Airbus Lounge Is trim runaway easier to counteract in the A320?

[Rosstafari]

We went over pitch trim runaway in A320 sims last night. I was kind of surprised at how low key the procedure was, which was essentially "counter it with the control stick"... heavy paraphrase. The only other turbine aircraft I have experience with is the PC-12, where it was considered more of a time critical emergency, and you'd need to hit a trim interrupt switch fairly quickly before the aircraft became uncontrollable.

I feel like I'm missing something here. Does it have to do with there not being any trim tabs on the THS, so less potential of a separate flight control surface (the tab) affecting the main one (the stab)? Does it not push the A320 into as drastic of a control state as the PC-12? Something else?

I'm hitting the books to see what I can learn, but wanted to see if anybody here had something to add.

 

[derg]

"Trim" on an Airbus is kind of an interesting issue. We don't have a trim tab or surface, but we have a "Trimmable Horizontal Stabilizer"

But I need to dust off my old 320 books before I get too deep into it.

 

[CFIT99]

it's all monitored, if it's a problem they airbus will tell me about it...

of the 1500 things that can go wrong....about 3 of them require an immediate response

 

[Roger Roger]

"Trim" on an Airbus is kind of an interesting issue. We don't have a trim tab or surface, but we have a "Trimmable Horizontal Stabilizer"

But I need to dust off my old 320 books before I get too deep into it.

So does a pilatus, but a trim runaway in there is a big damn deal and if you don’t get on it with catlike quickness you better have eaten your wheaties that morning (do people still say that? God I’m feeling old). I too am interested in how Airbus keeps it safer.

 

[Rosstafari]

of the 1500 things that can go wrong....about 3 of them require an immediate response

Yeah, that took some getting used to.

*DING DING DING* "Le sigh. Jean Claude, kindly stow your tray table so we might attend to this. ECAM actions, sil vous plait."

 

[CFIT99]

....but I am Le Tired...

 

[Roger Roger]

....but I am Le Tired...

One of our new FOs is too young to know the greatness of have a nap….AND ZEN FIRE ZE MISSILES! I felt old as dirt

 

[CFIT99]

One of our new FOs is too young to know the greatness of have a nap….AND ZEN FIRE ZE MISSILES! I felt old as dirt

Ebaumsworld was the peak of the internet...full stop.

 

[Baronman]

I don’t ever remember training a trim runaway in over 10 years on le Bus.

On the ERJ yes, but that thing was trimmed way the hell up to get that long nose up for TO, and you still pulled the yoke to your lap….. and if I remember correctly , there was a limitation to start trimming nose down before you got too fast …

 

[Boots2Wings]

IIRC we did one event with a jammed/runaway trim scenario. As mentioned; it was monitored and automatically cut out with an ECAM to follow. Remember it being a non-event really.

Like you said, very different from Turboprops where things got spicy very quickly.

 

[arkflyr]

This is how you know that while based in France the Airbus isn't truly Gallic like a Dassault product is. Airbus engineers sit around a padded cubicle and try to keep everyone from hurting themselves, meanwhile over in Bordeaux they built an airplane that when the trim runs away it does a 4.5G 10,000 foot climb that has to be arrested by rolling the thing 90 degrees to get the nose down.

2 minutes and 36 seconds passed between the start of THS nose-up movement and its return to balanced position. During this time:
the load factor reached 4.6g;
altitude increased from 13,000 to 22,500 ft;
the calibrated airspeed went from 300 to 125 kts; the pitch attitude reached 41 degrees.

https://bea.aero/uploads/tx_elydbrapports/hb-n110525.en_01.pdf

Being a proper Dassault airplane it wasn't damaged during all of this and yes they did ground the fleet until they figured out what happened and fixed the problem. Just think if Boeing had grounded the MAX like that right away, it probably would have been down for just a few months and they wouldn't be stuck with having to reinvent the wheel trying to get the 7 and the 10, as well as the 777X certified.

 

[bLizZuE]

I don’t ever remember training a trim runaway in over 10 years on le Bus.

On the ERJ yes, but that thing was trimmed way the hell up to get that long nose up for TO, and you still pulled the yoke to your lap….. and if I remember correctly , there was a limitation to start trimming nose down before you got too fast …

160kts!

Can’t remember what my wife told me yesterday but I can remember a limitation on a jet I flew in 2010.

 

[///AMG]

Other than an actually jammed stab (which would not really produce "runaway") or an errant electrical signal in an actuator somewhere, I am having a hard time understanding why any FBW aircraft would ever see this failure mode? I'm used to quad channel FCS, with 3 out voting a questionable 4th. Lose two and it kicks you into a regression mode gracefully. I'm guessing this must relate to actuator failure theoretically? I've never flown a FBW aircraft that has true "trim"......like derg said, its just "trimming" out the control forces via the FCS telling the control surfaces to compensate. Don't know about the A320, but my bird is always trying to re-"trim" to 1G in the clean configuration (gear/lift devices up), without any pilot input