And then it started. First a modest but very noticeable vibration. Something had failed in the engine....throttle was slowly pulled back to idle and a descent initiated.....”Columbus (Georgia) Approach, Cozy 10 charlie zulu, I’ve got an engine problem and am headed for that airport off to the west”....no answer....the vibration suddenly became very extreme, the airplane was shaking violently....it induced a flutter in the canard which was flexing the tips at least 6 inches .... wow! the canard was a blur ... am I in trouble! .... Mixture to off .... raise the nose a bit to reduce airspeed ..... speed came back to about 90 knots .... the vibration stopped just as suddenly after about 10-15 seconds ....”Columbus Approach, Cozy 10 charlie zulu, I think my prop failed, I’ve shut down the engine” “Roger, are you declaring an emergency?” “Affirmative. I’m headed to the airport at 12 o’clock.” “That’s Auburn. How many souls and fuel on board?” “ One person, standby on the fuel .... (push a  button on the vision micro) ... 31 gallons.” “Roger” “Could you get the unicom frequency for Auburn” “Standby ..... 123.0” “Thanks. I’m switching over” “Auburn do you read Cozy 10 charlie zulu?” “Roger.” “I’m overhead with the engine shut down and headed for 36" “Roger”.... rolled out on a high down wind and did not want to extend away from the airport but the base was obviously too high .... ”What’s your elevation?” “776 feet”..... airpspeed check, 120 knots, damn, bring the nose up .... get it back to 90 .... 2600 feet indicated ... decide to do a 360 over the numbers ... sink is something less than 1000 .... Cozy is flying great but very quiet .... roll out on down wind a second time and things look much better .... base leg .... looking good .... final about 400 feet agl ... extend the board .... 90 knots .... on the concrete .... wow! 

I rolled to the intersection of 22 turned on it and stopped. The greeting party included one ambulance, one police car, and about 5 pickups with local guys. Everyone was looking at the prop. What a shock! One blade was missing and the other 2 were badly damaged. Also missing - the top exhaust stack on the right side. A group of guys helped push the airplane to some grass where it is now parked. Auburn is a beautiful airport. Looks like a golf course. ATC wanted a call. The supervisor was filling out a form with basic stuff and I asked it he needed a written report and he said no, but you better check that engine mount....that was an under statement. Called my wife...honey, won’t be home tonight and I’ll call you back as soon as I figure out what to do next....pulled the cowlings....as I suspected, the top pipe is #4. It has the heat muff welded to it and the pipe failed where the aft end of the muff is welded. I had a aluminum shroud around both pipes as per plan so the pipe slid aft and out into the prop.
 

The engine was inspected quite thoroughly before this trip as I had both cowlings off changing oil and filter. But what I did not do was remove the aluminum shroud around the #2 and #4 pipes. The pipe probably was cracked and I did not see it because of the shroud. (major dumb-dumb, not removing the shroud).

I rented a car for 2 weeks and drove home. As soon as I can round up some new pipes (they are on the way) and get FAA approval to use a new Felix prop which just arrived a few days ago, I’ll head back to Alabama to retrieve the airplane. Meanwhile, is there a builder in the Auburn area? The top cowling has a minor ding where the prop kicked the pipe up and away and it could use a 2 ply lay up for temporary repair. Also, does anyone have experience with this much vibration....a brief inspection revealed no mount damage, but I’m wondering about the engine itself. It was at idle when the major shaking started and the mixture was pulled immediately. 

Anyway, I’m pleased and thankful to be among the living. Check your pipes guys .... the more often, the better. 

The Adventure Continues - Lessons Learned

I returned to Auburn, Alabama, on Monday of this week hoping to retrieve my Cozy which had been sitting there since April 12 after the #4 exhaust pipe went through the prop. 

The first thing on the list was to check the engine flange for run out. I borrowed a micro dial gauge from a friend and checked it twice - max run out I could detect was .001. The new limit for this engine is .002 and the service limit is .005. The flange is not bent. The next thing checked was the engine mount and firewall hard points- no cracks anywhere. Then a die penetration check of the prop extension - no cracks on it. 

On the engine itself I found 2 of the 4 primer lines broken at the #2 and #4 cylinder intake ports. I capped the lines, removed the nozzles and installed plugs. Also found about 5 rivets in the baffle system broken and replaced them. Everything else in the engine compartment appeared secure. Up front the canard was checked. It looks normal. Attach fittings are without visible cracks. That 10 or 15 seconds of flutter really got my attention. A metal surface probably would have disintegrated. 

There was about a gallon of water in the nose down section. Removed it. Next I installed the new exhaust stacks at #2 and #4. I also closed the exit through the baffle system from 2 inches to 1.75. Also installed a steel hose clamp just forward of the baffle on each pipe. The pipes now are very tight and will not leave the airplane ever again.

continued...

All this work took about 10 hours on Monday evening and Tuesday. Finally at about 4 pm Tuesday it was time to flight test the beast. The wind was rather gusty but I wanted to get this over with so I cranked it up and did it. The engine came to life  immediately and all system were working. I flew for 30 minutes, became weary of the turbulence and called it quits. Before returning to my motel and a couple beers, I pulled the cowling and checked things one more time. All looked well. 

This morning at 8:30 I took off bound for St. Louis. It wasn’t the most relaxing flight I’ve ever made but the trusty Lycoming purred like a kitten for 3:20 minutes and got me home. The take off out off Auburn was a little tense as there was a line of trees off the runway and just beyond that a shopping center which I turned away from. But once at10,500, the flight was within gliding distance of a hard surface runway most of the trip and I kept track of where these airports were constantly. (probably would be a good idea to do that all the time....)
 

Because I will not be able to fly this airplane again without wondering about the accessory section, I’ve already started to jerk the engine so as to comply with AD91-14-22. The purpose of this AD is “To prevent loosening or failure of the crankshaft gear retaining bolt, which may cause sudden engine failure”. While this AD is not mandatory on experimental airplanes, it would seem prudent to comply with it. 

Lycoming also has a “mandatory service bulletin” advising an engine tear down, which the FAA has not yet deemed appropriate as an AD. Like 5 or 6 guys who responded saying the engine probably is OK, I agree. But I will feel better after going through the hassle of checking that little bolt. I will hire a qualified mechanic for the inspection, installation and security of the bolt, the dowel, and its gear. 

This event was preventable. If the baffle exit holes had been at 1.75 instead of 2 inches, the broken pipe probably would have jammed there. Also, if my inspection procedure had included removing the aluminum heat shield at each oil change, certainly the cracks would have been apparent before the pipe broke. That pipe went from no cracks to compete failure in a little over 100 hours.

With regard to a theory that the pipe exit hole through the baffle has some affect on cooling, I submit this for contemplation. Some time just before the pipe broke and interrupted my serene flight, I wrote down some CHT numbers at 10,500. (I was somewhat
bored) The average CHT with the 2 inch holes and the 1.75 inch pipe was 352°. Today, with the same power setting at the same altitude, the average CHT was 315°. (1.75 hole with a 1.75 pipe in it.) The only difference today was a OAT at 8°C cooler. That would account for some of the difference, but not all of it. The hole in the baffle larger than the pipe probably does not make for cooler running. 

Hope to be flying again in several weeks....

Dave's Cosy in earlier days.
 

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