Interesting Engine Issue Situation

[pelmet]

From TSB....

C-GJVO, a Perimeter Aviation Fairchild SA227-DC aircraft, was conducting flight BLS371 from
Sault Ste. Marie (CYAM) ON. to Thunder Bay (CYQT) ON. While enroute to CYQT, the flight crew
received a right-engine (Garrett TPE 331-12UHR) low oil pressure annunciation. The flight crew
confirmed the oil pressure indication was below 40 PSI on the separate oil pressure gauge. The
flight crew elected to continue running the engine for the remainder of the flight. After landing, the
right engine torque would not reduce to flight idle, and the aircraft pulled to the left. The flight crew
pulled the right engine stop, feather and shutdown the engine while maintaining runway center line
with the application of brakes. The aircraft stopped on the runway, the other engine was shut
down, and the everyone evacuated the aircraft via the main cabin door. There was some residual
smoke from the right engine and from the 2 tires on right landing gear. There were no injuries to
the 11 passengers and 2 crew. ARFF response was activated but there was no fire.
The 2 right landing gear tires were deflated and will be replaced. The operator's maintenance
found the right engine rear turbine bearing scavenge pump had failed and the right engine oil
quantity had depleted.

[Dronepiper]

This actually bothers me a lot.

The metro has 2 separate indicators for low oil pressure. You have the annunciator light, and the actual gauge. Both indicators are hooked up to separate sensors, therefore if both indicate you have low oil pressure, you can be 100% sure you have low oil pressure in the associated engine.

Generally the safest course of action is to shut down the engine in flight. This will allow you to complete all of your checklists at altitude, and make a pre planned stabilized single engine approach and landing. The metro will fly perfectly fine on one engine in cruise, and handle great during a stabilized single engine approach and landing.

If you leave the engine running, you run the risk of the engine failing on final approach. This will put you in a much more precarious situation. If you don't make fairly immediate decisions when this happens, things can go sideways very quickly. Bearskin's fatal accident in Red Lake in 2013 is a prime example of the dangers of an engine failure on final approach.

It bothers me when crews are scared of shutting down an engine in cruise flight. You would much rather have a pre-planned single engine approach VS having the engine fail on final.

Someone could argue that "oh if the weather is bad you should leave both running." I think this is worse. Think about it, would you rather shut down an engine in cruise IMC flight and complete a pre planned stabilized approach in IMC, or lose an engine at 700ft in IMC. Of course if you have the fuel, diverting to an airport with better weather would also help.

[digits_]

This actually bothers me a lot.

The metro has 2 separate indicators for low oil pressure. You have the annunciator light, and the actual gauge. Both indicators are hooked up to separate sensors, therefore if both indicate you have low oil pressure, you can be 100% sure you have low oil pressure in the associated engine.

Generally the safest course of action is to shut down the engine in flight. This will allow you to complete all of your checklists at altitude, and make a pre planned stabilized single engine approach and landing. The metro will fly perfectly fine on one engine in cruise, and handle great during a stabilized single engine approach and landing.

If you leave the engine running, you run the risk of the engine failing on final approach. This will put you in a much more precarious situation. If you don't make fairly immediate decisions when this happens, things can go sideways very quickly. Bearskin's fatal accident in Red Lake in 2013 is a prime example of the dangers of an engine failure on final approach.

It bothers me when crews are scared of shutting down an engine in cruise flight. You would much rather have a pre-planned single engine approach VS having the engine fail on final.

Someone could argue that "oh if the weather is bad you should leave both running." I think this is worse. Think about it, would you rather shut down an engine in cruise IMC flight and complete a pre planned stabilized approach in IMC, or lose an engine at 700ft in IMC. Of course if you have the fuel, diverting to an airport with better weather would also help.

I agree.

Some factors to consider (and most of it is pure speculation):
- They were likely above water, out of gliding distance to the shore line, this might have made them weary to shut down an engine
- CYAM - CYQT is usually the last flight of a tour around Ontario. Often, the fligths are coming in to CYQT with minimum fuel. That might have made the crew less acceptable to diversions or slowing down and potentially burn more fuel, depending on wind and fuel burn. They might also be unaware of the fuel burn/airspeed/performance during single engine ops, it's not something that is often emphasized during training
- I don't recall the oil pressure limits, but if you get the warning, and the needle is just below the minimum red line, it's mentally quite easy to consider it as a fluke in the system. Which unfortunately happens too frequently. If you've had a few false warnings, or have had colleagues experience false warnings, it seriously affects your faith in the warnings. It doesn't sound like it was a situation in which the low oil pressure warning came on and the oil pressure gauge read 0.

[goldeneagle]

Continue with an engine running out of oil, there is history.

Just read up on the NTAir incident at YVR a few years back. Failure on short final that ended up a big fireball on the hiway just short of the threshold for 26.

I cant think of a single reason that would convince me to leave an engine running if I'm in an airplane quite capable of flying on one, and the guages are telling me that an engine is critically low on oil. Flying with one shut down is inconvenient, but after it shuts itself down, it can become catastrophic.

For perspective, I have never read an accident report that says folks died from shutting things down on a faulty indication. I have read many, often fatal, accident reports where folks did not correctly action items like this.

[‘Bob’]

Just read up on the NTAir incident at YVR a few years back. Failure on short final that ended up a big fireball on the hiway just short of the threshold for 26.

The engine didn’t fail. An engine failure would simply autofeather.

The pilot only advanced one engine instead of both at low speed because the checklist recommended reduced power settings on the engine with low oil pressure.

Self induced Vmc roll… which will happen regardless if the aircraft is mishandled. All he had to do was advance the other engine.

[J31]

Just read up on the NTAir incident at YVR a few years back. Failure on short final that ended up a big fireball on the hiway just short of the threshold for 26.

The engine didn’t fail. An engine failure would simply autofeather.

The pilot only advanced one engine instead of both at low speed because the checklist recommended reduced power settings on the engine with low oil pressure.

Self induced Vmc roll… which will happen regardless if the aircraft is mishandled. All he had to do was advance the other engine.

The TPE331-12 does NOT AUTOFEATHER when it quits! This misunderstanding of the TPE331 will get you killed!

If the engine quits, strain gauges sense a negative torque situation and dump oil from the propellor dome, driving the blades to about 30 degrees. This is called NTS (Negative Torque Sensing) You still MUST feather and secure the engine.

If the oil pressure is below 40 psi the engine will begin eating itself and slowly start to fail. As the engine speed slows below selected engine RPM, the blades could be driven to fine pitch. This will cause MASSIVE DRAG and could lead to lost of control.

TPE331-12 oil pressure below 40 psi requires the engine to be shutdown.

Anyone operating a TPE331 needs to read this Transport Canada Alert

https://tc.canada.ca/en/aviation/refere ... no-2014-04

To all owners, operators and maintainers of Honeywell TPE331 series engines

Issuing Office: National Aircraft Certification
Document No. : CASA 2014-04
File Classification No. : Z 5000 35
Issue No. : 02
RDIMS No. : 99456688
Effective Date: 2014-10-22
Purpose:
To emphasize to the owners, operators and maintainers of Honeywell TPE331 series of engines that:

The NTS System fitted on the Honeywell TPE331 engines is not an automatic feathering system. It will function only when certain preset conditions and parameters are met, it is therefore, not always available;

Under certain conditions and settings, such as retarding the Power Levers from the forward position, misrigging of the NTS System or improper fuel valve setting, the NTS System may malfunction or not function at all;

The primary reason of the NTS System is to provide propeller drag reduction by driving the propeller blade angle towards feather at the optimal rate in case of an engine failure or shut down, and the secondary reason is to assist in the air start;

The NTS System may induce a false sense of feathering. Flight crew must guard against this perception and be aware that full feathering can only be achieved by manually feathering the propeller;

Asymmetric drag, under certain condition and configuration could cause the loss of control at speeds above Vmca, especially in the landing configuration when the propeller of the failed engine has not been feathered.

Background:
The NTS system description in the aircraft flight manual (AFM) and pilot operating handbook (POH) may cause the flight crew to incorrectly believe that it is an automatic feathering system; is always available; and will always activate in the event of a power loss or engine shutdown. This misconception has not been clarified during the pilots training sessions.

The NTS drag protection system is designed to reduce the urgency with which the pilot is required to feather the propeller of the failed engine and allows him/her to concentrate on controlling the aircraft. Misconception of the NTS System has distracted the flight crew from carrying out the appropriate emergency procedure. Flight crew must always be aware that where the propeller is required to be feathered, it can be done only manually and they cannot expect the NTS System to do it.

The operation of the NTS System has misled the flight crew into believing that the propeller has been feathered. This has distracted them from manually feathering the propeller, contrary to the prescribed emergency procedures. Consequently, when Power Levers were retarded it interrupted the drag protection provided by the NTS System and surprised the crew with asymmetric drag. If this happens during the approach, the unexpected asymmetric drag could startle the pilots and result in loss of control.

Recommended action:
The owners, operators and maintainers of Honeywell TPE331 series of engines must ensure that:

The AFM, POH, standard operating procedures (SOP) and Supplementary Materials, as applicable, must clearly establish that the NTS System is not designed to automatically feather the propeller but only to provide drag protection; where the propeller is required to be feathered it can only be achieved by manually feathering it.
The AFM, POH and SOP must be reviewed in conjunction with Honeywell published Pilots Tips for Honeywell TPE331 Revision 1 dated October 2009; Operating Information Letter (OIL) OI331-20R1 dated March 10, 2009; or Operating Information Letter OI331-21R1 dated March 10, 2009 (as applicable). Though AFM and POH over-ride the Pilot Tips and OIL, it must be ensured that these documents are aligned and any apparent disparity must be clarified by the engine manufacturer. Subsequently any affected SOPs must be amended to comply with the manufacturer's instructions.
The initial and annual technical ground and flight training program for flight crew operating these engines should contain a detailed syllabus on the NTS System, including its normal, abnormal and emergency operations. Any misconception concerning the operation of the NTS system must be clarified during these training sessions.
Secondary recommendation
It must be emphasized that in any engine failure situation, flying the aeroplane is the paramount important action; followed by the memory items and then the checklist items.

The pilot must avoid windmilling within the Shaft Critical RPM Range as this may cause damage to the engine.

Avoid windmilling in the wrong direction (propeller rotation reversed) due to excessive sideslipping as this may cause damage to the carbon brushes in the Starter/Generator. Slideslipping may be induced by excessive rudder deflection or trim in the wrong direction.

[Heavy Rayn]

The above comment is a good read and should be common knowledge for anyone that is operating or has operated a TPE 331 powered aircraft. Low oil pressure on this eng? Shut it down. Do NOT leave it running. Could’ve been catastrophic.