VFR or IFR Flight


By Kyle Ramsey

To help the student understand the reasons why he or she might choose to fly VFR or IFR in certain circumstances.

After completing this lesson the student will understand the strengths and weaknesses of choosing to file and fly using VFR or IFR parameters. The student should then be able to choose the most appropriate flight rules.

None, however understanding of basic flight planning, ATC services, and weather prior to this lesson will increase the material comprehension.

What is IFR? What is VFR? Why is one better than the other? Which one is better? The answer is not pat, although it can be simple. Sometimes it is the operation you are flying that will dictate which rules you fly under and sometimes it's the airspace or weather you will be flying through.

IFR - Instrument Flight Rules
Rules that govern flight operations when aircraft may spend some or all of its flight time in IMC (instrument meteorological conditions - clouds) and/or aircraft that will stay within controlled airspace under radar control at all times (there are exceptions, of course). Separation of your aircraft from other aircraft, the ground, and objects (i.e., radio towers) is the responsibility of air traffic control.

VFR - Visual Flight Rules
Rules that govern flight operations when an aircraft will spend NONE of its flight time in IMC. The aircraft may be inside controlled or uncontrolled airspace and may or may not have radar coverage. Separation of your aircraft from everything else is the responsibility of the pilot at all times, even when radar identified.

The ATC System
The entire ATC system was built for IFR traffic. If all the traffic worldwide were IFR there would be no need for airspace definitions and weather minimums; they exist primarily so VFR aircraft will be able to safely co-mingle with IFR traffic. But what fun is that? Free flight through canyons and over great terrain is some of the best flying anywhere; someday MSFS's scenery may be up to it. The point here is IFR flights fit very easily into the ATC system. 

VFR also fits, but not without a little more work and sometimes a bigger hassle, like getting a VFR tour of a city while they find a slot to get you into the landing pattern on a busy day. On the other hand, VFR flights don't have to wait for clearances before taking off at uncontrolled airports and clearances out of towered airports can be much faster than IFR flights waiting for their release. VFR can also get into a traffic pattern and land quicker in some cases, while IFR traffic is on 6-8 NM final approaches. Some airports even run some runways preferentially for VFR traffic to separate it from incoming IFR traffic and keep the flow up.

Weather is a large reason to choose IFR over VFR. By VFR rules you may not enter a cloud of any type, nor in air with visibility of less than 3 or 5 NM (depends on airspace and altitude (is this true worldwide?)). In fact in many cases you may not get within hundreds of feet of clouds. VFR pilots fly around clouds of all types; under, over, or around. Under and around means bumpy air, but sometimes over is too tall. Hit a wall of clouds all the way to the ground and you must turn around and divert to an airport that is not blocked by clouds. 

IFR allows you to fly into any weather suitable for the aircraft and pilot. Nobody flies through thunderstorms or tornadoes, and only special aircraft fly through hurricanes and typhoons. If flying into known or predicted icing you must be flying an aircraft with appropriate deicing equipment. If flying to the very minimums of IFR, decision heights below 200 ft AGL, the aircraft and pilots must be certified for Category II, III or IIIA operations which includes multiple altimeters, flight directors, and radar altimeters.

ILS Categories I, II, IIIA, IIIB, IIIC and associated minima:
Cat I - 200ft, 800M 
Cat II - 100ft 400M
Cat IIIA - 50ft, 200M
Cat IIIB - 20ft, 100M
Cat IIIC - 0ft, 0M

In the U.K. the categories and minima are:
Cat I - 200ft, 550m
Cat II - 100ft, 300m
Cat IIIa - 50 to 100ft, 200m
Cat IIIb - <50ft, 75m

Safety and insurance companies dictate that scheduled flight operations with passengers always file and fly IFR. Most large jet aircraft also always file and fly IFR, most of the time. Charters and fractionals can go either way, usually dictated by insurance and usually IFR. Smaller General Aviation jets and props have the choice of choosing IFR or VFR depending on weather, terrain, and airspace ahead of them. Flying into large, busy airports is almost always easier when flying IFR while getting into the airport and landing is much quicker for a VFR flight at small non-controlled airports. Military aircraft fly visually quite a bit, but have learned over the years how to integrate their VFR training and patrol operations into the ATC system to help them get into and out of their bases. Helicopters can be flown in IFR but they like to fly visually as much as possible as that uses the helicopter's strengths the best.

If you're flying a J-3 Cub or a Luscombe with no lights or radios, then you are going to be flying strictly VFR. IFR requires two-way radio communications, a transponder, and navigation equipment, at least one VOR, is considered mandatory for most airspace. Modern GPS and FMS equipment is designed to operate within the IFR environment.

Terrain and Borders
Sometimes the terrain you plan to cross will help you to decide which type of flight to plan. Some small GA single engine piston airplanes can't make the minimum enroute altitudes over mountainous terrain so they must pick their way through the peaks or go around. Also, being in radar and radio contact with ATC means that should you lose an engine and have to make a forced landing, you get SAR help much quicker. Crossing international borders will for sure require a filed flight plan and sometimes VFR flights might be restricted from a border crossing.

Choosing IFR or VFR comes down to assessing the weather and air traffic environment. There are only a few wrong answers, like flying VFR in pouring rain and lightening.

1. Look at the airport pairs below. Decide if the flight should be conducted using VFR or IFR.


2. Look at the METARs below. Decide if a take off or landing at this airport should be under IFR or VFR conditions:

a. EGLL 150250Z AUTO 25008KT 9999 OVC009 08/06 Q1015
b. EGLF 142050Z 23005KT CAVOK 06/05 Q1020
c. LIPC 150355Z 27003KT 1800 BR SCT007 SCT019 10/10 Q1020 RMK OVC WIND THR12 29003KT YLO