Pilots flying in poor conditions where the human eye is obstructed will need the help of flight instruments to navigate the slides safely; however, this day and age, VOR isn’t strictly necessary.
Unlike VFR (Visual Flight Rules) that stipulate that if conditions are clear to a set standard, you can navigate simply by relying on visual geographical cues such as buildings and landmarks, flying in accordance with IFR (Instrument Flight Rules) means you’re going to need extra help.
Historically, as detailed by federal aviation regulation 14CFR 91.205(d), VOR was an essential part of the navigation system of aircraft in IFR conditions.
The high radio frequencies pinging between fixed-ground radio beacons and the aircraft allowed pilots to determine position in the air and to stay on course with little to no visual cues.
As VOR was and still is so heavily relied upon, a VOR operational check within 30 days before the scheduled flight is also mandatory procedure.
Fast-forward to present day, GPS has come on leaps and bounds. It’s no longer just a so-so tool we keep in our cars that periodically gets us more lost than we ever could have gotten going it alone.
It’s a highly refined technology that can highlight not just aircraft location, but give a detailed read of the environment.
What’s more, it doesn’t rely on localized sources of radio signals, meaning you can venture further from the station, and you don’t have to worry about flying blind due to accidentally traveling out of range.
In light of this, GPS became the primary flying aid of the majority of aircraft operators. Consequently, the federal aviation regulations were altered to suit the new age of air navigation.
This recognition of the new technologies can be found under the very same CFR 91.205 regulation that ruled VRO was mandatory.
It currently states that the minimum equipment required for IFR flight is ‘two-way radio communications systems and navigational equipment suitable for the route to be flown’.
So, being that in many scenarios, pilots are no longer relying solely on VRO technology, as long as you have an adequate alternative on board, you’re good to go!
That's not to say VRO is defunct by any means. On the contrary, VRO is still seen as the standard aviation navigational tool on a global scale. As such, many aviators do still use them and still have to complete the appropriate VRO operational checks before liftoff.
Can You Fly IFR Without VOR?
As we’ve touched upon already, no, you don’t necessarily need VOR technology to take a plane up into substandard weather or visual conditions.
You just need a fully functional alternative such as GPS navigation.
Having said that, not all GPS technology is certified as a primary navigational tool. First-generation, non-WAAS GPS units, for instance, are registered under the TSO-c129 umbrella of the federal aviation regulations, meaning they’re not fit to use as a sole navigation system for IFR aviation.
As this was the case, many early Garmin non-WAAS c129 GPS units were built with integrated VOS technology and required the very same preflight operational checks as dedicated VOS systems as stipulated by regulation 14 CFR 91.171.
Modern TSO-c146-certified, WAAS-augmented GPS units, on the other hand, are considered the ideal primary navigational tool when you’re up there cutting cloud.
What makes WAAS GPS so much better than traditional GPS systems? Well, WAAS stands for Wide Area Augmentation System, and it functions in a very similar fashion to VOS, which is largely the reason why it is slowly but surely taking its place.
The basic function of WAAS technology is to use a network of ground-based reference stations (just like VRO) developed in Hawaii and across North America to measure subtle variations in GPS signals.
These signals are sent to a master center which then feeds the corrective data to geostationary WAAS satellites in orbit.
The satellites then ping the signals back down to Earth where it’s picked up by WAAS-enabled GPS systems, amounting to unparalleled locational accuracy.
But just because WAAS-augmented GPS is making waves in aviation, doesn’t mean it’s foolproof.
Modern, high-performance GPS can and will let you down from time to time, not because of internal faults, but due to incidental or intentional radio interference.
By intentional, we don’t mean that some nefarious villain is purposefully tampering with your GPS signal.
It’s just that the U.S. military frequently experiments with test jamming, and if you get caught in that airspace, your GPS will appear to be on the fritz.
As WAAS GPS isn’t completely foolproof, you will need a backup, especially if your flight path leads you a fair way from the airfield, and as far as we’re concerned, VRO is still the best stand-in when your GPS goes haywire.