Before Charles Lindburgh flew a glider, he was advised by the man who taught him never to turn in a down draft.
An aviation journalist of the time tried to explain the reason to his lay readers.
"In making a turn," he wrote, "the glider customarily loses altitude; and if a turn is attempted while in a down draft, the glider suffers a double loss -- the normal loss of altitude by the plane itself and the sinking due to the air moving downward."
Do you consider this explanation correct or adequate? Do you believe this was the concern of Linburgh's tutor? Do you or would you turn in a downdraft? Has this been a problem for hang gliders in the past?
RickMasters (with Bob's numbering added wrote:Before Charles Lindburgh flew a glider, he was advised by the man who taught him never to turn in a down draft.
An aviation journalist of the time tried to explain the reason to his lay readers.
"In making a turn," he wrote, "the glider customarily loses altitude; and if a turn is attempted while in a down draft, the glider suffers a double loss -- the normal loss of altitude by the plane itself and the sinking due to the air moving downward."
1. Do you consider this explanation correct or adequate? 2. Do you believe this was the concern of Linburgh's tutor? 3. Do you or would you turn in a downdraft? 4. Has this been a problem for hang gliders in the past?
I fear that I'm going to expose some aeronautical deficit of mine by attempting to answer , but I'll be brave and give it a try anyway ...
If you need to turn, then any altitude loss due to the turn will be suffered one way or another - whether you're in lift or sink. However, the reason you generally don't want to turn in sink is that you'll be spending more time in that sink while completing the turn. In general, you want to minimize your time spent in sink and maximize your time spent in lift. Joe Greblo described this as a specific example of the rule to fly slow in "good air" (lift and tailwinds), and fast in "bad air" (sink and headwinds).
So based on that, here are my answers:
1. I would not consider his explanation correct or adequate. 2. I don't know what was on Lindburgh's tutor's mind, so I don't know if it was just a miscommunication or not. 3. I would avoid turning in a downdraft as a way to minimize my time in it ... all else being equal. 4. I would guess that it's been a problem for hang gliders who didn't know about it and wanted to stay up.
OK, Professor, how did I do?
P.S. to Joe Greblo: Your words of wisdom will always be with me!!!
Join a National Hang Gliding Organization:US Hawks at ushawks.org View my rating at:US Hang Gliding Rating System Every human at every point in history has an opportunity to choose courage over cowardice. Look around and you will find that opportunity in your own time.
"Before Charles Lindburgh flew a glider, he was advised by the man who taught him never to turn in a down draft. An aviation journalist of the time tried to explain the reason to his lay readers. In making a turn," he wrote, "the glider customarily loses altitude; and if a turn is attempted while in a down draft, the glider suffers a double loss -- the normal loss of altitude by the plane itself and the sinking due to the air moving downward." 1. Do you consider this explanation correct or adequate? 2. Do you believe this was the concern of Linburgh's tutor? 3. Do you or would you turn in a downdraft? 4. Has this been a problem for hang gliders in the past?
Well, it's almost like a trick question, but if you glide on a straight path through sink "the glider suffers a double loss -- the normal loss of altitude by the plane itself and the sinking due to the air moving downward" -- all true, so why bring up the turn? Does the turn itself effect even more the loss of altitude? (Answer: Not by much with a gentle turn - but it can look like it does when the sink is strong.) What if you wanted to perform a 180 and head back to your last area of lift? Clearly, the explanation is inadequate. But remember, the explanation was provided by an aviation journalist, not a glider pilot, and there were very few people in the U.S. in those days who were anything but power pilots. The principles of gliding were mostly a mystery.
The greater danger of turning in sink has to do with pilot error. The history of hang gliding provides a poignant lesson when we look back on pilots in the early 1970s learning to 360. A lot of pilots were killed or injured (unnecessarily!) when they entered a sideslip on their downwind quarter and fell out of the sky. There was no good reason for this. The pilot did this to himself. A pilot can execute a proper 360 in any type of glider. The glider doesn't care if the air is sinking or climbing. It simply needs to maintain flying speed at the proper angle of attack. (Understanding this, I learned to 360 using a Hall wind meter and never had any problem.) But pilots new to turning near hillsides would concentrate on their apparent ground speed - which has NOTHING to do with flying at all. Thinking they were flying too fast, they would approach stall. Then their inner tip (which has the slowest airflow in a turn) would stall and the glider would enter a sideslip. Their response to the sideslip, with the ground coming up fast, was then to push out. But this only aggravated the slip and they would hit the ground in a steep spiral with a strong sideways vector.
I am not a sailplane pilot but I remember reading John Lake, in an early Ground Skimmer, saying sailplane pilots were astounded to see hang gliders execute 360 near hillsides. Sailplanes didn't do that. It was too dangerous. Sailplanes did figure eight Chandelle turns parallel to the slope.
Sailplane designer Hawley Bowlus, who had built the "Spirit of St. Louis" and now provided Lindbergh with his own SP-1 Paperwing sailplane, understood the difference between Chandelle turns in power and unpowered aircraft. He knew that a power pilot, new to soaring, would be at a disadvantage when he first attempted a Chandelle in ridge lift, not only because the throttle no longer played a role, but the effect of torque, which a power pilot would be keenly attuned to -- and which made a significant difference in the pilot's input for right or left turns -- was missing.
Probably the greatest concern Bowlus had was that Lindbergh, filled with chutzpah from his recent Atlantic crossing, would get himself into trouble trying maneuvers close to the ridge. If Lindbergh crashed, Bowlus knew that his sailplane and his reputation would also be ruined along with the loss of the famous aviator, so he advised him to at least fly through and out of sink to ensure that any Chandelle turns Lindbergh might attempt be done in lift.
Last edited by Rick Masters on Mon Dec 29, 2014 10:14 am, edited 1 time in total.
Excellent topic and excellent presentation Rick. I hope my response didn't detract too much from your point.
This is exactly the kind of topic that will be helpful to pilots entering the sport and maturing in their aviation knowledge.
P.S. That X-Plane simulation was also excellent. It turns out that I used X-Plane on a research project about 4 years ago. At that time we were working to demonstrate artificial intelligence principles in decision making, and we chose airplane landing as one possible application. So we purchased X-Plane (it wasn't cheap), and wrote the software to interact with it via its UDP packet interface. I started by writing the code that would create a separate "pilot's interface" in Java. It would show me a simple instrument panel and I could use the keyboard and mouse to fly it - all via UDP packets shipped back and forth to X-Plane. Once that was working, then I worked on the artificial intelligence portion that would learn the relationships between the situation (sampled instrument values) and response (my own controls when flying). As the "trainer", I just spent a lot of time flying the simulation over the UDP interface and allowed the network to observe what I was doing and how the airplane responded. Then when I directed the "artificial pilot" toward some result, it would use the mapping it had learned by observation to decide what control inputs would achieve that directed result. It actually worked as a prototype, but we ended up focussing our limited resources on other projects at that time.
Thanks for the reminder about X-Plane. As your video shows, it would be an awesome way to package and present hang gliding training materals!!
Join a National Hang Gliding Organization:US Hawks at ushawks.org View my rating at:US Hang Gliding Rating System Every human at every point in history has an opportunity to choose courage over cowardice. Look around and you will find that opportunity in your own time.
To me that sounds like advice for soaring a ridge. Reworded: Wait for lift to start your first "180" - unless you've run out of ridge. WIth no ridge left and no lift there's little left to do but fly straight for the beer.
Thermals are different matter. If you've flown out of lift into strong sink, it's probably time to tighten your turn.
That might be a better way to build flight videos for the training manual than Blender's animations. I went to x-plane.org and searched for hang glider models with this result:
http://forums.x-plane.org/index.php?app=downloads&showcat=1 wrote:There are no files directly in this category. Files listed below are from this category's subcategories, or you can click on a subcategory in the menu to narrow your results
They may not have hang gliders because weight shift control may be incompatible with their simulation. Even so, just putting a hang glider "skin" on a conventional airplane would enable us to generate some good looking simulations. This might be another good topic for the "Technology" forum.
Join a National Hang Gliding Organization:US Hawks at ushawks.org View my rating at:US Hang Gliding Rating System Every human at every point in history has an opportunity to choose courage over cowardice. Look around and you will find that opportunity in your own time.
Merlin wrote:To me that sounds like advice for soaring a ridge. Reworded: Wait for lift to start your first "180" - unless you've run out of ridge. WIth no ridge left and no lift there's little left to do but fly straight for the beer.
Thermals are different matter. If you've flown out of lift into strong sink, it's probably time to tighten your turn.
Good points. Gary Fogel's book mentions Charles Lindbergh flying a glider through the lift at Torrey Pines. So when I think of Lindbergh and gliders, that's what comes to my mind (ridge soaring). But you're right that it wasn't explicitly stated in the original post.
Join a National Hang Gliding Organization:US Hawks at ushawks.org View my rating at:US Hang Gliding Rating System Every human at every point in history has an opportunity to choose courage over cowardice. Look around and you will find that opportunity in your own time.
Hawley Bowlus had not yet successfully soared in a thermal when he counseled Charles Lindbergh in 1930, just before he was awarded the second NAA gliding license.
https://www.flickr.com/photos/sdasmarchives/9579337216 This the soaring school Bowlus operated in San Diego in the 1930s. The event is a meeting of the Anne Lindbergh Gliders of San Diego. Talk about getting people excited about flying gliders! Note the two Bowlus SP-1 Paperwings in the foreground and the primary training gliders in back. Look at all the excited young people! Fantastic. I think that's Hawley in the white shirt. That would be the old Point Loma Lighthouse in the distance.
Last edited by Rick Masters on Mon Dec 29, 2014 2:56 pm, edited 1 time in total.
Hawley Bowlus had not yet successfully soared in a thermal
Yes, I believe that. When I started flying in the seventies our club was just sort of figuring out how to thermal. In fact, most of what we had been calling "ridge soaring" was probably just bumbling through thermals on the ridge.
That is a remarkable photo. Those open cockpit gliders look like a lot of fun. Some real country boys and business suits.
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, but I'll be brave and give it a try anyway ...
