Plane slips off runway in Madrid

[alrik]

Update from the German press: The jet had thrust reversal activated - but the investigators are not sure if it was a technical defect or pilot error. If pilot error, the pilot attempted to slow the plane down, possibly with one jet engine missing.

I can confirm that. Victims that survived say that the plane haven't got the correct power to fly and the rescue teams have encountered an engine with reverse activated.

But nobody knows... if its technical problem or pilot error.

 

[James.Denholm]

I can confirm that. Victims that survived say that the plane haven't got the correct power to fly and the rescue teams have encountered an engine with reverse activated.

But what would the survivors know? I mean, they probably don't have aviation or physics degrees, and the likely hood of them being pilots are quite slim.

 

[simonpro]

Generally if a plane takes off and then falls out the sky one can assume that it didn't have the needed power.

IMO this sounds like an issue with the thrust reverser prior to liftoff which then fully deployed some time shortly after rotation, leading to the crash. Whether this was because the pilot realised there was an issue and purposefully deployed it (not clever) or because of a mechanical fault I can't say.

 

[Urwumpe]

But what would the survivors know? I mean, they probably don't have aviation or physics degrees, and the likely hood of them being pilots are quite slim.

You have for example the observation, that the plane needed 500m more for the take-off run as usual. Frequent fliers will notice that long distance. Also, they could notice that the initial rate of climb was lower as usual. Finally, the deployment of the thrust reverser caused a sharp yaw in most other accidents (like one Lauda Air crash), which would be noticed even by somebody who flies the first time.


-----Posted Added-----

IMO this sounds like an issue with the thrust reverser prior to liftoff which then fully deployed some time shortly after rotation, leading to the crash. Whether this was because the pilot realised there was an issue and purposefully deployed it (not clever) or because of a mechanical fault I can't say.

You forget the fire in the other engine. Possibly, both events are related - A 767 crashed after the thrust reversers deployed because of a hydraulics failure. Maybe something like that played into the accident. I still look for a MD-80 manual, I had been quite lucky with the 777 manual, maybe something for the MD-80 also floats through the hexayoo.

 

[James.Denholm]

You have for example the observation, that the plane needed 500m more for the take-off run as usual. Frequent fliers will notice that long distance. Also, they could notice that the initial rate of climb was lower as usual. Finally, the deployment of the thrust reverser caused a sharp yaw in most other accidents (like one Lauda Air crash), which would be noticed even by somebody who flies the first time.

Very true. However, all could possibly be legitimate emergency procedures. I doubt that commercial pilots take off as soon as they reach the minimum ground speed (excluding, of course, the event when they are taking off from shorter runways). I also doubt that the pilot's intention was to rise quickly, he was probably worried more about getting off the ground so he didn't run off the end of the runway, and keeping sort-of close to the ground, so in the event that the second engine failed, the vertical speed on ground impact could be minimised. Not sure what to say about the reversed thrust, perhaps he was trying to "clear the engine", spitting out whatever foreign body had entered it? I mean, people do strange things when they panic. Or it could have been standard procedure to do such a thing (still on thrust reversal here) in such a situation.

 

[Urwumpe]

Very true. However, all could possibly be legitimate emergency procedures.

Wrong - legitimate emergency procedures are different. See below for your detailed arguments why.

I doubt that commercial pilots take off as soon as they reach the minimum ground speed (excluding, of course, the event when they are taking off from shorter runways).

No, you will take off when you pass the rotation speed (Vr). As you always lift-off with full thrust if possible, any difference in the distance needed to reach Vr means a technical problem.

I also doubt that the pilot's intention was to rise quickly, he was probably worried more about getting off the ground so he didn't run off the end of the runway, and keeping sort-of close to the ground, so in the event that the second engine failed, the vertical speed on ground impact could be minimised.

That is no legitimate emergency procedure. That what you describe is called pilot error. After take-off you want two things: Gain altitude and reduce drag. For the first you want a high rate of ascent, for the second you want the right rate of ascent. You don't want to fly NOE even in emergency. You want to get at least to about 3000 ft in a airliner, so you can safely align with the runway again. Too low is always bad, too high sometimes bad.

You can land practically as long as you are well above decision height. But 3000 ft is better for most jets.

Not sure what to say about the reversed thrust, perhaps he was trying to "clear the engine", spitting out whatever foreign body had entered it? I mean, people do strange things when they panic. Or it could have been standard procedure to do such a thing (still on thrust reversal here) in such a situation.

Reverse thrust does not work that way and again, you describe a pilot error - such a operation is not recommended at all for planes, which are not designed for deploying reverse thrust while in air just like the MD-80 is.

Reverse thrust does not invert air flow inside the engine, but instead directs a part of the exhaust or bypass flow in direction of flight. The engine still operates normally at high thrust. No pilot would ever even think about cleaning the engine that way. Also, when an object already destroyed the engine, you will want to shut the engine down as soon as possible, so the risk of further damages to the plane get reduced.

Again: What you imagine as emergency procedure is actually describing massive pilot errors.

The goal of all emergency procedures is NOT to solve the technical problem leading to the emergency but to keep the situation controlled. If a problem can be solved by procedures, it will get solved, if it can't be solved, other priorities are more important. Deploying reverse thrust in flight is leading almost always to a uncontrolled situation and is thus not a emergency procedure at all.

When a engine fails after you passed decision speed (V1), you have only the following option: Lift-off, raise at reduced rate to stay above stall speed and fly around the airport for landing there again. Or at least fly to a nearby airport, if this is easier as a round around the airport (Like the Concorde crew attempted in the Paris crash).

The pilot did very likely not decide to abort the flight after passing V1 - the plane lifted off before the reverse thrust activated. Either the pilot panicked (It is not that easy to activate reverse thrust, you need to overcome a friction lock) or the more likely cause is, that a hydraulic failure deployed the thrust reversal.

 

[joeybigO]

No, you will take off when you pass the rotation speed (Vr). As you always lift-off with full thrust if possible, any difference in the distance needed to reach Vr means a technical problem.

No, most airlines have a "flex" thrust takeoff, this is a trick on the FADEC telling the motor that it's colder and you can use lesser thrust on takeoff, this is a massive savings when it comes to fuel.

If you don't reach Vr this would indicate your not making power of the day, which is a thrust based on the temperature.

 

[Moonwalker]

No, you will take off when you pass the rotation speed (Vr).

The pilot flying (PF) begins to rotate the aircraft at Vr while the aircraft lifts off after passing Vlof and reaches V2 very shortly. But there might be a reason which causes the aircraft not to climb or even not to lift off the runway after passing Vr like a reverser problem which might have happened in Madrid.

As you always lift-off with full thrust if possible, any difference in the distance needed to reach Vr means a technical problem.

Unlike for the Concorde you never advance the throttles just fully forward if you mean this by "full thrust". Reduced thrust take offs are rather common because of noise abatement procedures, economy and to extend the engines lifetime. The take off thrust setting depends on the pressure altitude, outside air temperature, airport procedures and partly on airline specific procedures.

After take-off you want two things: Gain altitude and reduce drag. For the first you want a high rate of ascent, for the second you want the right rate of ascent. You don't want to fly NOE even in emergency.

Gaining altitude or a high rate of climb (RoC) can be quite difficult with reversers operating if this was the case in Madrid. It might be possible that it was not possible to climb because of massive engine problems. At least the aircraft did not climb.

For reaching 3.000 ft you have to consider the MSA (minimum sector altitude) of your destination airport. For a MSA of 7700 feet for example reaching 3.000 ft only might not be a good idea...

Reverse thrust does not invert air flow inside the engine, but instead directs a part of the exhaust or bypass flow in direction of flight. The engine still operates normally at high thrust.

It depends. Applying reverse thrust on the MD-80 below 60ft can cause compressor stalls for example.

The pilot did very likely not decide to abort the flight after passing V1 - the plane lifted off before the reverse thrust activated. Either the pilot panicked (It is not that easy to activate reverse thrust, you need to overcome a friction lock) or the more likely cause is, that a hydraulic failure deployed the thrust reversal.

Yes. I think it was a systems failure. No pilot would ever "try" to apply reverse thrust during flight since it is almost impossible as you already mentioned and totally stupid anyway.

 

[simonpro]

Joey, I thought that the md82 was too old to have FADEC. Never heard any mention of it.

 

[Moonwalker]

No, most airlines have a "flex" thrust takeoff, this is a trick on the FADEC telling the motor that it's colder and you can use lesser thrust on takeoff, this is a massive savings when it comes to fuel.

One exception was the Concorde. The standard procedure was to always advance the throttles fully forward and extend the reheats no matter the OAT or aircraft weight. Actually the Concorde was easy to fly. No different EPR settings for take off, no spoilers and no flaps. It was the first civil jet aircraft which used fly-by-wire as well as thrust-by-wire. The most complex job was done by the flight engineer, controlling and monitoring the aircraft systems.


-----Posted Added-----

Joey, I thought that the md82 was too old to have FADEC. Never heard any mention of it.

Reduced thrust take offs don't depend on FADEC only. The old Boeing 727's, 737's and so on use reduced take off thrust too. If not, maximum take off thrust is used which does not mean maximum power is used. You never set the throttles fully forward. The RPM indication never goes to or beyond 100% under normal circumstances.

 

[joeybigO]

Joey, I thought that the md82 was too old to have FADEC. Never heard any mention of it.

MD-82's have the JT-8D which have no FADEC, however still you can use a reduced EPR. They have the "envelope" for reduction in EPR. Which still have power of the day requirements, however you still make power. If you exceed power of the day or the engine does not meet the power settings, which usually a check when they go throttles up, you immediately shut down. So I think they made power of the day, they just the left engine had an event, and it is possible that both T/R's were deployed. But my thinking is that the Right side T/R was deployed, based on the trajectory, and if the left engine had the event, then you would be not making forward thrust, and you would be going down.