Smoke or a burning smell in the cockpit

The Thielert/Austro diesel ECUs are equipped with backup batteries that allow them to continue to run even if the main bus is out. Turning off the engine master will kill the engine.

I’ve had smoke in the airplane once, in a 15 yo C172P. I had been asked to do 360s on downwind due to an IFR arrival. The smoke seemed to be coming from behind the panel, where the landing/taxi light switches are located, so I just turned off the landing light and the smoke stopped. I also requested immediate landing due to smoke in the cockpit and was immediately cleared as requested. A fire engine met me on the taxiway. End of story.

In my case the source of the smoke was pretty obvious. That may however not always be the case, and more drastic measures than what I applied may be required.

Peter wrote:

Assume the fire must be electrical → make a quick radio call → turn off the master power? That’s possible on magneto-engine aircraft only

It works on a King Air too. I know from personal experience.

We had lots of acrid smoke in the cruise, called Mayday and emergency diversion.

Last year I did smell and then see smoke coming out of the KX155. I switched the radio off and all other avionics worked well. To be really sure the radio was the culprit, I switched it on again after some thirty minutes and the smoke came back immediately. For this reason we have to carry two radios. It`s another story not to see where the smoke is coming from.

Peter wrote:

What is the best procedure?

Depends on how it happened. If it starts smoking when you turn on something then turn that thing off immediately and never touch the switch again. I had that once with the windshield heater in a C421. As if a frosted over windshield is not enough, filling the cockpit with smoke will certainly not improve forward vision on landing…

Otherwise the best thing is what you propose: Turn off all electrics – or as by memory items of the appropriate checklist. Ours says “Amperage – note” before switching from “BATT” to “EMER” and then “Amperage – verify decrease”. If the short circuit can not be isolated by switching off the electrics (e.g. because of a stuck relay) then the aircraft needs to be on the ground ASAP. Anywhere. Burning up in the air is not survivable.

Edit: The memory items of the smoke checklist start with “Oxygen mask – don”. Always a good idea if one has such a thing on board. Inhaling acrid and poisonous smoke will incapacitate you within seconds. In unpressurised aircraft, opening a window and/or door must be the first action.

Smoke and fire is the deadliest thing you can encounter in flight, particularly in airplanes with complex systems where the origin can not be identified by switching simply consumers off, as they are all interlaced. I lost some people I knew to one of the most notorious smoke accidents in history and they fell into a trap which was almost impossible to avoid.

They flew a large jet out of JFK and had just about reached top of climb when they noticed a faint smoke appearing on the flight deck. It was so faint they initially were not sure whether there was smoke or not, so they asked a flight attendant who confirmed she saw it too. They decided to divert to sort it out.
Shortly after that decision the smoke disappeared. They kept to the decision they had taken but went from almost emergency to irregularity mode and decided to first dump fuel and get the cabin sorted for landing.
Having made all those decisions, they started to work the checklists of smoke of unknown origin. That one calls for the cabin bus and all unnecessary consumers being switched off.
A few minutes later the flight deck was fully ablaze with fire and they lost almost all electrics. In the end they lost control of the airplane and crashed with the loss of 229 lives.

The reason that scenario went out of control was beyond anyone’s imagination. That airplane type was from the outset designed as both a passenger plane and freighter. Consequently, some installations were present which could help a later conversion. One of those was an airconditioning duct which was not used in the passenger version of the plane but only in the cargo version. It was closed off with a silicon cap.

When the fire developed in the electrics panel behind the cockpit wall, the heat which at this point was not noticable inside either flight deck nor cabin melted the silicon cap. Consequently the tube became open and sucked the smoke away into the recirculation fans. Switching off the cabin bus deactivated the fans, so the fire, which had become larger due to the suction, immediately attacked everything in the vicinity, destroying the electrical system including flight instruments, autopilot, fire warnings (they got a fake one on engine 2 which was shut down without need) and so on, until they were overcome and lost the airplane.

The one bit which needs to be priority with any sort of smoke and fire is to get the thing on the ground NOW, right now. Boeing wrote in one of the bulletins which resulted of the above accident that if you had an uncontrolled fire on board, you are either on the ground within 15 minutes or “the accident is a fact”.

One guy who got vindicated by this was the captain of a cargo DC10 who had just done that, got it on the ground NOW without bothering with any checklist which would slow the process. They survived but the airplane burnt out. The original NTSB finding was that had they followed the checklist, the airplane might have been saved. After the above example happened about a year later, those voices went very silent indeed.

In the mean time, we’ve seen two more losses attributed to uncontrolled fire: A 747-400F at Dubai and another one south of Sri Lanka.

One of my “heroes” of aviation, the late David Gunson, said in his wonderful program “What goes up must come down” that he “had an agreement with the fire brigades: If they kept the fire on the ground they would come and put it out.” Not much to add to that I reckon.

So yea, in our small planes, by all means try to identify the souce and isolate it if you can but then get the HELL on the ground. I know at least two people who did not and both are no longer with us in small planes.

So what if you were over open water, 30 mins from the nearest land? So your option is continue and try and manage the smoke, or ditch?

Probably the best option is to make a mayday call, and get down to 50 feet above the surface and continue. That means if you decide to ditch, you can execute it very quickly, which means you can run longer with the fire problem.

dublinpilot wrote:

Probably the best option is to make a mayday call, and get down to 50 feet above the surface and continue. That means if you decide to ditch, you can execute it very quickly, which means you can run longer with the fire problem.

I guess that’s what I would do in the circumstances.

I only had burning smell / smoke once, and that was a radio dying. It decided to do so right above LAX….. probably one of the better places for an emergency to happen, still disconcerting though. It started with the r/t audio quality deteriorating, then came the smell. At first I thought it came from the outside, as I was just over a huge refinery, then a faint smoke appeared. Switched that radio off and informed Santa Monica (my destination a few miles away), that I might have to go NORDO. In the event, switching this one piece of equipment did the trick and the – short – rest of the flight was uneventful.

Peter wrote:

What happened?

In the cruise over North Devon, FL180 or thereabouts, just 2 of us on the aircraft having dropped off my parents at Newquay. Good weather above a broken cloudbase with good vis beneath
A slightly woody smell appeared, and my colleague in the right seat, who is much more experienced than I, went down the back to see if it was a fault with the Mapco (electric hot water container). It wasn’t, but looking down the aircraft from the back a wispy flow of smoke was coming up from my foot well area.

We decided a diversion to Cardiff was in order and called a Mayday, and requested a diversion. A decent towards Cardiff was started and we decided that as the smoke was clearly electrical we would switch off the Battery and take both Generators off line. We later switched on the one hot wired radio via the Clearance/Delivery button on the panel.

In the descent we de-pressurised and opened the clear vision panel and the smoke started to diminish.
We landed flapless at Cardiff, and by this time the smoke was almost gone, however despite our protestations they followed procedure and insisted we stopped and evacuated on the runway, which we did, surrounded by fire appliances.

After more than one inspection by a fireman with a thermal imaging camera it was decided the hot area, which was under the pilot’s feet, was cooling, and the fire chief asked if we would taxi the aircraft off the runway. I declined as we would all have looked a bit daft if the thing had caught fire as we switched on the battery and then taken several hundred amps to start the engines!
They couldn’t find a tow truck that would work and so we were pushed off the runway by the combined efforts of all the fire crews.

The fault was later found to be with the cabin air blower. Had we followed the check list to the letter rather than our decision to switch off all electrics the check list called for “cabin air blower – HIGH”, which in this case would have made things worse.

If the weather had been worse we could have been in serious trouble. I seem to remember that the offending blower motor apparently once had a requirement for service every 1000 hrs, but this was discontinued; our aircraft had 1100TT.