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| Volume 3, Issue 6 |
July, 2004
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CROSS COUNTRY SOARING (Part 2) Are you serious about learning to fly gliders cross country ? If you read the suggestions in the last "Wingtips", went out and acquired an aviation chart of the area and studied it as suggested --- Then you're well on your way ! As mentioned previously, a lot of the success will come from doing the PREPARATION "on the ground", so that you can concentrate on flying the glider once you are "in the air" and not be burdened with making all kinds of extra mathematical calculations that are needed to work out if you have sufficient height etc. to get where you want to go . Some "Rules of Thumb" help - I for one like to know how far the Sailplane can go for each 1000 ft of altitude. Do you know those numbers for the club ships? They are : 1) The BLANIK L23's.Best L/D approx. 27:1 at 47 knots. That's about 5 miles per 1000ft . I suggest you use 2.5 miles /1000 ft to be safe. 2) The GROB 103. Best L/D approx. 35:1 at 57 knots. That's about 6.6 miles per 1000ft. Suggest you use 3 miles / 1000ft . 3) The PW - 5. Best L/D approx. 32:1 at 48 knots. That's about 6 miles per 1000 ft . Suggest you use 3 miles / 1000 ft . So to get to ELWOOD Airport , about 10 miles west of Alexandria you would need : BLANIK - 1000(10 / 2.5) + 1000 ( safety altitude) = 5000 agl at Alexandria. That's with no significant wind. Obviously with a tailwind you would have altitude in hand. But have PATIENCE and go only when the winds are light ( Not into a strong headwind.) Similarly you could calculate the height needed to get there in the GROB or the PW - 5. If you decide your first "sortie" will be a short "out and back" from Alexandria to a prominent landmark, you can now do the simple calculation. A choice might be the Railroad crossing in the middle of Alexandria town - about 6 miles there and back. To do that in the GROB you will need 1000( 6 / 3) + 1000 = 3000 agl at Alexandria . This roundtrip flight should be possible on almost any reasonable soaring day . Try it, you'll find it easy now that you have done some PREPARATION ! Fly Safe. Have Fun. ZA. |
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