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Friday, 22 March 2019

Boeing 737 Max - Safety Costs Extra

The Cockpit Voice Recorder from Indonesian Lion Air flight 610, which crashed soon after taking off from Jakarta Airport with the loss of all 189 on board, has now been analysed. It shows that the commander and co-pilot were reduced to examining the flight manual for the Boeing 737 Max 8 aircraft, in order to figure out why the plane’s nose was pitching downwards, despite their efforts to keep it straight and level.
What had happened was that one of the two sensors that feed information to the Manoeuvring Characteristics Augmentation System, or MCAS, was feeding it erroneous information, and that bad information was causing MCAS to believe the plane was pitching nose-up to a dangerous enough angle as to induce a stall. So it pitched the nose down. Those on the flight deck would have been better informed if they had known this.

And they would have been better informed if their aircraft had been fitted with what is called a “disagree indicator”, which lights up when the sensors disagree with one another. From there, the pilots would have been able to deduce that they had what is termed a “runaway trim problem”, which has a straightforward solution.

As one former pilot has told an online forum, “It is very quick and easy to arrest a runaway trim condition on the Boeing 737 MAX 8: switch the two guarded stabilizer cutout switches to the off position. These two switches are located immediately next to each other behind the #2 fuel cutoff switch and the flap handle … The pilots could have disabled the stabilizer trim to end the emergency”. But how would they have known about the condition?

Boeing claims that this procedure is documented under runaway trim”. Only there was clearly not enough time for the pilots to locate that part of the flight manual. As another contributor to that forum, a former avionics engineer, added: “Of course, before you do that, you have to be certain where the problem lies”. Which is where the light comes in.

So why didn’t the Lion Air plane have a “disagree indicator” in the cockpit? Simples. Because it was in the list of optional extras, for which Boeing charge, well, extra. Many low cost carriers - like Lion Air - operate on tight margins and therefore don’t choose any of those optional extras. After all, safety shouldn’t mean paying more. Or should it?

This from the Guardian: “Boeing reportedly sold the 737 Max planes that crashed in Indonesia and Ethiopia without two safety features that the US aircraft manufacturer offers airlines for an additional cost … The two safety features in question were an ‘angle of attack indicator’ and an ‘angle of attack disagree light’, both of which were not included in the aircraft by Boeing as standard safety features, according to … the New York Times”.

There was more. “Reports on Thursday night suggested that Boeing will make at lelast one of the safety features - an indicator light - standard on the 737 Max 8 aircraft, according to unnamed officials cited by Associated Press”. The “disagree indicator”. As aviation analyst Bjorn Fehrm has told, “They’re critical, and cost almost nothing for the airlines to install … Boeing charges for them because it can. But they’re vital for safety”.

That’s coming on top of Boeing marking its own homework on certifying the 737 Max as good to fly. The pilots of Lion Air Flight 610 could have been given the vital clue as to what was causing their problem. But for Boeing, until now, safety costs extra.
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Anonymous said...

Good ol' Yank capitalism.

What's good for Boeing corporation profits is good for......er......er......er......

Thierry Bourdelin said...


on a separate issue : did you change anything to the code of your blog ?
since today, everytime I log in, I get my Kaspersky anti-virus ringing all bells about the threat of data loss - not once or twice, but by the tens of alerts

Tim Fenton said...


No changes have been made from this end.

Thierry Bourdelin said...

thx for the reply
I can confirm that your site has been tagged as "tracking data" by my browser (firefox)
first time I see that with your blog

anyway, keep up the good work
best wishes