The last week of April 2023, I was in Las Vegas sitting at an FBO waiting for dispatch to call. I am an air ambulance pilot flying the venerable Lear 35 twinjet around the country, moving patients to critical and advanced care facilities.
We dropped a patient the previous evening in Sin City and were waiting for our next mission. As late afternoon approached, I was expecting a call about what hotel we would be in that night. The call came, but not as expected. The direction was to gather the crew (first officer, flight nurse, and flight paramedic) and get to Chicago Midway International (KMDW) as soon as possible. One of our other aircraft developed a technical issue after taxiing with a patient on board that was awaiting transfer to New York for surgery.
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I texted my twin jet crew to get to the airport as soon as possible, then quickly planned the flight, ordered the fuel, and completed the preflight while my fellow crewmates arrived and got their pre-mission tasks accomplished. We manned up, launched with full fuel, and started our climb to FL 350, heading northeast toward Chicago.
We climbed fairly quickly to FL 350. After my copilot accelerated and set cruise power (it was his leg), I confirmed that we were on track with our fuel usage. Then we settled in for a long, boring cross-country. Or so we thought…
The problem started when the right engine turbine temperature (ITT) started fluctuating at a rapid rate. I believed this to be a gauge or sensor issue since all other engine readings were normal. I even pulled out my smartphone to video the abnormality for maintenance. I fully expected the gauge to fix itself before we landed because that is what old airplanes frequently do (this airframe was about 42 years young).
A few more minutes pass by and now the right engine ITT variations are increasing, shortly followed by both the turbine speed and fuel flow fluctuating. OK, now I am getting a little concerned. I advise center that we are having engine abnormalities and want to return to Las Vegas. Then I pull out the pilot checklist (QRH). As I am executing the abnormal engine checklist and reviewing the single-engine procedures, the right engine rpm steadily decreases to below flight idle, and the aircraft is yawing significantly from the differential thrust. Rudder trim fixes the yaw issue, but surprisingly we do not have a single caution or warning light. All electrical, oil, and fuel pressure gauges and lights are normal even though the right engine has flamed out.
I advised ATC that we had lost an engine and would not be able to maintain altitude. A controller immediately gave us a lower altitude and asked our intentions. I told the controller we would keep going to Las Vegas. ForeFlight indicated we could reach there with a 900 fpm descent rate. Once we got lower, we would be able to maintain altitude with one engine operating. I told my copilot that we would attempt a restart once we got down to FL 300, the top of the restart envelope.
Passing FL 300 the left engine now started displaying the same abnormal engine variations that the right one previously exhibited. At this point I told my copilot (it was his first jet job and just over 100 hours in the aircraft) that I had the controls and told him to attempt a restart of the right engine using the QRH procedures. I also advised ATC of our impending total engine failure and asked for clearance to the nearest airfield. I quickly looked at ForeFlight on my iPad and saw that Page, Arizona (KPGA), was within gliding range.
Time for that full disclosure stuff… I am a CFI in airplanes and gliders, and actively teach in gliders. The Lear 35 has a nominal glide ratio of 12.1:1. We had a 40-knot headwind, but using a conservative 10:1 glide ratio at FL 300, I knew we could make Page Airfield.
The left engine continued to degrade to a sub-idle condition but was technically running. The yaw from the asymmetrical thrust was now gone, and the rudder needed to be retrimmed. The right engine was windmilling but would not restart. I had no control of the left engine. Yet I still do not have a single caution or warning light. We were definitely now a glider.
I asked ATC to arrange for fire/rescue in case I messed up my approach/landing. Page Airfield is an uncontrolled airport at 4,300 feet elevation, and the runway is just under 6,000 feet long. Unlike the several times we had flown over this incredibly beautiful terrain around Lake Powell and the Grand Canyon, there was now an overcast at 11,000 feet with light rain. I turned on the fuel dumps as we were well above maximum landing weight. Unfortunately, we were not able to dump all the excess fuel because of our nose down attitude.
We broke through the overcast with the rain, and the field was clearly in sight at my 10 o’clock position 7,000 feet below us. The geometry looked a lot like an emergency that I give glider students where I fully deploy the spoilers and tell them to deal with “the emergency.” Remember the Lear 12:1 glide ratio? A modern glider with fully deployed spoilers has no greater than 7:1 glide ratio. Seeing my position visually, I was now totally confident I could make the runway. I just had to manage my energy (speed and altitude) properly.
I continued a spiral from a very high downwind position to set up for a normal pattern and landing. My copilot suggested we go directly over the airport and do a tight circle there. I explained that I was flying a “cone” pattern that would make the approach path easy to manage and continued with that plan. Rolling out on final, I was still high and fast, exactly as I wanted. You can always get rid of energy, but you cannot create it in a glider. And we were a glider.
My sight picture was what I wanted. My copilot was making the appropriate calls on the unicom frequency and warning any aircraft in the pattern to get clear (fortunately there were none). I had the nose pointed at the end of the runway and just had to use flaps and gear at the appropriate times to slow to a “normal” landing speed.
About 2.5 miles from the end of the runway, I called for gear. I was 20 knots above gear speed, but I knew the gear could handle it. Worst case would be very minor gear door damage, but that was unlikely. The gear is locked down, and I am still 30 knots over landing speed as well as overweight, but I have the runway made. I progressively call for flaps, ensuring with each flap change I can still make the runway. We are on short final, about to cross the field threshold, and I am 25 knots above my targeted landing speed (VREF). I saved the final flap position for this scenario.
Full flaps are mostly about drag, not lift. I call for full flaps (5 knots above maximum full-flap speed), knowing they will rapidly decelerate the airplane, especially as I flare for landing. I touched down a little long, on speed, 700 pounds over max landing weight, and brake to stop about 700 feet from the end of the runway.
We sat on the runway doing nothing for a couple of minutes, waiting for our heart rates and blood pressure to go down. We had successfully landed with no damage and no injuries. The FBO then called us on the radio and asked if we were OK. I told them yes, but that we had no engines and needed a tow off the runway.
Unfortunately, ATC was not able to contact anyone in Page to get fire/rescue to the airport. About 10 minutes after we landed, two police SUVs showed up to see if we needed help. The officer literally asked for my license and registration, like it was a traffic stop. No problem. I had the insurance paperwork too.
So, what caused a highly reliable twin engine jet to turn into a glider? The short answer is fuel contamination. The Lear 35 requires jet fuel with an icing inhibitor. That is either premixed in the fuel or mixed in as the fuel is pumped from the truck to the aircraft, which is more common.
Human error was the culprit. Postflight testing of the aircraft fuel and the fuel truck revealed that diesel exhaust fluid (DEF) was present in the fuel and that the icing inhibitor level was significantly below the minimum. DEF had been accidentally put into the icing inhibitor tank instead of the icing inhibitor. DEF is used to clean up diesel exhaust and is injected after the combustion cycle. Unfortunately, DEF in jet fuel forms solid particles that ultimately plugged the fuel nozzles, leading to the engine flameouts.
This column first appeared in the June Ultimate Issue 959 of the FLYING print edition.
