To Shut Down or not to Shut Down? Part 2

By Matt Odenbrett

Fast forward ten years…

I had long since moved away from the northern Prairie and was now flying single-pilot air ambulance for an operator in southern California. My company operated a fleet of Cessna C421C Golden Eagle airplanes, which had the same Continental GTSIO-520 engine as the Cessna 404 Titan.  My years of experience operating both the Cessna 404 and 421 were put to good use by my employer.

One night I was called out to do an air ambulance flight at 11 p.m.  This was a normal occurrence. I met my medical team at the airport, and we loaded their gear into the 421 then launched for a short flight to the desert to the east. I stayed with the airplane while the medical team went to the local hospital to retrieve the patient that required pressurized transport back to the hospital in the big city. They arrived back around 0215 local time, and we loaded the patient and the team settled in while I started the GTSIO-520’s. We took off from the uncontrolled field, and I contacted Los Angeles Center and received my IFR clearance for the 30-minute flight back to home base.

All was normal, and I was enjoying myself as I levelled off at my cruise altitude of 10,000 feet. Per my checklist, I set cruise power, leaned the mixtures to 50 degrees rich of peak EGT, then looked outside at my engine nacelles.  Both the 404 and the 421 have louvres in the upper cowling for engine cooling, and at night one can view the reassuring glow that can be observed coming off the turbo-supercharger as it spins inside the 1,400F-degree heat of the engine exhaust. I always made a point of checking the glow to ensure I had set my mixtures at the correct temperature.

On this flight, when I looked at my left engine, something did not look right. It was a moonless night, but I could see that the louvres appeared darker than they usually would against the turbocharger’s glow. Knowing something was amiss, I reached down for my flashlight and pointed the light at the louvres on top of the nacelle.

Black.

There was a black liquid substance sitting on the top of the louvres, which were painted white. Not good. I moved my flashlight down to the side of the nacelle. There, I observed a three-inch-wide black streak that appeared at the junction of two of the cowl pieces, and it was painting a stripe in the slipstream towards the upper side of my wing. This is really not good!

I checked my engine gauges. Both oil temperatures and pressures were in the normal range. Time to take stock of the situation. I knew from years of operating and hangar flying with other pilots that the Continental GTSIO-520 has a history of cracking the engine crankcase, and by the looks of what I saw, I surmised that this was the problem I was facing. I knew that had I lost an oil cooler or an oil line to the turbo I would have had an engine failure by now. Well, that meant that I once again had an engine that was slowly bleeding to death, but how long did I have? This is where my previous experience came into play.

A quick check of the Garmin 530 GPS showed I had less than 20 minutes flight time before landing at home base. There were no other airports closer, and I was over mountainous terrain so continuing on to my destination was my best choice. Fine, I thought. If the engine quits on me, I am high enough to make it safely to my destination. If I start losing oil pressure on my left engine gauge, I will declare an emergency and ask for fire trucks to be rolled out as a welcoming party. Until that happens, I will continue. No need to make a Mayday call because I am not in an emergency situation. I know that even if my oil pressure begins dropping I should have maybe 15 minutes or so to run my left engine before I lose so much oil that I have to shut it down.

The oil pressure gauge stayed at its normal indication, and never dropped all the way to touchdown. Once off the runway I cancelled my IFR flight plan with SoCal approach, taxied to the ramp, unloaded my passengers into the waiting ambulance, and then called my office. The left nacelle was painted black from the side of the nacelle forward of the wing all the way to the back. More oil painted the top of the nacelle from the louvres to the rear of the nacelle. The engine clearly was toast, but it hadn’t leaked enough oil during the 30-minute flight to cause a failure. I was very thankful I hadn’t been on a much longer flight, but this night’s flight was merely one that was just a bit outside of the normal routine.

I later asked the mechanic who inspected the engine how much oil I had lost in that engine. Three quarts.  Not bad.

The old engine was removed and a new one installed after a few weeks. A couple of air ambulance flights were performed with it and everything appeared normal. Thanks to this, I had no qualms when I was once again dispatched out to the desert at 11 p.m. at night. This was a routine operation. So once again I take the medical team out to the desert, they retrieve the patient, and we depart around 0230 to return to home base. Everything is normal, and there is no weather anywhere in SoCal. The tower was shut down for the night, so when I was about 35 miles from base, I clicked on the approach lights on the airport’s CTAF and was rewarded with the Rabbit strobes showing me the path to the runway. All looks great, and the Garmin 530 is telling me it is time to begin my descent, so I called SoCal approach for my descent clearance. I was cleared from 10,000 feet to 4,000 feet and told to report the field in sight for a visual approach. I replied I would do so when I got closer and began my descent.

As I dialed my descent rate into the autopilot and we started down, a big red light illuminated on my instrument panel. What the heck? I look down and identify the light as my left engine fire warning indicator! Seriously, what the heck!?

I check my engine instruments. Everything appears normal. I look at the offending engine nacelle. The usual glow from the turbocharger is all I see. No smoke. No flames. Yet I have a fire warning indication.

Do I really have a fire?

I knew this was a brand-new engine and it had only flown perhaps eight hours. It wasn’t even through the break-in phase of operation. Maybe there was a problem with the fire warning indicator, and I had an erroneous fire warning indication. Maybe, but there wasn’t any way to know for sure. Better to treat it as if this fire warning light is correct.

I throttled the engine back by two inches of manifold pressure to see if the fire indicator light would go out. No change. Okay, that does it. I reached down to the fire-warning indicator, lifted the protective cover from the dual-purpose indicator light and push-button switch, and pushed it. This push-button activated the high-pressure Halon fire extinguisher into the left engine inside the nacelle. There goes $3,800 of fire protection. Will it work? After maybe ten seconds, the fire warning light extinguished.

Hmmmmm….  It seemed to me that perhaps I really had some kind of fire, even if I couldn’t see any indications other than the indicator light itself. While my head was continuing to tell me that it likely was an erroneous indicator, my training said to treat the situation by the book, i.e., treat it as a potential emergency situation.

By now I was descending through 8,000 feet and less than 25 miles to my home base. Should I say something to SoCal? Yes, I better do that. What if the fire warning light illuminates again? Better safe than sorry.

I pressed down on my push to talk switch and spoke into my headset mike, “SoCal Approach, Medevac 745 Charlie Alpha, PAN-PAN, PAN-PAN, PAN-PAN! I have had a fire warning indication in my left engine nacelle. The light went out when I hit the fire bottle, my engine is running fine, instruments are normal, and I cannot see any flames or smoke, but please be prepared to roll the fire trucks in case I ask for them.”

“Medevac 745 Charlie Alpha, SoCal. Are you declaring an Emergency? Please state how many souls are on board.”

“SoCal, 745 Charlie Alpha, negative. I am not declaring an Emergency at this time, but please be prepared in case I do. I have four souls on board, I have the field in sight and am ready for visual approach.”

“Medevac 745 Charlie Alpha, roger. Cleared for visual approach.”

I continued to bring my power slowly back to approach setting, and out of habit I was proceeding to the final approach fix for the ILS. Everything seemed ok, but I was still on edge. I considered shutting down my engine, but I decided against doing so. So long as my left engine continues to produce power with no smoke, flames, or other fire indication I would continue to leave it running.

My medical team had seen the fire warning light from the cabin and were worried. I told them, “As you can see, we may have a problem, but I cannot confirm it. Everything is fine for now but be prepared for an emergency evacuation if I call for it.”

Two miles from final approach fix, it happened again. The Fire Warning Indicator light on the left engine illuminated! I had already used my Halon bottle, and there was no back up. Doggonit, it is time to call for the Marines.

“SoCal, Medevac 745 Charlie Alpha, MAYDAY MAYDAY MAYDAY!!! I have another fire warning indication from my left engine. Please roll the fire trucks!”

Now in retrospect, I know it was 3 a.m. at the time. The tower was shut down, so the guys who usually would call the fire trucks out weren’t there. However, I was still shocked when SoCal made their reply to me.

“Medevac 745 Charlie Alpha, you wouldn’t happen to have the phone number for the local fire department, would you?”

My jaw dropped down to around my ankles. I felt like smacking the palm of my hand completely though my forehead and into the rear of my airplane! My first thought was, “Why am I even talking to you?”  However, civility and the necessity of running my before-landing checklist precluded me from saying this. Instead, I replied, “Uh, no. Sorry, but I am a little busy right now.”

As luck would have it, I wasn’t the only person on the frequency. A third party chimed in.

“Mayday call, this is Police One. I have the number for the fire department. Do you want me to call them for you?” It was a helicopter operated by the local police department! Wonderful!

Gratefully, I replied, “Yes, I would appreciate that very much! Thank you!”

SoCal came back on, “Police One, thanks for the assistance. Medevac 745 Charlie Alpha, change to advisory frequency. If able, report when on the ground. Good Luck.”

I changed over to CTAF, and completed my before-landing checklist. I then did yet another assessment of my situation: The fire-warning light is still lit, but the engine is running normally and no smoke or flames present. Shutting down the engine right now doesn’t make any sense. If I was going to shut it down, it would have been before I had dropped my landing gear. No, continue the approach and be prepared for emergency evacuation if necessary.

My approach was normal, and so was the landing. Somewhere during the approach the fire warning light extinguished again, but I was so intent on getting on the ground in one piece I didn’t notice it was out until we were rolling down the runway towards the end. As I slowed to taxi off the runway, Police One called to me.

“Mayday call, Police One. I just raised the fire station. Do you still require them to come out?”

I looked again at my situation for the umpteenth time in just ten minutes. No smoke. No flames. No fire-warning light. Left Engine operating normally at idle power and all engine instruments gave normal indications.

I called back, “Police One, Medevac 745 Charlie Alpha. I am fine and will taxi to my ramp on my own power. You can tell the firemen to go back to bed. Thanks for your help!”

As I taxied to my ramp I called to SoCal, reported on the ground and no fire, so please cancel my mayday. They acknowledged and said good night. I continued to my ramp, got the medical team and patient into the ambulance, then called my dispatch and told them the story and prepared myself for the fireworks that I knew were certain to follow the next day.

General aviation pilots know that when an emergency is declared they may have to submit a written report to the local Flight Standards District Office, if requested. By contrast, when a commercial operator declares an emergency, a written report is required. Furthermore, anytime a pilot says the word, “Fire!” to ATC, it automatically sets into motion an official investigation. Every part of the operation is subject to an audit, from the maintenance records to pilot training, to operations manual to standard operating procedures for the charter operator.

The investigation into my Mayday call found the culprit of the fire warning. Inside the Cessna 421 engine nacelle there is a cable run that is placed along an engine mount and passes near the turbo-supercharger. It is close enough to the turbo to require a heat shield. The asbestos heat shield is normally secured to the cable run and engine mount by safety wire. During the new engine installation, this heat shield had been secured using plastic zip ties instead of safety wire. The plastic zip ties had held up for approximately eight hours of operation before the heat from the turbo melted through them. When this happened, the heat shield fell against the turbo-supercharger, and began flaming onto the heat sensor at the rear of the compartment, thus setting off the tire warning indicator in the cockpit. So I actually did have a fire in the nacelle that night, even though I could not see it. Had it continued to flame, I definitely would have had more problems to deal with, but since I was landing, the flaming stopped once the turbo cooled down.

I was not faulted for my performance. In fact, my chief pilot said he wouldn’t have done anything differently. The FAA investigators were satisfied with my written report and never asked any follow-up questions.

There are lessons to be learned here for both single-engine and multi-engine pilots from these stories. The horizontally opposed, air-cooled engines we operate are a relatively simple, robust design whose origins date back nearly a century. However, they are far from being bullet proof. Knowledge of an engine’s design and how it works is key to making critical decisions necessary to survive an in-flight emergency when something goes wrong. 

Experience is a great teacher, provided one remembers the lessons learned. When I discovered the oil leak on my air ambulance flight, I knew I could continue for some time before I lost so much oil that I would have to shut down the engine. It is always preferable to continue to operate an engine that is producing power unless a situation requires otherwise. Since I was over mountainous terrain, I had no desire to perform a precautionary shut down of my engine. Such an action would immediately place my flight into an emergency situation, which is not a desirable outcome. As I had mentioned, if I would have seen a loss of oil pressure I would have declared an emergency immediately, but I still wouldn’t have shut down the engine. Just keep running the engine until it tells you it can’t run any longer. Engines are much cheaper than lives.

The engine fire was a more complicated problem. Any in-flight fire is an emergency. It is imperative to get the airplane on the ground as quickly as possible. I once read a report from someone more knowledgeable than I, that studies have shown if an aircraft lands within the first 15 minutes of detection of an in-flight fire, the chances of surviving the emergency exceed 90 percent. Once that 15-minute limit is exceeded, the chances of survival go down very quickly. But in my case, I had conflicting information. Sitting in the left seat of the Cessna 421, I was looking directly at the engine nacelle out my pilot’s side window. This sort of visual confirmation can be great, but it also prolonged the point where I did declare an emergency. However, I was within the final 10 minutes of my flight, and again without any other indications of a fire or unusual engine indications, I was reluctant to shut down what was an otherwise perfectly running engine.

Situation awareness plays a role as well. In all three incidents, I was in cruise flight but relatively close to either my departure airport or my destination. In the 404 we made the prudent decision to turn back before we were too far away from our departure field. During the incidents in the 421, I was so close to my destination that my best choice was to continue, rather than turn back or divert to a hypothetical alternate. Had I been on a mission to a more distant destination, my actions would have been far different!

In the end, the decision to shut down an engine while in flight is highly dependent upon many variables, so there really cannot be a whole lot of hard and fast rules. An engine failure on takeoff is an easy decision. A catastrophic failure of an engine in flight is another. Same goes for a verified engine fire. But as for the rest, good judgement must be exercised. 

I am sharing my experiences for my fellow pilots to ponder and use them as examples of scenarios to consider during training and flight planning.

It is my contribution to the old question, “What If?”

Editor’s Note: Please see Part 1 of Matt Odenbrett’s story in the May 2022 edition of In Flight USA, online at www.inflightusa.com or call our office for a free copy: 650/358-9908.