This discussion is to promote safety and not to establish liability.
CAA’s report contains padding and repetition, so in the interest of clarity, I have paraphrased extensively.
Aircraft Registration ZU-FVW
Owner/Operator: Madiba Bay School of Flight.
Date of Accident 12 August 2014
Time of Accident 0955Z
Type of Aircraft Sling 2 Aeroplane
Type of Operation Private
PIC License Private
Age and nationality 28 Angolan
License Valid Yes
Type Private pilot license
PIC hrs on Type 124.3
Total hrs 168.3
Point of departure Port Elizabeth (FAPE)
Intended landing Tedderfield (FATA)
Accident Location Farm (S32°50.45.0ʹ E025°48.25.0ʹ)
Elevation 1782’ AMSL
Met CAVOK
People on board 1+1
People injured 0
People killed 0
History of Flight:
The pilot and passenger took off from Port Elizabeth on an hour-building, VMC, private flight to Tedderfield just South of Johannesburg.
The pilot went through the aircraft’s technical documentation and then performed a thorough preflight inspection.
After approximately one and half hour’s flying at FL 095 at 90 knots IAS, smoke emanated from the instrument panel and degraded the visibility within the cockpit area to the extent that the instruments could not be scanned. The pilot alerted Cape Town ATC. However the aircraft radio became inoperative during the conversation.
There was an electrical burning smell.
After few minutes all electrical equipment became inoperative. The pilot tried to switch on the back-up EFIS screen, but without success. The smoke in the cockpit intensified.
The pilot descended to FL 075. During the descent the engine stopped and the smoke began to clear. The pilot then followed the procedures in the quick reference handbook (QRH). He switched on the engine control unit (ECU) backup switch and tried to restart the engine but without success.
The pilot then carried out an unsuccessful forced landing.
The landing gear, wings, propeller and the lower cowling were damaged.
This aircraft is powered by a 100 HP Rotax engine turning a 3-bladed Warp drive propeller.
The aircraft has a full-colour EFIS which integrates primary flight data and engine condition monitoring. This revealed that, immediately prior to the accident the sensors on the engine all failed three times to default values caused by three voltage drops. Low voltage warning lights appeared during the three engine failures. The aircraft engine was restarted 3 times.
Where the voltage falls below 10 volts the ECU shuts down to re-synchronize lanes A and B. The first engine shut down was at 1,659 hr 2 minutes. The voltage dropped below 10 volts and the engine RPM dropped to 802. The engine was restarted and it ran until the final engine shut down.
The second ECU voltage drop took place at 1,659 hr 8 minutes, at which time the voltage had dropped to 5.52 volts and the engine was running at 4411 RPM. Although the engine did not cut entirely on this occasion, the warning lights flashed.
The third and final time was when the engine cut out and could not be restarted at 1660 hr 11 minutes, at which time all engine sensors failed.
The cause of the engine failures was the loss of voltage to the ECU. Regulator B on the fuse box had completely melted. This indicates overvoltage leading to total electrical failure.
An engineer removed the ignition housing from the engine to inspect the stator for damage. Signs of burning on the stator were observed on the coils.
The investigation concluded that the burning on the stator coils resulted in melting of the insulation around the copper wires, leading to short circuiting and a persistent overvoltage condition. This led to the failure of the regulator, causing a total electrical failure and subsequent engine stoppage. Further inspection of the stator pickups showed that they had rubbed against the flywheel housing. This caused a heat build-up which resulted in the melting of the stator coils.
Sling 2 aircraft electrical description and warnings:
This aircraft’s electrical system consists of a 12 Volt DC circuit. An 18 Ah lead acid battery provides the energy to start the engine and acts as an emergency standby supply of electrical power for electrical components in case of generator malfunction. The MGL Voyager has a 3 Ah back-up battery which charges from the Voyager backup battery connection terminals.
A single-phase generator connected to a regulator/rectifier supplies DC power to the bus bar and recharges the battery. The positive end of the rectifier is connected to the primary bus through a 50 Amp circuit fuse mounted on the firewall. A red warning light will indicate that the generator is not operating. Circuit protection is through resettable breakers or fuses located on the lower right side of the instrument panel.
POH EMERGENCY PROCEDURES
In-flight Engine Fire
Heating close
Fuel selector close
Throttle full power
Magnetos Off when engine stops
Find landing place
Forced landing perform
NOTE Approx time for engine to use fuel in carbs 30 seconds
WARNING – do not attempt to restart the engine.
In-flight Cockpit Fire
Master switch OFF
Heating Close
Fire extinguisher Use
Once a fire is established land as soon as possible.
Jim’s comments
My goodness I can’t believe the crew survived such a farrago of stuff-ups. The POH has nothing to say about an electrical fire which is both in the engine bay and the cockpit. And the pilot’s lack of training left him doing more harm than good.
I have a decent understanding of machinery but the electrical system on this aircraft leaves my mind floundering much as a gecko might flounder in a bowl of cold vegetable soup.
Herr Rotax departed from traditional aircraft ignition systems when he decided that his engines didn’t need independent magnetos but would manage far better on a diet of two or more batteries charged by things he variously calls generators, dynamos, magnetos and alternators. These power everything from the spark plugs to the EFIS to the beacon to the avionics to the flaps and even the trim. Oh, and the autopilot and the fuel pump. And there are two lanes – A and B, and two busses separated by a circuit breaker; one is the main bus and the other is naturally the instrument bus.
This level of complexity is beyond the grasp of average pilots. Most of us will never come to grips with the basics let alone be able to trouble shoot.
If things go wrong with a traditional system, and the cockpit fills with electrical smoke, it doesn’t matter if your brain turns to porridge, all you have to do is put the master switch off and you know that the engine will keep running.
And if a magneto packs up in flight you probably won’t notice it. The engine may lose a hundred revs. It’s all very simple.
When a Rotax/Sling electrical system catches fire and brain porridge sets in, there’s no quick way of knowing what to do. Your best course is to treat it like any other aircraft – stop feeding the fire with electricity and fuel by shutting down both systems. Land smartly and run away.
The Sling/Rotax POH has no clear answers.
This poor pilot had no idea how to handle the situation. In the nine or ten minutes he had between smoke entering the cockpit and the final engine stoppage, his main focus was on a radio call and restarting the engine.
His very first action was to have a discussion with an oke in Cape Town whose bum was not on fire and who had no way of improving the lot of one who was thus afflicted.
What happened to aviate, navigate, communicate?
During that ten minute period of faffing with the least important priorities, he could have been safely on the ground instead of being in a burning aircraft at flight level 75.
Certainly it turned out okay in the end, but this was despite his actions, rather than because of them.
Take home stuff
Unfortunately I don’t have the space here to discuss the various types of fire. All I can do is to give you the priorities that apply to most light aircraft.
- Breathe. Ventilate the cockpit. You must be able to breathe and see. If the fire is in the engine bay close heaters and demisters. This will stop smoke coming through the firewall. Ventilate the cabin by whatever means possible.
- Descend. Plan on landing quickly before the fire takes hold. Throttle fully back. If you have manual flaps use them. Think before using electric flaps – you may not be able to retract them to stretch your glide later. Trim – it may be your last chance.
- Fuel. Stop feeding the fire. Switch off the fuel and the master. If it’s an oil fire – identified by black smoke – try to stop the prop from turning by using full flap and reducing speed.
- Plan your descent towards the best available area.
- Mayday, If you have time, make a MAYDAY call so that SAR know where to look for you. If it’s an electrical fire the risk of putting on the master switch to make this call is probably not worth it.
- Trouble shoot.