How old is the non-directional beacon (NDB) as an aeronautical navigation aid? Eighty years? 90 years? Or maybe more. I’m not sure. The NDB was certainly around before even the fancy four-course range with its dit-dah left-right guidance along a “beam.” But the four-course range died decades ago while the NDB lives on. What’s up with that?
In most countries other than theU.S.an ADF receiver capable of navigating using NDB signals is still a requirement for IFR flight. Newly designed mega million dollar airplanes are still leaving the factory with an ADF receiver, or more often two of them. That’s like including an Underwood manual typewriter along with every new iPad sold.
But the NDB and ADF live on because of politics, not technology. The “G” in GPS stands for global, and the GPS signals cover the world with excellent accuracy everywhere, not just over the U.S. But GPS is controlled by the U.S. military and that’s why many – even most – nations in the world are still using NDB signals because the NDB transmitter is bolted firmly to the ground in each country.
There is more than the “not invented here” syndrome at work causing many countries to reject GPS for primary IFR navigation, particularly for IFR approaches. It is theU.S.that set the ball rolling when GPS was initially developed.
The original name of GPS was Navstar and it was totally a military project and was created by funds from the military budget. When the first test satellites were being launched in the mid-1970s the U.S. Air Force was very clear that its worldwide navigation system was first and foremost a military weapon.
The Air Force did relent a little by making an intentionally degraded GPS signal available to the public, including pilots, but made it clear that even that lower level of service could be turned off at any time without warning if the military believed there was a valid reason to do so. The Air Force definitely didn’t want any civilian pilots using GPS for primary navigation, much less for IFR approaches flying close to the terrain in the clouds.
The FAA obliged the Air Force and ignored GPS in its plans for the future. The FAA and European aviation authorities invested millions in a squabble over a microwave landing system (MLS) technology that would guide pilots along curved approaches in three or four dimensions. The Europeans wanted to use a Doppler technique for MLS, but the FAA and its industry supporters demanded a time-reference scanning beam (TRSB) technology. The FAA won the fight, but only a handful of MLS systems were ever installed anywhere. Why do I remember this stuff when I can’t remember what I ate for lunch?
Anyway, the civilians in the federal government saw the waste in reserving GPS only for military use when all taxpayers had chipped in to build it. The government changed the policy and assured civilians that GPS signals would be available, and that the accuracy would not be intentionally degraded. The FAA was ordered onboard and GPS became a foundation for the Nextgen modernized air traffic system.
But the rest of the world wasn’t so quick to accept the 180-degree turn by the U.S. government. After all, if theU.S.could reverse its policy on GPS availability once, it could do it again. So most of the world’s aviation authorities simply refused to certify GPS for IFR guidance, particularly approaches. Without GPS all that’s left in remote areas or in rugged terrain where an ILS is not feasible is the NDB approach.
The anti-GPS attitude is changing slowly because other nations are launching their own compatible satellite navigation constellations. Europe has its Galileo satellites and the Russians have GLONASS, and I’m sure there are other efforts I have lost track of. It’s not really crucial that these additional satellite nav systems add any capability or redundancy to GPS. What’s really important is that the rest of the world feel a part of GPS and have an ownership stake so they will not be victims of a whim of theU.S.
So the NDB and ADF live on because many national aviation authorities don’t trust the U.S. government, not that they don’t trust the technology of GPS. My ADF receiver is long gone and I sure don’t miss it.