September 1, 2011
By Thomas A. Horne & Dave Hirschman
Editor at Large Tom Horne and Senior Editor Dave Hirschman have a lot of things in common: lots of ratings, lots of experience in lots of airplane models—and lots of opinions (as well as similar haircuts). We last turned them loose on the topic of production and Experimental aircraft (see “Dogfight: Experimental Versus Standard,” September 2011 AOPA Pilot) and the response to two different schools of thought on this topic garnered interesting opinions from a large number of readers (see “Letters”). So we launch them into another “Dogfight”—we hope you’ll enjoy these two takes on a topic, and keep those cards and letters coming. —Ed.
By Thomas A. Horne >
While I’ve never been a big fan of flying automatic direction finding (ADF) approaches, holds, and other procedures, I had to come to terms with them during my instrument training. Eventually, I became fairly good at flying the heading-adjustment procedures necessary to make good a track. Learning was difficult, but certainly rewarding. And I picked up a skill set that has served me well.
Lately, the trend has been to do away with ADF approaches (sometimes called NDB approaches, for the non-directional beacon stations that put out the signals). Oh, joy, I hear so many say. No more mental math to come up with proper headings! No more memorizing MH (magnetic heading) plus RB (relative bearing) equals MB (magnetic bearing) to the station! No more flying the least precise of the nonprecision approaches! No more stressful inflight quandaries about the quality of your track!
Believe me, I understand those feelings. But there are several very important reasons for obtaining and maintaining ADF skills. Yes, yes, I know that if the airplane you use for passing an instrument rating checkride isn’t equipped with an ADF you needn’t demonstrate ADF skills. But that’s a pretty weak reason for not building a complete set of navigation abilities.
Believe it or not, some airplanes are still delivered with ADF equipment fresh from the factory. Thousands more ADFs are in the total aircraft fleet. Some day you may find yourself behind the wheel of an airplane with a navigation system that you’re unable to safely use.
But there are fewer ADF approaches these days, I hear you say, and GPS overlays obviate the need for NDB tracking. Yes and no. At some smaller community airports an ADF approach (sorry, without GPS overlays) either to or from the NDB station remains the only way to make an instrument arrival. Ever plan on flying to Canada, the Caribbean, or overseas? Then you’d better know how to track NDB bearings. In many parts of the world there are even NDB airways. Care to accept a clearance to track a low-frequency airway to an airport served by an NDB-DME approach? You’d better, if you want to qualify to fly outside the U.S.
Why would you knowingly want to do away with a second source of navigation information?
Redundancy is another good reason for having an ADF in the cockpit. To those who cheer the NDB’s (apparent) demise, I have a question: Why would you knowingly want to do away with a second source of navigation information? It may come in very, very handy one day. GPS outages do occur. Emergencies do happen, and a quick landing at the nearest airport—served, you guessed it, by a sole NDB—may be the only option. It’s happened to me.
Last but not least is the vital issue of situational awareness. Sure, seeing your position on a huge GPS display screen is hard to beat. Unless your airplane doesn’t have one; or unless you’re cleared to hold at an NDB; or unless you’re told to intercept and track an NDB bearing; or unless you’re attempting to ascertain your position in a nonradar environment with no access to GPS information. ADF skills give you the kind of basic visualization, tracking, and orientation aptitudes that have staying power. And it’s not that difficult to learn; if you can become proficient understanding the use of VOR cross-bearings for position finding, then you can become a whiz at using an ADF for position fixing. A slaved radio magnetic indicator (RMI) makes this chore even easier because the compass card shows the airplane’s current heading, as well as real-time compass bearings to NDBs or VORs.
So are ADFs useless, and the skills to use them as arcane as those used in operating an abacus? I think not. Knowing how to use an ADF is the sign of a pilot with a well-rounded education. Too bad virtually all aircraft manufacturers no longer offer them, or if they do it’s as optional equipment.
Email the author at [email protected].
< By Dave Hirschman
Tough times require hard choices—although the decision to ditch NDB approaches shouldn’t be all that difficult. It costs the FAA about $20,000 a year to retain each NDB approach in the United States. Mercifully, more than 250 have been decommissioned since 2005, and additional savings are available by disposing of the 907 such antiquated approaches still on the books. And even though those of us who learned to fly IFR by chasing the heads and tails of NDB needles may wax poetic about them and boast of our prowess, NDBs are indisputably the least precise of all nonprecision approaches.
Most U.S. aircraft owners have long since chucked their obsolete, electron-wasting, panel-space-hogging, antique ADF receivers and ice-collecting, drag-inducing, clothesline antennas in favor of more useful and modern navigation equipment. (Those who haven’t are more likely to tune their ADFs to AM radio stations than actual NDBs.) The FAA should be encouraged to rid itself of its outmoded and expensive NDB network and accelerate the addition of newer approaches that offer greater safety, utility, and far lower minimums than NDBs ever could. (There are 5,117 RNAV approaches now, and more are being added each charting cycle.)
In a recent survey, about half of all U.S.-based ATPs reported having flown no NDB approaches at all in the preceding year. Clearly, that’s not enough for broad proficiency, and practice NDB approaches are sure to become harder to find as their numbers dwindle. In 1996, a U.S. Air Force crew tragically bungled an NDB approach in Croatia and struck a mountainside, killing Commerce Secretary Ron Brown and 34 others—an accident that likely wouldn’t have happened if a more accurate form of navigation had been available.
Overseas, most aviation agencies get the message, and NDBs are on the way out. Should Americans cling to an outmoded technology on the slim chance we might encounter it as a secondary system in some remote corner of the globe? No way.
Most NDBs in the United States are compass locators that help identify the outer markers on ILS and localizer approaches, but even these are disappearing, and few pilots notice, or miss compass locators, when they’re gone.
NDBs have been around for more than 70 years, and their shortcomings are well known and numerous. Atmospheric conditions radically alter reception range. Coastal refraction distorts signals, and thunderstorms can cause ADF needles to swing wildly, often pointing to the electrical storms themselves. (The German and Japanese militaries during World War II sometimes transmitted false NDB signals to draw allied fliers off course.)
We shouldn't waste precious resources on outmoded, anachronistic systems, and that's what NDBs are today.
Some pilots argue against giving up any redundancy in our IFR system. That sounds reasonable, but the same logic would have required preserving airway beacons, radio ranges, and loran forever. Does anyone really want to go back to deciphering scratchy dits-dahs while trying to find a runway on a rainy night?
Learning to fly NDB approaches, especially in crosswinds, is fun and challenging. It requires a refined instrument scan and interpolation, and it brings great satisfaction to those who master the arcane practice. But at a time of declining FAA budgets and uncertain future funding, we shouldn’t waste precious resources on outmoded, anachronistic systems, and that’s what NDBs are today.
They aren’t a primary or even a secondary navigational source for cross-country flying, and they’re not a primary or secondary system for nonprecision approaches. Rather than putting them on costly and indefinite life support, we should decisively end them. Thankfully, almost all have already been replaced (or “overlayed,” in FAA parlance) with newer, more accurate approaches that better match aircraft avionics and provide lower approach minima.
Most of the U.S. GA fleet, and especially the training fleet, abandoned ADFs, loop antennas, and RMIs long ago. Applying the savings to more useful and accurate navigation systems that allow GA pilots to fly to more runways with greater precision, safety, and confidence makes sense. The NDB system has outlived its usefulness. It’s time—past time—to leave it behind.
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