ORIGINAL: camdyson

Question is, what led these guys to even think it WOULD fly in the 1st place?! Looked alot like an F1 race boat lifting off.....similar result too.[:@]

ORIGINAL: drunkenbushman

Yea i watch RC Hobbies but i find they Chris Chianelli does more on cars than planes. Its only on once a fortnight here in Aussie Land but i record it and watch every episode.

ORIGINAL: AQ500

That had to have been the maiden flight of the F-117 in that video. If you watch the video closely and then look at the picture countryboy posted you can see exactly why it crashed. Infact, I knew how it was going to crash before the flight.

If you watch the video and pay attention to the engine exhaust outlets you can see that they vector the thrust up by about 25 degrees. Between 52 and 55 seconds into the video you can really see it. There is no way the plane would fly controlably like that.

Notice in the photo:

http://image.rcuniverse.com/forum/up...09/Vt56676.jpg

You can see that the exhuast section has been modified to straighten the flow.

It would be interesting to know why the plane was originally built like that. Was it a mistake or was there a purpose behind it? (Maybe to hide the exhaust openings from below when flying overhead?)

ORIGINAL: Daren Savage


They had a smaller one which flew successfully many times. There was quite a bit of discussion at the time as to the cause of the crash. Some felt there was some issue with the radio which caused the ailerons and elevons to deflect up fully. I can see this when viewing frames from the rendered video. The original videographer disputed this alligation, but never posted high-res screen grabs to disspell that assertation.

Many in the jet forum, felt that for this to happen somehow pointed to some failing by the test pilot, whom I know to be a highly skilled stick and rudder man. Personally, I like to use video to help with the debriefing and find the root cause of a crash when they happen, but some don't. I don't feel pilot error to be the root, but some issue with radio interference, but we may never know.

Daren

ORIGINAL: AQ500

Understandable.

Not to beat a dead horse....but

I don't think it was the pilot's fault at all. The pilot most likely pulled back to rotate the plane and it over-rotated and suprised him. That would be why you can see the upward deflection of the elevon. He may have held it from for two reasons. Being suprised by the excessive pitching and maybe by habit. Sometimes a pilot will freeze when the plane does funny stuff, but in this case the pilot was much better than that. As it comes over the top most pilots would pull up to try and finish the loop and not pile into the ground out of instinct. So the upward deflection seen would not be out of the ordinary.

There are three reasons that I think the vectored thrust caused it. First the modification in the photo. It is evident that the exhaust manifold was modified, smoking gun. Second, the plane pitched up at a faster rate than I would think possible with elevons alone on a jet. As the plane looses air speed the plane continues to pitch around until it finally gets to where the speed is too low and the angle of attack too high and it falls to the side. Highly swept deltas like that can fly at a higher angle of attack than other planes (Watch the Concorde landing, pretty cool). The exhaust is coming out of the rear and there is no wash over the control surfaces, so at a low airspeed the control surfaces would have little authority. The vectored thrust would be in control. Third, there is no way that you could fly a model with the thrust vectored like that. That would be like mounting an engine on a any plane at a 25 degree angle upward or downward and then expecting it to fly well. All you need to do is find the cg and guesstimate the center of drag and then draw a thrust vector. You would see that the moment caused by this would make the plane impossible to have a controllable pitch. I'm sure the smaller one had different geometry or was not vectored as much and was severly nose heavy to counteract it. If it had somewhat like geometry and was seriously nose heavy to counteract it, there would have been a serious pitch trim problem and the controls would have not been very effective. But without seeing it there is no way to know.

Sorry, that's all I'll say. I'm sure it has been debated enough already.