I must admit to finding the PSEU light difficult to get my head around, and yet it should be so simple. My interpretation is that if you get a PSEU light on recall only, you can fly - "pilot dispatch" in your terminology. You would put it in the book after landing and it would be up to the engineers to decide if it was "engineer dispatch" after that.
FYI A new improved & perhaps less "buggy" PSEU is due for release this month (Oct 06). See 737NG-FTD-32-04006, copied below in case you do not have access to these.
Regards
S&L
Revision Description:
Modified BACKGROUND, STATUS and FINAL ACTION sections of the FTD.
Applicability:
All model 737-600/-700/-800/-900/-BBJ airplanes.
Description:
Operators have reported schedule interruptions due to PSEU light illumination. Often, a check of the PSEU non-volatile memory (NVM) reveals no faults.
The PSEU stores detected faults in the "existing faults" in the NVM. "Existing faults" are transferred to "fault history" when the airplane is in "air".
The PSEU classifies faults as "NO DISPATCH", causing the PSEU light to illuminate spontaneously, or as “DISPATCH” causing the light to illuminate only upon Master Caution “RECALL”.
The PSEU light will illuminate only when there is a fault stored in the current fault list and the airplane is on the ground.
A PSEU light which illuminates as a result of a "DISPATCH" fault will extinguish upon Master Caution Reset, per MMEL 2-32-17. A "DISPATCH" fault does not require immediate corrective action. A "NO DISPATCH" fault will not reset, and requires corrective action prior to dispatch.
Background:
The -4 PSEU records external "active" or "latched" faults (transfer from the "current fault list" to "fault history" in the non-volatile memory NVM), when:
- The PSEU senses a transition from Ground to Air “AND” all eight service, entry, and access doors are closed.
If the fault is intermittent, or there is a “reset”, manual or due to power up, the condition may not record.
Maintenance crews should read out each fault stored in the "current fault" NVM prior to a "reset latches" or a "self test" or "power up".
The -5 PSEU fault recording logic has been modified to record in NVM when:
- Either engine is running “OR” all eight service, entry, and access doors are closed.
The following are the eight door signals used for the fault record logic for either -4 or -5 PSEU:
Fwd Ser Lkd
Aft Ser Lkd
Fwd Ent Lkd
Aft Ent Lkd
Fwd Cargo Lkd
Aft Cargo Lkd
EE Acc Lkd
Fwd Acc Lkd
In addition, Internal PSEU faults are always be recorded in the NVM when the fault is detected.
Boeing and BAE Systems are working to improve the fault detection and recording logic. The following areas have been identified for improvement:
1: Add Maintenance Air Mode to Prevent Faults due to Maintenance Actions
2: Revise fault history recording logic to include faults detected On Ground to aid troubleshooting
3: Annunciate Dispatchable Faults Automatically on Landing
4: Prevent False Sensor Faults due to one-wheel landing
5: Inhibit external fault indications when internal faults are detected
6: Increase landing flap signal fault detection time
7: Correct proximity sensor gap rigging tool for FWD Galley Door
8: Add shop data to fault record to aid analysis of in-service problems
Status:
Line Position 2086 is scheduled to incorporate the first -5 PSEU. Line Position 2086 is scheduled for delivery on 25 October 2006.
The Component Service Bulletin is scheduled for release in October also.
Interim Action:
Operators should ensure that upon return to gate due to a PSEU light, prior to performing any reset function which may cause a reset of the faults, the “existing fault's” NVM be interrogated to read out and manually record any and all fault records which may be found in the “existing fault's” NVM. This practice will allow for appropriate troubleshooting, and will prevent repeats of the same fault.
The process to read out the contents of fault records in NVM is available in the ref FIM Figure 202 (Existing Fault Data), or Figure 203 (Fault History Data).
Final Action:
The -5 upgrade to the P/N 285A1600-4 MOD A PSEU will incorporate the above changes. Prior PSEU versions will require to be updated to -4 MOD A prior to incorporation of -5 software.
The -5 upgrade is purely a software upgrade.
BAE Systems will issue a Component Service Bulletin which has been submitted for review and is scheduled for release in October 2006, after the first airplane is delivered.
A Service Letter will follow the Component Service Bulletin.
BAE Systems Repair Centers will begin upgrading units at that time.
Operator Action:
Operators may wish to begin planning the PSEU module upgrade schedule to -5.
Operators should note that upgrade capacity is limited and will require schedule coordination.
Part Information:
Proximity Switch Electronics Unit (PSEU) P/N 285A1600-4 MOD A will be upgraded to P/N 285A1600-5 per Service Bulletin not yet defined, scheduled to be released October 2006.