Engine Rollback?

[wmuflyguy]

What is engine Rollback?

 

[Donsa320]

What is engine Rollback?

Basically this would be the case of a turbine engine decreasing rpm without a change in throttle setting. Could be serious if the engine stagnates at some low rpm and does not respond to an increase in throttle setting. Compressor stalls or flameout could be imminent. I've never seen it and I've been flying turbine equipment since 1958. The cure is to decrease the load on the engine. Turn ON engine anti-ice to unload the compressor and turn OFF hydraulic pumps and generators driven by the engine. If the problem is stuck acceleration bleed valves that may help. If it is physical damage you may have to shut it down.

-DC

 

[Lead Sled]

I've only had one engine rollback - in a G200. It was a fuel computer problem. It was easy to resolve, it just required a reset.

'Sled

 

[slowto250]

What is engine Rollback?

This is what they call it, when an engine unspools on a Walmart aircraft.

 

[flx757]

Also, you sometimes hear people call "rollback" during engine start as the temp decreases and the engine stabilizes after start.

 

[Jeff Helgeson]

I've got a manual or two around here myself...

Also, you sometimes hear people call "rollback" during engine start as the temp decreases and the engine stabilizes after start.

I'm sure you waited for 50% N2 before making that call and putting the HP Bleed to auto?!

 

[CWASaab]

This has been a common problem on the Saab 340. Not sure of the current status of the fleet, but in my 4000+ hours in the saab I experienced four 'rollbacks'. I think Saab officially calls them 'power interuptions'. In the saab they seemed to mostly occur due to slush/ice build ups in the bird catcher part of the intake, until the slush/ice ball develops enough mass to allow some slush to make it past the bird catcher and into the engine, causing a flame-out. And this is most often with the engine anti-ice on, or shortly after turning it off. Auto-ignition has always gotten the flames going again, at least as far as I know, and acts before most of us know what is going on. The auto-ignition in the saab also has a sub-idle relight protection to keep from torching an engine that has slowed too much to support combustion safely.

That's not to say that the yaw, bang and if at night, big flame out the back of the motor, don't get your attention, and quick. But in my experience it was over before we could react. Well, over except for the paper work and monitoring the temps.

 

[Jeff Helgeson]

It's a training philosophy and CRM issue as well...

...In the sim, as on the line, a previous airline taught us to call "engine rollback on #_" in lieu of "engine fail". this does not lead the pilot to the shut down check list by assuming a catostophic failure.

The thought being both pilots would assess the engine, why it rolled back, is it still turning (N1, N2, hyrdraulics, oil pressure, etc.). Maybe a relight could be attempted, etc.

It's more about the non-flying pilot stating the conditions instead of labeling the event or giving the diagnosis.

 

[Lead Sled]

...In the sim, as on the line, a previous airline taught us to call "engine rollback on #_" in lieu of "engine fail". this does not lead the pilot to the shut down check list by assuming a catostophic failure.

The thought being both pilots would assess the engine, why it rolled back, is it still turning (N1, N2, hyrdraulics, oil pressure, etc.). Maybe a relight could be attempted, etc.

It's more about the non-flying pilot stating the conditions instead of labeling the event or giving the diagnosis.

That sounds like a good call. I'm going to discuss this with the guy I fly with. It may be worth incorporating it into our procedures.

'Sled

 

[flx757]

I'm sure you waited for 50% N2 before making that call and putting the HP Blee'd to auto?!

Actually, it's not SOP at my company to make that call on the MD-80. The only "required" calls during engine start are "Start Valve Open", "40% N2" and "Start Valve Closed".

But yes, I would wait until ALL engine indications were stable before calling "rollback", if that were my "technique" to make that call. It is also not SOP to close the pneumatic crossfeed and move the Air Conditioning Supply switch to "HP Bleed Off" or "Auto" until you come to it in the After Start Flow, after both engines are started. However, in practice, those two items are done by most guys after each engine start when the indications are stable.

As far as what the PNF calls when there is the other type of "rollback", there are only 3 calls made when the PNF notices an engine problem..."Engine Failure", "Engine Fire" or "Compressor Stall". It is not until you have reached the accel height (if this was on a takeoff), cleaned up, and completed all normal checklists, that you would begin to "diagnose". This would be initiated when the PF would query "What's my problem?". The PNF would then state.."Left Engine Failure" or whatever (Fire, Seizure, etc...), both pilots would then confirm whether there is some rotation, whether a relight should be attempted. or whether this was a more catatrophic event and then the appropriate QRC or QRH procedure would be completed.

(Caveat...these are Alaska procedures. Your mileage may vary... )

WAIT A SECOND....this is Saturday. I should be doing something, ANYTHING besides talking about training. Getting the guitars out now...see y'all...