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Wednesday, February 4, 2009

Flying Blind

It’s almost been 6 months since my last real instrument approach.

That one was an Instrument Landing System (ILS) approach to Erie PA, when I was visiting my parents over the summer. I flew my Sundowner from Nashua NH to Erie PA, climbing over some building cumulus cloud near Buffalo NY that took me up to 10,000 ft. As we neared the shoreline of Lake Erie, the clouds stopped, like a giant wall of orange tinted white as the sun lowered towards the Western Horizon.

Erie was reporting no ceiling (clouds), but poor visibility. So I intercepted the extended centerline (called the localizer) and descended as cleared until capturing the glide slope around 4000 feet. I followed the beam to land on runway 24. But that was in July 2008.

The FAA requires that before you can file and fly under instrument conditions, you must be “current”, which means you must have completed 6 instrument approaches and flown holds and intercepted a VOR radial within the last 6 months. So to remain current, I had to do some blind flying.

My Friend “D” owns the only other Sundowner based at TKI. It’s been in shop for a while, after a mishap with a hanger door, so he was more than happy to volunteer to be my safety pilot. Let me explain that.

When flying to currency, you can either fly in real instrument conditions (which can be hard to find in North Texas), or you fly “under the hood” – in my case, a set of goggles that fit over my spectacles, and are fogged so that I can only see downwards. So all I can see are the airplane instruments, I can’t see out. The safety pilot’s job is, well, safety. His or her job is to look for other airplanes, and to take control if the safety of flight is in doubt.

So a few Saturdays ago, “D” and I climbed into “Charlie”, my sundowner, for a few approaches. We took off from McKinney airport at 9:30am into some severe blue weather – no clouds, clear visibility due to strong winds from the North – a Texas “Blue Norther” (cold front) has blown through the night before, dashing away all the airborne pollutants and dumping them into the Gulf somewhere. I climbed in the blind to 2,500, tuned in the ILS approach for runway 17 at Mesquite and waited to intercept the glideslope.

The ILS displays on an instrument called the CDI, or “course deviation indicator”. The CDI is round, and has a vertical needle that shows which direction to fly to intercept the extended runway centerline, called the "localizer". The ILS version also has a horizontal needle for the glideslope. The pilot’s goal on an ILS is to keep the needles crossed in the center of the dial, by following the needles – if the needle is to the right, turn slightly right. If the horizontal needle is low, increase your descent rate until it is back in the center. You can fly very accurately on the ILS – airliners can even use it to land completely blind. My airplane can descend as low as 200 feet above the runway using my system.

The only problem was that with the wind from the north, we were approaching the wrong end of the runway! So I abandoned the approach a bit higher than normal to stay out of the way of departing airplanes, and climbed back to 2,500 over the runway to set up for the back course approach to runway 35.

The ILS is set up for an approach to a specific end of a runway. Some runways have an ILS for each end, usually those that host airline traffic. At some airports, you can use the back side of the ILS to fly an approach – it’s tough to do because everything is reversed – instead of flying towards the needles, you must remember to turn away from them. Some airplanes have a button that can reverse the CDI sensing – mine does not. In the real world I would probably use my autopilot on a BC approach, because it can set up to fly it with reverse sensing, but for practice, I did it the hard way.

Too hard in fact. I lost the signal right on the turn in from the course reversal turn. I did this approach perfectly when I was doing my test ride back in October 2007. But the rules don’t say you have complete the whole approach for it to count, so when I abandoned the approach at 2000 feet, that was 2 down. I needed 6.

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