Simple Question About Dash 8 / Turboprop Sounds???

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wowie_kazowie
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Simple Question About Dash 8 / Turboprop Sounds???

Post by wowie_kazowie » Sat Nov 06, 2010 12:19 am

Hey Everyone!
I just had a simple question about a common sound you hear around the airport coming from the turboprops and especially the Dash 8. The engine sound drops to a lower sound for a few seconds...You can here it in these two Vids:

At 24 Seconds in this one


at 5:08 in this vid


I asked around and the best answer I got was its the pilots adjusting the prop/feather but he was not sure... Is this true?? if not what is it? Just curious as it is one of the best sounds ever (one of my simple pleasures)!

Thanks Gents
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No Conflict
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Re: Simple Question About Dash 8 / Turboprop Sounds???

Post by No Conflict » Sat Nov 06, 2010 7:38 am

At 24 seconds, that is us putting the one engine into start feather and using the other to taxi. This has to do with the cooling down period required for each engine before shutdown (after stopping at the gate, we normally wait 30 sec or so before shutting down number 2 at the same time waiting for ground power to come up). It also sounds like the capt putting one into disc to slow the plane down without using brakes.

HTH
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mattedfred
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Re: Simple Question About Dash 8 / Turboprop Sounds???

Post by mattedfred » Sat Nov 06, 2010 7:50 am

I think the sound the original poster is referring to is discing. The Captain selected discing while he was clearing the active in the first video and the Captain selected discing as he commenced his taxi.
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Re: Simple Question About Dash 8 / Turboprop Sounds???

Post by No Conflict » Sat Nov 06, 2010 7:59 am

mattedfred wrote:I think the sound the original poster is referring to is discing. The Captain selected discing while he was clearing the active in the first video and the Captain selected discing as he commenced his taxi.

Lol, didn't watch the second vid till now... yup, sounds like discing.

Looking forward to flying with ya back in YYZ Mattedfred!
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Re: Simple Question About Dash 8 / Turboprop Sounds???

Post by mattedfred » Sat Nov 06, 2010 8:34 am

I would reciprocate but I don't know the user behind the username. PM me if you like.
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Re: Simple Question About Dash 8 / Turboprop Sounds???

Post by Chaxterium » Sat Nov 06, 2010 8:48 am

Yep, that's discing. My favourite sound. You should hear it with 4 props! ;)
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Re: Simple Question About Dash 8 / Turboprop Sounds???

Post by wowie_kazowie » Sat Nov 06, 2010 10:03 am

Thanks for the answers guys, appreciate it! and if you care to answer one more, do you just use discing to for added braking on the ground or always during taxi?
Thanks
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Re: Simple Question About Dash 8 / Turboprop Sounds???

Post by flying4dollars » Sat Nov 06, 2010 10:21 am

You'll hear this sound with all PT6 turboprops. When taxiing, rather than using toe brakes, selecting the power levers into ground fine (or coaxing it into the reverse gate if you're in a B100) aids in braking and causes the props to make this sound as the propeller pitch changes. I think garrets are somewhat the same but I'm not sure since I've never operated one.
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Re: Simple Question About Dash 8 / Turboprop Sounds???

Post by iflyforpie » Sat Nov 06, 2010 11:55 am

Definitely discing in each of those vids.

Discing is sort of an eeeeeEEEEEooWWWoooEEEEeeeeeoOOWWWoooeee sound, where feathering is sort of a whhhooooommpp sound.

You can sort of hear the feather sound here...

http://www.youtube.com/watch?v=vD5IVoe9Les#t=0m45s

You can hear the discing and the feathering of a B350 here (feather at about 38s).

http://www.youtube.com/watch?v=5pVXEQQIfi8
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KISS_MY_TCAS
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Re: Simple Question About Dash 8 / Turboprop Sounds???

Post by KISS_MY_TCAS » Sat Nov 06, 2010 1:58 pm

flying4dollars wrote:coaxing it into the reverse gate if you're in a B100. I think garrets are somewhat the same but I'm not sure since I've never operated one.
Uhhh....B100s have Garretts on the wing. :smt017

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Re: Simple Question About Dash 8 / Turboprop Sounds???

Post by KK7 » Sat Nov 06, 2010 2:59 pm

Chaxterium wrote:Yep, that's discing. My favourite sound. You should hear it with 4 props! ;)
+1 AGREED!!!

In some cases discing is used, in addition to saving the use of excessive brakes, to keep the prop RPM in an acceptable range. In the DASH-7 there is a range of prop RPM that is not recommended, and simply keeping the power levers at flight idle causes the RPM to be in this bad range when on the ground. Discing the props keeps the RPMs above this range.
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Re: Simple Question About Dash 8 / Turboprop Sounds???

Post by Chaxterium » Sun Nov 07, 2010 4:51 am

I also love the sound a PT6 makes as it goes into feather.

Nothing like the sound of discing though.
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Re: Simple Question About Dash 8 / Turboprop Sounds???

Post by BingBong » Sun Nov 07, 2010 10:30 am

Another awesome sound on the dash....start the right engine....bring it out of feather....power leaver that sucker into quiet taxi mode...LOVE IT!
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Re: Simple Question About Dash 8 / Turboprop Sounds???

Post by flying4dollars » Thu Nov 11, 2010 12:14 am

KISS_MY_TCAS wrote:
flying4dollars wrote:coaxing it into the reverse gate if you're in a B100. I think garrets are somewhat the same but I'm not sure since I've never operated one.
Uhhh....B100s have Garretts on the wing. :smt017

Image
B100 = Beech 100 or King Air 100. Just like B1900 = Beech 1900 :mrgreen:
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Re: Simple Question About Dash 8 / Turboprop Sounds???

Post by BTD » Thu Nov 11, 2010 5:56 am

flying4dollars wrote: B100 = Beech 100 or King Air 100. Just like B1900 = Beech 1900 :mrgreen:
I think everyone new what you meant, but I guess technically.

http://webcache.googleusercontent.com/s ... clnk&gl=ca
The next in the series was the B100, which featured 715 shp (533 kW) Garrett AiResearch TPE-331 engines as an alternative to the Pratt & Whitneys offered on other King Airs, and another increase in MTOW to 11,800 lb (5,350 kg). The B100 was introduced in 1976 and was produced concurrently with the A100 for several years; manufacture ceased in 1983 after 137 were built.
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Re: Simple Question About Dash 8 / Turboprop Sounds???

Post by BingBong » Thu Nov 11, 2010 7:24 am

edited...due stupidity....
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Last edited by BingBong on Fri Nov 12, 2010 1:19 pm, edited 1 time in total.

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D5GRVTY
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Re: Simple Question About Dash 8 / Turboprop Sounds???

Post by D5GRVTY » Thu Nov 11, 2010 10:14 am

If we're all being scientifically correct...a Beech 1900 is B190 according to transport....if were all gonna play this game we better play by the rules :wink:
Huh, all those years of beech 1900 time go down the drain because my company apparently did a type rating on a BE02?? :roll:

Sorry couldn't resist correcting someone's correction ;)
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Re: Simple Question About Dash 8 / Turboprop Sounds???

Post by Legacy » Thu Nov 11, 2010 5:28 pm

Actually none of the Beeches are B. thats designation is Boeing's obviously. Beech is Be. Like GRVTY sais, a 1900 is Be-02, King air 100 is Be-10, 200 is Be-20.
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Re: Simple Question About Dash 8 / Turboprop Sounds???

Post by iflyforpie » Thu Nov 11, 2010 11:07 pm

Yeah, but Beech was retarded and put their successive model letters in front of the numerical designation (90, A90, B90, C90 etc) and then they decided to put even more letters behind the numbers for successive models of models (C90A, C90B, etc).

B200 will universally be accepted as a Beech 200 because just about all the variants are the B200 and B is also conveniently what Beech starts with. But only about a third of the 100s were the noisy 'B's from when P&WC went on strike during the 70s till the 100 finished production.


I don't have too much experience with Garretts, but I believe you have to reverse them slightly to get them off the pitch locks which makes an interesting sound before taxi...
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Re: Simple Question About Dash 8 / Turboprop Sounds???

Post by 5400AirportRdSouth » Thu Nov 11, 2010 11:43 pm

Yup, first time I stood in front of one at startup I thought the pilots were taking the piss by blasting me. By the third or fourth time I clued in....
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