N2175N is a 1979 Piper Warrior II, model designation PA-28-161, with 5000 total airframe hours, and a Lycoming O-320-D3G normally aspirated (carbureted, non-turbo) engine. The original engine was rebuilt by Lycoming in 1994 at 2000 hours. In 2011 this engine had performed admirably for 2925 hours and was showing its age with increased oil consumption and a steady decline in cylinder compressions, particularly in #4 cylinder. It was time to overhaul or replace the engine.
The 1994 engine "remanufacture" on the original 1979 engine was done at the Lycoming factory and presumably they used the original case, crankshaft, and camshaft with new cylinders. In a factory remanufacture used parts may be used only if the parts meet the specifications for new parts. This meant the low end of the engine had 5000 hours on it. Without incurring much expense to open up the engine and inspect the case, crank, and cam shafts it was difficult to discern the condition of these critical components.
We had a number of options.
With the ECi Titan Engine one gets a completely new engine built by a world-class shop. I shopped around and chose Charlie Melot's Zephyr Aircraft Engines in Zephyrhills, FL.
Aircraft have redundant ignition systems, hence we have 2 magnetos and each cylinder has 2 spark plugs, one fired by each magneto. FAA regulations require at engine overhaul or replacement the magnetos be overhauled or replaced with new units. The magneto manufacturers know this, so they price the overhaul kits very close to the cost of new. We opted for new. This meant we would need to remove the fuel pump and carburetor and ship them to Zephyr to be used during engine run-in on the test cell when the engine is started and run for the first time at the shop. So, the plane would be down from that point until the new engine was installed. Original estimate was about one month.
The process would proceed thusly:
It is the 11th of July. Zephyr Aircraft Engines was ready for the carburetor and fuel pump, so it was time to bring down the engine. Here is the old engine with the engine cowling removed. For those unfamiliar I'll try to orient y'all a bit. The engine is a Lycoming O-320-D3G - solid 1960s technology, 4 opposed air-cooled cylinders. The black metal tubing is the engine mount from which the engine hangs. The hydraulic tube sticking down from the engine mount is the nose gear strut which is also contained by the engine mount. The orange ducting connects the air cleaner to the carburetor, and connects the exhaust system shroud to the cabin heater and defrosters. (The shroud collects the hot air around (NOT IN) the exhaust system and directs it into the cabin). If the exhaust system is not obvious to you, perhaps you should stop reading now. Unlike an automobile engine the carburetor is under the engine. The sheet metal with the black fabric on top, surrounding the valve rocker covers, is the engine baffling. Since the engine is air cooled, air flow through and around the cylinders is critically important and this is accomplished by an extensive set of engine baffles. The vacuum pump is the ribbed cylinder with the red stripe at the top rear. The white oil filter is just below the vacuum pump, and below that, the fuel pump. The alternator is just below the front of the engine. The starter is on the other side.
There was method to my madness. I had a camera, a box of ziplock sandwich bags, a roll of pink masking tape, and a black felt pen. The plan was to photograph, remove components, place the bolts/screws/washers/nuts/pins/retainers/etcetera in a bag, write the contents on the bag, attach the bag to the component and label the engine location if needed.
2 weeks later I am only on day 2 of the engine removal. The propeller, spinner cone, vacuum pump, fuel pump, starter, alternator, engine baffling, exhaust system, and the carburetor have been removed. The fuel pump and carburetor were shipped to Zephyr. The oil filter can now easily be seen sticking straight out the back of the engine. Center, top frame, just behind the oil filler tube can be seen one of the 4 floating Lord Mounts. These cushions attach the engine to the tubular engine mount and isolate the airframe from some of the vibration. All four were replaced with new units. Some pink tape can be seen labeling the throttle cable, and paper towels were stuffed into holes left by the removal of some accessories.
Here is the day two view from the front. The white cables hanging down on the right are to the starter and alternator. Loose fuel lines with gold/blue fittings can be seen under and behind. The upper arch and the top two Lord Mounts of the engine mount can be seen above and behind the engine, and the nose gear tube and lower attachment points of the engine mount to the firewall can be seen below.
The tension was at a fevered pitch as the weight of the engine was lifted and the airframe tilted back and came to rest on its tail skid on large wooden blocks. The Lord Mount bolts were removed, and the engine lifted clear of the aircraft. Oh, my God, what have I done!
The engine mount can now be clearly seen with its 4 Lord Mount mount rings and its 5 attachment points to the airframe, top left/right, bottom left/right, and top center. Yes, only 5 bolts hold the engine onto the airplane.
Here we see the engine mount from the left side of the plane. The centered, paired actuators sticking out of the firewall are nose wheel steering arms. While on the ground with weight on the nose wheel the nose wheel is coupled to the rudder and steers with rudder movement. The nose wheel strut sticks up through the large lower tube on the engine mount and attaching to the top of the strut is a steering bow to which the actuators attach.
So finally, the engine mount was removed, and here is what was left.
The box at the bottom of the firewall is the cabin heat airbox and contains a cable controlled flapper to turn the cabin heat on/off. Also on the firewall is the electric (backup) fuel pump (center right), the starter solenoid (right w/white cables), the gascolator (a sump point for the fuel system) (lower right), the brake fluid reservoir (top right), and the red defroster ducting. The throttle and mixture cables can be seen propped up at center left frame.
This is the engine mount free of the airframe. It is important to ensure the structural integrity of the engine mount. But before I had it sandblasted, inspected, and powder coated, I had to remove the upper and lower nose strut bearings from the lower tube. These bearings were to be replaced. The lower bearing was easy to remove, but the top one would not budge. Rather than damage something I shopped around for a machine shop who could press out the bearing. There was a time when machine shops abounded, back in the day when cars were actually owner servicable. But it turns out few remain, and those that do tend to specialize in some automotive niche, rather than general machine services. It took a few days, but after realizing the nose strut tube was very similar to a motorcycle front fork, I stopped by Lynnwood's Emerald City Harley Davidson. 15 minutes later the mechanic handed me the bearing and refused any compensation.
I was back on track. Here is the final state of the engine mount. Pretty, ain't it? The steering bow and carburetor controls cage was similarly finished.
Obviously I took many more photos of wiring configuration, control cable configuration, safety wiring, and dozens of specific parts. Among the parts replaced were the rear spinner bulkhead, all 4 Lord Mounts/bolts/washers/nuts, all 5 engine mount/firewall bolts/washers/nuts, all the orange ducting, and a lot more.
The cover was removed from the pallet and the engine hoist used to remove the engine from the truck. It had that wonderful "new engine" smell. (Note - the astute observer may notice that the kayak carriers on the truck's lumber rack are not aligned. The front carriers are on the left, the rear on the right. Do no be alarmed, the rear cross member is removalable for easy access to the truck bed.)
The top photo shows the new magnetos (shiny, black cylinders the wires lead into) and the new wiring harness. The second photo shows the new starter ring gear attached to the pallet and a small cardboard box with our carburetor and fuel pump. Surprisingly the engine arrived with new spark plugs and a new oil filter. An astute observer may note that the oil filter has a different orientation than the old engine. This was an issue discovered later. Also the starter ring gear was wrong for my alternator and starter. A proper replacement was sent gratis, then a close examination of the old ring gear showed it to be in perfect condition, so the two new ring gears were eventually shipped back with the old engine. Zephyr was quick to address issues, refund, and offer help.
On 11 September 2011, a month after receiving the new engine and 2 months of elapsed time, we got it hung on the reconditioned engine mount. It took some time for me to get the new nose wheel strut bearings installed, and the engine mount installed on the firewall. After solving the top center nut access problem, replacing and torquing the top center nut was easy. The two bottom corner nuts were also very easy. Contrary to the diassembly, getting the new washers and nuts on the new top corner bolts was very difficult. Just getting the nut started on the left side bolt took over an hour of sweating and expletives under the claustrophobic contortionist confines behind the panel. The right side was somewhat easier taking only 30 minutes. All the engine mount firewall through bolts/washers/nuts were new. With the engine mount installed, and 4 new Lord Mounts/bolts/washers/nuts in hand it was time to hang the new engine. Because the Lord Mount bolts follow the angles of a 4-sided pyramid, it was necessary to get the engine flanges perfectly aligned before insertion of all of the bolts at basically the same time. It took three of us about an hour to get the four Lord Mount bolts inserted.
I am NOT in this photo. The gentleman on the left is my plane partner, Gregg Krogstad, a notable Seattle area photographer. You can access his website and samples of his work at Krogstad Photography. The gentleman on the right is one of our helpful, friendly hangar neighbors who offered to help out. I'd post his name, but don't have his permission. At the bottom is Gregg's dog, Chaka. At the time this photo was taken the engine hoist was still supporting the engine weight. Before removing the hoist we blocked up the front of the engine.
Aircraft are space challenged. A lot of stuff is stuffed into small spaces. Clearances are close. Things need to be assembled in order. Some nuts/bolts are barely accessible around and between obstructions. I had to build 3 special, single-purpose wrenches for specific nuts. It's amazing what a vise, a propane torch, and a 5 lb hand sledge can do.
One issue that came to light quickly was a conflict between the new canted oil filter and an oil cooler line. The old engine had the oil cooler sticking straight out the back of the engine as is visible above in this photo. The new engine had the oil filter canted at a 45* angle. The following two photos show the problem. There is not enough clearance between the oil filter and the oil line fitting to attach the oil line to the fitting.
The solution was to use the old oil filter adapter housing. Zephyr was quick to acknowledge the problem and send new gaskets. The oil filter adapter housing also contains an oil bypass valve termed a vernatherm. This valve is heat actuated and increases and/or decreases oil flow through the oil cooler depending on oil temperature. After checking that the old and new vernatherms where identical, the new was swapped into the old housing and then the old housing with new parts was installed on the new engine. This returned the oil filter to a straight back orientation. The photo above also clearly shows the two magnetos.
After hanging the new engine some time was spent finding new parts, a collection of specific new bolts/nuts/washers including alternator mount, propeller, many Adel clamps (rubber cushioned clamps). Also acquired new ducting and a complete new baffle set.
Here is a photo of the new engine baffling set. There are 10 pieces. The blue strips are soft, flexible silicone rubber seals which press against the inside of the engine cowling. Every hole was perfectly drilled and perfectly placed.
Collecting and receiving parts, and of course life, work, and other play conspired to delay progress for a number of months.
The blue silicone rubber seals against the inside of the engine cowling to create a closed airbox, through which the air passes in carefully designed pathways to cool the engine. In the first photo it may appear that the engine is mounted canted to the right side of the plane. It is not an illusion; it is a fact. Because of the huge amount of torque that is produced by the spinning engine and propeller there are induced "left turning tendencies", and this slight rightward cant of the engine counteracts most of that tendency. The top sparkplug leads are laying loose on top of the engine.
The second photo shows the installed carburetor below the engine with installed control cables and fuel lines. Rather hidden at the rear of the engine are the newly installed vacuum pump and fuel pump. The steering bow was also installed. Note the loop of tubing emerging from the slot in the forward baffle. The fuel priming system on the old engine only primed 3 of the 4 cylinders. This engine primes all 4 cylinders and the baffling was not designed for the fourth cylinder. The priming tubing is stainless steel rather then copper and so was not amenable to bending. Instead the baffling was carefully slotted.
Unmentioned in this litany is the recurring inspections, suggestions, and guidance provided by our mechanic. He kept very close watch on my work, checked bolt torques, performed function tests, answered the phone quickly, and showed up on short notice when needed.
There were a number of lesser scope things left to accomplish. All wires, cables, hoses, oil lines, and fuel line had to be secured from vibration. Seems like a small task, but it is very important to prevent chafing and it took some time. At a few thousand feet above the ground chafing through a fuel line or oil line can lead to a very bad day.
Inspection of the engine compartment found a small oil leak from an oil line fitting I had only hand-tightened. The nice, clean new engine was now soiled and I spent some time with paper towels cleaning it up. At least the leaked oil was clean.
There were a few easily remedied minor issues identified by the mechanic. However, one issue was serious and we could not resolve it on that day. The alternator was not putting out power - the load meter (ammeter) was pegged at zero. I had changed the brushes in the alternator, but was pretty sure all was well. By then we were all freezing, so I pulled the alternator, and we put the plane back in the hangar and called it a day.
Over the next couple of weeks I tore out my hair trying to troubleshoot the charging system. I brought the alternator to an auto parts store for a free test. As mentioned earlier, due to the expense of FAA regulations, these engines are solid 1960s technology and the alternator is no exception. It is a stock alternator from a mid 1970s Chrysler. The auto parts store had trouble adapting to the electrical connections - newer vehicles have combination multi-prong connectors - this alternator has posts/nuts and screws. As such I didn't particularly trust the finding that the alternator was bad, so I took it to another auto parts store and had it tested again. This time it came back good. Well, I spent many days shivering in the damp, gray cold, repeatedly installing and removing the alternator running tests with a multimeter. Eventually, I came to the conclusion that the voltage regulator was bad. I brought it home, built a resistor bridge to test the function of the unit and found it did NOT regulate voltage. The voltage regulator was blown. Luckily a friend had recently replaced his charging system with an updated system and had his old VR available. I installed the used VR, reinstalled the alternator, pulled the plane out of the hangar, and started it for the 2 dozenth time. Still no charge current.
Back to more troubleshooting. Given that the VR was good, the overvoltage relay tested good, the circuit breakers tested good, the grounds tested good, led me to the conclusion the alternator was indeed bad. Luckily the same friend with the VR had his old alternator, and I borrowed it. I swapped out the alternators, pulled the plane out of the hangar, and started it for the 2 dozenth and 3rd time. CURRENT! We had current!
Thank God.
Subsequent speculation has led me to suspect I had blown the battery, VR, and alternator, by forgetting to disconnect the battery before starting my disassembly of the engine. I likely inadvertently and unnoticed shorted out the system. A somewhat expensive mistake.
Once again our mechanic looked over the plane, at the work I'd done to fix the charging systems as well as some other minor issues. All was well. It was time to button up the cowling, sign off on airworthiness, wait for a weather window, and fly the thing.
At the airport, Saturday, 17 December, dawned a balmy, overcast 30F with temperatures climbing to 45F at noon. The reported weather (METAR - Meteorological Aviation Report) at Paine Field and Arlington was similar, temp 7-9C, cloud cover scattered at 10K' at Paine, clear skies at Arlington, visibility over 10 miless, and light winds out of the south.
Post Maintenance Flight Test
Started up about 1:30 pm, allowed to idle about 4 minutes, then taxied to a quick run up. Oil temperature gauge had not moved, waited a few more minutes then taxied back to the hangar. Gauge came off the peg just before shutdown. Jockeyed the plane back around, started up, and headed to the runway. Full brakes, and slowly applied full power on runway 15 gave about 2250 rpm. All engine gauges were in the green, everything looked good, released the brakes to an easy takeoff.
Slowly climbed in the pattern as the oil temperature climbed. Left pattern altitude on downwind and continued the climb with WOT to the east. The OAT at 4500 was 11C (temperature inversion) and a leaned WOT gave 2550 rpm and 125 kts. From the POH performance chart this was about 72% power. Circled Harvey field from PAE on the west to Monroe on the east, and Lake Stevens on the north and Riley Slough on the south. Circled for 2 hours at 4500 MSL, WOT, 2550 RPM, monitoring closely all engine gauges, and expecting the engine catastrophe at any moment.
At about 4pm, after 2 hours at 4500, started the descent to a gentle landing on runway 15. Taxied back to the hangar and shutdown to find oil dripping out of the cowling onto the nose wheel pant. The inside of the engine compartment and the belly were coated with clean oil. It appears about 2 quarts were lost during the 2 hour flight. The initial start up and leak test on 28 November did not find this oil leak. Despite the leak all oil temperature and oil pressure remained steady and in the green the entire flight. Below is the boring flight record.
By the time I refueled and got back into the hangar it was 4:30PM and dark. I pulled the top cowling, and used a shop light to look around the engine compartment. The leak appeared to be centered somewhere around the oil filter. The oil filter was tight. The oil filter adapter gasket appeared sound as did the fuel pump, the vacuum pump, and the magnetos. There was a pool of oil in a hollow on top of the oil filter adapter near the oil temperature sensor. The sensor was loose, so I tightened it up and cleaned up the oil. The leak did not return.
The plane had flown great and the engine never skipped a beat. Cabin heat worked well. The throttle seemed to have a tight spot about halfway from idle to wide open. The mixture control operated well. The new pilot-side yoke u-joint made a noticeable difference.
After assuming the plane would be down for about a month, just over 5 months had elapsed.