Service difficulty report · Adiru · Boeing 737824

Difficulty date
March 17, 2024
Submitted
March 20, 2024
Operation
Air carrier
Aircraft
N18223
Make and model
Boeing 737824
Aircraft serial
28932
Aircraft time
76,547 hours, 28,128 cycles
Part
Adiru
Part number
HG2050AC11
Part serial
56082702
Condition
Intermittent
Location
E/E Bay E5 Rack
Part time
28,068 hours, 10,540 cycles
Stage of operation
DE
How discovered
O
Nature of condition
N
Precautionary procedure
B

As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.

What was found

IAS DISAGREE ON PDF. F/O AIRSPEED FROZEN AT 257KTS. DEBRIEFED CREW, ABOUT AN HR INTO FLT, NOTICED FO AIRSPEED STUCK AT 259, ENCOUNTERED A BIT TURBULENCE, PLAYED AROUND WITH THROTTLES, CA INDICATIONS WERE SPOT ON WITH STDBY, ON DESCENT FO AIRSPEED DROPPED TO 45 & REMAINED FOR REST OF FLT, ACP FIM34-21-801, ADIRS BITE TEST, CDU SHOW 1 FLT FAULT LEG 1, FAULT MSG34-21038, AIR/GND LOGIC INVALID. ACP ADIRS OPS TEST IAW MM34-21-00-710-801 STEP F.5, FOR INDEPENDANT LT & RT ADR, LT CHKS NORMAL, RT HAS FAULT AT TAT TEMP OF TAT INDICATION DURING TEST, REF SSM34-21-22-101 FOR TAT PROBE M171 INPUT TO RT ADIRU M1752 AT CONNECTION D3693A PINS H8, J8 TO CONNECTOR D277 PINS 2,5 ON TAT PROBE. ACP FIM 34-21 TASK 824. NO FAULTS FOUND. ALL WIRING CHECKS GOOD. PSEU CONNECTORS D11138 & D11140 WERE R & REINSTALLED FOR WIRING CHECKS. ACP PSEU OP CHECK IAW AMM 32-09-10-710-801. OP CHKS GOOD. ON DESCENT ALTITUDE AROUND A 1000 FT HIGHER THAN CA/STANDBY, EVENED OUT ON LANDING, ON DESCENT GOT MASTER CAUTION & BOTH ENGS WENT INTO ALT MODE & LOST AUTOTHROTTLE, SPEED TRIM FAIL, BOTH IAS & ALT DISAGREE LIGHTS ON IND ON UPPER CENTER DISPLAY. IAW BITE INST SHOWN ON CDU TAT SHOULD READ 35 DEGREE C, LT ADR DOES, RT ADR DOES NOT. SWAPPED ADIRU IAW MM34-21-01, TAT TEMP FAULT DOES NOT FOLLOW ADIRU. RETURNED ADIRU TO ORIGINAL POSITIONS.