Nice Video - and it sure has sparked some discussion here regarding procedures. Some have been addressed and some are misunderstood. I'll try to shed a bit of light on it as much as I can. As with anything technical, the FM is the final authority. 1). Why are the throttles moved before start? Throttles are moved full open and then closed to check for travel and "feel". They could be frozen, the frictions could be too tight, or travel otherwise restricted. All of this is better found out before the start sequence. 2). What's the deal with the throttle travel DURING start? As someone else said, there's about 3 ways to start a 412 - and the most common is as per the video. - Engage Starter - At 12% N1 throttle full open, then back to Idle Stop, but not holding pressure against it. - Engage Idle Stop and move throttle slightly past towards the Cut Off side. This is in case there is a sudden electrical failure and the engine start needs to be aborted (hot start, fire etc). - Starter OFF at 55% N1 - Stabilize at Idle (61% N1) and carry on with the rest. 3). Doesn't moving the throttles full open during the start sequence increase the chances for a hot-start? On some helicopters, yes - 100%...but not so much on a 412. Probably not a good idea to leave the throttle full open, but a momentary placement doesn't do any harm. The fuel control units (FCU's) operate on the premise of PFM (Pure F*&king Magic), and there is A LOT of magic that happens there. Basically fuel is metered by a complex relationship of air pressure (P3 air and PX-PY air), N1 speed, and atmospheric pressure. For the nerds, as per the training manual: "With airframe electrical power applied, engine fuel supply systems energized, and the selected engine’s throttle closed, the pilot engages the starter. Energizing the starter activates ignition, initiates compressor rotation, and drives the engine fuel pump through the N1 accessory section gearing. As the compressor spools up, compressed air is supplied to the combustor section, compressor discharge pressure (P3) is sent to the AFCU, and fuel pressure increases within the FCU. Fuel, however, is prevented from going to the combustor section by the shutoff valve in the MFCU, which is held closed by the throttle. The N1 governor begins to establish a PX-PY pressure to position the auto-metering valve to the correct opening to provide light-off fuel scheduling. At 12 % N1 rpm, with both ignition and compressed air available in the combustor and the auto-metering valve positioned to the start- flow setting by PX-PY air, the throttle is opened to the flight-idle position. This opens the shutoff valve in the MFCU and allows metered fuel from the AFCU to pass through the MFCU and on out to the flow divider. At 12 % N1, fuel pressure has increased to the point where it has sufficient force to open the primary valve of the flow divider, and fuel flows through the primary manifold to the seven primary fuel nozzles in the combustor. Light-off should occur within 15 seconds of opening the throttle to flight idle and is indicated by increasing ITT and continued acceleration of the N1 rpm, which should continue until flight-idle rpm is achieved. Acceleration fuel is controlled by the increasing P3 air pressure, which causes the PX-PY bellows to move the auto-metering valve. Flight-idle fuel flow is preset to provide 61 ± 1% N1 rpm. N2 governing has not yet begun. With the engine started, N1 exhaust gases impinge on the N2 turbine wheel, causing it to rotate. N2 rotation activates the associated Sprague clutch in the C-box and begins to drive the main rotor. This is indicated by the N2 needle “marrying” with the NR needle and both beginning to accelerate. With N1 rpm stabilized at 61%, N2/NR Will increase to approximately 65%, depending upon atmospheric conditions. 4). The collective should NOT be manually pulled up on shutdown - but as mentioned previously, it is simply pulled up slowly after shut down by the elastomerics in the rotor head. Anyway, long-winded comment that likely no one will ever read...but in case someone does, maybe they learned something.

@MrBadApple999

3 жыл бұрын

I read it, and thanks a lot.

Basically you are 100% right! But sometimes, after decades and thousands of flight hours pilots and engineers discover things that work better for the helicopter than what the FLM says. For example the oil level in the 412's combining gearbox: If you do your exterior-check and come to the C-Box, you want to fill up oil until the green marking because it seems there is no more oil left. But every drop you fill up on top of "barely nothing", the C-Box just pushes out again and everything is dirty!

I fly Bell-412 as well. So in our company we start the engines on principle of which date is on each day; even and odd days. That is because it is believed that it is good for engines that they have the same amount of starting cycles. And why is collective up before startup and pushed down during startup?....its because of hydraulics and the structure of the head of rotor (bearings, dampers,...) they become hard when the rotor is not turning. And it is wrong, that you pull the collective druring shutdown procedure. You leave it away and collective comes up by itself. You can also start the engines if you leave the throttle open to some position bertween flight idle and half open throttle. Then you just add or remove some throttle in respect of rising/falling ITT. Some instructors on Flight Safety International say that there are 3 different ways of starting the Bell-412, and niether is wrong or right ;) But I stick to that, which is described in RFM.

Thanks for the explanations. I've never flown 412 yet, but out of my experience in other helicopters -mainly AS332- I think you should stick to procedures. In every helicopter I've flown procedures tell you to move throttle from close to open and then to close but always BEFORE start. If during START you open throttle to full even for a short time, there's a lot of fuel entering the combustion chamber and the start up will be hotter, wich is not good.

Hi Christian, yes you are right. It's a very common procedure on twin-engine helicopters.

Nice ❤

Because last time #1 was started first. I'm not sure if it's in the FLM but the engines should be started in alternating sequence, basically on every twin-engine helicopter!

Huh, I never thought it mattered. Interesting!

Why start engine #2 first? Also, thanks for uploading, love the video!

@user-nb6kr9kq7j

3 жыл бұрын

1day is 1engine 2day 2engine again 3day 1engine

Ha dato starter al motore 1 poi l'ha tolto.......cosa si era dimenticato?

Sorry. I don't understand why you move the ENG 2 throttle from closed to full open and then to closed AFTER putting START SWITCH to ENG 2 position (0:09). And is it normal in Bell 412 to begin START UP with collective up? Thank you. I'm a helicopter pilot preparing for Bell 412 Type Rating.

Starting with the batteries turned off? Braver man than I am lol

It looks like you actuate the starter for engine no. 1 twice. Why is that?

Do you follow the starting procedures?

of course...

Well, I don't have a rating on 412 but i will try to explain. In the FLM it just says: Engine 1 throttle: Open to idle at 12% N1 rpm minimum. However, every 412 pilot i met, does it the way in the video but i can't explain why. Yes for the 412 it is normal to have the collective up because during shut down, with the last few rotations of the main rotor you pull the collective up. It's because of some bearings or dampers, to increase lifetime i think.

why some helicopters requires 2 pilots?

0:50 what happened there

Is that in Ahlen at Agrarflug Helilift?

@youtuubesucks

9 жыл бұрын

+Huey-Fan Negative. The video was taken in Sudan/Africa. The chopper is from Agrarflug though!

@youtuubesucks

8 жыл бұрын

+Huey-Fan Negative, the video was taken in Heglig, Sudan.

Nice ❤