Almost to Hog Heaven…..
06-26-2005, 10:51 PM
#1
Thread Starter
Almost to Hog Heaven…..
Here’s a few pics of my Hog that tried to make it to Hog Heaven, but won’t quite make it yet. It’s a Sig Hog I picked up from an estate sale complete with an OS .61 SF Long Stroke. Supposedly this plane had only 6 flights on it, the engine and radio. I pulled the radio out, installed and programmed my new Futaba 7CAP last night.
First two flights today went great – plane flew pretty good, but wanted to just float for about 400 ft on the runway.
Third flight I took off, flew a circuit and just turned back for a pass 150 ft beyond the runway at about 50 ft. I was at full throttle when the plane appeared to get elevator flutter when the left stab blew off causing the plane to dive. I pulled the nose up and then the engine shot off the plane, which went nose up, slowed to a stall. I pushed nose down and it responded by falling vertically to the ground. When it impacted, one mail gear and the nose gear ripped out, black marks from all 3 tires on the monokote, and the one remaining wheel bent backwards – the landing gear block pivoted inside the wing. And the fuselage split in half right behind the bulkhead at the wing hold down bolt blocks.
While I watched the plane fall, I also kept an eye on now loose engine. Estimates from witnesses put the engine traveling at least 250 ft in the air, and then down in the middle of the runway about 75 ft from the pilot box. I think it landed on the muffler since the engine turned through fine, and was not running when it hit ground, but the muffler cracked in half and there was a small round chunk out of the runway the size of the outlet. The plane impacted 2 to 3 seconds before the engine.
When I went to retrieve the stab 250 behind the rest of the plane I found one of the propeller blades sitting 2 ft. from it (Master Airscrew 12 X 6). The other blade and nose cone are still attached to the engine. The plane came to rest directly from the pilots box, 100 ft off the runway. The engine on the middle of the runway, and part of the muffler 10 ft from the pilots box. There is no damage on the nose from a blade hitting the front of the fuselage, and the spinner backplate was mounted 1/16” off the nose. The stock Hog mount sheered off even with the backplate of the engine, but I’m not sure if the carb came out upon impact or started to separate when the engine broke free – the clevis stripped off the threaded connector and is still attached to the throttle arm. The engine turns through smoothly, and the carb was undamaged and works smoothly, but the front muffler screw casting broke.
Truly awesome crash to watch unfold, but scary in having to watch a hot engine launch 250 ft uncontrolled like a model rocket.
Any ideas? I think the blade broke causing massive vibration which led to structural failure of the stab and engine mount before the engine could be shut down.
First two flights today went great – plane flew pretty good, but wanted to just float for about 400 ft on the runway.
Third flight I took off, flew a circuit and just turned back for a pass 150 ft beyond the runway at about 50 ft. I was at full throttle when the plane appeared to get elevator flutter when the left stab blew off causing the plane to dive. I pulled the nose up and then the engine shot off the plane, which went nose up, slowed to a stall. I pushed nose down and it responded by falling vertically to the ground. When it impacted, one mail gear and the nose gear ripped out, black marks from all 3 tires on the monokote, and the one remaining wheel bent backwards – the landing gear block pivoted inside the wing. And the fuselage split in half right behind the bulkhead at the wing hold down bolt blocks.
While I watched the plane fall, I also kept an eye on now loose engine. Estimates from witnesses put the engine traveling at least 250 ft in the air, and then down in the middle of the runway about 75 ft from the pilot box. I think it landed on the muffler since the engine turned through fine, and was not running when it hit ground, but the muffler cracked in half and there was a small round chunk out of the runway the size of the outlet. The plane impacted 2 to 3 seconds before the engine.
When I went to retrieve the stab 250 behind the rest of the plane I found one of the propeller blades sitting 2 ft. from it (Master Airscrew 12 X 6). The other blade and nose cone are still attached to the engine. The plane came to rest directly from the pilots box, 100 ft off the runway. The engine on the middle of the runway, and part of the muffler 10 ft from the pilots box. There is no damage on the nose from a blade hitting the front of the fuselage, and the spinner backplate was mounted 1/16” off the nose. The stock Hog mount sheered off even with the backplate of the engine, but I’m not sure if the carb came out upon impact or started to separate when the engine broke free – the clevis stripped off the threaded connector and is still attached to the throttle arm. The engine turns through smoothly, and the carb was undamaged and works smoothly, but the front muffler screw casting broke.
Truly awesome crash to watch unfold, but scary in having to watch a hot engine launch 250 ft uncontrolled like a model rocket.
Any ideas? I think the blade broke causing massive vibration which led to structural failure of the stab and engine mount before the engine could be shut down.
06-29-2005, 08:05 PM
#4
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RE: Almost to Hog Heaven…..
Hi HogFlyer
Nice description it sounds to me Like a catostrophic Failer of the air frame
you said you purchased it from a estate sale so the airframe could have had a fair bit of age even if it had only had 6 flights
some old glues deteriate with age, make sure you re-glue all the old joins before next flight
cheers
TailSlider
Nice description it sounds to me Like a catostrophic Failer of the air frame
you said you purchased it from a estate sale so the airframe could have had a fair bit of age even if it had only had 6 flights
some old glues deteriate with age, make sure you re-glue all the old joins before next flight
cheers
TailSlider
06-29-2005, 11:02 PM
#5
Thread Starter
RE: Almost to Hog Heaven…..
Hi guys!
I totally agree this doesn't make sense. I've snapped a couple more pics.
After looking the fuse over closely, it's history. The break came right behind Former F-5. Inspection of the fuselage interior, where one can't normally see because the radio was installed, definitely shows the fabrication is, IMHO, second rate. When I got this bird, I was after the OS .61 and the Radio and considered the airframe a free-bee.
Could there be a design flaw in the Sig kit? I've had 2 other hogs, but both where scratch built off the original 1958 plans. The original has a ply doubler that runs over the wing and past the equiv. of F-5 to hold the rubber band dowel. The Sig kit has the formers butting to the fuselage side, and the doublers placed between them. Thus the clean snap at F-5 is explained - a lot of plane behind for just the 1/8" sides to handle. Or is a an OS .61 SF too much power for this design?
Tailslider - this plane appears to have been built using CA, and is at least 6 years old. My 24 year old Scat Cat 500 with 2500+ flights, built with carpenter glue is solid as a rock. Does CA get that brittle after only 6 years? I tend to build with carpenters glue and epoxy, hardly use CA.
Catastrophic airframe failure sounds like the most likely culprit. I was making a full throttle pass out of turning dive, and was on the first circuit after takeoff, so the weight was at max (12 oz fuel) at a point of high stress on the airframe. That also explains why I had control of the plane after the tail snapped.
I still am baffled by the prop breaking in flight. Both a broken prop (see pix) and vibration form flutter would explain the engine mount breaking also. The prop was a 12 X 8 - is this too much for this plane? It's the one that came with the plane (my other Hogs, built from the original 1958 plans, where .40 powered).
Thanks for the reply’s and the help. I'm still totally baffled as to what went first, the airframe or prop.
I totally agree this doesn't make sense. I've snapped a couple more pics.
After looking the fuse over closely, it's history. The break came right behind Former F-5. Inspection of the fuselage interior, where one can't normally see because the radio was installed, definitely shows the fabrication is, IMHO, second rate. When I got this bird, I was after the OS .61 and the Radio and considered the airframe a free-bee.
Could there be a design flaw in the Sig kit? I've had 2 other hogs, but both where scratch built off the original 1958 plans. The original has a ply doubler that runs over the wing and past the equiv. of F-5 to hold the rubber band dowel. The Sig kit has the formers butting to the fuselage side, and the doublers placed between them. Thus the clean snap at F-5 is explained - a lot of plane behind for just the 1/8" sides to handle. Or is a an OS .61 SF too much power for this design?
Tailslider - this plane appears to have been built using CA, and is at least 6 years old. My 24 year old Scat Cat 500 with 2500+ flights, built with carpenter glue is solid as a rock. Does CA get that brittle after only 6 years? I tend to build with carpenters glue and epoxy, hardly use CA.
Catastrophic airframe failure sounds like the most likely culprit. I was making a full throttle pass out of turning dive, and was on the first circuit after takeoff, so the weight was at max (12 oz fuel) at a point of high stress on the airframe. That also explains why I had control of the plane after the tail snapped.
I still am baffled by the prop breaking in flight. Both a broken prop (see pix) and vibration form flutter would explain the engine mount breaking also. The prop was a 12 X 8 - is this too much for this plane? It's the one that came with the plane (my other Hogs, built from the original 1958 plans, where .40 powered).
Thanks for the reply’s and the help. I'm still totally baffled as to what went first, the airframe or prop.
06-29-2005, 11:46 PM
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RE: Almost to Hog Heaven…..
Well this might sound weird, but close you're eyes and replay the event. What did you hear? If that prop went, I would imagine that there would be an associated sound, then the ensuing structural failure. If there was no sound, it might have been flutter. Just my 2 cents.
As far as CA getting old. IMHO, ca simply cant do the job for many applications that the other types of glue can. CA is a surface to surface bond rather than a filler type bond. Thus, CA will build very light, but since it is only the surface being bonded, the likelyhood of a break occuring is greater especially over time.
It does sound like a rather spectacular crash though,
I just looked at the prop picture, it looks VERY hammered. If the prop came apart in flight, it didn't get all that damage from the crash (speaking about the separated part). Is that the same prop that came on the plane? If not, did you mow the lawn with it?
Tom
As far as CA getting old. IMHO, ca simply cant do the job for many applications that the other types of glue can. CA is a surface to surface bond rather than a filler type bond. Thus, CA will build very light, but since it is only the surface being bonded, the likelyhood of a break occuring is greater especially over time.
It does sound like a rather spectacular crash though,
I just looked at the prop picture, it looks VERY hammered. If the prop came apart in flight, it didn't get all that damage from the crash (speaking about the separated part). Is that the same prop that came on the plane? If not, did you mow the lawn with it?
Tom
06-30-2005, 01:56 PM
#7
Thread Starter
RE: Almost to Hog Heaven…..
Liberator -
I've been replaying the incident over and over. It all happened with in about 2 to 3 seconds and I vividly remember the movements of the plane and talking to a buddy standing next to meabout what was happening. I think when it started, I was on a high speed diving turn from 100 ft to about 50 ft when the and just turned paralled to the runway. I heard a what I initially thougt was flutter and the pop as the stap came off, saw the stab blow off, the plane pitched down. I know it came close to the ground, and maybe it did just catch the ground and bounced up. That would explain the chunk of prop setting there. It also rolled to the right with up elevator and required heavy aileron correction. The more I think about it, I think I did reduce the throttle at the sound because the of the way the plane slowed. I also remember the sound of the engine quitting as it launched off the plane - just dead silence and the crunch as the plane hit the ground - all in slow motion. This would also explain why the gear ripped out and the tire marks on the wings.
That's the prop that came with the plane. It didn't appear to have any bad spots or damage on it when I inspected it.
As far as CA goes, the plane appears to have built with it. I'm not a big fan of CA - I totally agree it's a surface glue and doesn't soak into the wood like carpenters glue does, nor does it have the flexibility of carpenters glue. I've flexed several of the bulkheads in the fuselage and they all popped loose. There is a lot of light ply used and it's all been CA's in place. From the looks of it, the light ply wasn't sanded or prepared, and there are several other parts that don't have good joints.
The more I think about it, the more I feel it was airframe failure in flight caused by elevator flutter and probably an impact with the ground. The fuse very well could have been severly damaged and the engine separated, but it all didn't come apart until the final decent and impact with the ground.
Thanks for the insight and help. I think the pieces are slowly falling in place.
BTW, since I don't intent to fix this fuselage, I've decided to mount it on a trophy plaque with a small portion of a wing. Some may place a deer or other animal this way, I'll just start a collection of crashed models.
I've been replaying the incident over and over. It all happened with in about 2 to 3 seconds and I vividly remember the movements of the plane and talking to a buddy standing next to meabout what was happening. I think when it started, I was on a high speed diving turn from 100 ft to about 50 ft when the and just turned paralled to the runway. I heard a what I initially thougt was flutter and the pop as the stap came off, saw the stab blow off, the plane pitched down. I know it came close to the ground, and maybe it did just catch the ground and bounced up. That would explain the chunk of prop setting there. It also rolled to the right with up elevator and required heavy aileron correction. The more I think about it, I think I did reduce the throttle at the sound because the of the way the plane slowed. I also remember the sound of the engine quitting as it launched off the plane - just dead silence and the crunch as the plane hit the ground - all in slow motion. This would also explain why the gear ripped out and the tire marks on the wings.
That's the prop that came with the plane. It didn't appear to have any bad spots or damage on it when I inspected it.
As far as CA goes, the plane appears to have built with it. I'm not a big fan of CA - I totally agree it's a surface glue and doesn't soak into the wood like carpenters glue does, nor does it have the flexibility of carpenters glue. I've flexed several of the bulkheads in the fuselage and they all popped loose. There is a lot of light ply used and it's all been CA's in place. From the looks of it, the light ply wasn't sanded or prepared, and there are several other parts that don't have good joints.
The more I think about it, the more I feel it was airframe failure in flight caused by elevator flutter and probably an impact with the ground. The fuse very well could have been severly damaged and the engine separated, but it all didn't come apart until the final decent and impact with the ground.
Thanks for the insight and help. I think the pieces are slowly falling in place.
BTW, since I don't intent to fix this fuselage, I've decided to mount it on a trophy plaque with a small portion of a wing. Some may place a deer or other animal this way, I'll just start a collection of crashed models.
