[SystemSafety] "FAA chief '100% confident' of 737 MAX safety as flights to resume"

Dewi Daniels dewi.daniels at software-safety.com
Thu Dec 3 13:43:41 CET 2020


That isn't what is meant by a deep stall. A deep stall is one in which the
elevators have no authority, meaning that the pilot is unable to recover
from the stall. Aircraft designs with T-tails can be susceptible to deep
stalls. A deep stall resulted in the loss of the BAC 1-111 prototype on 22
October 1953.


In the case of the Boeing 737 MAX, if the pilot were to inadvertently stall
the aircraft, he would still be able to recover from the stall by pushing
the yoke forward or even by increasing engine thrust.


Dewi Daniels | Director | Software Safety Limited

Telephone +44 7968 837742 | Email d <ddaniels at verocel.com>
ewi.daniels at software-safety.com

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On Thu, 3 Dec 2020 at 12:08, Olwen Morgan <olwen at phaedsys.com> wrote:

> Having admitted to my execrable knowledge of aerodynamics and
> aeronautical engineering, I will now make a few ill-informed
> speculations about the 737 MAX:
> Consider the following situation without MCAS:
> At a certain speed and AoA, the pitch-up tendency of the aircraft is
> beginning and the force on the stick has started to lessen. AFAI can
> see, lessening of stick force will be due to reduced aerodynamic
> pressure on the HS and elevators. If the HS and elevators are exerting a
> much reduced force against the oncoming air-stream, then their ability
> to control pitch has been correspondingly lessened. At the same time,
> the pitch-up tendency is bringing the wing closer to a stall condition.
> If the aircraft progresses to a wing-stall condition and at the same
> time is suffering reduced pitch control as a result of what is
> happening/has happened to the air flow over the HS and elevators, then
> that condition is very close to a much more dangerous *deep stall*
> condition.
> Call me a scaredy-cat - or even just a pig-ignorant old bag - but I
> personally don't think that any civil airliner airframe should exhibit
> aerodynamic behaviour that introduces such a risk of a deep stall.
> And now I'll just let PBL hurl his customary bile at me.
> Olwen
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