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DC-9-50 Engine Start Noises  
User currently offlineN126DL From United States of America, joined May 2010, 125 posts, RR: 0
Posted (1 year 12 months 3 days 9 hours ago) and read 4896 times:
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Anyone know why the DC-9-50 engines have a strange noise upon startup? Is it a difference between the JT8D-17 and the JT8D-219's on the MD-88 which don't make that noise?

http://www.youtube.com/watch?v=swWfoPF1F3A
at around 00:30 mark - the whoop whoop whoop


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17 replies: All unread, jump to last
 
User currently offlineZANL188 From United States of America, joined Oct 2006, 3517 posts, RR: 0
Reply 1, posted (1 year 12 months 3 days 9 hours ago) and read 4875 times:
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Sounds like a flight deck alarm to me.... Configuration or Master Caution maybe?


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User currently offlinetb727 From United States of America, joined Jun 2005, 1586 posts, RR: 9
Reply 2, posted (1 year 12 months 3 days 8 hours ago) and read 4857 times:

I have no idea, we have a 727 or 2 that does it too, I've heard it in Learjets and Falcons I have flown too. I think it has something to do with the igniters.


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User currently offlineXFSUgimpLB41X From United States of America, joined Aug 2000, 4194 posts, RR: 37
Reply 3, posted (1 year 12 months 3 days 7 hours ago) and read 4837 times:

It's when the fuel lever is brought from cutoff to run and the starter is engaged.


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User currently offlineflashmeister From United States of America, joined Apr 2000, 2900 posts, RR: 6
Reply 4, posted (1 year 12 months 3 days 7 hours ago) and read 4833 times:
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Check out this thread: Two DC9 Questions (by DrDeke Nov 15 2006 in Tech Ops)

What you're hearing is interference in the PA system caused by the ignitors firing.


User currently offlineFlyASAGuy2005 From United States of America, joined Sep 2007, 7004 posts, RR: 11
Reply 5, posted (1 year 12 months 3 days 3 hours ago) and read 4741 times:

Something that's always been on my mind...what is that almost "bang" sound you ear right at the end of the 88's engine start right before final spool? It's very hard to explain but as the engines turn and gain EPR you hear a sort of bang, the engine sounds goes up (as if you're spooling up) then it settles. It's right at the end of the engine start.


What gets measured gets done.
User currently offlineN243NW From United States of America, joined Jul 2003, 1630 posts, RR: 20
Reply 6, posted (1 year 12 months 2 days 13 hours ago) and read 4601 times:

Quoting FlyASAGuy2005 (Reply 5):
Something that's always been on my mind...what is that almost "bang" sound you ear right at the end of the 88's engine start right before final spool? It's very hard to explain but as the engines turn and gain EPR you hear a sort of bang, the engine sounds goes up (as if you're spooling up) then it settles. It's right at the end of the engine start.

You're probably hearing the fuel being introduced, which on the JT8D produces a terrific and very pronounced light-off sound. It's right at 1:05 in this video, but (of course) some baby has to be making noise at the same time so it's hard to hear. http://www.youtube.com/watch?v=jwwhKYaLBTc



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User currently offlinePGNCS From United States of America, joined Apr 2007, 2821 posts, RR: 45
Reply 7, posted (1 year 12 months 2 days 10 hours ago) and read 4564 times:

It's the ignition system used for engine starts.

User currently offlineFlyASAGuy2005 From United States of America, joined Sep 2007, 7004 posts, RR: 11
Reply 8, posted (1 year 12 months 2 days 3 hours ago) and read 4484 times:

Quoting N243NW (Reply 6):

That's the exact sound I was talking about (timing). It wasn't as pronounced in this video bu that was it.



What gets measured gets done.
User currently offlineN243NW From United States of America, joined Jul 2003, 1630 posts, RR: 20
Reply 9, posted (1 year 12 months 2 days 1 hour ago) and read 4454 times:

Quoting FlyASAGuy2005 (Reply 8):

That's the exact sound I was talking about (timing). It wasn't as pronounced in this video bu that was it.

That's what I figured. Funny thing is - it seems to be the loudest just behind the wing. If you're sitting right next to the engine, from my experience at least, it is definitely audible but not quite as loud.



B-52s don't take off. They scare the ground away.
User currently offlineAmericanAirFan From United States of America, joined Jun 2004, 408 posts, RR: 3
Reply 10, posted (1 year 12 months 1 day 14 hours ago) and read 4379 times:

Quoting N243NW (Reply 6):
You're probably hearing the fuel being introduced, which on the JT8D produces a terrific and very pronounced light-off sound.

I got really lucky while taking shots of an Allegiant MD-87 from its backside. I was taking 1" exposures because the light was low. It was hand held. I had no idea that I caught the fuel introduction until I got home and looked through my photos.




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User currently offlineNWADC9 From United States of America, joined May 2004, 4896 posts, RR: 10
Reply 11, posted (1 year 12 months 1 day 8 hours ago) and read 4315 times:

Why is this "whoop whoop" found on DC-9s and not MD-80s? Was there an improvement with the JT8D-200 series that did away with this sweet song?


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User currently offlineN243NW From United States of America, joined Jul 2003, 1630 posts, RR: 20
Reply 12, posted (1 year 12 months 1 day 6 hours ago) and read 4298 times:

Quoting AmericanAirFan (Reply 10):
I got really lucky while taking shots of an Allegiant MD-87 from its backside.

Nice catch!  

Quoting NWADC9 (Reply 11):
Why is this "whoop whoop" found on DC-9s and not MD-80s? Was there an improvement with the JT8D-200 series that did away with this sweet song?

I have heard it on several AA planes, although it seems to vary from one aircraft to another. Some are silent, while others are very pronounced.



B-52s don't take off. They scare the ground away.
User currently offlineboeingfixer From Canada, joined Jul 2005, 530 posts, RR: 0
Reply 13, posted (1 year 11 months 4 weeks 1 day 16 hours ago) and read 4091 times:

Quoting flashmeister (Reply 4):
What you're hearing is interference in the PA system caused by the ignitors firing.

To be technically correct what you are hearing is the ignition box recharging between firing the ignition plugs. The pause in the sound is the actual moment of ignition plug firing.

Cheers,

John



Cheers, John YYC
User currently offlineAccidentally From United States of America, joined Dec 2000, 643 posts, RR: 0
Reply 14, posted (1 year 11 months 3 weeks 6 days 2 hours ago) and read 3817 times:
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It's to do with the ignition system. Kinda like the quick ticking from a King Air's PT6. In that video you posted there's a video down below titled "Delta Airlines DC-9-51 Start-up, Takeoff, Cruise MKE-DTW Pt. 1/2" in which it is also evident.


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User currently offlineSPREE34 From United States of America, joined Jun 2004, 2246 posts, RR: 9
Reply 15, posted (1 year 11 months 3 weeks 4 days 3 hours ago) and read 3664 times:

Quoting boeingfixer (Reply 13):
To be technically correct what you are hearing is the ignition box recharging between firing the ignition plugs. The pause in the sound is the actual moment of ignition plug firing.

This. ^^^^^^^

You hear it in headsets in the cocpit too. 80s and later aircraft had better isolation of electricl noises from the audio equip. 400hz hum used to be common in AG comms and PA announcements. Hardly heard anymore.



I don't understand everything I don't know about this.
User currently offlineIAHFLYR From United States of America, joined Jun 2005, 4790 posts, RR: 22
Reply 16, posted (1 year 11 months 3 weeks 9 hours ago) and read 3373 times:

Quoting SPREE34 (Reply 15):
You hear it in headsets in the cocpit too. 80s and later aircraft had better isolation of electricl noises from the audio equip. 400hz hum used to be common in AG comms and PA announcements. Hardly heard anymore.



I still find it often on the AA Super 80 fleet more so than the DL MD88's.



Any views shared are strictly my own and do not a represent those of any former employer.
User currently offlineKingAir200 From United States of America, joined May 2006, 1611 posts, RR: 2
Reply 17, posted (1 year 11 months 2 weeks 6 days 14 hours ago) and read 3301 times:

Quoting SPREE34 (Reply 15):
You hear it in headsets in the cocpit too.

It seems to vary from ship to ship, but it can be quite loud over the ramp interphone as well.



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