Radar to the Rescue

Taught briefly during pursuit of the instrument rating, three very important radar approaches are often quickly forgotten. These are the ASR (airport surveillance radar), PAR (precision approach radar), and no-gyro approaches. Even worse, only rarely does an instrument pilot ever practice these approaches once he's earned the rating.

It's too bad, because these approaches can be a pilot's very best friends when vacuum pumps fail, heading indicators or slaved compasses give up the ghost, or navigation equipment decides to take some time off. If you're stuck in the soup, face a descent into low ceilings and visibilities, and have one or more of these problems, one of those radar approaches may be your only shot at any semblance of a safe instrument approach.

Right up front, it's very important to understand that these approaches can't be flown to just any airport. You have to fly in an appropriate radar environment. It's only certain larger airports, those equipped with properly certified surveillance radar, that can provide ASR and no-gyro approaches. These radars, which typically have effective ranges of 40 to 60 nautical miles, meet terminal area specifications that make them usable for both plain-vanilla radar vectors used in everyday terminal operations, as well as for pure radar approaches. PAR approaches require much more sophisticated radars that can scan in both azimuth and elevation.

The ASR approach, also called simply a "surveillance approach," is designed to provide pilots with heading information. This is helpful in cases where your navigation equipment has failed but you still have an operable heading indicator.

In such cases, controllers will give you headings to fly. The objective is to position the airplane along the extended centerline of the runway you'll be landing on. In this sense, flying an ASR approach is a lot like receiving vectors — something we're all pretty much familiar with anyway. Truth to tell, ASR approaches are not only for emergencies. They can be issued to routine arrivals as part of a traffic management strategy.

The ASR is not really meant to provide very precise altitude information, but controllers will let you know certain recommended altitudes. For instance, you'll be told the minimum descent altitude (MDA) for the approach, when to begin a descent to the MDA, and the altitudes of any crossing or step-down fixes.

Once on final, you can also be told your range from the runway (in nautical miles), provided you ask for it. Another on-demand service available from controllers is issuance of recommended altitudes for each one-mile segment along the final approach course. So, while the ASR approach is not specifically designed for vertical navigation, you can, if you ask for it, have the peace of mind that comes from knowing that you're flying not just a safe heading, but a safe descent profile, as well.

One caveat: Because of airport surveillance radar limitations, the MDAs posted for ASR approaches can often be higher than those ordinarily published for other, nonradar instrument approaches. You can appreciate any difference in minimums by checking the instrument approach procedures for those airports that publish ASR approach information.

Jeppesen approach plates use a dedicated page, titled "Radar," for ASR approach information. Also depicted are navaid and voice frequencies, final approach courses, missed approach procedures, and obstacle data. Government approach books list radar minimums in the front of each approach book.

Take a look at Charleston, West Virginia's Yeager Airport approach plates for a moment. The ASR MDA for Charleston's Runway 23 is 1,500 feet, or 569 feet above the airport. That's far above the ILS Runway 23's decision height of 1,181 feet, which is 250 feet above the runway.

Controllers will continue to give heading and altitude guidance right up to the missed approach point. At that point, you either announce that you have the runway in sight or fly the missed approach procedure. In the former case, guidance is terminated and you land. In the latter, it's time for more vectors — perhaps for another try, or perhaps to an airport with better weather.

No-gyro approaches are tailor-made for those times when the gyro-driven heading indicator is kaput, you've lost your source(s) of vacuum or pressure to drive your heading instruments, or your slaving system (if so equipped) has thrown your slaved compass out of whack.

First things first. Cover up the heading indicator, then ask a controller for help. If you have the fuel, time, and opportunity, a good plan is to ask for no-gyro vectors to an airport that's experiencing good visual meteorological conditions. If you're short on fuel, then you'll want to ask for a no-gyro approach to an airport closer by.

With no-gyro approaches, you don't have to worry about flying headings. Controllers will tell you to "turn right" (or left) and then to "stop turn" when you reach the desired heading. All you do is follow instructions and make all turns at standard rate.

That, and keep the airplane under control. It bears repeating: Cover up the malfunctioning heading indicator — and leave it covered. It's an all-too-natural temptation to fixate on it, even though you know its information is no good. Many pilots have died after following a dead gyro instrument's false cues right into the ground.

The idea is for the controller to "turn...stop turn" you until the airplane intercepts the extended runway centerline. Altitude information can be provided much the same way as it's provided with ASR approaches.

Once established on a final approach course, you'll continue hearing the "turn...stop turn" litany, but more often. This marks the fine-tuning of your inbound heading. Make all turns at half standard rate, lest you "stitch up" the final approach course or wander too far away from the prescribed ground track — in which case the controller may well call for a missed approach and have you "turn...stop turn" all the way around the airport for another try.

Once you arrive at the MAP, the no-gyro approach ends either with the runway in sight or a missed approach — again, with "turn...stop turn" vectors.

PARs are for the direst of predicaments. Just to play what-if, let's say you're on instruments and you've lost power, or you suspect a fire, or a passenger goes into convulsions, and the whole time the surface weather suddenly goes zero-zero. It's a nerve-wracking, confusing time, and you need all the concentration you can muster just to fly the airplane. You need to get on the ground — and fast.

Of all the radar approaches, the PAR does the most to lighten pilot workload. Controllers will lead you by the hand, giving such precise altitude and heading guidance that landings in zero-zero weather conditions can, and have been, successfully performed.

After establishing communications, a controller will usually remain on the same frequency for the duration of the approach. He or she will guide you to a final approach course, then tell you when glide slope intercept is 10 to 30 seconds away. At this point, the controller will go into a rapid-fire monologue. You'll be told if you deviate from either the final approach course or the glide slope, and you'll also be advised of the effect of any course or altitude corrections you may make. In short, the controller becomes a sort of verbal course deviation and glide slope indicator.

The advice will be constant, coming at intervals of no more than five seconds. In fact, as part of the preliminary information given by the controller, you'll be told that if nothing is heard for five seconds while on the final approach course, a missed approach will be required. That's how closely controlled a PAR is.

The terms "slightly" and "well" will be used to advise you of your orientation with regard to the precision approach path. The terms "rapidly" and "slowly" are the phrases for trend information.

The banter would sound something like this: "November-Seven- Two-Three-Six-Whiskey, you're on course and on glide path.... Now you're drifting slightly left of course and slightly above glide path.... Now you're left of course and holding.... You're slightly above the glide path and slowly coming down.... Left of course and correcting rapidly.... Below glide path and coming up.... Slowly.... "

Range from the touchdown zone is issued at least once every mile, so you remain constantly apprised of range, bearing, and altitude. (As for the decision height, controllers won't offer that bit of information unless you ask).

You get the idea. The approach follows what many nonpilots believe to be a routine instrument approach — as gleaned from bad Hollywood movies, that is. The controller manages the pilot, and leads him right to the decision height. And, if necessary, right to the runway.

If the ceiling and visibility are low enough, the PAR controller will tell you when you're over the runway threshold — all the time still providing course and glide path guidance. Once past decision height and the runway threshold, controllers will still give heading guidance relative to the runway centerline. Once you announce your landing, however, radar service will be automatically terminated.

Now you may face a new predicament. If your approach was to an airport experiencing WOXOF (indefinite ceiling zero, sky obscured, visibility zero in fog) conditions, you're left sitting on the runway. The visibility is so bad that you can't even taxi safely. Now's the time to call for the "follow me" truck — and to prepare for another potential problem. The truck has to be driven very carefully, lest its driver plow into the airplane. It sounds funny, but more than one "follow me" truck has driven into an airplane idling in the fog. Imagine a safe approach to a landing in zero-zero weather, only to be T-boned on the runway by a well-meaning lineman.

Flying these radar approaches may sound simple. You just follow directions and land at the end of the procedures, right? But remember: Serious malfunctions precipitate these approaches. The distraction factor will be high, and so will pilot workload and con centration. Unless you've been practicing them, radar approaches themselves can be vexing — let alone coping with any preexisting emergencies. The moral: Practice radar approaches.

As suggested earlier, this may be a problem for many pilots. Radar approaches are available at only a few airports. A look at the front portion of a National Ocean Service approach plate book will show you just how few. Radar equipment and radar coverage must meet strict standards in order to guarantee the kind of accurate coverage that these approaches demand. And relatively few airports can meet the requirements.

With PARs, the choice of airports is narrower still. PARs are a favored approach of the military, so if you need one, plan to seek out the nearest Air Force or Navy facility. You can try asking for practice PAR approaches at military airports, but a granting of the request might not always be forthcoming.

Despite problems with availability, it makes sense to aggressively seek out those airports that both provide these services and are amenable to granting practice approaches. You could easily be surprised. Controllers, like pilots, must also practice to stay current. A controller who hasn't logged any radar approaches in a while may jump at the chance to knock off the rust and stay legal.

In a pinch, these approaches can save your life — and those of your passengers. It's just plain irresponsible to neglect them. The last thing you need is to become reacquainted during an actual emergency.