If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below. |
|
|
|
Thread Tools | Display Modes |
#11
|
|||
|
|||
As I read this, I think about how that one hour of
less flying means different things. Less exhaustion, for one. The most impressive thing to me about the 1-26 diamond guys isn't the flight itself, but the amount of time spent doing it. The super-long wave flights (Kestrel?) were similarly impressive just from the endurance perspective alone. I personally have seen forecast conditions and experienced times when a 300km flight looked possible, but the gliders I had available had low enough performance that I personally didn't have the recent experience with endurance flights to make the 300km with what I considered an adequate margin of safety. For me, the difference between a 3 hour and a 6 hour flight is still quite significant. A flight of over 10 hours (which one might need for a 1000km) looks quite daunting to me. IIRC some of the Kestrel wave flights exceeded this. For the guys who are recommending max wing loading, how much of this is because you want to make the flight as short as possible for endurance reasons? In a similar vein, a 500km downwind seems a lot different (in endurance terms) than a triangle or O&R. At 02:36 03 August 2005, Andy Blackburn wrote: At 18:48 02 August 2005, Eric Greenwell wrote: Tactically, one should take off with full ballast early enough to have a chance of completing the flight, and drop whatever it takes to stay up. That's one approach - but keep in mind that the difference in climb rate between full and empty (in a 45-degree bank) is less than 50 fpm. Furthermore, the McCready-derived XC speed differential for full versus empty water is 6-9 knots. The actual difference with streeting, etc. may be greater. That amounts to about an hour less time on course with water versus without. To break even without ballast you'd have to make about 80 miles before you could get started on course with ballast. I'm thinking this would only be true if the day developed with either very weak (0.5-1.5 knots climb, dry) or very narrow thermals for a very long time (1-2 hours). Under those conditions I don't think you're making 80 miles even if you have Helium in your wings. I'd recommend taking tows until you can stay up with full water. 9B Mark J. Boyd |
#12
|
|||
|
|||
T o d d P a t t i s t wrote:
M B wrote: I personally didn't have the recent experience with endurance flights to make the 300km with what I considered an adequate margin of safety. For me, the difference between a 3 hour and a 6 hour flight is still quite significant. A flight of over 10 hours (which one might need for a 1000km) looks quite daunting to me. IIRC some of the Kestrel wave flights exceeded this. I've flown over 12 hours a few times. The endurance keys are 1) a good pee system, 2) water 3) comfortable in the cockpit (cushion/chute, hat, sunglasses, etc) 4) food, in that order (IMHO :-). I would add somewhere in the low stress flying. For me, this comes from enough experience with the area that I know where I am and what's coming next (navigation), total familiarity with the glider (no distractions), and predictable weather (confidence). A four hour flight with three low saves is much more tiring than an eight hour flight without any. In my case, part of the low stress comes from flying a motorglider, so I can concentrate on the soaring and not stressing out over the possibility of a long retrieve. Powerless glider pilots can achieve the same result other ways - Henry Combs is the quintessential example of developing a great retrieve system! -- Change "netto" to "net" to email me directly Eric Greenwell Washington State USA |
#13
|
|||
|
|||
"Andy Blackburn" wrote in message ... At 04:54 01 August 2005, Ttaylor At Cc.Usu.Edu wrote: I am working on the planning for a 1000K attempt. One question I have is how much water should I launch with in my Ventus B? I can carry up to 40 gallons (150 liters), but for a 1000K flight I will need to launch in early weak conditions, followed by strong conditions latter in the day. Options would be to launch with 20 to 40 gallons. Twenty to thirty would probably give a good balance for early climb and later running. Any suggestions for an optimum balance? The optimal, assuming strong enough conditions to support 1000k, is full water - so long as you can stay aloft early in the day. The slower climb in the first 1-2 hours of the day is more than offset by the faster cruise for the peak 6-7 hours later on. 9B Don't forget to have a plan for dumping the water. There's no need to hold on to it after the thermal strength drops below that which justifies ballast. It probably won't get any better late in the day. This is particularly true if you have a tailwind on the final leg. Bill Daniels |
#14
|
|||
|
|||
In a comfortable glider (both physically and mentally comfortable),
there really isn't much difference between 3 and 6 hours. In fact, after an undercalled task, landing after only 3 hours sometimes seems like a relight! Compared to long flights in power planes (boooring, unless at 500 ft and 500 knots, or 100 ft and 100 knots), it always amazes me how fast 6 hours can go by on a really fun (fast, high, low stress) soaring flight. On the other hand, anything over an hour in an uncomfortable (physically) glider is torture. I really enjoy flying 1-26s, but almost all the ones I've flown have been rentals and none have fit very well - so there was never any problem in deciding to land after an hour or two. Water? Because it feels so goood! Like a big heavy Cadillac, cruising along nice and fast...and faster means you can cover more ground and see more scenery before you land, not to land earlier. Finally, a 500 k downwind is a lot more of an endurance test than a 500 k O&R - that 500 k drive back is really tiring! Kirk |
#15
|
|||
|
|||
On Sun, 31 Jul 2005 21:31:36 -0700, ttaylor at cc.usu.edu wrote:
I am working on the planning for a 1000K attempt. One question I have is how much water should I launch with in my Ventus B? I can carry up to 40 gallons (150 liters), but for a 1000K flight I will need to launch in early weak conditions, followed by strong conditions latter in the day. Plan your flight in advance. Start with the number of flying hours available in the day, select your take off and landing times, average speed on each leg and ETA for each turn point. Then based on the required average speeds, you can estimate what thermal strengths you will need and the optimal wing loading. Obviously you have to carry the water ballast from launch. The details will depend on your location, aircraft, personal skills etc. Certainly they will look different in Norway to South Africa. For a 1000km task in a 15m glider, you will need to plan for strong lift, or a long day, or both. You will probably need to fly close to max AUW. Write down the flight plan and carry it in the cockpit so you have a target to measure your progress against during the flight. You will discover that you have very little margin for loosing time. Most important is a cut off time for your last turnpoint. If you fall behind schedule and can't make the turnpoint by that time, then turn short, go home and try again the next day. If you push on and land out, you will probably not get home in time to attempt another big flight the following day. (Motor glider pilots have an advantage, they can push on to the point where they have just enough daylight to motor home before sunset.) One tricky decision that you are almost certainly going to face, is what to do if you have taken a launch with a heavy water load, and you find you can't stay up. Do you dump some water, stay airborne and jeopardise the rest of your task or risk a landing with full ballast in the hope of getting airborne again while there are still enough hours in the day to complete the task. If you dump all the water and land, by the time you have filled it again you will have lost too much time. Motor gliders have another tactical advantage over pure sailplanes in this aspect, they can launch early and use their motors until conditions are good enough to stay up, then start their task. One last comment, if the day is good for 750km but not 1000km, you will probably achieve a better distance if you declare and plan for 750 than if you go for the 1000. But on the other hand if you don't go for the big one, you will never get it! Have fun! Ian |
#16
|
|||
|
|||
At 04:24 03 August 2005, Eric Greenwell wrote:
I'm sure that's good advice for Tonopah and other strong areas, but I don't think it will work here in the Pacific NW. Tim will need to experiment some, and, I hope, report back to us in a year. Always good to know how conditions develop at your intended site. There are 'speed sites' where the length of the day is the limiting factor rather than the strength of the day. At these sites loading up will help you get home before sunset. Apparently there are sites in the northern latitudes where the conditions develop slowly (e.g. narrow, 1-2 knot thermals for several hours before noon), then get strong later. In these cases it may be optimal to go with little or no ballast. I've never seen a day like this, but maybe that's because I fly further south where the days 'pop' to a significant portion of full strength when you reach trigger temperature. Also, in places like the Great Basin, you'll often find the high ground working (full strength) an hour or more before the valleys get cooking, so a well-placed tow release can help a lot. 9B |
#17
|
|||
|
|||
Try taking off with full water and dumping early only if absolutely
necessary to sustain. Dino taylor at cc.usu.edu" wrote in message oups.com... I am working on the planning for a 1000K attempt. One question I have is how much water should I launch with in my Ventus B? I can carry up to 40 gallons (150 liters), but for a 1000K flight I will need to launch in early weak conditions, followed by strong conditions latter in the day. Options would be to launch with 20 to 40 gallons. Twenty to thirty would probably give a good balance for early climb and later running. Any suggestions for an optimum balance? Thanks, Tim |
|
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Airbus A380 water purification | john smith | Piloting | 1 | July 7th 05 02:50 AM |
Induction System Water Problem | Mike Spera | Owning | 1 | January 30th 05 05:29 AM |
Water, water, everywhere, but none for thirsty wings.... | Chris OCallaghan | Soaring | 0 | November 21st 04 03:14 PM |
Questions regarding Air/Oil Separators | Doodybutch | Owning | 6 | April 20th 04 05:56 PM |
Water Cooled Jet Engines: a possibillity then and now? | The Enlightenment | Military Aviation | 3 | December 18th 03 09:41 AM |