Georgetown
Topic Author
Posts: 341
Joined: Wed Dec 28, 2005 12:50 pm

Strange sound on 737-800

Tue Jul 11, 2017 4:19 am

Hi All-

Heard a new sound on a 737-800 last night a few minutes into flight that I haven't heard before. For context, I'm a very very frequent flyer and am on a UA 737-800/900 at least three times per week. I usually choose to sit in row 4, right hand side, which is where I was last night. I only give this information to provide a little bit of credence to the statement that I'm used to the vast majority of sounds these planes make after takeoff: nose gear coming back into the well, flaps/slats retracting, etc etc.

About three or four minutes after takeoff last night a very loud hum began that increased in pitch over the course of about a minute until it went away. If I didn't know any better, I would have said it was an engine starting up (very similar sound), but it obviously wasn't that. Had a number of folks looking around with puzzled looks. Flight was otherwise perfectly normal.

Any of the experts or 737 drivers have any idea what I heard? Thanks in advance!
Let's go Hoyas!
 
7673mech
Posts: 332
Joined: Tue Mar 30, 2004 10:10 am

Re: Strange sound on 737-800

Tue Jul 11, 2017 5:31 am

From a maintenance point of view, maybe a door seal that was seating as the airplane pressurized. Sometimes they hum, sometimes they scream. Just a thought.
 
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DL_Mech
Posts: 2154
Joined: Fri Feb 18, 2000 7:48 am

Re: Strange sound on 737-800

Tue Jul 11, 2017 10:58 am

+1 on the door seal. Probably the cargo door.
This plane is built to withstand anything... except a bad pilot.
 
Georgetown
Topic Author
Posts: 341
Joined: Wed Dec 28, 2005 12:50 pm

Re: Strange sound on 737-800

Tue Jul 11, 2017 2:09 pm

Thanks for the replies! That would make sense as I was sitting over the cargo door. Didn't think of that.
Let's go Hoyas!
 
AA737-823
Posts: 5178
Joined: Wed Mar 01, 2000 11:10 am

Re: Strange sound on 737-800

Fri Jul 14, 2017 1:15 am

Greetings from 737-NG maintenance land.
Add me to the list of people that suspect a door seal. They're notoriously noisy.
As much as you fly, I suspect you'll hear more of them in the future!
As a rule, any hum that increases in pitch with cabin pressure is USUALLY related to sealing. I'm sure someone will come after me and point out twelve exceptions, but it's a general truth!
 
Georgetown
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Posts: 341
Joined: Wed Dec 28, 2005 12:50 pm

Re: Strange sound on 737-800

Fri Jul 14, 2017 5:30 am

Much appreciated AA! I'm surprised I haven't heard it before - maybe I have and it wasn't as pronounced as this one was. I guess a follow up question: I assume there's no imminent issue that would cause a plane to turn around and head back? Always love learning new info!
Let's go Hoyas!
 
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thewizbizman
Posts: 92
Joined: Wed May 03, 2017 4:15 pm

Re: Strange sound on 737-800

Sat Jul 15, 2017 11:25 am

What kind of job do you have that allows you to fly 3 times a week and where do I get it.
 
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Starlionblue
Posts: 17983
Joined: Fri Feb 27, 2004 9:54 pm

Re: Strange sound on 737-800

Sat Jul 15, 2017 1:18 pm

thewizbizman wrote:
What kind of job do you have that allows you to fly 3 times a week and where do I get it.


Pilot? ;)

Jokes aside, I used to fly around 100 times a year working in a sales organisation. It's not for everyone but some people enjoy it.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
fr8mech
Posts: 6878
Joined: Mon Sep 26, 2005 9:00 am

Re: Strange sound on 737-800

Sat Jul 15, 2017 2:52 pm

Georgetown wrote:
I guess a follow up question: I assume there's no imminent issue that would cause a plane to turn around and head back?


I guess if the sound didn't go away and enough people complained the flight crew would write it up at the next station. Where, I'm sure, maintenance would inspect and clean the seal and sealing area and call it good.

Now, if there were an associated pressurization issue...things may go a bit differently.

But, in reality, a seal buzzing during the pressurization cycle is common and will normally go away well before cruising PSID.
When seconds count...the police are minutes away.
 
Georgetown
Topic Author
Posts: 341
Joined: Wed Dec 28, 2005 12:50 pm

Re: Strange sound on 737-800

Sat Jul 15, 2017 8:39 pm

thewizbizman wrote:
What kind of job do you have that allows you to fly 3 times a week and where do I get it.


I work in finace, advising companies on mergers and acquisitions, equity financings, etc. Translates into a lot of in person meetings, and in turn, a lot of airplanes. I love flying but trust me after a while it's far from glamorous.
Let's go Hoyas!

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