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Wednesday, May 19, 2010

Going Fast, ................Slowly

Earlier this month I flew my Sundowner from Texas to Pennsylvania and back, approx 2,000 miles. It was Mother's Day, and I was hankering for a flying challenge, so off I went.

Spring in the Central Plains and Ozarks can be rough. We have tremendous thunderstorms and even tornadoes on a regular basis. In the summer, typically Texas broils under a semi-permanent tropical "high" that keeps weather fronts off the the North, in Oklahoma or Kansas, but in May the high has not yet formed, and we get fronts coming and going, and highly variable, sometimes entertaining, sometimes dangerous, weather.

On my flight up, a cold front was sweeping down the plains, from Oklahoma to Detroit. Winds in front of a cold front tend to be strong and from the Southwest. After the front passes, they swing around to the north, then northwest. Ahead of the front, the air is warm, but usually clear. And that is what I had all the way to PA - a 40 to 50 kts tailwind, and apart from a thin layer over my departure airport, no clouds, and visibility about 10 to 15 miles. My Sundowner has NEVER covered the ground so fast - I saw ground speeds as high as 165 kts (190 mph).

I made it to PA a full hour ahead of schedule. The front caught up over the weekend, causing rain and thunderstorms.

I was planning to depart on Tuesday, but a look at the weather map convinced me to start a day earlier. A warm front was coming up the Ohio River valley, pushed by a strong cold front behind it, bringing the usual turbulent and dangerous weather. So I launched at 11:30, and by 3:20 I was on the ground in Bowling Green, Kentucky.

I can fly in warm fronts without much problem. Warm fronts tend to generate hazy, calm, muggy and rainy conditions, but without much vertical development - i.e. storms. I landed in Bowling Green in light rains and lowering ceilings. My plan was to let the thunderstorms ahead of the cold front pass by overnight, and take off in the crisp cool air behind.

Well, the front passed - to the north. Louisville, Cincinnati - they all got storms. But in Oklahoma, Missouri and Kentucky, the front just kind of stopped, spawned tornadoes that killed several people, and shuffled to the East. That meant layered clouds and the potential for thunderstorms all along my route.

It also meant I would be flying against headwinds, almost as strong as those that helped me going the other way.

I left Bowling Green at 9am. I entered the cloud at 2700 ft, and climbed to my planned cruising altitude of 6,000, still in the clouds, with moderate turbulence. I asked for, and received clearance to climb to 8,000. After almost an hour, I started to be able to see the cloud tops above me, and to break out occasionally into small patches of clear sky. I heard another aircraft say that the tops were between 10,000 and 11,000 feet. So I climbed to 10,000, where I was in the clear about 50% of the time. Somewhere over West Tennessee, battling headwinds near 40kts (so my ground speed was about 75 kts), the clouds lowered below my altitude. Passing North of Memphis I could see the FedEx planes on approach in a long string.

With the slow ground speed, I decided to change my planned fuel stop from Hot Springs, to Conway, Arkansas. The field was covered by a thick overcast clound layer from 2,500 to 6,000 feet, so I made an VOR/DME instrument approach, and landed visually once I was out of the clouds.

After refueling, I took off and climbed to 6,000 feet - just above the cloud tops. At 6,000 the head winds were a little less, and I had a ground speed of 85 kts, which slowly climbed above 90 as I passed over Oklahoma and into Texas. Just past Paris, Texas, I saw the ground for the first time, and descended into the Dallas area through patchy, hazy cloud, landing at 4:20pm.

In flying, there is usually a head wind. It's straight mathematics - imagine you are flying 1,000 miles at 100 mph. With no wind, it would take you 10 hours. Now, imagine that you have a 20 mph tailwind going one way, and the same wind going back. Now, your ground speed is 120 mph up, and 80 mph back. So the 10 hrs on the way up now drops to 8.3 hrs, but your return trip now takes 12.5, for a total of 20.83 hours, of which 40% of the time you had a headwind, and 60% of the time a headwind.

The winds are (nearly) always against you.

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