Instruments of IFR

When the weather doesn’t make it possible or you’re flying at night, it is not safe to fly according to the visual flight rules (VFR). It is the time when you need to follow the instrument flight rules (IFR). It requires you to have a very good understanding of what’s going on in the cockpit with those aviation instruments.

ADF (Automatic Direction Finder)

When the NDB (non-directional beacon) sends an omni-directional signal, the ADF receives it and the pilot is able to find out the NDB’s relative direction to the aircraft. If ADF indicates 0°, it means that your direction lines up with the station itself. However, it doesn’t tell if you are going towards or away from the station. Therefore, there is another antenna that is used by the ADF to tell if you’re approaching or leaving the station.

RMI (Radio Magnetic Indicator)

It is one of the most useful instruments in the plane. It uses indications from a magnetic compass, VOR as well as ADF and shows them on one instrument. You can always tell where you are compared to the VOR and ADF transmission station.
We can distinguish low, high and terminal VOR depending on the height and coverage. Low-altitude VOR can be used up to 18,000 feet and 40 nautical miles, while high-altitude VOR goes up to 60,000 feet and 130 nautical miles wide. Last but not least, terminal VOR can go up to 12,000 feet and 25 nautical miles.

ILS (Instrument Landing System)

This instrument shows you both the horizontal and vertical guidance when you are about to land. It uses two radio beams that will define the state of the plane in both directions.  It sometimes has marker beacons and high intensity runway lights in order to help you land more precisely.
Since it gets information from both the LOC and GS signals, it is important that both works. You can use it with LOC only, however, it will support a non-precision approach in that case. So, keep in mind that you need both LOC and GS for a precision approach.

HSI (Horizontal Situation Indicator)

The main reason of using HSI is to reduce some of the work of the VOR and ILS. It combines the functions of the magnetic compass, the VOR-CDI and the ILS instruments. It is a very tricky instrument since it provides comprehensive information to the pilot.
So, from this one instrument, you are able to tell the aircraft’s magnetic heading. In addition, you can see the position of the selected radial relative to the aircraft’s current position. Usually a dotted scale shows the deviation from the course. Furthermore, ADF needle is also shown with a glide slope indicator and scale for ILS approaches.
If you want to play around with these instruments and see how they work, go to the App Store and try out our apps!