MrL RTFQ??? Why nose up trim? Please read some of the possible reasons posted previously.
CrossBars your comment “the airplane should be in trim which it clearly isn't below 400 feet RA”, is an often quoted misunderstanding; see:
JAR–OPS 1.435 Terminology.
“Fail-Passive flight control system. A flight control system is fail-passive if, in the event of a failure, there is no significant out-of-trim condition or deviation of flight path or attitude but the landing is not completed automatically. For a fail-passive automatic flight control system the pilot assumes control of the aeroplane after a failure.”
Also see: JAR-AWO 109 Out-of-trim forces at disengagement
“It must be possible to disengage the automatic landing system at any time without the pilot being faced with out-of-trim forces that might lead to an unacceptable flight path disturbance.”
Therefore, it may be assumed that Boeing has demonstrated that the out of trim forces in the 737 are acceptable.
Re MrL your comment “What is your opinion???? If the AP disengages just after the decision to land, what would you do?? The thinking here is that runway contact is almost certain if a GA is executed. The result we are after is an A/C safely on the deck.”
There is another widely held misconception relating to completing a manual landing after an autopilot failure, see:
“IEM to Appendix 1 to JAR-OPS 1.430, paragraph (e)(5)
Crew actions in case of autopilot failure at or below decision height in fail-passive Category III operations.
For operations to actual RVR values less than 300m, a go-around is assumed in the event of an autopilot failure at or below DH. This means that a go-around is the normal action. However the wording recognises that there may be circumstances where the safest action is to continue the landing. Such circumstances include the height at which the failure occurs, the actual visual references, and other malfunctions. This would typically apply to the late stages of the flare. In conclusion it is not forbidden to continue the approach and complete the landing when the commander or the pilot to whom the conduct of the flight has been delegated, determines that this is the safest course of action. Operational instructions should reflect the information given in this IEM and the operators policy.”
Thus, I would interpret the above as a GA should always be flown, unless unsafe to do so. Any alternative interpretation, without obvious problems e.g. engine failure, generator trip, etc, would require an understanding of why a continued manual landing is safer than a GA. I would further suggest that crews do not have the expertise to judge why a manual landing would be safer in limiting visibility conditions. N.B touching the runway during a GA is not inherently unsafe, whereas landing on grass is.
Could someone give an operators interpretation of this (ops policy) as suggested by the IEM?