Hi everyone,
I have had tough discussions concerning the definition of primary flight controls, which triggers (at least in our company) if you have to do a Maintenance Check Flight after disturbance of the system.
The best definition I could find so far is (NATO / Introduction to Flight Test Engineering, July 2005):
The flying controls of an aircraft can be regarded as being comprised of two sub-systems, namely the:
Primary flight control system (PFCS) which enables the attitude and angular rate about each axis to be controlled, and consists of the elevator, ailerons, and rudder (or their equivalents, such as the elevons on a delta aircraft, or the foreplanes with a canard configuration)
Secondary flight control system (SFCS), which permits the aerodynamic configuration to be optimised for particular flight conditions, and consists of such features as variable wing sweep (to cover the Mach number range), flaps and slats (to enhance lift and thereby improve manoeuvre capability and/or reduce takeoff and landing speeds), and airbrakes (to increase deceleration or rate of descent).
Now, we have two issues here:
1)
My colleague argues that the spoilers play a role in roll control of "modern" aircraft (A320, B747), so they should be considered PFCs.
I disagree on this as they "only" assist in roll control (B747s only beyond 45 degrees steering wheel input, if I remember correctly).
And as a gut feeling: Even simultaneous removal/installation of all A320 spoiler SCUs in my point of view does not warrant a MCF; the jobs are fairly simple, and you can test the correct installation on ground (and find spoilers left in the maintenance mode...
).
What do you think - spoilers are primary or secondary flight control surfaces?
2)
In my company, removal/installation of the Trimable Horizontal Stabilizer Actuator triggers a MCF.
Per above definition, the THSA is not a PFC, thus there would be no MCF required. But we DO conduct MCFs after THSA replacements.
(For info on A340s in our outfit: One elevator replacement - no MCF. Both elevators replaced at the same time - MCF).
Any ideas on MCF after THSA replacement?
Have a nice sunday!
J.V.