# JASC 6240: Main Rotor Indicating System

- Type: JASC system/component code (FAA)
- ATA chapter: 62 Main Rotor
- Title in the code table: MAIN ROTOR INDICATING SYSTEM
- Service difficulty reports: 676
- FAA code table: https://www.faa.gov/sites/faa.gov/files/JASC_Code.pdf#page=57
- Page: https://openairdocs.org/jasc/6240

## What it covers

The system used to indicate the operation or activation of the main rotor. Includes lights, gauges, switches, wiring, etc.

## Service difficulty reports (676, newest 50)

- [SDR QR9R2026091600001](https://openairdocs.org/sdr/QR9R2026091600001), Sep 16, 2026: Bolkms BK117C2. SENSOR. INTERMITTENT. LOW ROTOR RPM LT AND AUDIO INTERMITTENTLY ACTIVE WHILE HOVER TAXIING, ALL OTHER INDICATIONS WERE NORMAL. A TESTFLIGHT EV
- [SDR QR9R2026081800001](https://openairdocs.org/sdr/QR9R2026081800001), Aug 18, 2026: Bolkms BK117C2. SENSOR. ERRATIC. ROTOR RPM INDICATOR GAVE ERRATIC INDICATIONS FROM 101% TO 80% DURING FLIGHT. THE ROTOR LOW WARNING LIGHT INDICATION FLUC
- [SDR QR9R2026042000001](https://openairdocs.org/sdr/QR9R2026042000001), Apr 20, 2026: Bolkms BK117C2. SENSOR. FAULTY. AFTER STARTING ENGINE #2, INITIALLY NR APPEARED ON THE TRIPLE TACH AND MATCHED #2 N2, BUT THEN RETURNED TO 0. A BATTERY 
- [SDR QR9R2025110300002](https://openairdocs.org/sdr/QR9R2025110300002), Nov 3, 2025: Bolkms BK117C2. SENSOR. FAULTY. RRPM GAUGE WOULD DROP TO ZERO INTERMITTENTLY IN FLIGHT WITH LOW RRPM AUDIO. ALL OTHER ENGINE INDICATORS WERE NORMAL. HAP
- [SDR QR9R2025103000001](https://openairdocs.org/sdr/QR9R2025103000001), Oct 30, 2025: Bolkms BK117C2. SENSOR. FAULTY. TRIPLE TACH FAILED DURING START UP. NR FAILED TO SYNC, THEN WOULD DROP TO 0. AFTER SEVERAL SECONDS IT WOULD MATCH TO N2 
- [SDR QR9R2025091700001](https://openairdocs.org/sdr/QR9R2025091700001), Sep 17, 2025: Bolkms BK117C2. SENSOR. FAULTY. ROTOR TACH INTERMITTENT. TEST FLIGHT EVAL FOUND ROTOR TACH AND DIGITAL READOUT INTERMITTENT ON THE GROUND BUT WORKS FINE
- [SDR QR9R2025052900003](https://openairdocs.org/sdr/QR9R2025052900003), May 29, 2025: Bolkms BK117C2. SENSOR. FAULTY. APPROXIMATELY ONE MINUTE AFTER FIRST ENGINE START, BOTH NR DISPLAYS (TRIPLE TACH AND VEMD SYSTEM PAGE) DROPPED TO INDICA
- [SDR QR9R2025051600001](https://openairdocs.org/sdr/QR9R2025051600001), May 16, 2025: Bolkms BK117C2. SENSOR. FAULTY. FAULTY TRIPLE TACHOMETER NR INDICATION WITH TWIST GRIPS IN FLIGHT (INTERMITTENT 101 TO 0 INDICATIONS WITH W/U DISPLAY AN
- [SDR QR9R2025040900001](https://openairdocs.org/sdr/QR9R2025040900001), Apr 9, 2025: Bolkms BK117C2. SENSOR. FAULTY. LOW ROTOR RPM LIGHT ON THE WU WITH ASSOCIATED TONE CAME ON INADVERTANTLY 6 TIMES DURING A 30 MINUTE FLIGHT. DURING TROUB
- [SDR QR9R2024101600001](https://openairdocs.org/sdr/QR9R2024101600001), Oct 16, 2024: Bolkms BK117C2. SENSOR. INTERMITTENT. DURING FLIGHT, ROTOR RPM INDICATION DROPPED TO 0 THEN RETURNED TO NORMAL FOUR TIMES TOTAL. TROUBLESHOOTING FOUND THE MAI
- [SDR QR9R2024100800002](https://openairdocs.org/sdr/QR9R2024100800002), Oct 8, 2024: Bolkms BK117C2. SENSOR. FAILED. NR FAILURE ON TRIPLE TACH DURING FLIGHT RESULTING IN AN UNSCHEDULED LANDING. REMOVED AND REPLACED SPEED PICK-UP SENSOR I
- [SDR QR9R2024080700001](https://openairdocs.org/sdr/QR9R2024080700001), Aug 7, 2024: Bolkms BK117C2. PICKUP. FAILED. DURING FLIGHT, TRIPLE TACH FAILED WHEN REDUCING TWIST GRIP FROM FLIGHT TO IDLE. A TEST FLIGHT EVAL REVEALED ROTOR INDICA
- [SDR QR9R2024032500001](https://openairdocs.org/sdr/QR9R2024032500001), Mar 25, 2024: Bolkms BK117C2. PICKUP. FAILED. ON START UP, NR WAS AT IDLE THEN BEGAN FLUCTUATING TO ALMOST ZERO WITH BOTH ENGINES AT IDLE. REMOVED AND REPLACED SPEED 
- [SDR QR9R2024013100001](https://openairdocs.org/sdr/QR9R2024013100001), Jan 31, 2024: Bolkms BK117C2. INDICATOR. FLUCTUATES. DURING HOVER, ROTOR TACH WOULD DROP TO 0 SEVERAL TIMES, THEN GO BACK TO NORMAL. REMOVED AND REPLACED TRIPLE INDICATOR IA
- [SDR YV3R2023120100590](https://openairdocs.org/sdr/YV3R2023120100590), Nov 11, 2023: Robsin R44. DUAL TACHOMETER. DEFECTIVE. CUSTOMER REPORTED DUAL TACHOMETER ASSEMBLY P/N: C792-5 ENGINE NEEDLE WAS OVERREADING 2%.
- [SDR YV3R2023120100589](https://openairdocs.org/sdr/YV3R2023120100589), Nov 11, 2023: Robsin R22BETAII. WARNING SYSTEM. DEFECTIVE. CUSTOMER REPORTED WARNING UNIT ASSEMBLY, LOW RPM P/N: A569-5 WAS INOPERATIVE.
- [SDR 2023FA0000766](https://openairdocs.org/sdr/2023FA0000766), Nov 7, 2023: Bolkms BK117C2. GAUGE. DEBONDED. MAST MOMENT WAS EXCEEDED IN A HOVER. LANDED THE AIRCRAFT WITH NO ISSUES. AFTER TROUBLESHOOTING FOUND THE STRAIN GAUGE IN (N240SF)
- [SDR QR9R2023103100001](https://openairdocs.org/sdr/QR9R2023103100001), Oct 31, 2023: Bolkms BK117C2. PICKUP. FAILED. TRIPLE TACH/ROTOR RPM FAILURE DURING FLIGHT. DURING ROTOR SPEED FAILURE TROUBLESHOOTING, FOUND NR SENSOR BAD DURING FUNC
- [SDR YV3R2023111500586](https://openairdocs.org/sdr/YV3R2023111500586), Oct 19, 2023: Robsin R44RAVENII. WARNING UNIT. DEFECTIVE. CUSTOMER REPORTED WARNING UNIT, LOW RPM P/N: A569-9 PART FAILURE, HORN LIGHT STAYS ON.
- [SDR QR9R2023071900001](https://openairdocs.org/sdr/QR9R2023071900001), Jul 19, 2023: Bolkms BK117C2. PICKUP. ILLUMINATED. IN FLIGHT, VARNAR CAUTION APPEARED THREE TIMES. THE RPM R LIGHT AND AUDIO APPEARED WITH RPM R INDICATING 0% MULTIPLE TIM
- [SDR JBZA20230706001](https://openairdocs.org/sdr/JBZA20230706001), Jul 2, 2023: Airbus EC135P3. UNKNOWN. UNKNOWN. TRIPLE TACHOMETER INDICATIONS LOST FOR # 1 , #2 ENGINES AND MAIN ROTOR TRANSMISSION (N319RX)
- [SDR YV3R2023051600567](https://openairdocs.org/sdr/YV3R2023051600567), May 10, 2023: Robsin R44RAVENII. RELAY. INOPERATIVE. CUSTOMER REPORTED RELAY ASSEMBLY P/N: B280-12 WAS INOPERATIVE (NO LOW RPM LIGHT OR HORN). (N944VB)
- [SDR YV3R2023042700559](https://openairdocs.org/sdr/YV3R2023042700559), Apr 12, 2023: Robsin R22BETAII. WARNING UNIT. DEFECTIVE. CUSTOMER REPORTED WARNING UNIT ASSEMBLY, LOW RPM P/N: A569-5 LOW ROTOR HORN SOUND INOPERATIVE. (N522SB)
- [SDR YV3R2023042700558](https://openairdocs.org/sdr/YV3R2023042700558), Apr 11, 2023: Robsin R44. DUAL TACHOMETER. DEFECTIVE. CUSTOMER REPORTED DUAL TACHOMETER P/N: C792-5 NEEDLES GET STUCK BETWEEN 68% - 90%. (N7102Z)
- [SDR YV3R2023042700555](https://openairdocs.org/sdr/YV3R2023042700555), Mar 30, 2023: Robsin R22BETAII. WARNING UNIT. DEFECTIVE. CUSTOMER REPORTED WARNING UNIT P/N: A569-5 WAS INOPERATIVE. (N313DD)
- [SDR ULXR307FD21323](https://openairdocs.org/sdr/ULXR307FD21323), Feb 13, 2023: Bell 505. SENSOR. FAILED. NR SENSOR FAILURE. NR WENT TO ZERO IN FLIGHT. CAUSED TRANSPONDER TO GO OFF LINE AS AIRCRAFT THOUGHT IT WAS ON THE GROUND (N307FD)
- [SDR YV3R2022111700547](https://openairdocs.org/sdr/YV3R2022111700547), Oct 31, 2022: Robsin R44RAVENII. DUAL TACHOMETER. DEFECTIVE. CUSTOMER REPORTED DUAL TACHOMETER ASSEMBLY P/N: C792-5 FLUCTUATES CAUSING OVER RPM.
- [SDR QR9R2022101900002](https://openairdocs.org/sdr/QR9R2022101900002), Oct 19, 2022: Bolkms BK117C2. INDICATOR. INTERMITTENT. DURING FLIGHT, TRIPLE TACH INTERMITTENT FAILURE. REPLACED TRIPLE TACH IAW 62-41-00,4-3. COMPLETED GROUND RUN AND FLIGHT 
- [SDR YV3R2022111700546](https://openairdocs.org/sdr/YV3R2022111700546), Oct 18, 2022: Robsin R22. WARNING UNIT. INOPERATIVE. CUSTOMER REPORTED WARNING UNIT ASSEMBLY P/N: A569-5 WAS INOPERATIVE OUT OF THE BOX.
- [SDR YV3R2022101500545](https://openairdocs.org/sdr/YV3R2022101500545), Oct 5, 2022: Robsin R22BETAII. NONE. FAULTY. CUSTOMER REPORTED WARNING UNIT ASSEMBLY (LOW RPM) P/N: A569-5 WAS NOT SERVICEABLE.
- [SDR YV3R2022100700544](https://openairdocs.org/sdr/YV3R2022100700544), Sep 15, 2022: Robsin R44RAVENII. NONE. FAILED. CUSTOMER REPORTED WARNING UNIT ASSEMBLY (LOW RPM) P/N: A569-9 FAILED TO ACTIVATE LIGHT AND HORN.
- [SDR YV3R2022100700543](https://openairdocs.org/sdr/YV3R2022100700543), Sep 8, 2022: Robsin R66. NONE. DEFECTIVE. CUSTOMER REPORTED WARNING UNIT ASSEMBLY (LOW RPM) P/N: A569-11 LOW ROTOR WARNING LIGHT AND SOUND (AUDIO) CAME ON DURING 
- [SDR YV3R2022052600529](https://openairdocs.org/sdr/YV3R2022052600529), May 3, 2022: Robsin R66. NONE. DEFECTIVE. CUSTOMER REPORTED WARNING UNIT ASSEMBLY P/N: A569-11 WAS INOPERATIVE. (N10MW)
- [SDR YV3R2022050400527](https://openairdocs.org/sdr/YV3R2022050400527), Apr 22, 2022: Robsin R22. NONE. DEFECTIVE. CUSTOMER REPORTED WARNING UNIT ASSEMBLY (RPM) P/N: A569-5 WAS INOPERATIVE. (N6240)
- [SDR YV3R2022050400525](https://openairdocs.org/sdr/YV3R2022050400525), Apr 9, 2022: Robsin R44RAVENII. NONE. DEFECTIVE. CUSTOMER REPORTED DUAL TACHOMETER ASSEMBLY P/N: C792-4 NEEDLES WERE JUMPING WITHIN UNIT. (N2444)
- [SDR QR9R20220330001](https://openairdocs.org/sdr/QR9R20220330001), Mar 30, 2022: Bolkms BK117C2. PICKUP. FAULTY. FIVE SECONDS AFTER STARTING #1 ENGINE, NR DROPPED TO ZERO THEN RETURNED 3 MINUTES LATER. AFTER RESET, NR LAGGED GOING IN
- [SDR YV3R2022050400524](https://openairdocs.org/sdr/YV3R2022050400524), Feb 14, 2022: Robsin R44RAVENII. NONE. DEFECTIVE. CUSTOMER REPORTED WARNING UNIT ASSEMBLY P/N: A569-9 FAILED TO REACT TO RPM'S.
- [SDR YV3R2022021600517](https://openairdocs.org/sdr/YV3R2022021600517), Jan 27, 2022: Robsin R22BETAII. DUAL TACHOMETER. DEFECTIVE. CUSTOMER REPORTED DUAL TACHOMETER ASSEMBLY P/N: A792-4 INDICATED INCORRECT READING.
- [SDR YV3R2022021000515](https://openairdocs.org/sdr/YV3R2022021000515), Jan 5, 2022: Robsin R22BETAII. NONE. NONE. CUSTOMER REPORTED WARNING UNIT (LOW RPM) P/N" A569-5 WAS NOT FUNCTION AT FULL RPM.
- [SDR YV3R2022021000514](https://openairdocs.org/sdr/YV3R2022021000514), Dec 20, 2021: Robsin R66. NONE. NONE. CUSTOMER REPORTED WARNING UNIT ASSEMBLY (LOW RPM) P/N: A569-11 LOW RPM LIGHT NEVER WENT OUT. CORRECTION: UNIQUE CONTROL 
- [SDR YV3R2022021000513](https://openairdocs.org/sdr/YV3R2022021000513), Dec 20, 2021: Robsin R66. NONE. DEFECTIVE. CUSTOMER REPORTED WARNING UNIT ASSEMBLY (LOW RPM) P/N: A569-11 LOW RPM LIGHT NEVER WENT OUT.
- [SDR QR9R20211207003](https://openairdocs.org/sdr/QR9R20211207003), Dec 7, 2021: Bolkms BK117C2. PICKUP. FAULTY. ONCE THE #1 ENGINE WAS STARTED, NO NRO INDICATIONS. CALLED MAINTENANCE TO TROUBLESHOOT, RESET BAT AND GENERATORS FOR TRO
- [SDR YV3R2021100700497](https://openairdocs.org/sdr/YV3R2021100700497), Sep 22, 2021: Robsin R44. DUAL TACHOMETER. DEFECTIVE. CUSTOMER REPORTED DUAL TACHOMETER P/N: C792-4 WAS INTERMITTENT. (N808LB)
- [SDR YV3R2021090100492](https://openairdocs.org/sdr/YV3R2021090100492), Aug 24, 2021: Robsin R22. DUAL TACHOMETER. DEFECTIVE. CUSTOMER REPORTED DUAL TACHOMETER ASSEMBLY P/N: A792-4 ENGINE TACH NEEDLE READS 70% WITH ENGINE SHUT DOWN.
- [SDR YV3R2021072200471](https://openairdocs.org/sdr/YV3R2021072200471), Jul 12, 2021: Robsin R44RAVENII. WARNING UNIT. DEFECTIVE. CUSTOMER REPORTED WARNING UNIT P/N: A569-9 HORN (AUDIO) DID NOT SOUND. (N882GD)
- [SDR YV3R2021070700469](https://openairdocs.org/sdr/YV3R2021070700469), Jun 30, 2021: Robsin R44RAVENII. DUAL TACHOMETER. DEFECTIVE. CUSTOMER REPORTED DUAL TACHOMETER P/N: C792-4 ROTOR NEEDLE READS LOW 2-5%. (N144KD)
- [SDR YV3R2021070700468](https://openairdocs.org/sdr/YV3R2021070700468), Jun 29, 2021: Robsin R44. DUAL TACHOMETER. DEFECTIVE. CUSTOMER REPORTED DUAL TACHOMETER P/N: C792-4 ROTOR NEEDLE WAS INTERMITTENT, AND THEN FAIL COMPLETELY. (N46SG)
- [SDR YV3R2021060900461](https://openairdocs.org/sdr/YV3R2021060900461), Jun 1, 2021: Robsin R44. DUAL TACHOMETER. DEFECTIVE. CUSTOMER REPORTED DUAL TACHOMETER P/N: C792-4 ENGINE NEEDLE PEGS WITH POWER APPLIED. (N715SG)
- [SDR YV3R2021052800458](https://openairdocs.org/sdr/YV3R2021052800458), May 19, 2021: Robsin R66. WARNING UNIT. DEFECTIVE. CUSTOMER REPORTED WARNING UNIT (LOW RPM) P/N: A569-11 WAS NOT FUNCTIONING CORRECTLY, LOW RPM LIGHT ILLUMINATES WITH HORN (N73PT)
- [SDR YV3R2021052800457](https://openairdocs.org/sdr/YV3R2021052800457), May 17, 2021: Robsin R22BETAII. WARNING UNIT. DEFECTIVE. CUSTOMER REPORTED WARNING UNIT ASSEMBLY (LOW RPM) P/N: A569-5 WAS INOPERATIVE. (N142VA)

All 676: https://openairdocs.org/jasc/6240/reports.md

## Other codes in chapter 62

- [JASC 6200](https://openairdocs.org/jasc/6200): Main Rotor System (168 reports)
- [JASC 6210](https://openairdocs.org/jasc/6210): Main Rotor Blades (1,561 reports)
- [JASC 6220](https://openairdocs.org/jasc/6220): Main Rotor Head (2,052 reports)
- [JASC 6230](https://openairdocs.org/jasc/6230): Main Rotor Mast/Swashplate (1,271 reports)
- [JASC 6297](https://openairdocs.org/jasc/6297): Main Rotor System Wiring (8 reports)

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