Spanair theory
It is published now that some authorities have seen Spanair’s plane that crashed few weeks ago, that it’s flaps were not in the take-off position. Could be.
It is also said that no engine failure has detected and that engine fire theory is not a good anyway. We all know that a plane can take off with half engines. (Not with one engine, plane needs half the engines dear press).
But why write this? Because I have always wondered does it need flaps to be take off position? Can it take off without flaps?
And with this accident, aren’t there a warning system in every plane that take off configuration is not complete. As far as I know there is. If it worked like it should, pilot could have a warning and a chance to abort take off. Or try to put flaps down. Does that make any sense? If a pilot started to roll, is it possible to change the flap position? I mean in the runway…
Don’t Blame Bitching Betty
If it is true that the pilots left the flaps retracted as the BBC has suggested, it would be a plausible explanation for the crash. Of course, the investigation is ongoing, and we don’t really know yet.
Nearly all jet airliners have swept wings. This allows them to fly faster in cruise, but they must also go faster to take off and land. That makes flaps and slats absolutely critical.
Airliners with a heavy load of passengers and freight, and still carrying all of their fuel, require tremendous amounts of energy to take off. The crews have to consider not only the planned takeoff, but also the possibility of aborting on the runway or taking off with an engine failure. They calculate a speed for each takeoff based on flap configuration, available runway, and the ability to stop or go (abort or continue). Without flaps, the takeoff speed the pilots calculated is meaningless: the airplane won’t have enough lift to fly.
Nearly every airline’s procedures require pilots to set and verbally confirm the flap settings before every takeoff and every landing.
It is true that different airplanes employ different warning systems. MD-80s such as Spanair’s have a system called CAWS (Central Aural Warning System), that the pilots call “Bitching Betty” for its many voice warnings.
If the pilots indeed failed to set the flaps and slats, “Bitching Betty” should have let them know. But the pilots would have been responsible to set those flaps and visually check them, regardless of any aural warning.
I don’t blame Betty. Maybe it is possible that pilots did set a flaps as they should and Betty thought they did but flaps never moved. It is a long shot but is that even possible? I would think that warning system is made in a way that it “sees” the problem from the actual part of aircraft. Like in this case from the flaps, not from the gauge in the cockpit.
Make any sence?
There is some evidence that CAWS did not provide the alert it should have. That would indicate a failure of the warning system. The entire purpose of having a warning system is to warn; if it failed to do so, it failed in its essential purpose.
My point is that might have contributed to the problem, but the pilots would still have been responsible to assure that the flaps and slats were properly set.
1. They should have set the flaps and slats. (a) It is a part of the pilots’ taxi “flow” (a memorized series of steps taken on the way to the runway), and (b) it is part of the pilots’ taxi checklist, which they read to each other to check that everything was done before takeoff.
2. The pilots were responsible to actually LOOK at the flap and slat meters to see whether they were properly set.
You didn’t “Blame Bitching Betty.” However, that is the argument the BBC is advancing, and while a CAWS failure might have contributed to the accident, it probably wasn’t the only cause.
Again, all of this assumes that the pilots failed to set takeoff flaps and slats. We don’t know for a fact that any of that occurred until the investigation is complete. Which, in the end, makes all of this speculation.
As for the possibility that the pilots did set the flaps and slats, but they didn’t move into position, that is possible, but unlikely. It also doesn’t clear the pilots of responsibility (again, if that was the cause of the crash).
The flaps and slats are operated through hydraulics. If both engines are running, each engine operates a hydraulic pump. So the hydraulic pressure should have moved the flaps into position.
There are hydraulic shutoff valves in the cockpit and at another location accessible by mechanics. Is it possible that a mechanic shut off the hydraulics when the airplane returned to the gate for maintenance before the crash?
It is possible, but it sounds unlikely, because the maintenance was on a different system.
Let’s assume that the pilots or the mechanic shut off the hydraulics. This doesn’t just affect the flaps and slats. It would also affect the airplane’s brakes (which you need as you taxi to the runway) and other systems.
The pilots are required to turn on hydraulics before they leave the gate, and confirm that they actually have hydraulic pressure on each system’s gauge (another one of those “flow” and “checklist” items). They would find that after one or two pumps of the brakes during taxi, they would lose the brakes during taxi if somehow the hydraulics were still off.
When they test the flight controls, they look for spoiler deflection and elevator boost (other cockpit indicators, another “flow” and “checklist” item), which both need hydraulics.
And again, the pilots were responsible to physically look at the flap and slat gauges to confirm that the flaps moved into position.
For all of these reasons, if the pilots selected proper flaps and slats, they should have moved into position. If they didn’t, there were ample warnings that something was up, even if CAWS failed.
Finally, in the forensic inspection of the crash, the investigators will certainly look at the switch and lever positions in the cockpit. They will see whether the flap/slat lever was moved into the correct position.
Hope this helps!
Great comments. Thanks a lot for clearing our minds.