A319/A320/A321 - ELAC 1(2) PITCH FAULT

[320DRIVER]

Have you ever experienced this ECAM warning [ ELAC 1(2) PITCH FAULT ] after manually restricting the movement of the trim wheel as the aircraft is automatically re-trimming to 0 after landing/during touch-&-go?

[SLT]

Nope. Why would you want to do that???

[Zeke]

Did you get a master caution, F/CTL page come up, and a FAULT light on the ELAC PB ?

Did the PITCH TRIM change to amber on the F/CTL page ?

:rolleyes:

[Professor]

We do get this ECAM caution somtimes without apparent reason. Resetting ELAC PB will cure it but the if the reset is done during taxi out, the STAB trim normally goes to ZERO and has to be reset foor takeoff again.

[countrybusdriver]

Sound a bit odd, slightly concerning if it happens during base training if you touch the trim wheel by mistake whilst waiting for it to zero!

[maxmobil]

countrybusdriver,
as the stabilizer is returning to zero anyway, there is no difference in stabilizer setting just because of ELAC pitch fault.
You don't set the stabilizer to a value other than zero during touch and go, do You ?

we get the same warning sometimes during first engine start; maybe it has something to do with tailwind conditions during first application of hydraulic pressure to the flight controls
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This Airbus is o.k., but why did it come with a RENAULT key ??

[This message has been edited by maxmobil (edited 26 March 2001).]

[countrybusdriver]

Doh!!!!!

[SLT]

From FCOM 3.02.27 p7 - Pitch function is acheived by the other ELAC. ELAC pitch fault may be triggered during engine start due to the electrical transient.
As already mentioned - it can be reset on the ground by resetting the ELAC pb.

[320DRIVER]

Unfortunately, in the case I know about, both ELAC pitch channels failed during the roll during a touch-&-go.

Obviously, the ECAM warning was inhibited due to the present flight phase. Even worse, with this failure, and with the gear down, the aircraft was in DIRECT LAW, also unannounced by ECAM due to flight pass inhibition.

The PF was a bit surprised by the "strange" handling during the take-off (it's not every day that the Airbus is flown in Direct law :)).

The first time that there was indication that something wasn't working was when the aircraft passed 1500ft AGL, and the ECAMs ELAC 1 PITCH FAULT and ELAC 2 PITCH FAULT were announced.

Since the landing gear had been retracted, the aircraft was now in ALTERNATE LAW, and the associated ECAM warning was displayed. Resetting the ELACs returned the systems to normal operations.

[upperecam]

"It's not every day the a/c is flown in direct law"

FCOM 1.27.20 P1

"...the aircraft performs the rotation in direct law"

[320DRIVER]

Dear UpperECAM, if you had continued reading the next sentence, you would have discovered that; "As soon as the aircraft becomes airborne, the system blends into flight mode."

In the case I mentioned, the aircraft was in DIRECT LAW at least until the gear was retracted, (and don't assume the gear was tucked in as soon as the aircraft was airborne), and even if the gear went up immediately and the aircraft was in ALTERNATE LAW, roll control would still be in DIRECT LAW as such, and would certainly feel more sensitive in roll.

[Flight Safety]

I just hate the idea that a mode change can occur because of inadvertent contact with a flight control by the pilot, with the pilot not immediately being notified (or made aware) of the mode change resulting from the physical contact.

On a somewhat related issue, I've heard that on older Airbus models (300/310) the autopilot can disengage in one axis only due to physical contact with the flight controls, and the system will not notify the pilot immediately that a mode change has occurred. My understanding is that this has resulted in a small number of crashes in that series. Is this also true in the newer 320/330/340 Airbus series? Are there any other instances where this can occur?

Correct me if I'm wrong, but is seems to me that the pilot should ALWAYS be notified (with a light, chime, ECAS display, whatever) when a system is designed to disconnect after a pilot manually takes the controls. The reason for the notification is to alert the pilot in case of an accidental disconnect (or mode change) due to accidental physical contact with the flight controls.

If the mode change is accidental, then the pilot did not intend to initiate it, and therefore he remains unaware of the mode change until it's discovered by other means (as in the example in this thread). It's just good system design to simply notify the pilot of the mode change.

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Safe flying to you...

[This message has been edited by Flight Safety (edited 28 March 2001).]

[320DRIVER]

Flight Safety, your comments are very valid. However, the flight control laws of the A320 family do not relate directly to the modes you are referring too.

In those cases, Airbus pilots are advised by a Flight Mode Announciator (FMA) not unlike many other modern jets.

In the case I mentioned, the pilot forcefully held the trim wheel which was automtaically (and correctly) trimming to 0 during the ground roll so I don't think it really falls under the description of "inadvertent contact with a flight control", as you described in your message.

[Flight Safety]

Alright then. This reminds me of an incident that occurred back on November 3, 1973 involving a National Airlines DC-10-10 on a regular passenger flight cruising at FL390.

About 2 hours into the cruise phase, the flight crew were discussing the system details of the autothrottle system. The aircraft had 2 independent autothrottles which worked in either airspeed mode or N1 rpm mode. The flight engineer wanted to know if the circuit breakers were pulled for the N1 tachs, would the autothrottle continue to function normally in airspeed mode.

So the crew decided to test this theory by engaging the autothrottle in airspeed mode and then pulling the circuit breakers to the N1 tachs for all 3 engines. They did this and no airspeed change was observed. So the "theory" was further tested by reducing the airspeed setting by 5 knots, and the autothrottle responded as expected. The test period was brief (only a minute or 2) and shortly thereafter the N1 tach circuit breakers were reset on all 3 engines.

Almost immediately the fan disk of the number 3 engine exploded (a CF6-6D). The explosion was uncontained and the hull was punctured leading to an immediate loss of cabin pressure. A cabin window was also destroyed leading to a passenger (Mr Gardner in seat 17H) being sucked bodily out of the window to his death during the depressurization.

The engine cowling was torn completely off of the number 3 engine which caused severe buffeting and vibration of the airframe. Wiring and control cables were severed in the lower fuselage, and electrical power was momentarily lost on all systems. The number 1 engine generator wiring was severed when fan disk debris passed under the fuselage and struck the port engine. It's oil and hydraulic pressures also went to low readings.

It took 5 minutes for the crew to restore electrical power to the aircraft systems while cabin crew helped the passengers with their oxygen masks. Two of the cabin crew in the lower galley passed out before they could get to their masks. The flight crew began an emergency descent and after electrical power was restored, they began an emergency descent and approach into Albuquerque. The leading and trailing edge lift devices extended normally in preparation for landing, but the landing gear had to be extended manually. With the oil and hydraulic pressures still deteriorating on the number 1 engine, the plane landed safely about 20 minutes after the incident began.

Post flight examination of the aircraft, CVR and FDR showed that the N1 speed of the starboard engine had reached 110 percent just prior to the fan disk explosion. The port engine suffered a punctured oil tank and complete severing of the generator wiring. The number 2 engine also suffered some fan blade leading edge damage and some compressor blade damage from ingesting small bits of the fan blades from the destroyed right engine.

So the moral of this story is that pilots should never perform the duties of a test pilot, unless you are a test pilot operating under test flight conditions.

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Safe flying to you...


[This message has been edited by Flight Safety (edited 30 March 2001).]

[320DRIVER]

Well said Flight Safety.

In fact, the crew who experienced this failure were from a major European airline and I was told that this forceful restriction of the trim wheel to get a correct trim setting for a touch-&-go, was the accepted practice which sounded really strange. That is why I wanted to see how widespread this practice was and if it was a common causal factor for ELAC PITCH CHANNEL FAULTS.

[Cmdr Data]

Had an ELAC 1& 2 fail on touchdown, we used config 3 for landing and on rollout the failure occured. Could not determine the reason for it, such is the nature if the beast.

[DoctorA300]

Restricting the trim whell from moving, should not result in ELAC 1 AND 2 fault, this should "only" cause PITCH TRIM Fault, and it shoudn´t result in Altn Law.
Maybe there where other problems aswell.
Brgds
Doc

[320DRIVER]

No other problems after the reset. The actual warnings were ELAC 1 PITCH FAULT and ELAC 2 PITCH FAULT.