It happened four days ago…
The veteran Saab was behaving splendid that day, I like to fly this airplane because it is one of the two company models with extended wingtips – longer wings – so, it climbs better and flies faster than other versions we operate. This was an unusual flight, a mid-morning ferry flight from Bangkok to Chiang Mai with a reduced crew of only two pilots on board, our Flight Attendant was supposed to join us at our first stopover, here we had a full load of passengers to Udon Thani and back again to Chiang Mai, our return to Bangkok was a dead head one on a Company flight at the end of the afternoon.
Forty five minutes into the flight we were cruising at FL240, although our destination was with IMC with isolated rain showers, weather here was excellent. Everything was normal and we were engaged in a technical conversation about Company procedures with my junior First Officer, although he was still in line training he had plenty Thailand flying and turboprop experience.
Then the Master Caution Light came on. As the airplane gets old is usual to have Master Cautions alerts, most of them are nuisances alerts – a Crying Wolf – as is called in aviation. Then, before cancelling the light and the chime, my eyes went to the Master Caution / Warnings Panel to find out what triggered the alert and the position of it on the overhead panel. This was new, not something we see often, a “L BLD AIR LEAK” – an instant image on my mind and I found that the meaning of that light was that we had a hot air leak somewhere between the left engine nacelle and the fuselage. Something to worry about, considering that the hot air is close to 400 degrees on that tubing and that high explosive aviation fuel is on the wing. My First Officer was already with the Abnormal Checklist opened in the correct page. We followed the procedures, reset the position of High and Low Pressure Bleed Valves, but the light kept ON. At the end of the Abnormal Checklist for this item a legend stated: “if any of the above lights still ON – Consider to shutdown the engine. Apply Engine Shutdown Procedure – Page A45”.
Then the dilemma of every professional pilot begun. Was this another false alarm? We were really losing hot compressed air on the rear of the wing? Engine indications were normal. But the Checklist was clear – Engine Shutdown is recommended – All of us heard about sad histories of guys that lost a wing because virtually melted due to a hot air leak or worse case scenario, an explosion. I said – let’s go to Page A45.
We again followed the procedures for Engine Shutdown step by step. I grabbed the Condition Lever and bring it to start position and after a couple of seconds to FUEL OFF.
Now we were a single engine airplane, the sound was different, more quiet. Well, we can’t stay here wondering now, let’s go to plan B, we can’t remain at FL240, we have to descent. Drift down was not a problem here because the aircraft was empty and terrain was not a factor in this area. Next step – notify ATC we had a precautionary engine shutdown and that we are in normal single engine operation. All checklists done, let’s plan the descent, approach and landing. Sometime ago someone taught me; never descent into an airport if you don’t follow these steps:
A – ATIS – Get the Terminal Weather Broadcast or METAR
B – BUGS – Verify the Landing Weight and set the Speed Bugs
B – BRIEFING – Brief the Approach Plate
C – Request the Before Descent Checklist
We began a shallow descent into Chiang Mai, our nearest suitable airport. Weather at destination was with isolated rain showers and good visibility. Established on the ILS we executed an identical approach as if we had two engines. Landing was uneventful. We taxied to the ramp and shutdown the right engine. A while later, our engineer discovered that a loss clamp was the cause of the Bleed Air Leak.
In silence, I walked away from the airplane feeling the self satisfaction of taking the right decision…
“if we professional pilots share our experiences, we are making a safer aviation”