IFR aircraft conducting an instrument approach does not establish the required visual reference referred to in subsection (2), the pilot-in-command shall initiate a missed approach procedure
........(a) in the case of a CAT I or CAT II precision approach, at decision height; and
(amended 2006/12/01; previous version)
........(b) in the case of a non-precision approach, at the missed approach point.
....(4) Notwithstanding anything in this Division, no pilot-in-command of an IFR aircraft shall conduct a precision approach to CAT II or CAT III minima unless
........(a) the flight crew has received the training specified in the Manual of All Weather Operations (Categories II and III); and
........(b) the aircraft is operated in accordance with the procedures, the equipment requirements and the limitations specified in the manual referred to in paragraph (a).
Again, this is wrong. You can't legally do it. To me, it's the same as letting down below MDA to get visual with the runway environment. Re-reading 602.128 (2)(b), we can see : in the case of a non-precision approach, descend below the minimum descent altitude.sdjfkosdjf wrote: (in regards to SCDA approaches)
"The MDA is treated as a Decision Altitude (DA). If adequate visual reference exists at DA, no change in vertical speed should be required. If insufficient visual reference exists at DA, a go-around is immediately commenced. MDA is treated like a DA, therefore, during a go-around the aircraft will descend slightly below the MDA. Descent below this altitude must be minimized as much as possible."
In the subsequent paragraphs, there is no provision for using the MDA like a DA.
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Re: Multiple approaches, approaches in icing, and a few tricks.
Thanks Cap'n P8, all I'm refering to is the CARs. I see that in 723, they talk about SCDA, however there is no description of how to conduct it. I do know there is a circular out there describing it, but I just can't find it.Cap'n P8 wrote: I agree with the first part of your rebuttal but not the second. For those operators who have the ops spec to conduct SCDA approaches part of it allows for descent below MDA to allow for the sink rate as power is applied for go around, just like conducting an ILS to mins with a go around at DH.
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Re: Multiple approaches, approaches in icing, and a few tricks.
From CBAAC 0238 2006.09.08 SCDA NPA
The aim of an SCDA NPA procedure is to minimize the vertical manoeuvring required while flying most NPAs from the final approach segment through to touch down. The goal is to achieve a final approach vertical path that approximates that of a normal glide path. An SCDA NPA procedure allows certain NPAs to be flown using the MDA as a DA(H).
Using the SCDA NPA procedure, the aircraft is not flown at minimum altitudes for extended periods of time. If the route flown intercepts the intermediate approach segment, then a higher enroute altitude can be maintained until an approximate 3-degree vertical descent path is intercepted and a continuous descent to MDA can be made. If a course reversal using a PT is required, the aircraft can be flown at or above the minimum PT altitude until the 3-degree vertical descent path is intercepted and a continuous descent to MDA can be made. No later than crossing the FAF, the aircraft descends stabilized on the planned constant descent angle configured for landing, with stable airspeed, power setting, and attitude. The aircraft is descended towards MDA until the runway environment is sighted and the descent continued to landing, or until it reaches MDA (treated like a DA(H)) where a missed approach is commenced.
Figure 1 (Annex A) compares the vertical descent profiles of a NPA flown using a SCDA NPA technique to the traditional step-down technique. A typical NPA provides 1,000 feet of ROC in the initial segment and the procedure turn, 500 feet of ROC in the intermediate segment, and at least 250 feet of ROC in the final segment.
The SCDA NPA procedure is normally applicable to NPAs that meet the following three criteria:
The approach is flown to straight-in minima. (SCDA is not normally applicable to circling approaches where the aircraft has to level at MDA and a circling procedure flown before a descent to landing can be made.)
The approach design should permit a final approach segment descent angle of 2.9 to 3.5 degrees. (NPA approach design criteria permit a final approach segment with a descent gradient up to 3.77 degrees. Therefore, there are a few NPAs with steep descent gradients that exceed 3.5 degrees, for which the SCDA technique would not be appropriate. New approach design criteria for NPAs with vertical guidance limit the descent angle to 3.5 degrees or less.)
The final approach course shall not be more than 15 degrees from runway centreline. (NPA design criteria permit straight-in minima to be published for IAPs with final approach courses up to 30 degrees from the runway centreline. The SCDA approach procedure is not normally applicable to straight-in approaches with final approach courses that exceed 15 degrees from the runway centreline, in order to reduce the requirement for lateral manoeuvring during the transition from approach to landing.)
An SCDA NPA final approach descent is flown with a planned SCDA of not less than 2.9 degrees and not greater than 3.5 degrees from the FAF to a nominal landing runway threshold crossing height of 50 feet. The angle flown is selected to ensure that minimum FAF crossing altitude and any step-down altitudes between the FAF and the MAP are respected.
The final descent path can be flown using baro-VNAV guidance, FPA guidance, VS based on groundspeed, and/or check altitudes based on distance from touch-down.
A blanket exemption from CAR 602.128(2)(b) allows a momentary descent below MDA only when this occurs during a go-around from a SCDA approach.
705.48(3) No person shall continue an SCDA non precision approach unless
(amended 2006/12/01; previous version)
(a) the air operator is authorized to do so in its air operator certificate;
(b) the aeroplane is equipped with
(i) if the flight crew does not use pilot monitored approach procedures, an autopilot capable of conducting a non precision approach to 400 feet AGL or lower, or
(ii) a HUD capable of conducting a non precision approach to 400 feet AGL or lower;
(c) the instrument approach procedure is conducted to straight in minima with a final approach course that meets the requirements of section 725.48 of Standard 725 — Airline Operations — Aeroplanes of the Commercial Air Service Standards;
(d) the final approach segment is conducted using a stabilized descent with a planned constant descent angle specified in section 725.48 of Standard 725 — Airline Operations — Aeroplanes of the Commercial Air Service Standards; and
(e) a visibility report indicates that
(i) the visibility is equal to or greater than that set out in subsection (1),
(ii) the RVR is varying between distances less than and greater than the minimum RVR set out in subsection (1), or
(iii) the visibility is less than the minimum visibility set out in subsection (1) and, at the time the visibility report is received, the aeroplane has passed the FAF inbound or, where there is no FAF, the point where the final approach course is intercepted.
CASS 725.124(54) Stabilized Constant-Descent-Angle (SCDA) Non-Precision Approach Training
(amended 2006/12/01; no previous version)
The air operator shall ensure that the pilot-in-command and the second-in-command, in order to be able to conduct a stabilized constant-descent-angle (SCDA) non-precision approach, receive ground and simulator or flight training that addresses the following subjects within their initial and recurrent training programs:
(a) factors that affect altitude loss during the initiation of a missed approach;
(b) the relationship between the published missed approach point (MAP) and the position where a missed approach is commenced following a stabilized final approach descent to minimum descent altitude (MDA);
Information Note: The missed approach climb from a stabilized final approach descent will normally occur some distance before reaching the published MAP.
(c) the requirement to initiate a missed approach if the required visual reference necessary to continue to land has not been established, at the latest on reaching the earlier of:
(i) the minimum descent altitude, and
(ii) the MAP;
(d) the requirement to commence the horizontal (lateral) navigation portion of the published missed approach procedure at the MAP;
Information Note: It may be essential for obstacle clearance to delay any turns stated in the published missed approach procedure until the aircraft crosses the MAP.
(e) the requirement to ensure that any altitudes at step-down fixes between the final approach fix (FAF) and the MAP are respected;
(f) the operation of any aircraft computer-generated approach slope systems or other methods of computing stable approach paths to the target touchdown point;
Information Note: The effects of horizontal position error and temperature on the vertical path, whether it is derived from an inertial, barometric vertical navigation (Baro VNAV), or altimeter reference, shall be addressed.
(g) the requirement to verify any altitude and waypoint information from a navigation database against an independent source;
(h) crew coordination upon reaching MDA and during the execution of a missed approach; and
(i) utilization of temperature corrections to MDA and other published altitudes and remote altimeter correction factors, when required.
The aim of an SCDA NPA procedure is to minimize the vertical manoeuvring required while flying most NPAs from the final approach segment through to touch down. The goal is to achieve a final approach vertical path that approximates that of a normal glide path. An SCDA NPA procedure allows certain NPAs to be flown using the MDA as a DA(H).
Using the SCDA NPA procedure, the aircraft is not flown at minimum altitudes for extended periods of time. If the route flown intercepts the intermediate approach segment, then a higher enroute altitude can be maintained until an approximate 3-degree vertical descent path is intercepted and a continuous descent to MDA can be made. If a course reversal using a PT is required, the aircraft can be flown at or above the minimum PT altitude until the 3-degree vertical descent path is intercepted and a continuous descent to MDA can be made. No later than crossing the FAF, the aircraft descends stabilized on the planned constant descent angle configured for landing, with stable airspeed, power setting, and attitude. The aircraft is descended towards MDA until the runway environment is sighted and the descent continued to landing, or until it reaches MDA (treated like a DA(H)) where a missed approach is commenced.
Figure 1 (Annex A) compares the vertical descent profiles of a NPA flown using a SCDA NPA technique to the traditional step-down technique. A typical NPA provides 1,000 feet of ROC in the initial segment and the procedure turn, 500 feet of ROC in the intermediate segment, and at least 250 feet of ROC in the final segment.
The SCDA NPA procedure is normally applicable to NPAs that meet the following three criteria:
The approach is flown to straight-in minima. (SCDA is not normally applicable to circling approaches where the aircraft has to level at MDA and a circling procedure flown before a descent to landing can be made.)
The approach design should permit a final approach segment descent angle of 2.9 to 3.5 degrees. (NPA approach design criteria permit a final approach segment with a descent gradient up to 3.77 degrees. Therefore, there are a few NPAs with steep descent gradients that exceed 3.5 degrees, for which the SCDA technique would not be appropriate. New approach design criteria for NPAs with vertical guidance limit the descent angle to 3.5 degrees or less.)
The final approach course shall not be more than 15 degrees from runway centreline. (NPA design criteria permit straight-in minima to be published for IAPs with final approach courses up to 30 degrees from the runway centreline. The SCDA approach procedure is not normally applicable to straight-in approaches with final approach courses that exceed 15 degrees from the runway centreline, in order to reduce the requirement for lateral manoeuvring during the transition from approach to landing.)
An SCDA NPA final approach descent is flown with a planned SCDA of not less than 2.9 degrees and not greater than 3.5 degrees from the FAF to a nominal landing runway threshold crossing height of 50 feet. The angle flown is selected to ensure that minimum FAF crossing altitude and any step-down altitudes between the FAF and the MAP are respected.
The final descent path can be flown using baro-VNAV guidance, FPA guidance, VS based on groundspeed, and/or check altitudes based on distance from touch-down.
A blanket exemption from CAR 602.128(2)(b) allows a momentary descent below MDA only when this occurs during a go-around from a SCDA approach.
705.48(3) No person shall continue an SCDA non precision approach unless
(amended 2006/12/01; previous version)
(a) the air operator is authorized to do so in its air operator certificate;
(b) the aeroplane is equipped with
(i) if the flight crew does not use pilot monitored approach procedures, an autopilot capable of conducting a non precision approach to 400 feet AGL or lower, or
(ii) a HUD capable of conducting a non precision approach to 400 feet AGL or lower;
(c) the instrument approach procedure is conducted to straight in minima with a final approach course that meets the requirements of section 725.48 of Standard 725 — Airline Operations — Aeroplanes of the Commercial Air Service Standards;
(d) the final approach segment is conducted using a stabilized descent with a planned constant descent angle specified in section 725.48 of Standard 725 — Airline Operations — Aeroplanes of the Commercial Air Service Standards; and
(e) a visibility report indicates that
(i) the visibility is equal to or greater than that set out in subsection (1),
(ii) the RVR is varying between distances less than and greater than the minimum RVR set out in subsection (1), or
(iii) the visibility is less than the minimum visibility set out in subsection (1) and, at the time the visibility report is received, the aeroplane has passed the FAF inbound or, where there is no FAF, the point where the final approach course is intercepted.
CASS 725.124(54) Stabilized Constant-Descent-Angle (SCDA) Non-Precision Approach Training
(amended 2006/12/01; no previous version)
The air operator shall ensure that the pilot-in-command and the second-in-command, in order to be able to conduct a stabilized constant-descent-angle (SCDA) non-precision approach, receive ground and simulator or flight training that addresses the following subjects within their initial and recurrent training programs:
(a) factors that affect altitude loss during the initiation of a missed approach;
(b) the relationship between the published missed approach point (MAP) and the position where a missed approach is commenced following a stabilized final approach descent to minimum descent altitude (MDA);
Information Note: The missed approach climb from a stabilized final approach descent will normally occur some distance before reaching the published MAP.
(c) the requirement to initiate a missed approach if the required visual reference necessary to continue to land has not been established, at the latest on reaching the earlier of:
(i) the minimum descent altitude, and
(ii) the MAP;
(d) the requirement to commence the horizontal (lateral) navigation portion of the published missed approach procedure at the MAP;
Information Note: It may be essential for obstacle clearance to delay any turns stated in the published missed approach procedure until the aircraft crosses the MAP.
(e) the requirement to ensure that any altitudes at step-down fixes between the final approach fix (FAF) and the MAP are respected;
(f) the operation of any aircraft computer-generated approach slope systems or other methods of computing stable approach paths to the target touchdown point;
Information Note: The effects of horizontal position error and temperature on the vertical path, whether it is derived from an inertial, barometric vertical navigation (Baro VNAV), or altimeter reference, shall be addressed.
(g) the requirement to verify any altitude and waypoint information from a navigation database against an independent source;
(h) crew coordination upon reaching MDA and during the execution of a missed approach; and
(i) utilization of temperature corrections to MDA and other published altitudes and remote altimeter correction factors, when required.
Re: Multiple approaches, approaches in icing, and a few tricks.
Thanks!george sugar wrote:From CBAAC 0238 2006.09.08 SCDA NPA
The aim of an SCDA NPA procedure is to minimize the vertical manoeuvring required while flying most NPAs from the final approach segment through to touch down. The goal is to achieve a final approach vertical path that approximates that of a normal glide path. An SCDA NPA procedure allows certain NPAs to be flown using the MDA as a DA(H).
[...]
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Re: Multiple approaches, approaches in icing, and a few tricks.
An informative thread for everyone.
I also want to point out three more things we do at AC Jazz with regards to the SCDA, all are important:
The first is that before crossing the FAF, where you initiate the SCDA descent, you must be fully configured to land, ie: gear down, full flaps, Vref+5 KIAS. This is integral, because as soon as you hit the FAF, you select VS on the autopilot and dial in your preselected VS (usually 800 or 900fpm, depending on the FPA). So if you aren't fully configured, your FPA will be messed up, and you'll have to adjust your VS.
The second thing is that the SCDA FAF crossing altitude must be temperature corrected when zero or below, just like all other approach altitudes.
Also, if we are doing an SCDA single-engine, we add 50' to the DA. If the FPA, is higher than 3.5 degrees, we will add 50'. So it is possible to do an SCDA single-engine with an FPA of 3.6 degrees, but you'd have to add 100' to your DA.
The calls are the same for minimums, with the PNF saying either "Visual, Decide" or "No Contact, Decide." Since you might be executing a go-around before the MAP, you must wait until you pass the MAP before starting any lateral navigation.
I also want to point out three more things we do at AC Jazz with regards to the SCDA, all are important:
The first is that before crossing the FAF, where you initiate the SCDA descent, you must be fully configured to land, ie: gear down, full flaps, Vref+5 KIAS. This is integral, because as soon as you hit the FAF, you select VS on the autopilot and dial in your preselected VS (usually 800 or 900fpm, depending on the FPA). So if you aren't fully configured, your FPA will be messed up, and you'll have to adjust your VS.
The second thing is that the SCDA FAF crossing altitude must be temperature corrected when zero or below, just like all other approach altitudes.
Also, if we are doing an SCDA single-engine, we add 50' to the DA. If the FPA, is higher than 3.5 degrees, we will add 50'. So it is possible to do an SCDA single-engine with an FPA of 3.6 degrees, but you'd have to add 100' to your DA.
The calls are the same for minimums, with the PNF saying either "Visual, Decide" or "No Contact, Decide." Since you might be executing a go-around before the MAP, you must wait until you pass the MAP before starting any lateral navigation.
Re: Multiple approaches, approaches in icing, and a few tricks.
Can't you set a Descent Angle from the FAF in the FMS?? That would be more accurate than setting a VS that is solely dependent on your GroundSpeed (which is, in turn, dependant on your weight and windspeed)sdjfkosdjf wrote:The first is that before crossing the FAF, where you initiate the SCDA descent, you must be fully configured to land, ie: gear down, full flaps, Vref+5 KIAS. This is integral, because as soon as you hit the FAF, you select VS on the autopilot and dial in your preselected VS (usually 800 or 900fpm, depending on the FPA). So if you aren't fully configured, your FPA will be messed up, and you'll have to adjust your VS.
I was going to add that as well, it could get you in places like the Rockies.sdjfkosdjf wrote:The calls are the same for minimums, with the PNF saying either "Visual, Decide" or "No Contact, Decide." Since you might be executing a go-around before the MAP, you must wait until you pass the MAP before starting any lateral navigation.
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Re: Multiple approaches, approaches in icing, and a few tricks.
Yep, you can program it in the FMS, and bring up the VNAV snowflake, and follow that down... one problem though, only until you reach zero or below. The FMS in all the amazing things it can do, does not temperature correct the VNAV snowflake.AuxBatOn wrote:Can't you set a Descent Angle from the FAF in the FMS?? That would be more accurate than setting a VS that is solely dependent on your GroundSpeed (which is, in turn, dependant on your weight and windspeed)

But really not a biggie. We have our TOL cards set for our landing weight, so all you need to do is take into account the current wind. I'm willing to bet the majority of the time we use 130 or 140 KIAS as Vref for the SCDA.
And ditto on the mountainous terrain thing.
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Re: Multiple approaches, approaches in icing, and a few tricks.
It is important when using an approach from the database that one does not alter altitudes or angles inside the FAF. The coding is in compliance with the approach obstacle criteria provided by the state, and is designed to comply with intermediate step-down altitudes inside the FAF. Any alterations to the FMS can cause the aircraft to violate the obstacle clearance plane inside the FAF or on the subsequent go-around. One can certainly "build" an overlay approach to use VNAV, but raw data must be closely monitored at all times. Stand-alone RNAV and RNP approaches can not be built, however, as there is no other obstacle clearance protection than that provided by the coded approach.
A flight path angle (FPA) is the next best method, when the aircraft has the capability of the pilot selecting it (most don't). V/S is a lesser option, since as was pointed out it is subject to vagaries in wind and aircraft speed, and imprecise aircraft handling.
An additive must be used whenever anything might compromise go-around performance; not only engine-out, but also overweight landing conditions, configuration problems or potentially even airframe icing. The company ops manual should specify when an additive must be used.
A flight path angle (FPA) is the next best method, when the aircraft has the capability of the pilot selecting it (most don't). V/S is a lesser option, since as was pointed out it is subject to vagaries in wind and aircraft speed, and imprecise aircraft handling.
An additive must be used whenever anything might compromise go-around performance; not only engine-out, but also overweight landing conditions, configuration problems or potentially even airframe icing. The company ops manual should specify when an additive must be used.
Last edited by george sugar on Sun Nov 30, 2008 7:16 pm, edited 1 time in total.
Re: Multiple approaches, approaches in icing, and a few tricks.
I thought it did. We always fly the VNAV below zero.Yep, you can program it in the FMS, and bring up the VNAV snowflake, and follow that down... one problem though, only until you reach zero or below. The FMS in all the amazing things it can do, does not temperature correct the VNAV snowflake.
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Re: Multiple approaches, approaches in icing, and a few tricks.
Most FMSs do not automatically correct for cold temperatures. But generally VNAV can be used for guidance, as long as the missed approach is commenced at the temperature corrected minimum descent altitude, and crossing altitudes not within the final approach segment (i.e. missed approach and procedure turn altitudes) are also adjusted. The user guide for your particular FMS should be consulted, as different manufacturers have varying ways of compensating for temperature correction.
Re: Multiple approaches, approaches in icing, and a few tricks.
Interesting...Cap'n P8 wrote:I agree with the first part of your rebuttal but not the second. For those operators who have the ops spec to conduct SCDA approaches part of it allows for descent below MDA to allow for the sink rate as power is applied for go around, just like conducting an ILS to mins with a go around at DH.
We do SCDA non-precision approaches but we use a DDA(Derived Decision Altitude) in which we add 50 feet to the published MDA to ensure we do not sink below the published MDA in the event of a go-around.
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Re: Multiple approaches, approaches in icing, and a few tricks.
rd1331 wrote:Is there a way of calculating a table for the SCDA for any aircraft. I have seen the charts for RJ but the aircraft I fly does not have such a chart. I currently use the 1 in 3 rule which generally works ok. Have wanted to use the constant descent approach but wouldn't know how to calculate the rate of descent etc. Anyone have a formula?
The chart shouldn't be a/c specific, just speed, descent rate, distance, height AGL.
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Re: Multiple approaches, approaches in icing, and a few tricks.
WHy would you plan less than 3 degrees, that is what we are all trained for? Why would you not just calculate what altitude (AGL) you have to cross the FAF at to get 3 degrees, ensure that # is above the mimimun alt. and use the higher altitude?? I personally know that on approach you can't get into trouble if your a little high (I've spent a large portion of my career using speed levers, flight spoilers, landing gear, etc to correct my inattention, suduko is hard you knowAuxBatOn wrote:It largely depends on how the approach is designed, not so much about the aircraft itself. For example, if the FAF is closer to the runway and there is a lot of altitude to loose, you will need more than 3 degrees. On the other end, if the FAF is farther away and there is not much altitude to loose, you'll need LESS than 3 degree.
The rate of descent for a groudspeed/dive angle are published behind the CAPs.

Just my thoughts
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Re: Multiple approaches, approaches in icing, and a few tricks.
Your suggestion, bobcayeon, is in fact what is being worked towards. New approaches are being charted in accordance with a 3 degree path, rather than the minimum obstruction clearance plane. There are a few older-criteria approaches still out there, e.g. NDB 24 YHZ, that are very shallow. Certainly, charted altitudes are minimum, and if the three-degree slope requires you cross the FAF higher than the charted number, there is nothing wrong with that.
I would qualify your statement about being a bit high not being a potential for trouble, though. The inherent failing of the V/S method for an SCDA approach is that the descent at the FAF is commonly commenced a bit late, and the rate of descent is not sufficiently adjusted for this or for changes in wind conditions closer to the ground, frequently leaving the aircraft high at the VDP/MDA point. There is a tremendous temptation to increase the rate of descent upon visual contact at MDA, with the aircraft being high, and this often results in an unstable approach (as defined with a sink rate greater than 1000 fpm) in the visual segment close to the ground. This can result in ground contact prior to the runway. Alternately an over-run can occur when a subsequent over-correction to the high sink rate is applied, if the runway length is limiting and landing occurs beyond the touchdown zone.
As it states in the CBAAC, one should not have to change anything upon reaching MDA if the SCDA has been flown correctly. If drastic alterations to the flight path are required, then something is obviously not right, and a missed approach is likely the safest thing.
I would qualify your statement about being a bit high not being a potential for trouble, though. The inherent failing of the V/S method for an SCDA approach is that the descent at the FAF is commonly commenced a bit late, and the rate of descent is not sufficiently adjusted for this or for changes in wind conditions closer to the ground, frequently leaving the aircraft high at the VDP/MDA point. There is a tremendous temptation to increase the rate of descent upon visual contact at MDA, with the aircraft being high, and this often results in an unstable approach (as defined with a sink rate greater than 1000 fpm) in the visual segment close to the ground. This can result in ground contact prior to the runway. Alternately an over-run can occur when a subsequent over-correction to the high sink rate is applied, if the runway length is limiting and landing occurs beyond the touchdown zone.
As it states in the CBAAC, one should not have to change anything upon reaching MDA if the SCDA has been flown correctly. If drastic alterations to the flight path are required, then something is obviously not right, and a missed approach is likely the safest thing.
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Re: Multiple approaches, approaches in icing, and a few tricks.
This is the beauty of an SCDA approach. In your example above, say that the FAF crossing altitude was lower than what would permit a 3.0 FPA, you would artificially raise the FAF crossing altitude to make it a 3.0 degree FPA.AuxBatOn wrote:It largely depends on how the approach is designed, not so much about the aircraft itself. For example, if the FAF is closer to the runway and there is a lot of altitude to loose, you will need more than 3 degrees. On the other end, if the FAF is farther away and there is not much altitude to loose, you'll need LESS than 3 degree.
In essence, you would cross the FAF at a higher altitude (that what the charts publish), and start your 3.0 degree FPA from there, all the way down to the DA (MDA). This is safer, instead of starting a shallow FPA, with more power on.
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Re: Multiple approaches, approaches in icing, and a few tricks.
I would have to say that if all calculations are made correctly, and applied correctly, often you will break out of cloud on the PAPI (if available). Sometimes, you will maybe break out slightly above, or below the PAPI. In essence, you are trying to make a non-precision approach into as-close-to a precision approach as possible, but never quite.george sugar wrote:I would qualify your statement about being a bit high not being a potential for trouble, though. The inherent failing of the V/S method for an SCDA approach is that the descent at the FAF is commonly commenced a bit late, and the rate of descent is not sufficiently adjusted for this or for changes in wind conditions closer to the ground, frequently leaving the aircraft high at the VDP/MDA point. There is a tremendous temptation to increase the rate of descent upon visual contact at MDA, with the aircraft being high, and this often results in an unstable approach (as defined with a sink rate greater than 1000 fpm) in the visual segment close to the ground. This can result in ground contact prior to the runway. Alternately an over-run can occur when a subsequent over-correction to the high sink rate is applied, if the runway length is limiting and landing occurs beyond the touchdown zone.

Re: Multiple approaches, approaches in icing, and a few tricks.
Just to clarify one important point: unless you are working for a company with ops-specs you are NOT entitled to treat an MDA as a DH. Not many companies have this.
Also, you may find that the stabilized non-precision approach works great if you have adequate vis, but if you pop out of cloud at mins. on an ersatz glide slope, you will be considerably closer to the runway than with a dive-and-drive and you will have to decide to land 'immediately' or you will be too high/long to land. In any case, a non-precision has much higher mins and along with the prohibition from decending below MDA you will have to add the 50' or so to MDA to avoid descending below it, making it even more difficult. The Europeans are all going to stabilized now but sometimes what you gain in a stabilized approach you lose with the attendant dive for the runway.
Also, you may find that the stabilized non-precision approach works great if you have adequate vis, but if you pop out of cloud at mins. on an ersatz glide slope, you will be considerably closer to the runway than with a dive-and-drive and you will have to decide to land 'immediately' or you will be too high/long to land. In any case, a non-precision has much higher mins and along with the prohibition from decending below MDA you will have to add the 50' or so to MDA to avoid descending below it, making it even more difficult. The Europeans are all going to stabilized now but sometimes what you gain in a stabilized approach you lose with the attendant dive for the runway.
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