John Peltier

When was the last time you checked your VOR receiver? As an IFR pilot, how often are you required to do this test? What about as a VFR pilot? Are you required to check your VOR receiver?

The answer for VFR pilots is, well, no you’re not required to check your VOR receiver. That doesn’t mean that it’s not a good idea.

And for IFR pilots, how often do the Federal Aviation Regulations say you must check your receiver when using it for instrument flying?

According to FAR 91.171, you may not conduct an IFR flight using VORs for navigation unless your VOR system has been checked within the preceding 30 days and found to be in limits. The check must also be logged in the aircraft records.

Fortunately, these are checks that pilots can accomplish on their own, and in many different ways.

The FAA allows pilots a handful of different methods for checking VOR receivers. There’s an easy acronym to remember about these tests, including tolerances – do you know it?

The acronym most taught to IFR students is VODGA. This stands for VOT, Ownship, Dual, Ground, Air. Let’s take a closer look at the steps to check your VOR receiver using this acronym.

VOT

The VOR Test Facility (VOT) is the most accurate and is the preference to check your VOR receiver. Not all airports have a VOT. You can discover which airports do have a test facility in Section 4 of the FAA Chart Supplement (formerly known as the Airport Facility Directory [AFD]). The supplement indicates which airports have the test equipment, which frequency to use, and any other notes specific to that location.

Steps to using the VOT:

1. Ensure you are situated on the airport in an appropriate area – the parking apron, taxiway, or end of runway. The Supplement will make note of which areas on the airport will not work.
2. Tune to the appropriate frequency annotated in the Supplement.
3. Turn up the volume to identify the station, which is indicated by a series of dots or one continuous tone.
4. Twist the OBS to center the needle. The TO/FROM flag should indicate TO with 180 degrees (+/- 4) selected. Remember: Cessna 182. One-eighty two, or 180-TO. It should show FROM with 360 selected.
5. The tolerance must be within four degrees, i.e. the needle must be centered when the OBS is from 176 to 184 degrees or 356 to 004 degrees.

In the absence of a VOT, you may use other checkpoints designated in the Supplement. These are the ownship tests, and they may be conducted in the air or on the ground.

Ownship

Checking your VOR receiver may be done at either a designated location on certain airfields or over specific geographic locations while airborne. These locations, frequencies, and notations may also be found in Section 4 of the FAA Chart Supplement. The Supplement will provide the name of the VOR and/or airport facility, the frequency, and whether or not it is a ground or airborne checkpoint. If it’s an airborne checkpoint, minimum altitudes will also normally be listed. If it’s a ground checkpoint, the location on the airfield to perform the test will be listed.

Ground checks are preferred over air checks because it’s easier to position your aircraft to a more precise location on the ground.

Steps to doing an ownship location VOR receiver check:

1. Tune to the appropriate frequency annotated in the supplement.
2. Identify the station by turning up the volume and ensure the Morse code or voice identifier is correct.
3. Twist the OBS knob to the azimuth listed in the Supplement.
4. Position your aircraft at the appropriate location annotated in the Supplement, either on the ground or over a geographic location in the air, ensuring you’re at an appropriate altitude if airborne.
5. If the needle is not centered, twist the OBS until it centers up.
6. The tolerance must be within four degrees for ground checkpoints or six degrees for air checkpoints. So if an airborne checkpoint azimuth is listed as being 177 degrees, the OBS must be centered in a range from 171 to 183 degrees.

You may also make your own airborne check by looking at the charts and picking a significant geographic landmark under a VOR airway. Fly over the landmark and note the azimuth that your aircraft VOR receiver indicates. It should be within 6 degrees of the annotated airway azimuth.

The FAA allows for one more method of checking a VOR receiver, and you may do this if you have two separate receivers in your aircraft (they can share an antenna).

Dual Receiver Check

A dual receiver check is valid if you have two separate receiver units in your aircraft. They can have a common antenna but the actual receivers must be separate. These checks can be done on the ground or airborne.

Steps to conducting a dual receiver VOR check:

1. Tune both receivers to a nearby VOR station.
2. Identify the station in both receivers by turning up the volume and verifying the Morse code or voice identifier.
3. Compare the OBS settings for both receivers with the needle centered. They must be within four degrees of each other.

Ground / Air

The final pieces of the VODGA acronym, GA, is to remind you that there are different tolerances for ground checks and air checks. It should make sense that ground checks are more accurate, and thus have a lower tolerance for error. All tolerances are 4 degrees, including a dual check in the air. The only exception is the ownship airborne check, which has a tolerance of 6 degrees.

Logging the VOR Receiver Check

This may be the most neglected part of the VOR checks, and if the check is not logged you are in violation of the FARs. Doing the actual checks is important! But so is logging them.

Logging the check is easy. It doesn’t even have to be in official aircraft maintenance logs, it just needs to be with the aircraft and available for inspection. A simple spreadsheet will suffice.

The log must contain the date, location, bearing error, and signature of the pilot conducting the check.

Summing Up the VOR Receiver Check

If you’re an IFR pilot using VORs for navigation, you must check your VOR receiver within 30 days preceding an IFR flight, and log the check.

You may check two receivers against each other if your aircraft has two separate units. This will be the easiest if you have two units. Tolerance is 4 degrees.

You can also check your receiver while on the ground at certain airports using a dedicated VOR test facility or a designated VOR ground checkpoint, both found in the FAA Chart Supplement. Tolerance is 4 degrees.

In the absence of any other way to check your VOR, you may conduct a check airborne. The tolerance is 6 degrees.

The checks must be logged with the date, location, bearing error, and signature.

These regulations are found in FAR 91.171. More information can be found in AIM 1-1-4. But most importantly, don’t forget to keep current with these checks, and log them.

Get Started With Your Flight Training Today

You can get started today by filling out our online application. If you would like more information, you can call us at (844) 435-9338, or click here to start a live chat with us.

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Dr. Mary Ann O’Grady

Any pilot who has been flying for a while has experienced flights delays due to weather conditions, and without having an instrument rating, those delays can stretch into hours or even into days. These delays can cause many pilots to make go no-go decisions that are not so good. So the benefit of a pilot having an instrument rating is that it increases the number of good choices available to him or her. Although most pilots eventually earn an instrument rating, a smaller number of them maintain instrument currency, so when a student is contemplating IFR flight training, it is best to know in advance what kind of instrument pilot he or she intends to be. If the goal is to be an instrument pilot in name only, then all the IFR flight training needs is to accomplish is passing the check ride. However, if the student wants to be an active instrument pilot rather than a victim of the risks, it is necessary to progress well beyond the basic IFR flight training requirements. Instrument flying is demanding and it requires active thinking, because when a pilot earns an instrument rating he or she is authorized to evaluate weather, dispatch the flight, and then fly the airplane within the same air traffic control system and weather systems that the two-crew turbine aircraft are using.

In essence, weather and VFR flying is a relatively simple and straight-forward [black and white] process which involves flying visually while avoiding the clouds and areas of poor visibility. However, weather for IFR flying enters into a more gray area which involves actually flying in the weather rather than flying to avoid the weather. This makes knowledge about the weather that much more significant. It is critical that students learn as much about the weather as they do about the elements or mechanics of instrument flying. Those pilots who believe that they can be fed weather data for IFR flights by an FSS are the pilots who typically find themselves in trouble due to unanticipated or deteriorating weather conditions. Passing the FAA’s knowledge test does not provide a pilot with sufficient [theoretical] knowledge on weather, which is why it is imperative that students find a flight instructor who is willing to fly in actual conditions on training flights. This will help to acquire the practical experience that will allow student pilots to understand the correlation between the information provided by a weather briefing and the actual weather conditions.

One means of examining the potential value of an instrument rating is to fly hypothetical flights by checking the weather to see if a trip could be flown in VFR conditions. If the answer is “no,” then examine the weather for a hypothetical IRF flight between the two points. There are several elements of weather than impact IFR flights: clouds, ice, turbulence, precipitation, convection, fog, low ceilings, low visibilities, and winds aloft so that only through study and actual practical experience can students learn to weigh each of these elements that could affect their flying. The FAA allows pilots to earn an instrument rating with 125 hours of flight time, which might be sufficient for full-time students who are pursuing positions as airline first officers. But for pilots who want to be able to fly single-pilot IFR in light airplanes, those FAA requirements tend to be inadequate.

Summary of the FAA requirements for an IFR Rating

Pre-Flight Review: Review all information and goals associated with the upcoming flight as well as how to achieve them whether in actual or simulated IMC (Instrument Meteorological Conditions), such as WFKART: weather, fuel requirements, know ATC delays, alternates, runway lengths, and takeoff and landing distances. If the flight planning includes shooting some approaches, it becomes necessary to brief those approaches and the missed approaches several times before the flight.

Ground School: This is the most cost-effective environment in which to ask questions of the flight instructor which can assume multiple formats, such as one-on-one dialogues, group classes, videos, or interactive DVDs or a combination thereof. To maximize learning within the shortest period of time, it is important to combine the ground school [theoretical] concurrently with the [practical] flight training.

Hood Work: Provides practical experience when no clouds are available. Hoods assume many shapes and sizes, and they are a regular part of the instrument training to block the students’ view of the horizon which only allows them to see the instruments on the flight deck. The purpose of the hood is to expose students to the forces of flight which can lead to various types of disorientation so that the experience teaches students to deny their body sensations and only trust the instruments on the flight deck.

Instrument Cross-Country: Most of the IFR flight training will typically occur near the students’ home airport, but the cross-country phase of the training will take the students out of the familiar which is when flight planning really begins to pay off. The pre-flight review allows the students to remain ahead of the airplane and enjoy the arrival at the pre-determined destination without having looked out the window. Attempting this in a vehicle is not recommended….

Check Ride Preparation: Once all of the ground school and flight time requirements have been met, the flight instructor will provide the students with a ground review which is when the students have the opportunity to demonstrate their knowledge of the instruments and how they function as well as how they fail. The students must also demonstrate a familiarity with the FAA IFR regulations and how the system functions which is followed by a simulated check ride with the instructor. During this lesson, the students must adequately perform all flight procedures, maneuvers, and a number of instrument approaches to progress onto the next step of the process.

Instrument Rating Practical Test: This exam encompasses all the aeronautical information that the students have learned up to this point, and the students have the option to ride with a Designated Pilot Examiner or an FAA Inspector.

Once the students have passed the check ride, they are issued an instrument rating and are now allowed to file and fly in IMC. This allows the pilot to have a greater degree of freedom and feeling of self-confidence.

Get Started With Your Flight Training Today

You can get started today by filling out our online application. If you would like more information, you can call us at (844) 435-9338, or click here to start a live chat with us.

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