Re: hydraulic problems with DC-10's??

From: (Paul Raveling)
Organization: Unify Corporation (Sacramento)
Date:         08 Dec 92 15:51:12 PST
References:   1 2 3 4
Next article
View raw article
  or MIME structure

In article <airliners.1992.92@ohare.Chicago.COM>, (Terrell D. Drinkard) writes:
> In article <airliners.1992.85@ohare.Chicago.COM> weiss@turing.SEAS.UCLA.EDU (Michael Weiss) writes:
> >
> >>Flight AA 191 lost the slats on the left hand
> >>wing (if memory serves) because of Douglas' failure to include mechanical
> >>lockouts on the slat actuators.  They were not required to certify the
> >>airplane.

	I'd be inclined to phrase that a bit differently.  The certification
	requirements were satisfield by demonstrating safe flight with
	asymmetric slats.  The catch is that (a) flying safely in this
	configuration requires keeping airspeed above the minimum (or
	AOA below the maximum) needed with slats retracted and (b) the
	crew didn't have a sufficient indication to judge immediately
	that they had asymmetric slats.

	This fits in with a pattern that's shown up in virtually
	all breeds of airliners where the cockpit's 'human interface'
	fails to supply needed information.  This shows up in a fair
	variety of accidents in various forms -- unloading the autopilot
	produces surprising gyrations, aircraft FBW control logic reacted
	to factors other than the pilot's directions and the pilot
	didn't anticipate it, etc.

	One human factors problem is how to best inform the crew of
	simultaneous failures that each can be critical.  For this
	DC-10 accident, they experienced loss of an engine at low altitude,
	followed quickly by partial loss of hydraulics and asymmetric slats.
	Each of these three primary circumstances call for prompt attention,
	and cockpit warnings of these and other consequent failures
	can overload the crew with failure alarms, becoming more of a
	problem than a solution.

	Bottom line:  IMHO human factors engineering in the cockpit
	is more a more important target than airframe engineering
	for risk reduction.

Paul Raveling