Your Questions. Answered.

1. What is MCAS?

MCAS, or Maneuvering Characteristics Augmentation System, is a flight control law implemented on the 737 MAX to improve aircraft handling characteristics and decrease pitch-up tendency at elevated angles of attack.

2. Why did Boeing install MCAS on the 737 MAX?

The Maneuvering Characteristics Augmentation System (MCAS) flight control law was designed and certified for the 737 MAX to enhance the pitch stability of the airplane – so that it feels and flies like other 737s.

3. When is MCAS activated?

MCAS only activates in the rare instance when three conditions occur:
  • The airplane nose approaches a higher-than-usual angle.
  • The pilot is manually flying up.
  • The airplane flaps are up.

4. What is the Angle of Attack?

Angle of Attack (AOA) is the difference between the pitch angle (nose direction) of the airplane and the angle of the oncoming wind.

5. How will MCAS change with this software update?

Boeing has developed an MCAS software update to provide additional layers of protection if the AOA sensors provide erroneous data. The additional layers of protection include:
  • Flight control system will now compare inputs from both AOA sensors. If the sensors disagree by 5.5 degrees or more with the flaps retracted, MCAS will not activate. An indicator on the flight deck display will alert the pilots.
  • If MCAS is activated in non-normal conditions, it will only provide one input for each elevated AOA event. There are no known or envisioned failure conditions where MCAS will provide multiple inputs.
  • MCAS can never command more stabilizer input than can be counteracted by the flight crew pulling back on the column. The pilots will continue to always have the ability to override MCAS and manually control the airplane.
These updates reduce the crew’s workload in non-normal flight situations and prevents erroneous data from causing MCAS activation.

6. Does Boeing charge for safety features?

All primary flight information required to safely and efficiently operate the 737 MAX is included on the baseline primary flight display. This is true of all our commercial products. Boeing doesn’t put a price on required safety features. Crew procedures and training for safe and efficient operation of the airplane are focused around airplane roll and pitch attitude, altitude, heading and vertical speed, all of which are integrated on the primary flight display. All 737 MAX airplanes display this data in a way that is consistent with pilot training and the fundamental instrument scan pattern that pilots are trained to use. Some operators have their own tailored training requirements and have requested that we also provide AOA information on the Primary Flight Display, and we have offered the optional capability to provide that information. However, not all customers wish to include this feature on their Primary Flight Display, so it is offered as a customer-selected option. With the software update, customers are not charged for the AOA disagree feature or their selection of the AOA indicator option.

7. How many 737 MAX airplanes have been delivered to customers?

Boeing has delivered more than 370 MAXs to 47 customers (through February 2019).

8. How many additional 737 MAX airplanes have been ordered?

About 5,000 737 MAX airplanes have been ordered by 107 customers.

9. How and why did Boeing decide to develop the 737 MAX?

Our development efforts always start with listening to our customers to understand their needs and requirements. Based on customer feedback and market data, the 737 MAX was the clear choice to succeed the Next-Generation 737. Over a six-year period, our team worked through a disciplined methodical development process that culminated with a robust test program that validated the airplane’s safety and performance.

More 737 MAX Resources

Here’s more information about our ongoing efforts in working with manufacturers, regulators, pilots and airlines around the world to improve flying for everyone.