Again, warning everyone that this is just "rumors" I'm talking about here and that I have NO specific knowledge on the aviation industry, it seems that another sign of these types of WOW sensor related malfunctions is, as described, automated flight control systems ("computers") may "act weird" when they receive grossly (over the limit) temperature readings from the outside air temperature sensor (due, i.e., to the heater being on while on ground for a long time on a hot day).
The first reports that I heard is that the pilots "felt" like the engines were "accelerating and deccelerating" erratically-quickly during take off (a real bad time for this to happen). At first, it was thought it could've been some malfunction with the autothrottler, it was rumored.
Wings1011 explanations makes it all look much clearer now. Is there a way to check what the probe's reading is in the cabin? If so, a sanity check could also be a good idea?
Obvioulsy the Spanair pilots noticed either the "impossible" temperature reading or some other sign that made them know there was something wrong with the "heat probe".
In other, more automated airplanes, like I think some airbusses may be, what would happen if an automation-assisted take off is attempted and an air temperature probe gives, due to a malfunction, a temperature reading of say 8º when the actual temperature is 28º?
Due to engineer performing their daily check and pulling this c/b to be able to check the strobe lights working on GND. A Std procedure since decades on the type among engineers worldwide.
I find this very strange, since we never pulled that breaker out during daily checks on our fleet. I worked with MD-80s and DC-9s for nearly ten years and never pulled the mentioned CB, ever. As I recall, on our fleet anyway, you could turn the strobes on turning a switch on the right hand side of the glareshield (it is possible I remember wrong, it's been a couple of years since I've been inside an MD).
Second thing is, you said they had reported thrust rating problems. Have I missed something? It is possible that I have missed such a piece after reading this thread through.
Wings 1011, Thank you for your invaluable insight.
The famous C/B L/H GND CTRL RLY also does controll the take off warnig system of the MD80 aircraft that ofcourse means if it is pulled the take off warning system will NOT work.
The inference here is that a successful TOCW check was never performed during pre-flight.I am guessing that the FIRST OFFICER performs the cockpit set-up but both pilots must check everything before taking to the skies.If they dont and only work according to SOP Areas of responsibility,they are like lambs to the slaughter.A skipper must advance his thrust levers and check that warning.He must check his consummables.He must know that the fire bottles are working .The FIRST OFFICER may be highly competent but you never abrogate responsibility.Areas of responsibility are not mutually exclusive.I can stray into his and he can stray into mine.I have no problem whatsoever with a FIRST OFFICER checking me.In fact if he doesnt,it worries me.One pilot can miss a pulled c/b or a system check,but two?Never ever let a SOP hamstring you.When you're on fire off the end of the runway,its no use saying "I was following SOP's.He was supposed to check it"
Newcomers to the thread should take the time to read all of it. This scenario was proposed as early as thread 507 by sevenstrokeroll and elaborated on by others, myself included, shortly afterwards. A disabled T/O config warning plus poor checklist discipline, leading to a takeoff without slat/flap, is unfortunately the most likely scenario for this sad accident
Regarding check of exteriour lights (strobe lights) by pulling the mentioned cirquitbraker is more or less the only easy way to verify if they are working depending of aircraft setup-Some of the aircrafts have modified the system so by just selecting the strobe switch on F/O glareshield lighting pnl it does come on. But basicly all of them I have seen during the years aircraft must be in FLT mode to get the strobe to come on, thereby engineers pulling it. Just for info our company have just the last 6 months filed no less than 6 official complains to two different maintenance providers operating in Spain for forgetting to reset C/B after carried out work on aircraft. That is then probably only a fractional of the actual ammount it has been forgotten by maintenance. Normally it is just resettet and not mentioned to anyone but since the incident and the knowlegde of the magnitude it potentially could have it have been started to be reported when found C/B in out position when entering the aircraft.
"As I recall, on our fleet anyway, you could turn the strobes on turning a switch on the right hand side of the glareshield (it is possible I remember wrong, it's been a couple of years since I've been inside an MD)."
No you can't Nelli. (Well,not on our MD's anyway) Strobes on the MD only work in the air,even with the switch on.
Wings1011; I' ve got 12 years on the MD.....good post
Just a couple of ideas----- I have a few thousand hours in the MD-88, line check pilot for a famous southern US airline. We had a procedure where we used circuit breakers as switches. Airplane on ground for more than 3 hours or overnight we pulled "red collared" CBs. Other breakers were "yellow collared" to be pulled in non-normal situations. Stay with me here:
Out loud say the word "SHOP:
OK, spell it out loud: S- H- O- P
OK, Out loud
What do you do when you come to a red light??
Most answer STOP!!!
You have just been programmed---- Now We had a crew take off from a famous downtown Washington, DC airport in a 737-800 and on the first callout after gear up, called for flaps 1, VNAV. Guess where the flaps were? Two times, the crew responded properly to the checklist challenge FLAPS ---- 5,5 and a green light Crew was "programmed" for the response and the previous crew had accidentally pulled the yellow collared CB for the take off warning system. it was early morning and the offending CB was not noticed. In almost 29,000 hours of flying, there is not much I haven't seen. When any routine is interrupted, mistakes creep in. Most of the time we are simply lucky and catch our mistakes before they catch us. Again at the previous airline, we had a procedure that required a complete before start checklist any time maintainance had been performed on the aircraft. Also, the importance of "flows" can't be minimized. Our flows in the MD-88 were extensive-but the 88 was a very hands-on busy cockpit. With a proper flow, if one thing is in place, then everything is in place. End result--I'm hoping the crew is found faultless and some bizarre mechanical failure is to blame
How many "possitions" does the Ground Control Relay has?
If you "find it in the off possition", could it just have tripped itself? (I.e. is it suppossed to trip under shortcuts or other electrical malfunctions?) Or is it totally neccessary that someone physically puts it in that possition (knowingly or inadvertenly)?
Also, is it in the pilot's mandatory checklist to check that all the circuit breakers (except those turned off for delayed maintenance) are on?
And last: Do manufacturers keep a knowledge base that could be downloaded to a laptop where a technician could type: "probe heater turned on while on ground" and get an answer such as: "check WOW sensor opened or closed", "check gnd relay CB set or out"? Shouldn't it exist?
Two more survivors have been discharged from the hospitals. Only one remains in intensive care in very serious condition.
The Gnd control relay is a circuit breaker= "on" or "off", popped or in
Forget, some operators may have done that,Idunno. My outfit has not. Strobe's only flashing when nose' s off the ground. And good that is. Always irritates me sitting behind a Boeing lining up at night with those stupid strobes on!
The DL 1141 crew were distracted by a flight attendant chatting in the cockpit and were famously discussing F/A dating habits, mixed drinks and even whether a certain "community organizer" from Chicago was suitable to be President:
When I flew the MD83 one of our setup procedures was to advance the thrust levers prior to engine start and test the CAWS (Central Aural Warning System).
Back in the day... Yep, in the old days you rang every bell and checked every light, pushed all the instrument transfer switches, even ran the trim all the way through in both directions. As you know, in modern Boeings and Airbuses you do little of this, we don't even check fire warnings, it's a maintenance function. I guess you could push up a throttle before start these days but you'd trip off the utility busses and get a call from the back. Some of these old checks were busy work for the FE and we've gradually gone to a "if it ain't broke, don't fix it" streamlined preflight.
We had a procedure where we used circuit breakers as switches. Airplane on ground for more than 3 hours or overnight we pulled "red collared" CBs. Other breakers were "yellow collared" to be pulled in non-normal situations.
The "circuit breakers as switches" has fallen out of favor with many operators as have things like closing the valve on the 02 bottle every night due to the possiblity of inducing a problem that is spring loaded to cause a mishap if the c/b or valve is not repositioned before flight.
So, was the MAD mishap due to a distracted crew with taking off with flaps up and no takeoff warning horn? I think it's looking like a very real possibility.
Good discussion, thanks for sharing. I am a PPL, but an anesthesiologist in real life. Most of our "disasters" are similar to this: violations of the "sterile cockpit" rule, excessive chitchat, and inattention to boring but very basic safety details. Thanks !