Airlines PNG Dash 8 fatal crash in PNG
 

PNG crash
 

From the AvHerald:
Crash: PNG DH8A near Madang on Oct 13th 2011, impacted terrain

News report from Friday edition of 'The Age' newspaper gives a few more details:

An Australian pilot has survived a plane crash in Papua New Guinea's north coast in which 28 people are believed to have died.

Only four people are believed to have survived the crash in dense forest, near the mouth of the Gogol River, about 20 kilometres south of the resort centre of Madang.

Airlines PNG Dash 8 plane, which was carrying 32 people, was on a flight from Lae, PNG's second largest city, to Madang, when it crashed about 5pm (6pm AEDT) yesterday.

"All I can tell you is there have been reports of survivors and reports there have been fatalities," the PNG Accident Investigation Commission's (AIC) spokesman, Sid O'Toole, told AAP. He said it wasn't clear how many survivors there were.

The 64-year-old Australian pilot, from Queensland, has decades of experience flying in PNG. The other survivor was a New Zealand pilot, a Department of Foreign Affairs and Trade (DFAT) spokeswoman said.

She said there were no indications at this stage that Australians were among those who died, adding that the Australian High Commission in Port Moresby has been liaising with Airlines PNG and local authorities.

Consular officials would be travelling to Madang today, she added.

Airlines PNG grounds its fleet

Airlines PNG confirmed one of its Dash 8 aircraft has crashed near Madang and grounded its fleet of 12 aircraft until further notice.

A spokesman for the Australian Transport Safety Bureau (ATSB), Australia's national transport safety investigator, said they had not been contacted to assist in investigating the crash.

The ATSB has previously assisted the AIC in crash investigations.

FF 'Headlines' Experienced skipper this time. Sounds like a challenging place to fly, with a large possibility of being a long way from a road if you do come down.

From the Post-Courier

Post-Courier Online

Also mentioned by a Radio Australia PNG correspondent in an interview this morning

Fire onboard and both engines out? That sounds a bit strange.

The weather in the area has been reported as being very bad? The pictures of the burnt out plane seems to suggest that the impact was severe (maybe CFIT?).

Skipskatta I am not sure what pictures you refer to. Do you have a link? There was a post in Planetalking which indicated that News Ltd online had erroneously posted a picture of a burnt out wreck that was in fact of another accident.
Here is the Planetalking link: News.com.au cheats on PNG crash photo | Plane Talking

There are photos on the ABC web site, linked to the thread in Dunnunda Forum.

More than meets the eye still to come ....... Maybe
 

Another rumor getting round is that the crew were doing a DME arrival in bad weather, got above VMO, had a propellor over speed, destroyed the engine (fire) and all over Red Rover! :rolleyes:

No idea how this rumor got its legs but sounds feasible ......... Maybe! :eek:

you don't have many options in PNG or Irian Jaya if something goes wrong - best to aim for the sea or the river if you have a chance

Sad but looks like being true!
 

Just received a bit of info from a contact in PNG who says the above rumor re prop overspeed on an out of control DME arrival has been "confirmed" by other crew(s) of the airline involved.

Still no guarantee of this being 110% correct but looking like is was the culprit!

Abingdon
 

Local newspaper reports observers on ground saying that aircraft passed low overhead and was 'dripping fuel' which was burning in the trees.

Also that the emergency doors were open as the plane went towards the sea.

It seems that the fuel problem certainly contributed to the flash fire which happened when the aircraft grounded. One passenger escaped 'through a crack in the fuselage' with severe burns.

Overspeed?
 

Sorry, not the original source....
OVER-REVVED PROPELLERS FOUND IN PNG CRASH PROBE - Nov. 7, 2011

Any twoter drivers out there to explain to us how you could overev both Props 60% ?? Major pilot Error ? I really would like to know. Thanks

Why do you want to hear from Twotter pilots when it was a Dash 8??

OOPS:8, My Bad ! I was thinking about another crash In Papua, that one was a DHC-6.
OK Any DASH 8 Drivers ?

Overspeed of 60% would be almost 2000rpm. Major failure as at this Np the engine would be decelerating to try to limit the Np. Never heard of an overspeed this great - and on both props? Suggest we await further reports as this sounds unlikely.


EDIT: Take off Np 1200

The fact that it happened on both sides to me is an indication that the probability of a direct mechnaical failure of the propeller control as root cause might not be so terribly high.

One thing that crossed my mind:
Could it be that they accidentally entered too steep a dive and tried to use the propellers as speed brakes ?
Would be interesting to know the propeller pitch setting at the time.

This might have absolutely no bearing on this accident, but Bombardier sent out a FOSL yesterday advising against moving the power levers below Flight Idle (i.e.into Discing) in flight. One possible - or should I say likely - result would be a prop overspeed.
Interesting timing of the FOSL.

I've never flown a Dash 8, but I have fair experience in DHC-6 and Caravan. On both those types, rapidly moving the propeller levers from coarse pitch to fine pitch can get you close to an overspeed, though 60% over seems very hard to imagine. The key is that power lever movement alone should not really result in significant overspeed, as the governor should govern. I speculate that overspeed risk is cause by mishandling the propeller levers.

What would happen if the propeller controls were moved toward feather in error, and then rapidly moved back to fine to correct things, while lots of power was applied? Could the governor change the blade angle quickly enough to prevent an overspeed?

Though I respect what Bombardier would instruct about the operation of the Dash 8, I would speculate that if a pilot selected power below flight idle in flight, that would initially result in a lower propeller speed, as there would not be much engine power commanded to turn the discing propellers. The discing propellers would have some of the blade in reverse pitch, thus large torque required to turn the prop.

Just me thinking, I have no knowledge of the accident....

In discing the blade angle decreases from 17.5 to a minimum of 1.5 degrees. However, there is no significant change in Tq.

The Bombardier AOM states:
"When the POWER Levers are moved aft of the FLIGHT IDLE gate in-flight, the Propeller Governor, Propeller Overspeed Governor and the BETA Backup logic protection are all inhibited
and Propeller speed control is no longer available. In this condition the propeller(s) would be
driven uncontrollably toward a Reverse pitch condition resulting in an overspeeding propeller
and substantial engine damage leading to possible engine failure."

However, if this was the case, I suspect the plane would come straight down. I've never heard of a prop overspeed of 60% due to Condition Lever(s) being moved too rapidly and I suspect if such a thing did occur, the manufacturer would send out a crew advisory.

Preliminary report can be downloaded here:

http://www.atsb.gov.au/media/3482404...20report_1.pdf

It seems that at least one prop (From one of the the preliminary report Photos) is feathered, so how can you get 60% over speed on a feathered prop ? I'm not a -8 Driver but it just puzzles me... 28 deaths, I really want to find out what happened !

Maybe they just fearthered after the engines failed (which did happen according to this report) due to the overspeed?

Here is a clue:

http://www.airdisaster.com/reports/ntsb/AAR94-06.pdf

Not saying this is what happened here, but way back in '94 a Saab 340, for some reason (read the report) ended up with both engines in reverse range in flight. Both props ran away; one going to 142%, the other to 158%. Both engines flamed out, but they were able to get the engines running again.

Didn't help, though. In a free turbine engine there is no direct mechanical connection between the compressor (gas generator) section and the power section (which drives the propeller). While the overspeed event did not damage the compressor sections, it destroyed the power turbines in both engines. So even though both were successfully restarted, with the power turbine blown out the back like a mouthful of sunflower seed husks, there was no way to deliver power to the propellers.

Unlike the accident in PNG, there were no serious injuries among the pax and crew of the Saab. And again, I am not saying this is what happened. but there are similarities between the preliminary report on the PNG crash and the NTSB report referenced above.

Possibly just feathered the prop after the overspeed causing a loss of control

The HS prop on any PW 100 series engine will be driven to feather after loss of oil pressure by springs after any normal, or abnormal shutdown.

There is no feathering springs in the prop hubs. Piston inside with engine oil on both sides, the system is controlled by a hydraulic (engine oil) propeller control unit (PCU), oil is ported in and out of the prop via a transfer tube.

Very good clue, I'd say.

No it won't. What You wrote is valid for PT6. PW100s are radically different.

I'm not sure that I understand... what caused the loss of control? Overspeed or feathering? What makes you think that loss of control was involved?

Bobnspike, The AE accident relates to a different engine type and systems. I'm not sure this is what happened here. In that case the Capt may have selected reverse beta, just like the Twin Otter crash in St Barts.
French BEA report (french) here: http://aviation-safety.net/go.php?ht...f-es010324.pdf

BEA english report: http://www.bea.aero/docspa/2001/f-es...-es010324a.pdf
ASN page : ASN Aircraft accident de Havilland Canada DHC-6 Twin Otter 300 F-OGES Saint-Barthlmy

If not approved, placing power levers below flight idle on a turboprop can be very dangerous. The F50 has a different propeller(Dowty) for its PW100 engine but as this accident report shows, the three second time period that it was done on this aircraft was fatal. Do a 360(or some other safe manouver) if you are too high.

http://www.skybrary.aero/bookshelf/books/677.pdf

From the preliminary report, they were at 13,000 ft with 24 miles to run before Madang. This seems to be quite high. At what altitude should you be at 24 miles for a normal descent profile (assuming already clear of terrain)?

FL80 or thereabouts ... depending on the platform altitude /entry point for the procedure ... and of course terrain in that sector. The above assumes terrain is not an issue.

The CT-7's and PW-100's both have a free power turbine. Additionally, in both engines, coming over the gates into beta or reverse disables the propeller overspeed protection. The preliminary report states that according to the FDR on the Dash, the props went to 160%, which implies the overspeed protection was not operating.

Even with the Dash's good descent performance, 13000 at 24 miles is way high. I am not familiar with the terrain in PNG, but discounting terrain issues, a standard descent ratio is about 3:1, making the correct altitude at 24 NM 7200 ft.

If the propellers were placed into DISC (retarded below the flight idle indent) it is possible the aerodynamic forces of a rapid descent could cause the propellers to overspeed. In normal flight configuration the DHC-8 has an automatic safety feature that will drive the propeller to coarse pitch if it exceeds 1208 PRPM. This is driven by engine oil pressure pushing on either side of a piston and tachometer. In the oil is lost the propeller will lock its pitch.

Bombardier already has issued warnings about reducing the power levers below flight idle and in US air carriers a placard is mandatory stating this prohibition.

As a manager at another DHC-8 operator in the Pacific I will be interested in seeing how this investigation plays out.

Actually Island-Flyer, the Bombardier AOM says that in flight selection below Flight Idle the "props would be driven uncontrollably to a reverse pitch condition"
This would probably overspeed the power turbine resulting in failure. If the crew in such a situation was lucky enough to get the props out of reverse, the only option left - with the power turbine failed - would be to feather the prop(s)

A standard 3x profile on a Lae-Madang track will not work, bcoz of the high terrain you have to clear and Madang is just across the bay after you've cross those big rocks.
Just a quick question, does the Dash8 do overspeed test on there run ups like they do in the Otter? I've only seen Dash do Auto FX test on there run ups?

In response to the question on the overspeed governor on the DHC-8, the overspeed governor test is now an engineering fuction and is not carried out by the flight crews on the normal first flight of the day checks.
Slight thread drift here, but similarly the T-handles are not pulled to test the fuel shut-off valves, we only test the loops for continuity, and the fire bells and fire detect lights in our company. This has also been relegated to an engineering fuction.

I figured terrain would be an issue.

13000 feet AGL at 24 NM is 540 ft/NM. That's pretty steep. At 180 knots groundspeed that would require just over 1600 ft/min descent rate. At 240 it would require just under 2200. Distance required to slow and configure would further steepen the required descent angle.

Perhaps someone with experience in the Dash can let us know whether those descent rates are practical.