Bell 412 unusual engine problem
 

Hello there. Just picking up our Bell 412 from contractor following a 600 hr inspection. The #1 engine was taken out because it was reported that engine stalling / popping was occurring. Some of the compressor blades were changed out and the engine got a new combustion liner.

We started doing our post 600 hr ground runs and noticed that the #1 engine was still popping since repair! It seemed to pop like a machine gun going off between 61% to 70% Ng (N1) on a normal wind up of the #1 engine throttle. If the pilot wound up the throttle quickly like if we were doing an accel check, it wouldn't pop. Also if he brought up the throttle slowly, it wouldn't happen. It would only happen during a "normal" wind up of the throttle and it didn't matter if the governor was in auto or manual.

So far we have swapped fuel clusters from our #2 side since it was proven serviceable during ground runs, changed bleed valves, fuel surge accumulator, fuel dump valve, checked P3 filter, checked for air leaks, changed the setting on the accel dome 3 clicks in either direction and still has the symptoms!

So any input on the cause of this problem would be very helpful because i think we've changed about everything that we can before we change the engine!

Thanks.

Check the inlet system?

How olds (hrs) the Engine and was it popping before the inspection? if not what was done to the engine during the check? has it had an HSI recently where the CT vane ring was changed?

Well, oddly enough, before we changed fuel clusters it wouldn't pop with the intake cowling off!! I guess P&W do say that these birds do have a problem with the intake system with the 3D engines.

Anyways, got word back from the P&W guys and our Bell Rep. They have concluded that our "surge margin" in the engine was too close and it was running too rich. This was evident because we pulled one fuel nozzle and it was covered in black powdery carbon!

So the decision was to pull the engine and replace it. I'm just glad that i'm not forking the bill for this mess. Thanks for the input.

Pleasure dear Chap, give my regards to your Pratt rep (Rob Pobjoy?)
Stacey

Errrmmm... The Canadian Defence Forces? (CH-148 Griffon).

CH 148 is the Cyclone/S92

CH 146 is the Griffon/412

and.... Surete du Quebec (Quebec Provincial Police), NRC (National Research Council, fly by wire, flying simulator), Allied Wings (commercial, de-militarized CH-146 flying as trainers)...

Bell 412 Maintenance /year 700 fh.
 

Hi there,
Is there any info out there regarding how much maintenance a Bell 412 need´s on a yearly basics for doing around 700 f/h .
we are talking about a Full SAR 4 Axis EP Heli.

My figures are so far 70 Day´s(ground time) schedule maintenance , and normally around 14-35 days (groundtime)unschedule maintanance.

Pls advise if you have any Idea where such info is avali!

Tump´s rule if you need one rolling have 3 on the line right ;)

412 Helicopter Maintenance Tasks
 

We're government 412 helicopter operator in Turkey. We perform all scheduled maintenance requirements iaw tasks in MM chapter 05. Tasks in MM is not well defined and are mostly full of general wordings. ın order to optimize maintenance performances we're looking for job cards for scheduled maintenance requişrements of 412 helicopters?

Has somebody heard, used or seen well detailed maintenance tasks (job cards) to apply 300/600 Hrs and lower and higer level scheduled maintenance requirements of Bell 412 helicopters?

Where ? How can I reach / buy / see ?

The aircraft is a B412SP with PT6T-3B engines. When making a power change engine 1 hunts high and low (torque, ITT and N1) about four times before settling down; engine 2 settles down after only one cycle.

Is there a prescribed minimum (either in seconds or number of cycles) before which the engine should be in a stable state? If so, where can I find it? I’ve looked through both the B412 and PT6T Maintenance Manuals and failed to find any hard data.

Thanks for any pointers.

Mmmmm ...

Not quite sure what you mean by 'cycle' ...BUT .... engines should be stable (within reason) during pwr changes at all times ....

Need to know a bit about the TSN/TSOH of the engines and AFCU/Gov components to really try to diagnose this .... BUT... it may be that the fault is actually with the No.2 engine AFCU/Gov as it may be the 'slow' (sticky) operator which is making the No1 do all the work .... need to see what is happening with the Nr while all this is going on ....

One method to determine which engine is operating correctly is to set (say) Eng No1 into MANUAL Gov and set it @20% Tq lower than No2 and see if with (gentle) pwr changes the other engine responds normally then vice versa etc.

If you are operating in a very dusty envoironment get your engineers to look at the TCU bleeds for blockages etc ...

Cheers ... Good luck :}

Rainbrave.
Check your PM's.

Frank
Pleased you answered before I did!!
Stace

Thanks spinwing,

My question was prompted by the following observations: with the aircraft on the ground, well ballasted, one throttle at idle and the other fully open, rapidly raise the collective to 35-40% engine torque, and observe how long it takes for the parameters (NR, torque, N1, ITT) to settle down at the new setting. Initially the NR will droop somewhat, then surge higher than before, drop again, etc., before settling down. The #1 engine took about 4 times as long (both in seconds and in number of high-low surges) to stabilize as the #2 engine; however, it does eventually stabilize.

What I was hoping for is a hard number (either seconds or number of surges or “cycles”) before which the engine must stabilize following a power change. At the moment we’re not sure if this is a fault that needs to be rectified, or just not as good as the other engine but acceptable.

I have flown a few B412s whose engines just wouldn’t stop hunting, from +/- 3% N1 at flat pitch to +/- 1% in cruise even in dead calm air, and they all required an AFCU change on one engine to rectify that problem.

Mmmm ...

Buitenzorg.....


Well there is your answer .... No.1 AFCU or Gov. FKD! (this is a technical term for 'not working correctly') .... Engineering dept. will have M&O requirements to hand?

In the organisation (?) I work for the requirement for us to carry out slinging task with loads that put the a/c at MTOWA mean we have no margin for sloppy AFCU/Governor performance .... so they are kept very well looked after.


StacyS of this forum will have the detail you require at his finger tips ..... perhaps :}

Cheers ;)

yes , lots of fingertips, but on holiday in Abu Dhabi till 2nd Jan?!!!!
S

Mmmm ....


ROFL ..... AND I'm on holiday AWAY from Abu Dhabi .... Have fun! :E


:D

If you've warmed up the engines, then icing in the air lines shouldn't be a problem.
We had an iced up air line after a blizzard many years ago. -The engine went from idle to 117% N2 in less than three seconds when the throttle was cracked from idle. Ripped the tail rotor drive shaft into several sections.

when will P&W make a digital fuel control for the 212 / 412? The world waits!

Aren't the latest "Super EP" equipped with a EEC similar to the 119s and 139s?
I believe few of those were built for the Saudi Kingdom and came with a full glass cockpit.