DHC 6 engine query.

[skywriter6]

STANDARD OPERATING PROCEDURES MANUAL DHC-6
Section 5 - Abnormal Procedures

5.6 Engine Malfunctions
5.6.1 Fluctuating Torque and Fuel Flow
Torque fluctuation '" 1.5 psi combined with fuel flow fluctuations'" 15lbs/hr.
AFFECTED ENGINE ....................... ............... _. REDUCE POWER

I was always told that this required an engine shut down.

What causes this problem.

Please.

[ahramin]

Oil pressure problems.

[GyvAir]

May I suggest you add something in the subject line of your thread to catch the attention of the DHC-6 knowledgeable people on the site. Nobody here reads every thread; generally only the ones that look like we might relate to. Some of us might even click with a little trepidation on your current subject line.

[trey kule]

Trepidation? Are you not confident in your lifestyle choices?

But back on topic (no pun intended).
Is that SOP a company produced document? If it is, a word to the wise...this is not a place to be pasting part of a company document and then looking for advice. Some very knowledgable 6 pilots here who actually have seen a torque guage in psi. But also lots whose 6 experience is on c-fsim.

And the person responsible in the company may not take it well when you question the SOP based on extensive research here. Talk to them directly. Pose your question and your confusion and ask for an explanation. There maybe a reason for it, even if it should require a shutdown. For example in remote areas or over water no one gives a rat butt about calving an engine...they want to get home. On the other hand, doing a precautionary shutdown may save an engine..dont take the examples as gospel...they are examples only to point out that a company may have considered things and changed them...and no one here is going to know that.

In my opinion, there are some questions that are best not posed on a public forum...and the posting of a company document falls within that category.

Unless the SOP is asking you to do something intrinsically unsafe, you should follow them. What do you see as unsafe in that procedure?

[frozen solid]

Oil pressure problems.

I respectfully suspect something other than oil pressure. I think if it were oil pressure you would see fluctuations in torque and nP but not fuel flow.

If you are seeing fluctuations in torque and fuel flow but steady nP, I would be more inclined to suspect a problem in the FCU and/or high-pressure fuel pump. I'm not an AME though, so I apologize if I'm wrong.

As for shutting it down or not, the answer would depend highly on the situation, I would think. If reducing power makes the fluctuations stop, and the engine's T5 and oil pressure are steady, then shutting it down might not be indicated. If it continues to fluctuate, then maybe shutting it down is indicated.

If the fluctuations occur just after lifting off a gravel-bar in a river, two knots below VMC with a full load of rock samples, well heck I think I'd just leave the damn thing alone until we're out of ground-effect at least! Then maybe reduce power a little on that fan and see what happens.

If it just suddenly started to happen in cruise for no apparent reason, my decision-making might be a little different!

The only time I've seen a fluctuation like that is right during takeoff with max power and prop rpm. Reducing torque a little has always made it stop, and I've never shut one down.

[ahramin]

Good point. I didn't have much time when I read the original post and for some reason thought OR instead of AND. This is the first time I've come across this particular combination, maybe it's something peculiar to the -6. In any case if the procedure doesn't require a shutdown, I'd be inclined to keep it running, absent some other reason. Is that Viking guy still hanging around here, I can't remember his name?

Skywriter, as others have mentioned, you'd stand a better chance of getting a useful answer if you use a useful title.

[skywriter6]

Gentlemen thank you for your responses. I am not very proficient when it comes to presenting my ideas on a forum. It also comes as a pleasant surprise to have people with what I perceive as in-depth experience reply to my query.

The mention of the legal side to what ever I post on the forum is a good reminder to be wary of what one puts in print. The quote that I made comes from a generic FOM and does not identify any particular company.

I was curious to find the engineering logic behind the particular procedure as it relates to an incident that I experienced.

As I have already put in the subject heading is there any way to modify it to a more appropriate name?

Again, with thanks.

[ahramin]

You can edit the title by editing your first post. Button at the bottom right of the post.

As for your experience, what was the outcome? Did you shut down the engine? What did maintenance diagnose as the engine problem afterwards?

[pelmet]

STANDARD OPERATING PROCEDURES MANUAL DHC-6
Section 5 - Abnormal Procedures

5.6 Engine Malfunctions
5.6.1 Fluctuating Torque and Fuel Flow
Torque fluctuation '" 1.5 psi combined with fuel flow fluctuations'" 15lbs/hr.
AFFECTED ENGINE ....................... ............... _. REDUCE POWER

I was always told that this required an engine shut down.

What causes this problem.

I wouldn't worry about what you posted. You won't get sued.

I can only guess as to what the problem might be but I suspect that they are related. Something is causing a fluctuation in fuel flow, perhaps a fuel pump problem. The result of the fluctuating fuel flow is fluctuating torque(power). If so, it would not be a DHC-6 only potential event but possible on any PT-6. And perhaps any engine depending on the fault.

With a partial blockage intermittently restricting fuel flow, you may not be able to get higher power settings but will still be able to get smooth lower power settings.