Non precision MDA/DA
Chill out Bleed. We were doing this 20 years ago in jets and it works a treat. If you do get Visual, you fly the aircraft into the VASI and continue on to land. If you don't get Visual, you level off at the MDA then execute the MA at the MAP point. It really is not a big issue. Try a non-database approach without a DME - that's exactly what you would do.
We don't fly 200ft low on a precision approach because a precision approach has a DA. When and if our NPAs have a "DA" as low as the current MDAs, then we will fly down the 3° slope.
We don't fly 200ft low on a precision approach because a precision approach has a DA. When and if our NPAs have a "DA" as low as the current MDAs, then we will fly down the 3° slope.
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The level off thing, or dive and drive, however you wanna call it, is not allowed anymore for AOC-holders under JAR-rules. You have to fly a continues descent final approach to MDA or nowadays DA and execute a go-around if not visual by then.
By the way, Boeings 737 FMC-update 10.8 actually tried that, it flew 200ft low under certain circumstances on NPAs and they had to re-call that update ASAP as that behaviour (and some other snags) were deemed dangerously unsafe.
By the way, Boeings 737 FMC-update 10.8 actually tried that, it flew 200ft low under certain circumstances on NPAs and they had to re-call that update ASAP as that behaviour (and some other snags) were deemed dangerously unsafe.
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DA is the product of GPS. In the old days, we had MDA - tho shall not descend below which was for nonprecision approaches and we had DH which was for precision/ILS approaches which meant we made a decision at that altitude and started the transition to missed approach or continue to a landing. It was understood that some additonal altitude would be lost in the transition to a climb. Approaches were built with this in mind.
Now move to the 90s and later. The upstart GPS approaches muddle things a bit. GPS is considered a nonprecision approach although a very precise one. For that reason, those approaches that are surveyed and meet certain criteria have a designated "Decision Altitude". This is the GPS/non precision approach stopping point to treat with similar definition as Decision Height. Be careful. Not all GPS approaches have "DA"s some will have "MDA"s. DA minimums are not dive and drive minimums, they are for stabilized VPATH approaches.
Mike
Now move to the 90s and later. The upstart GPS approaches muddle things a bit. GPS is considered a nonprecision approach although a very precise one. For that reason, those approaches that are surveyed and meet certain criteria have a designated "Decision Altitude". This is the GPS/non precision approach stopping point to treat with similar definition as Decision Height. Be careful. Not all GPS approaches have "DA"s some will have "MDA"s. DA minimums are not dive and drive minimums, they are for stabilized VPATH approaches.
Mike
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INSTEAD of being "a bit low" on the profile for a CDFA during a NPA with actual limited visibility, it makes better sense to do the opposite -- be "a bit high".
Reason 1: Being so, you're bound to reach your MDA at a closer distance to the runway -- and therefore have a better chance of eyeing the runway --than being exactly on the profile. Sometimes less than a quarter of a mile more is all you need to be visual.
Of course, "a bit high" was in quotation marks to emphasize it being a subjective thing, and that you get above the profile just enough that the required sink rate after becoming visual from your usual 700FPM becomes only around 900FPM.
Reason 2: It plainly gives you a better perspective searching for the runway.
Cheers
Reason 1: Being so, you're bound to reach your MDA at a closer distance to the runway -- and therefore have a better chance of eyeing the runway --than being exactly on the profile. Sometimes less than a quarter of a mile more is all you need to be visual.
Of course, "a bit high" was in quotation marks to emphasize it being a subjective thing, and that you get above the profile just enough that the required sink rate after becoming visual from your usual 700FPM becomes only around 900FPM.
Reason 2: It plainly gives you a better perspective searching for the runway.
Cheers
Per Ardua ad Astraeus
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Being so, you're bound to reach your MDA at a closer distance to the runway
Far better to fly the damn thing as planned?
INSTEAD of being "a bit low" on the profile for a CDFA during a NPA with actual limited visibility, it makes better sense to do the opposite -- be "a bit high".
Only half a speed-brake
That'll be European Council Regulation 859/2008 a.k.a. EU-OPS, OPS 1.430 d(2).
FD (the un-real)
All non-precision approaches shall be flown using the continuous descent final approaches (CDFA) technique unless
otherwise approved by the Authority for a particular approach to a particular runway.
otherwise approved by the Authority for a particular approach to a particular runway.
Last edited by FlightDetent; 4th Mar 2010 at 14:30.
Can't see any level-off rules/prohibition there...
You do your CDA, then level at the MDA IAW the procedure, then at the MAP you do your MA. What's the big deal? You (or your company) may choose (require) to do an immediate MA when approaching the MDA if not Visual but is it a requirement?
You do your CDA, then level at the MDA IAW the procedure, then at the MAP you do your MA. What's the big deal? You (or your company) may choose (require) to do an immediate MA when approaching the MDA if not Visual but is it a requirement?
Only half a speed-brake
OPS 1.450 Terminology
C.B./manuel this of course does not disapprove your point. I'll attempt to dig more later.
“Continuous descent final approach (CDFA)”. A specific technique for flying the final-approach segment of a nonprecision instrument approach procedure as a continuous descent, without level-off, from an altitude/height at or above the Final Approach Fix altitude / height to a point approximately 15 m (50 feet) above the landing runway threshold or the point where the flare manoeuvre should begin for the type of aeroplane flown.
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Capn Bloggs, there's 2 different approaches using CFDA technique as well:
Approach with a designated vertical profile using the CDFA technique:
a. The optimum angle for the approach slope is 3 degrees, and the gradient should preferably not exceed 6.5 percent which equates to a slope of 3.77 degrees, (400 ft/NM) for procedures intended for conventional aeroplane types/classes and/or operations. In any case, conventional approach slopes should be limited to 4.5 degrees for Category A and B aeroplanes and 3.77 degrees for Category C and D aeroplanes, which are the upper limits for applying the CDFA technique. A 4.5 degree approach slope is the upper limit for certification of conventional aeroplanes.
b. The approach is to be flown utilising operational flight techniques and onboard navigation system(s) and navigation aids to ensure it can be flown on the desired vertical path and track in a stabilised manner, without significant vertical path changes during the final-segment descent to the runway. APV is included.
c. The approach is flown to a DA(H). d. No MAPt is published for these procedures.
Approach with a nominal vertical profile using the CDFA technique:
The optimum angle for the approach slope is 3 degrees, and the gradient should preferably not exceed 6.5 percent which equates to a slope of 3.77 degrees, (400 ft/NM) for procedures intended for conventional aeroplane types / class and / or operations. In any case, conventional approaches should be limited to 4.5 degrees for Category A and B aeroplanes and 3.77 degrees for Category C and D aeroplanes, which are the upper limits for applying CDFA technique. A 4.5 degree approach slope is the upper limit for certification of conventional aeroplanes.
The approach should meet at least the following facility requirements and associated conditions. NDB, NDB/DME, VOR, VOR/DME, LLZ, LLZ/DME, VDF, SRA, RNAV(LNAV) with a procedure which fulfils the following criteria:
i. The final approach track off-set ≤ 5degrees except for Category A and B aeroplanes, where the approach-track off-set is ≤ 15 degrees; and
ii. A FAF, or another appropriate fix where descent is initiated is available; and
iii. The distance from the FAF to the THR is less than or equal to 8 NM in the case of timing; or
iv. The distance to the threshold (THR) is available by FMS/RNAV or DME; or
v. The minimum final-segment of the designated constant angle approach path should not be less than 3 NM from the THR unless approved by the Authority.
CDFA may also be applied utilising the following:
i. ii.
RNAV/LNAV with altitude/height cross checks against positions or distances from the THR; or Height crosscheck compared with DME distance values. The approach is flown to a DA(H). The approach is flown as an SAp.
Note: Generally, a MAPt is published for these procedures.
So-called dive and drive is still there and can be used it requires the minimum to be increased accordantly.
Approach with a designated vertical profile using the CDFA technique:
a. The optimum angle for the approach slope is 3 degrees, and the gradient should preferably not exceed 6.5 percent which equates to a slope of 3.77 degrees, (400 ft/NM) for procedures intended for conventional aeroplane types/classes and/or operations. In any case, conventional approach slopes should be limited to 4.5 degrees for Category A and B aeroplanes and 3.77 degrees for Category C and D aeroplanes, which are the upper limits for applying the CDFA technique. A 4.5 degree approach slope is the upper limit for certification of conventional aeroplanes.
b. The approach is to be flown utilising operational flight techniques and onboard navigation system(s) and navigation aids to ensure it can be flown on the desired vertical path and track in a stabilised manner, without significant vertical path changes during the final-segment descent to the runway. APV is included.
c. The approach is flown to a DA(H). d. No MAPt is published for these procedures.
Approach with a nominal vertical profile using the CDFA technique:
The optimum angle for the approach slope is 3 degrees, and the gradient should preferably not exceed 6.5 percent which equates to a slope of 3.77 degrees, (400 ft/NM) for procedures intended for conventional aeroplane types / class and / or operations. In any case, conventional approaches should be limited to 4.5 degrees for Category A and B aeroplanes and 3.77 degrees for Category C and D aeroplanes, which are the upper limits for applying CDFA technique. A 4.5 degree approach slope is the upper limit for certification of conventional aeroplanes.
The approach should meet at least the following facility requirements and associated conditions. NDB, NDB/DME, VOR, VOR/DME, LLZ, LLZ/DME, VDF, SRA, RNAV(LNAV) with a procedure which fulfils the following criteria:
i. The final approach track off-set ≤ 5degrees except for Category A and B aeroplanes, where the approach-track off-set is ≤ 15 degrees; and
ii. A FAF, or another appropriate fix where descent is initiated is available; and
iii. The distance from the FAF to the THR is less than or equal to 8 NM in the case of timing; or
iv. The distance to the threshold (THR) is available by FMS/RNAV or DME; or
v. The minimum final-segment of the designated constant angle approach path should not be less than 3 NM from the THR unless approved by the Authority.
CDFA may also be applied utilising the following:
i. ii.
RNAV/LNAV with altitude/height cross checks against positions or distances from the THR; or Height crosscheck compared with DME distance values. The approach is flown to a DA(H). The approach is flown as an SAp.
Note: Generally, a MAPt is published for these procedures.
So-called dive and drive is still there and can be used it requires the minimum to be increased accordantly.
Only half a speed-brake
9g Both your designated and nominal approaches are flown to DA. The next paragraph after your qoute reads (my bolding):
The way I read it:
- CDFA is constant profile do 50 ft over threshold;
- all NPAs shall be flown as CDFA [EU law since 2008];
- even nominal approaches (no vertical guidance) shall be flown to DA with Miss Approach procedure initiated upon reaching with no allowed level flight towards MAPt [EU law once your operator applies for Appendix (New) to OPS 1.430; every operator must adhere to Appendix (New) by September 2011 the latest]
Sincerely,
FD (the un-real)
The missed approach, after an approach has been flown using the CDFA technique, shall be executed when reaching the decision altitude (height) or the MAPt, whichever occurs first. The lateral part of the missed approach procedure must be flown via the MAPt unless otherwise stated on the approach chart.
- CDFA is constant profile do 50 ft over threshold;
- all NPAs shall be flown as CDFA [EU law since 2008];
- even nominal approaches (no vertical guidance) shall be flown to DA with Miss Approach procedure initiated upon reaching with no allowed level flight towards MAPt [EU law once your operator applies for Appendix (New) to OPS 1.430; every operator must adhere to Appendix (New) by September 2011 the latest]
Sincerely,
FD (the un-real)
Last edited by FlightDetent; 5th Mar 2010 at 14:39. Reason: some coloring
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The flight techniques and operational procedures prescribed above should always be applied; in particular with regard to control of the descent path and the stability of the aeroplane on the approach prior to reaching MDA(H). Level flight at MDA(H) should be avoided as far as practicable. In addition appropriate procedures and training should be established and implemented to facilitate the applicable elements of paragraphs 4, 5 and 8. Particular emphasis should be placed on subparagraphs 4.8, 5.1 to 5.7 and 8.4.
In cases where the CDFA technique is not used with high MDA(H), it may be appropriate to make an early descent to MDA(H) with appropriate safeguards to include the above training requirements, as applicable, and the application of a significantly higher RVR/Visibility.
This is from the new appendix 1.430.
In cases where the CDFA technique is not used with high MDA(H), it may be appropriate to make an early descent to MDA(H) with appropriate safeguards to include the above training requirements, as applicable, and the application of a significantly higher RVR/Visibility.
This is from the new appendix 1.430.
Only half a speed-brake
Would you say that the quoted Appendix principles
a) allow you to operate opposite to OPS 1.430 d(2) requirement - the paragraph, not appendix
or,
b) are provided to assist operators under special circumstances exempt from the general rule
?
Also note the quite significant minima penalty
FD (the un-real)
a) allow you to operate opposite to OPS 1.430 d(2) requirement - the paragraph, not appendix
All non-precision approaches shall be flown using the continuous descent final approaches (CDFA) technique unless otherwise approved by the Authority for a particular approach to a particular runway.
b) are provided to assist operators under special circumstances exempt from the general rule
All non-precision approaches shall be flown using the continuous descent final approaches (CDFA) technique unless otherwise approved by the Authority for a particular approach to a particular runway.
Also note the quite significant minima penalty
When calculating the minima in accordance with Appendix 1 (New), the operator shall ensure that the applicable minimum RVR is increased by 200 metres (m) for Cat A/B aeroplanes and by 400 m for Cat C/D aeroplanes for approaches not flown using the CDFA technique, providing that the resulting RVR/CMV value does not exceed 5 000 m.
