B737-800 Approach Category
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B737-800 Approach Category
Dear all,
Are there any ideas out there regarding the B737-800 Approach Category? Is Cat “C” or “D” and why?
In ICAO Aircraft Operations Vol.1 Flight Procedures Table 1-4-1-2 it states that:
Cat “C” VAT = 121-140kts
Cat “D” VAT = 141-165kts
IAS at Threshold (VAT) =
· 1.3 VSO Stall Speed OR
· 1.23 VS1G Stall Speed
in Landing Configuration at Maximum Certified Landing Weight.
If both VSO andVS1G are available, the higher shall be applied.
The MCLW on our a/c is 66360kgs.
In the AFM it states that Flaps 40 VREF speed equals the Landing Speed which equals or greater 1.23 VS1G Stall Speed.
In the FCTM Section 5.2 it states that the 737 is classified as class “C” for straight in Approaches and for Circling Approaches the anticipated circling speed at the actual weight is used to determine the required Approach Minimums (Cat “C” or “D”).
In the QRH, PI Section 20.5, in the VREF table following a Weight of 66000kgs(<66360kgs) with Flaps 40 you are coming up with a VREF speed of 142kts.
Even in the FMC 10.7 version if you insert a weight of 66.3, will give you a Flaps 40 VREF of 142 kts.
2 kts above the Cat “C” limit with F40 in MCLW.
Waiting for your feedback!!
Are there any ideas out there regarding the B737-800 Approach Category? Is Cat “C” or “D” and why?
In ICAO Aircraft Operations Vol.1 Flight Procedures Table 1-4-1-2 it states that:
Cat “C” VAT = 121-140kts
Cat “D” VAT = 141-165kts
IAS at Threshold (VAT) =
· 1.3 VSO Stall Speed OR
· 1.23 VS1G Stall Speed
in Landing Configuration at Maximum Certified Landing Weight.
If both VSO andVS1G are available, the higher shall be applied.
The MCLW on our a/c is 66360kgs.
In the AFM it states that Flaps 40 VREF speed equals the Landing Speed which equals or greater 1.23 VS1G Stall Speed.
In the FCTM Section 5.2 it states that the 737 is classified as class “C” for straight in Approaches and for Circling Approaches the anticipated circling speed at the actual weight is used to determine the required Approach Minimums (Cat “C” or “D”).
In the QRH, PI Section 20.5, in the VREF table following a Weight of 66000kgs(<66360kgs) with Flaps 40 you are coming up with a VREF speed of 142kts.
Even in the FMC 10.7 version if you insert a weight of 66.3, will give you a Flaps 40 VREF of 142 kts.
2 kts above the Cat “C” limit with F40 in MCLW.
Waiting for your feedback!!
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It's very simple for anything other than a circling approach it's Cat C otherwise for circling it's Cat D. I would say the logical answer is safety. You try a circling approach in a 737 at Cat C minimums. Sure you could do it, but would it be as safe with that little extra distance you gain under Cat D?
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Not sure about the CAT C/D criteria for final approach and the numbers you quote. I fly -700 & -800, can't quote for -900. Our MLW is less than yours so we fall into C.
For a circle the FCTM quotes 2 categories. I understand that for 2 engines F15 gear down it is CAT C; SE ops where circling is at F5 it is CAT D due higher speed.
Regarding Wx minima for circling; I'm always amazed at 2400m being used. If you do the maths and calculate the turning radius for 150kts I think you'll find that the diameter is >2400m. Thus you'd lose sight of the RWY turning base. Hence a CAA in an older operation insisted we use 3600m in our Ops manual. However, in JAR OPs 2400m is legal.
It's a little the same with some NPA approaches where the required vis is far too short considering the distance you are out at MDA. They don't tie up and you'd never see the Visual reference at MDA if the vis is at minima. However, you are allowed to go and have a look. Possibly better than diverting when in fact the estimated vis was from the tower whereas you are 2-3nm away on appraoch. It might be OK out there. Same could be said for the circle. It takes good crew discipline not to push it too far. So perhaps it's not an exact science.
For a circle the FCTM quotes 2 categories. I understand that for 2 engines F15 gear down it is CAT C; SE ops where circling is at F5 it is CAT D due higher speed.
Regarding Wx minima for circling; I'm always amazed at 2400m being used. If you do the maths and calculate the turning radius for 150kts I think you'll find that the diameter is >2400m. Thus you'd lose sight of the RWY turning base. Hence a CAA in an older operation insisted we use 3600m in our Ops manual. However, in JAR OPs 2400m is legal.
It's a little the same with some NPA approaches where the required vis is far too short considering the distance you are out at MDA. They don't tie up and you'd never see the Visual reference at MDA if the vis is at minima. However, you are allowed to go and have a look. Possibly better than diverting when in fact the estimated vis was from the tower whereas you are 2-3nm away on appraoch. It might be OK out there. Same could be said for the circle. It takes good crew discipline not to push it too far. So perhaps it's not an exact science.
