TTX – 20

radio altimeter

6 (RVR at least 350 metres)

Decision Height: <100ft (30m)
OR
NO decision height (=0)

RVR: <300m

Decision Height: <100ft (30m) but not less than 50ft (15m)

RVR: <300m but not less than 200m

4 (RVR <300 to 200 metres)

Decision Height: <50ft (15m) 
OR
NO decision height

RVR: <200m but not less than 50m

CAT III A: Minimum to allow pilot do decide whether aircraft will land in touchdown zone

CAT III B: Minimum to allow pilot to decide whether aircraft will land in touchdown zone and ensure safety during roll-out

1 (<200 to 50 metres)

NO decision height

NO RVR limitations

How does the pilot find the way off the runway.

-> problem for controller about following aircraft

Reduced Aerodrome Visibility Conditions

4 different conditions

Visibility sufficient to pilot to taxi and avoid collisions with other traffic on taxiways and intersections by visual reference, and for personnel of control units to exercise control over all traffic on the basis of visual surveilance.

not counted as reduced aerodrome visibility condition but normal state

Visibility sufficient for the pilot to taxi and avoid collision with other traffic on taxiways and intersections by visual reference, but insufficient for personnel of control units to exercise control over all traffic on the basis of visual surveillance.

Visibility sufficient for the pilot to taxi but insufficient for the pilot to avoid collision with other traffic on taxiways and intersections by visual reference, and insufficient for personnel of control units to exercise control over all traffic on the basis of visual surveillance. 

For taxiing this is normally taken as visibilities equivalent to an RVR of less than 400m but more than 75m

Visibility insufficient for the pilot to taxi by visual guidance only.

This is normally taken as an RVR of 75m or less.

RAVP -> reduced aerodrome visibility procedures
on aerodromes without CAT II/III and LVD operations

LVP -> low visibility procedures
on aerodromes with CAT II/III and LVD operations

Local procedures shall define the transition between visibility conditions, based on visual references, MET observations and reports from taxiing aircraft (either alone or the combination of), taking into account local aerodrome and traffic characteristics.

- reduction of persons and vehicles on manoeuvring area to essential minimum
- discontinuation of temporary works in progress on manoeuvring area
- marking of work areas as unavailable for use
- follow me vehicle for taxiing aircraft
- guidance for emergency vehicles

defined in local instructions

no

- no conditional clearances in conditions 3+4 (avoid)

- if ground surveillance, increased traffic information shall be provided to assist pilot awareness

To support safe instrument flight operations when RVR is less than 550m and/or decision height is less than 200ft.

- require restrictive measures in specific meteorological conditions

- protect the physical area around the runway to ensure safety – ILS GP & LOC critical and sensitive areas to avoid disturbance of ILS signals

- apply appropriate spacing between successive landing and/or departing aircraft

Areas extending beyond the critical areas where the parking and/or movements of vehicles, including aircraft, is controlled to prevent the possibility of unacceptable interference to ILS signal.

preparation phase -> necessary preparatory action (specified in local instructions) flight crew not informed

operations phase -> flight crew is informed "low visibility procedures in operation"

termination phase 

RVR of TDZ is <800m and/or vertical visibility or ceiling drops to <300ft (may be initiated earlier if conditions are deteriorating quickly)

RVR of TDZ is <550m and/or vertical visibility or ceiling drops to <200ft

No -> tower supervisors shall ensure that the ATIS reflects which runways are subject to LVP

- movement on manoevring area restricted to essential minimum
- stop bars shall be used and aircraft cleared to the CAT II or III stop bar ("taxi to CAT II stop bar, report lights in sight")
- procedures shall be implemented to separate aircraft & vehicles taking into account ground ATS surveillance systems
- additional spacing may be required by TWR to allow lead aircraft to vacate runway and clear the LOC sensitive area or departing aircraft passes LOC before succeeding acft reaches 2 NM
- no immediate take-offs

"SWR123, taxi to CAT II stop bar taxiway alpha, runway 32, report light in sight."

Obstalce Free Zone

A volume of airspace in the immediate vicinity of a precision approach runway. This zone shall be kept free from fixed objects, other than lightweight frangible mounted aids required for air navigation purposes.

During CAT II or CAT III operations the OFZ is kept clear of all obstacles, such as vehicles, persons and aircraft at all times that an aircraft making an approach is below 200ft AGL.

ILS critical area:
area of defined dimensions about localizer and glidepath antennas; vehicles and aircraft to be excluded during all IFR operations

ILS sensitive area:
area extending beyond critical area where parking and/or movements of vehicles, including aircraft, is controlled to prevent the possibility of unaccepted interference to ILS signal – must be clear for CAT II and III

runway is reduced to CAT I only, unless runway protection available by other means

SHOULD be kept clear of all vehicles and aircraft form the time when aircraft reaches 2 NM from touchdown until reduced to taxispeed

MUST be kept clear before an arriving aircraft reaches a point 1 NM from touchdown