Spanair accident at Madrid

[justme69]

Just for clarification, there have been several accidents of this type where slightly different reasons have led to similar consecuences.

-There have been cases where a perfectly serviceable TOWS was disconnected by a "human" pulling a c/b (MAP case in Lanzarote).

-There have been cases where a (electrically) "working" TOWS has not been activated due to a bad switch in the thrust handles (727's like in Delta Dallas accident or 737 in DCA incident). In those cases, a theoretical "lighted indicator" that would've signaled the TOWS was powered on the ground would've given the false sense of security that the TOWS was working, when it actually wasn't for practical purposes.

Even worse, in Dallas case, the switch was determined to work "some times", perhaps once every 2 or 3 actuations, so checking the TOWS would've only LIKELY, but not for sure, have detected the malfunction. Neither an "operating" lighted TOWS indicator nor a test are 100% effective measures to know the TOWS won't fail when it's needed. The most effective measure given current designs is the test shortly before each takeoff, though, as it would most likely catch an inop TOWS on time. The pilots are not going to be staring at a lighted TOWS indicator to see if it's on while they take off. And having it "on" doesn't mean the TOWS will work if the switch in the handle is broken or if the loudspeaker is blown, i.e. Only chance of catching it is to test it and pray it doesn't fail from that time until the time it's needed.

(Incidently, in Dallas Delta accident, i.e., the crew answered the checklist FLAPS/SLATS as the correct "15/15/Green light" while the FDR and the CVR showed no indications that they ever moved the handle nor did they really had appropiate time to have done it as they moved to the next item in a like less than a second. So paying "lip service" to checklists is a long known fact.)

-There have been cases where the TOWS failed for undetermined reasons (Northwest in Detroit).

-There have been cases where (probably) the TOWS failed due to part of the ground/air logic circuit failure (Spanair).

-There have been cases where the TOWS worked just fine but the crew failed to take appropiate action (LAPA).

-There have been cases of accidents with victims where it wasn't clearly reported why or if the TOWS failed (Lufthansa in Nairobi or India Air in Hyderabad).

But the short story is: quite a few airplanes have tried to take off with incorrect configurations, when procedures, training and aircraft indicators (flaps/slats panel indicators) should've made it clear that this wasn't a good idea. Most of them have been "saved" by the TOWS. Of the rest, most have crashed and some have saved the day one way or another (quick command of flaps, reducing angle of attack and flying ground effect, aerodynamics conditions allowing for clean takeoff with little performance penalties, etc).

But we come back to quite common even nowadays scenarios of landings with gear retracted (forgotten, usually on small private planes, but even recently in small and even some large airliners), spoilers in the wrong setting, or similar events. They range from simple oversights to configuration alarms being turned off by the crew while dealing with another malfunction that made them distracted.

A 100% reliable TOWS is not "impossible", but it's probably not "worth the time and effort". Such a design and expense is probably better use on other, more vital systems. But a much better design is certainly possible, one that is close to 100% effective and today's technology should make it more than cheap enough to be considered. So why not?

But the main reason for these accidents, crew failure to perform vital actions for which they were trained and under not overly-stressful circunstances (well rested, before a takeoff, plenty of time to double check on 20 minutes long taxiing... some of you would simplify it as "pilots simply screwed up"), will not really be solved, only "masked" by the more effective TOWS.