When we drive our cars, we always have to make sure we are able to see outside. Without being able to see outside, driving would not only be dangerous, but the basic principles would break down. After all, you can't blindfold a human being and have them drive from Point A to B without hitting every curb and pole along the way (unless they are Chuck Norris). Flying is a little bit different. While all new pilots initially learn how to fly VFR, that is to say with reference to the outside natural horizon of the earth, they eventually transition to IFR (Instrument Flying Rules), which yes you guessed it, is the opposite. IFR is the way most commercial airplanes fly around the world. IFR itself has two sub-sects. Firstly, IFR could mean you are flying under the use of your aircraft instruments for guidance, but can still see outside (i.e. aircraft that fly high up in cruise on a clear sunny day). Alternatively it could mean flying in IMC (Instrument Meterological Conditions), where you are using instruments to guide and fly the aircraft, while not being able to see anything outside (i.e. cloud, fog, precipitation, etc). IFR skills are of utmost importance to all pilots, not only those involved in the traditional commercial operations. For general aviation pilots, it is a key skill to keep because it can save lives in unplanned situations (pilot losing complete outside reference). For the majority of commercial pilots however, IFR flying is second-nature, and arguably a lot easier. Let's go on an imaginary IFR flight with you our pilot, and explore each of the 3 major sub-sects of IFR.
In Canada, IFR flying is broken into 3 major portions; Departures, Cruise, and Arrivals/ Approaches. Each of these sub-sects has governing rules which are laid out quite nicely by the cap-gen, considered "the bible of IFR flying." It is a condensed format version of the CAR's (Canadian Aviation Regulations).
Trust me, it is a blessing not to have to decode the meaning of those lawyer-like terms they use in the CAR's. Ask any IFR pilot, they swear by this document. The cap-gen lays out, in plain english, exactly the information you need for the various phases. In Canada, departures are governed by visibility. You must have a minimum 1/2 SM (statute mile) visibility in order to takeoff. Larger airports and some operators have additional procedures to operate below the aforementioned limit, but for the majority of flying this rule is the minimum. So here you are arriving at the airport and checking the weather for your flight from Toronto to Thunder Bay. There is light rain outside, clouds at 1500' but above 14000' most of that weather seems to give way to clear blue skies. You use a variety of tools to check the visibility, such as RVR (Runway Visual Range: a measurement taken by sensors on the runway), METAR reports, tower visibility, and if required, visibility determined you, the pilot. The RVR tells you the visibility is 1 sm, which means you are above the 1/2 sm restriction. Fuelled up, engines running, and aircraft all setup, you request the controller on the ground for your IFR clearance (a set of instructions to follow to be able to depart successfully). Remember, past the takeoff you will not see anything outside so these instructions keep you safe from the ground and other aircraft.
You depart and blast through most of the weather abiding by the exact instructions which you received in the clearance on the ground. Passing 18000' you enter IFR cleared airspace. Everything above this, is airspace where you are only allowed into if you are capable of flying IFR, have been instructed to climb into, and are able to maintain IFR for the entire duration of the portion. Normally it might look like blue skies up here, but that's only because you are now above most of the weather. As you climb through the last few clouds, the sky gets immensely bright and transforms into a stunning array of bright blues with a well defined white horizon, and the clouds below you looking smaller and smaller as you climb higher.
Despite being able to see the bright blue sky outside, you are still flying with reference to the instruments, as is every other aircraft flying above this barrier (thus it is not IMC but certainly IFR). There are various altitude "barriers" for entering/ cruising in IFR. For your flight from Toronto to Thunder Bay, this altitude is 18000'. In the northern and arctic parts, this "barrier" is 23000' and 27000', respectively. You have levelled off at 23000', meaning until it is time for descent you are now maintaining this altitude. ATC can see you on radar, and will periodically switch you to the next controller. There are some additional elements of airspace regulations, but we will keep it simple for now. About an hour and a half into your flight, you receive a notification from your aircraft system that you are about to reach TOD (Top of Descent). This is the time where you set yourself up to descend into Thunder Bay, prep for the approach and landing phase, as well as request ATC for your descent clearance.
Shortly after the notification for TOD, you are cleared to descend down to 6000.' You comply and set the aircraft up for descent. You are one of the lucky pilots and have autopilot to manage the flying for you. In accordance with your company regulations and descent planning, you setup a 3:1 descent. That is, you travel 3 miles of distance for every 1000' you lose (this is also the generic industry standard). This sets you up nicely for the approach and landing phases. In Canada, the approach phase is governed by the same aforementioned RVR values, while landings by DH/MDA (Decision Height/ Minimum Descent Altitude). See the figure below for what DH/MDA looks like. As you go through your descent, you pull out the approach plate you are most likely going to receive in accordance with the weather in Thunder Bay. You brief this plate to your co-pilot and yourself so that you understand what the aircraft will be doing, where it will be going, and what to expect in the landing phase, including the missed approach phase (more on this later). Looks like the same weather system from Toronto is hanging around here too, meaning below about 14000' you will enter conditions which will reduce your ability to see outside. Infact, you determine the visibility to be 1 mile, and ceilings of 300' AGL (Above Ground Level). With a limit on the plate for 1 mile and 250' this puts you close to the limit for conducting the approach. Through 14000' as expected, you enter the clouds and immediately all the blue skies and bright light you enjoyed vanishes to give way for the dark grey cloud cover. At the same time, you receive instruction to plan for the RNAV (GPS approach) onto runway 25 and to head direct to the 10 mile fix (usually associated with a name as well). Since you had already expected this, all you are doing now is guiding your GPS directly to the said 10 mile fix, which in reality is just an imaginary point created in space by GPS with lateral and vertical restrictions.
Through 8000' ATC clears you for the RNAV approach onto runway 25 into Thunder Bay. Your pre-planned descent makes your life easy and all you have to do now is hit the approach activate button, while your autopilot flies the approach. You also pull out the approach plate.
An approach plate is a one page document which lays out the approach in map form, and shows where each waypoint or "fix" is located. It also includes all the safe altitude limitations which keep you clear of obstacles and the ground. Remember, throughout this whole process you can't see anything until the very last moment, so having these restrictions are incredibly important. You pass each of the waypoints and their vertical restrictions correctly and continue the approach. As you pass through 2500' you are cleared to land and your RadAlt (Radar Altimeter) turns on which gives you a readout of your altitude above the ground. You compare this to the limitations published on the approach plate. Should you see the runway prior to this limit, you can continue to land. If you are not able to see it however, then you must execute a missed approach. A missed approach occurs when you do not receive the required visual reference to the runway, in which you immediately transition to follow the missed approach instructions, so you can contact ATC and attempt the approach again or fly to your alternate airport (this is pre-planned in the flight planning stage prior to departure). About 100' above the 250' limit, suddenly you gain enough visibility to see the runway lights which is legally enough visual reference to continue to land. You transition quickly to visual flying and land. Finally you are on the ground, proceeding forward to taxi into your parking spot.
From your initial descent out of 23000' to touchdown, the whole sequence takes about 20 minutes. These 20 minutes are critical, in that the task saturation is almost at its highest and you must execute the entire sequence without any deviations. It takes meticulous planning, and good experience. In all of the IFR flying, the missed approach is by far the most stressful and mentally demanding. That is because while the aircraft has arrived at a point where the runway cannot be seen, you must be able to transition from a landing sequence to a takeoff sequence by applying power, bringing your gear and flaps up, and flying the approach, while communicating with ATC of the situation and flying the published procedure to a tee, all of this in a matter of seconds. While there is almost always a co-pilot who is there to assist, just the sheer amount of workload to transition between the two aspects demands pitch perfect crew communication and management. Should there be miscommunication or other issues rising, the whole situation can turn catastrophic very quickly. This is why the briefing we pilots do during the descent phase is so important; it cements the entire procedure so that absolutely nothing is left to question when our skills are required the most. IFR flying in Canada, as you can see is not difficult by any measure, but it does require good training and lots of experience. There are some differences between what we learn in training, and line flying. Most of these differences exist to make the procedures more efficient, and abide to greater levels of restrictions. There are also more nuanced portions of departures, airspace classification, and complex standard terminal arrival routes (STAR's), all of which are beyond the scope of this post.
Most of us pilots who regularly fly IFR will agree that IFR is far, far easier than VFR flying. ATC is almost always instructing you on every move you make, thereby there is less effort from your end to manage since the whole flight is essentially scripted by directions and pre-planned procedures. There is little left up for debate and since every aircraft is flying IFR alongside you, there is a general sense of uniformity. While not being able to see anything outside might seem intimidating at first, it is for sure a skill that is cemented as second nature by good training and lots of experience. The next time you are blessed by the window seat, and notice the blue skies give way to near zero visibility, you now know what is generally going on in the cockpit and how you will arrive at your destination, safely.
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