Thursday, September 09, 2010

The Blanik Dilemma

In June, there was a fatal accident in Austria involving a Blanik L13 glider which lost a wing. The investigation is not yet complete, but the manufacturer / type certificate holder, known as LET, issued a mandatory bulletin restricting aerobatics and requiring an inspection (for cracks) and requiring that the results and the glider's usage history be sent back to LET for evaluation. Later, the FAA issued several versions of the same bulletin, requiring a more stringent inspection. LET was to evaluate each glider's usage history and rule as to whether the glider could continue in service.

The latest FAA version has taken back the decision process from LET, but it essentially grounded every L13 until it passes an even more detailed US-based inspection. But the inspection has not yet been defined, so the entire fleet is in limbo until it is.

Our club owns two L13's (built in 1973) which we use for primary instruction. We performed the original inspections and found no cracks. We examined the aircraft logbooks and gathered the required information about number of flights, number of hours, ratio of solo vs. dual flights, ratio of aerotow vs. ground launches, number of aerobatic flights, damage and repair history etc. Since I'm the secretary my club and I retain the older logbooks, I took on the task of compiling the usage information. It was really interesting to look at the history of these gliders I have been flying: who owned them, what they accomplished in them, how many hours the pilots accumulated, the various minor and major damages, when they gliders changed hands (or wings!), how long they sat idle... each one has a story to tell. I think I'll write an article for our club newsletter with some of the more interesting facts about each one. I learned a bit about the Airworthiness Directive, repair, and documentation processes as well.

The glider community (at least the segment of it that does flight instruction) is in a spin at the moment. There are about 200 L13's in use in the U.S. I'm guessing that they are second only to the Schweizer 2-33 in popularity as a training glider, and I'm sure that some commercial operators use L13's for tourist rides as well. So a large part of the U.S. training fleet (in clubs and commercial ops) is grounded. Rumor has it that the larger commercial operators are working with the FAA and SSA to develop the new inspection and approval process. No one knows how long this will take, how much the new inspection procedure will cost, or who will do the evaluation.

Rumor has it that someone in Europe is looking at acquiring "new" never-used L13's that have been in storage in Russia, and selling them after appropriate refurbishing and updating; since the concern is fatigue and not age, theoretically these would be "safer".

So here's the dilemma: Does one failure justify permanently grounding an entire model of aircraft? Blaniks are not failing at in flight frequently. Was the accident aircraft an extreme case, i.e. used for extensive aerobatics? Was their hidden damage not caused by fatigue? We just don't know. Clubs like ours that rely on L13's have had to cancel training, and will lose members to other clubs/operations that fly other ships. On the other hand, if L13's are reaching the end of their useful life, we as operators need to be responsible and not fly them if they are dangerous. Usage records are not perfect - many operators did not record the type of launch, the number of occupants, the number of aerobatic flights, etc., they just recorded hours and flights. So any evaluation based on usage pattern will be quite subjective, and the evaluators will probably want to be very conservative. And developing a definitive inspection/testing procedure will be expensive.

For a more detailed history of these events, visit

Monday, September 06, 2010

Dual thermal flight over the Tehachapi Valley

Sunday afternoon we spent an hour or so troubleshooting an electrical problem in the PW5, and cleaning it out. This morning we put it in the trailer so it can be repositioned to another gliderport for the fall and winter.

I also got my Official Observer to sign my Silver duration forms so I can send them in to the SSA. We've each been traveling, so I hadn't seen him since my flight on July 4.

This morning I helped N prep and launch the Grob 103 for two instructional flights. Now he has been "signed off" to fly the Grob from the rear seat. Our club requires signoffs for different aircraft, seats, and locations, beyond what the FAA requires, in order to enhance safety and learning. After his second flight, I jumped into the front and we took off at 12:44. N did the takeoff, and I did the landing.

There were very few gliders up today, probably because originally the forecast was not so great. (Also, I think a lot of pilots use the last day of the holiday weekend to drive home if they live far away.) I think we thermalled with one and saw only one other.

We let off over the mountains at 8200' MSL and went back to where we had seen lift, but could not connect. We tried some ridge lift (wind was from the east) but it wasn't strong enough and we made our way back to the valley.

Fortunately we connected with decent thermals which twice took us back up to 7000-7500 feet. Not high enough to go exploring - even to the end of the valley - but high enough to have some fun. There was some other spotty lift which may have been a north-south convergence line but was not very organized. Once when we got high enough I tried for anabatic lift over the lowest ridge of the mountains, but it was not working well enough for me to turn and climb the next ridge.

So we came back and landed on 9L at one hour and 14 minutes. Landing from this direction enables us to roll right up to our tie-down, avoiding a long push in the heat.

Huh. As I'm writing this, a glider just took off to the west. Today was the only day in which the wind reversed itself. Some days it reverses many times and we need to push the lined-up gliders back and forth to reverse takeoff direction.

Look at my three posts from this weekend, and you'll see that the conditions and best flying locations were different each day. One thing for sure - flying at Tehachapi requires you to learn flexibility! I'm very pleased to have had good flights (if not very ambitious ones) all three days. A total of 5:18 in the air, but I can only log half of the dual flights as PIC time.

Sunday, September 05, 2010

Shear line soaring

The NWS forecast called for winds gusting to 45 MPH so we thought we'd get shut down, but they never came. Just the usual moderate west winds, which actually can make for decent soaring in the valley. The wind enters the Tehachapi valley from the west around two sides of a mountain, and the colliding winds set up a convergence, commonly called a "shear line". I've tried to work it before but never had much luck.

Today another pilot wanted to fly dual with me in the Grob 103. We don't have an instructor this trip, so the newer pilots pair up with more experienced pilots and learn about flying this location, or get experience in the Grob, or whatever. T had had some flights in the Grob but is not signed off to fly it yet. He flew from the front and I from the back as PIC. Since I'm still working on becoming an instructor, it's good experience for both of us.

We released at 2800' AGL (7000 MSL) and fairly promptly found a thermal that took us up to nearly 8000 MSL. That seemed to be the top of the lift all day, both shear and thermal. We went back and forth and usually found narrow bands of lift along a northwest-southeast line. Often it was too narrow to circle in, so it was apparently mostly shear line. At times we could fly directly upwind and still gain altitude. That sounds like a really odd thing to be able to do without an engine, huh? But if the wind is coming at you and colliding with wind from another angle, it deflects upward and takes you up! Kind of magical.

We traded off flying from time to time. There were three or four other gliders in the area, and we all followed each other to the lifting areas. We saw a grass fire start and get put out a few minutes later, and observed how the wind carried the smoke different directions at different altitudes. Wind shear made visible!

We used soaring ravens to find lift, and we came within a hundred feet or so of a hawk, which quickly turned and dived away from us. It was brownish on top and black-and-white underneath, which in my bird book looks like a Rough-Legged Hawk. I'm still hoping to encounter an eagle in flight some time.

Eventually we got a bit tired and ran out of drinking water, so we came down after 2 hours and 8 minutes.

Saturday, September 04, 2010

Mountain and valley flight at Tehachapi

I took off at 1:37 in the club's PW5. I let off at 3900' AGL (8100 MSL) in what I thought was good lift. I had to go back and search for it a bit, but soon I was climbing. That first thermal took me up to over 10,000. There were 4 or 5 gliders over the mountains, and we all used each others as markers for usable lift. I flew with BT, KMA, and Blue J at various time.

I had put my Li-On backup battery pack into the PW5 because the club's gel cell battery seemed to be discharged. I found that mine ran the instruments OK but I could not transmit well on the radio, and switched to my portable. I guess I should get a gel cell as a better backup - they're not that expensive.

We found that there was not much thermal lift but instead there seemed to be a convergence line along the top of the mountains. It was bumpy but worked well. The highest I got was 10,900 MSL, which is just about what the RUC forecast and Dr. Jack predicted.

I was able to use my oxygen tank with the ship's EDS system, which I had not been able to do the last couple of times. I think Greg replaced the O-ring on the regulator, and now it doesn't leak anymore. It's very cool - comes on automatically at 10,000 MSL.

Eventually I headed out toward Bear Mt. and a tour around the valley. As expected, I found no more significant lift. There was a little over the recent burn area, but not enough to work. So I eventually came back in, finishing up at just under two hours. My landing was really good and I rolled right up to where our other glider was parked. Actually the wind gets partial credit. Once the PW5 slows down, its tiny rudder doesn't let you override the tendency to "weathervane" into the wind. But it was just what I needed to roll off the right side of the runway.

All in all, a nice flight, if not very ambitious. Had I gotten up to 11,000 consistently, I could have headed north, but it just wasn't that strong.

Tonight my trailer is full of things being recharged: main battery, backup battery, PDA, and handheld radio.