Cessna 680A captain reported a nose gear unlock message during climbout followed by a loud recurring...

Attributes
ACN	1601815
Time
Date	201812
Place
Locale Reference	ZZZ.ARTCC
State Reference	US
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	Citation Latitude (C680A)
Operating Under FAR Part	Part 91
Flight Phase	Climb
Flight Plan	IFR
Component
Aircraft Component	Gear Extend/Retract Mechanism
Person 1
Function	Captain Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP) Flight Crew Multiengine Flight Crew Instrument
Events
Anomaly	Aircraft Equipment Problem Less Severe Deviation - Procedural Published Material / Policy Deviation - Speed All Types

Narrative:

Climbing through FL340 and 260 KIAS nose gear unlock with associated cas message displayed. Simultaneously loud and recurring banging from nose gear attempting to lock at a 3 times per second frequency. Associated wind noise and pitch movement from nose doors partially opening along with an overspeed warning related to the 210 KT gear limitation.slowed below 210 and descent initiated; QRH for 'gear disagree north' cas. We extended gear at FL180 without further issue. We diverted to ZZZ airport which was about 80 miles from us due to known good weather (we had been in ZZZ earlier in the day); substantial runways and emergency equipment availability.initially my sic and I wrongly thought there was an 18;000 gear operation limit; which apparently there is not. Hence the reason we waited until FL180 to extend gear. The 18;000 limitation only applies to the flaps unlike our previous aircraft.

Original NASA ASRS Text

Title: Cessna 680A Captain reported a nose gear unlock message during climbout followed by a loud recurring banging noise from the nose gear attempting to lock. The flight crew extended the gear at FL180 and diverted to the nearest suitable airport.

Narrative: Climbing through FL340 and 260 KIAS nose gear unlock with associated CAS message displayed. Simultaneously loud and recurring banging from nose gear attempting to lock at a 3 times per second frequency. Associated wind noise and pitch movement from nose doors partially opening along with an overspeed warning related to the 210 KT gear limitation.Slowed below 210 and descent initiated; QRH for 'GEAR DISAGREE N' CAS. We extended gear at FL180 without further issue. We diverted to ZZZ airport which was about 80 miles from us due to known good weather (we had been in ZZZ earlier in the day); substantial runways and emergency equipment availability.Initially my SIC and I wrongly thought there was an 18;000 gear operation limit; which apparently there is not. Hence the reason we waited until FL180 to extend gear. The 18;000 limitation only applies to the flaps unlike our previous aircraft.

Data retrieved from NASA's ASRS site 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.

Cessna 680A captain reported a nose gear unlock message during climbout followed by a loud recurring banging noise from the nose gear attempting to lock. The flight crew extended the gear at FL180 and diverted to the nearest suitable airport.