Report from the ridge

We received this from John Good, regarding today's ridge flight:

Based on a forecast of reasonably good winds all the way from Pennsylvania to Tennessee, I decided to declare a big Out & Return task: the southwest turnpoint was Luttrell, the end of the Clinch Mountain ridge not far from Knoxville.

Winds at the launch point (Karl Striedieck's Eagle Field) were too westerly, so the start involved an aerotow behind Karl's Cessna 180 to near Tyrone PA, where the ridge turns a bit and a westerly wind can work. Not long past 8am I was pounding along Brush Mountain (overlooking the city of Altoona) at 110 knots, feeling optimistic.

Despite just a hint of rain (call it mist) and rather low cloudbases, my crossing of the Altoona gap was no problem. But Bedford, some 20 miles further on, was a nail biter: Solid clouds at around 3100' meant I couldn't get the sort of height that makes this 8-mile gap friendly - at the far side I was only about 400' above the valley, but favorable winds soon had me back at ridgetop. I stormed on past Hyndman, having not yet had to make a turn (nor having encountered much of anything worth turning in).

Yet the view ahead was growing ominous: no sun on the ground anywhere near Cumberland. That rules out the easy way of getting through the "Keyser knobblies": wave. And solid clouds with low bases were saying that thermals weren't a likely option. I've done this stretch on ridge alone, and the winds of the past half hour suggested this might work. But near the Allegheny Ballistic Lab that changed. The ridge (not amazingly high here) became really weak - I was thinking it might have been some sort of wave suppression (this area sees a lot of wave) but there were no wave signs in the clouds. And light rain (call it heavy mist this time) added to my sense that conditions had turned against me.

The view ahead was now discouraging: solid clouds with lower bases and areas of heavier precipitation. Faced with a substantial stretch of low, broken ridges ahead and poor to nil landability, this was below my standards for safe flying. I spent about 30 minutes beating back and forth on the ridge (occasionally falling below its top) hoping for some sign of improvement. When none was evident, I decided to head home.

This wasn't as easy as it might have been, in large part because a lack of thermals made it hard to transition between ridges. But I managed to stagger back to Tussey Mountain and eventually to reach Centre Airpark (about a 20-minute drive from Eagle Field). Karl very kindly came with my trailer to fetch me.

So, not a successful flight - but interesting, and I managed to keep it reasonably safe, so no big cause for regret.

Ambitious

John Good will be attempting a long ridge flight tomorrow. He is planning an early takeoff from Eagle Field in Pennsylvania and a start just north of Altoona. His turnaround point could be as far south as Knoxville, Tennessee, which would result in a total out-and-return distance of around 900 miles. Or maybe he'll land at Altoona in time for breakfast, you never can tell.

If he remembers to turn on his tracking device, we'll be able to follow his progress on the web.

Good luck, John!

Critical Assembly Check

Today's guest blogger is John Good, who wrote up his flight from yesterday. His flight log is available (open this file with your favorite flight analysis program).

The PW-5 aileron story, and the post that mentioned distractions during glider preparation prompt me to offer my thoughts. Distractions are never a good thing, but they are also inevitable. Safety requires a scheme that ensures an airworthy glider even when a host of distractions interfere with assembly.

Thus we have the Critical Assembly Check (CAC). This is a separate check of each item that the manufacturer and the service history of the glider indicate are critical to flight safety. For every glider you fly you should have a list of these critical items, and you should check them prior to flight. It will help if you get in the habit of placing a mark on the wing root tape that indicates you have done the CAC.

The list should be as short as possible. It should not include "nice to have" items such as installing batteries and checking their voltage. Batteries are important and should indeed be checked prior to launch. Failure to do so might well be reason to land prematurely. But there should be no glider in which a battery is required for safe, controlled flight - so checking batteries should be part of your assembly checklist, but not your CAC.

On my Discus, the CAC includes three items:

• Main pin secured
• Tail pin fully seated
• Controls free

This may sound awfully simple, but it works - there never has been a Discus that was unairworthy when these three items were correct^*.

Note that the CAC is not the same as a positive control check (PCC). For an aircraft that has manual control hookups, the CAC might include a PCC (though direct inspection of the control hookups has in a number of cases been shown to be more reliable). And there are almost certainly other items in any CAC (such as checking that pins are secured).

^*It should be noted that weight and balance sufficiently out of tolerance would provide another way to achieve an unairworthy Discus.