Thursday, November 1, 2007
The Badaling Challenge!
Originally we had planned to drive to the Great Wall at Jinshaling (app. 160 km West of Beijing) rather than Badaling. The latter is much more overrun by tourists, and this is exactly what you would not want for R/C helicopter flights. However, Ken Yap thought it was possible to pull off the stunt at Badaling, and this would save us about 1.5 days of extra time which we really needed for finishing the latest ROTOR article, the blog, data backups, email communication, and for repairing equipment; our heli transport box had gotten a heavy blow on the way from Singapore to China.
Thanks to the help of some nice local guy we got a good taxi flat rate to Badaling; they drive like they queue up - all lanes are in use, and it's an overtaking (doesn't matter which side) and squeezing back in all the time, especially during heavy traffic or jams. 'Congratulations!' one thinks, 'it's now one million less one car in front of you!'
Badaling really is a tourist place. We took the cable car to the top of the hill (quite hard to take a big 90size heli with you!) and went straight onto the Great Wall - and that's definitely what it is! The structure has been built and rebuilt over centuries starting 500 BC and stretches over app. 6,700 km.
We were lucky with the weather - the day we arrived it was fog everywhere, the next two days (including our trip to the wall) were sunny, and after that it got extremely cold plus stormy. So at reasonable temperatures of around 10 °C and light wind blowing up the hill we lugged 15 kg of equipment up and down this huge structure. Quite exhausting as there are almost no horizontal sections; on the contrary, sometimes it gets close to climbing up and down vertically. People often couldn't really believe why somebody would take such bulky equipment to this place and even cheered on us when we got stuck in one of the vertical sections. Funny.
The big problem for heli flying is that you will need a horizontal section to both take off and land. And it does neither help you if this is kilometers away nor when it's down in the "valley" and thus not giving you a good view.
After an hour of walking we nearly dropped dead at some good viewpoint. We were sweating like hell; this means you have to take extra care not to catch a cold when stopping all of a sudden. Of course the heli bag drew the attention of the people around plus a guard. We found some English speaker who helped translate what the WSF project was all about. There was no way around this as the Great Wall is just about 3.5 m wide and we'd have to block it for the flights (We're not sure if anybody has blocked the Great Wall in the past 100 years or so?!).
Quick calculation: 3.5 m - 1.60 m rotor diameter = 1.90 m. Two handrails on each side, app. 25 cm off the wall, that's 1.90 m - 0.5 m = 1.40 m. Divided by two gives you 70 cm clearance to each side. Since the ground is quite uneven, you may have to land a little more to the left or right, depending on how the heli comes in. Add to this a constant breeze plus a tree hanging half over the area, and there you have it: The perfect spot for take-off and landing! Did we mention we had just lugged 15 kg of weight around for an hour? :-)
After some negotiations we actually got clearance for our remote-controlled toy. Someone asked what happens if he put his hand into the rotor disc. Well …
Most of the people visiting the Great Wall were Chinese, not foreign tourists. And it was the same problem with people just squeezing through narrow spots instead of queuing up. One guy even managed to fall over the helicopter in its carrier bag while I still had it over my shoulder (just don't ask …)! Consequently, we got a little worried somebody might actually fall into the rotor disc after the landing. Our translator was a big help, and we had him make extra clear to the guard that the area needed to be entirely clear when the machine came back in.
OK, take-off! There was no way to test the heli after assembly this time, so we just gave it a try. Add pitch, and --- it leaves the ground and sits in the air. Smooth and stable, as always. That's a Henseleit, one thinks, and slowly adds fore cyclic and right aileron to leave the wall and fly out to the countryside. As expected, all the spectators now gather around you and make it hard to walk over to the camera. One wrong step and you will fall about 30 m down the stairs - the descent is nearly vertical (you will see it later in the video)!
The flight was interesting in many ways. Not that we complain about people blocking our vision or jostling against us, but there was quite a breeze coming up the hill. At just over zero degree pitch the heli was still climbing towards us. You had to be careful not to fly into the occasional invisible tree that had already lost its leaves. Once the heli has nearly reached your position, do a combined ail/ele flip and let it dive down the wall inverted backwards, just a little offset so it won't hit any people in case something goes wrong. Finally morph the slide into a large diameter funnel, and that's it for today.
After repeating and modifying the exercise a couple of times we pull out the photo camera and shoot dozens of pictures within just one minute. We know there won't be a chance for a second flight, and you have to allow for 2 - 3 minutes of landing. No surprise the walk back to the landing area took a while and it was a nightmare getting the people out of the way. Then slide in the machine and touch down fast. The moment when it goes below the height of the smaller side walls is critical because it loses lift and you have to stop compensating for the side wind all of a sudden. But no problem this time, it lands as smoothly as ever, and it's just a matter of keeping the people from jumping into the rotor disc now.
Since the Great Wall was pretty crowded everywhere, attempting to shoot an AFD panorama was hopeless. It wouldn't have made much sense anyway since the only spots suitable for at least a heli take-off and landing were bad for flying because the pilot cannot change his position (like we had to) in the simulation. So we walked another 40 min. until we found a reasonably good location. Let's see what Ikarus/IPACS will be able to make of it.
The last shock came when we discovered we had ended up on the other side of the hill where a train goes up to the wall, and not the gondola! We called Ken Yap in Singapore, and he called our Chinese only speaking cab driver; the driver claimed there was no way around the hill. Uuups!?! Should we really have to walk back now for two hours with all that baggage ("queuing" up for the train would have taken the same time plus also walking for 30 min.)? I had a feeling the heli would not survive that trip – and we wouldn't, either.
Saskia volunteered to recheck if there really wasn't a way around the hill by car. 20 eternal minutes of pointing and gesturing later we found someone to drive us (may God decide what will happen to the lost soul of our cab driver …). Phew …
We're on our way to Seoul/South Korea - we originally wanted to slow down a little. But unfortunately, the next problems are already shaping on the horizon … We'll keep you updated!
Labels: AFD problem, Badaling, China, crowd, Great Wall
# posted by hg/tuw @ 15:18 
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