737-800 approach category in Europe.
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737-800 approach category in Europe.
I was under the impression that the -800 should be operated under approach category D in Europe, but having seen one at Chambery recently, am I to assume it's actually C?
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Cat C as far as I've seen.
If your company circles with gear down/flap 15 you can apply C there as well, those applying gear up until downwind Cat D, flown both sets of SOPs...
If your company circles with gear down/flap 15 you can apply C there as well, those applying gear up until downwind Cat D, flown both sets of SOPs...
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Not sure what the FCTM says about Europe. But the FAA criteria on our B738 FCTM states that B738 can either be Cat C or D depending on the Maximum Landing weight. Perhaps you can check on your company FCTM?
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Isnt it based on Final approach speed?
CAT C is to 140Kts, which the 800 is 142 kts, hence Cat D
In reality, I think that 142 kts is not a realistic FAS....just a bit faster.
CAT C is to 140Kts, which the 800 is 142 kts, hence Cat D
In reality, I think that 142 kts is not a realistic FAS....just a bit faster.
Last edited by underfire; 29th Nov 2016 at 07:31.
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As far as i know EASA doesnt allow an on the fly change of category, hence only one for those in europe, and no flaps 15 normal landing either. Which is of course different than in FAA country.
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I understand that some airlines have limited the weights to get it to CAT C, and to minimize the landing fees.
In RNP procedure design, the 800 is Cat D, becuase the FAS of below 140kts for Cat C is not realistic, especially on the auto.
In RNP procedure design, the 800 is Cat D, becuase the FAS of below 140kts for Cat C is not realistic, especially on the auto.
Originally Posted by Underfire
Isnt it based on Final approach speed?
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Sorry, but the CAT does exactly relate to the final approach speed, the speed at threshold, depending on the criteria. For a procedure design, that CAT speed is used for the entire final approach segment, from the FAF on in. There are some differences between TERPS and PansOps, but for the designer, there is not, for example, under ICAO, you cannot use 160 kts for the final approach segment for CAT C. Likewise, with TERPS, you are not going to be circling to land a 738 at 140 kts...
While the tables and criteria claim differences, the design criteria is basically the same.
If there is a turn after the FA, the turn max speed is the CAT speed. If there is a turn that ends in the FAF, that CAT speed is used back to the beginning of the turn...
PansOps: The following ICAO table indicates the specified IAS speed range, in knots, for each category of aircraft to be utilised whenb conducting the maneuver or approach phase specified. These speed ranges have been considered by the PANS-OPS approach designer when calculating airspace and obstacle clearance requirements for each segment of the procedure.
FAA TERPS is a bit different.
According to TERPS criteria, an aircraft shall normally fit into only one category. However, if it is necessary to maneuver at speeds in excess of the upper limit of a speed range for a category, the minimums for the next higher category should be used.
TERPS categorisation has identical speed ranges for the threshold speeds for each of the five categories, but the approach procedures designed under TERPS do not consider the circling speeds
TERPS has a simple table for the final approach segment:
EDIT: Look at this from the programming and automation perspective. Since there is no speed restriction coded on threshold, how would you automate the ac going from 160 kts on final to a max of 140 kts over the threshold? In the programming, it is per segment in the coding in the FMS, the ac knows that at the FAF, I am a Cat D, and will manage the speed to meet that target. When you are on auto, are you placing speed restrictions on threshold, or at the FAF, or does the ac manage that?
so Vat+5kts, the 738 is not exceeding 140Kts at threshold? That would take a bit of intervention...
While the tables and criteria claim differences, the design criteria is basically the same.
If there is a turn after the FA, the turn max speed is the CAT speed. If there is a turn that ends in the FAF, that CAT speed is used back to the beginning of the turn...
PansOps: The following ICAO table indicates the specified IAS speed range, in knots, for each category of aircraft to be utilised whenb conducting the maneuver or approach phase specified. These speed ranges have been considered by the PANS-OPS approach designer when calculating airspace and obstacle clearance requirements for each segment of the procedure.
FAA TERPS is a bit different.
According to TERPS criteria, an aircraft shall normally fit into only one category. However, if it is necessary to maneuver at speeds in excess of the upper limit of a speed range for a category, the minimums for the next higher category should be used.
TERPS categorisation has identical speed ranges for the threshold speeds for each of the five categories, but the approach procedures designed under TERPS do not consider the circling speeds
TERPS has a simple table for the final approach segment:
EDIT: Look at this from the programming and automation perspective. Since there is no speed restriction coded on threshold, how would you automate the ac going from 160 kts on final to a max of 140 kts over the threshold? In the programming, it is per segment in the coding in the FMS, the ac knows that at the FAF, I am a Cat D, and will manage the speed to meet that target. When you are on auto, are you placing speed restrictions on threshold, or at the FAF, or does the ac manage that?
Assuming Australia operates to PANS-OPS, it's got nothing to do with final approach speed. The speed that determines the category is Vat, which is normally 1.3Vs. Our "approach" speed is Vat+5kts (not 737 but "normal" big jet ops, I suspect).
Last edited by underfire; 1st Dec 2016 at 00:34.
You've lost me.
The categories are based on Vat. End of story. If 1.3Vs (ie Vat) in the 737 is greater than 140kts at MLW (as per the Flight Manual), then it's Cat D. If 1.3Vs is 140 or less, it's Cat C. As far as I can see, it's got nothing to do with Approach speed. If I chucked on +15 for wind, do I then have to brief a Cat D approach? Your chart shows you can be doing 160KIAS quite happily as a Cat C, so it cannot be based on "Approach Speed" being 140 or less for Cat C. It's based on Vat/13.Vs only.
The categories are based on Vat. End of story. If 1.3Vs (ie Vat) in the 737 is greater than 140kts at MLW (as per the Flight Manual), then it's Cat D. If 1.3Vs is 140 or less, it's Cat C. As far as I can see, it's got nothing to do with Approach speed. If I chucked on +15 for wind, do I then have to brief a Cat D approach? Your chart shows you can be doing 160KIAS quite happily as a Cat C, so it cannot be based on "Approach Speed" being 140 or less for Cat C. It's based on Vat/13.Vs only.
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@Underfire:
The table extract that you've shown is related to the provisions PANS-OPS makes as part of the design criteria.
@All
The Aircraft Approach Categories are based on aircraft certifications and, in some cases, specific operational approvals if the normally certified approach speed is to be permitted to operate as a lower category in a particular country.
Basically, it's defined by ICAO in the following way - for both conventional and PBN procedures:
The criterion taken into consideration for the classification of aeroplanes by categories is the IAS at threshold (Vat) which is equal to the stall speed (Vso) multiplied by 1.3 or stall speed, in landing configuration at maximum certificated landing mass (Vso) multiplied by 1.23. If both Vso and Vslg are available, the higher resulting speed at
threshold (Vat) is used.
It's not changeable on a case-by-case basis, or even dynamically based on Vat used.
However, when using Vis Man/Circling, aircraft can elect to use the circling area (& minima) of a higher category if they wish.
Also, the B738 is an Approach Category C.
Refer also BOEING 737-800 - SKYbrary Aviation Safety
@Underfire:
Re your comment about the RNP design for the 738 and it needing to be Cat D because it can't go as low as 140kts.
Read the ICAO table you've posted. The Final APCH speeds allowed for as part of normal design allow for speeds in the Final APCH for RNP procedures (and conventional procedures for that matter) to be up to 160KIAS.
Check out Table 3.1(b) in ICAO Doc 9905.
So, your statement is not 100% correct. The only case where it could be correct is where you require a Cat C aircraft to fly the Final faster than they normally would and than they're normally certified for.
The table extract that you've shown is related to the provisions PANS-OPS makes as part of the design criteria.
@All
The Aircraft Approach Categories are based on aircraft certifications and, in some cases, specific operational approvals if the normally certified approach speed is to be permitted to operate as a lower category in a particular country.
Basically, it's defined by ICAO in the following way - for both conventional and PBN procedures:
The criterion taken into consideration for the classification of aeroplanes by categories is the IAS at threshold (Vat) which is equal to the stall speed (Vso) multiplied by 1.3 or stall speed, in landing configuration at maximum certificated landing mass (Vso) multiplied by 1.23. If both Vso and Vslg are available, the higher resulting speed at
threshold (Vat) is used.
It's not changeable on a case-by-case basis, or even dynamically based on Vat used.
However, when using Vis Man/Circling, aircraft can elect to use the circling area (& minima) of a higher category if they wish.
Also, the B738 is an Approach Category C.
Refer also BOEING 737-800 - SKYbrary Aviation Safety
@Underfire:
Re your comment about the RNP design for the 738 and it needing to be Cat D because it can't go as low as 140kts.
Read the ICAO table you've posted. The Final APCH speeds allowed for as part of normal design allow for speeds in the Final APCH for RNP procedures (and conventional procedures for that matter) to be up to 160KIAS.
Check out Table 3.1(b) in ICAO Doc 9905.
So, your statement is not 100% correct. The only case where it could be correct is where you require a Cat C aircraft to fly the Final faster than they normally would and than they're normally certified for.
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So, your statement is not 100% correct. The only case where it could be correct is where you require a Cat C aircraft to fly the Final faster than they normally would and than they're normally certified for.
First off is the difference between ICAO and FAA criteria.
Next is the procedure design. Procedure design and coding is by leg. The final approach segment, from the FAF to threshold is a leg. You cannot set a variable speed on the final approach leg, as it is a terminator.
ie you cannot begin a leg at 160 and end it at 140...you begin the leg at the speed. If the procedure is a CAT C, the ac will hit 140kts at the beginning of that leg. That is just the way the coding works.
This is why there is a disco with RNP vs non-RNP traffic.
For a CAT C aircraft, the RNP ac will be at 140 kts at the FAF, it will not be at 160 kts, and slow to 140 at threshold.
Also, the B738 is an Approach Category C.
Boeing 737-800 D-III 142
Boeing 737-800W D-III 142
This is based on Flaps 30 and 60K wt, a bit less than the MLW (flaps 40 is 141 at 65K) but you dont get to pick and chose CAT
The categories are based on Vat. End of story.
Here is the FAA design criteria table right from the manual...it shows the MAX speeds for the different SEGMENTS. It may be based on the 1.3Vs, but it is for the segment...
According to the FAA criteria, the CAT C ac cannot exceed 140 kts for the entire final approach segment.
Last edited by underfire; 1st Dec 2016 at 07:45.
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As i mentioned above, ours were certified as Cat C, no matter if we used flaps 40, which went up to over 140kts, or flaps 30 which was nearly always faster. For circling we used the larger area of Cat D though.
I don't know what you mean in this context by "coding", but the FMC displayed threshold speed was variable and adjusted according to chosen flap setting and weight plus inserted wind correction (minimum 5kts).
I don't know what you mean in this context by "coding", but the FMC displayed threshold speed was variable and adjusted according to chosen flap setting and weight plus inserted wind correction (minimum 5kts).
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I understand, and I was never quite certain how the 738 gets cert as CAT C, you would have to take the MLW down pretty far for that to happen. (flaps 30 used to be the standard for cert)
Of course the speed is variable per conditions, but there is the CAT speed to consider for the procedure.
In regards to the coding, the ac is managing the speeds. While not such an issue in a straight in, but when there are turns, the ac has to use all of the variables, especially speed and max bank angle. Exceed the limits, like you stated, if it cannot get down to 140kts for the turn, you off track and disco.
This is what happened with Alaska at Palm Springs, a CAT C procedure designed for the 737-700, but when they got the 738, they could not make that last turn to final, and the ac would disco. Could not make that work with the 800.
Of course the speed is variable per conditions, but there is the CAT speed to consider for the procedure.
In regards to the coding, the ac is managing the speeds. While not such an issue in a straight in, but when there are turns, the ac has to use all of the variables, especially speed and max bank angle. Exceed the limits, like you stated, if it cannot get down to 140kts for the turn, you off track and disco.
This is what happened with Alaska at Palm Springs, a CAT C procedure designed for the 737-700, but when they got the 738, they could not make that last turn to final, and the ac would disco. Could not make that work with the 800.
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As far as category is concerned, Cat C is standard in EU as generally MLW is set not to exceed 65T.
Regarding flap 30/40, it is not based on 30, but based on slowest possible speed, thus 40 is taken to enable category C.
Table above uses rounded figures at 5t intervals, digital files provide more accurate data and sometimes weights are directly derived from lb tables for certification converted into kg, thus the odd numbers in some operators...
In addition, wing configuration is to be taken into account, winglets, scimitar, or none...
Regarding flap 30/40, it is not based on 30, but based on slowest possible speed, thus 40 is taken to enable category C.
Table above uses rounded figures at 5t intervals, digital files provide more accurate data and sometimes weights are directly derived from lb tables for certification converted into kg, thus the odd numbers in some operators...
In addition, wing configuration is to be taken into account, winglets, scimitar, or none...
Originally Posted by Underfire
Far from the end of the story, what do you think the procedure is designed for?
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A Cat C aeroplane can legally do 160 down final. It seems that you need to change your RNP design parameters to cope with that.
The explanations in the posts details how it works, it also shows why there are known issues with RNP traffic vs non-RNP traffic. There are plenty of stories and dialog about the RNP ac being too slow on final. That is one of the reasons.
The issue is not if it is legal or not to exceed 140kts on final for CAT C, it is simply that the coding will not accept that. There is a speed per leg, that is just the way the FMS understands it.
The FMS is horribly outdated as far as the programming goes, and with the way certification of systems goes, it it not likely to get better very soon.
Skyjob...the CAT is based on MLW and flaps 30, you can search that criteria online if you want, and I did provide a table. There is always a set standard that the criteria is based on.
Looking at the table, you have to look pretty far down the weight table to get below 140 kts, and in reality, you see very, very few 738's going over the threshold at 140kts...
Just so you are aware, there are other requirements such as runway length that are also based on flaps 30.
I understand that quite a few carriers SOP is flaps 30, that came about when fuel costs were so high, and flaps 30 was to save fuel.