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Old 5th December 2010 | 19:58
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safetypee
 
Joined: Dec 2002
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From: UK
IIRC some types of thickened anti-icing fluids (type 4) have caused problems on a few aircraft. This involved types with manual controls, but not necessarily servo-tabbed controls, which independently, suffered problems from re-hydrated fluid residues. Also, the airfoil / control surface sections were of a modern design – reflex surfaces.
ATR and Saab experienced problems with heavy control forces during rotation. Again from memory there was one incident involving an ATR where the crew ‘failed’ to rotate due to heavy controls – either too heavy, or the crew failed to pull hard enough (non normal control feel).
Several manufacturers have conducted tests to check for problems, including loss of lift performance after take off.
Where conditions result in unacceptably high control forces, (adverse cg, wt, configuration) manufacturers should have published appropriate procedures. Again IIRC, these include restrictions on configuration / cg, type of fluid, repositioned takeoff trim setting (to reduce forces – but a/c must still be in trim after takeoff), and / or changes in takeoff speed schedules.

CS 25.143 – maximum control force (short term):-
Control wheel – one hand 220N, 50 lb.
Control wheel – two hands 334N, 75 lb.
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