Thu Mar 21, 2019, 01:37 PM

Doomed Boeing Jets Lacked 2 Safety Features That Company Sold Only as Extras

As the pilots of the doomed Boeing jets in Ethiopia and Indonesia fought to control their planes, they lacked two notable safety features in their cockpits.

One reason: Boeing charged extra for them. For Boeing and other aircraft manufacturers, the practice of charging to upgrade a standard plane can be lucrative. Top airlines around the world must pay handsomely to have the jets they order fitted with customized add-ons.

Many airlines, especially low-cost carriers like Indonesia’s Lion Air, have opted not to buy them — and regulators don’t require them.

Now, in the wake of the two deadly crashes involving the same jet model, Boeing will make one of those safety features standard as part of a fix to get the planes in the air again.

Boeing’s optional safety features, in part, could have helped the pilots detect any erroneous readings. One of the optional upgrades, the angle of attack indicator, displays the readings of the two sensors. The other, called a disagree light, is activated if those sensors are at odds with one another.

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Reply Doomed Boeing Jets Lacked 2 Safety Features That Company Sold Only as Extras (Original post)
Gamle-ged Mar 2019 OP
drunk_teddy Mar 2019 #1
oflguy Mar 2019 #2

Response to Gamle-ged (Original post)

Thu Mar 21, 2019, 08:22 PM

1. hell nawaaa like buying a Buick Riviera w/o the vinyl top n/t

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Response to Gamle-ged (Original post)

Fri Mar 22, 2019, 08:22 AM

2. From the linked article

"When it was rolled out, MCAS took readings from only one sensor on any given flight, leaving the system vulnerable to a single point of failure. One theory in the Lion Air crash is that MCAS was receiving faulty data from one of the sensors, prompting an unrecoverable nose dive.
In the software update that Boeing says is coming soon, MCAS will be modified to take readings from both sensors. If there is a meaningful disagreement between the readings, MCAS will be disabled.
Incorporating the disagree light and the angle of attack indicators on all planes would be a welcome move, safety experts said, and would alert pilots — as well as maintenance staff who service a plane after a problematic flight — to issues with the sensors."

When it comes to an item like an angle of attack sensor, you are dealing with a mechanical "fin" that converts the AOA indication to an electronic signal. The nature of that gadget lends itself to failure, so I can't believe Boeing even considered making a redundant sensor optional. The sensors attach on the nose of the aircraft. A second one mounts on the opposite side of the nose. The cost to Boeing to install the redundant sensor and wiring during the aircraft's manufacture is almost nothing. I have to believe the wiring is installed during manufacture regardless whether the second one is purchased or not, making the add on cost to Boeing almost nothing likewise.

We are talking about an aerodynamic stall here, not something mundane like an extra bathroom. This is a safety issue where the benefit to Boeing and the airline far outweighs the cost. Maybe Boeing just figured everybody would recognize this and purchase the option. Either way, hopefully everybody (Boeing, FAA and Airlines) learned their lesson. The redundant sensor and the disagree light will now be mandatory.

Remember the Malaysian airliner that disappeared? That plane did not have satellite tracking on it because it was (and still is) an option.

We live and learn, especially in aviation. Not long ago, an airliner crashed in the Atlantic because a pitot tube was plugged. The plane crashed when the pilots tried to put the plane on autopilot, which used the left pitot tube to measure airspeed. There are two pitot tubes on the nose, one for each pilot. After that crash, they changed it so both pitot tubes input airspeed to the autopilot and the pilot is notified if they disagree.

Apparently the industry did not learn from that situation.

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