Totally Blind - but instrumented

Recently we had one of those rare weekend days in Dallas with low hanging cloud cover, but little vertical development (which is pilot talk for "not stormy"). The clouds just hung low over the runway at McKinney, occasionally spitting out a little rain. Perfect!

Since becoming an instrument pilot my view of weather perfection has changed. I used to like those clear blue days after a cold front had come and gone, when the air is crisp and you can see forever. I would get in a 'plane and climb as high as I could while fitting in a cross country (I was trying to build cross-country time in preparation for the instrument rating). The view was tremendous, and once I'd climbed past around 4,000 feet the air would become glassy calm.

Later I got my own aircraft, and the next year, an instrument rating. Now my idea of weather perfection is one where I can fly in actual cloud, shoot some approaches, but avoid too much turbulence, especially inside a cloud. When it rains in Texas, it tends to also storm, especially in the Springtime. Rain here tends to be an event of some violence, not something to mess around with in a lightplane.

So I launched into overcast skies, with 700 feet to the cloud base, on an IFR clearance direct KARLA, a GPS waypoint about 10 miles East of McKinney. Climbing to 2000 on a heading of 90 degrees, per ATC instructions, I swam up into clear air over a sea of white as far as the eye could see in every direction. These clouds where only 500 feet thick, and flat as a pancake.

Cleared to 3000ft, ATC gave me vectors to intercept the 212 radial from the Bonham VOR (BYP), and cleared me for the VOR-DME approach. I identified the radial using my #2 NAV and CDI, plus the DME, and also, just for grins, on my GPS. Fortunately they all agreed I was in the right place and heading in the right direction.

This pleased me. Turning in the clouds had given me what pilots call "the leans", which is vertigo. Pilots cannot trust their bodies senses in clouds, they must only trust the instruments. You turn right, and the body says you are climbing and turning left. When you can see on the panel that you are level and turning right, if you trust your sense of balance which says you climbing and turning left, you will move the controls in exactly the wrong way. That's one reason it takes so long to become instrument rated, and a reason why few private pilots complete it (almost all commercial pilots are instrument rated).

Once on the radial and 12 miles from BYP, I throttled back and descended into the murk at 2200 feet, then 7 minutes later at 22 miles on the DME down to 1400 feet, and clear of the clouds. I could see the airport dead ahead, and approach handed my over the tower. I told them I would end the approach and requested the ILS to runway 17. Cleared direct to the initial approach fix at FLUET, I recontacted DFW approach, and was cleared for the ILS. This time, I stayed at 2500 feet for the outbound leg and procedure turn, which meant I stayed mostly in the clouds, only occasionally popping out of the top at a particularly low area, or between cloud cells.

Once on the inbound leg, I intercepted the ILS glideslope, and setting up for 90 kts and 450 ft/min descent rate, came out of the soup at 1700 ft. The clouds were continuing to rise - now they were 1100 feet above the runway, making the field technically VFR. I canceled the approach and requested the GPS RNAV approach to runway 35 (the other end of the same single 7000 ft long runway at McKinney). ATC cleared me for the approach, and asked me to climb to 2500 feet, but them changed their mind and asked me to make the approach at 2000. I said "OK", because that would put me back inside the clouds, and because I could hear them working a Beechcraft King Air on the same approach. I suspected they want me to stay well below him.

At 2000 ft I kept occasionally catching sight of the ground, but by now I had got completely over my vertigo, and was flying entirely on instruments, which in the case of GPS on a real IFR flight simply meant following instructions until established on the purple line, and then descending along the GPS WAAS glideslope as indicated on the #1 CDI (just like an ILS). The main difference is that an ILS becomes more and more sensitive as you get closer to the transmitter, a GPS WAAS does not, making it very slightly easier to fly.

A GPS receiver uses satellites to fix its position in space, a constellation of 24 satellites controlled by the US military. For precision approaches, GPS uses a ground-based enhancement called "Wide Area Augmentation System", or "WAAS". WAAS approaches require an airport to have no ground facilities at all - so they are rapidly replacing NDB approaches at small airports, and even VOR/DME approaches will be a thing of the past soon.

It only took a few seconds to clear the clouds once on the WAAS glideslope - I could see the runway straight ahead about 5 miles away. I flew through a short, sharp rain shower, and landed. I didn't need the 3 approaches to legal currency, but the experience was useful, and knowing that I could do this for real was invaluable. It was also fun!

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.