VFR and IFR
There are two sets of rules for flying any aircraft: VFR and IFR. VFR stands for Visual Flight Rules. IFR stands for Instrument Flight Rules.
Depending on the weather conditions a pilot may opt for one set of rules or the other. Mostly, it’s the weather that makes the pilot fly VFR or IFR. What is the difference between VFR and IFR flying?
1- Aviating under VFR
VFR normally means “see and avoid”. Under VFR, an aircraft is flown just like driving a car with eye movement and the pilot can see where he is going.
VFR pilots maintain a ‘see and avoid’ principle when the visual meteorological conditions (VMC) are favorable. VFR is the usual way to fly a small craft. Under VRF, a pilot cannot fly through clouds, which means they must go under, around, or divert if the clouds form a block en route.
To fly VFR, Visual Meteorological Conditions have to be maintained. It means you cannot fly through clouds and need to keep a safe distance. In some types of airspace, you also have to see the ground. As VFR flights rule, pilots are responsible for seeing other aircraft and avoiding a collision.
They have to maintain vertical and horizontal separation. As per the Civil Aviation Authority of Nepal rules, an 8 kilometers horizontal separation is required for a flight under the VFR rules at and above 3,050 meters [10,000 feet] above mean sea level and 5 kilometers below 3,050 meters above mean sea level.
There must be no cloud within 1,500 meters [5,000 feet] horizontally or 300 meters [1,000 feet] vertically from the aircraft. Similarly, an aircraft must maintain an altitude of 300 meters [1,000 feet] over any congested area of a city, town, or settlement. In hills, the aircraft should maintain 600 meters [2,000 feet] altitude from the ground.
Flying VFR is beneficial in busy airspace. In Nepal for example, there can be long delays for IFR departures because there are so many requests.
2- Aviating under IFR
Under IFR rules, a pilot is authorized to fly into clouds in what is called zero visibility. It’s called instrument flight because the pilot navigates only by reference to the instruments in the aircraft cockpit.
Unlike VFR flights, IFR happens usually within controlled airspace and requires filing a flight plan, usually, ahead of time. The flying is not completely at the pilot’s discretion. Established waypoints and airways have to be used and the altitude for the flight is determined.
IFR requires a ceiling less than 300 meters [1,000 feet] above ground level and visibility of fewer than three miles. During flight under IFR, there are no visibility requirements, so flying through clouds or other conditions where there is zero visibility outside the aircraft is legal and safe.
According to air traffic controller Bhatta, additional time is required for the preparation of the IFR flight plan.
In controlled en-route airspace, the horizontal separation standard between the same types of aircraft flying at the same altitude is 5 minutes. If a smaller aircraft is ahead, for the bigger aircraft, the horizontal separation standard should be 10 minutes.
And if a bigger aircraft is ahead to land, for smaller aircraft, the horizontal separation standard should be 2 minutes. Therefore, for smaller planes, which are normally flown in VFR conditions, flights are delayed sometimes if the weather deteriorates to prepare for an IFR flight.
Filing VFR Flight Plans
Although position reports are not required for VFR flight plans, periodic reports to FSSs along the route are good practice.
Such contacts permit significant information to be passed to the transiting aircraft and also serve to check the progress of the flight should it be necessary for any reason to locate the aircraft, Pilot: “[Callsign], [Route], at [Time], VFR flight plan, [Departure Airport] to [Destination Airport]”
Closing VFR Flight Plans
A pilot is responsible for ensuring the VFR/DVFR flight plan is closed. Close the flight plan with the nearest FSS, or if not available, any ATC can relay your cancellation to an FSS. Towers do not normally close VFR/DVFR flight plans because they don’t know if a particular aircraft is on a flight plan or not.
Filing IFR Flight Plans
Pilots should file IFR flight plans at least 30 minutes before the estimated time of departure to preclude possible delays in receiving a departure clearance from ATC. When IFR weather conditions exist or are forecast at that airport, an IFR flight plan should be filed before departure.
Otherwise, a 30-minute delay is not unusual in receiving an ATC clearance because of the time spent processing flight plan data.
Traffic saturation frequently prevents control personnel from accepting flight plans via radio In such cases, the pilot is advised to contact a flight plan filing service to file the flight plan Additionally, mistakes can be easily made over the radio.
Flying on IFR Flight Plans
In addition to altitude or flight level, destination, and/or route changes, increasing or decreasing the airspeed by plus or minus 5% or 10 knots (whichever is greater) constitutes a change in a flight plan.
Closing IFR Flight Plans:
IFR flight plans may be closed at any time with either ARTCC, approach control, tower, or if unable, with FSS. When landing at an airport with a functioning control tower.
What is an IFR clearance, and what are the components?
The FAA defines TEC service as “the control of IFR en-route traffic within delegated airspace between two or more adjacent approach control facilities.” The service was created to increase the efficiency of ATC services. TEC routes are generally more direct and have less stringent separation minimums. Availability is dependent on ATC workload.
TEC flights are intended to be relatively short – generally two hours or less, and are conducted below 10,000 feet. Throughout the route, communications are managed through tower controllers and departure and approach controllers at a TRACON facility.
The Airport/Facility Directory publishes the available TEC routes for each airport in the system. Several airports can be grouped for the same route, with the only difference being the initial departure instructions, which you receive along with the clearance.
In addition to the airport published in the TEC section of the A/FD, tower en-route procedures can be used at airports in the vicinity of the major, published airports. You need to study the published route (or routes) from the A/FD in detail before getting into the airplane.
Make sure the airplane is equipped to handle the route and that the route applies to the correct aircraft classification (jet – J, turboprop – M, non-jet 190 knots or greater – P, and non-jet 189 knots or less – Q). No IFR flight planning needs to be filed with the flight service station or DUATS.
You can simply call clearance delivery or, if clearance delivery is not available, ground control, and request a “tower en-route” or “tower-to-tower” to your destination airport. Remember to give the controller your airplane type and suffix on the initial call. The controller will then issue your IFR clearance, and you’re good to go.
Can you fly IFR without a flight plan?
Flying IFR into new environments can be a serious challenge, particularly in busy airspace where controllers are talking nonstop, and it’s more important than ever to listen up and follow their instructions precisely.
For flights in congested areas, pre-published, low-level IFR routes make both pre-flight planning and actual flying much more straightforward and enjoyable.
No IFR flight plan needs to be filed with the flight service station or DUATS. You can simply call clearance delivery or, if clearance delivery is not available, ground control, and request a “tower en route” or “tower-to-tower” to your destination airport.
Remember to give the controller your airplane type and suffix on the initial call. The controller will then issue your IFR clearance, and you’re good to go.
Can you fly without a flight plan?
No person may operate an aircraft in controlled airspace under IFR unless that person has filed an IFR flight plan. Flight plans may be submitted to the nearest FSS or air traffic control tower (ATCT) either in person, by telephone, by computer, or by radio if no other means are available.
Pilots should file IFR flight plans at least 30 minutes before the estimated time of departure to preclude possible delays in receiving a departure clearance from ATC.