Originally Posted by
Flt.Lt Zed
Why does Boeing not delete MCAS from their new B73 8/9s?. They have thousands flying around successfully without it.
Originally Posted by
AerocatS2A
They needed z for certification.
Originally Posted by
meleagertoo
Might a more comprehensive answer be that they needed it for certification without additional sim conversion training?
Is there any suggestion that an aircraft with those stall characteristics could not be certified at all? Doubtless someone here can advise.
It is not the stall charectoristics. The B737 MAX has pitch up tendencies which don’t meet FAA Static Longitudinal Stability certification standards. To meet the standard, MCAS was needed to reduce the pitch up tendency at high angles of attack.
Addtional sim training won’t exempt you from meeting the certification standard.
Sec. 25.173 Static longitudinal stability.
Under the conditions specified in Sec. 25.175, the characteristics of the elevator control forces (including friction) and the elevator control surface displacement must be as follows:
(a) A pull must be required to obtain and maintain speeds below the specified trim speed, and a push must be required to obtain and maintain speeds above the specified trim speed. In addition, if the elevator control forces are not dependent upon the hinge moments of the elevator control surface, it must also be shown that upward displacement of the elevator trailing edge is required to obtain and maintain speeds below the specified trim speed, and a downward displacement of the elevator trailing edge is required to obtain and maintain speeds above the specified trim speed. This must be shown at any speed that can be obtained except speeds higher than the landing gear or wing flap operating limit speeds or VFC / MFC , whichever is appropriate, or lower than the minimum speed for steady, unstalled flight.
(b) The airspeed must return to within 10 percent of the original trim speed when the control force is slowly released from any speed within the range specified in paragraph (a) of this section.
(c) The stable slope of the stick force versus speed curve may not be less than 0.5 pound for each three knots or exceed a value beyond which control of the airplane is difficult.