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Subject: Turbine transition
 
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LeewenhookeUser is Offline
JH Guru
JH Guru
Posts:52

11/02/2011 1:31 PM  
Unless you're working on some kind of European JAA thing and it's mandatory for you, I don't think paying for a "turbine transition" is very cost effective or educational for what it costs. As a new student, there are other, uh… less dumb ways to piss away your training dollar. Managing a turbine engine is in a lot of respects, easier than managing a piston engine. That’s why I’m offering the training here at a greatly discounted rate!

Learn how an Allison/Rolls-Royce C250 turbo-shaft engine works, 'cus that's what you're gonna be flyin’.

http://en.wikipedia.org/wiki/Turboshaft
http://en.wikipedia.org/wiki/Allison_Model_250

From now on, it is assumed we’re talking about a C250 engine. Did you read that? Good. Now you know the way a turbine starts is by getting the gas producer (N1) turbine spinning with an electric starter. Once there is enough airflow in the combustion chamber, you crack open the twist grip, which adds fuel. The fuel is ignited in the chamber and gets the flame going. Of all the air the engine is sucking in, only 20% of it gets burned in the combustion chamber. The other 80% acts as a buffer to keep the flame centered in the middle of the can and keeps it from burning the walls of the chamber.

If there isn’t enough airflow before the flame starts, it will touch the sides of the combustion can and burn a hole in it. That’s called a “hot start”. The cockpit indication will be Turbine Output Temperature (TOT) 810-927˚C for >10 seconds or >927˚ for any amount of time.

Don't ever have a hot start because if this is your first turbine job, you're gonna be asked to step into your bosses office because you're f*cking fired. You will have blown your only shot at being a "real pilot" and you'll have to go back to your former non-flying job where you had money and respect. No one wants that, right? Don't let that intimidate you though. Here's how to avoid it in 99% of cases:

1. Make sure you have enough voltage before attempting start. (>24 volts) This is to ensure the starter can spin fast enough and long enough to keep the airflow going during the start sequence. If not, go find a Ground Power Unit (GPU). No GPU? Charge the battery. No charger? What kind of two-bit operation is this? I'm sure you have a deadline to keep but don’t attempt a start with low voltage.

2. Ensure blades untied, area clear, TOT is below manufacturer specifications (150˚C) and N1 is >15% before adding fuel. If the engine is hot from a previous start and it’s too high, just keep motoring the starter until the airflow cools it below 150, then crack the throttle to idle. If you’re at high altitude and the air is thin or this engine has a history of running hot, keep the starter running past 15%. It should top out around 18-20%. This is like extra insurance against a hot start.

3. After you crack the throttle to idle, the engine will get going and N1 and TOT will rise rapidly. Keep starter engaged up to 58% N1 to ensure you have enough air moving during the start sequence. Take note of how fast TOT rises and where it peaks. This will become a "baseline" for future starts. If TOT ever rises faster or higher than the baseline, cut off the throttle to abort the start and continue to motor the starter to cool the engine back down. Figure out the problem and try again if you still have enough battery voltage.

4. Once you get it started, it’s more or less like a piston engine. Oil and transmission pressure should be in the green by now and you'll be idling. You will have a rotor torque gauge instead of manifold pressure but they mean basically the same thing to the pilot. At high altitude, you may reach a TOT limit before a torque limit but that’s not too much extra to keep an eye on. All other common-sense helicopter power management rules apply. If you've ever flown an R44, the Jet Ranger will mostly act like that, but harder to get in and out of, more expensive, louder, slower, less maneuverable and easier to autorotate.

Congratulations! There's your turbine transition! Now you may send $20 for ground training to my paypal account .

If you feel cheated somehow and are dying to spend money on something else instead, I would recommend an NVG or vertical reference/longline course. NVG’s are becoming mandatory at nearly all EMS operations and the vertical reference course will give you a good intro into utility flying. Neither of these skills are intuitive to normal helicopter flying. If funds are limited, I think either of these courses will pay more dividends than a turbine transition. I wouldn't reccomend either though until you are further along in your career (>1,000 hours) because starting out, you don't know what industry you want into (utility guys don't need NVG's and offshore or EMS guys don't do long-line) and you will not have the flying proficiency to get the maximum benefit from the training.

Good luck!

60-driver, Robinson survivor
SPIFR HEMS pilot
Sayer of Nay

"I regret to say that we of the FBI are powerless to act in cases of oral-genital intimacy, unless it has in some way obstructed interstate commerce."

-J. Edgar Hoover
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