Stewart 51 Partner LLC

2017 News and Events

January February News and Events
Even down here in Alabama and the panhandle of Florida, there is winter, and winter slowed things down again this year.  We did get our set of pre-production ribs from Mooney International, shown below in the racks in Pensacola.  We'll be trial fitting these new ribs to the spar from the wing we are disassembling to check them for proper dimensions, fit, and compatibility with stringers and other components.
I did finally fly Doll again on February 1st, a one hour local flight in Bartow.  Everything checked out properly.  I had taken Doll down in June of 2016, so there was about an eight month interlude between flights.  Harry and crew had removed the Electromotive Ignition system for repair, got it back, and had it ready to go.  After the successful local flight, we loaded up and flew to Pensacola on the 2nd..
I changed the oil and filter Saturday the 18th, did the leak checks, then cowled her up.  Sunday was such a pretty day all over the southeast, I just had to fly somewhere.  I "go with" a lady in North Alabama, so we arranged to let me fly up to see her for lunch:  The S51 version of the $100 Weekend Hamburger, although we enjoyed more sophisticated fare.  About an hour and a half up, another hour and a half back, making for an excellent Sunday.  It was nice.
The photo below was taken by Beth as I was shutting down up there.
Beth came down to Montgomery this past weekend for a Mardi Gras visit.  We enjoyed downtown Montgomery, and spent the afternoon at The Aviator Bar, owned by an old fraternity brother and aviation enthusiast, Mike Watson.  Watson has done an incredible job with the bar, and hosts regular citizens and the military contingents from Maxwell AFB, the Alabama Air Guard (F-16's), and other drinkers who enjoy an aviation theme with their libations. 
Beth and me in front of Mike's beer pulls.
The last pieces of news include Cliff Fitch, Jim Gohm, and Rod Bower:
Rod is closer and closer to his first flight, still ironing out a couple of items before breaking ground.  Jim Gohm is up and flying again out in Arizona after installing an oil cooler in the scoop to get his oil temp more comfortable.
Cliff Fitch and his son, Cliff III, journeyed down from Illinois last week to get his overhauled prop and do the final planning for the main and tail landing gear components we lack.  Cliff and his son will be building main gear trunions, pistons, and all the other goodies that we lack for the landing gear.  Cliff also figures to be flying his Stewart again as winter eases up in his neighborhood.

The last photo for this segment is of some of the machined parts we just received from our supplier in Pensacola.  These fellows did a nice job on the engine mount brackets and several other components we needed.

March April News and Events
On a local flight in Pensacola in early March, I had some difficulty switching tanks:  The fuel selector was stiff and didn't want to move freely, not necessarily a good thing.  So, I went about removing what I needed to remove to get at it, pulled it out (it's down inside that circular hole under the seat frame), disassembled and cleaned and replaced "O" rings, lubed it, put it back together, reinstalled it, leak checked it, ran her up to check function, put the interior back together, and had that issue handled.  That's all you have to do sometimes.

Cecelie, Ole, and Jim.

S51 kit builder Ole (and his lovely wife Cecelie) Ringstad came over from Norway for some vacation time, some pilot recertification review work, and to meet Jim Stewart.  Their U.S. trip began in Orlando, where Ole visited with the Stalion 51 people at Kissimmee.  I met up with them in Bartow Friday March 31st, where Ole studied the kit we are building at Harry Stenger's Aero Fabrication and Restoration. 
Saturday morning, we flew up to Zephyr Hills Airport where Ole had a two hour visit with Jim.  Ole and Jim shared ideas on Ole's progress with his BMW auto engine conversion and other engine related items.  A great visit, one that impressed Ole as to Jim's engineering knowledge and genuine curiosity about Ole's V-12 pursuit.  Recall that Jim had done some initial work with the Italian BPM V-12 engine, but no reliable supply source could be arranged.  GM based V-8's are a little easier to come by.  It was nice to see Jim and listen to Ole's visit with him.
Below, you see Jack Peck in the cockpit of his S51 at his home in Spruce Creek, which was our destination after leaving Jim in Zephyr Hills.  Ole and I had a great study of Jack's plane and compared notes.  Jack had house guests, which added to a nice visit with Jack and Mary.
Coolant System Issues
For several years now, we have been evolving several systems on Doll, including the powerplant cooling system.  We added a dual thermostat box, changed pressure cap ratings, and have flown on.
As I began to fly Doll again this spring, I began to notice I was having to add more coolant than normal after a period of flying.  In prior years, we would purposely overfill the system, then let it "pop off" and vent excess overboard.  We would then fly at that level for a while, having learned where the system liked to be on total coolant volume.  That worked fine until lately, when the coolant seemed to be needing more added to get back to the "pop off" point.
On a particular flight in March, I taxied in and had an abnormal "pop off" event occur as I was parking and about to shut down, the engine  getting hotter than the normal warming we always get while taxxing in.  I had not opened the scoop outlet door on final approach on this flight, and assumed that leaving it closed on final added to more latent heat not being dissipated.  Keep in mind the vast difference in 100 knot airflow through the radiator and 4 knot air taxiing in.  Add to that effect the fact that the water pump is turning much more slowly on taxi-in than in cruise flight or on final approach, and one can see why some warming occurs.
I flew several more local flights, but always having to add coolant, so it did finally dawn on me, "You might ought to figure out where the coolant is going."  The other big clue was that our coolant system pressure was bleeding down sooner and sooner after shutdown, so we had to stop and figure it out.  Turns out there were a couple of answers.
The first thing we did was use a pressure tester to pressurize the system and listen and look.  What we found first were several spots where we were getting seepeage at the intake manifold-to-block and manifold-to-head joints.  Ole and Cecelie Ringstad were with me in Pensacola and helped find the first of these leaks.  We tightened a few intake manifold bolts, re-safetied, and pumped her up again, finding much improvement, but not complete success.
Intake Manifold Bolts Tightened and Safetied.
Ole Ringstad Looking for Coolant Leaks
A few days later, I once again had time to spend on Doll, and found a small leak at one of the head studs.  This created some concern, of course, having to consider the possibility of a damaged head gasket and possibly a damaged head, going back to my hot shut down earlier in March.  I was on the phone with Al Joniec, Harry Stenger, and several other S51 builders and experts as we troubleshot and checked things out.


Our next step was to remove the rocker cover, the Jessel Valve Rocker assemblies, and re-torque the heads.  Turned out the left bank was, indeed, in need of re-torquing, as a few nuts moved at 50 foot pounds on the way to a final 70 foot pounds.  The right side was closer to proper torques, but some of them needed a little snugging up, too.

Reinstalling Jessel Bases

After re-torqueing the heads, our pressures held well.  We finished reinstalling the exhaust system and other parts, safetied, and had two good ground runs with pressure holding tight.


I hope to get her flown again the week of May 8th.  We'll see how we do with coolant.

May News and Events
The Engine has to Come Out 
The photo above was taken as we made a full power ground run in Pensacola.  This was actually the second run in the past two weeks.  Here's what has been going on:
If you read the past few months' posts, you'll recall we have been working several issues and questions on Doll.  For clarity, I had flown on March 9 and had the fuel selector valve issue, had re-built it and reinstalled it and operationally checked it and inspected it for leaks, and figured we were past that issue.  Maybe not.
You'll also recall we had tightened and re-torqued and pressure tested our cooling system and figured we were past that issue.  Maybe not.
On Sunday, May 14th, I had Doll ready to fly, I thought, and started my takeoff roll on Runway 35 in Pensacola.  At about 70% of the way into the acceleration, I got a secondary acceleration, which happens occasionally and is deemed to be normal.  Other S51's exhibit this phenomenon, going all the way back to Jim's prototype.  Correspondence between Jim and Hartzell theorized that the prop blades stayed partially stalled due to torque and relative angle of attack of the blades, and that the secondary acceleration we get is due to the blades gaining "full" efficiency as the stalled portion begins to develop thrust.  Normal stuff.
I rotated at between 70 and 80 knots, but soon after airborne, got what I perceived to be another acceleration, then another, which could also be described as a series of surges, which had never happened before.  I elected to abort the takeoff, which I think was the proper move.  The drawback to the situation was that I had gotten high enough and fast enough that I was not able to get her back down and stopped before using more runway than Pensacola has pavement.  I slowly rolled past the end of the runway and whacked the four foot tall MASLR lights at the end of the pavement with the left wing leading edge before I could get her stopped.  Not really any kind of adrenalin event or anything:  Just disappointed that I had dented the airplane. 
We then began to investigate over the next few days and weeks what exactly had caused the engine surge.  We thought about prop governor, oil pressure, fuel flow, and several other possibilities.  Let's go back first to the fuel flow possibility.
Recall my fuel selector valve rebuild and reinstallation.  Harry Stenger theorized that it was possible I had screwed something up with that operation.  I had run my operational check at 3,000 RPM with ten gallons in each tank, and had pronounced Doll's fuel system healthy and ready.  We decided to do a full power run to see if anything might show up similar to the surging I got on that takeoff attempt.  We strapped her down and ran her full power for two minutes on each tank, using one fuel pump as normal, and on both fuel pumps for periods.  Nothing abnormal showed up.  No surging, nothing.
I did decide that I was going to take one more look at the fuel selector valve before checking that possibility off the list.  I removed enough interior again to get at it and, sure enough!  There was dripping at the connection of the fuel line from the valve to the firewall; the supply line to the engine.  I had failed to tighten it properly.  I couldn't believe it, but there it was.
Realize that the engine had run the day before at full power with the loose line and no hiccups, yet we had to conclude that there was the possibility that the difference between the full power static ground run vs. the 80 to 90 knot full power dynamic  condition were enough to reveal my mistake.  As Harry had predicted, it was probably sucking enough air through my faulty connection that I got the surging.  I tightened the connection and made another full power run, which, again, was normal.
Why had my 3,000 RPM operational run and leak check from a month earlier not revealed my failure?  Our theory here is that my putting only ten gallons per side for that leak check had the fuel level low relative to the fuel selector valve, such that there was no fuel at the level of the connection.  When we ran, the leaky connection might have sucked air, but not dripped fuel.  Once topped off, the fuel did begin to show itself, but I had closed up and not inspected after topping off later.  The 3,000 RPM run vs. the full power 4,200 RPM run did not show the leak either way.  Had I run at 3,000 RPM but had full tanks, I might have revealed the leak a month ago.
Now.  The coolant system:  The day after the last full power static run, I went back and did another pressure test on the cooling system.  Pumping up to 16 lbs., she lost 3 lbs. in 50 minutes.  Not OK.  I resolved to do a borescope inspection.
I removed the front plug from the #8 cylinder (left front from the cockpit), as we had been seeing evidence of coolant in that area (recall the head stud coolant leak).  Our thinking was that we would check the condition of the cylinder walls and valves and whatever else we could see.  The plug had coolant on it whan I removed it.  I then stuck a paper towel into the spark plug hole to see what I could wick out.  The photo below tells the story.
June News and Events
The Engine is Pulled in Pensacola
Before, After, and the engine ready to load for the trip to South Carolina for inspection.
Mike Goransky ("Gorilla"), on the right, and me tearing the engine down to pull the left head.  We are removing the intake manifold to allow for removal of the left head for cylinders 2 through 8, to see what is going on with the coolant in cylinder #8.  You can see the rocker cover has been removed for that side.
Al Joniec examines the #8 cylinder.  This cylinder is at the left front of the engine as oriented from the cockpit.  The cylinder walls and top of the piston looked normal.
The left bank exposed.  Number 8 is on the left.
The tan section on the gasket with the piston in the background is direct evidence of a "blown" head gasket, recognized by Robert.  Notice the blue areas of the intact gasket material vs. the darkened areas radiating from the small tan section.
Al, Robert, and Gorilla conclude that, if the heads don't show any cracks in the Zyglo inspection, we don't have any significant damage.  Robert will go ahead and pull and check the pistons, hone the cylinder walls, perhaps add new rings, and put the engine back together.
How did we get to this point?  What happened?

This is the thermostat housing box we began to use about a year ago.  The housing contains two standard automotive thermostats in parallel.  The box was designed with a small hole that allowed coolant from the engine to pass through, thereby giving the thermostats input about coolant temperature, opening to allow greater quantities to flow past to the radiator through the tube exiting the bottom of the box.  In all the testing and experimenting, we never allowed enough coolant to pass by the thermostats, and the coolant had to travel down two feet of hose to reach the box.  Bottom line:  The engine got hot and pressurized before the thermostats ever opened.


The cure for this is to run a coolant line from the box section above the thermostats to the water pump, which will allow more total flow from the engine past the thermostats, which will allow them to better respond to changes in coolant (thus, engine) temperature changes.  Cliff Fitch has already gone through the same troubleshooting sequence and has his running just right.

The box viewed from the left side.

Rear view of box.  The temperature probe fitting is shown, mounting in the chamber that houses the thermostat bulbs.

We'll probably be outside of two months before we are flying Doll again, given Robert's schedule, my schedule, and logistics.  In the meantime, we'll be working to get kit parts production amped up.  Will keep you posted.
November 2017
Call me clairvoyant, call me optimistic, call me inaccurate:  I was right when I closed our June update with "we'll probably be outside two months before flying again."  Here we sit in mid-November, and our engine is still with Robert Abernathy in Beech Island, South Carolina, being rebuilt.

Robert had other engines in line before we got ours up to him, and we have had delays in getting some of the parts we wanted, but we are now underway with our "freshening up."  The block and heads are fine, but we are reworking the cylinders and had to go to the next size pistons, and that has slowed things down.

As I have tried to update the site this weekend, I have run into technical problems with Network Solutions, mostly the inability to download pictures.  I will update as soon as these issues are cleared up.

Meanwhile, the biggest news is that Rod Bower's beautiful S-51 took flight in October with Elliot Seguin at the controls.  Check "Bower's Pony 10.1.17" on YouTube for Elliot's production on the flight.

Meanwhile, we've made some progress over the past several months on manufacturing the wing leading edges, main landing gear components, and some wing rib tool modifications.  I'll post more details and photos when we get the editing function ironed out.

Elliot Seguin in Rod's S-51.
December  News and Events
Robert and Al are close to running our engine on Robert's dyno, and I should be in Beech Island in January for the runs.  I'll post photos as soon as possible.

Meanwhile, Rod Dill and Chuck Pyritz at TPR, Inc. and I have been exploring ways to manufacture the wing leading edges.  We are close to working out a method with L3 Aerospace Technologies to pre-roll the skin, then form the leading edge in the tooling TPR has built.

In the first photo below, you'll see an error we found in our rib dimensions.  TPR has modified the rib blocks involved.  We will be shipping them to Mooney for corrected ribs. 

The second photo below shows our new main landing gear trunions in one of their machining steps.  Cliff Fitch plans to have them finished and will bring them down to Montgomery in January, if he can get out of the snow in northern Illinois.  Stiff winter has arrived.
Jim Gohm is continuing to fly his S51 in Arizona.  Rod Bower and Elliot Seguin have completed a 3rd flight out in California, going up to 14,500 feet and pulling strong power and good speed.
We hope everyone had a good 2017, and we'll all look forward to a great 2018.