4 ms·
There were actually two AoA sensors (on either side of the aircraft) each connected to different sides of the panel. The issue was/is what to do when they disag
by gbjw 7y ago
There were actually two AoA sensors (on either side of the aircraft) each connected to different sides of the panel. The issue was/is what to do when they disagree (with respect to MCAS).
EDIT: Source: https://aviation.stackexchange.com/questions/61011/how-many-aoa-sensors-does-the-737-max-have https://aviation.stackexchange.com/questions/61011/how-many-...
- AnotherGoodName 7y agoMy next question would be are they adding a third? Everything I hear sounds like a software update rather than the more expensive hardware changes.
- zaxomi 7y agoThere is no need to add a third. The software update make MCAS to use both existing angle of attack sensors, and if they disagree MCAS will be disabled and a warning indication will be shown.
- mantap 7y agoThen you risk a stall. If MCAS is non-essential why not remove it completely? And if it's essential, then you need >2 sensors to ensure it can operate all the time.
- Tomte 7y agoNot everything that is non-critical should be removed. Autopilot? Not necessary, pilots can fly themselves. Still, it is added for convenience (and its consequences, less mental burden, more mental capacity to do other stuff).
- zaxomi 7y agoMCAS is not essential. It exist to make the airplane behave like the older B737.
- mantap 7y agoThis just isn't true. MCAS was added because it is a safety requirement that stick forces strictly increase. You don't want the thing to start stalling itself.
- zaroth 7y agoI think you mean decrease — pulling back should become less effective as you enter a stall.
- Stratoscope 7y agoStick force doesn't refer to how effective any stick movement is. Roughly speaking, stick force is the amount of force the pilot has to to apply to the stick to achieve a given movement of the control surfaces. As the airplane gets closer to a stall, you want to make it harder for the pilot to pull it fully into the stall, by increasing the required stick force. If the stick force decreased as the airplane approached a stall, then the pilot would have to actively push the stick back into more stable flight.
- salawat 7y agoThe MCAS subsystem in the active Flight Control Computer was only taking input from the AoA vane on that FCC's side of the plane, and not cross-checking with the other instrument. The triple redundancy only comes into play with systems with a severity of failure rated as catastrophic. The MCAS system as originally designed was rated as merely hazardous. Which doesn't require redundancy. The decision to feed off of only one vane was intentional to avoid having to have pilots undergo level D simulator training as part of their type certification. Multi-sensor systems generally require Level D training. See the 737 MAX Expose by 60 minutes, where the whistleblower testimony is first presented.
- CydeWeys 7y agoWow, so they could've easily made it safer with the hardware they already had onboard, but chose not to because money? Somewhere inside Boeing there are decision-makers that lack ethics (or even long-term financial thinking). They need to be fired.
- brentm 7y agoUnless they were just acting completely reckless, which is hard to believe considering their previous safety record and the downside of failure, it's probably more complex than that.
- tgsovlerkhgsel 7y agoYes. Specifically, because airlines wanted to save money on pilot training.
- acqq 7y agoRather because Boeing wanted to remain "competitive" against Airbus' superior alternative by selling something that didn't exist, namely the factually different plane which would be certified as "the same". https://leehamnews.com/2019/03/20/boeing-didnt-want-to-re-engine-the-737-but-had-design-standing-by/ https://leehamnews.com/2019/03/20/boeing-didnt-want-to-re-en...
- 7y ago