Spanair (SAS) MD-80 Crash on Takeoff in Spain

[HighSpeedClimb]

Here's the direct link...

http://www.elpais.com/videos/espana/fue/accidente/Barajas/elpvidnac/20080918elpepunac_8/Ves/

 

[aa73]

One of the T/Rs was inop and deactivated. It would be understandable that the crew may have deployed the operative T/R after ground contact in an attempt to reduce speed.

Regarding reasons as to why the t/o warning never sounded: As I recall, there is a weight on wheels switch on the nose gear called "ground shift", which tells the aircraft whether it is on the ground or airborne (which most jets have.) If the jet senses that it's airborne, certain things work and certain things are inhibited.

The Spanair jet came back to the gate after the crew noticed that the RAT probe was heating up. The RAT probe is one of those things that is inhibited on the ground and only heats airborne. The mechanics supposedly disabled the heater by probably pulling the breaker, and they taxied back out again. There is a possibility, not yet proven, that the RAT probe was heating not because of a heater fault, but because the ground shift switch itself may have been faulty, indicating the jet was in "air mode."

IT IS PRESUMED that the crew, which had retracted the flaps/slats on taxi in, may have forgotten to redeploy them on taxi out number 2. Now, if they indeed forgot to deploy them - and the faulty ground shift switch was in "air mode" - when they went to apply takeoff thrust, the takeoff config warning system would not have sounded - because that system is ALSO inhibited when the jet is in "air mode." The takeoff config warning yells really loudly "FLAPS... SLATS..." when the throttles are moved forward, if they are not extended.

Just speculation, but it fits reasonably well.

May they rest in peace.
73

 

[bubbers44]

The left ground control CB connects the left oleo strut gnd/air switch to about 11 relays, one being R2-5 which powers the TAT heater and take off warning system. It fails to the air position.

 

[aa73]

Air Transport

SubscribeYou are in: Home › Air Transport › News Article
DATE:17/09/08
SOURCE:Flight International

Inquiry timeline details Spanair MD-82 crash sequence
By David Kaminski-Morrow


Preliminary information from Spanish investigators details for the first time the sequence of events prior to the Spanair Boeing MD-82 crash, and the dynamics of the 20 August accident.
The Comision de Investigacion de Accidentes e Incidentes de Aviacion Civil (CIAIAC) has compiled a draft report containing initial data.
After arriving from Barcelona the aircraft parked at gate T21 of Madrid Barajas' Terminal 2, and took on 10,130 litres of fuel in preparation for operating flight JK5022 to Las Palmas, scheduled for 13:00.
Its first attempt at departure, at a weight of 64.5t, proceeded as follows:

13:06.29 With 166 passengers and six crew members on board the MD-82 leaves its gate, and the pilots deploy the flaps to a standard 11° setting for departure on runway 36L.
13:25.11 Flight JK5022 receives take-off clearance.
13:26.41 Crew reports a 'small problem' and, a few minutes later, opts to return to the apron.
​

The aircraft returned to park on remote stand R11, which is situated almost opposite gate T21.
Engineers checked the ram air temperature (RAT) probe which, according to flight-data recorder information, was showing an "excessive" reading of 105°C. The decision was taken to open the RAT probe heating circuit-breaker. The flight-data recorder subsequently detected a reduced maximum probe temperature of 30°C.
The RAT probe is linked with a relay, designated R2-5, which also has a common electrical link with the radio-rack cooling system, alternating current cross-tie, and - perhaps most critically - the configuration-warning system.
This warning system is normally active only on the ground, and is inhibited through the R2-5 relay once the aircraft is airborne. Similarly the RAT probe heating is normally only active during flight.
After the engineering work was completed, flight JK5022 made a second attempt to depart:

14:08.15 After taking on board another 1,080 litres of fuel the MD-82 leaves the remote stand R11 for a runway 36L departure. From this point onwards the flight-data recorder registers zero flap deployment, up to the end of the recording.
14:23.19 Brakes released. From this point onwards the cockpit-voice recorder reveals no evidence of a configuration warning.
14:23.28 Take-off roll commences.
14:24.06 Pilot calls 'V1' and, four seconds later, 'Rotate'. Length of the take-off roll is 1,950m (6,400ft).
14:24.25 Stick-shaker activates and, four seconds later, audio stall warning sounds.
​

Having struggled to become airborne, the MD-82 reached a height of just 40ft before descending. The aircraft rolled slightly left, then rapidly right by 20°, slightly left again and then rapidly right by 32°. During the short flight the aircraft reached a maximum pitch of 18°.

​

Flight JK5022 struck the ground with its tail-cone and, almost simultaneously, with the tip of its starboard wing and the cowling of its starboard Pratt & Whitney JT8D-217 engine.
Impact marks from this contact were discovered 60m to the right of the 36L centreline and 3,207m from the runway's threshold. Runway 36L has a length of 4,350m.
The aircraft travelled around 448m on a heading offset from the centreline by about 16°. Uneven terrain meant the jet lost ground contact, then regained it, the main part of the wreckage coming to rest some 1,093m from the initial ground strike.
Both engines separated from the aircraft. Investigators found the starboard engine's thrust-reverser, in the stowed position, about 235m from the first ground impact point. The port engine's reverser was found deployed, about 913m from this point.
At least one flap-actuator piston was found partly extended, by a distance of 12cm, but the inquiry has not yet attached any significance to the discovery.
Investigators do not suspect any fault from the engines, the thrust-reversers, control surfaces on the empennage, or the undercarriage.

 

[bubbers44]

My wife made me stop my last post so now I can finish it.

It seems the R2-5 relay failed in the de energized position. It supplies power to the RAT heater on the ground and also supplies power to the take off warning system for take off. It seems like the RAT heater problem was caused by the relay not energizing along with the take off warning system. The relay said the aircraft was airborn. No take off configuration warning allowed the no flap/slat take off. Electrical schematics will show how this relay caused both faults. Power on heaters on ground and no take off warning on the ground because the airplane thought it was in the air. Maintenance should have figured it out.

 

[bubbers44]

I meant supplies power to the RAT in the air.

 

[aa73]

Is the R2-5 relay the same thing as the ground shift mechanism (weight on wheels nosegear switch?)

 

[bubbers44]

 

[bubbers44]

aa73:

The schematic above shows the R2-5 relay in the upper left which is controlled along with about 10 more relays through the CB to the left nose gear oleo air/ground switch. Since the FDR showed nose gear going to air mode before the crash, the CB was in. The failure was the R2-5 relay failing in deenergized air mode. A shame the mechanics didn't figure it out when the RAT on same relay was getting air mode power.

 

[bubbers44]

The B1-23 CB that is just below and right of R2-5 goes to the 115vac power source. Many people though it had been pulled to check strobe lights on the ground and had been forgotten out but too many other things like flight idle on taxi out and FDR info for nose going to air mode were normal.

 

[aa73]

Thanks Bubbers, good info.