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What Is An Engine Rollback  
User currently offlineDreampilot From United States of America, joined Dec 2006, 6 posts, RR: 0
Posted (7 years 6 months 2 weeks 2 days 3 hours ago) and read 18842 times:

Will somebody please explain what happens during an engine rollback and what corrective action you should take. Thanks!

23 replies: All unread, jump to last
 
User currently offlineFr8Mech From United States of America, joined Sep 2005, 5327 posts, RR: 14
Reply 1, posted (7 years 6 months 2 weeks 2 days 1 hour ago) and read 18810 times:

Roll-back is when the engine decelerates uncommanded. There are numerous causes, but usually the fuel control, or some input to it is at fault.

From a crew perspective, I would assume an attempt to accelerate is in order as long as there was no vibration felt or indicated. A restart if the engine went sub-idle or shut-down (flame-out).

From a maintenance point of view, depending on the engine, we would interrogate the EEC (or equivalent) and determine the fault. If non evident, we may tap the fuel system at certain points and check pressures (older engines) or even get into a borescope, though that may not yeild any clue.



When seconds count...the police are minutes away. Never leave your cave without your club.
User currently offlineThePinnacleKid From United States of America, joined Feb 2005, 723 posts, RR: 8
Reply 2, posted (7 years 6 months 2 weeks 2 days ago) and read 18797 times:

What are we talkin' about here??? A mx issue or just in normal speech???

I often call out "Roll-back" during our ERJ engine start sequence as our ITT decreases to a normal value.... the sequence of callouts for the engine start are:

- N2 (i'm watching N2 starting to turn)
- Oil Pressue (oil pressure starting to rise)
- Ignition (Ignitions have auto turned on)
- Fuel Flow (PPH is now increasing)
- Light off (ITT starts rising somewhat steadily and quickly upwards)
- N1 (N1 is turning)

- Rollback (ITT has peaked and is dropping to normal idle values... if it does not it would be heading towards it starting limits (800 degrees celcius) and we would have a "hot" start)

- 2, 4, 6, and a half... pressure, temps, vibes are good - stable start
(20% range of N1, 400 degree range of ITT, 60% range of N1, 300 pph range... three being half of six hence the half call... then finally that engines oil pressure and temps are in the green, and the vibrations are in the green and normal)

Chris



"Sonny, did we land? or were we shot down?"
User currently offlineZeke From Hong Kong, joined Dec 2006, 8849 posts, RR: 75
Reply 3, posted (7 years 6 months 2 weeks 1 day 23 hours ago) and read 18772 times:

Quoting Fr8Mech (Reply 1):
Roll-back is when the engine decelerates uncommanded. There are numerous causes, but usually the fuel control, or some input to it is at fault.

Bae 146 - Selecting wing anti ice on at high altitude resulting is all engine rollback
B717/BMW engine - a number of uncommanded rollbacks and shutdowns in flight
CRJ - also a number of uncommanded shutdowns
777-200LR/300ER reduction to idle on takeoff when using a reduced thrust takeoff

Most aircraft either have an automatic relight or an engine relight procedure. For a rollback to IDLE, selecting TOGA can be a fix.



We are addicted to our thoughts. We cannot change anything if we cannot change our thinking – Santosh Kalwar
User currently offlineGkyip From United Kingdom, joined Apr 2006, 163 posts, RR: 0
Reply 4, posted (7 years 6 months 2 weeks 1 day 21 hours ago) and read 18744 times:
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Quoting Zeke (Reply 3):
777-200LR/300ER reduction to idle on takeoff when using a reduced thrust takeoff

What do you mean by this? Do you mean the engine rolls back on the take off roll or the thrust reduction after takeoff and reduction to climb thrust?

Gary



The strength of the turbulence is directly proportional to the temperature of your coffee
User currently offlineFr8mech From United States of America, joined Sep 2005, 5327 posts, RR: 14
Reply 5, posted (7 years 6 months 2 weeks 1 day 19 hours ago) and read 18697 times:

Quoting ThePinnacleKid (Reply 2):
I often call out "Roll-back" during our ERJ engine start sequence as our ITT decreases to a normal value

We also callout EGT rollback on engine starts. The poster stated 'engine rolback' which to me means: an rollback of all engine parameters.

As Zeke points out, several engines were/are affected by rollback under certain conditions or as random failures.



When seconds count...the police are minutes away. Never leave your cave without your club.
User currently offlineFtrguy From United States of America, joined Aug 2003, 358 posts, RR: 0
Reply 6, posted (7 years 6 months 2 weeks 1 day 18 hours ago) and read 18680 times:

Quoting ThePinnacleKid (Reply 2):
What are we talkin' about here??? A mx issue or just in normal speech???

You fly for an airline and you've never heard of an engine rollback. Please tell me you're joking...


User currently offlineZeke From Hong Kong, joined Dec 2006, 8849 posts, RR: 75
Reply 7, posted (7 years 6 months 2 weeks 1 day 15 hours ago) and read 18650 times:

Quoting Gkyip (Reply 4):
What do you mean by this? Do you mean the engine rolls back on the take off roll or the thrust reduction after takeoff and reduction to climb thrust?

For take off a reduced thrust setting was selected, and a number of engines went from takeoff power back to idle.

More details here RE: GE 90 Emergency AD (by Zeke Oct 6 2006 in Tech Ops)?searchid=169463&s=zeke#ID169463



We are addicted to our thoughts. We cannot change anything if we cannot change our thinking – Santosh Kalwar
User currently offlineThePinnacleKid From United States of America, joined Feb 2005, 723 posts, RR: 8
Reply 8, posted (7 years 6 months 2 weeks 1 day 14 hours ago) and read 18642 times:

Quoting Ftrguy (Reply 6):
You fly for an airline and you've never heard of an engine rollback. Please tell me you're joking...

No man..

If you read my post you would realize that I was making a statement for the original post'er to clarify if he was asking about rollback in ref to MX issue or ref to a callout he might have heard... if you read what I wrote you would realize that rollback as a call out during engine start is something that is quite normal and is what I WANT to say... not a bad thing... but I'm not clear as to what the Rollback he wants to know about is in reference to...



"Sonny, did we land? or were we shot down?"
User currently offlineXFSUgimpLB41X From United States of America, joined Aug 2000, 4190 posts, RR: 37
Reply 9, posted (7 years 6 months 2 weeks 1 day 14 hours ago) and read 18635 times:

Ftrguy- Apparently I am not a true god of aviation like yourself, either. Try to keep the derogetory responses to yourself next time, OK?




Engine rollback in regards to the definition of the poster is not referred to anywhere in my manuals for the CRJ, and I wouldn't doubt that it was not referenced anywhere in PinnacleKid's ERJ manuals.

Normal reference in day to day basis for "rollback" is ITT stabilization after engine start.

Rollback in regards to the original poster would be referred to as an uncommanded engine response or uncommanded decelleration. Thus, the checklist for such an occurence would be executed.



Chicks dig winglets.
User currently offlineZeke From Hong Kong, joined Dec 2006, 8849 posts, RR: 75
Reply 10, posted (7 years 6 months 2 weeks 1 day 14 hours ago) and read 18627 times:

Quoting XFSUgimpLB41X (Reply 9):

Normal reference in day to day basis for "rollback" is ITT stabilization after engine start.

Many airlines have a standard call when starting more than one engine at a time to call out "rollback" as one pilot maybe starting one, and the other monitoring an engine that is further progressed in the start.

Like the inflight rollback, the start rollback one is looking for the reduction in parameters to signal the end of the start.



We are addicted to our thoughts. We cannot change anything if we cannot change our thinking – Santosh Kalwar
User currently offlineDreampilot From United States of America, joined Dec 2006, 6 posts, RR: 0
Reply 11, posted (7 years 6 months 2 weeks 1 day 5 hours ago) and read 18550 times:

Sorry to confuse all you with engine rollback. The actual question was in regards to an interview which was "Passing the FAF, you get an engine rollback, what action do you take?" Hopefully this will clarify things a bit. Thanks!

User currently offlineZeke From Hong Kong, joined Dec 2006, 8849 posts, RR: 75
Reply 12, posted (7 years 6 months 2 weeks 1 day 4 hours ago) and read 18539 times:

Quoting Dreampilot (Reply 11):
"Passing the FAF, you get an engine rollback, what action do you take?"

I would be inclined to do a missed approach, go into a hold somewhere and sort it out. If it was a fire I would be inclined to continue.

The difference is that I see one as a non-normal unstable approach, the other an emergency.



We are addicted to our thoughts. We cannot change anything if we cannot change our thinking – Santosh Kalwar
User currently offlineSabenapilot From Belgium, joined Feb 2000, 2714 posts, RR: 47
Reply 13, posted (7 years 6 months 2 weeks 1 day 4 hours ago) and read 18524 times:

Quoting Zeke (Reply 12):
would be inclined to do a missed approach, go into a hold somewhere and sort it out. If it was a fire I would be inclined to continue.

The difference is that I see one as a non-normal unstable approach, the other an emergency.

Non-normal and unstable approach indeed, but since the FAF is still far out from the runway, I'd say I'd simply split the cockpit (i.e. designating the F/O to just fly the plane further down the planned approach, preferably though automatics) while I take a good look at the engine parameters.

In the worst of situations, there is still ample time (roughly 5 min) to simply shut down the engine and land one engine out, whereas a decision to go-around on one engine at idle (possibly even flaming out somewhere during the missed approach) would also definitely lead to a non normal situation but then at high thrust.

Obviously, the closer you get to the minima, the more go-around minded I'd be getting for this sort of event as you need to be more concentrated on the stable approach aspect and the subsequent landing and one needs to judge each situation independently, but let's say that for as long as I am not marker inbound, I would be still be 'landing minded' rather than automatically 'go minded'.


User currently offlineFtrguy From United States of America, joined Aug 2003, 358 posts, RR: 0
Reply 14, posted (7 years 6 months 2 weeks 1 day 3 hours ago) and read 18508 times:

I apologize for my earlier comments. I was extremely upset when I wrote it and I guess I took it out on him. Once again I apologize...

User currently offlineThePinnacleKid From United States of America, joined Feb 2005, 723 posts, RR: 8
Reply 15, posted (7 years 6 months 1 week 6 days 5 hours ago) and read 18322 times:

Quoting Ftrguy (Reply 15):
I apologize for my earlier comments. I was extremely upset when I wrote it and I guess I took it out on him. Once again I apologize...

It's alright... apology accepted. More importantly to me though... just read the full post next time before jumping on someone.. you would have seen I know full well what a rollback is... I was just looking for the scenario in which we are talking about because it can mean very different things.

By the way, there is no mention anywhere of "rollback" as an official term in any of our ERJ manuals... and the scenario you are ref, which thank you for the clarification Dreampilot, would actually be called by our QRH "Engine Failure/Precautionary Engine Shutdown." In general day to day operations rollback is simply the ITT "rolling back" towards a normal stable idle value after it hits its peak value during the normal engine start sequence.

Chris



"Sonny, did we land? or were we shot down?"
User currently offlineClydenairways From Ireland, joined Jan 2007, 1222 posts, RR: 0
Reply 16, posted (7 years 6 months 1 day 5 hours ago) and read 18059 times:

ALF502 engines installed on BAe146 aircraft had been prone to a phenomenon known as “rollback” ,which was an uncommanded power reduction and loss of thrust in certain icing conditions.
There were also instances where simultaneous rollback occurred on multiple engines on the same aircraft.
Aircraft were restricted to FL260 until a modification was developed to prevent this..


User currently offlineIwok From Sweden, joined Jan 2005, 1107 posts, RR: 0
Reply 17, posted (6 years 5 months 3 weeks 23 hours ago) and read 16731 times:



Quoting Clydenairways (Reply 17):
Aircraft were restricted to FL260 until a modification was developed to prevent this..

What was the modification?

iwok


User currently offlineCosmicCruiser From United States of America, joined Feb 2005, 2255 posts, RR: 15
Reply 18, posted (6 years 5 months 3 weeks 17 hours ago) and read 16291 times:



Quoting XFSUgimpLB41X (Reply 9):
Normal reference in day to day basis for "rollback" is ITT stabilization after engine start.

Since a few here have gotten their "feathers ruffled" may I remind us all that one should really qualify statements that are a/c or airline specific. For example here we never say "rollback" to confirm a stable eng start. To me a rollback is the abnormal and uncontrolled reduction in thrust and not necessarily an emerg.

Quoting Sabenapilot (Reply 14):
In the worst of situations, there is still ample time (roughly 5 min) to simply shut down the engine and land one engine out, whereas a decision to go-around on one engine at idle (possibly even flaming out somewhere during the missed approach) would also definitely lead to a non normal situation but then at high thrust.

Of course I'm speaking from only our ops but I'll make another point of view here. If you really do decide to shutdown the eng then you're obligated to run the eng. shutdown inflight chk list and brief an eng out app and ldg.. FAF inbound is not the best place to do this so yes the miss would be in order. For the most part (at least in my jet) after the eng has been shutdown if there is no apparent reason for the rollback (no fire/damage) then a re-light is an option so here's another chklist. If I'm on final and this eng "rollsback" I may just continue since I've lost no systems. I would weigh each situation on it's own in this respect considering wx, airport and what jet I'm in.

Quoting Sabenapilot (Reply 14):
Obviously, the closer you get to the minima, the more go-around minded I'd be getting for this sort of event as you need to be more concentrated on the stable approach aspect and the subsequent landing and one needs to judge each situation independently, but let's say that for as long as I am not marker inbound, I would be still be 'landing minded' rather than automatically 'go minded'.

I'm sorry but I feel just the opposite. If I'm at mins and that rnwy is 1/2 mi or less in front of me this jet is landing. If I'm out there being vectored around and this happens I'd be asking for a big vector or hold and sort it out. Sometimes the best decision may go somewhat against the taught procedures. Here's a couple of good examples. In my jet a loss of the second eng (3 eng jet) after t/o or inflight requires a big chklist long pattern and a slat/no flap app & ldg. BUT if you're on final and a second eng fails the memory items are just "flaps 28, Vapp" and you land. Different thinking for diff situations. An old trick in the sim for a 2 eng jet was V1 cut on T/O come around for the ILS and on final get a fire warning in the remaining eng. Do you go by the taught chklist and pull that fire handle? Better not or you'll never see tomorrow.


User currently offlineGetdonnie From Bermuda, joined May 2006, 50 posts, RR: 0
Reply 19, posted (6 years 5 months 3 weeks 15 hours ago) and read 16161 times:

Guys,

I am a complete novice and at best an aviation enthusiast. Your posts are overwhelmingly educational and a bit intimidating. My question pertains to the physical support systems when there is a thrust issue. Is there or will there be a comparative support system for engine thrust issues as they arise much like when the RAM turbine is deployed to supports the aircraft flaps and vertical stablizers when there are problems with the hydrolic pumps?


User currently offlineJetlagged From United Kingdom, joined Jan 2005, 2541 posts, RR: 25
Reply 20, posted (6 years 5 months 3 weeks 14 hours ago) and read 16105 times:



Quoting Getdonnie (Reply 20):
Is there or will there be a comparative support system for engine thrust issues as they arise much like when the RAM turbine is deployed to supports the aircraft flaps and vertical stablizers when there are problems with the hydrolic pumps?

There have been such systems which usually operate at takeoff to boost the thrust of engines after one has failed. The later 727-200s with JT8D-17R engines had an APR system (automatic performance reserve), the MD-80 has ARTS (automatic reserve thrust system ?). Earlier 727s had a system to trip off the air conditioning packs in the event of engine failure on takeoff and the Fokker F.28 has a similar bleed trip system. Propeller driven aircraft have auto feather which does not increase thrust but significantly reduces drag if an engine fails.

Usually these systems are armed at takeoff when all engines are set above a threshold level. In other flight phases the autothrottle can usually compensate for the loss of engine thrust automatically. In the case of the BA 777 the lack of engine response made this ineffective.



The glass isn't half empty, or half full, it's twice as big as it needs to be.
User currently offlineTdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 21, posted (6 years 5 months 3 weeks 14 hours ago) and read 16088 times:



Quoting Getdonnie (Reply 20):
Is there or will there be a comparative support system for engine thrust issues as they arise much like when the RAM turbine is deployed to supports the aircraft flaps and vertical stablizers when there are problems with the hydrolic pumps?

As Jetlagged notes, there are a lot of ways this can be addressed. On 737's, pushing the thrust levers full forward will cause the engine to go to the maximum thrust allowed for that model, regardless of the thrust rating of that engine. As a result, unless you're running the maximum thrust rating already, the engine has a thrust reserve that can be tapped in an emergency.

Tom.


User currently offlineThrottleHold From South Africa, joined Jul 2006, 655 posts, RR: 1
Reply 22, posted (6 years 5 months 2 weeks 6 days 12 hours ago) and read 15680 times:



Quoting Iwok (Reply 18):
What was the modification?

Itwas some kind of alteration to the bleed band to change the amount of airflow through the engine.


User currently offlineHAWK21M From India, joined Jan 2001, 31660 posts, RR: 56
Reply 23, posted (6 years 5 months 2 weeks 6 days 11 hours ago) and read 15659 times:



Quoting Tdscanuck (Reply 22):
On 737's, pushing the thrust levers full forward will cause the engine to go to the maximum thrust allowed for that model, regardless of the thrust rating of that engine

Thankfully some types eg 757s have EECs with supervisory & limiter functions.  Smile
regds
MEL



Think of the brighter side!
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