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Old 26th Nov 2020, 22:38
  #35 (permalink)  
john_tullamarine
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There was a video going around

A simple youtube search will come up with a number of similar videos.

(a) just do be careful taking the stories as gospel as Va is subject to a variety of OWTs and the correct story sometimes is quite different. The usual pilot story only applies for aircraft certificated to the minimum value permitted for Va. For some aircraft the OEM may well elect to design for a higher Va and therein lies a problem when the pilot fraternity typically uses an incorrect definition of what Va is about. The design standards talk about

Design maneuvering speed VA. For VA, the following applies:
(1) VAmay not be less than VS where--
(i) VS is a computed stalling speed with flaps retracted at the design weight, normally based on the maximum airplane normal force coefficients, CNA; and
(ii) n is the limit maneuvering load factor used in design.
(2) The value of VA need not exceed the value of VC used in design.

The two important points to note are bolded in the quote. You need to know what the particular certification did before you go off doing this and that. Other bits make it clear that the pilot is responsible for making sure that any manoeuvres do not cause the limit load factor to be exceeded (often referred to as a "checked" manoeuvre). That is to say, for an aircraft designed for Va above the minimum permitted value, the pilot must not rely on protection by stalling to avoid pulling tails and/or wings off ....

(b) if you are going to run factored speed calculations to account for bank angle or steady g loads, please ensure you use CAS rather than IAS for the sums, converting IAS to CAS at the start and CAS to IAS at the finish.

(c) AFM stall speeds are based on very steady conditions (smooth air and the 1kt/sec deceleration bit). Things can get a bit off that mark if you are manoeuvring or running the speed back at a significantly faster rate.

(d) if you are going to put yourself in a stall risk situation, do so with plenty of air underneath the bird so that the hard, rocky bits don't get a look in.
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