Sponsor Message:
Aviation Technical / Operations Forum
My Starred Topics | Profile | New Topic | Forum Index | Help | Search 
L Recirc Fan & Light Dimmer - B757  
User currently offlineHAWK21M From India, joined Jan 2001, 31684 posts, RR: 56
Posted (1 year 9 months 2 weeks 1 day 15 hours ago) and read 2025 times:

On the B757 What is the connection electrically.....that with the left recirculation fan Unpowered, the Light dim function of the Indicator lights gets Inoperative.


Think of the brighter side!
5 replies: All unread, jump to last
 
User currently offlinefr8mech From United States of America, joined Sep 2005, 5489 posts, RR: 14
Reply 1, posted (1 year 9 months 2 weeks 1 day 14 hours ago) and read 1993 times:

Are you saying that when the L RECIRC Fan is turned off the master dim function on the flight deck is inop? Or just the INOP light on the switch?


When seconds count...the police are minutes away.
User currently offlinefr8mech From United States of America, joined Sep 2005, 5489 posts, RR: 14
Reply 2, posted (1 year 9 months 2 weeks 1 day 14 hours ago) and read 1986 times:

Hmmm, I never saw the connection before. I guess it's because the L RECIRC fan is always running.

A quick reading of the AMM:

Under normal conditions, 28v dc from the dim control circuit breaker energizes a power control relay which sends 28v dc to the dim control relays. The dim control relays are energized by the DIM position of the control switch providing a ground.
When air conditioning airflow sensors or rack overheat sensors detect insufficient airflow for equipment cooling, or power is removed from the recirculation fan, a ground is removed from the power control relay by the air conditioning trim valve controller. The power control relay then removes 28v dc from the dim control relays and disables the automatic dimming function. This ensures all warning and caution annunciations are visible even if cooling is lost.

[Edited 2013-01-10 00:59:03]


When seconds count...the police are minutes away.
User currently offlineHAWK21M From India, joined Jan 2001, 31684 posts, RR: 56
Reply 3, posted (1 year 9 months 1 week 6 days 4 hours ago) and read 1778 times:

Quoting fr8mech (Reply 1):
Are you saying that when the L RECIRC Fan is turned off the master dim function on the flight deck is inop? Or just the INOP light on the switch?

No just power supply off thru CB.Then lights dont get dimmed selectable.

Quoting fr8mech (Reply 2):
The dim control relays are energized by the DIM position of the control switch providing a ground.

Thanks.
Any reason for this circuitry



Think of the brighter side!
User currently offlinefr8mech From United States of America, joined Sep 2005, 5489 posts, RR: 14
Reply 4, posted (1 year 9 months 1 week 5 days 8 hours ago) and read 1660 times:

Quoting HAWK21M (Reply 3):
Any reason for this circuitry

The AMM says:

Quoting fr8mech (Reply 2):
This ensures all warning and caution annunciations are visible even if cooling is lost.



When seconds count...the police are minutes away.
User currently offlineboeing767mech From United States of America, joined Dec 2000, 1029 posts, RR: 3
Reply 5, posted (1 year 9 months 1 week 5 days 8 hours ago) and read 1650 times:

Quoting fr8mech (Reply 4):
Quoting HAWK21M (Reply 3):Any reason for this circuitry
The AMM says:

Quoting fr8mech (Reply 2):This ensures all warning and caution annunciations are visible even if cooling is lost.

I have been told with smoke in the cockpit you turn off the Left Hand Recirc fan, that is a reason why the warning lights go bright when turned off



Never under-estimate the predictably of stupidty
Top Of Page
Forum Index

Reply To This Topic L Recirc Fan & Light Dimmer - B757
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...
MEL Query - B757. posted Wed Jan 9 2013 22:50:23 by HAWK21M
Gyroscopic Effect Of Turbo Fan Engines posted Sun Jan 6 2013 23:10:05 by dhawald3
Pack Light 737 posted Sun Jan 6 2013 05:22:38 by smartt1982
CFM 56 Fan Blade Ice Shedding posted Sat Jan 5 2013 10:08:59 by abnormal
AA738: Adaptive Trailing Edges/Var Area Fan Nozzle posted Fri Dec 28 2012 02:13:24 by faro
No Varable Area Fan Nozzles For CSeries...Why? posted Thu Dec 20 2012 21:58:59 by JoeCanuck
Unducted Fan Engine posted Thu Dec 20 2012 12:03:28 by surajit001
B757 Emergency Exit Sign Question posted Tue Nov 6 2012 08:18:08 by hagiograph
Static Electrically Induced Light. posted Mon Jul 9 2012 03:09:59 by HAWK21M
Fan Blades: Titanium Vs Composite posted Fri Jun 22 2012 12:50:52 by imiakhtar

Sponsor Message:
Printer friendly format