TransAsia plane crash

[dylan]

Scooby, someone has given you some very inaccurate info.

we have been talking about this all day at work. my coworker worked on the ATR-72 for a few years and knows the plane very well. the engines are the same as the Dash-8 and Do328 which I have quite a bit of experience with. (same engine different version) the PW120 series of engine is known as a free turbine engine. the turbine that turns the propeller is not physically connected to the compressor or its turbine. but I can assure you that it is firmly connected to the prop gearbox via a long driveshaft.

the prop turbine drive shaft rotates inside the driveshaft low speed compressor, which rotates inside the driveshaft for the high speed compressor.

basically the high speed and low speed compressor and their turbines produce high energy gasses to spin the prop turbine (known as the gas generator section on the PT6)

the ATR can start the #2 engine and then use a brake attached to the prop gearbox to stop the propeller, while the core of the engine is still running. this provides electricity and bleed air for the aircraft. they use this system instead of an APU.

the prop is a double acting design. there is no spring or counterweights to feather the prop, instead the autofeather relies on a pump to use oil pressure to feather the blades.

once feathered the prop will windmill freely, sometimes it will rotate in the opposite direction. during normal operation the prop pitch is controlled by porting high pressure oil to either side of the prop actuator.

hopefully this answers some of the questions about the engine and prop.

cheers

Dylan

[Scooby]

Scooby, someone has given you some very inaccurate info.

we have been talking about this all day at work. my coworker worked on the ATR-72 for a few years and knows the plane very well. the engines are the same as the Dash-8 and Do328 which I have quite a bit of experience with. (same engine different version) the PW120 series of engine is known as a free turbine engine. the turbine that turns the propeller is not physically connected to the compressor or its turbine. but I can assure you that it is firmly connected to the prop gearbox via a long driveshaft.

the prop turbine drive shaft rotates inside the driveshaft low speed compressor, which rotates inside the driveshaft for the high speed compressor.

basically the high speed and low speed compressor and their turbines produce high energy gasses to spin the prop turbine (known as the gas generator section on the PT6)

the ATR can start the #2 engine and then use a brake attached to the prop gearbox to stop the propeller, while the core of the engine is still running. this provides electricity and bleed air for the aircraft. they use this system instead of an APU.

the prop is a double acting design. there is no spring or counterweights to feather the prop, instead the autofeather relies on a pump to use oil pressure to feather the blades.

once feathered the prop will windmill freely, sometimes it will rotate in the opposite direction. during normal operation the prop pitch is controlled by porting high pressure oil to either side of the prop actuator.

hopefully this answers some of the questions about the engine and prop.

cheers

Dylan

Should I add I am Avionics.

When I worked Twin Otters one of the engine guys told me the prop wasn't mechanically connected to the gearbox. He said it was magnetically linked. I believed it from that day on.

I helped on many engine washed where I heald the prop.

[dylan]

Should I add I am Avionics.

When I worked Twin Otters one of the engine guys told me the prop wasn't mechanically connected to the gearbox. He said it was magnetically linked. I believed it from that day on.

I helped on many engine washed where I heald the prop.

that sounds like the kind of B.S. the engine guys would tell an avionics tech. lol

i've seen a guy try to hold on to the prop on a Dash-8 while they spooled it with just the starter. it dragged him about 2 feet across the floor before he had to let go.

[yvesff]

Scooby, someone has given you some very inaccurate info.

we have been talking about this all day at work. my coworker worked on the ATR-72 for a few years and knows the plane very well. the engines are the same as the Dash-8 and Do328 which I have quite a bit of experience with. (same engine different version) the PW120 series of engine is known as a free turbine engine. the turbine that turns the propeller is not physically connected to the compressor or its turbine. but I can assure you that it is firmly connected to the prop gearbox via a long driveshaft.

the prop turbine drive shaft rotates inside the driveshaft low speed compressor, which rotates inside the driveshaft for the high speed compressor.

basically the high speed and low speed compressor and their turbines produce high energy gasses to spin the prop turbine (known as the gas generator section on the PT6)

the ATR can start the #2 engine and then use a brake attached to the prop gearbox to stop the propeller, while the core of the engine is still running. this provides electricity and bleed air for the aircraft. they use this system instead of an APU.

the prop is a double acting design. there is no spring or counterweights to feather the prop, instead the autofeather relies on a pump to use oil pressure to feather the blades.

once feathered the prop will windmill freely, sometimes it will rotate in the opposite direction. during normal operation the prop pitch is controlled by porting high pressure oil to either side of the prop actuator.

hopefully this answers some of the questions about the engine and prop.

cheers

Dylan

Dylan has got it right, the PW100 series has 3 spools (PT, HP and LP), each rotating on theuir own bearings, ie not mechanically linked with eachother, but one of them, the power turbine (PT) spool has no compressor and is linked to the propeller via the gearbox. The PT6 is a two spool engine (HP and PT), the PT spool is mechanically connected to a planetary gearbox which turns the prop. This magnetism thing is horsehockey... PW127M engines on the ATR-72 do have propeller brakes for what we call Hotel Mode, this stops the propeller from rotating, and the PT turbines, so the gases flow over the turbines, this can only be done at ground idle and for a limited time has it kills the life of the turbine blades...

http://www.pwc.ca/en/engines/pw127m

yvesff (25 years in the engine design dept at Pratt Whitney Canada)

Edited February 7, 2015 by yvesff

[Ben Brown]

Thanks yevsff and Dylan for the more detailed explanations! It's only been 20 years since I last flew the Dash-8. :-)

Ben

[Bushpounder]

I heard he lost an engine and then shut down the other one. Poor training/piloting. I hope this returns the other crews to the sim for training.

Don

[Jennings]

Pilot shut down the wrong engine?

https://gma.yahoo.com/both-engines-lost-power-transasia-crash-aviation-official-095150422--abc-news-topstories.html

A.) Pilots (even really stupid pilots) don't shut down engines immediately after takeoff.

B.) We know ***NOTHING*** about what actually happened on board this aircraft. Period. Nothing. All we know at this point is that it crashed. The media loves to speculate on stuff like this.

[11bee]

A.) Pilots (even really stupid pilots) don't shut down engines immediately after takeoff.

B.) We know ***NOTHING*** about what actually happened on board this aircraft. Period. Nothing. All we know at this point is that it crashed. The media loves to speculate on stuff like this.

Jens:

A.) Pilots occasionally do shut down the wrong engine after takeoff. Peruse all the crash reports online, I promise you'll find some examples of this. That doesn't make them "stupid", it makes them human.

B.) If you had bothered to read the linked article, you would have understood that this theory is based on data from the recovered flight data recorder. So while we don't know ****EVERYTHING**** about this accident, there seems to be some real data being made public. Since your mouse must be broken and you can't click the link, here is some info for you:

One of the engines on TransAsia Airways Flight 235 went idle soon after takeoff, and the pilots apparently shut off the other engine before the plane crashed, according to Taiwan’s top aviation official. Aviation Safety Council Executive Director Thomas Wang, speaking at a news conference today, presented preliminary findings based on the flight-data recorders, which were recovered after the plane crashed in the Keelung River in Taipei

Edited February 7, 2015 by 11bee

[Mfezi]

A.) Pilots (even really stupid pilots) don't shut down engines immediately after takeoff.

Sorry, Jennings, but if true, this would not have been a first by any means. It also wouldn't necessarily mean the pilots were stupid, but in the heat of the moment they could simply have made a mistake by misdiagnosing a problem. Here is an accident report of a Jetstream involved in a crash here in South Africa not long ago:

http://www.caa.co.za/Media%20Statements/2011/SACAA%20releases%20final%20report%20on%20the%20Merebank%20accident.pdf

From the report:

"The Jetstream 4100 aircraft is certified to be operated by two pilots and is able to take-off and climb with one operating engine, even at its maximum certificated mass."

And the conclusion of the investigation:

"Examination of the wreckage confirmed that the right-hand engine (engine 2) had suffered a catastrophic failure of the second-stage turbine seal plate and that subsequently the serviceable (operating) engine (left-hand engine) had been shut down, resulting in a forced landing. The incorrect identification of the failed engine is attributed to the apparent breakdown of the crew resource management action within the cockpit and total deviation from the operator’s prescribed standard operating procedures.

A review of the Fuel Control Unit test and design requirements indicated that the fuel shut-off valves of both engines were in the closed position following the accident flight. No defects other than the second-stage turbine seal plate failure were found in the right engine and all the physical evidence and recorded data point to this as being the cause of failure of the engine. There were no defects found on the left engine other than the seal plate which was worn beyond limits. The physical and recorded evidence shows that the left engine was shut down and its propeller feathered."

[jester292]

Jennings was saying that crews aren't trained to shut down an engine immediately after takeoff. And he's right. We typically climb to a prescribed altitude before performing memory items and running a checklist. However, soon after takeoff we are trained to identify and verify which engine has failed and for what reasons (fire, damage, flameout).

Those are at the airline and charter operator I've flown for. Procedures may differ around the world, but I wouldn't bet by much.

Aaron

[Mfezi]

This is an old thread, but a preliminary report is out:

http://www.bbc.com/news/world-asia-33358707

Turns out it was indeed a case of the pilot shutting down the wrong engine.

[Scooby]

that sounds like the kind of B.S. the engine guys would tell an avionics tech. lol

i've seen a guy try to hold on to the prop on a Dash-8 while they spooled it with just the starter. it dragged him about 2 feet across the floor before he had to let go.

I've held the prop plenty of times on an engine wash on a Twin Otter and I wasn't thrown anywhere. You can hold the prop while the engine spools up. I don't know the theory behind it and it is now obvious the story I was given wasn't true or accurate.

Edited July 2, 2015 by Scooby

[Scooby]

This is an old thread, but a preliminary report is out:

http://www.bbc.com/news/world-asia-33358707

Turns out it was indeed a case of the pilot shutting down the wrong engine.

Which it truly looked like from day one.

[11bee]

A.) Pilots (even really stupid pilots) don't shut down engines immediately after takeoff.

B.) We know ***NOTHING*** about what actually happened on board this aircraft. Period. Nothing. All we know at this point is that it crashed. The media loves to speculate on stuff like this.

Well Jens, looks like you are wrong on both points. Pilot did shut down the functional engine and the speculation immediately after the crash was completely accurate.

I thought most modern aircraft had autofeather capabilities which would eliminate the immediate need to have to secure an engine that failed?

Another unfortunate Darwin Award.

[82Whitey51]

dupe

Edited July 2, 2015 by 82Whitey51

[82Whitey51]

Well Jens, looks like you are wrong on both points. Pilot did shut down the functional engine and the speculation immediately after the crash was completely accurate.

I thought most modern aircraft had autofeather capabilities which would eliminate the immediate need to have to secure an engine that failed?

Another unfortunate Darwin Award.

"A.) Pilots (even really stupid pilots) don't shut down engines immediately after takeoff."

Ayyyyup...happens a lot in multi engine aircraft.

In P-3s it was the FE (yours truly...) who did the actually shutting down of engines (emergency or otherwise) and prior to pulling the E Handle or chopping the fuel with the shutoff switch YOU GOT CHECKED BY THE PILOT OR COPILOT.

"Check me on 3"

"You got 3"

Boommmm

Ya know, I get that not having a flight engineer in the cockpit is a huge cost saver and that many of the functions are more or less automated in modern multi engine aircraft...but while one guy's aviating, another guy's communicating...it'd be nice to have someone completely focused on the systems that are keeping you flying. The P-8 pilots I know are figuring out real fast that it was nice to have our knuckle draggin' butts sitting up front with them.

Key word SYSTEMS. I think a lot of pilots put a lot more emphasis how they sound on the radio. I just learned that there was even a third pilot on board in the jump seat...seems none of them knew what was going on.

Oh well, he shut down the wrong engine and crashed a bunch of people in a river...

Edited July 2, 2015 by 82Whitey51

[dylan]

I've held the prop plenty of times on an engine wash on a Twin Otter and I wasn't thrown anywhere. You can hold the prop while the engine spools up. I don't know the theory behind it and it is now obvious the story I was given wasn't true or accurate.

twin otter/king air no problem. the Dash 8 has a much more powerful engine.

[Jennings]

Well Jens, looks like you are wrong on both points. Pilot did shut down the functional engine and the speculation immediately after the crash was completely accurate.

I thought most modern aircraft had autofeather capabilities which would eliminate the immediate need to have to secure an engine that failed?

Another unfortunate Darwin Award.

Really? When I posted that in February? Seems like we found this out yesterday.

[Ben Brown]

twin otter/king air no problem. the Dash 8 has a much more powerful engine.

Here's a good cutaway of the PT-6 to show why you can hold the prop and start the engine (I love this stuff!).

The blue part is a turbine engine. On the PT-6, it's actually sitting backwards. The intake is the area between the accessory gearbox and the compressor, so air entering the engine makes two 90 degree turns before it gets to the compressor. The exhaust is between the power turbine and the 1st stage reduction gear. The shaft for the red part isn't physically connected to the blue part. The power turbine acts like a water wheel, or pinwheel, and spins because the exhaust gases from the turbine engine blows across it. The PW-120 on the Dash-8 works the same way, except the jet engine part is turned around the right way, and the power turbine shaft runs through it so the exhaust flowing out the back of the engine blows across it. It produces a lot more thrust (over double the horsepower), so you can't hold the prop without getting tossed over the fuselage or across the ramp. On a turboshaft engine, like the Garrett Grenade found on Metroliners & Mu-2s, the jet engine part is physically connected to the prop gearbox, so when the engine turns, the prop turns, too.

Cheers!

Ben

[82Whitey51]

Here's a good cutaway of the PT-6 to show why you can hold the prop and start the engine (I love this stuff!).

The blue part is a turbine engine. On the PT-6, it's actually sitting backwards. The intake is the area between the accessory gearbox and the compressor, so air entering the engine makes two 90 degree turns before it gets to the compressor. The exhaust is between the power turbine and the 1st stage reduction gear. The shaft for the red part isn't physically connected to the blue part. The power turbine acts like a water wheel, or pinwheel, and spins because the exhaust gases from the turbine engine blows across it. The PW-120 on the Dash-8 works the same way, except the jet engine part is turned around the right way, and the power turbine shaft runs through it so the exhaust flowing out the back of the engine blows across it. It produces a lot more thrust (over double the horsepower), so you can't hold the prop without getting tossed over the fuselage or across the ramp. On a turboshaft engine, like the Garrett Grenade found on Metroliners & Mu-2s, the jet engine part is physically connected to the prop gearbox, so when the engine turns, the prop turns, too.

Cheers!

Ben

Who's idea was it to go try out this theory anyway? Doesn't sound safe at all. Is it normal maint procedure...or a "ya'll watch this shee'it" function?

[Ben Brown]

Who's idea was it to go try out this theory anyway? Doesn't sound safe at all. Is it normal maint procedure...or a "ya'll watch this shee'it" function?

You're supposed to motor the engine with the starter while you're washing the compressor. Even that's enough to turn the prop, so you'd have to do something to keep it from turning. If most airplane mechanics are like the ones at the FBO I used to fly King Airs for, I'm sure things started out with just motoring the engine and sort of went downhill from there. :D

BTW, everything you ever wanted to know about the PT-6 but were afraid to ask: Know Your PT-6A

Ben

[sanmigmike]

I've got a couple hours flying airplanes in the civil world (no military, P-3 or Electra time) and the last I was flying (about ten years ago) there were very very few times that the emergency checklist would call for an engine shutdown right after take off. IF the auto feather in the turboprops had worked you didn't do much until you got to the designated altitude for the airport (different for some airports and different aircraft had "standard" altitudes for starting the emergency procedures...some aircraft had an agl (altitude above ground level) and others had a msl altitude in the performance data. I don't know how many times I'd hear on a six month check "engine fire on number one" and I'd respond..."cancel the bell" and we would get the gear up like a regular take-off and inform the tower or departure and then wait and wait and wait and wait and did I mention...wait! The turboprops we would confirm the auto feather and wait. The non-flying pilot and or the FE would look at the gauges and report what was going on, low oil pressure or whatever...and confirm what engine was the problem child. But if you were climbing and all was pretty much okay you didn't screw around until you got some altitude! Ask a Swiftaire crew among many others about getting too rushed shutting down an engine. (Yes, I've had pylon mounted engines burn off the wing in the sim...and we were assured that was pretty much true to life...)

Now if we had no auto feather we would confirm there was indeed a problem and if there was one we would feather and shut down the engine right away (been so long since I've flown a piston twin I am not going to comment on those). The non-flying pilot would do the work and the flying pilot would call the checklist and confirm the correct lever or control before the non-flying pilot would manipulate it. In the heavy jet I flew the FE and the non-flying pilot would do the checklist as a team. verifying and confirming and keeping the flying pilot informed. The one item we worked on after take off but before the safe altitude was getting a "Thrust reverser unlocked" light. A very bad light indeed and that called for power to flight idle right away and go right on and shut that engine down!

I have to admit that I really liked having a flight engineer. A good one helps a fantastic amount (we had only PFEs so they were not going to upgrade or downgrade depending upon your view) but a bad one is a mess. We had only a few bad ones.

Another time to not rush (or times) is certain smoke problems and trying to isolate a bus (or other system) causing problems. If you are trying to clear smoke or figure out where it is coming from you have to give it time for the smoke to start to clear or quit increasing. Some studies showed that crews were running the whole checklist that had them isolating and then powering buses back up in seconds and doing four or five or six or ten buses in two minutes...and learning nothing about the problem, but the checklist was done ;-).

I was flying a four engine jet with one company and they decided not to do the verify and confirm stuff. So I was in the sim with a very sharp FO and we had lost two engines already. Started to lose another one and he started pulling levers and so on and I have to drop the nose to get some speed and I was running out of ideas and altitude. I look at the engine gauges and realized he had shut down my one good engine. I pointed that out to him (in his opinion rather calmly and he was very grateful for that kindness...it had been a long day in the box with some problems with the sim...we had emergencies that the check airman didn't program in...what fun! Things get interesting when the check airman is going WTF!) and suggested that he pull out and do the engine start in flight checklist for the engine he had just shut down and then do the shutdown list for the engine that had failed. He did so and we got it started and didn't hit the ground (we were in a wide downwind leveling off at traffic pattern altitude when it happened), staggered around and got a good landing out of it and the beers tasted great less than an hour later! We started doing the verify and confirm stuff not too much time after than...LOL!

[11bee]

I've got a couple hours flying airplanes in the civil world (no military, P-3 or Electra time) and the last I was flying (about ten years ago) there were very very few times that the emergency checklist would call for an engine shutdown right after take off. IF the auto feather in the turboprops had worked you didn't do much until you got to the designated altitude for the airport (different for some airports and different aircraft had "standard" altitudes for starting the emergency procedures...some aircraft had an agl (altitude above ground level) and others had a msl altitude in the performance data. I don't know how many times I'd hear on a six month check "engine fire on number one" and I'd respond..."cancel the bell" and we would get the gear up like a regular take-off and inform the tower or departure and then wait and wait and wait and wait and did I mention...wait! The turboprops we would confirm the auto feather and wait. The non-flying pilot and or the FE would look at the gauges and report what was going on, low oil pressure or whatever...and confirm what engine was the problem child. But if you were climbing and all was pretty much okay you didn't screw around until you got some altitude! Ask a Swiftaire crew among many others about getting too rushed shutting down an engine. (Yes, I've had pylon mounted engines burn off the wing in the sim...and we were assured that was pretty much true to life...)

Thanks for the insight. I assume the ATR would be equipped with auto-feather, can't image what would have possessed the pilot to start shutting down an engine a thousand feet off the ground.

Such a waste.

[sanmigmike]

Thanks for the insight. I assume the ATR would be equipped with auto-feather, can't image what would have possessed the pilot to start shutting down an engine a thousand feet off the ground.

Such a waste.

Indeed such a waste.

I have NO ATR time but I think all the turboprops I flew except the Metro II's had autofeather. Poking around the net I read the ATRs do have autofeather and I think also a system to increase the power on the good engine. One possible exception in my flying was the light Bandits (Emb 110s that had a 12,500 lb max take off weight). Most of the Bandits I flew were the heavy ones (I'd guess less than 50 hours of light Bandit time and more thousands of heavy Bandit than I want to remember...heavy in pitch, no auto pilot and no flight director and needed more power) and I know they did have auto feather. As long ago as that flying was it might have had to do with the fire bottles or something else for the "important" difference between the light and heavy Bandits. If memory serves (for example my Metro time is over thirty years ago) the Metros I flew had no auto feather but did have NTS (Negative Torque Sensing) that kinda drove the props toward feather BUT didn't feather them. Not too unlike all the light piston twins (biggest piston twin I flew was the PA-31-350 the Piper Navajo Chieftain, 350 hp a side...not a bad airplane) I flew the Metro II was more than a bit marginal losing a engine right after take off at any normal weight and that also meant that when doing a single engine landing you could have to get in a configuration that meant once selected (flaps usually past a certain point) you were not going around. I used to joke all the Metro needed was about 1000 hp a side and some more wing...and that is pretty much what they did for the III but a rock that flew the IIs would have thought the same thing.

I seem to recall that all the things I flew with autofeather...we had to arm and check the system before each take off, looking at PRUNE I get the impression the ATR does not require that. I was told that the FAA said that systems had to be checked before possible use in most cases and the reason that landing data in the US does not take into effect reverse thrust is that with the exception of certain DC-8s you can't check reverse thrust in airliners so the landing data assumes no reverse thrust...dunno if that has changed but I like the idea of checking something like auto feather before each take off. In the Shorts 360 we had to do a RTOP check on most, and all full power take offs I think...but my Shorts 360 time is about thirty years ago!, enjoyed that airplane, slow, no autopilot, could be handful at times but fun...RTOP was Reserve Take Off Power, one engine failed the other would go to a higher than take off power setting all by its wonderful little self! (I used to tell my FO's that if it looks like we are going to hit the ground and more power might prevent that and we do hit the ground and I die and the power levers are not actually bent forward and you live...I will haunt you the rest of your life! (We got 150% Tq indicated out of a pair of engines in one airplane {not a Shorts} one night and I don't regret trashing them a bit...if we actually trashed them...they did keep running for almost another hour! Any way the engines were in a lot better shape than if we had tried to get them to fly through a mountain! :D The power levers were not bent but they were as far forward as we could get them...)

I've read that the Captain didn't handle check rides too well. Even would fumble starting the engines. Dunno if the Captain started the engines in the ATR but goodness, doing something you do every day you fly and having problems with it. I'll bet I could start pretty much everything I flew for a living that that I was the crew member doing the starting after a few minutes thinking and being back in the airplane. Most the Check Airman I knew would tell me that the ultimate question was..."Do I want this guy flying my loved ones some day with things going wrong?" If the answer was "No" the ride was not passed. If he was as poor on line flights as checkrides maybe he needed more time in the right seat? It will be interesting to hear what the line first officers thought of him if it come out.

[Ben Brown]

Bandits and Screamin' Weenies? Sanmigmike, you are a survivor! :D

I can't remember if we did autofeather checks on the King Airs or Dash-8s. Those were the only turboprops I flew. If we did, it was first flight of the day. Sounds like that TransAsia captain might have been one of those Teflon captains who the FOs would sit there wondering how the guy got/kept his job, or maybe just had a massive brain fart when he actually had to face a for-real emergency. The one time we had an uncommanded engine shutdown in the Dash-8 was pretty anticlimactic. The autofeather did it's thing, and we just slooooooly climbed up to altitude and took care of the checklists. It was actually easier than in the simulator, because we didn't have some sadistic check airman throwing extra emergencies at us!

Ben