Reviving a 1984 Sonerai IIL

[cpd]

Back in December I began looking for a Sonerai II, after spending the last decade flying a Pietenpol and various ultralights I had began to feel the need for speed again! I was also considering KR2s but having put 12-15hrs on a Sonerai IILT back in 2013 I decided that was the better option given the steel and aluminum construction vs wood/composite and its flight characteristics are somewhat known to me. My neighbor across the grass strip from me got wind of my search and pulled back a dusty tarp in the corner of his hanger to reveal 9BX, a 1984 Sonerai IIL. She was built by Bob Scannell of missouri and is powered by a revmaster 2100D swinging a 54x48 sterba prop. Between 1985 and 1994 she accumulated 341hrs of flight time including 5 oshkosh trips winning best sonerai at airventure 91. Bob sole her in 1994 and she was moved to florida where she sat in a hangar, wings removed gathering dust til my neighbor bought her and relocated her to kansas in 2018. Back in kansas my neighbor fiddled with her occasionally, replacing the exhaust stacks and rebuilding the rare float type revflow carburetor, he attempted an engine start in 2019 but with no spark on the dual mag she got stuffed in the back of the hangar again and there she sat til I purchased her 4 weeks ago.

after getting her home my 1st project was to pull the motor and remove the bendix dual mag. I disassembled and serviced the mag per a 500hr inspection and comply with the various service bulletins ignored since 1984. let me say, im usually a fan of bendix mags but i didnt enjoy working on the 3000 series D4RN and hope its a good long while before I need to open her up again! I flushed out the tank, replaced the fuel lines, pre oiled the oil system, topped her off with some good ol hundy LL and on sunday evening brought the revmaster 2100 to life for the 1st time in 30 years. I gave her 4 shots of prime, pulled the prop through 4 blades by hand then cranked the starter, she fired on the second blade and settled into a happy idle at what sounded like just over 1,000 rpm (tach is currently inop).

Video of the startup can be watched here:

Oil pressure was normal and oil temp began to rise after 10 minutes or so, CHT was indicating about 250 but the EGT and tach were inop. switched the alternator on and the ammeter indicated charging. I briefly accellerated the engine to what sounded like 2700 rpm and she responded to the throttle normally without any hesitation, mag check showed normal rpm drop on both sides of the dual mag. I did note that pulling the mixture know out more than3/4 inch or so resulted in a rough engine. SUCCESS!

yesterday evening I removed the wings from the rack where they had hung for 30 years and reinstalled them. I plan to do alot of ground running and taxiing on my home airport (18ks, a 2500ft grass strip) but the little angle on my shoulder tells me its best to trailer her 30 minutes away to the 5,000ft paved strip for her first flights. I'm sure she will get off of the 2500ft strip but having not flown a sonerai in 12 years and not having much time in my 1st one to begin with I dont need the added challenge of getting down on the 2500ft runway on the 1st landing, especially if the airplane has any bugs pop up.

So far the list of things to address includes: replacing oil lines, addressing play in the ailerons coming from the linkages behind the seat, and fixing a skin corrosion issue in the area of the RH aileron balance tab/counterweight. Im sure others will pop up as well when I get into a thorough condition inspection on her. so far though I would say build quality on her is above average, even the interior surfaces of the wing skins and spar webs were zinc chromated before assembly and the wings were entirely assembled with solid driven rivets, not cherry type pull rivets. first flight is still 2 or 3 months distant im sure and I will keep this thread updated as I go. im sure I will have plenty of questions for you guys along the way as well.

Chris

 

[BJC]

Nice looking airplane. Congratulations.


BJC

 

[Elviar]

Looks and sounds great. I like those wing tips!

 

[TarDevil]

Sweet! I'm envious.

 

[cpd]

For the first time since 1994 my Sonerai IIL has moved under its own power! I made a few taxi runs this evening up to about 25mph. Ground handling seems to be absolutely delightful so far, just little toe taps needed to keep her going in the right direction. Long ways to go still before she is airworthy again but it sure felt sweet to have her out on the runway

 

[cpd]

Over the weekend I did the engine portion of the condition inspection, changed oil, torqued head bolts, set valves, etc.... yesterday I performed the first full throttle run ups on the revmaster 2100D in 30 years. She spun the sterba 54x48 up to 3100rpm static, I made 3 runs to full power, each lasting 2 minutes and ran it about 15 minutes at 2500rpm. Temps and pressures all green and smooth as butter above 2800rpm. She seemed a bit rougher than I expected between 2000 and 2800 rpm, not vibration I could feel just the exhaust note sounded "poppy" and not smooth. Might be mixture related, need to get the EGT working so I can see what the mixture is doing in that power band.

After shutdown there was a lot of oil dripping from the right side of the motor, lower cylinder fins and pushrod tubes were covered in it. At this point I'm thinking it's a leaking fitting on one of the braided steel oil cooler lines, I will clean it up and chase the cause on the next run. Lots of baked on varnish on the bottom of the RH cylinders suggests this was a problem 30 years ago!

Have one cylinder with terrific compression. 2 with average compression, one with a slight intake valve leak and the other with a slight exhaust valve leak. And one with low compression with an exhaust valve leak. This is a newer development, after the 1st start and few minutes at idle 2 weeks ago all had great compression then after taxiing last week 1 had good compression and the other 3 were quite low. Engine has 341 total time with about 160 on the heads and valves, I scoped it before the 1st start and the jugs were rust free. I will continue monitoring compressions over the next hour or so of ground running and taxiing and will pull heads and lap valves if needed.

After the runup I noticed the impulse coupling wasn't snapping either, a few taps in the mag with a screwdriver handle resolved that but one more thing to monitor, it was inspected and serviced per the 500hr inspect on the mag and in good order so will continue to monitor that as well.

Chris

 

[TFF]

While I get you don’t want to crack into it, I would go ahead and fix the valves. If you follow the engine hour pattern of a 350 hour engine and valves starting to leak at 160, it’s telling you something. It’s not end of the world or anything, but first flight in decades, with a question of why and quit it flying in the first place, let it prove to you the next 150 hours condition with fresh valves. It will also give you a condition check of the rings if you know the valves aren’t leaking.

A friend bought a plane, we did a prebuy great compressions. Owner had passed but it was flown. In reality it was a 15 minute plane for the original owner. When my friend started flying it and to him a short flight is two hours, the compressions tanked. I let him fly it like that for a few more years, but I told him it was time we are not squeezing any more out of it without spending money. I’m all for using it up, but it has to prove it to me.

 

[delta]

I'd re-check your valves clearance just for drill.

 

[cpd]

While I get you don’t want to crack into it, I would go ahead and fix the valves. If you follow the engine hour pattern of a 350 hour engine and valves starting to leak at 160, it’s telling you something. It’s not end of the world or anything, but first flight in decades, with a question of why and quit it flying in the first place, let it prove to you the next 150 hours condition with fresh valves. It will also give you a condition check of the rings if you know the valves aren’t leaking.

TFF, I can confirm no ring leakage. The reason she quit flying in 94 was that the owner completed a Zenith 301 and passed the sonerai on to a new owner who was never able to fit in the cockpit being that he weighed near 300lbs and he never did go on a diet, just held onto the plane. I am getting the leaking valves are probably the ones that spent 30 years held off their seats. yes 30 years is a long time to be sitting in storage, that why i'm going to ground run for an hour or 3 and monitor the situation as well as look for other issues, seal leaks, etc..... dont want to pull the heads now just to have to do it again after an hour or 2 to fix something else. No worries though she wont be flown with leaking valves, or any other issues.

Chris

 

[TFF]

Most planes have leaky valves if they got time on them. It’s not like they don’t usually seal under running conditions, but it’s not easy sealing. A leaking valve on a Lycoming is a different level from a VW, that tend to have valve problems pop up. I get it, but VWs care when certified don’t. I like doing cold compression checks. They really show how slack things are.

 

[TFF]

A 300 pounder would be interesting in a Sonerai with normal seating.