In case you missed it, back in the first week in April an Airbus A-320 took off from New Orleans and then climbing through 4000′ the crew got a message on the Electronic Centralized Aircraft Monitor (ECAM) concerning an Autothrottle system problem and then another saying that there was smoke detected in the Avionics Bay.

All sorts of things happened after that, ending in a landing back at the New Orleans airport with the nosewheel exiting the runway surface and the crew and passengers evacuating the aircraft using the emergency slides. No injuries were reported from anyone on board the flight, though I imagine New Orleans had a shortage of clean seat cushions the the rest of the day.

As more information came to light (The NTSB Preliminary Report is located here in pdf format) things started sounding a little ‘unusual’ to me. The report says that the crew lost primary instrumentation and on landing did not have anti-skid braking nor nosewheel steering. An Avweb article about the incident adds that it was the First Officers displays that went blank and also adds that the air-driven emergency generator deployed – that would refer to the RAT or Ram Air Turbine.

An interesting comment from the crew in both the Preliminary Report and the Avweb article is that neither member of the cockpit crew smelled or saw smoke during the incident – nor did any of the cabin crew.

First, let me say that I was not in the airplane, nor do I know the pilots, nor do I have any first-hand knowledge of what happened onboard the flight that day. All I have is what is published in the NTSB report , the Avweb article and my experience flying as an A-320 captain.

Second, let me reiterate that in-flight fires are nothing to mess with. All of our checklists say that if a fire is confirmed and cannot be immediately extinguished, you are to descend and divert immediately.

The A-320 Avionics Smoke detection system has an ionization detector (like you have in your house)  in an air circulation vent line. If the detector senses particles that it thinks are smoke it sets off the warning and generates the Avionics Smoke ECAM message.  There is no check for flames or heat associated with the detector.

Our procedures were to accomplish the checklist that appears on the ECAM screen and then go to the written Cockpit Operating Manual(COM) and see if further steps are required and to see what changes to our procedures will be necessary because of the steps we had taken.

As best as I can tell from the manuals that I have , the ECAM checklist on our aircraft started with “IF PERCEPTIBLE SMOKE…”

Our  COM checklist for Avionics Smoke started with :

If smoke is not perceived (sight or smell):
– Continue to search for signs of Avionics Smoke.
– End.

If smoke is perceived (sight or smell):
…

If you continue with the Avionics Smoke checklist you are to put on your oxygen masks and start a divert to the nearest suitable airport – then start trying to isolate whatever equipment is causing the problem. If you can identify the specific equipment you are to remove power from it. If the smoke is no longer perceptible after 5 minutes the procedure ends.

If the smoke is still perceptible after 5 minutes it is assumed that you have a real fire in the avionics bay (right below the cockpit) and the procedure gets really serious. You shut off the number one  generator (of two) and turn on the Emergency Electrical Power (extend the RAT).  Once you confirm that the emergency generator is operating you disable the APU (Auxiliary Power Unit) generator and turn off the number 2 generator – that leaves the RAT powering the aircraft electrical system. This emergency generator has a much smaller output than either the aircraft or APU – consequently several normally operating aircraft systems are disabled in order to make sure that essential equipment remains operational.

The result is that the First Officer loses all of his displays and all of the number 2 radios cease operation. The aircraft reverts to what is called Alternate Law, meaning that some of the computer-generated aerodynamic protections are lost. When the landing gear is extended this degrades even farther to Direct Law – you then have a manually-controlled airplane instead of a computer-controlled airplane. You also lose both autopilot systems, the autothrust system, one engine reverser, nosewheel steering and the antiskid function of the braking system.

As a recap, you have a hand-flown, single-pilot airplane. The First Officer has no displays nor access to any radios. With one thrust reverser inoperative and no antiskid system, there is a reduced ability to slow the aircraft on landing and once the rudder loses effectiveness only differential braking can steer the airplane. If the nosewheel is not centered the airplane will go wherever it is pointed as there is no nosewheel steering system.

So, what happened on this flight? I don’t know for sure, but according to the Avweb article, the NTSB is saying that there is no indication of any fire or smoke damage.

Anyway, I thought I’d throw this information out there and let you draw your own conclusions. Some day – maybe in 2-3 years – we’ll get the NTSB final report and see what they think happened.