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Discussion in 'After Hours Lounge (Off Topic)' started by Andy_S, Jun 2, 2004.
Very impressive, all the same!
thought I'd bump this, the video is back up! more info http://www.mcgirt.net/RC/VIDEOS/Giant_B52/ video http://www.mcgirt.net/RC/VIDEOS/Gian...52_flight2.wmv
Now that's what I call entertaining the troops!!
Holy crap, the sound of that thing is amazing, if you didn't see it sitting beside the men, you'd think it was real!
It does sound sweet! It's probably the first time I've ever heard an RC model sound very much like the real thing!
I looked up the price on those engines, it worked out to about 6800 USD each with the current exchange rate
The current issue of Air & Space Smithsonian (September 2004) - my favorite magazine - has an excellent article on RC model jets. Wished this B-52 was included.
Very cool, and for some reason, I think I'd be more uncomfortable controlling one of those than I would be piloting a real plane. Also of interest, check out the extras on "Empire of the Sun" DVD. Speilberg used model RC's in some of the air raid scenes to great effect. I didn't even realize that until watching the 'making of'.
That video was absolutely unbelievable.
I found this video on military.com: it's a F-14, complete with GREASED landing! It is possible. http://www.xmission.com/~knhmeads/F-14.wmv
Well, I'm afraid its success was short lived. http://www.teambanana.co.uk/b52crash2.wmv
Ouch!! Looked like it had some control issues from the outset of the takeoff. Much less stable than the other video. I noticed the dark clouds and wonder if there were some iffy winds?
I think it was a little gusty. from the lighting and the clouds I wonder if he lost track of the airplane's attitude with a sliver a/c against a silver sky and just let it roll into an attitude he couldn't recover from. B52 isn't known for it's aerobatic prowess...
That was heartbreaking...... Did look (and sound) gusty. Hopefully they were able to salvage enough to make another go at it ! >>>>>B52 isn't known for it's aerobatic prowess... Anyone catch the video of the real B-52 that tried to perform a tight turn at an air show ? Banked way too high, lost all lift and slid right into the runway, wingtip first. Tragic, but apparently the pilot was known to be a "hot shot". Too bad he had to take his crew with him.
He wasn't trying to turn, he was trying to do a roll. He had a history of doing stupid things. A lot of them on video.
I really feel for the folks who lost a marvelous work of modeling art. That was to me one of the most impressive model aircraft I’ve even seen. I hope they can salvage enough to rebuild. Looking at the video of the crash, it looks to me like they forgot some very important facts when dealing with exact scaled aircraft. First of all, the thrust from those gas turbines was I believe only about 12lbs each. That’s not even close to scale of the real thing being many thousands of pounds each. This would be done simply to make the aircraft flyable from a third point of view on the ground. This also would give the plane a more graceful appearance while in the air. The downside is that the plane can never truly achieve its designed cruising speed and would always be flying at or near stalling speed. Secondly, an airfoil can only provide maximum lift when it is parallel to the ground. When an airfoil is tilted at an angle to the ground it loses lifting ability by that same factor. In other words, if an aircraft makes a 45° turn (or half way to vertical) then the plane can only depend on its wings to provide 50% of its normal lifting capability. When that B-52 made its fatal turn it looked to me like it was at nearly 90°?!? to the ground. At that point the airfoils would cease to work altogether and the plane would have to rely solely on the brute force of its engines and momentum to keep it in the air. Lastly, I believe the weather made a significant contribution to the crash. When one scales down the size (and thus its aerodynamic lifting capability) of an airplane you also need to scale up any kind of weather conditions it will be exposed to by the same factor. For example if one is building a “1/5 scale” aircraft then one must also multiply any weather conditions your craft will be exposed to by a factor of 5. In this instance I would think its safe to say on this attempt there was a good 15 mph wind with maybe 20-25 mph gusts. Scaled up by the reverse of the crafts scale (I estimate ¼-1/5 scale) and I think they were easily flying in 100 mph+ scaled conditions. On take-off when they were heading into the wind (also when they made the first turn) this would be a benefit as the airplane would need to be traveling at 100 scaled mph slower than normal to execute these maneuvers. However, when the plane made its fatal second turn, the craft was flying with a 100+ mph tailwind. This reversed the minimal requirements to perform this maneuver from 100 mph slower than normal to 100 mph FASTER then normal. This is a 200 mph change in aerodynamic requirements inside of a few seconds. When this happened and you add the factor of the extreme angle of attack of the airfoils and the gross lack of engine power, the aircraft lost all ability to stay in the air and simply crashed to the ground.
Not entirely true. A more accurate description is that lift acts perpendicular to the wing, while gravity always acts downward, towards the earth. So, as you roll into a bank more and more of your lift is used to turn the airplane, and the vertical component of lift becomes smaller and smaller, it's not too bad up to 45 degrees, but beyond 45 degrees it increases sharply, the load factor on the airplane at 60 degrees is 2 G's, at 70 degrees it's 3G's. "lifting ability" isn't changing, nor is the amount of lift generated, it's actually increasing if flown correctly. It's simply that the vertical component of lift, used to counteract weight, is decreasing, while the G force is increasing. I don't feel that this airplane was incapable of flying in a 45 degree bank, if it can take off, it's capable of a steep turn. Part of what happens in a steep turn is called the "overbanking tendency" Since the outside wing is traveling a further distance than the inside, it's traveling faster and generating more lift, causing the airplane to want to roll into a steeper bank. I seem to remember the airplane rolling into the turn at about the midpoint before spiraling down. Also, you speak a lot of scale, while the size of the airplane is to scale, the weight probably is not, as that is not steel, but lightweight balsawood. 12 pounds of thrust times 8 is a lot of thrust for a 300 pound model. The 'real" B52 is 195,000 pounds empty, and has a maximum takeoff weight of 488,000 pounds, yet has 136,000 pounds of thrust. that's 3 pounds of weight for 1lb of thrust. The model has 96 pounds of thrust and weighs 300 pounds, that's 3.125 pounds per pound of thrust, hardly underpowered. They could have also been the newer wren engines with 14 pounds of thrust, tough to say.