Mis-set Cruise power

[pelmet]

Seems odd to get an overspeed when there was an underspeed. Or could that have been while trying to correct the underspeed......


C-GJZH, a de Havilland DHC-8-402 aircraft operated by Jazz Aviation LP, was conducting flight
JZA7999 from Moncton/Romeo LeBlanc Intl (CYQM), NB to Montréal/Trudeau Intl (CYUL), QC.
While enroute at approximately 25 nm northeast of Fredericton Intl (CYFC), NB, the flight crew was
setting cruise power and inadvertently decreased the propeller condition levers briefly below the
MIN/850 position. The crew then observed a number 1 propeller overspeed indication, and a #1
PEC annunciation (number 1 propeller electronic control malfunction). The crew then followed the
quick reference handbook (QRH) instructions for PROPELLER OVERSPEED, and the number 1
propeller feathered. The crew then actioned the QRH instructions for ENGINE
FAILURE/FIRE/SHUTDOWN, and shut down the number 1 engine (Pratt & Whitney Canada
PW150A). The crew declared an emergency (MAYDAY) and elected to divert to CYFC where the
aircraft made a single-engine landing without further incident. There were no injuries.
Company maintenance conducted overspeed governor checks, which tested serviceable. It was
determined that the inadvertent decrease of the condition levers below the MIN/850 position
caused the Automatic Underspeed Protection Circuit to activate for the number 1 propeller.

[cdnavater]

Wow, thankfully they didn’t get the same fault on both sides
I put on my instructor hat, I wonder if they actioned the overspeed QRH with an underspeed annunciation, wouldn’t be the first time a similar message caused actioning of the wrong checklist.

[yhz41]

There is a system in the Q400 engine that will force the prop into an overspeed if it starts as an underspeed situation. It's been quite awhile since I've flown the Q but I believe that when you get that PEC light that's what's happening.

[airway]

In the Q400 normal take off prop RPM is 1020, climb is 900, and cruise is 850. After you level off at cruise, generally you pull the condition levers back from 900 to 850. Below 850 is feather. If for some reason one prop gets into a overspeed condition, the procedure is to feather it and shut it down.

From what I understand, If you inadvertently pull both condition levers below 850 in flight (they need to be lifted over a gate), both props will start to feather. Realizing what you have just done, you will probably jam the prop levers back up to 1020. This creates an overspeed condition in both props that can not be corrected in flight, and you need to land ASAP.

In this case they may have only got one of the levers below 850?




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[flyer 1492]

There's the next loft training session..

[fish4life]

In the Q400 normal take off prop RPM is 1020, climb is 900, and cruise is 850. After you level off at cruise, generally you pull the condition levers back from 900 to 850. Below 850 is feather. If for some reason one prop gets into a overspeed condition, the procedure is to feather it and shut it down.

From what I understand, If you inadvertently pull both condition levers below 850 in flight (they need to be lifted over a gate), both props will start to feather. Realizing what you have just done, you will probably jam the prop levers back up to 1020. This creates an overspeed condition in both props that can not be corrected in flight, and you need to land ASAP.

In this case they may have only got one of the levers below 850?




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You don’t need to jam them back forward the PEC automatically drives the prop into over speed to keep you from essentially FX both

[tbayav8er]

Some people here are almost on the right track. There is a system on the Q400 where if both condition levers are brought below the 850 RPM (cruise) gate, the PEC's (propeller electronic control) will automatically put the props into an overspeed condition. This is to prevent the props from self-destructing themselves in cruise if you accidentally select the prop levers to "start/feather" while you're at 65% torque in cruise.

Edit to add: Sorry, just noticed fish4life just said the same thing.

[pelmet]

Some people here are almost on the right track. There is a system on the Q400 where if both condition levers are brought below the 850 RPM (cruise) gate, the PEC's (propeller electronic control) will automatically put the props into an overspeed condition. This is to prevent the props from self-destructing themselves in cruise if you accidentally select the prop levers to "start/feather" while you're at 65% torque in cruise.

Edit to add: Sorry, just noticed fish4life just said the same thing.

Thanks,

So at low power(for shut down or after bring a power lever to idle in flight for shutdown), there will be no damage when selecting feather but there will be at high power.

Is that correct?

[tbayav8er]

Yes. When parking the airplane, you put the condition levers to "start feather" before shutting the engines down, as well as when starting the engines. When in flight, the props would self destruct under such high torque loads, so the airplane won't allow the props to actually go into feather, at least beyond a certain power lever angle. If you have to do an in-flight shutdown, the QRC has you first bring the power lever to flight idle, which then allows the prop to be feathered. When flying along in cruise though, if you were to accidentally pull the condition levers back to feather, the PEC's won't allow it, and will instead put both props slightly beyond the overspeed limit (1020 rpm). I think they end up at 1080 RPM or something like that.

[Meatservo]

One would think a better design would be a "PEC" that positions the props to a slightly less than overspeed condition. But what do I know.

[pelmet]

Another mis-set power incident....

C-GLQE, a Porter Airlines Inc. De Havilland DHC-8-400 was conducting flight POE2942 from
Boston/General Edward Lawrence Logan Intl. (KBOS) to Billy Bishop Toronto City (CYTZ), ON.
During initial climb, Flight crew declared an emergency (Pan Pan) with ATC due #2 engine
indicated more RPM than commanded through 5000' feet. The Flight crew elected to do a
precautionary shutdown of the #2 engine and diverted to KBOS. Flight landed in KBOS without
further incident. There were no injuries reported.
The engine data was downloaded and it was found that the #2 engine power lever exceeded the
power detent during climb out. The Propeller Electronic Controller (PEC) logic assumes that the
pilot needs full emergency power and correctly drove #2 propeller to 1020 RPM even though the
propeller condition lever remained at 900 RPM. Aircraft was returned to service with no fault
found.

[Canoehead]

Yes. When parking the airplane, you put the condition levers to "start feather" before shutting the engines down, as well as when starting the engines. When in flight, the props would self destruct under such high torque loads, so the airplane won't allow the props to actually go into feather, at least beyond a certain power lever angle. If you have to do an in-flight shutdown, the QRC has you first bring the power lever to flight idle, which then allows the prop to be feathered. When flying along in cruise though, if you were to accidentally pull the condition levers back to feather, the PEC's won't allow it, and will instead put both props slightly beyond the overspeed limit (1020 rpm). I think they end up at 1080 RPM or something like that.

Sort of true. Props won't self destruct; during an unscheduled feather (Autofeather armed) FADEC will limit to 106% torque and the blades will turn at the corresponding RPM. I'm sure there's an expensive prop removal after that (although maybe that's what you meant by self destruct?).

AUPC only works when Condition Levers are above Start/Feather (amongst other arming requirements).

It's always possible to feather the props manually by setting them to Start/Feather regardless of power lever angle. If you do it inadvertently, and assuming the other AUPC arming logic is met, once you bring the Condition Levers above Start/Feather (such as one would after thinking "holy S$1t what did I just do?!) the AUPC will intervene and the prop(s) are given the drive-fine signal which, if at higher speed such as cruise, will appear as an overspeed of up to 1060 RPM.

In the case of the Jazz flight, only one prop met the conditions for the AUPC to intervene for whatever reason, otherwise they would have had a double overspeed scenario [then what do you do ? ]

In the case of Porter, setting the Power Lever above the rating detent commands Max RPM regardless of selected RPM (probably 900 in their case). The crew just had to set the Condition Lever(s) to Max then they could have reset to desired RPM. No need to shut the engine down.

Both of these cases were pilot induced resulting in lots of paperwork and likely some sort of followup training, but thankfully no injuries or damage excluding some egos.

[EPR]

Sign of the times, with many more to come!

[fliter]

One would think a better design would be a "PEC" that positions the props to a slightly less than overspeed condition. But what do I know.

The way it was explained to me it's that AUPC is designed not just for pilot error but for an actual system malfunction. If something weird like feathering of a healthy engine in flight begins to occur, the aircraft just assumes that something has malfunctioned (e.g., condition lever sensors, PEC circuitry itself or who knows what else) and just removes the normal means on propeller control, assuming its broken. Then the job of handling prop speed falls to the back-up overspeed governer, which only kicks in once the prop is actually overspeeding, and which is designed to keep the prop in a slight overspeed (1060 as opposed to 1020 rpm) because you don't want this back-up system interfering with prop operation under normal conditions.

[Meatservo]

One would think a better design would be a "PEC" that positions the props to a slightly less than overspeed condition. But what do I know.

The way it was explained to me it's that AUPC is designed not just for pilot error but for an actual system malfunction. If something weird like feathering of a healthy engine in flight begins to occur, the aircraft just assumes that something has malfunctioned (e.g., condition lever sensors, PEC circuitry itself or who knows what else) and just removes the normal means on propeller control, assuming its broken. Then the job of handling prop speed falls to the back-up overspeed governer, which only kicks in once the prop is actually overspeeding, and which is designed to keep the prop in a slight overspeed (1060 as opposed to 1020 rpm) because you don't want this back-up system interfering with prop operation under normal conditions.

Ah, thanks for the explanation. That makes sense.

[The Champ]

Sounds to me like some rookies need to get their heads out of their as*es. Whenever you’re touching the engine controls when you’re in the sky maybe think to yourselves, “ OK. I’d better be careful here because if I do this wrong I could damage this multi million dollar machine and kill everyone on it.”

[airway]

So I was thinking with the Jazz flight, only one propeller over speed, so why not shut it down and then restart it? Would that clear the over speed condition?

If you were close to an airport and about to land, I probably would just land with it over speed anyway.

[digits_]

Sounds to me like some rookies need to get their heads out of their as*es. Whenever you’re touching the engine controls when you’re in the sky maybe think to yourselves, “ OK. I’d better be careful here because if I do this wrong I could damage this multi million dollar machine and kill everyone on it.”

Lol. You're quite dramatic...

[The Champ]

LIVES ARE AT STAKE!!!

[tango308]

Sounds to me like some rookies need to get their heads out of their as*es. Whenever you’re touching the engine controls when you’re in the sky maybe think to yourselves, “ OK. I’d better be careful here because if I do this wrong I could damage this multi million dollar machine and kill everyone on it.”

Jazz SOPs is to for the PF to set cruise power with the open palm of the hand. Just carefully lift those CLs past the climb detent, slide them back with open palm to the cruise gate, 100% avoid yourself the embarrassment of an overspeed. Dont be the idiot that moves back the CL with a tight fist

[fliter]

Jazz SOPs is to for the PF to set cruise power with the open palm of the hand. Just carefully lift those CLs past the climb detent, slide them back with open palm to the cruise gate, 100% avoid yourself the embarrassment of an overspeed. Dont be the idiot that moves back the CL with a tight fist

You don't need to lift them over the climb detent. You can move between all in-flight positions with an open palm, precisely to avoid accidents like the one described.