Turbine tot

[Mav27]

I am looking to get a turbine, OH58A+ C20B
My concern is what information I have read as far as turbine transition leaves me with a few concerns. I understand that the start up and shut down is very critical. The area that I would like some advice on is how easily does a turbine jump to a dangerous tot when in flight? The article made it sound like you are always on the edge of a melt down. Just wondering if thats the case or not. I would think you would have to be working it pretty hard to over temp.

[Epiphany]

Temperature limits for turbine engines are something to be aware of - the same as any engine, gearbox or airframe limits. Start up is when you should be most attentive as this is generally when you will see temperature peaks - particularly if the engine is already hot. If it is and you are able then a vent is your best bet. Depending on your operating environment you will find that during flight the torque and N1 are your first limits.

Welcome to the turbine world - you'll find life much easier.

[Hell Man]

Mav27 - You should look forward to your turbine transition, as a powerplant they make great sense in helos!

Yes, the older generation 'manual' start birds require a certain amount of sensitivity, particularly during start, but the great thing about them is that you can control them throughout this process. Turbines are reliable as hell, so, enjoy!

Um Lifting - That was a nicely informed response for the turbine newbie! :ok:

HM

[Hilico]

This Youtube clip shows the same turbine a/c being started twice. The commentary is good and makes it clear what's happening. I was amazed at how much quicker the engine got up to speed on the second go.

Stick with it through the preamble, it's worth waiting for.

H500 start (http://www.youtube.com/watch?v=bE56Nf6lsSQ)

bE56Nf6lsSQ

[whatsarunway]

Just make sure you have a good battery on start up and you give it the two minutes on shut down and the engine should last forever.

Does give you a fright when you see the needle rush tword the red line on start but you get used to it. . . Perfectly normal !

O i miss flying. . . .

[Matari]

To add to what Um...Lifting and others wrote, I always thought there should be a little guidebook titled "Care and Feeding of my Gas Turbine." It would only be a few pages long, but contain some easy-to-remember tips. Like:

1. Start into the wind. Air blowing up the pipe is not good.
2. Where possible, always start with a fully charged ground battery cart. Low battery power equals slow N1 speeds equals low airflow and higher temps. High temps at start are your enemy.
3. When possible, don't stop and restart. Keep the blades turning. Starts (cycles) stress the hot section. Better to keep humming peacefully at idle.
4. The fuel control (very noticeable on a C20) goes through a couple of fuel schedules or ramps. The initial lightoff will see the the TOT gauge scream to yellow line, then come back down. That's when many new pilots relax, but forget that the second schedule starts soon after, sending another schedule of fuel into the combustor. That second spike can be just as tricky, especially if N1 speed hasn't built sufficiently. Keep your eyes open.
5. Starting uses all five senses, not just the eyes. Listen for the tick-tick-tick of the igniter. If there's no tick, or if the igniter is intermittent, don't light off. Smell more of the sweet aroma of burnt kerosene than usual? You're probably downwind. Feel the rocking of the ship as the rotor blades swing reluctantly into motion. No rocking? Are your tiedowns still on? (it has happened).

Your turbine is like a good pet. Care for it well and it will serve you well for many years. Abuse it, and it will bite you.

[Gomer Pylot]

In flight, the TOT shouldn't change much except when changing power. With a weak engine, you can approach TOT limits as you approach 100% torque, so you want to keep an eye on both gauges, but after takeoff the TOT should stay well within the green, and you don't really have to worry about it changing very much. For a good engine in an OH58, you should never approach engine limits in flight, even on takeoff.

[Shawn Coyle]

There are those who have started a 206/212/205/UH-1/OH-58A/C with the blades tied down, and those who will...

[Brilliant Stuff]

Yupp done it on the 206, it sounded good though.:O

[RVDT]

Couple of other points missed in the video -

Check that the heater and anti-ice is OFF prior to start. You need all the excess air going into the combustion chamber.

Testing the warning lights is always a good idea.

(Its youtube so....................?)

Nearly all helicopters wil light off before going into the idle detent. Roll it slowly to the point it lights off and keep it there. Some of the bigger 250's and CECO C20/20B's (rare) can be modulated but a Bendix C20 fuel system is on its own.

If you cannot attain the required N1 don't light it. Get a better electrical source.

Glance at the oil pressure gauge before you light it off, it should have some.

Until it is at idle speed, keep your finger on the starter, keep your finger on the starter, keep your finger on the starter, keep your finger on the starter!

If it gets hot, shut off the fuel with the twist grip, keep your finger on the starter, keep your finger on the starter, keep your finger on the starter, keep your finger on the starter!

Not so intuitive to piston jockeys for the first time who are used to taking their finger off the button when they hear the engine make a noise that sounds like it is running.

Fast and hot is the best, anything else is not. Think about the best method of putting your hand in a candle flame.

The 2 minute rundown is to get the core temperature down in the oil galleries in the engine so that carbon does not form and clog the scavenge strut. It applies after flight after achieving flat pitch and is not required if you are only doing ground runs. P.S. each manufacturer/model is different, i.e. 2 minutes on a TM Ariel is detrimental.

[500 Fan]

I've just started flying a turbine so still crapping myself on each start!

A good battery is certainly your best friend as a turbine newbie. Looking at the various turbine starts on youtube, there seem to be some variances in the rate at which N1 increases from the second the start button is pressed on different helicopters. The N1 on the turbine I am fortunate to be flying seems to accelerate fairly quickly compared to some on youtube. That has me thinking: What if you pass 15% and you haven't introduced fuel? Is there any damage done to the engine if fuel is introduced at 17, 18 or 19% N1? I lit off one start at 15% and the TOT stayed well within limits but the manual recommends various starts at 13%, 14% or 15% depending on the outside temperature. Thanks.

500 Fan.

[Fun Police]

i'd say no harm done, but do what the manual says because if you wait too long then the battery will start to get depleted. it doesn't take long.

one thing i was taught when i got my first endorsement on a turbine (a 500D) was on your walk around - which everyone does before each start i know :D - was to turn the tail backwards which verified that the turbine is not locked up before you go to start it.

all good advice given above.

[Mav27]

Thanks for all the information.

[krypton_john]

Here's a great video walk-through starting the C20W on an Enstrom 480B:

YouTube - How To Start an Enstrom Turbine Helicopter (http://www.youtube.com/watch?v=pMqVMsMcps8)

pMqVMsMcps8

[perfrej]

I started turbine transistion on the 330 9 months after I got my PPL on the 300, which puts in the summer of 1997. I have never had an issue with a start and I have a few observations that have been filed in my head. I have type ratings for 330, EC-120, B206 and H500 turbines, so my experiences are with two main engines.

Temp that's good
It was said above: hot and fast is best for the engine. Fluctuations in tot and peaks are bad.

N1 acceleration
It is important to introduce fuel while you still have acceleration on the N1. If you let it flat out at, say, 14% and then light off you are going to get a much more erratic start with larger peaks. Better to let go at 12% while you still have acceleration.

Battery
A good battery is best. If you start with a GPU you are going to get a nice, fast start, albeit somewhat cold. I once started a 500c from a totally over-sized GPU meant for a BAE146 commercial aircraft. I wasn't fast enough to manage to open the throttle when it passed 15%... The thing was at 58% N1 in less than 3 seconds... Nice and fast ;) and absolutely no peaks - just a quick rise to the proper temp.

When the battery is really too low or cold
I have discussed this at length with mechs and professional pilots. As we have arctic conditions here, a start at -25C or lower is nothing unusual. I was shown by a mech how to do it:

1 - If you can, pre-heat the engine some way, like with a car heater if you have electricity. It will make it spin with less friction

2 - Crank, open when acceleration of N1 decreases, even if way below 12%

3 - When tot approaches the red line, shut off until it goes down in the yellow, then open again, keep the button depressed

4 - Keep modulating off and on until you reach idle.

This may seem dangerous, but it really is safe if you stay alert and don't crank too much over the max crank time. You will not over temp the engine unless you focus on the wrong things. If it is cold, your starter will not over heat the first minute or two.

EC-120
This is one dangerous beast when it comes to battery. If the voltage drops below 17 Volts, the cut off release will not function. So, in this helicopter you have to watch the Voltage as well as the engine parameters. If voltage drops below and you get a hot start you cannot cut off fuel with the collective throttle and will have to resort to the big lever in the ceiling in order to stop the flow (naturally while still cranking with your other hand)... I wonder who designed that system.

Anyway, thoughts from an amateur with input from some professionals (and you should always listen when experience talks).

[311kph]

So, in this helicopter you have to watch the Voltage as well as the engine parameters.

I was also taught (on Astazous III and XIV , but with 'manual' two step start) when starting to look for voltage, but as an indicator of spark igniter readiness to fire. It wasn't working properly below 16V, and that starter could pull hard, especially with weak battery. So the 'after 2000 RPM, switch to ignite' became 'after above 16V switch to ignite' sequence.