All Weather Operations — Page 61, Lesson 92

I want to walk you through the core requirements for All Weather Operations. This is a critical part of your training because it governs how we operate in low visibility, low cloud, and poor weather conditions — the times when precision and procedure matter most. Let's start with the foundation. The detailed operating procedures and instructions for all weather operations must be specified in the Operations Manual, or OM. That's the airline's own book of procedures. Those instructions must be compatible with the limitations and mandatory procedures contained in the Airplane Flight Manual, the AFM. The AFM is the manufacturer's legally binding document for that specific aircraft type. So the airline's OM cannot contradict the AFM — it must work within its limits. Now, what must those OM procedures cover? I'll walk through each item. First, checks for the satisfactory functioning of equipment both before departure and in flight. So before you push back, and during the flight, you need procedures to confirm that the all-weather equipment — things like autopilots, flight directors, radio altimeters — is working properly. Second, effects on minima caused by changes in the status of the ground installations and airborne equipment. Your decision height or RVR minimums aren't fixed numbers — if a ground-based ILS transmitter fails, or if your aircraft has a piece of equipment unserviceable, your minima may increase. The OM must cover how to adjust. Third, procedures for the take-off, approach, flare, landing, roll-out and missed approach. That's the full sequence from departure through to a go-around if the approach doesn't work out. Fourth, procedures to be followed in the event of failures, warnings — and this specifically includes HUD, HUDLS, EVS, and other non-normal situations. HUD is the Head-Up Display, HUDLS is Head-Up Display Landing System, and EVS is Enhanced Vision System — these are advanced systems that project flight information or infrared/sensor imagery onto a transparent screen in front of the pilot. The OM must tell you what to do if any of those fail or give a warning. Fifth, the minimum visual reference required. This is the absolute minimum you must see — typically approach lights, runway threshold, or runway markings — to continue below decision height. Sixth, the importance of correct seating and eye position. This is not trivial. If your eye is not at the design eye position, your view of the outside world through the windscreen is distorted, and you might misjudge the flare or miss visual cues. The OM must stress this. Seventh, action that may be necessary from the deterioration of visual reference. If you had the runway in sight but then lose it in fog or rain, the OM must specify what you do — typically a missed approach. Eighth, the requirement for all height calls below 200 feet to be based on radio altimeter, and for one pilot to continue to monitor the aeroplane instruments until the landing is complete. Below 200 feet, barometric altimeters can be inaccurate due to local pressure variations. The radio altimeter gives true height above the ground. And one pilot must stay heads-down on the instruments — not looking outside — all the way to touchdown. Ninth, the requirements for the ILS localizer sensitive area to be protected. The localizer signal is very sensitive to interference from vehicles, other aircraft, or even large buildings near the runway. The OM must specify how to keep that area clear during low-visibility operations. Tenth, the information used relating to wind velocity; windshear; turbulence; runway contamination; and the use of multiple RVR assessments. RVR is Runway Visual Range — how far you can see along the runway. Multiple RVR assessments mean you might have readings at the touchdown zone, mid-point, and stop-end. The OM must cover how to use that data. Eleventh, procedures to be used for four specific categories: (A) lower than Standard Category I approaches; (B) other than Standard Category II approaches; (C) approaches utilizing EVS — Enhanced Vision System; and (D) practice approaches and landing on runways at which the full Category II or Category III aerodrome procedures are not in force. So if you're doing a practice low-visibility approach at an airport that doesn't have the full certified Category II or III ground equipment, the OM must have special procedures for that. Twelfth, operating limitations resulting from airworthiness certification. The aircraft's certificate of airworthiness may impose specific limits — for example, a maximum crosswind for autoland, or a requirement for certain equipment to be serviceable. Thirteenth, information on the maximum deviation allowed from the ILS glide path or localizer. During an automatic approach, there are limits — typically a fraction of a dot on the ILS indicator — beyond which you must go around. The OM must state those limits. And finally, allocation of crew duties in the carrying out of the procedures above, to allow the Commander to devote himself or herself mainly to supervision and decision making. The captain should not be heads-down programming or troubleshooting — they should be monitoring the overall situation and making command decisions. The other pilot handles the detailed flying and checklist work. Now, there are also hard regulatory conditions. An operator shall not conduct Category II and III operations unless five conditions are met. First, each aeroplane is certificated for operations with a Decision Height below 200 feet, or with no Decision Height at all, and equipped in accordance with CS-AWO or an equivalent accepted by the Authority. CS-AWO is the Certification Specification for All Weather Operations — the European standard. So the aircraft must be type-approved for low-visibility operations. Second, a suitable system for recording approach and/or automatic landing success and failure is established and maintained to monitor the overall safety of the operation. The airline must keep data on every autoland — how many succeeded, how many failed, and why — to detect trends and maintain safety. Third, the operations are approved by the Authority. The national aviation authority — for example, the DGCA in India, or the EASA in Europe — must specifically approve the airline to conduct Category II and III operations. Fourth, the flight crew consists of at least two pilots. No single-pilot Category II or III operations. Fifth, the Decision Height is determined by a radio altimeter. Not by barometric altitude — it must be based on true height above the ground. Finally, there is a separate rule for low visibility take-offs. An operator shall not conduct low visibility take-offs in less than 150 metres RVR for Category A, B, and C aeroplanes, or 200 metres for Category D aeroplanes, unless approved by the Authority. Category A, B, C, and D refer to aircraft approach speed categories — Category D includes the fastest jets like the Boeing 747 or 777. So if you want to take off in RVR below those values, you need specific authority approval. That figure shows the typical layout of these requirements. Let me know if you have any questions on any of these points.