Automation Surprises?

[jmmilner]

I've read NTSB reports on and off for 30+ years and I've always been uncomfortable with the fact that the AP seems to be able to compensate for a decaying situation (like the ATR-42 icing years back) or the drop below Vref in the recent TK accident by trimming the aircraft, seemingly without the pilots' notice. When the AP reaches the limits of authority (can't trim any more so disconnects) or some other condition arises (stick shaker) that demands immediate pilot input, the pilot is presented with a full blown issue without the history that hand-flying to the same point would have provided. Does this lack of history make a difference in the effectiveness of the pilot's response?

[Gooneyone]

This is why most turboprop manufacturers state that the autopilot must be disengaged in severe icing conditions: "the pilot is presented with a full blown issue without the history that hand-flying to the same point would have provided"
Without the "history" you are presented with an unusual situation with little warning.

[FCS Explorer]

you only get surprised when you don't pay attention.
i fly the b738 and speaking to the guys if flown with the last days we just have no idea how the AMS-thing went down with three guys in the cockpit.

[westinghouse]

if you dont know the automation for you particular acft your going to get killed.
when your close to ground for landing it isnt the best place to try and figure out what the AP is doing.:=
and if th acft aint doing what you want it to take over or go around.:ok:

[BOAC]

Three good 'golden rules', WH, but "if you dont know the automation for you particular acft your going to get killed." - better get onto TLS and get a big order for (software driven) coffins:)

[safetypee]

Automatic flight guidance systems have been described like a “dutiful First Officer, but they never learn”.
The certification/design requirements should ensure that in the event of a FGS failure, an automatic or planned disconnect, the aircraft is in a reasonable trimmed condition. After all, a good pilot should never hand over an out of trim aircraft to another pilot – surprising though that pilots think that an FGS will manage an out of trim aircraft at engagement … not always, thus some nasty surprises.
When a pilot is flying and has difficulty – high forces, rapidly changing conditions, he can communicate or shows signs of stress; the FGS cannot. Thus, an FGS can hide a non standard situation – exceptional ice accumulation or pending loss of control (stall) - until the last moment. In these rare events, pilots are often faced with surprising conditions, mainly because they did not see/understand the situation - external, aircraft, and FGS.

Most modern aircraft and FGS’s can cope with icing conditions; they have been tested within the capabilities of the aircraft’s anti/deicing systems. However, in severe icing – defined as being beyond the anti/deicing systems capability, thus aircraft specific – the FGS capability may be unknown. Thus the advice to disengage the autos, which enables the crew to maintain the best understanding of the aircraft’s performance by ‘feeling’ the control performance while they are leaving the severe icing conditions i.e. they should not be there – just like a stalled conditon.
Another point is that FGS's do not have the same force authority over aircraft control as do pilots, thus they tend to rely on trim for dynamic maneuvers. Similarly, FGS’s are not as adaptable as pilots and rarely can see ahead, have little planning capability, and cannot think ‘what if’.
Aircraft / FGS related problems usually occur when the pilot fails to see ahead, doesn’t plan, or think ‘what if’.