TWR visibility

[SSDD]

Its been a long time now, but I think when I was at Colgan we could shoot contact approaches. I even remember being able to go VFR if you could get the dispatcher to agree to do it VFR, we could also cancel IFR while still in the air and often did while going into most of the smaller outstations.

At my current airline we can't do any of that. Shoot we can't even shoot NDB apps anymore, or do circ apps when the wx is below VMC, or even shoot a vis app if the tower is closed. So I don't know if Colgan is "crazy" or if my new place is conservative to what most other airlines out there do.

Even though they are 121, turbo prop operators have different rules than jet operators.

 

[great cornholio]

so whats the deals


twr vis is 1/2 mile
rvr touchdown 1/4 mile


legal (cat 1)??

RVR is reported in feet not sm so you will see something like RVR 1200. RVR is controlling only for the runway it is installed on not the entire airport. From what I've seen it is very rare (not sure if I've ever seen it even once) where an airport has RVR and is reporting it on all runways. If you look at approach plates you will see that there is a listed min for both vis in sm and RVR in feet. There are a lot of apps out there that have mins listed as 1/2sm or 1800 RVR. So lets say they are reporting vis of 1/2sm and 1R RVR is 1000. You can't shoot the ILS for 1R because the RVR reported for 1R is less than 1200. However if 1L is long enough to land on or if the wind will let you land on 19L (and it isn't reporting an RVR) then you can shoot the ILS for either of those runways because you have the 1/2sm.

 

[paulsalem]

What if there is No RVR?
Atis is calling 1/4 mile.
Tower Vis is 2miles.
Need 1/2 mile for the approach.
Part 121 operation.

 

[regionalcap]

What if there is No RVR?
Atis is calling 1/4 mile.
Tower Vis is 2miles.
Need 1/2 mile for the approach.
Part 121 operation.

Good to go.

 

[paulsalem]

Good to go.

Reference?
(I believe you, just for future arguments)

 

[asayankee]

Reference?
(I believe you, just for future arguments)

Tower employees are "certified weather observers" and are therefore legal to use as "official" sources of weather. Remember, that ATIS can be up to an hour old. Yes you are able to accept an approach

 

[Oakum_Boy]

From

2-6-6. REPORTING WEATHER CONDITIONS
a. When the prevailing visibility at the usual point
of observation, or at the tower level, is less than
4miles, tower personnel shall take prevailing
visibility observations and apply the observations as
follows:
1. Use the lower of the two observations (tower
or surface) for aircraft operations.
2. Forward tower visibility observations to the
weather observer.
3. Notify the weather observer when the tower
observes the prevailing visibility decrease to less than 4 miles or increase to 4 miles or more.

xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx


2-6-7. DISSEMINATING WEATHER
INFORMATION
TERMINAL. Observed elements of weather information shall be disseminated as follows:
a. General weather information, such as “large
breaks in the overcast,” “visibility lowering to the
south,” or similar statements which do not include
specific values, and any elements derived directly
from instruments, pilots, or radar may be transmitted to pilots or other ATC facilities without consulting the weather reporting station.
b. Specific values, such as ceiling and visibility,
may be transmitted if obtained by one of the
following means:
1. You are properly certificated and acting as
official weather observer for the elements being reported.
NOTE
USAF controllers do not serve as official weather
observers.
2. You have obtained the information from the
official observer for the elements being reported.
3. The weather report was composed or verified
by the weather station.
4. The information is obtained from an official
Automated Weather Observation System (AWOS) or
an Automated Surface Observation System (ASOS).




These two sections seem to contradict each other, however it seems that if they state the visibility, then they have been certificated, and are acting as the official observer for the elements being reported.

Source: http://www.faa.gov/airports_airtraffic/air_traffic/publications/at_orders/media/ATC.pdf

 

[Flyin2low]

Takeoff and Landing requirements use surface visibilty reports, either in RVR or SM. If RVR is reported, it is controlling for the operation in question. The tower vis report (@75'AGL) is just to give operators a better understanding of the actual conditions, but doesn't override the reported vis (RVR+SM)

 

[moonship]

We = Great Lakes

 

[regionalcap]

Takeoff and Landing requirements use surface visibilty reports, either in RVR or SM. If RVR is reported, it is controlling for the operation in question. The tower vis report (@75'AGL) is just to give operators a better understanding of the actual conditions, but doesn't override the reported vis (RVR+SM)

I always thought it could override the reported visibility except for RVR. It is coming from a certified weather observer.

 

[Flyin2low]

I always thought it could override the reported visibility except for RVR. It is coming from a certified weather observer.

Nope. Like I said before, tower vis is reported at 75' AGL. Most runways are about 75' below that. If you are operating on a runway, RVR or reported surface vis are the only two things that can meet a takeoff/landing ops spec. Only an updated surface observation can override a surface observation.

 

[Oakum_Boy]

If the tower controller is the official weather observer on the field, then the prevailing visibility from that location is whats reported on the METAR/ATIS.

However, if the tower says "tower visibility xxxx", that's just an advisory thing until the surface observation is updated.

In the mean time, you have to use the lower of the tower visibility or surface observation.

Is that right?

 

[rptrain]

unless tower visibility is the "usual point of observation" it is added as advisory information. surface visibility, the prevailing visibility from the usual point of observation (usually an ASOS sensor), is the controlling value. unless RVR is installed and operating.

http://www.nws.noaa.gov/oso/oso1/oso12/fmh1/fmh1ch6.htm

 

[GuppyWN]

ATIS/AWOS/METAR is king unless you have an RVR for the particular piece of pavement you are using.

Tower visibility is meaningless in legalities.

Quit making it hard.

Gup

 

[trainer8]

At the 121 airlines I've been at(3) none were authorized to do contact approaches. Anyone know of a 121 carriers ops specs that allow these? I don't.

ALG used to allow contact aprroaches, but their FOM required VFR mins at the aerodrome to accept the request the approach.