C-055 2 NAV Rule. Lower Ceiling or Lower Vis?

[TXAce]

Hypothetical question I think I already know the answer to but still curious. If I have a list of options, let’s say my choices of mins are
ILS 16L. 200-1/2

GPS 34C - 400-1

NDB RWY 16R - 500 3/4

Which would we better to use for the 2nd Navaid? Lower ceiling or lower vis

I think it’s lower vis but I want to make sure

 

[bbmikej]

Depends on what you need to suit the forecast. If visibility is forecast at 1 1/4 with a 900 foot ceiling, you take the vis. If forecast is 2 miles vis with a 600 ft ceiling, you take the ceiling.

 

[Stumped]

What are forecast winds for alternate at ETA? What kind of approach are you using at your destination? Both are factors.

 

[McCrosky]

I’d pick a different alternate

 

[retrodx]

Hypothetical question I think I already know the answer to but still curious. If I have a list of options, let’s say my choices of mins are
ILS 16L. 200-1/2

GPS 34C - 400-1

NDB RWY 16R - 500 3/4

Which would we better to use for the 2nd Navaid? Lower ceiling or lower vis

I think it’s lower vis but I want to make sure

Depending on what you use, either way you’re screwed. If this was my only option, I’d just use the 1 navaid rule on the ILS with higher vis and call it a day. You can save the lower vis as a backup or… just go with a different alternate.

 

[Burrito]

Stop using SEA as an alternate

 

[Pepwave1]

Hypothetical question I think I already know the answer to but still curious. If I have a list of options, let’s say my choices of mins are
ILS 16L. 200-1/2

GPS 34C - 400-1

NDB RWY 16R - 500 3/4

Which would we better to use for the 2nd Navaid? Lower ceiling or lower vis

I think it’s lower vis but I want to make sure

What are the forecast winds?

 

[Delta Echo]

For 2 runways it is the higher of both vis and cig

 

[iono]

For 2 runways it is the higher of both vis and cig

View attachment 74722

i think that’s understood. in the example given by OP, the combination of approaches using the GPS approach gives you a better ceiling while the NDB approach gives you slightly better vis

 

[Pepwave1]

i think that’s understood. in the example given by OP, the combination of approaches using the GPS approach gives you a better ceiling while the NDB approach gives you slightly better vis

There is an 80 degree difference…and the 2 navaid rule says “suitable runway”

 

[iono]

There is an 80 degree difference…and the 2 navaid rule says “suitable runway”

it’s a hypothetical and weather wasn’t posted anywhere