58
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Accepted
What is the technique or procedure to disable/disengage the MCAS on Boeing 737 Max 8 & 9 Aircraft?
MCAS doesn't have its own on/off switch
It is a fly-by-wire feature designed to account for a particular flight regime that would not (or was not expected to be) encountered very often in normal ...
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27
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Did A320 NEO need an equivalent to 737 MAX MCAS because of its bigger engines?
The A320 and 737 have very different flight control architectures.
The 737 has physical cables that transmit pilot (or autopilot) input directly to the hydraulic actuators. This was common in the ...
- 73.5k
22
votes
What is the technique or procedure to disable/disengage the MCAS on Boeing 737 Max 8 & 9 Aircraft?
You can disable the stabiliser trim which will prevent MCAS from making inputs to the aircraft.
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15
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Did A320 NEO need an equivalent to 737 MAX MCAS because of its bigger engines?
The 737 Max had short landing gear. Since the engines need to have a minimum ground clearance, this meant that the new larger engines had to be repositioned further forward and higher on the wing.
...
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13
votes
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Why does the KC-46 use two sensors for MCAS when the 737 Max doesn’t?
According to the article, the KC-46 uses the dual FCC/AoA sensor for computing both FCC channels and comparing the command signals. With two disagreeing signals there is no way to determine which one ...
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12
votes
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Why would Boeing's MCAS be preferable to a modified Feel and Centering Unit?
On the 737 NG, at high angles of attack, the nose of the plane would naturally pitch down, helping to recover from a stall and to increase airspeed.
The larger engine nacelles on the 737 MAX are ...
- 73.5k
12
votes
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Could the pilots really not trim manually to overcome MCAS, as shown in the Netflix Downfall documentary?
The problem was they could not manually trim the a/c without performing the Boeing "offload the jack" procedure developed for the 737, which requires altitude to perform because you are ...
- 134k
11
votes
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Can computer imposed inputs be overridden on the Boeing 737-MAX?
The new 737 MAX has a more advanced pitch control system called maneuvering characteristics augmentation system (MCAS), which automatically adjusts the stabilator trim in case of high thrust and high ...
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10
votes
What is the technique or procedure to disable/disengage the MCAS on Boeing 737 Max 8 & 9 Aircraft?
From what I have read, the other answers explain the cutout procedure correctly.
Edit: The ongoing investigation appears to reveal that the aerodynamic forces on the stabilizer may become so high ...
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10
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If the updated MCAS software needs two AOA sensors, doesn't that introduce a new single point of failure?
Noting that the details of the MCAS update are yet to be publicly confirmed by Boeing - no I don't believe you are missing anything.
MCAS was meant to be a system that only kicked in when the pilots ...
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9
votes
Can airlines choose whether or not to enable MCAS on their fleets, and if so, have US airlines chosen to do so?
No, MCAS was required for the 737 MAX to be certified by the FAA. It cannot be deactivated by any airline, including airlines in the U.S.
Source:
"M.C.A.S. was necessary then for the airplane [737 ...
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9
votes
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What programming language(s) is Boeing's MCAS written in?
What language is Boeing's MCAS written in?
I believe the Flight Control Computer is a Collins Aerospace FCC-730 with two 16-bit processors.
Collins are known to use Ada for at least some of their ...
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9
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Would fitting a T-tail on the 737 Max make MCAS unnecessary?
No. A t-tail would worsen the characteristics of the airplane. While not necessarily a horrible idea in its own right, the already-nasty slow-flight/high alpha/stall characteristics of the aircraft ...
- 2,500
9
votes
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Do pilots still not need additional simulator training to fly the 737 MAX?
One of the conditions for allowing the 737 MAX to operate again, was additional simulator training for all pilots. In principle, each aviation authority can make their own rules, but the 4 big western ...
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8
votes
Why does the MCAS use the horizontal stabiliser rather than the elevators?
MCAS uses stabiliser input to retain full elevator authority in both directions for pilot input. MCAS is set up as an Inner Loop autopilot: it controls behaviour around the CoG of the aeroplane ...
- 62.3k
8
votes
Accepted
Why couldn’t Boeing just use the stab trim system to do MCAS job?
No, the 737 NG stabilizer trim system does not feedback from AOA. My source of information comes from this LinkedIn Slide Share and corroborated by this online FCOM.
There are several ways through ...
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8
votes
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what type of sensors does the Boeing 737 MAX use for MCAS?
The pitot tube has nothing to do with the angle of attack. It is used for measuring pressure which in turn gives you the airspeed.
Accelerometers are used for the Inertial Navigation System.
The ...
- 1,501
8
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Has the Boeing 737 MAX MCAS system successfully prevented a stall or approach to stall condition outside testing?
We don't know - until we hear about such a case!
A positive answer would require
a trace of MCAS action
sufficient evidence that the pilot could not have handled the (near) stall without MCAS.
...
- 10.8k
8
votes
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Did Boeing need MCAS because the 737 MAX didn’t meet FAA longitudinal stability requirements, or was it to make the MAX feel like the NG?
The Boeing 737 MAX MCAS system is there ONLY to meet the FAA longitudinal stability requirements as specified in FAR Section 25.173, and in particular part (c) which mandates "stick force vs ...
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7
votes
Boeing Dreamliner MCAS
No, we don’t know for sure. We do know, however, that it wouldn’t make any sense to install it.
It’s a bit like asking „are we sure the electric VW Golf doesn’t run the Diesel cheating software?“ - ...
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6
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Why would Boeing's MCAS be preferable to a modified Feel and Centering Unit?
A change in the pitch feel system wouldn't solve the problem. It's the MAX's natural behaviour separate from the flight control system (that is, behaviour when you aren't touching the controls). As ...
- 134k
6
votes
Will the 737 Max 10 have MCAS?
The fuselage length is immaterial. The problem of the Max series relates to the positions of the engines versus the wing, and their aerodynamic interference near the at high alpha. The amount of ...
- 4,624
6
votes
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On the 737 MAX, can the pilots switch to the backup MCAS, or switch active MCAS input to another AoA probe during flight?
As far as I understand from reading the B737 Operations Manual and the Lion Air Accident Investigation report,
Each Flight Control Computer (FCC) receives AOA input only from the onside ADIRU and ...
- 11.1k
5
votes
Was MCAS part of 737 8 MAX MMEL list?
It does not appear that MCAS was in any of the maintenance documents. This was part of the issue with the Lion Air crash. On the previous flight with the accident aircraft, MCAS acted on the faulty ...
- 73.5k
5
votes
How the stabilizer cutout switch functionality has changed from Boeing 737 NG to 737 MAX?
What do you know, I found the answer to my exact question in the Seattle Times:
First of all, even after two fatal crashes,
Boeing declined to detail the specific functionality of the two switches.
...
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5
votes
What is MCAS' purpose?
This website has a very comprehensive description and analysis of MCAS: http://www.b737.org.uk/mcas.htm
I find it to be the most accurate of all the various sources often quoted.
Here is a small quote ...
- 37.9k
5
votes
Would fitting a T-tail on the 737 Max make MCAS unnecessary?
The problem with the MAX has nothing to do with the elevators being ineffective, the characteristics which lead to the pitching up will be present wherever you put the tail. It's the placement of the ...
- 54.2k
4
votes
Has the Boeing 737 MAX MCAS system successfully prevented a stall or approach to stall condition outside testing?
Most airlines have a Flight Data Analysis section which uses the routine download of the FDR to automatically flag deviations from the normal flight profile for investigation. The kind of maneuvering ...
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4
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Is the Boeing 737 MAX 8 MCAS exceptional in operating when autopilot is off?
All large swept-wing aircraft have a yaw damper, which is always active. It takes an input from a yaw gyro and applies rudder inputs in order to counter Dutch roll.
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