Engine Problems of AirAsia’s Flight QZ 7633 Were “Downplayed”

The engine failure that was downplayed.
The engine failure that was downplayed.


Whilst the SAR operations for the passengers and crew of QZ8501 are going on, on 4-1-2015 AirAsia flight QZ7633 from Bandung to Surabaya had engine problems.



On 4-1-2015 there was another adverse news about AirAsia’s flight QZ 7633 from Bandung to Surabaya, which was taxiing for two to three minutes preparing for take off and it had to turn back due to engine problems.  Of course, this was downplayed as a small matter by non other than the AirAsia’s supremo, Tan Sri Tony Fernandes. He had lashed out against the media for being “silly” and “sensationalising”,  HERE.


Ms BK Sidhu, the editor of Business Star, should have been seconded to Surabaya to assist by “quoting sources” in her stories as in HEREHERE &  HERE.


In November 2012, the Malaysian  Department of Civil Aviation (DCA) granted AirAsia a 6 months Air Operation Certificate (AOC)  due to its failure to meet safety regulatory standard, HERE.


Below is a well thought out comment and backed up by research from a regular contributor of yours truly’s blog. Yours truly would like to share the comment from IT.Scheiss with other readers.  Than you IT.Scheiss for enlightening us on the subject matter.


Now let us examine this statement by Air Asia

“Indonesia AirAsia flight QZ7633 was taxiing in preparation for takeoff at the Surabaya airport – where last week’s doomed flight also took off – when a power unit used to start the plane shut down, an airline official said.”

An auxiliary power unit (APU) is a small jet engine usually mounted in the aircraft’s tail which powers the electrical generator to keep all electricity powered systems on the aircraft running, whilst the aircraft is on the ground with the main engines turned off. The APU also provides the electrical power for the starter of the main engines to get them running and generating electrical power themselves, after which the APU is no longer required, though sometimes the APU is left running to provide back-up power during the flight.


You can read more about APUs on Wikipedia.


Pratt & Whitney on APUs:

“Auxiliary Power Units (APUs) are gas turbine engines used primarily during aircraft ground operation to provide electricity, compressed air, and/or shaft power for main engine start, air conditioning, electric power and other aircraft systems. APUs can also provide backup electric power during in-flight operation. “. Please read HERE.


The You Tube video about a rather old APU on a Boeing 727 aircraft.


Notice the meticulous step by step procedures required when starting up and shutting down an APU


The more exciting video of the startup of an APU on a Boeing 747.



And on a Boeing 737


Here is a You Tube video of an APU failure on a Delta Airlines plane during push back from the parking bay but before the main engines were started.


Since the APU is a small gas turbine engine powered by the same jet fuel as the main engines, it is potentially dangerous if it catches fire or explodes and since it is usually mounted in the aircraft’s tail, an APU fire could spread and consume tioe rest of the aircraft’s fuselage where the passengers are.


So ask Tony what happened when the APU on that Air Asia flight failed with such a bang and why did it happen?


Why was it necessary for the APU to be kept running, whilst the main engines were running?




2 thoughts on “Engine Problems of AirAsia’s Flight QZ 7633 Were “Downplayed”

  1. IT.Scheiss

    Sdr. Wee,

    Thanks for highlighting my comment on APUs.

    I would like to add a contribution of a UK Air Accidents Investigation Board provided by fellow commentor Warrior 231 with regards an incident involving a failed APU on a Boeing 747 at Heathrow Airport in 2013 which shows that an APU failure is s serious matter and is potentially very dangerous.

    Click to access cms_resources.cfm

    This incident occurred shortly after the APU was started whilst the aicraft was parked and the pilot ordered a passenger evacuation.

    The APU is not always needed once the main engines are started up and running and is usually turned off since the main engines now provide the electrical, pnuematic and other power, though sometimes the APU is kept running for backup power or for supplemental power as Pratt & Whitney described above.

    Think of an APU as an electrical generator set used to keep a factory, facility or office running when the mains supply fails and is then shut down once mains supply is restored.

    In earlier days, there was a generator truck which drove up to the plane and attached a cable to it to keep the onboard electrical and other systems running whilst the main engines were turned off and to provide the power to start up the main engines, after which the generator truck disconects the cable and drives away, ready to service another plane.

    That generator truck is no longer needed today, since more modent aircraft are now fitted with their own on-board auxilliary power source – i.e. the APU.

    So why was the APU on that Indonesia Air Asia plane kept running when the main engines were running and more importantly – what happened to it, that the passengers reportedly heard a bang and the main engines died.


  2. Warrior 231

    For those interested:


    An additional and wholly plausible query about the AA Airbus 320 APU relates to whether its susceptibility to malfunction is accelerated by constant wear and tear or was it just a freak occurrence that should not be “sillily sensationalized”

    This question pops up because the APU in the Boeing that was involved in the Heathrow incident as linked by It above was approximately 22 years old which is way older than virtually all planes currently operating in the AA fleet.

    Secondly, the absence of any pings from the ULB is mystifying. My personal conjecture is that, the BBs could have landed or be embedded in thick mud thus muffling its emissions:


    Additionally, the nature of the impact, i.e Force of impact (Fi = Wa/g =G), the G force (converting the rate of deceleration= G=a/g), Pressure of impact (Pi = Fi/Ai) etc could have plausibly dislodged the power supply.

    It is entirely plausible too that the lithium battery power pack was not serviced due to an inadvertent oversight. Much was made of the latter assumption, albeit without evidence in MH370, to arouse curiosity as to whether a similar oversight had recurred….but as I say all these assumptions are conjectures that require clarification as FDRs do indeed go unrecovered.



    Other possible reasons are indicated in this extract from the Air France 2009 search:

    “The zone where the wreckage was discovered on 3 April 2011 was thus explored by a US Navy TPL, but without detecting the beacons, though such detection had been judged likely, based on experience, and the hypothesis that the wreckage zone would have been covered. The reasons for this lack of detection must now be the subject of research and feedback to evaluate the problems linked to the detection of the pingers. These problems could specifically be linked to a malfunction of the pingers, to problems with submarine acoustic propagation, or with imprecise bathymetry on the marine charts that were available at that time.”

    Click to access discovery.of.the.wreckage.pdf

    In fact, the report concludes with the following recommendation:

    “Despite this, it is noted that there is some doubt as to whether they functioned. The recommendation made by the BEA to install an additional beacon, transmitting on a lower frequency and thus with longer range, should enable the risk of non-detection to be decreased.”

    In raising these queries, I am not in the least interested in taking unwarranted potshots at AA but merely expressing my concern as a regular air traveler as to the safety procedures /protocols adopted by ALL carriers in the region given recent events, major or minor.

    I reckon politico-economic considerations such as role played in enhancing passenger arrivals in certain hubs, influx of tourists, huge financial outlays/debts that are entwined with local/international banks, competition between regional airlines, national and strategic interests etc are all of paramount importance in the overall discourse about aviation in the region but I would think that not one of those considerations should supersede air worthiness, passenger safety, pilot readiness etc irrespective of whichever airline is involved.

    Just my two cents.

    By the way, this just came in 4 hours or so ago :



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