Bearskin Metro 3 CYRL accident - Speculation thread

[Doc]

Very doubtful of a missed approach. As Ki-ll mentioned, the added power after the failure was probably mistaken for a missed approach, given how close they were when the engine had issues.

Don't know there Maynard, the folks at YRL have witnessed more than a few missed approaches, due in part to the wonderful weather observers?
Until I hear ANY "evidence" of an on board emergency, I'm chalking it up to a pooched missed approach.
Please, prove me wrong.
Wouldn't be the first time, failing to maintain a positive climb rate has had dire results.
Unfortunately, sometimes it is that simple.
The "mystery" transmission could have been as simple as a garbled missed call.
When this sort of thing happens, it's human nature for us to think something catastrophic to be the cause. Most often it is not. Most often probable being well over 95% of the time.

[Ki-ll]

Until I hear ANY "evidence" of an on board emergency, I'm chalking it up to a pooched missed approach.
Please, prove me wrong.

Here is the source of information on engine problems

There’s no word yet on the cause of the crash, but Transportation Safety Board investigator Ross Peden, who was in Red Lake, told Global News that he interviewed the 29-year-old survivor.

“He did confirm that there was some sort of an issue with one of the aircraft’s engines,” Peden said.

If that's not good enough, then I guess all we can do is speculate and wait until the report.

[CD]

Don't know there Maynard, the folks at YRL have witnessed more than a few missed approaches, due in part to the wonderful weather observers?
Until I hear ANY "evidence" of an on board emergency, I'm chalking it up to a pooched missed approach.
Please, prove me wrong.
Wouldn't be the first time, failing to maintain a positive climb rate has had dire results.
Unfortunately, sometimes it is that simple.
The "mystery" transmission could have been as simple as a garbled missed call.
When this sort of thing happens, it's human nature for us to think something catastrophic to be the cause. Most often it is not. Most often probable being well over 95% of the time.

I'm beginning to think, they may have been setting up for a visual, the WX went down, and they allowed their altitude to decay on the go around. This happens. Too often. I'm not convinced they had an engine issue at all. Otherwise, why the hermetically sealed "final transmission"?

Well, there ya go... speculation for pilot error from both discussion threads.

[Doc]

Don't know there Maynard, the folks at YRL have witnessed more than a few missed approaches, due in part to the wonderful weather observers?
Until I hear ANY "evidence" of an on board emergency, I'm chalking it up to a pooched missed approach.
Please, prove me wrong.
Wouldn't be the first time, failing to maintain a positive climb rate has had dire results.
Unfortunately, sometimes it is that simple.
The "mystery" transmission could have been as simple as a garbled missed call.
When this sort of thing happens, it's human nature for us to think something catastrophic to be the cause. Most often it is not. Most often probable being well over 95% of the time.

I'm beginning to think, they may have been setting up for a visual, the WX went down, and they allowed their altitude to decay on the go around. This happens. Too often. I'm not convinced they had an engine issue at all. Otherwise, why the hermetically sealed "final transmission"?

Well, there ya go... speculation for pilot error from both discussion threads.

Which I withdraw forthwith. They indeed had an issue. Sorry kids. Continue.

[Ki-ll]

Here is an interesting report about a Metro, engine problems and controlability.

On 21 November 2004, the crew of a Fairchild Industries SA227-AC Metro III aircraft, registered VH-TAG, was conducting an endorsement training flight near Lake George, 33 km north-east of Canberra Airport. The flight included a planned in-flight engine shutdown and restart, conducted at an altitude below 4,500 ft (about 2,200 ft above ground level (AGL)). During the engine restart preparation, the instructor departed from the published procedure by moving the power lever for the left engine into the beta range and directing the pilot to select the unfeather test switch. These actions were appropriate to prepare an engine for start on the ground with a feathered propeller, but not during an airstart. As a result, the propeller on the left engine became fixed in the start-locks position. The crew lost control of the aircraft and it descended 1,000 ft, to about 450 ft AGL, before they regained control. The crew could not diagnose the source of the loss of control and proceeded to start the left engine while the propeller was fixed on the start-locks. As a result, the crew lost control of the aircraft for a second time and it descended 1,300 ft, to about 300 ft AGL, before they regained control. The SA226 / SA227 aircraft contain no lockout system to prevent pilots from intentionally moving the power lever into the beta range during flight. It was the first time the instructor had given a Metro endorsement and he was subject to time pressure to complete the endorsement. His ongoing difficulties in adapting to his employment tasks were not successfully dealt with by the operator. He had a limited understanding of the aircraft's engine and propeller systems, and had not practiced an airstart for 8 years as the CASA check and training approval did not include an assessment of all flight critical exercises.

http://www.atsb.gov.au/media/2393410/aa ... 89_001.pdf

[oldtimer]

Ki-II, that was an interesting article but not very relevent in this case IMHO. But, by the same token, there is a good lesson to be learned. If you are doing the training, know your subject.
The Aussies also came up with a very interesting report on simulated engine failures during training that held some relevence. What the Austrailian TSB said was that power lever chops to flight idle were not simulating accuratly an engine failure with NTS and that trainers should chop the power to zero thrust instead.
In this article, what this trainer did was the procedure for bringing the propellers out of feather prior to a GROUND start. An airstart is totaly different.
When a pilot sets the power levers 1/4 inch forward of flight idle and presses the start switch, instead of the starter rotating the engine, the unfeather pump brings the prop out of feather and the airstream through the propeller causes rotation. From there on, it is a normal start procedure with the rotating propeller supplying the rotational forces rather than the starter. This is the reason for NTS as opposed to autofeather.
This Australian trainer needs more training before he hurts someone.
I am glad you brought this up because someone may learn from it.

[Ki-ll]

The only reason I posted that incident report is because it is the only piece of information that I found which talks in practical terms about how much of an issue a windmilling propeller on a geared engine is. Since there is a possibility that the NTS system might not have worked on FFZN it was interesting to see what actually happens. The start lock fixes the propeller angle at 9 degrees on Metro III with McCauley propellers, which is lower than the minimum angle beta follow up system would allow (between 15 and 20 degrees depending on a power lever position), so probably in this case they had more drag than would occur otherwise.
I looked into the NTS system and it seems like a fairly reliable system, there is a torque ring with three arms and a valve. I can hardly imagine something like that failing, but I guess anything is possible.

[YQkC]

I'm pretty sure in the event of an engine failure if the NTS system fails to work all of the oil pressure in the prop hub will, in fairly quick fashion, disappear and the prop will go toward feather. The start locks will not engage unless the power lever is held in Beta during deceleration. The locks are spring loaded pins that are held out by centrifugal (or centripetal depending on who you talk to) force. As the prop slows the spring force pushes the pins in to a groove that prevents the prop rotating (via speeder spring force) toward feather as oil pressure in the hub diminishes. If the power lever isn't held in reverse the blade angle will already be forward of the start lock pins and they will not catch the blade preventing it going to feather. On the other hand you could argue there may have been a catastrophic failure of the prop governing system and/or the gear case. Point is who the f@*ck knows. Maybe the TSB, maybe not.

[Ki-ll]

I'm pretty sure in the event of an engine failure if the NTS system fails to work all of the oil pressure in the prop hub will, in fairly quick fashion, disappear and the prop will go toward feather. The start locks will not engage unless the power lever is held in Beta during deceleration. The locks are spring loaded pins that are held out by centrifugal (or centripetal depending on who you talk to) force. As the prop slows the spring force pushes the pins in to a groove that prevents the prop rotating (via speeder spring force) toward feather as oil pressure in the hub diminishes. If the power lever isn't held in reverse the blade angle will already be forward of the start lock pins and they will not catch the blade preventing it going to feather. On the other hand you could argue there may have been a catastrophic failure of the prop governing system and/or the gear case. Point is who the f@*ck knows. Maybe the TSB, maybe not.

I am trying to understand why would the oil pressure disappear in quick fashion. I am thinking that in case of an engine failure the engine will try to spin as fast as it can, that means it will spin at close to 100 or 97%, depending where speed levers were (probably at 100%), especially with the NTS not working and then rpm will decay and with it oil pressure. In my memory the oil light on start up goes out somewhere before 60%. I could be wrong though.

[rigpiggy]

been a while, but my understanding is oil loss, prop goes to feather. However any other failure, if engine is turning it will supply oil pressure and prop will try to go full fine, until NTS cuts in

[Ki-ll]

It cannot go to full fine because of Beta Folloup system which is part of Propeller Pitch Control. If NTS does not work and the Power Lever is at flight idle the minimum angle a propeller will go to on -11 and -12 engines is 15 degrees, maintenance specifically checks for that.

[boeingboy]

First of all - if the engine fails there is no way its going to be spinning at 100% Secondly - the NTS system simply helps the pilot, it lessens the drag on the prop slightly, untill the pilot pulls the fancy red knob.

Besides - all this is happening faster than we can talk about it. Whatever happened - happened quick and Im sure the crew had run at least some of the drills. There would not have been time for the blades to drive to some rediculus number to cause an issue. Even if the NTS system failed (and there is no evidence it did) it is not some magic system that makes everything OK. Its just helps out. If it failed altogether - it will not cause a complete failure of the prop to feather.

[Brown Bear]

So, does anybody "know" anything, or are we still quarterbacking after the fact? If the investigators would release the rumoured transmission about the "problem" it would tell volumes.

[Ki-ll]

First of all - if the engine fails there is no way its going to be spinning at 100%

I re-read my post and realized that it is easy to misunderstand what I meant.
What I meant is that with NTS system not working rpm will decay much slower than with it being operational and initially you might not even see an rpm decrease.

[Ki-ll]

.

[Airtids]

After recent events, I can assure you that a TPE331 can go from hero to zero in the blink of an eye. One thing to remember is that even in fine pitch, if the engine isn't turning, the drag is drastically minimized. Small consolation, I know...

VERY interested to get some real info as to cause of this one.

[Brown Bear]

I flew Metros for two years. Granted, they were the 2, and not the 4 or the 23, but I'd be really interested in how the aircraft became unflyable. I did one precautionary shut down half way between JFK and UYL in the middle of the night, and the beast behaved like a total pussy cat. We just kept going. I've long forgotten everything I knew about the airplane, but I don't recall it being a fire snorting beast from Hell.

Okay, I'll be honest. We did a two engine take off from JFK with reduced power on the right one. We had suffered a bunny rabbit prop strike, and after much discussion with our mechanical gurus, it was decided we could bring it home empty on one. Out of a thousand feet, I feathered the right one and headed north. Absolutely zero issues. They changed the engine in YUL. Guess the 331 was not that fond of rabbit.

[spaner]

You need a new thread to discuss the single speed engine and it's quirks.
You're on the right track though Ki-ll. Here is a few generalisations to rebuff 90% of the statements.
A failed engine is one where the fire is out, that's it. It is now referred to, as a hunk of metal.
That spinning hunk of metal, will make oil pressure all day long.
The governing system will "attempt" to generate 100% RPM (74% N1 in the gate).
The system will do this by reducing blade angle, regardless of drag or deceleration to the aircraft.
The NTS system works opposite to the above, preventing the governing system from spinning the aircraft (negating negative torque).
All three aspects of controlling the failed engine, depend on one part...the feather valve.
Without the ability to dump the oil pressure, the condition will only worsen. (note, beta-follow-up MAY, save your bacon (long term-Vmc) in a perfect senario, it's never been attempted)
And most important, it's the good engine that will kill you...
Keep learning. I use what I call rule "20" for a failed feather valve.
Bad-PWR-LVR to firewall (beta follow up)
Good-PWR-LVR to 20%
Vmc+20
20 degrees nose down

And, you have 20 seconds...

NB, this little engineering oversight could have been fixed with a simple retro fix, parallel overboard dump valve. but an "inflight" failure is SO rare, it hardly deserves mentioning. Then again, we train for the recovery in the SIM, don't we...

[Ki-ll]

Wow. Very well said in very practical terms.
My understanding is that beta-follow up is there not to reduce the drag in the long term but to prevent the blade angles going to full fine in the first moments of engine failure. After control is regained (if it ever will be) it is more beneficial to get the propeller to the lowest possible angle, since that way it will spin this hunk of metal at a lower rpm hence lower drag (depends on airspeed too, but at lower speeds you definitely would like that propeller at the lowest possible angle).

[spaner]

Ki-ll, keep learning...

Best,

(too many PMs on that post, snip)