Symptoms of a "Rare failure"

BIG, double-deck, four-engine, medium to long range, high altitude, high speed, commercial transport airplane
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SJDobby
Airman
Posts: 38
Joined: 27 Jul 2016, 07:45

Symptoms of a "Rare failure"

Post by SJDobby »

Hi

During the climb on a fair-weather flight from Havana today in a moderately-loaded B377 my engineer told me "the engines can't take much more of this" (despite there being no RPM/MAP/Trq limit-busts), so I brought the power down a bit for the remainder of the climb.

Engine 4 then exhibited the following symptoms (during the cruise) when compared with the other engines (resulting in an overhaul being required after landing):

Higher Oil consumption (not dramatic rate, but maybe double that of the others)
Lower Oil pressure (70 vs 77)
Lower MAP (36in vs 39)
Lower Torque (158 vs 165)

The RPM was the same as the other engines but wavering a bit (wobbling about 70rpm either side of selected).

Cylinder Head Temp matched other engines at same cowl flap setting.
Oil Temp same as other engines (77deg)
Fuel Pressure matched other engines

No smoke or other symptoms were evident from that engine during the flight.

In the absence of the "full maintenance report" we get in certain other A2A products, can anyone comment on the most likely cause of the above "rare problem"?

Cheers
Simon
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alan CXA651
Senior Master Sergeant
Posts: 2438
Joined: 15 Mar 2016, 08:23

Re: Symptoms of a "Rare failure"

Post by alan CXA651 »

Hi.
What was your BMEP showing on engineers panel , this is the true power the engine can give you , and under certain outside air temp conditions , can mean you are pushing the BMEP beyond its max , yet still be below max RPM / MAN for takeoff and climb out , also did you use the water injection during takeoff.
Regards alan. 8)
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SJDobby
Airman
Posts: 38
Joined: 27 Jul 2016, 07:45

Re: Symptoms of a "Rare failure"

Post by SJDobby »

I didn't note the BMEP on Eng Panel but the torque-meter on the main panel didn't (I think) ever bust any limits.

However, it is possible I may have neglected to turn on the ADI pump (it was the second attempt at the flight as FSX froze during first attempt, and don't recall whether or not I turned ADI on), so maybe detonation was the cause.

Cheers
Simon
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wrkempson
Airman First Class
Posts: 79
Joined: 17 Apr 2012, 17:26

Re: Symptoms of a "Rare failure"

Post by wrkempson »

I had the same thing happen last night. Shortly after takeoff I checked on engine conditions with Shift-2 which informed me I had engine trouble. All metrics were in the green but with a slight variance of RPM for #4. Returned to the airport and shut down. Shift-9 said #4 had experienced a rare problem, was in poor condition and needed a complete overhaul, this after 12 hours. The other three engines had the same hours and were in excellent condition.

Rare problems often have rare causes. My thought is that this is a category used to generate a random engine problem and no particular blame adheres to the pilot for the problem. What we do with the problem is the issue.

Wayne

SJDobby
Airman
Posts: 38
Joined: 27 Jul 2016, 07:45

Re: Symptoms of a "Rare failure"

Post by SJDobby »

Hi Wayne

This "you experienced a rare problem" reminds me of the apocryphal "squawks" that got reported by military aircrew, with one being:

Pilot writes in maintenance log:
"Something is loose in the engine"

The next day the pilot reads the engineer's response in the notes:
"Something has been tightened-up"

Cheers
Simon
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alan CXA651
Senior Master Sergeant
Posts: 2438
Joined: 15 Mar 2016, 08:23

Re: Symptoms of a "Rare failure"

Post by alan CXA651 »

Hi.
In simons case the failure was due to pushing the engines beyond their limits, thats why the engineer claimed `the engines cant take much more of this` , this is why i asked what the BMEP was as this is the engines true power output , on take off run always glance at the engineers panel at the BMEP as well as your RPM/MAN gauges which ever gauge reachs the max mark first is the max power that can be applied for that takeoff , some days the RPM/MAN will hit the max limit first other days it will be the BMEP , go beyond these limits at your peril also do not keep the power at this setting for more than a couple of mins , the engines on this aircraft where prown to failures , and use the ADI if aircraft is on the heavy load side , it gives extra takeoff power , but turn the ADI off and bring engine power back as soon as gear and flaps are up and level off to allow speed to build up , then adjust engine power to climb rate , and adjust climb rate to maintain about 500fpm climb rate.
regards alan. 8)
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