flightsim91

Dash 8 Q400 Engine

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Hello everyone,

     I don't know if this is the correct place to post this. Please forgive me if it's the wrong forum.

     I learned that the PT6 on the Q400 is a free turbine engine, but the external exhaust is in the rear. I, for the life of me, can't figure out how that works. Yes, the intake can be in front externally and run under the turbine to the rear and enter the turbine from there. But how does the exhaust go to the back if the space underneath is used for intake.

     If anyone can explain this to me, I will finally be able to sleep again. 😂

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For one it is not a PT6. It is a PW100. Wiki a PW100 and it is more clear.

Edited by Adrian123

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The Series 400 uses Pratt & Whitney Canada PW150A

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I should have said 100 "series"

 

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Some cool videos.

 

 

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2 hours ago, Adrian123 said:

For one it is not a PT6. It is a PW100. Wiki a PW100 and it is more clear.

 

1 hour ago, BIGSKY said:

The Series 400 uses Pratt & Whitney Canada PW150A

😬😬😬

Yes, of course. I have no idea how that went over my head before posting. Thanks for the correction!

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41 minutes ago, DaveCT2003 said:

 

Some cool videos.

I just watched these, and from these, the intake/exhaust path makes sense.

However, the first of the two videos shows the turbine only. From that video, it almost looks like it's a direct drive engine since the shaft appears to run from the first centrifugal compressor through the front of the turbine into the gearbox. If the engine is a free turbine, is the propeller driven by a shaft concentric to the turbine shaft? Or else how can the propeller shaft (the one running in-line with the turbine shaft, not the one behind the propeller hub, just to be clear) be geared off of the turbine when the turbine is the rearmost element of the turbine?

I read online that the engine has a "unusual three-shaft design." I can see one shaft directly behind the propeller hub and one in the turbine. Where is the third one that defines a free turbine engine?

Edited by flightsim91

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5 hours ago, flightsim91 said:

 

😬😬😬

Yes, of course. I have no idea how that went over my head before posting. Thanks for the correction!

Possibly you saw the name PT7, which is what the P&W 100 Series engines were originally called and they do very occasionally get referred to by that older name, so it'd be easy to get PT in your head and then conflate that with a 6, since the PT6 is a very common turbine engine.

Edited by Chock

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The PW150 is different to other engines in the PW100 family (such as the PW120), as they are nearly twice the power they have an axial compressors in addition to centrifugal. However all the family is twin spool, if you want a triple spool you'll need a RB.211 or Trent! They are also all free power turbine (just like a PT6) they are most definitely not geared (like a Garrett TPE331).

The combustor is reverse flow, which alters the airflow direction. I believe the power shaft is concentric within the other spools as the gearbox is at the front, but I am by no means an expert and suggest you google for some diagrams or technical information.

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The combustor is reverse flow, which alters the airflow direction. I believe the power shaft is concentric within the other spools as the gearbox is at the front, but I am by no means an expert and suggest you google for some diagrams or technical information.

Yes. That's what I really want to know. The "three shaft design" meaning one behind the propeller hub, one turbine shaft, and one power shaft concentric to the turbine shaft that runs from the turbine element in the rear to the gearbox in the front. I can't find any diagrams of this, so I have no idea. If that is the case, why not just make it a reverse flow? Seems so much easier to maintain and cheaper to make then a complicated concentric shaft system.

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4 minutes ago, flightsim91 said:

Yes. That's what I really want to know. The "three shaft design" meaning one behind the propeller hub, one turbine shaft, and one power shaft concentric to the turbine shaft that runs from the turbine element in the rear to the gearbox in the front. I can't find any diagrams of this, so I have no idea. If that is the case, why not just make it a reverse flow? Seems so much easier to maintain and cheaper to make then a complicated concentric shaft system.

Jim,

Drop over to the Smart Cockpit website, Dash 8 Q400 section and grab the Power_Plant.pdf file.  It has both a good narrative as well as several diagrams.

Sorry, I didn't think about this earlier.  I've been away from the Majestic Dash 8 project for a couple of years.

Best wishes.

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Drop over to the Smart Cockpit website, Dash 8 Q400 section and grab the Power_Plant.pdf file.  It has both a good narrative as well as several diagrams.

Oh beautiful!! Exactly what I needed to see. Thank you!

Speaking of the Majestic Dash 8, I do have it. It's a beautiful piece of software, but it scares the living word not allowed out of me... 😂 I'm using the Aerosoft CRJ to transition over to airplanes like the Dash 8. Hopefully I'll take my brave pills eventually and get back to the Dash 8.

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Funnily enough, I was chatting to a FlyBe pilot last night at Manchester just before he was off to fly one to Exeter and I asked him if he actually liked being on the Dash 8. He said yes, but the ones that FlyBe had were all a bit worn out (won't use the actual phrase he used to describe that condition, I'm sure you can take a good guess lol). Nevertheless, he said they're great, especially for what FlyBe use them for and really suit that kind of flying. Since it had been snowing that night and was fairly horrible weather, I said that it could be worse, you could be on the ATR, which are known for not being great in icing conditions, and he said, 'well yeah, there is that' lol.

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you could be on the ATR, which are known for not being great in icing conditions

I'll just hijack my own thread quickly and ask why that is.

I see First Air ATR's flying all over northern Canada where it's not famous for being warm or dry. They must have something to deal with icing.

Edited by flightsim91

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4 minutes ago, flightsim91 said:

They must have something to deal with icing.

They do, not great though. Leading edge rubber boots! They "warp" the wing. Doesn't sound that appealing compared to heating the leading edge with bleed air.

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That's standard for props, the Q400 uses boots too.

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Yeah, that's what I thought, don't they all use leading edge boots? I guess I'll have to go back to Yellowknife one day and ask a FirstAir ATR crew...

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