Sig Rascal 110 #1 – UMN UAV Project
Next steps …
- Come up with a better solution for securing the tank.
- Redo top nose cover job?
- Cut and fit cowl.
- Purchase replacement windshield (?)
October 20, 2006.
This morning I re-maidened Rascal #1. I had to work through some minorhardware issues, but the structure and rebuild all held together well,and the airplane flew straight and true and as good as it ever has.I’ve very happy with the outcome, and very glad to have this airplaneback on active flying status.
October 19, 2006.
This evening I ran the engine for the first time after the crash. Everythingseemed to perform well. I think I may try to re-maiden tomorrow if the weather is ok.
October 2, 2006.
The battery and reciever and crystal arrived today. I tested to makesure they all work. I brought the aircraft home this evening andmounted the receiver, battery, and volt-watch unit. I still need to secureantenna. I’m running out of things I can think of todo before test flying!
September 29, 2006.
Begin putting the damaged right wing back together. I epoxied thewing joiner box back together so it is secure again and then a rebuiltand sheeted the first inboard section of leading edge back to the mainspare. Finally I sanded and covered it and (tada!) the wing is done!
We are *really* close to being ready to fly! Just waiting on thereceiver and battery now. I will cut and fit the cowl after wesuccessfully test fly and after I’ve regained my confidence in thisengine.
September 28, 2006.
Mixed up some epoxy and sawdust and used that to fill in the shatteredend of the right wing strut. I sanded this down to shape, redrilledthe hole, and threw a quick coat of white paint on it. Good asnew. 🙂 Here are before (damaged) and after (fixed) shots.
September 27, 2006.
Installed the engine and muffler.Reassembled and installed the main gear. Cleanedup the wings in advance of inspecting and repairing them. Inspected thedamaged wing strut and determined it is fixable.
September 26, 2006.
I recovered the front of the fuselage in white monocote. The top of thenose didn’t turn out nearly as well as I had hoped so I may cut that offand redo. We ordered a receiver and battery. I reinstalled the tailwheel assembly and the canopy.
September 25, 2006.
Test mounted the engine and rigged the throttle linkage. Next step is tocover the front of the fuselage.
September 22, 2006.
Worked on installing the fuel tank. Routed the throttle linkage housing.
September 19, 2006.
Secured the front wing support (where the wing dowls plug into.) Gluedin forward cabin support rods.
September 18, 2006.
Epoxy seal/paint the outside firewall.Filled in some of the gaps/cracks with balsa filler.
September 15, 2006.
Today I glued in the top nose support stringers. Then starting with thecracked up nose sheeting from the original, I drew a rough template of theshape the sheeting needed to be. I transfered that to 1/16th sheeting anddid some test fitting and trimming. Finally I squirted it up with windex which was what I had on hand and the sheeting pretty much melted around the curve …cool. 🙂 The final results looks better on the left side than on the rightbut I guess that just means I need to do a little filling and sanding.
Posing with the cowl and the cabin support rods.
September 14, 2006.
Reinforce left front nose side splice internally with some hardwoodsquare stock.
Finished sheeting both sides of the front fuselage (i.e. sides of the nose.)
September 13, 2006.
Reinforce wing leading edge bulkhead reinforcements. I’m compensating herefor an earlier mistake where the bottom portion of these reinforcments didn’tget clamped in where they should have been and thus there is some ugly gaps.It will be non-visible when the fuselage is all sheeted, but I just wanted tomake sure it’s solid structurally.
I installed (and tack epoxied) the engine mount blind nuts onto the backside of the firewall. These are a horrible pain to deal with once everythingis sheeted in … probably the hardest part of assembling the stock Rascal.So they are installed now and I don’t have to worry about them later.
Finally, I cross sheeted the bottom of fuselage forward of the main gearblock. This adds a surprising amount of rigidity to the nose section whichis what I was hoping/planning. I also attached the original sheeting to therear of the main gear block. (Little details …)
September 12, 2006.
Today I spent a few moments fabricating and installing the firewall sidereinforcements. I also fabricated the nose top stringers.
September 11, 2006.
Today I glued in the main landing gear block and supporting structure.I also dug around the shop and found the hardwood stringers I’ll needto support the balsa sheeting on the top of the nose section. When Itest fit the cowl, she’s actually starting to look a bit like her oldself again! Maybe there is hope after all. 🙂
September 8, 2006.
I spent a few more minutes fiddling with the fuselage. I foundseveral cracks and splits in the cabin roof where the wing dowlsinsert, specifically the sheeting forward of that.
I also secured several more cracks and splits in the bulkheads andvarious places I found them. I epoxied the split off pieces back ontothe landing gear mounting block.
I glued the cracks and splits in the right side forward nose section(shown in test fit configuration in IMG_3993 in the Sep. 7 entry.) Ifinalized my scheme to splice in the left side nose piece to theoriginal. It will involve a number of doublers, some beefy squarestock, and a big mess of epoxy.
Finally, I began to reassemble the nose section.
September 7, 2006.
A week ago I scored a new replacement cowl from a very kind fellow modellerwho was willing to donate his spare to the cause.
Today I did some work gluing the split clamshell that was the fuselage backtogether. From the wing trailing edge foward split out like a big clam shell.From the wing leading edge forward is just splinters. After today I shouldmostly have the wing leading edge back to the tail all fixed up and solidagain.
Yes, it still looks pretty ugly, but an amazing amount of rebuild progresshas actually been made:
May 30, 2006.
Today I made a replica of the fuselage bulk head that is between thecabin and the firewall. I also started tracing out the piece for the leftside of the nose (which exploded in the crash.) It is important to get thesize and shape just right so the firewall has the proper amount of right anddown thrust. I think I’ve got it, but it’s something I have to be carefulabout. I’m not 100% sure yet how I will fit/splice the new piece into theold one, but once I figure out how to get the side pieces glued on in a structurally sound way, I’m home free for this rebuild I think.
The replacement firewall:
The replacement rear fuel compartment bulkhead:
The replacement "instrument panel":
The replacement left side of the nose area:
May 26, 2006.
I pieced together the shattered bits of the original firewall and usedthat as a pattern to trace out a new firewall. The firewall is two layersof 1/8" light ply, so I made two copies, and sandwiched them together withepoxy.
My goal is to use the original bits as patterns to build new pieces when theoriginal is just too shattered. There is still some thought that needs togo into how best to proceed in some areas, but I’m making progress.
May 19, 2006.
Happy birthday to me. 🙂 I spent the evening cleaning up the engine.The dirt was surface only, nothing even made it into the carb. The carb wasslightly shielded by the cowl and the engine wasn’t running when it hit.There was a small amount of dirt/grit inside the veturi, so I popped offthe carb and blew everything out from the backside with carb cleaner. Hopethat doesn’t attack the rubber gaskets (not to mention my fingers.) Thealuminum spinner appeared to have no damage, the engine seemed to turn well,the motor mount was 100% intact. The only thing that shattered was thefirewall. I’m going to have to build me another one of those.
May 17, 2006.
Some of the parts fit together, some don’t. Some pieces are just not thereanymore.
May 16, 2006.
Today I started laying out the parts to try to piece them together. I madea lot of progress figuring out what goes where, but haven’t glued anythingback together yet. Some pieces I can probably glue together and use, butsome of the more load bearing structures I’ll glue together to make a formand then reproduce the part.
For what it’s worth, the left side of the front fuselage got compressedand exploded into bits. The right side of the forward fuselage is"reasonably" intact. This would indicate that the aircraft had some rightlateral motion when it impacted the ground. That is the direction the tailswung around after impact and it was the right wing that ripped off.
After staring at the pieces for a few minutes today, I believe this Rascalcan be rebuilt and will fly again, but it will take some effort. It won’tbe a completely trivial rebuild.
September 26, 2005.
Until further notice, Rascal #1 is offline. We are transfering all ourinstrumentation and cameras over toRascal #2.Follow that link to the most current interesting info.
September 21, 2005.
Today we flew 3 very nice flights testing out a new patch antennafor our video system. The new antenna seemed to yield much better results thanwe were getting before. Plus we had determined that the ground transceiverfor our radio modem link had also been interfering, so we put some goodseperation between the radio modem transceiver and the wireless videoreceiver and that all worked much better.
The video was working well so the next thing we wanted to try was havingme fly by video only (using a buddy box system and a safety pilot.)Take offs and landings would be done visually as per standard R/C procedures. The fly by video would only happen during a short segmentof the flight.
Shortly after take off (with maybe 75′ altitude) the engine sputteredand died. I thought I had plenty of altitude to turn back to the fieldso I initiated a turn. By my recollection I stayed off the elevator toavoid any chance of stalling, so the nose dropped substantially duringthe turn. However, once I got pointed down wind and tried to roll out ofthe turn (still with 20-30′ of altitude) the plane was unresponsive anddove straight in at a pretty sharp angle. As you can see there wassubstantial structural damage.
img_2936Case of dumb thumbs? Did Iride full elevator all the way into the ground? I didn’t think so at thetime, but the consensus of the audience was that I stalled it in. Buthere is my thinking: 1. TheRascal is nearly impossible to stall, 2. I am aware of this issue and I*thought* I was intentionally staying off the elevator specifically toavoid this mistake, and 3. the plane seemed completely unresponsive inthe final one or two seconds.
But I also don’t trust my recollection and I know my mind can play trickswith me. I am hoping we have good MIDG data from this fateful flight.I am hoping that I can compare the planes directional vector with it’sorientation to get an estimate of velocity and alpha. I don’t think Istalled it in, but I’m hoping the data can shed some light on what reallyhappened. We don’t have a way to record control inputs or indicatedairspeed, so we may never know for sure what happened. Just so I don’tforget, wind estimate for the time of the crash was 5 mph out of the south.The MIDG will give me speed relative to the earth, not speed relative tothe local air mass.
Update (Sep 23, 2005):
- For some unexplained reason (and this has never happened to us before) our MIDG didn’t have a gps solution for the final flight. This means we had no position or velocity data, only attitude data.
- The attitude data clearly shows the take off, climb out, and turn back to the field.
- Our engine died during the climb out before the turn. But during the 180 turn back to the field, the nose immediately drops to between 10-15 degrees pitch down. This supports my intention to lay off the elevator during the entire turn so that gravity would keep the aircraft above a safe airspeed and eliminate the risk of stalling.
- Because of data buffering and the fact that when the main gear departed, it sheared off our radio modem antenna, I believe we lost the last second or two of data. Our wonderful video capture software automatically deleted the video for us because it detected too much snow (after the crash.)
Note that I am speaking unofficially here, and from the perspective ofthe pilot in command with an ego to defend. Whatever the evidence,the conclusion will be that it was not my fault. 😛
I believe I properly executed my plan to turn back to the field withzero elevator input. The resulting natural dive during the turnshould have kept the airplane at safe flying speed since it naturallyseeks an equilibrium. This aircraft is *very* difficult to stall andin all previous stall tests, stalls were slow, required a tremendousamount of forced up elevator, they were gentle not sharp, and somelimited control authority was always preserved even during the stall.This makes it hard for me to believe that I could have been in a stallregime, and even if I was, I would have expected different behaviorfrom the aircraft. I believe I had sufficient and safe airspeed.However, when I tried to roll out of the turn and pull out of the diveI had nothing. The plane gave no response and continued to divestraight into the ground.
My conclusion then is that given my recollection of the control inputsand my intentions (supported by the attitude data) combined with myunderstanding of aerodynamics and my specific knowledge of theparticular flight characteristics of this aircraft, I believe theaircraft maintained safe airspeed throughout the 180 turn backmanuever, and very likely I over compensated and gained more airspeedthan needed through the turn/dive. Based on my understanding of thespecific characteristics of this plane, I find it highly unlikely thatI was any where close to the stall regime. The more likely scenariois the relative orientation of the plane’s R/C receiver antenna to theground transmitter, combined with the interference patterns of the twoon-board transmitters (1 for video and 1 for data) put us in atemporary "dead" zone. Unfortunately our close proximity to theground when this occured meant that we were unable to fly through thedead zone and recover … we hit the ground first.
I think I can rule out pilot error in the direct operation of theaircraft, however there are still higher level issues we have controlover that likely contributed to the crash. Specifically engine tuningprior to the flight. We did run up the engine on the ground beforetake off and it sounded perfect, but perhaps we missed something.Also we were using a buddy box system for the first time on thisflight. Did that contribute in any way? Crashes seem to always be along sequence of events where the initial problem leads to, but is notthe source of the final crash. What else could we have done prior tothe flight, with the setup of the airplane, the setup of the buddy boxsystem, the setup of our instrumentation, our flight plan, etc. tohave prevented this crash? Are there things we can do to ensure morereliable engine operation?
This big Rascal can be rebuilt and will fly again.
2006-10-20 13:21:53 -0500 - Written by curt