DASH 8 accident in PNG
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As this is a Rumour Network, a little birdie told me that there may have been an accidental selection of reverse, in flight. Prohibited in the AFM, obviously, if the rumour is true, for good reason.
My own Dash days are so far in the past that I don't remember the system but do remember the limitation.
My own Dash days are so far in the past that I don't remember the system but do remember the limitation.
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I flew the Dash for about 12 years. About 3 of those without a beta warning horn system. Around 1999(?) Bombardier introduced the beta warning horn, incorporated into the throttle triggers.
The triggers at the flight idle gate prevent the power levers from moving into discing mode (from memory, a beta mode). At the back of discing is a detent (not a gate), then you move into reverse mode.
In the background info distributed at the time, it was emphatically stated that the selection of discing in flight (inadvertent or otherwise) could lead to a complete loss of propeller control. Hence the introduction of the beta warning horn system. The prohibition in the AFM has always been so, and was re-emphasised in the bulletin.
Jabber, even at VMO with the condition levers at max, a normally functioning prop governor on the PW120 series engine will keep the prop at around 1200rpm. It's not an issue. In climb, cruise, descent and till late approach - the props are running at 900 or 1050rpm. Max isn't normally selected until late final.
Interesting..........
The triggers at the flight idle gate prevent the power levers from moving into discing mode (from memory, a beta mode). At the back of discing is a detent (not a gate), then you move into reverse mode.
In the background info distributed at the time, it was emphatically stated that the selection of discing in flight (inadvertent or otherwise) could lead to a complete loss of propeller control. Hence the introduction of the beta warning horn system. The prohibition in the AFM has always been so, and was re-emphasised in the bulletin.
Jabber, even at VMO with the condition levers at max, a normally functioning prop governor on the PW120 series engine will keep the prop at around 1200rpm. It's not an issue. In climb, cruise, descent and till late approach - the props are running at 900 or 1050rpm. Max isn't normally selected until late final.
Interesting..........
Last edited by Hugh Jarse; 12th Nov 2011 at 03:03.
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20 years ago, we operated a couple of ATR-42-300's on the 110 mile sector Nausori - Labasa. Labasa then was sealed and 1050 metres long, without fuel availability, and we used the factory provided data for the strip and terrain when planning departures to cater for a single engine climb to LSALT on departure. Temperatures precluded full passenger seating and limitations sometimes for departures in summer. It was the shortest runway in our network then.
Remember one occasion, when planning to shortfield land, with the hand on the levers ready to pull reverse as soon as the mains touched, I must have started the retarding while still a foot or two up. (With the trailing-link undercarriage we would usually get smooth touchdowns - different to the Dash even though we shared the same PW 120 engines and HS props)
Wouldn't have reached reverse, but probably was back enough to make a difference, and then we were on the ground in a more-sudden-than-normal arrival.
A hands-on learning, and theory re-inforcing moment.
A 'Won't do That Again' moment, too.
Certainly wouldn't try it at altitude.
A Dash 8 passenger may have felt something from that arrival, but the old ATR took this new captains learning curves like that in it's stride.
Remember one occasion, when planning to shortfield land, with the hand on the levers ready to pull reverse as soon as the mains touched, I must have started the retarding while still a foot or two up. (With the trailing-link undercarriage we would usually get smooth touchdowns - different to the Dash even though we shared the same PW 120 engines and HS props)
Wouldn't have reached reverse, but probably was back enough to make a difference, and then we were on the ground in a more-sudden-than-normal arrival.
A hands-on learning, and theory re-inforcing moment.
A 'Won't do That Again' moment, too.
Certainly wouldn't try it at altitude.
A Dash 8 passenger may have felt something from that arrival, but the old ATR took this new captains learning curves like that in it's stride.
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Ejector,
When you pull the triggers on a Dash and move the power levers back, you have discing mode which, at the forward limit of travel will give you quite a bit of forward thrust. At the rear limit of travel (reverse detent), you will get either zero thrust, or a very slight reverse (depending on rigging).
Discing covers a range of about 2-4" of power lever travel AFT of the flight idle stops before you hit the reverse detent.
Once you retard the power levers aft of the flight idle stops (in flight), all bets are off. It does not require the selection of reverse to lose control of propeller governing. The selection of discing alone will achieve that nicely, and long before the reverse detent is reached.
Not that I'm suggesting this is what happened in this instance.
When you pull the triggers on a Dash and move the power levers back, you have discing mode which, at the forward limit of travel will give you quite a bit of forward thrust. At the rear limit of travel (reverse detent), you will get either zero thrust, or a very slight reverse (depending on rigging).
Discing covers a range of about 2-4" of power lever travel AFT of the flight idle stops before you hit the reverse detent.
Once you retard the power levers aft of the flight idle stops (in flight), all bets are off. It does not require the selection of reverse to lose control of propeller governing. The selection of discing alone will achieve that nicely, and long before the reverse detent is reached.
Not that I'm suggesting this is what happened in this instance.
I believe a report will be years away, sometime after Bombardier, Pratt & Whitney, Hamilton Standard and APNG have stopped pointing the finger at each other.
It will definately be interesting reading when published.
It will definately be interesting reading when published.
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Wonder if it needs another event before Transport Canada mandate it?
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No casa AD for Dash8 yet
I notice the release of an AD [CF-2012-01 - Beta Warning Horn System Failure] for the Dash 8 this week by casa.
But there still has been no similar AD to [FAA AD 2005-13-35] as issued in PNG after the Dash8 accident.
On looking at the casa AD list [ http://services.casa.gov.au/airworth...ver&toc=DHC-8] nor was there in 2005 an AD for the Dash8 [or similar to or reference to FAA AD 2005-13-35]
casa as the Regulator and safety body???
casa looking after passenger safety???
But there still has been no similar AD to [FAA AD 2005-13-35] as issued in PNG after the Dash8 accident.
On looking at the casa AD list [ http://services.casa.gov.au/airworth...ver&toc=DHC-8] nor was there in 2005 an AD for the Dash8 [or similar to or reference to FAA AD 2005-13-35]
casa as the Regulator and safety body???
casa looking after passenger safety???
Last edited by Up-into-the-air; 14th Jan 2012 at 23:09. Reason: spelling again
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I don't recall hearing of any incidents of airborne beta selection in my 5 years on the DH8 ('95-'00). I wonder what's happened that Mach12 has heard of so many in recent times?
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Interestingly Bombardier released "All Operator Message No. 971" with the subject being:
In-Flight Intentional Power Lever Movement Aft of the Flight Idle Gate
In the body of the message Bombardier states:
"Bombardier hs become aware of instances where the flying pilot has intentionally moved the engine POWER Levers AFT of the FLIGHT IDLE gate in-flight". (bolding as per the message)
The message goes on to describe what happens should the above be done.
It would seem (at least on the basis of the message) that Bombardier does not see it as a design fault, but rather as an operating error.
Although, I do agree that a Beta Lockout device should be installed. At least it should stop an application aft of the flight idle gate, for whatever the reason.
BTW
I guess PPRuNe would not be much of a rumour network if you can't make rumours and not need/deliver any facts, hey Mach 12. 
In-Flight Intentional Power Lever Movement Aft of the Flight Idle Gate
In the body of the message Bombardier states:
"Bombardier hs become aware of instances where the flying pilot has intentionally moved the engine POWER Levers AFT of the FLIGHT IDLE gate in-flight". (bolding as per the message)
The message goes on to describe what happens should the above be done.
It would seem (at least on the basis of the message) that Bombardier does not see it as a design fault, but rather as an operating error.
Although, I do agree that a Beta Lockout device should be installed. At least it should stop an application aft of the flight idle gate, for whatever the reason.
BTW
I also understand that QFLink has had two similair events in the last three months, and Air Niugini has also had to replace an engine after something similiar occuring.
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I wouldn't be to quick to shoot down Mach 12 as he is right on the money and obviously well connected as well.
I know where you are coming from Mach and your 'rumor' is pretty damn good according to my source.
As the Kelpie would say 'more to follow'.
I know where you are coming from Mach and your 'rumor' is pretty damn good according to my source.
As the Kelpie would say 'more to follow'.
Negatron on the Air Niugini engine replacement.
Not in the last 2 years anyway
Beta Lockout doesn't stop the power levers going below flight idle - just extends the protection envelope of the current "beta backup" system that stops the props going into beta above flight idle, to the below flight idle regime in flight as well.
Not in the last 2 years anyway
Although, I do agree that a Beta Lockout device should be installed. At least it should stop an application aft of the flight idle gate, for whatever the reason.
If Mach12's info is indeed correct the Q I have is why the hell are these events occuring, why would anyone attempt to move a power lever below Flt Idle in flight??? 
The turboprops I flew with TPE 331's required a deliberate lifting of the locking levers to go back into beta range. It was impossible to accidentally move the levers below the Flt Idle stop without doing so.
Does the Dash 8 have a similar setup??
The turboprops I flew with TPE 331's required a deliberate lifting of the locking levers to go back into beta range. It was impossible to accidentally move the levers below the Flt Idle stop without doing so.
Does the Dash 8 have a similar setup??
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Aussie27, what you said re the TPE's is not exactly true; I was a junior F/O flying Metro 2's a few years back. One fine day as we were entering the circuit at the usual speed (Vmo minus about 5...) I was stunned when the skipper whipped the power levers past the idle stops. It was completely unintentional on his part - the whole throttle setup had become so worn over the many years in service that there was almost no pressure required to lift them over the gate.
Thankfully he reacted almost instantly and pushed them forward again, but in those couple of seconds the aircraft yawed all over the sky. Quite memorable.
I guess in hindsight that had he pulled them back gently, instead of smacking them back, it may well not have happened. But we tried it on the ground in much newer 23's and you couldn't do it even if you abused them (engineers were present).
It was the first thing I thought of when I read about the PNG crash. Those in the know might like to tell us whether power lever hardware wearing with time could cause unintentional movement aft of flight idle.
Thankfully he reacted almost instantly and pushed them forward again, but in those couple of seconds the aircraft yawed all over the sky. Quite memorable.
I guess in hindsight that had he pulled them back gently, instead of smacking them back, it may well not have happened. But we tried it on the ground in much newer 23's and you couldn't do it even if you abused them (engineers were present).
It was the first thing I thought of when I read about the PNG crash. Those in the know might like to tell us whether power lever hardware wearing with time could cause unintentional movement aft of flight idle.
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Rad alt,
Some of the Dashes I flew had in excess of 30,000 hours total time. The power levers felt no different to those of a new one. You still needed to pull the triggers up a good 15+mm to release theflight idle gate. You only had to Lift one trigger a couple of mm to get the warning horn to sound.
Clarrie, I never experienced it eitherin all those years. But then again, Qantaslink never had a single stick shaker event on the Dash (from memory) until 2008.
Now it appears to be a regular occurrence
Some of the Dashes I flew had in excess of 30,000 hours total time. The power levers felt no different to those of a new one. You still needed to pull the triggers up a good 15+mm to release theflight idle gate. You only had to Lift one trigger a couple of mm to get the warning horn to sound.
Clarrie, I never experienced it eitherin all those years. But then again, Qantaslink never had a single stick shaker event on the Dash (from memory) until 2008.
Now it appears to be a regular occurrence
Interestingly Bombardier released "All Operator Message No. 971" with the subject being:
In-Flight Intentional Power Lever Movement Aft of the Flight Idle Gate
I can not find a link, do you have it?
In-Flight Intentional Power Lever Movement Aft of the Flight Idle Gate
I can not find a link, do you have it?