Engine Runs

I didn’t see it coming, we had been working daily on Sis since returning from Thanksgiving. We were supposed to head out of town for Christmas the next day, but had to get a few more things done while the weather was cooperating.

The restorer opens up the hangar door to the mostly blue sky outside.  Let’s see what we get, he says.  

It took us some effort to pull the two thousand pounds that is Sis out of her hangar and get her lined up into the breeze coming through the hangar row.

Sis is a 1947 Beechcraft Bonanza model 35, one of the first 1000 off the assembly line. For all intents and purposes, she is my big sister as I have grown up flying with her and now am her caretaker.

I think she was sitting a bit higher on her gear in anticipation of what would come next.

Finally, we were both sitting inside Sis, one last discussion before we began.

I’m in the left seat with my feet on the only set of brakes.  This is the first of the engine break-in runs called for by the manufacturer after the cylinders were installed.  The restorer will monitor the engine and make adjustments within the scope of the manufacturer’s specifications.

Ok, here it goes.

Battery master on, boost pump on, fuel confirmed in system – everything looks good.

I open up the pilot window and call out ‘clear prop’ then turn the key to engage the starter.

The starter didn’t want to engage. The restorer said to let off the key and then try it again, to give her starter a bump.  It took a few bumps but the starter turned over and she ran.

Boy did she run!

Our eyes were glued to the JPI engine monitor for the duration of the run.

I think my jaw was on the floor at first as everything we have been working towards is falling into place. Pinch me – this is really happening!

Coming back to reality, I remind myself of the break-in procedure, which calls for low RPM on the first start. We stayed around 750 RPM to begin with increasing to 1000 RPM as the engine warmed up.

Outside temperatures were in the 40’s which impacted the oil.  I’m sure the restorer was looking at both oil temperature and pressure but I only recall the pressure from the first run.  

Oil pressure started off on the low side of normal then went over 100 PSI for some time eventually evening out within the high side of normal over the course of what felt like forever but 

The oil pressure was high because of the cold temperatures.   The procedure called for running the engine for 3 minutes.  The restorer elected to run until the oil evened out, which ended up being about 4 minutes.

When the oil pressure was stabilized, the restorer called for a shutdown and I pulled the fuel mixture control out which shut Sis down.  

Looking under the cowling after the run was completed, I could see something smoking which the restorer told me was Marvel Mystery Oil left over from the earlier engine work.  

Oil pressure was high most of the run, but lowered to normal near the end.  

Think Sis smiled a bit as we pushed her back into the hangar.  

The oil level looked good afterward, the restorer was happy with everything.  

In discussing the next week, we decided to take more items no longer needed at Moraine back to the restorer’s hangar at New Carlisle before we lost daylight and we would head up to Chicago the following morning for the holiday weekend.  

The break-in procedure called for more runs before the flight.  The next run will take the engine to a higher RPM and ensure oil pressure is becoming more stable than during the first run.  A taxi with the application of brakes to ensure they are working properly will also occur with a yet higher RPM run mimicking what occurs at takeoff.

Day 2

The weather held until after our return from Chicago, while not as warm as the previous week it was still comfortable for getting things done at the hangar albeit in more layers and hot tea than before.  Low ceilings and a light rain shower were all that happened this day but we were able to get the next run in.

It was a windier day for the next engine run. The restorer turned Sis toward the end of the hangar row away from the taxiway to get better airflow for the engine.

This time, she starts with a minimum amount of fussing.  

Temperatures are again in the mid 40’s, the restorer says it will take the oil longer to come up to its operating temperature of 100 degrees on days like this. Temperatures any colder will require preheating.

Oil pressure should come more in line by the end of the run, the restorer added. 

After another set of runs under 1000 RPM, the restorer exited the airplane while the engine was running to examine everything from the outside. He also took some pictures.

When the restorer returned, we increased the RPM to 1500 RPM while I held the brakes.  

The oil pressure was looking much better, still not entirely normal but closer to where it should be. 

The restorer again said he was happy with things and called for shutdown, this time by turning the key to ensure the magnetos were working properly. 

I didn’t understand everything happening, but I felt that Sis was working as she should.  

As we pushed Sis back into her hangar afterward, discussing what we were comfortable flying in for her first flight took on a new meaning.  

We were beginning to look at weather reports for more information than before – we had only been concerned with engine performance on the ground up until now. Predicated on another successful run, it next would be a matter of having good enough weather to fly!