Posts: 435
Joined: 12/11/2001 From: oberndorf, AUSTRIA Status: offline
right side viewfrom the Cap 222, in the background the full size aluette 3 from the turbine manufacturer peter jakadofsky, who did a stopover to help the setup procedere.
the turbine is an autostart unit. first start was without mishaps. as soon as the starter revs up the turbine, the prop starts slowly to turn. rpm of the turbine increases and you see and hear that the prop does not follow the acceleration of the turbine until it revs 37.000rpm. over 37.000rpm the clutch engages and the prop follows the increase in revs. at 80.000 we measured the prop at 5200rpm. at this time pitch was 0°. this data we reached after several tries of balancing the prop however. it was evident that the prop was not balanced properly.
our next concern was the temperatur in the engine and exhaust cowl. but the testruns showed that we will not expect any problems (the future will show). everywhere on the fuselage, the engine cowl although near the exhaust pipe, you can lay your hands on. seems to be a healthy airflow through these compartments. interestingly the right wing, next to the fuselage, showed a slightly temporarely darker coloring of the film covering. apparently the exhaust pipe blows the gases horizontally to the right, maybe the left one a little bit more upright or ascending. eventually i will make a new y-pipe, eventually with a thrust factor backwards too.
we had no possibility to measure thrust. but with the increase of pitch, so did thrust. these tests had been necessary to approach our limiting factor, the EGT. till now the display shows 600°C, we should not exceed 640°C. the man holding the plane said, that the trust was nearly comparable to his 3W 60ccm Extra 300. seems to be a good base to bring it in the air.
next test runs will follow soon, hopefully with a better balanced prop.
mpeg of the start sequence, rollout and first flights will follow.
Posts: 435
Joined: 12/11/2001 From: oberndorf, AUSTRIA Status: offline
hi
sorry, but the plane crashed after take off.
from the beginning: today, in the morning i balanced the prop and added 400 milligramm to blade 1, and 800 milligramm to blade 2. our goal was to check the balance of the prop during full throttle test runs. again i adjusted the play between the gearwheel of the propshaft and the clutch.
I'm sorry to read this, I thought these things only happened to careless guys like me. Is it a total or what dammage you got? I hope it won't throw your moral down, you have a spectacular project and I'm folowing its developement like many other guys as you can see.
Posts: 435
Joined: 12/11/2001 From: oberndorf, AUSTRIA Status: offline
early afternoon we arrived at the flying field. several engine starts succeeded without problems. the first full throttle runs showed that the balancing of the prop was done properly, although not perfect. seems that our simple static method, as seen in the picture above, would not allow 100% results. but without doubt the balancing would allow to think of first flights. next we reduced max pitch because of the doubt of overheating the engine, which showed to be the great mistake. max pitch thrust on ground seemed to be enough for take off and comfortable flight characteristics. short acceleration test followed. they seemed to be ok for our 120meter gras field. once again refuelling for first flight. sunny weather, 19° celsius, light cross wind from the right, take off should not be a problem. engine start once again without any problem (never seen a turbine engine with autostart with such a lot of starts without a hotstart or another bothersome failure). plane taxied to the beginning of the runway. first half of the acceleration phase was ok, but in the second half it did not gain speed really much. yes, it was not slow, but everything else than fast. take off, but not enough speed, right turn against the wind. nevertheless one wing dropped, then the other. pilot ernst managed to level the plane and did a hard landing in a high gras field. kill switch for turbine immediadetly, fire extinguisher in case of fire. but we had luck. approaching the plane, i heard the autocooling of the starter, so i asume that there was no damage to the engine. the complete handmade pitch prop mechanism however was destroyed. landing gear broken, enginefirewall has minor damage, as has one wing.
following inspections (planed for one of the next days) will show maybe more damage. all in all, we had luck. i think next flights will follow in some weeks. manufacturing of the pitch mechanism will take at least two weeks.
how could this happen? suggestions appreciated. to my mind there are two major facts worth considering: # the plane was too slow. in order to do no damage to the turbine (overheating) we reduced max pitch so much, that it was enough for ground thrust. but at the moment, the plane gained speed, there was no pitch left over to compensate the reduced thrust (how do you call it? learning by doing ) # certainly our full symmetrical profil, airfoil of the prop blades are not the best choice (nevertheless helis fly with similar bladetip speeds).
thats all for the moment sorry, that i had no good news today thanx all for their interest
as soon as there are first videos online, i will post the url
Hi Mec, Really sasd to hear the news, but don't worry, you'll have her ready and flying any day. I once crashed my trainer, and thought that I would never get tho fly again, as it was really bad, but, the next day I flew it again!!! I have to say, that your prop might not be the best, but I have no experience with Turbo Props, so I wouldn't know. Did you think about using a normal 2/4 blade? Again, I am not very familiar with the advantages/disadvantages of the one you used now. Well done though, as it has to be one of the coolest planes in the world. (Please note though, that as a Juan Pablo Montoya supporter, I cannot approve of your colour scheme! Just kiddin, its cool.) Go get it fixed!!! Robert.
Posts: 2472
Joined: 1/19/2002 From: Anchorage,
AK, USA Status: offline
Hi Mec,
Fantastic!
I'm watching with great interest, and see that you're making progress all the time. This is a VERY cool development for our "hobby", and I hope you continue through these complications.
I'm not a propeller expert, but it seems to me that this is an area that might call for a little more help from a great machinist. A prop that big, on such an expensive project, should really be done right, and I'm sure that someone can help you solve that problem... I'm thinking one of the turbine guys might have the machining capability (if you don't) to help you make a first class propeller that will do the job.
Keep up the great work, and keep us informed. What you are doing is great!
_____________________________
Mike James RC Design and Building - www.nextcraft.com
Posts: 281
Joined: 1/22/2002 From: Bend,
OR, USA Status: offline
Well the plane turned out looking fantastic and like you said, you did learn something! I have no doubt that you will be able to get that plane working very well! Can't wait for the next "episode", and i also agree, this has got to be one of the coolest RC planes i've ever seen.
Glad to hear that you haven't let your spirits drop too much. Good luck
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