Sponsor Message:
Aviation Technical / Operations Forum
My Starred Topics | Profile | New Topic | Forum Index | Help | Search 
"Finger Tapping" Sound On MD-88-What Is It?  
User currently offlineDeltaGator From United States of America, joined Sep 2005, 6341 posts, RR: 13
Posted (8 years 2 months 2 weeks 6 days 19 hours ago) and read 6050 times:

I flew home to ATL from MLB this afternoon (flight 688) on a Delta MD-88 (reg. N907DE) and I heard a sound I've never heard before. After we backed away from the gate and started to taxi to the runway I heard what sounded like very loud finger tapping. I had headphones on and at first thought I had a nervous passenger behind me tapping their fingers on my seat. It was more of a "thumping" sound kind of like it would sound like if you tapped you fingers on your leather recliner at home.

I was about to turn around and say something to him but when I took my headphones off I could better make out the sound coming from in front of me and down and to the left. I was in row 3 of 1st class on the port side of the plane and there was nobody in the first row in front of me except the stewardesses on the complete other side of the head sitting in their seats by the door.

I was thinking it was something on the taxiway. Perhaps centerline reflectors but it came and went and continued even when off the centerline of the taxiway. It finally went away after we rolled onto the runway.

I'm just curious as to what it was since I have spent many hours in the Maddog and never heard that sound. Any ideas out there folks? I surely hope nobody trapped in the wheelwell but who knows.


"If you can't delight in the misery of others then you don't deserve to be a college football fan."
10 replies: All unread, jump to last
 
User currently offlineDougloid From , joined Dec 1969, posts, RR:
Reply 1, posted (8 years 2 months 2 weeks 6 days 19 hours ago) and read 6042 times:

Have you been watching old episodes of Twilight Zone?

User currently offlineDeltaGator From United States of America, joined Sep 2005, 6341 posts, RR: 13
Reply 2, posted (8 years 2 months 2 weeks 6 days 18 hours ago) and read 6034 times:

"There's something (insert Shatner pause here) on (another pause) the wing!"

No, I haven't seen that in a while. Didn't even think of that one until you said it.



"If you can't delight in the misery of others then you don't deserve to be a college football fan."
User currently offlineDeltaGuy From , joined Dec 1969, posts, RR:
Reply 3, posted (8 years 2 months 2 weeks 6 days 18 hours ago) and read 6028 times:

Just to hazard a guess, but perhaps just some aggressive expansion joints in the taxiway tarmac? I haven't been to MLB in a year, so I'm not sure of the condition of the pavement there, but it could have been something on the jet rattling as a result of it.

DeltaGuy


User currently offlineDeltaGator From United States of America, joined Sep 2005, 6341 posts, RR: 13
Reply 4, posted (8 years 2 months 2 weeks 6 days 17 hours ago) and read 5998 times:

I thought that as well and looked out thinking it was the joints but the tapping didn't line up. Looked like a bunch of MLB was done in asphalt as well so not a huge amount of joints in the taxiways.


"If you can't delight in the misery of others then you don't deserve to be a college football fan."
User currently offlineBohica From United States of America, joined Feb 2004, 2631 posts, RR: 0
Reply 5, posted (8 years 2 months 2 weeks 6 days 15 hours ago) and read 5967 times:

Quoting Dougloid (Reply 1):
Have you been watching old episodes of Twilight Zone?

LOL...I was thinking exactly the same thing.  bigthumbsup 


User currently offlineMX757 From United States of America, joined Aug 2005, 628 posts, RR: 12
Reply 6, posted (8 years 2 months 2 weeks 6 days 10 hours ago) and read 5916 times:

It was a damn gremlin in the E&E bay tapping his chin trying figure out what system he is going to f*** with today. Didn't you hear about it? Every MD-80 has one the little bastards running around in them! The gremlin's only goal in life is to make a tech's (like me) life pure hell!  devil 


On a more serious note, I thought about what you were hearing and all could think was that I agree with your conclusion. The nose tires were probably hitting the taxiway center lights/reflectors. Either that or one of or both nose tires had a flat spot.

I have a lot of experience on DC-9/MD-80's and I can't think of anything in the a/c's forward section that would make a tapping noise you heard. I've taxied numerous times in several types of a/c and when you run over one of those taxi lights it does make a kind of thud that is audible in the cockpit and the forward section of the a/c.



Is it broke...? Yeah I'll fix it.
User currently offlineNonfirm From United States of America, joined Sep 2005, 434 posts, RR: 0
Reply 7, posted (8 years 2 months 2 weeks 6 days 9 hours ago) and read 5900 times:

Quoting MX757 (Reply 6):
It was a damn gremlin in the E&E bay tapping his chin trying figure out what system he is going to f*** with today. Didn't you hear about it? Every MD-80 has one the little bastards running around in them! The gremlin's only goal in life is to make a tech's (like me) life pure hell!

I like to call him the job security gremlin.


User currently offlineLongbowPilot From United States of America, joined Jan 2005, 577 posts, RR: 4
Reply 8, posted (8 years 2 months 2 weeks 6 days 4 hours ago) and read 5847 times:
Support Airliners.net - become a First Class Member!

Gator, it is a phenomina within the flaps of the MD88/90s.

Basically the flaps are fully retracted and there is a slight amount of pressure over what is needed to hold those flaps up. so you hear the relief valve in the flap system popping when the pressure is too great.

The mechanic explained that it is something that takes a short fix in ATL, but nothing to delay or MX the flight.


User currently offlineOkie From United States of America, joined Jul 2003, 2854 posts, RR: 3
Reply 9, posted (8 years 2 months 2 weeks 6 days 4 hours ago) and read 5847 times:

Quoting DeltaGator (Thread starter):
I'm just curious as to what it was since I have spent many hours in the Maddog and never heard that sound. Any ideas out there folks? I surely hope nobody trapped in the wheelwell but who knows.

Been there heard that.
It was explained to me by a jump-riding Mad Dog Captain sitting by me when I questioned him about that noise and seems to make sense.
There is an aux electric hydraulic pump and accumulator in system that pressures the control system when engines (or engine if single engine taxi) are at idle as the slow turning engine/engines do not provide all the quanity of hydraulic volume required. (I also assume that this pump could be used in an emergency)

The sound you hear is the check valve closing when the aux system puts hydraulic fluid in the system and recloses preventing back flow. I have been on some 80's where that pump has been pretty noisy starting and stopping often as soon as it charges the accumulator and system demands are met. The noise stops as soon as the engines spool up for take-off and flight.

While I am not a tail number watcher I have noticed that newer birds are more likely to make the tapping sound while the older birds you seem to hear the whirling of the pump starting and stopping, possibly they have changed their motor/pump design with time.

Okie


User currently offlineLongbowPilot From United States of America, joined Jan 2005, 577 posts, RR: 4
Reply 10, posted (8 years 2 months 2 weeks 4 days 8 hours ago) and read 5697 times:
Support Airliners.net - become a First Class Member!

Well, I was close right Big grin

Top Of Page
Forum Index

Reply To This Topic "Finger Tapping" Sound On MD-88-What Is It?
Username:
No username? Sign up now!
Password: 


Forgot Password? Be reminded.
Remember me on this computer (uses cookies)
  • Tech/Ops related posts only!
  • Not Tech/Ops related? Use the other forums
  • No adverts of any kind. This includes web pages.
  • No hostile language or criticizing of others.
  • Do not post copyright protected material.
  • Use relevant and describing topics.
  • Check if your post already been discussed.
  • Check your spelling!
  • DETAILED RULES
Add Images Add SmiliesPosting Help

Please check your spelling (press "Check Spelling" above)


Similar topics:More similar topics...
Speed Brakes On MD-88. What Did I See? posted Thu Apr 27 2006 17:25:32 by Mastropiero
Door Seals On MD-88 And Others posted Fri Nov 19 2004 06:48:55 by Monorail
What Is "Sync" On A DC9-50 posted Sun Jun 23 2002 03:42:46 by BR715-A1-30
What Is A "steam" Gauge? posted Thu Oct 26 2006 10:10:44 by Speedracer1407
What Is "cross Country"? posted Thu Dec 22 2005 11:24:30 by Tbar220
What Is The Function Of "prop Sync"? posted Thu Aug 25 2005 22:48:17 by ArniePie
"Licensed Aircraft Engineer", What Is It Exactly? posted Fri Aug 5 2005 01:33:35 by Sabena332
What Is An "aircraft Stick Shaker" posted Wed Jun 29 2005 01:04:06 by ETStar
What Is That Little Black "thing"? posted Tue Jul 6 2004 17:37:04 by Qb001
What Is An "e-enabled" Airline? posted Tue May 4 2004 03:04:59 by Varmit

Sponsor Message:
Printer friendly format