Repaired Exhaust System Reinstalled
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- Written by Kevin Horton
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Saturday I reassembled the repaired exhaust system and put it back on the aircraft. I’m very glad I took a lot of pictures as I was removing it, as it is in six pieces and it wasn’t obvious how the puzzle went back together. I also had quite a number of heat shields to reinstall.
I did’t get a test flight off that day, as it was very hot and muggy and I ran out of energy before getting to the engine run stage. I’m chasing a small oil leak near the front of the engine, so I cleaned the engine up and will do a couple of short engine runs before I put the cowling back on, hoping I can see some sign of where the oil is coming from.
Here is the repaired top end of the #3 cylinder exhaust pipe. You can see the new 0.049” wall thickness pipe at the top and the new flange.
Here you can see the welded on reinforcing patches that Larry Vetterman put at the top of each of the other cylinders. These are part of the currently shipping configuration.
I hope to get the aircraft flying tomorrow.
Tire Change
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It’s been a busy few weeks. I was in Wichita, KS for three weeks flight testing a major update to the avionics for the Bomdardier Global 6000 large business jet. It is almost impossible to keep up with the myriad marketing product names. I first heard the “Global 6000” designation during this trip. Up to now they called it the “Global Vision” variant of the Global Express, and the latest avionics fit was called the Global Vision Flight Deck. The avionics are from Rockwell Collins, and they call them the Pro Line Fusion avionics. The renaming of the Global Express as the Global 6000 wasn’t completely unexpected, given that the short fuselage variant is the Global 5000, and the future models are the Global 7000 and 8000.
I got back about 10 days ago. The first weekend back I changed the main landing gear tires and tubes on the RV-8, repacked the wheel bearings with grease and inspected the brake pads. The brake pads were in good shape, but one of the calipers was jamming up against the bottom aft corner of the landing gear leg. I knew there wasn’t much clearance there, but thought there was enough. But, the caliper wasn’t moving freely, so I used a file to put a small bevel on the corner to ensure the caliper would slide correctly.
The left main gear tire was wearing strangely on the inboard edge. It looks as if something was rubbing on the edge of the tire, but I can’t figure out what that might have been. There is no sign of any rub marks on the edges of the wheel pants and the flexible brake line isn’t long enough to reach that far. I never heard anything rubbing was I pushed the aircraft into or out of the hangar. I’ll keep a closer eye on the wear pattern of the new tires.
Repaired Exhaust System Arrived
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The repaired exhaust system arrived today, back from Vetterman Exhaust. The repair looks excellent. Larry Vetterman put a new piece of 0.049” stainless steel tubing on the top end of the broken #3 cylinder pipe (the original wall thickness was 0.035”). The other pipes received reinforcing plates welded on the outside of the pipe at the flange weld. The reinforcing plates are standard now on these exhaust systems. The tubing on current systems is still 0.035” as it is much lighter than 0.049” tubing”, but Larry uses 0.049” for any needed repairs.
Pictures to follow.
I hope to get the repaired exhaust system reinstalled this weekend.
The Hawk is Back in its Roost
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The aircraft is finally back home in its hangar in Smiths Falls. Eight days to fly from Oshkosh to Smiths Falls.
Plan A was for a coworker to fly me and the loaner exhaust system to North Bay this morning. But, the long range weather forecast had some showers and thunder showers in it, and the weather guys kept changing their story on when a weather system approaching from the NW was forecast to arrive. I really needed to get this done on Saturday, so to avoid the possibility of a weather abort Terry and I drove to North Bay Friday evening - Plan B. I changed out the exhaust system on Saturday morning, while Terry drove to Smiths Falls to pick me up.
I took a closer look at the failure after I removed the exhaust system. The pipe broke immediately below the weld that attached the flange on the top end of the pipe. The weld looked completely normal to my untrained eye. The break looked fresh on the outboard edge of the pipe (closest to the viewer in this photo), but there was a lot more exhaust residue on the break on the inboard edge of the pipe. Perhaps a crack started on the inboard edge, where I couldn’t easily see it during inspections, and it finally progressed far enough so that it went the rest of the way around in a very short period of time.
Here is the flange. The outboard edge is on the bottom in the photo.
Tomorrow I’ll box up the exhaust system and we’ll ship it back to Larry Vetterman on Monday.
Thanks to everyone who helped: Hal and Armand for the hangar space in North Bay, Alfio for the ride to North Bay and back so I could put the aircraft in the hangar, Mark for the use of his exhaust system, and Terry for driving to North Bay and back.
Exhaust Failure Update
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I’m making progress on recovering the aircraft. Monday I made contact with Larry Vetterman to discuss my failure and get his advice. He said that the IO-360-A series engines are the model where he has by far the most problems with exhaust system failures. The failure rate must be fairly low though, as I’ve never seen any discussion of it as a concern on any public forum. But, since my exhaust system was made in 2001, Larry has done a continual series of design changes to address various areas that proved problematic in service. In particular he has increased the wall thickness of the stainless steel tubing at the top of the exhaust from 0.035” to 0.049” as well as making reinforcements in various areas. I’ll ship my whole exhaust system back to him and he will upgrade it to the latest configuration, which has proved relatively robust in service.
I got a very generous offer of temporary hangar space from a Cessna owner in North Bay who is good friends with an RV-9A builder who read about my plight on the Vans Air Force web forums. Yesterday evening local RV-9A Alfio F. flew me to North Bay and back so I could put the aircraft in the hangar. Thanks Alfio!
This evening I drove to Carp to meet with Mark R. who has an RV-8 with a similar engine to ours. His aircraft was damaged when his hangar door blew in earlier this year, so it is out of service. Mark removed his exhaust system so I can borrow it for a few days. Thanks Mark.
This coming Saturday morning John, a coworker, has agreed to fly me, the loaner exhaust system and a bunch of tools to North Bay. I’ll remove my exhaust system and install Mark’s, load up the tools, etc and fly back to Smiths Falls, hopefully.
Back Home, but Aircraft in North Bay
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We had a pretty good Oshkosh, all in all. We saw many old friends, purchased the various things I was looking for, and narrowed down our choices in oxygen systems. Terry spent the whole time with me, unlike last year when she bailed out to visit sisters after she had her fill of mud. This year she enjoyed it all, except for a couple of hours Wednesday morning when it seemed like the rain would never end and her fun meter was bouncing in the red zone for a while. We never did visit the beer coffin guy, as he apparently was ill and never made it.
Terry and I got home from Oshkosh late yesterday evening, after a much longer and more complicated day than expected. We left Oshkosh shortly after 9 Friday morning, and did a very short flight to Green Bay to get fuel, fill out an electronic EAPIS form to keep US Customs happy, and file IFR flight plans. Next stop was Sault Ste Marie, MI for lunch and to phone Canada Customs. Things were going well until just after we passed overhead North Bay, Ontario, when the engine developed a new vibration. It wasn’t a strong vibration, but it was strong enough so you were sure it wasn’t your imagination, unlike those mysterious vibrations and noises that single-engine aircraft engines often seem to develop as soon as you are over a large body of water. I started going through the various pages of the engine monitor, looking for anything abnormal. As I was doing that, I got a warning from the engine monitor that the “EGT Spread” was high. The EGT Spread is the difference between the highest and lowest Exhaust Gas Temperature (EGT). I saw that the #3 EGT was falling, and it bottomed out about 350 deg F lower than the other EGTs.
The engine was still producing good power, but something was clearly wrong, so I told Toronto Centre that we had an engine anomaly and wanted to divert to North Bay. They were very accommodating, and gave us clearance for an immediate left turn to north, followed quickly by clearance direct to North Bay and descent. I was already well within gliding range of North Bay, and I saw the airport, so I wasn’t too worried. The engine kept running, but it was backfiring once in a while. I did a 360 degree overhead arrival into North Bay, keeping well within gliding distance the whole way, and landed about 2500 ft down the 10,000 ft long runway. Terry kept her cool the whole time.
There was no big pool of oil after shutdown, which was a good sign. I was hoping the cause was a plugged fuel injection nozzle, as that left some hope of flying home that day, but I also wondered about a possible exhaust pipe failure, which was the only other thing I could think of that fit the observed symptoms. I pulled the tool kit out of the front baggage compartment, and removed the cowling. The problem was immediately obvious - the #3 exhaust pipe had broken at the weld where the exhaust pipe attaches to the flange that bolts to the cylinder, so the pipe was completely free of the cylinder.
I couldn’t arrange hangar space easily, and it was looking bad for a rental car, but we eventually got one. We pulled our gear from the aircraft, tied it down, and hit the road. I might be able to borrow an exhaust system part early next week from one of the many Ottawa area RV-8 builders, or I may be able to get a replacement part here by overnight courier by Tuesday or Wednesday. In any case, I’m hopeful to get the aircraft back home by the end of next weekend.