Our 2006 Flight Design CTSW in flight near San Leon, Texas.
Our Flight Design CTSW had been up in Denton, Texas for about five weeks getting her yearly conditional inspection, some preventative maintenance I wanted done, and replacement of all the rubber hoses used to run its Rotax 912 engine. I was ready for the airplane to come home. It had taken several weeks longer than expected due to weather delaying my delivery of the aircraft to the shop, a training interval for the mechanic, and a nasty surprise that developed during the last part of the work. A spark plug in the number four cylinder head had stripped during removal. (More on that in Part 3.)
The stripped spark plug removed from the #4 head.
The mechanic informed me that Rotax had removed any kind of repair of the spark plug cavity from the approved procedures, implying his only recourse was to replace the head. That added a week to the overall timeline and, worse, about two thousand dollars of expense we were not prepared for. I didn’t see I had much choice if I wanted to fly the airplane out, so I approved the purchase and installation of the new head as he recommended.
Getting and retrieving an airplane from a shop some two hundred fifty miles away is always challenging, but I had taken it there because the mechanic was both Flight Design approved and Rotax certified. I had flown it up and my wife had arrived later by car to pick me up and continue a family trip to Missouri and Kentucky. Getting the airplane home became a bigger issue. It was a five-hour drive (another five hours to return), a ticket on Southwest airlines (that would cost about $250 and you still had to get to Denton) or someone in another small airplane had to fly me up.
My planned GPS course in and out of KDTO from KLVJ. It is designed to avoid any Class B or D airspace in case weather or ATC clearances preclude entry.
The shop had mentioned they had a 205 they might be able to give me a lift in; so, I asked about they might do that so I could go get the CT. That airplane wasn’t available but they had someone else with an airplane who might be able to come get me; we arranged for me and that pilot to meet me at the Pearland FBO at 9 a.m. on Monday, July 3rd. He would be flying down in a Bonanza; it was a VERY nice F33A. He arrived and we left Pearland closer to 9:30 a.m., sneaking out under the floor of the Class B past West Houston airport, before eventually climbing to 4500 feet and leveling off. It was a very smooth ride, disturbed only by a few bumps due to the heat of the day. I was looking at the cumulus clouds dotting the skies around us while thinking about my trip back; daytime heating would grow them upward like flowers stretching for the sun. If I was quick getting back, I could get above them and avoid traveling in the hot, bumpy air below, something that would be impossible if they merged into a broken layer. Light Sport rules forbid overflying a ceiling so that you couldn’t tell where you were over the ground by looking down. Once I got Basic Med under me, I could fly my Light Sport airplane under Private Pilot rules and cheat that, but for now…
David Shulman, the pilot and owner of the Bonanza, was a professional pilot, and he talked about how he got there as we headed north. He had every approach control frequency between Houston and Dallas memorized, and we monitored Houston and then Waco’s approach controllers as we made our way. He aimed the airplane directly at Arlington’s Class D airspace at the bottom of the Dallas Class B, descended to 2500 feet, and requested clearance through the area from the tower, which it quickly approved. As soon as we zipped past, we quickly descended to 1500 to crawl under the floor of DFW Class B as we headed toward Ranger VOR, just south of Denton. Flying slightly west of a direct line to the fix to miss the western edges of the Surface to 10,000 DFW Class B, we traveled only a few minutes more before Denton was in sight and we were talking to their tower. They had us run a left downwind to runway 18 at two thousand feet and follow in some other traffic, which David did in a quick and professional manner. Moments later, we were shutting down his Bonanza on the ramp to the shop where my CT was; my airplane was sitting underneath an open hangar door in obvious anticipation of leaving soon today. I hoped to do exactly that.
After thanking David for a pleasant flight, I made my way to my airplane, did a quick look over, dropped my flight gear in its cockpit, found its mechanic, and had a chat. We discussed what had been done and how it had gone; he told me the logs were in the cockpit and the removed parts were there, too. I took a look at them and reviewed the log entries; happy with what I had found, I paid the bill (which was a bit lower than I had expected), and started preflighting the airplane. I didn’t find anything unexpected, so I pulled the airplane out of the hangar and got the cockpit ready to go. I ran my weather brief from my phone, turned on my Go Pro, an external GPS, and an iPad mini, called “CLEAR PROP!” and started by airplane up. My main navigational instrument was a Garmin 496; when I powered it up, I could barely see its screen. Considering it unusable, I shut the airplane back down, popped the 496 out of its holder, and started stepping through its settings. The backlight had somehow gotten turned down; I ran it up, reinstalled it, and restarted the CT. Once I was happy everything was ready to go, I gave my airplane some throttle and started to taxi.
At the end of the ramp, I stopped and called Denton Ground for taxi, also informing them I’d be requesting flight following. Using flight following usually had given me the most direct routing to Pearland. Once I was airborne, Regional approach would ask me what heading I wanted; I’d tell them “one eight zero” and they’d clear me south just west of the DFW surface class B at 3500 feet. I’d hold that until I was out of their hair and then turn a bit southeast to point at the west side of Houston’s Class B. Denton Ground gave me clearance to taxi and came back quickly with a squawk and a frequency for Regional, which I dutifully repeated back. I taxied south to the run-up area near the approach end of runway one-eight, did my take-off checks (including a run up, which was normal), dropped the flaps to fifteen degrees, and then taxied forward to the hold short where I gave tower a call. The controller asked me to “hold short”, which I acknowledged, nudging the nose of the airplane to the right to be able to see down final better. One Cessna later, the tower cleared me to go; acknowledging the call, I pushed the throttle forward, steering a long arc to the left, and hitting full power as the aircraft reached the runway centerline. I rotated at 42 knots, and the airplane leaped off the runway, climbing away at about 800 fpm. Right at about a thousand feet AGL, the tower approved a right turn out for me and advised me to switch up to Regional departure. I turned, acknowledged, switched frequencies, and called Regional, reporting in passing seventeen hundred. Regional answered immediately, letting me know I was in radar contact and giving me the latest altimeter setting. I continued the climb up toward twenty-five hundred as the realization crept in that I wasn’t going to be offered my usual course south. Must be holiday traffic, I thought. No worries. The course I was on would carry me southwest to the western edge of the Dallas Class B, where I would turn south and eventually southeast toward home.
I overflew Propwash and continued at 2500 feet until I hit Copeland where the floor of the Class B moved up to 5000. I shoved the throttle full forward to climb to 4500 feet and raised the nose to hold Vy. And when I did, I noticed both more vibration than usual and a barely perceptible series of “skips”. In all the time I’ve flown the CT, I had never felt anything like it. At my target altitude, I pushed the nose over to level flight; and as the airplane accelerated, I pulled the throttle back to cruise rpm, i.e., 5200. The vibration and the skipping went away.
I didn’t know what I had, but I knew something wasn’t normal. I continued to cruise level for a few more moments, but then pushed the throttle up to full power to see what would happen. The vibration seemed to return, vanishing as soon as I backed off the throttle even a little. Did I have a real problem here or not? After all, I had been out of my airplane for five weeks and I knew I was a bit reactive, knowing the head had been changed out and the most likely time for any issue is after someone’s done major work on your airplane. I felt like something was wrong, and I needed more assurance there wasn’t before I continued to trek toward Houston. I rolled into a medium bank right and pulled the power back, called Regional to let them know I was stopping my progress but didn’t get an answer, and descended to 2500 feet before leveling off heading southwest again. Regional called and asked what my on-course heading was going to be; not yet ready to abandon the idea of continuing home, I responded I would be turning to 180 shortly and then shoved the throttle to full to climb back to 4500 feet. Oil pressure, oil temperature, and cylinder head temperatures all were normal; but once again, the vibration returned at full power. After a few moments of experiencing it, I turned right, arcing back to head back to Denton in a descending turn that leveled at 2500 feet.
By now, my gyrations had gotten the attention of Regional approach, and the controller asked me if I needed any assistance because she was showing me heading northeast. I told her I had a problem “but it wasn’t big” and I was returning to Denton. She asked me if I needed assistance there and I responded in the negative; I didn’t feel I was in “emergency” territory yet, though I was prepared to go there if needed. I pushed the throttle up to full power as I cruised back toward the field at 3500 feet; the RPM pushed up to 5200 but that’s where it stayed. I felt like I usually would see the engine creep higher than that at this altitude; I was more convinced than ever something wasn’t right.
Because the Rotax 912 engine has twin carburetors that have to stay in sync, vibration issues are often due to the carbs being out of it. I had experienced that in flight when an air tube that keeps them together popped loose; there was a very increased vibration in the midrange, about 4000 RPM; at operation below or above that range, it smoothed out. It didn’t feel like what was happening; and though I couldn’t rule a carburetor issue out, I also knew that the most likely place for an issue was in the head since that component had been recently changed. It was a lesson I had learned not only as a pilot but as a NASA safety engineer dealing with the space shuttle; we often performed a risk analysis (though I didn’t do that one personally) to examine what a maintenance activity would perturb before approving its implementation.
The engine was producing good power and the gauges still looked good, but I was hedging my bets by staying at 3500 feet as long as possible. (The Class B floor was 4000 there.) My next checkpoint was Propwash, an airpark with a single north/south runway, and I could see its white block buildings clustered around the runway. Regional called, recommending I start a VFR descent, which I did. It was accompanied by the smell of burning oil. I had never smelled that before when flying the CTSW, and I now knew the situation was bit more serious than I had first thought.
Insert shows gauge location. Background shot shows start of approach into Denton. Look at where the “green” ranges are. Engine gauges are showing nothing unusual even though I’m smelling burning oil.
I dialed up the tower, reported my position, and requested a full stop landing. The tower gave me an immediate clearance to land. There were several aircraft in the pattern with me, and the tower controller mentioned as I swung into downwind that he had a departure to get out, which I thought I saw sitting at the hold short. The last thing I was going to do was allow a downwind extension to get a departure out…so I was keyed to declare an emergency as I passed abeam the approach threshold. Before I had to say anything, the tower asked me to make an immediate right base to help them with sequencing, and I happily and immediately complied. I kept the flaps up to keep up my approach speed and get on the ground sooner; I made an uneventful landing and taxied back to the shop the trip had started from.
I shut down the CT, got out, and opened the little oil door in the cowling to see the inside full of smoke.
I sauntered off to find some mechanics; mine had gone to lunch but the head guy was there, working on another airplane. After telling him I had experienced some “abnormal vibration and loss of power”, I pulled out my iPhone, texted my wife to tell her I had returned to Denton because of a problem, and looked over at the CT. Oil was flowing down the nosegear strut!! I took a picture and then fetched the head mechanic and he did the same as he also called my mechanic back from lunch.
The CTSW nosegear strut covered with oil from the leaking seal some minutes after landing.
When my mechanic got there, it only took him about a minute to pinpoint the oil leak; one of the push rod tube seals on the head that had been replaced was leaking. He said he had used seals that didn’t have a shelf life, pondering whether there might have been a material failure, and that pinching during installation was also a possibility.
The push rod seal after removal with damaged areas shown.
In any case, I left it up to him to go work. I wasn’t going anywhere else in the CTSW today; that was for sure.
While the head guy worked on getting me home, I grabbed my flight bag and my gear and walked up to the FBO that had some air conditioning to be comfortable while I waited. David agreed to run me back home later in the day; but he couldn’t get there until 6 p.m., so I spent the next four hours thinking that, while I was not happy about the problem or the additional delay getting my airplane home, I was very happy the incident had turned out okay and neither me nor my airplane had gotten hurt. I had discussed the failure with the mechanic; when I had suggested to him that the ultimate result of pressing ahead would have been engine oil starvation and seizure, he agreed and said he could not tell me how long I would have had before I would have encountered it. The one thing we both felt was right was…I would not have made it home without becoming a nightly news story, either because I performed an emergency landing (either successfully or unsuccessfully) or had chosen to use the airplane’s Ballistic Recovery System.
I had made the right decision…not only because of my experience as a pilot but because of my experience as a NASA safety engineer at the MER Safety Console during the Columbia accident. The engineer actually on duty when the crew was lost was Dave Witwer, one of my best friends, a fellow pilot and CFI who now flies for United. He and I had many talks about the value of following your feelings and taking action when you feel something is wrong. We are both strong believers in the value of intuition, which is often confused in the engineering community as operating on “emotion”. They are not the same. Intuition is the subconscious synthesis of your experience and knowledge; when the data is not there or is lying to you, it may be all you have. You ignore it at your own peril; paying attention to it can often save your life. In this case, it saved both me and my airplane.
And the role my intuition would play in getting this whole thing resolved was not over, yet…