At various points during my instrument training, my redoubtable primary (and instrument) instructor took me on a number of memorable mini-adventures. There was that DME arc approach into Martin State Airport in Maryland, or my first taste of Warp Five through snow on a night flight from New Jersey, or that time we flew over to Andrews Air Force Base, and down a special chute reserved mostly for the folks in uniform: the Precision Approach Radar.
PAR for the course: This was my lasting introduction to one of three seldom used but critically important types of instrument approaches, all having to do with radar. One of them is admittedly a bit less obscure; most of us have heard of the “no-gyro” approach. You’ve heard of airport surveillance radar, but how many ASR approaches have you ever flown? (The chances are that it isn’t very many.) And then there’s the cream of the crop, the PAR approach. Of those pilots deciding to earn themselves the added feather of an instrument rating, all hear about PAR during their instrument training. I know I did. The difference between these approaches and the other “regular” IFR approaches deserves the telling.
Your ace in the hole: Most instrument pilots know what a no-gyro approach is. It’s used when you’re IMC in widespread low ceilings and visibilities and you find yourself faced with a vacuum pump (or heading indicator perhaps, or your navigation radio) that’s gone Tango Uniform, and you need to get down. They’re only available in areas of radar coverage, and more to the point, only at certain airports. Airport Surveillance Radar is fairly sophisticated and capable of more than just a squawk code and a by-your-leave with the local en route controller, for this type of radar can give you, in addition to the no-gyro variety, the approach called (logically enough) the ASR approach. First, a commercial message…
Flashback: When I went for my oral exam before my instrument check ride, the examiner asked me a difficult question. What would I do in an airplane when there were 200-foot ceilings everywhere, and the temperature-dew point spread was getting smaller? My answer was that I wouldn’t take off in the first place with that kind of widespread moisture and cruddy weather. At first, I thought to myself “Oh jeez that was a cop-out; now I’m gonna get shot down.” However, it turned out that was the right answer, at least for me, at that point, given what I was likely to be flying (single-engine, probably non-complex, and not high-performance any time real soon). That was back in 1992, and my answer hasn’t changed. In fact, I was a bit younger and I’ll be honest, probably a bit bolder but sharper as well, and the older I get, the wider that yellow streak gets — the one down the middle of my back. Still, things can get out of hand even for the best of us I suppose, and it’s just these types of approaches that I want to toot the horn about here.
ASR approaches …are just called “surveillance” approaches, for short. Their purpose is to provide the pilot in need with assistance on his or her heading. This would be perfect in the scenario where someone’s DG still works for instance, but their navigation radios don’t. Here, ATC simply gives you a “progressive” with one heading after another to fly, until you’re lined up with the destination runway (or what’s become your destination runway). It’s really just radar vectors with a nervous tic and a faster beat. In fact, controllers sometimes use a variation of these for TRACON triage, when things get busy.
Look ma, no gyros! Of the three, this is the one you may have heard the most about. This is what to prepare for if you lose your vacuum pump, for example. By the way, the first thing you should always remember to do, should this happen to you, is this: COVER UP THE DEAD DISPLAYS! Whether it is the heading indicator, the artificial horizon, or something else, it’s too easy to be misled, even subconsciously. (If you don’t happen to have the proverbial set of five-and-dime suction cup soap holders in your flight bag, crumple up something else and improvise.) The second thing (or while you’re doing the first) would be of course to declare an emergency, and ask for a no-gyro approach to the nearest place with better weather. If the fuel gremlin is a factor, make it a local. The good news with no gyro approaches is that you’ll have one less thing to keep track of: namely, your headings. Instead, you’ll hear a lot of “turn left” or “turn right” (at the three degrees per second standard rate) and “stop turn” requests. Altitude information is available as mentioned previously. Once they’ve got you on the final approach course, you’ll be expected to perform all your turns at half standard rate. What happens at and after the MAP (missed approach point) is again, pretty much as already described.
The deluxe edition: If things really go the Hell on a sled, the PAR is what you should ask for. The odds are that there is one available at a military airfield within the fuel range of your aircraft. (My Andrews AFB experience of course was before 9-11 and the “freeze” or Flight Restricted Zone around Washington DC, but rest assured, if you have an emergency, and it’s not one of your own making, you’ll have no reason to worry about getting shot down, should you need to traverse regulatory special use airspace.)
Now hear this: a PAR approach can get you down safely (assuming you don’t go into auto-flail mode) when conditions are zero-zero.
In a PAR approach, hand-holding is so unwavering and so precise that this isn’t at all an exaggeration. (You can read something about this in the ATC publication 7110.65P.) In fact, if at any point you do not hear your controller for five or more seconds, it means an immediate missed approach; that’s how carefully controlled these things are. You will be constantly updated as to your position relative to “on course, on glide path” with a series of advisory terms which, while not quantified in terms of degrees or distance, nonetheless provide position and trend information. (“Slightly left”, “slightly above”, or “correcting slowly” are the sorts of things you might hear.) They also tell you your range from touchdown every mile, and if things have really gotten scuzzy, they can tell you when you’re over the runway threshold. Your worst problem might be safely taxiing back to the terminal area in pea soup fog.
THE Bottom line: I don’t know why these approaches aren’t on the FAA’s front burner, because they can save lives. Be aware of them, and know where the exits are, before things ever get hot.