rainbrave

I wonder the maintenance programme of Military 412 helicopters.

Is there any Bell 412 Military operator who is able to explain maintenance programme of military 412 helicopters?

Is there mandatory preflight inspection performed by technicians apart from flight crew performing before each flight?

What is daily inspection consept and validaty?

Is any airframe overhaul (or other type of inspections) scheduled beyond 3000hrs/5year inspections?

Does any military format MM exist for 412 helicopters?

What about maintenance test flight requirements? Do -6CF and -6CL manuals exist for 412 helicopters?

Any help/information will be higly appriciated...

Dreviator

A tech rep from Bell Helicopter came and looked at the aircraft. After several checks and isolating the Main drive shaft Vibration. It was realized that the rotor brake disc was warped. That has gotten rid of the high frequency vibration throughout the airframe. The aircraft has subsequently smoothed out a bit. I only experience a slight lateral vibration in the 60 kts letdown.

The Sultan

Deviator

I have seen the reported rotor problems when certain RT&B equipment is being used. What were you using Chadwick, RADS, Bell's HVM?

In most cases it is just a lead-lag damper.

Also unless you have 20 year old blades all are interchangable and not as reported in pairs unless they get cocked up during refurb.

The Sultan

Encyclo

The answer: NO

All Bell 412s, what ever the paint scheme, have the same inspection requirements. Some customers have elected to slightly modify their schedule because of past incidents/events. And yes, the highest interval is the 5 year/3000 Hr inspection.

m708

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.

Shawn Coyle

Check the inlet system?

stacey_s

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?

m708

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.

stacey_s

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

sandyhelmet

Who the heck is running 412s in Canada anyways?

Buitenzorg

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

carholme

CH 148 is the Cyclone/S92

CH 146 is the Griffon/412

Encyclo

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)...