Reading assignment for Dual Cross-country Training MNP 4/25/03 Flight plan #1 El Tiro to Ryan 20 nautical miles Ryan to La Cholla 20 nautical miles La Cholla to El Tiro 20 nautical miles Total 60 nautical miles or ~100 km Maximum distance from towable airport = 10 nautical miles Maximum distance from safe landing field = 10 nautical miles Flight plan #2 (if conditions are bad) El Tiro to Rillito Cement Plant 12 nautical miles Rillito Cement Plant to Red Rock 13 nautical miles Red Rock to El Tiro 10 nautical miles Total Distance 35 nautical miles Maximum distance from towable airport = 4 nautical miles USEFUL FREQUENCIES El Tiro CTAF 123.3 MHz Ryan Tower 125.8 MHz (class D airspace below 4200 ft and 5 miles) Tucson ATIS 123.8 MHz (to get Tucson Approach Frequency) Tucson Approach 125.1 or 118.5 MHz (to check Parachute Jumping at Marana NW Regional (formerly Avra Valley)) Marana NW Regional CTAF 123.0 MHz (formerly Avra Valley) La Cholla (pvt) ??? MHz Pinal CTAF 123.05 MHz. (formerly Marana airport) Grob 103 twin II performance from http://www.ssa.org/Johnson/42-1983-02.pdf Best Glide Ratio 33:1 at 53 knots, 1234 pounds. With a 10 knot headwind glide ratio (over ground) drops to 26 :1 at 58 knots. How high do you have to be? Joy of Soaring uses 1/2 the glide ratio or 16:1 with no wind and 14:1 with 10 knot headwind. If 10 miles out with no wind we need 6076 feet/nm x 10 nm / 16 = 3798 ft AGL With a 10 kt head wind we need 6076 feet/nm x 10 nm / 14 = 4240 ft AGL If we are going to Ryan in still air, we need to be at 2403 + 3798 = 6201 ft ASL If we are going to La Cholla in still air, we need to be at 2940 + 3798 = 6738 ft ASL Note the difference of more than 500 feet due to the airport elevations. BUT we could fly from Ryan to La Cholla via Marana NW Regional and cut the maximum distance between airports down to 16 nm. If marginal, I might deviate towards Marana NW Regional until I got my next thermal (maybe over the Tucson Mountains) and then head straight for La Cholla So for our flight, assuming the head wind is no more than 10 knots, we will need to be between 6200 and 7200 feet ASL at the half-way point 10 nm out at the point of no return approximately 1/2 way between airports. Which altitude depends on which airport we are flying towards and whether there is a head wind or not. We will fly according to the FAI rules for 100 km triangles documented with a flight recorder (even if we aren't carrying one). This means that we must release below 1 km above ground level. We will get into a 90 degree start sector opposite the direction to our first turn. We will round every turn point by getting into the 90 deg FAI sector of that turnpoint, then we will land at El Tiro. Note that the rules offer some interesting nuances, but we are taking the simple approach and not trying to squeeze the last possibility out of them. Along the way out to Ryan I will point out some fields and ask you to select a couple for emergency landings. On the way home we will stop by them and see what they look like from the ground. Schedule 2 PM meet at El Tiro. Call 1800 WXBRIEF to get weather and check with flight service for unusual airspace closures. 3 PM launch 4:45 PM be on final glide to El Tiro...radio El Tiro to release Tow Pilot 5:00 PM be on ground at El Tiro putting glider away Down load GPS record to disk (if recorder carried) and inspect flight. 5:40 PM check out emergency landing fields 6:00 PM on way home Notes on Speed to Fly Best glide speed to fly numbers for Grob Twin II (derived from Dick Johnson's polars) Air Sink Vario Calibrated Air Speed 0 fps -160 fps 53 kts 100 -280 57 kts 200 -420 63 kts 300 -550 70 kts MacCready theory says that if you are expecting the next thermal to be +200 fpm the numbers are: Air Sink Vario Calibrated Air Speed 0 fps -220 63 kts 100 -350 70 kts I like to fly a little more conservatively than MacCready theory so unless the lift is more than 5 knots lets make things simple. Unless we are trying to stretch our glide we will just fly at 60 kts between thermals. If we expect more than 5 knots in the next thermal and we are high, lets fly 70 knots between thermals. Since there is a speed-to-fly ring on the Grob vario, we will experiment with using it for a while instead of the above rules. PLAN Launch from El Tiro and release at 5100 feet (or earlier in good thermal) Get in FAI start sector Don't get out of gliding range from El Tiro unless above 6200 feet (still air) or 7000 ( 10 kt head wind). Round Ryan FAI sector (contact Ryan if descending into their airspace) Don't get out of gliding range of Ryan until above 6700 ft (still air) or 7500 ft (10 kt headwind) unless we deviate via Marana NW Regional. Don't get into Tucson Class C airspace! Round La Cholla in the FAI sector, and don't get out of gliding range until we can get to Marana NW Regional. Don't go over the Marana NW Regional parachute drop zone if active. Don't get out of Marana NW Regional gliding range until you can continue to El Tiro. Finish at El Tiro by getting into the FAI finish sector. Time on course will be 1 1/2 hours if we average 40 knots. Alternative Calculation for Altitude Needed SSA's rule of thumb wraps the altitude needed to fly a pattern into their rule of thumb. My own personal rule of thumb (no wind) is to allow 3000 feet for every 10 nm for a low performance glider and 2000 feet for every 10 nm for a high performance glider. Then you must add another 1000 feet to inspect the field and fly a pattern. This rule in still air for the Grob results in a 3000+1000 = 4000 feet AGL requirement which is 202 feet higher than the SSA rule for 10 nm. Why do I use a different rule? In Arizona you can get really high so you may do a 30 nm glide. I think that the SSA rule is somewhat conservative for very long glides EXCEPT when thunderstorms are around or when flying in the lee of mountains. Be able to do this in your head: 3000 feet per 10 nautical miles + 800 feet per 10 nautical miles per 10 knots headwind + 1000 feet for inspection & pattern + field elevation And Speed to Fly = Best glide + 1/2 headwind Inexperienced people may wish to allow 1500 feet for field inspection and pattern. If I am flying over truly unlandable terrain where an emergency landing will badly break the glider and injure or kill me, I add another 1000 feet per 10 nautical miles to the above. And if there are Thunderstorms or Mountain Wave around, I am even more conservative.