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Flying the PAR

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This article originally appeared in IFR magazine, Sep. 2006.

Flying the System

Getting tired of reading how someday WAAS-in-it-for-me technology will offer near-precision approaches to every ma-and-pa airport in the nation -- but it's not ready yet? Dreading the day when you'll have to choose between plunking $20,000 worth of new avionics in your panel or not flying IFR? How'd you like an approach that could get you to CAT II mins in your Skyhawk using nothing but your radio (even a handheld radio, in a pinch)? The military has had this approach -- precision approach radar (PAR) -- widely available since the 1960s, but in today's high-tech, low-staffing world, it's on its way to extinction. At least in its current setup, that is.

The Verbal Approach

Looking positively dowdy to the right of a modern radar display, the PAR system still soldiers on.

The older your ticket is, the more likely you learned about PAR approaches in your instrument training. Most instrument students today get about two sentences on the PAR: "They're available at some military airfields and allow the controller to talk you right down to ILS-level minimums. You could use one in an emergency and get down with nothing more than a hand-held radio." Thanks, but if I ever need one, how am I supposed to get it? What's it like to fly? The answer is that they are hard to get but quite easy to fly. The equipment exists at some military bases and it's up to the base commander whether civilians can try them for practice. In the wake of 9/11, low approaches to military bases became as likely as direct routings through New York airspace, but some bases will still allow them during slow times. I made a phone call to Brunswick Naval Air Station (KNHZ) just 20 minutes north of my home base to see if they had a PAR and if I could come up and fly it. They did and I could, but only under two conditions. The first was that I couldn't land at the base and the second was that this wasn't a blanket invitation for every pilot in the Northeast to come try out a PAR at Brunswick NAS. That worked for me and I hopped in the car for a drive to the base and a view of the PAR from the controller's side of the scope. My guide for the day was AC1 Shea Bickerstaff, a naval air traffic controller seasoned on shipboard operations in the Middle East. Bickerstaff is now the Training Chief for ATC at Brunswick. He gave me the tour of Brunswick's shiny, new TRACON and Tower. (If you're thinking, "Hey, isn't Brunswick NAS being decommissioned in a few years?" Yes, it is, but they just got a new ATC building. Don't ask.) Lining the wall were several large-screen color displays running the latest ATC software. Between them were two old, round scopes that looked like set pieces from Doctor Strangelove. "The PAR is a piece of equipment that is past its shelf life," said Bickerstaff. "We had to get one of these fixed recently, and when the tech showed up -- I swear -- the guy was 82 years old." That tech won't be needed for too much longer. Just maintaining the PAR can run $2 million a year in parts and personnel time. The PAR needs alignment every hour if it's not been used for an approach. That's only a three-minute task, but it adds up. The radar head must also be swung around by motors to point down the runway in use. By comparison, installing an ILS costs a mere $1.3 million and the system is largely self-monitoring. Changing active runways usually requires pressing a button. Brunswick should have a new ILS in service this month, which doesn't bode well for the future of their PAR. Until the ILS comes on line, though, the only approach other than the PAR is a TACAN (similar to a VOR-DME) that gets you within 500 feet of the ground. (See "What The Heck Is TACAN?" at right.) The PAR can get you down to within 100 feet of the ground and at visibilities as low as 1/4 of a mile, if the pilot is qualified to fly it all the way down. Not all of them are.

Practice, Practice

The actual radar sits on a turntable out between the runways.

So that I could see a PAR from the controller's side, the Brunswick ATIS included a request "fishing" for pilots willing to fly the PAR on the clear day. Luckily for me, a KC-130 Hercules coming home from overseas took the bait and was willing to fly a PAR down to minimums for practice -- a generous offer considering this was the end of a long trip. The scene was odd. On my left, one controller vectored the Herc on a downwind and base using a new, color scope with a datablock following the target. On my right, another controller fiddled with adjustments on a round scope with an amber sweeping line displaying two paths, one for lateral displacement and one for glidepath. When the Herc was on an intercept to the final approach course, it got a frequency change to the guy on the round scope. There was a quick radio check and then the final approach controller started giving courses to fly and information: "Fly heading 120. Left of course. Correcting rapidly." As the aircraft established inbound and on-course, the controller issued a new heading and instructions not to acknowledge further transmissions. Now the comments came every five seconds, "On course. Approaching glidepath Slightly right of course right of course, fly heading 113 Slightly right of course, correcting. On glidepath." The Herc began a descent without any more instruction than "on glidepath." I guess those Navy boys had their numbers dialed in and winds weren't too challenging, because the rest of the approach consisted of the controller issuing one minor heading change -- two degrees -- and saying "on course, on glidepath" until the pilot broke it off at 250 feet AGL for landing. Back in the training room where they have a PAR simulator, Bickerstaff told me it takes about six months for the average new controller to become competent on the PAR. There is a double delay for reaction time inherent in this system. The controller must notice if the aircraft is diverging from course on the scope. He or she must then issue a correction -- after quickly deciding just how much -- and then the pilot must react and make the correction in the aircraft. The new heading or rate of descent must take effect and be evaluated by the controller on the scope. Pilots don't like abdicating control and sometimes this is a problem on the PAR. "When you're flying the PAR, we're basically telling you to ignore your instruments," said Bickerstaff. "I'm watching the track to see how well the pilot is taking my turns. Sometimes they see the gyro go so far they stop taking the turn." Controllers can remedy this by telling the pilot this is now a no-gyro approach. This does two things. It removes headings from the instructions -- "Start left turn ... Stop turn" -- and makes pilots question the validity of those distracting instruments. Pilots then just do what they are told. Most often, though, the system goes off without a hitch. There are even some non-official phrases that sneak in there among the PAR-experienced: "Slightly drifting left" means the heading is just a bit off but not enough to really issue a correction. It's a suggestion to give it a bit of right rudder. My host was honest about the system from a pilot's point of view: "From being on both sides, I wouldn't want to shoot a PAR if I had another option like an ILS."

Talk Me Down

The approach display isn't fancy, but it gets the job done. The multiple dashed lines on the approach course are distance markers and show the beam angle left or right of centerline. The controller can adjust this to find aircraft before they intercept. The aircraft should be centered on the solid glideslope line. The dashed one is the lower limit. The aircraft appears as a long line as well. This aircraft is slightly right of course and approaching the glidepath.

A few days later, my friend Rudy hopped in the right seat as safety pilot and we flew up to Brunswick to try the PAR ourselves. There wasn't much to brief for the approach other than the runway we were using and the published minimums. Since we weren't bound by any Navy policy, we could fly it right down to 100 feet if we wanted. In fact, Bickerstaff told me that course guidance would be given right to the pavement if we didn't say we were going missed approach. Course guidance is accurate to 30 feet left or right by the end of the runway. Given that the runway width is 200 feet, a PAR should put us somewhere over the pavement every time. The vectors for downwind, bases, and an intercept were identical to vectors for an ILS. Then came the frequency change to the final-approach controller and a quick radio check. We were issued headings and cleared for the approach. Acknowledging that clearance was the last thing we said. How did it go for that first approach? Well, I had the deck stacked in my favor flying a G1000-equipped Skyhawk that day. Things were moving slowly and I could see the heading to one degree with ease. Even so there were a couple "left of course, diverging rapidly" calls until I got settled. After that, it was just like an ILS, but with a mental picture of crossed needles rather than a real one on the CDI. As I got in close, "slightly above glidepath" rang in my ears at a three-to-one ratio with "on course," which is the standard ratio if things are going well. I was told when I was over the approach lights and when I was over the threshold. At 100 feet AGL, and easily in a position to land, we went missed. Since that was too easy, I requested a no-gyro approach for the PAR and adjusted my view to nothing but the backup instruments Cessna installs by the pilot's right knee. The result was an approach with more "slightly right" and "slightly above" calls until Rudy reminded me to make smaller corrections close to the runway, but at 100 feet we were still in a position for an easy landing, had that been allowed.

Familiar Lessons

The PAR turned out to be a piece of cake. In a pinch, it really could get you down with nothing but a radio and an attitude indicator if need be. Like any approach, the PAR is all about stability and trends. Listening to an experienced controller giving corrections of one or two degrees and slight trend information for your glidepath is a great reminder that small corrections and a touch of patience are some of the best approach tools you have. It's sad to think they will all fade from service. There is a system the Navy uses "on the boat" that normally provides automated approaches or CDI guidance to the pilot, but can operate like a PAR if needed. These systems are installed at a few land facilities, but don't go asking to shoot one of those. If you can fly a PAR before they disappear, it's a fun and useful exercise. Perhaps, late at night -- when the skipper isn't in his office at mid-field -- some facilities might even let you shoot one without previous permission. (Not that I've ever heard stories about how convenient it is that no one can read "United Airlines" off the side of an empty regional jet in the dark.) In our world of ever-mechanized flying, an approach that relies entirely on the human computer is a welcome diversion.
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