Boeing 717 / MD80 question

Cherokee_Cruiser · September 2nd, 2004, 10:21

Hey guys,
This question is mainly for the 717, although I'm sure it applies to the MD80 as well. I was recently on an Airtran flight on a 717, sitting in 30A. That window seat has no view outside: just the engine. Basically after pushback when the engines started, all throughout taxi, the engines were loud!!! All that while, the engine sound was resonating in the back of the aircraft. But right when power was applied for takeoff, that sound died out, and was replaced by the quiet hum (MUCH quieter) that I'm used to on the 717. Any idea why the aircraft engines are louder when on the ground taxiing to the runway?

Also, I've noticed this is only true when you're sitting in the back of the airplane. Sitting in the middle and up front, there was no loud noise as described.

Doug Taylor · September 2nd, 2004, 10:24

Resonate frequencies.

JEP · September 2nd, 2004, 10:28

[ QUOTE ]
Sitting in the middle and up front, there was no loud noise as described.

[/ QUOTE ]

That's because you are farther away from the engine. [img]/ubbthreads/images/graemlins/grin.gif[/img] I avoid at all costs the back seat on a DC-9 variety airplane.

Cherokee_Cruiser · September 2nd, 2004, 11:28

Thanks for the responses!

flyover · September 2nd, 2004, 13:16

[ QUOTE ]
Resonate frequencies.

[/ QUOTE ]

The other big factor is all the noise coming through the doors. When power is pushed up the cabin starts pressurizing and the doors seal. This can make a major difference in noise level. Sometimes there is such a gap in the door seals it sounds like the door is open until it pressurizes.

chrisesp · September 2nd, 2004, 19:20

I know the 757/767, have a very high pitched whine when idiling, that whine is enough to make me miserable, but when they are at full power they sound much easier to deal with? [img]/ubbthreads/images/graemlins/grin.gif[/img]

[img]/ubbthreads/images/graemlins/blush.gif[/img]I guess since we are on the subject, why is it that the MD-80 makes a really loud "pop" sound when the engines start, I have noticed that no other airplanes do that/are that loud. Any body know why? [img]/ubbthreads/images/graemlins/spin2.gif[/img]

mtsu_av8er · September 2nd, 2004, 19:43

Man, I love that whine!!!

Maximillian_Jenius · September 3rd, 2004, 01:34

[ QUOTE ]
Man, I love that whine!!!

[/ QUOTE ]

Yup me too...gotta love these new high ratio bypass engines [img]/ubbthreads/images/graemlins/spin2.gif[/img]

Matthew

gurisudenko · September 3rd, 2004, 03:08

My favorite seat on any aircraft, as a passenger, is right next to the wing and at the window. I love watching the control surfaces being adjusted all through the flight, but I never thought about the obvious - it was a lot louder right next to the engine then anywhere else.

I decided to host a marathon of The Young Ones on a flight to Vegas, for my extremely nervous fellow passenger. He liked the show and it got his mind off everything that worried him. I had the volume turned up all the way on my laptop - and this thing has some awesome stereo speakers - but I could barely hear it! All of a sudden, a passenger behind me tapped me on the shoulder, pretty pissed off, and told me that the show was "Way too loud!"

I was puzzled. How could it be "Way too loud!" when I could barely hear it? ....Yeah, then came my lesson about how sound travels, and when you sit right next to loud things, it's loud. [img]/ubbthreads/images/graemlins/buck.gif[/img] The crew was lucky that I didn't stand up and yell, letting them know right then of my phenomenal discovery!

Always love the engines' various sounds during flights. The MD-80 was nice. Has anyone noticed how the Embraer 135 sounds like it's underwater?!

/end of tangent

RiddlePilot · September 3rd, 2004, 03:11

[ QUOTE ]
I decided to host a marathon of The Young Ones on a flight to Vegas

[/ QUOTE ]

The Young Ones?! Talk about good obscure British comedy. I approve. [img]/ubbthreads/images/graemlins/grin.gif[/img]

flyover · September 3rd, 2004, 09:18

[ QUOTE ]
[img]/ubbthreads/images/graemlins/blush.gif[/img]I guess since we are on the subject, why is it that the MD-80 makes a really loud "pop" sound when the engines start, I have noticed that no other airplanes do that/are that loud. Any body know why?

[/ QUOTE ]

I've got about 5,000 hours on the airplane (in the quiet end) and didn't know that. If it's happening consistently and you hear it in the back, I would have to guess it's one of the many valves that open and close during a start cycle.

mtsu_av8er · September 3rd, 2004, 10:26

He may just be refering to light-off....

It's sometimes more pronounced than at other times.

flyover · September 3rd, 2004, 11:09

[ QUOTE ]
He may just be refering to light-off....

It's sometimes more pronounced than at other times.

[/ QUOTE ]

That's a good point. Probably right. Some engines do go with a pop, particuarly the JT-8 series.

I think you win the prize.

Dave

Maximillian_Jenius · September 3rd, 2004, 13:55

[ QUOTE ]
He may just be refering to light-off....

It's sometimes more pronounced than at other times.

[/ QUOTE ]

What exactly is "light off"....is that when the underwing mounted lights retract on MD-80/90 series aircraft?

Matthew

Doug Taylor · September 3rd, 2004, 13:57

Right after you 'introduce' fuel to the engine, it's when combustion begins during the engine start.

kellwolf · September 3rd, 2004, 14:21

[ QUOTE ]
I decided to host a marathon of The Young Ones on a flight to Vegas, for my extremely nervous fellow passenger.

[/ QUOTE ]

Haven't watched that in a long time. "Rick! I got six pair o' 'ands!" [img]/ubbthreads/images/graemlins/smile.gif[/img]

September 2nd, 2004, 10:21	#1
Cherokee_Cruiser Senior Member Join Date: Sep 2001 Posts: 1,419	Boeing 717 / MD80 question Hey guys, This question is mainly for the 717, although I'm sure it applies to the MD80 as well. I was recently on an Airtran flight on a 717, sitting in 30A. That window seat has no view outside: just the engine. Basically after pushback when the engines started, all throughout taxi, the engines were loud!!! All that while, the engine sound was resonating in the back of the aircraft. But right when power was applied for takeoff, that sound died out, and was replaced by the quiet hum (MUCH quieter) that I'm used to on the 717. Any idea why the aircraft engines are louder when on the ground taxiing to the runway? Also, I've noticed this is only true when you're sitting in the back of the airplane. Sitting in the middle and up front, there was no loud noise as described.

September 2nd, 2004, 10:24	#2
Doug Taylor Agent Smith Join Date: Dec 1969 Location: KSDL Posts: 39,825 Blog Entries: 1	Re: Boeing 717 / MD80 question Resonate frequencies.

September 2nd, 2004, 10:28	#3
JEP Moderator Join Date: Jun 2003 Location: Eden Prairie, MN (KFCM) (KMSP) Posts: 10,556 Blog Entries: 1	Re: Boeing 717 / MD80 question [ QUOTE ] Sitting in the middle and up front, there was no loud noise as described. [/ QUOTE ] That's because you are farther away from the engine. [img]/ubbthreads/images/graemlins/grin.gif[/img] I avoid at all costs the back seat on a DC-9 variety airplane.

September 2nd, 2004, 11:28	#4
Cherokee_Cruiser Senior Member Join Date: Sep 2001 Posts: 1,419	Re: Boeing 717 / MD80 question Thanks for the responses!

September 2nd, 2004, 13:16	#5
flyover Old Skool Join Date: Mar 2004 Location: Georgia Posts: 3,389	Re: Boeing 717 / MD80 question [ QUOTE ] Resonate frequencies. [/ QUOTE ] The other big factor is all the noise coming through the doors. When power is pushed up the cabin starts pressurizing and the doors seal. This can make a major difference in noise level. Sometimes there is such a gap in the door seals it sounds like the door is open until it pressurizes.

September 2nd, 2004, 19:20	#6
chrisesp Senior Member Join Date: Mar 2004 Location: Bay Area, CA Posts: 386	Re: Boeing 717 / MD80 question I know the 757/767, have a very high pitched whine when idiling, that whine is enough to make me miserable, but when they are at full power they sound much easier to deal with? [img]/ubbthreads/images/graemlins/grin.gif[/img] [img]/ubbthreads/images/graemlins/blush.gif[/img]I guess since we are on the subject, why is it that the MD-80 makes a really loud "pop" sound when the engines start, I have noticed that no other airplanes do that/are that loud. Any body know why? [img]/ubbthreads/images/graemlins/spin2.gif[/img]

September 2nd, 2004, 19:43	#7
mtsu_av8er Old Skool Join Date: Dec 2002 Location: Utopia Posts: 12,403	Re: Boeing 717 / MD80 question Man, I love that whine!!!

September 3rd, 2004, 01:34	#8
Maximillian_Jenius Old Skool Join Date: Nov 2003 Location: KPHX, KFFZ, KIWA Posts: 18,661	Re: Boeing 717 / MD80 question [ QUOTE ] Man, I love that whine!!! [/ QUOTE ] Yup me too...gotta love these new high ratio bypass engines [img]/ubbthreads/images/graemlins/spin2.gif[/img] Matthew

September 3rd, 2004, 03:08	#9
gurisudenko Junior Member Join Date: Aug 2004 Location: Saint Cloud, MN USA Posts: 260	Re: Boeing 717 / MD80 question My favorite seat on any aircraft, as a passenger, is right next to the wing and at the window. I love watching the control surfaces being adjusted all through the flight, but I never thought about the obvious - it was a lot louder right next to the engine then anywhere else. I decided to host a marathon of The Young Ones on a flight to Vegas, for my extremely nervous fellow passenger. He liked the show and it got his mind off everything that worried him. I had the volume turned up all the way on my laptop - and this thing has some awesome stereo speakers - but I could barely hear it! All of a sudden, a passenger behind me tapped me on the shoulder, pretty pissed off, and told me that the show was "Way too loud!" I was puzzled. How could it be "Way too loud!" when I could barely hear it? ....Yeah, then came my lesson about how sound travels, and when you sit right next to loud things, it's loud. [img]/ubbthreads/images/graemlins/buck.gif[/img] The crew was lucky that I didn't stand up and yell, letting them know right then of my phenomenal discovery! Always love the engines' various sounds during flights. The MD-80 was nice. Has anyone noticed how the Embraer 135 sounds like it's underwater?! /end of tangent

September 3rd, 2004, 03:11	#10
RiddlePilot Senior Member Join Date: Apr 2003 Location: Prescott, AZ Posts: 928	Re: Boeing 717 / MD80 question [ QUOTE ] I decided to host a marathon of The Young Ones on a flight to Vegas [/ QUOTE ] The Young Ones?! Talk about good obscure British comedy. I approve. [img]/ubbthreads/images/graemlins/grin.gif[/img]

September 3rd, 2004, 09:18	#11
flyover Old Skool Join Date: Mar 2004 Location: Georgia Posts: 3,389	Re: Boeing 717 / MD80 question [ QUOTE ] [img]/ubbthreads/images/graemlins/blush.gif[/img]I guess since we are on the subject, why is it that the MD-80 makes a really loud "pop" sound when the engines start, I have noticed that no other airplanes do that/are that loud. Any body know why? [/ QUOTE ] I've got about 5,000 hours on the airplane (in the quiet end) and didn't know that. If it's happening consistently and you hear it in the back, I would have to guess it's one of the many valves that open and close during a start cycle.

September 3rd, 2004, 10:26	#12
mtsu_av8er Old Skool Join Date: Dec 2002 Location: Utopia Posts: 12,403	Re: Boeing 717 / MD80 question He may just be refering to light-off.... It's sometimes more pronounced than at other times.

September 3rd, 2004, 11:09	#13
flyover Old Skool Join Date: Mar 2004 Location: Georgia Posts: 3,389	Re: Boeing 717 / MD80 question [ QUOTE ] He may just be refering to light-off.... It's sometimes more pronounced than at other times. [/ QUOTE ] That's a good point. Probably right. Some engines do go with a pop, particuarly the JT-8 series. I think you win the prize. Dave

September 3rd, 2004, 13:55	#14
Maximillian_Jenius Old Skool Join Date: Nov 2003 Location: KPHX, KFFZ, KIWA Posts: 18,661	Re: Boeing 717 / MD80 question [ QUOTE ] He may just be refering to light-off.... It's sometimes more pronounced than at other times. [/ QUOTE ] What exactly is "light off"....is that when the underwing mounted lights retract on MD-80/90 series aircraft? Matthew

September 3rd, 2004, 13:57	#15
Doug Taylor Agent Smith Join Date: Dec 1969 Location: KSDL Posts: 39,825 Blog Entries: 1	Re: Boeing 717 / MD80 question Right after you 'introduce' fuel to the engine, it's when combustion begins during the engine start.

September 3rd, 2004, 14:21	#16
kellwolf Old Skool Join Date: Jun 2003 Location: Memphis, TN Posts: 13,252	Re: Boeing 717 / MD80 question [ QUOTE ] I decided to host a marathon of The Young Ones on a flight to Vegas, for my extremely nervous fellow passenger. [/ QUOTE ] Haven't watched that in a long time. "Rick! I got six pair o' 'ands!" [img]/ubbthreads/images/graemlins/smile.gif[/img]

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