• Glider Tow

(All photos and video from iPhone, believe it or not. I'm constantly amazed by that thing. Click to enlarge.)

Another day towing gliders/sailplanes at SkySailing. For a guy who loves sailing and flying--both an incalculably valuable inheritance from my Dad--soaring is the nexus.

The commute from Carlsbad (poor me, in perhaps my favorite all time airplane, a friend's E33 Debonair) suggested the weather would be an issue. SoCal forecast predicted doom and gloom, but usually it's sunshine and happiness despite their warnings. Not this time. Think they got it right. Gonna be an interesting day, as this picture circa 8:15am suggests (click to enlarge any picture).

"Three instructors have students at 9, so best be here ready to go then", she said. Boss Lady knows wherefore she speaks after 20+ years doing this, so I was there with bells on and ready.

And at nine o'clock customers are lining up. Note the clouds in the background.

This Grob 103 was 'boxing the wake', you can just see the towline if you look carefully and click to enlarge.

It was a busy day, and at one point I was #3 to land behind two gliders. But with full flaps and a little power the Pawnee can easily fly slower than they do in the pattern.

Speaking of slow, some pilots, I'm told, are a bit freaked towing the trainers at 55, when the white arc ends at 60 (supposedly stall speed). But the aircraft is entirely happy with or without one notch of flaps at that speed (and the pilots is too, if you pull the stall warning circuit breaker). Keep in mind, this is a bird that's designed to carry 1250 pounds of chemicals, and fly at 5 feet between hammerhead turns. It's honest as the day is long. Sure, it'll kill ya, something not to be forgotten. But, like a Cub, just barely.

The mostly boring, but for the record, video in the pattern. That little white spot in the distance is a glider. Really. Use your imagination?

As the day progressed the 200 knot jetstream way up high started to drag some of the air below along, and when it hit the mountains it made waves.

Towed 26 gliders, and added 7.8 hours to logbook, including the commute! Yeah, baby! Makes up for the days when I'm happy to get three tows.

I'm paid the princely wage of $2.50 for each thousand feet (vertical) towed, but was too tired to add them up at the end of the day--and worried about getting home.

On the east side of the mountains, looking toward home 32.9 miles away to the west (according to the GPS), it looked pretty bad. (Those weird black scimitar-like lines are the prop. At certain RPM the iPhone sees them, at others they're invisible. Go figure.)

In any event, ATIS at CRQ said, "Visibility greater than 10, scattered clouds at 2,500, overcast at 10,500." Works for me!

Weather forecasts for tomorrow is for gale force winds and bizzard conditions above the snow level, floods below, rain starting tonight. Didn't want to borrow a car and drive home, and--worse--leave John's lovely Debonair tied out in the mountains where 70knot surface winds, rain and snow are forecast for a week, maybe two. Had some thoughts about pressing on and shooting the ILS, if it came to that, even though I'm not officially IFR current. Glad I wasn't forced to make that decision. (I know, based on history I would have opted for the most conservative, and legal, option. But . . . .)

These clouds, crossing the ridge at 6,500 on the way home, suggested the forecast is right.

And we did get wet on the descent, proving their point. Nevertheless, traffic was light, but we were #2 behind a Hawker on the ILS, winds calm. So I approached high and landed long to avoid wake turbulence.

Another day, another dollar.

• Vne, IAS, TAS and BVDs

Never Exceed Speed (Vne), Indicated Air Speed (IAS) and True Air Speed (TAS) are closely linked, and if you don't understand how and why, they could have an effect on your BVDs.

Studying the Pilot Operating Handbook of a Grob 103 I was surprised to see a chart that showed never-exceed speed decreased with altitude. The jet and prop powered aircraft I've flown for over 40 years all have a redline at Vne and none varied with altitude. Vne was Vne. Never exceed that speed or bad things will happen.

But now, the Grob manual told me, Vne was not a fixed speed on the airspeed indicator. Vne, it insisted, was related to true air speed (TAS) not indicated air speed (IAS). To keep from exceeding the 135 knot TAS Vne, the never exceed indicated airspeed had to go down as you climbed higher.

Now hold on, common sense said IAS should be the limiting factor not TAS. What was I missing? How could the aircraft be exceeding Vne if the needle was way down in the green arc, which the sailplane's POH and a placard demanded?

TAS is the true speed an aircraft moves through an air mass, and the lying air speed indicator doesn't show that, at altitude, because it's confused by the lower air density. To get the true story we have to pull out our prayer wheel and correct IAS for altitude and temperature--in other words correct IAS for air density--to get TAS. No new news there, every student pilot learns how and knows why.

So what's the problem, why does Vne go down as you go higher? The answer has do with something that almost sounds sweet and friendly but is actually very nasty: flutter. Ribbons and butterflies flutter in a pretty way, but airfoil flutter can ruin your whole day life.

Flutter is a so-called aeroelastic effect that results from the springiness (elasticity of the airfoil and the surrounding air), aerodynamic forces, and inertia.

A wing has mass and when it's tweaked--when a force is applied, say by turbulence or a control input--it overcomes the inertia of the mass, and the wing responds by flexing (even a metal wing). Usually, that acceleration is absorbed or damped by the wing, the structure it's attached to, and the surrounding air. But if that tweak is suddenly imposed or is energetic enough as the result of high speed, you can make the structure resonate like a tuning fork.

It doesn't have to be a plastic ship, either. Here's a NASA film of a Twin Comanche's empennage (note how the fuselage skin flexes just ahead of the horizontal stab).



And a Lockheed C-141 (note the tail is resonating too)



What happens if you go too fast, push the aircraft past the speed where it flutters? Here's one of Grumman Iron Work's A6 Intruders.




Why does Vne go down with increasing altitude? Because there's less air to act as a shock absorber. Because there's less resistance to the wing (or other structure) flexing, you have to reduce the forces on that structure. The only way to avoid flutter (without redesigning the wing) is to go slower.

Aircraft manufacturers determine Vne by using numerical methods to compute Vd, design diving speed. (FAR 23, by the way, requires that Vd be not less than 1.4 design cruise speed, so the days of aircraft that climb, cruise and glide at 80 are over.) Flight testing is used to establish Vdf, flight test dive speed, which must be lower than or equal to Vd. Then Vne is set at 90% of the Vd or Vdf, whichever is lower, to add a margin for error--theirs and yours.

What does all this mean to you as a glider (or power) pilot? The faster your True Air Speed the more likely you are to encounter flutter. Push your slick glass ship up to redline and you're flirting with danger.

Remember, your airspeed indicator lies. It won't tell you what your TAS or never exceed speed is. In fact, it may be a compulsive liar and even lie to you down low (click to enlarge) or visit https://www.ntsb.gov/_layouts/ntsb.aviation/brief.aspx?ev_id=25093&key=0

• Dancing With Angels

Last weekend friends invoted me to tag along on a jaunt down to Torrey Pines. Once one of the premier soaring sites in the U.S., today sailplanes show up just a few days a year to enjoy the lift created by the ocean wind blowing up the cliffs that tower 400 over the beach. The mix of model sailplanes, real sailplanes, parasails, hang-gliders, and seagulls is spectacular and well worth a visit if you're in San Diego, whether the big birds are there or not.

I took advantage of the opportunity to experience an exilerating winch launch in a Blanik. All my glider experience has been at the end of a rope behind a tug, and the catapult-like acceleration and steep climp was a thrill.

Chuck Deerinck was assembling his DG-800s and I was lucky enough to get some interesting shots of his launch,


flyby (click to enlarge),


And recovery (click to enlarge).


Here's a piece that John wrote describing a very different kind of soaring:


My weekend is finally over. It is midnight, and I am completely exhausted, but I couldn't sleep without writing about today.

I worked on my glider all weekend long in the hangar, and it rained a lot, so the flying was very difficult. On Saturday, I had one 40 minute flight, that was very fast, and the only lift were little "wavelets", and only existed within a few hundred feet of 2000 foot cloud base. The second flight was in heavy rain, so I was basically forced down in about 30 minutes.

Sunday was looking like more of the same, but near the end of the day, the clouds began to break up. I finished the work I was doing, and launched at 4:30.

After a 2500 foot tow, I got off tow in light lift, and began working the leading edge of a cloud street. As I got higher, the lift got better. At about 8,000 feet, I was struggling a little to get higher.

Then I saw very fast rising tendrils of mist, forming above a few clouds, and when I flew into these, they provided spectacular lift. At one point, I was on the North side of the clouds as they exploded upward, blocking me from getting back to the airport. I turned west, and headed off at 100 knots down the side of the cloud street, around the end, and back east towards home. I resumed my search for lift, and soon I was at 11,000 feet.

The view was amazing, truly stunningly beautiful. In a DG-800S, with its incredible view, you almost forget that the glider is around you. I think the pictures here are pale in comparison to being up there, but they are still pretty good as photos go. I was thinking "This is the stuff that only Angels get to see".

I saw a full moon come up over the clouds to the east. I saw the sun setting over the Pacific, and the entire ocean turned fluorescent orange. It was very bright up high, and the lure of staying high was very strong. I looked down between the clouds, and saw the shadows on the ground getting very long, as the sunset was nearing. I contacted wave lift, and quickly and easily got to 13,000 feet. I hadn't turned my oxygen on when I was on the ground and didn't want to stretch to reach it, so given the approaching sunset, I decided to stop at 13k. Otherwise, I am sure I could have made 18,000 feet with ease.

After flying around at 130 knots for a while trying to loose altitude, but still doing nothing but going up, I finally pulled my spoilers, said goodbye to the Angels, and began my decent. I landed, and learned that of the two other gliders that launched, one fell out early, and the other made it to 9,500 feet.

Once again, my DG helped me to achieve what I likely couldn't have done otherwise. We put the glider away in the freezing cold and dark, but I couldn't get the smile off of my face. As I go to sleep tonight, and wish that my family was back from Italy, I still have a smile on my face, knowing that today I was dancing with Angels.