When starting a turbine engine, how do you know its started?

I think most King Airs/turbine beech products go something like this (but I don't fly a King Air so don't take my word for it :)):

Ignition/Engine Start - ON
*FUEL PRESS light goes out.
*N1 increases and stabilizes at > 12%.
Condition Lever - Low Idle
*Fuel flow jumps from 0 to 100 lb/hr (PPH).
Prop - Forward out of feather
*Monitor ITT & N1. ITT will start rapidly increasing towards the red line around 800 deg C and hopefully peak before then.
*Check oil pressure.
*Verify ITT rollback (within 10 s).
*N1 stabilizes around 50%.
Ignition/Engine Start - OFF.
Generator - Reset -> On.
*Check voltmeters, start second engine, etc...

Quick note:

On a King Air (like a B350) with a PT-6, "N1" is referring to a gauge called "Turbine RPM (%)." It's measuring the RPM of the higher speed section of the gas turbine engine sometimes referred to as the "gas generator" (and some N1 gauges are called "Ng" instead, with g for gas generator). To make things extra confusing turbojet and turbofan engines re-use the N1 and N2 nomenclature, only in a turbofan "N1" refers to the fan speed or speed of the low stage compressor/turbine section, while "N2" refers to the high stage compressor/turbine.

High stage is the turbine closest to the fire in the combustion chamber, which is going to spin the inner compressor blades its connected to at a faster RPM. Low stage is the outermost turbine section(s), which are going to spin slower since the expanding exhaust gasses have lost energy by that point, having already transferred some of its kinetic energy to the high stage turbine blades to spin them. Thus the corresponding low stage compressor blades also spin slower. Some Rolls Royce Engines have three stages instead of the usual two, and then you get an N1, N2 and N3 gauge.

So in my example, "N1" on a King Air means the same as "Ng", and as "N2" on Autothrust Blue 's ERJ EICAS. And on his new ride, NH (N2) and NL (N1) are going to be on the same NH/NL gauge. Crazy Brazilians...
 
MoMatt said:
It helps to think about what's going on inside the respective engines during start. Turbine engines handle the "suck - squeeze - bang - blow" sequence in a much simpler and more elegant fashion.

A piston engine is really pretty complex and has metal parts flinging every which way when it runs. A turbine engine just spins from one central axis.

So, the start sequence is just: spin the turbine to start moving air, start dumping fuel into the combustion chamber and ignite it with sparks. The flame will eventually sustain itself as long as it's fed fuel, and the compressor / turbine rotation stabilizes at a given RPM based on the amount of fuel that gets dumped in.
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Exactly what I said. PFM.
 
SteveCostello said:
No need to be condescending. I can see why this is a bit of a mystery to some folks, especially if they've only flown piston. Turbines are a bit of a mystery to folks... it's just a cylinder of fire, noise, and magic. I'd venture to say that quite a few pilots that have never flown turbine (and even more of the general population) have very little idea of how they work, much less start or know how the start process works.
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Didn't mean to be a jerk, for some reason I thought the OP was high time, or at least flew from regionals and was trolling.
 
I can totally relate to the OP. I've got an aquaintaince who works at Honeywell, and asked him to explain a jet/turbine motor to me while heading out for lunch. While standing next to the thing. In a cross-section. The first time, it was like,

"DUDE... This is SO simple. It works on the same principle as a car motor. Suck, squeeze, bang, blow. Air gets sucked into the stage 1, and squeezed. Mixed with fuel, and ignited, then pushed into the 2nd stage and repeated. Make sense?"
"Um. No. Not really. Why all the blades?"
"Dude.... wha wha wha..." And he started talking really fast, and way over my head.

The 2nd time went a bit better, but, I'm still all screwed up when it comes to how the power is harnessed to regulate how fast that shaft spins the prop. I'm sure it's not all that complicated, just above my pay grade right now.
 
MoMatt said:
It helps to think about what's going on inside the respective engines during start. Turbine engines handle the "suck - squeeze - bang - blow" sequence in a much simpler and more elegant fashion.

A piston engine is really pretty complex and has metal parts flinging every which way when it runs. A turbine engine just spins from one central axis.

So, the start sequence is just: spin the turbine to start moving air, start dumping fuel into the combustion chamber and ignite it with sparks. The flame will eventually sustain itself as long as it's fed fuel, and the compressor / turbine rotation stabilizes at a given RPM based on the amount of fuel that gets dumped in.
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Simple? Sure. Elegant? Possibly not ;)

I would consider a radial "elegant." Certainly not simple.
 
GX said:
"DUDE... This is SO simple. It works on the same principle as a car motor. Suck, squeeze, bang, blow. Air gets sucked into the stage 1, and squeezed. Mixed with fuel, and ignited, then pushed into the 2nd stage and repeated. Make sense?"
"Um. No. Not really. Why all the blades?"
"Dude.... wha wha wha..." And he started talking really fast, and way over my head.

The 2nd time went a bit better, but, I'm still all screwed up when it comes to how the power is harnessed to regulate how fast that shaft spins the prop. I'm sure it's not all that complicated, just above my pay grade right now.
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It's more like, the compressor section sucks air into the compressor stages, which squeeze it. Each stage of compressor blades squeezes the air more than the last. It gets to the combustion chamber at a very high pressure (and thus high temperature, since compressed air heats up). Fuel is injected via some sort of Fuel Control Unit (FCU) and blown up by a couple ignitors (turbine name for "spark plug"). The resulting high temperature/high pressure boom wants to fly out the back as it expands ("blow"), and the job of the turbine blades is to collect as much of that energy as possible and keep the thing spinning before it's all lost out the tail pipe. Each stage of turbine blades collect as much energy as possible, turning it into rotational kinetic energy which spins that turbine. You're never going to get 100% efficiency out of one turbine (not even close), which is why they have a bunch stacked one after another. The turbines then turn a drive-shaft, which passes through the center of the engine and connects to the compressor blades at the front (in a two stage, you get two concentric drive shafts).

Suffice to say, gas turbine engines are the ultimate rube-goldberg/perpetual motion machine, because once you get them spinning they'll just keep doing their thing until you cut off the fuel (or it runs out).

Are you asking about a turbo-prop at the end of you're question? Those are a different beast, and there are two fundamentally different design philosophies for them: Direct-Drive (Garrett) vs. Free Turbine (Pratt & Whitney PT-6). PT-6s are weird because they're mounted backwards, and are cut in half... :)
 
Our pt6 start basically goes.....
Start/ignition, 12% N1, low idle, 50% N1, starter off. Repeat.
12% happens quicker than a piston engine lights, but it takes 5-10 secs to get up to 50.
 
inigo88 said:
snip about PT-6
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On the TBMs I flew, the procedure was to put the prop lever in full fine pitch/high RPM right away, to give a little extra cooling (or at least that's what I think the stated reason was, it's been a few years).

So in my example, "N1" on a King Air means the same as "Ng", and as "N2" on Autothrust Blue 's ERJ EICAS. And on his new ride, NH (N2) and NL (N1) are going to be on the same NH/NL gauge. Crazy Brazilians...
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NH, NL and Np actually make more sense to me. One of these is high pressure, the other is low, and the other is the propeller. Keep it simple, stupid!
 
Yeah, batt on, beacon on, props forward. Although in reality, I doubt there's much reason. I've seen people start in feather, I've seen them taxi in feather and feather before shutdown. I don't think the engine really cares.
 
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