Flight crew of B737-900 are uncertain of operational procedure for air conditioning trim air system ...

Attributes
ACN	626509
Time
Date	200408
Day	Wed
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : zzz.airport
State Reference	US
Altitude	agl single value : 0
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	B737-900
Operating Under FAR Part	Part 121
Flight Phase	ground : parked ground : preflight
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
ASRS Report	626509
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
ASRS Report	626517
Events
Anomaly	aircraft equipment problem : less severe other anomaly other
Independent Detector	other flight crewa
Resolutory Action	none taken : anomaly accepted other
Consequence	other
Factors
Maintenance	performance deficiency : logbook entry
Supplementary
Problem Areas	Maintenance Human Performance FAA Aircraft
Primary Problem	Aircraft

Narrative:

I was given an airplane today. It had a single MEL on the release for the trim air system. This is the most confusing MEL I have been confronted with to date. We checked every page of the MEL thoroughly. We spoke with maintenance numerous times. First I was assured that the right pack and right recirculating fans should be positioned to 'high' and 'off.' next I was told to operate the system normally, just not to climb above FL250. Then I found that the high/off method was the only one that would work and keep the equipment cooling exhaust 'off' light off. Then there is the limitation in the flight handbook to not operate a pack in 'high' for takeoff, approach, or landing. Attempting to cover all the bases is practically impossible. This MEL needs attention. I would recommend a group meeting with the maintenance controllers involved, flight operations and a B737 instructor or two to hash this out. Supplemental information from acn 626517: in the end, after numerous discussions with maintenance, we flew the aircraft with both packs in 'automatic' for takeoff, approach, and landing, and placed the right pack to 'high' for all other phases of flight. However, there is no mention of this confign in either applicable MEL for operations procedures, only in the maintenance procedures. Again, very confusing.

Original NASA ASRS Text

Title: FLT CREW OF B737-900 ARE UNCERTAIN OF OPERATIONAL PROC FOR AIR CONDITIONING TRIM AIR SYS MEL ITEM.

Narrative: I WAS GIVEN AN AIRPLANE TODAY. IT HAD A SINGLE MEL ON THE RELEASE FOR THE TRIM AIR SYS. THIS IS THE MOST CONFUSING MEL I HAVE BEEN CONFRONTED WITH TO DATE. WE CHKED EVERY PAGE OF THE MEL THOROUGHLY. WE SPOKE WITH MAINT NUMEROUS TIMES. FIRST I WAS ASSURED THAT THE R PACK AND R RECIRCULATING FANS SHOULD BE POSITIONED TO 'HIGH' AND 'OFF.' NEXT I WAS TOLD TO OPERATE THE SYS NORMALLY, JUST NOT TO CLB ABOVE FL250. THEN I FOUND THAT THE HIGH/OFF METHOD WAS THE ONLY ONE THAT WOULD WORK AND KEEP THE EQUIP COOLING EXHAUST 'OFF' LIGHT OFF. THEN THERE IS THE LIMITATION IN THE FLT HANDBOOK TO NOT OPERATE A PACK IN 'HIGH' FOR TKOF, APCH, OR LNDG. ATTEMPTING TO COVER ALL THE BASES IS PRACTICALLY IMPOSSIBLE. THIS MEL NEEDS ATTN. I WOULD RECOMMEND A GROUP MEETING WITH THE MAINT CTLRS INVOLVED, FLT OPS AND A B737 INSTRUCTOR OR TWO TO HASH THIS OUT. SUPPLEMENTAL INFO FROM ACN 626517: IN THE END, AFTER NUMEROUS DISCUSSIONS WITH MAINT, WE FLEW THE ACFT WITH BOTH PACKS IN 'AUTO' FOR TKOF, APCH, AND LNDG, AND PLACED THE R PACK TO 'HIGH' FOR ALL OTHER PHASES OF FLT. HOWEVER, THERE IS NO MENTION OF THIS CONFIGN IN EITHER APPLICABLE MEL FOR OPS PROCS, ONLY IN THE MAINT PROCS. AGAIN, VERY CONFUSING.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.

Flight crew of B737-900 are uncertain of operational procedure for air conditioning trim air system MEL item.