B777 flight crew reported their aircraft became non-rvsm on their trans-atlantic flight.

Attributes
ACN	1309025
Time
Date	201511
Local Time Of Day	1201-1800
Place
Locale Reference	ZOB.ARTCC
State Reference	OH
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	B777 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	Cruise
Route In Use	Oceanic
Flight Plan	IFR
Component
Aircraft Component	Flight Dynamics
Person 1
Function	Pilot Flying Captain
Experience	Flight Crew Last 90 Days 139 Flight Crew Total 14313 Flight Crew Type 3896
Person 2
Function	First Officer Pilot Not Flying
Experience	Flight Crew Last 90 Days 225 Flight Crew Total 23500 Flight Crew Type 6750
Events
Anomaly	Aircraft Equipment Problem Less Severe

Narrative:

Reaching cruise at FL370; a system malfunction caused the loss of transponder and TCAS. Unable rvsm; ATC descended us to FL270. After conferring with [maintenance]; it appeared to be a failed aims (air data module) module with no possible attempt at a reset. All navigation and remaining avionics were operating normally. Dispatch worked up [a new release] with a re-dispatch intermediate destination. I agreed and accepted the rls (release) and we proceeded on to fra at FL270; but it was going to be tight at the re-dispatch point and as we continued on we definitely felt the need for a higher altitude to make a successful dispatch all the way to fra. Referencing fom (flight operations manual) we managed to get FL330 from gander oceanic as they guaranteed 2;000 ft vertical separation. We were very proactive entering each ATC area that all were aware and approved 2;000 ft vertical separation. This worked thru london airspace; then it was back down to FL270. Landed uneventfully in fra with 12.5 fuel at touchdown. Just an awkward and unusual situation for me. Great crew; teamwork and resource utilization.

Original NASA ASRS Text

Title: B777 flight crew reported their aircraft became non-RVSM on their trans-Atlantic flight.

Narrative: Reaching cruise at FL370; a system malfunction caused the loss of transponder and TCAS. Unable RVSM; ATC descended us to FL270. After conferring with [Maintenance]; it appeared to be a failed AIMS (Air Data Module) module with no possible attempt at a reset. All navigation and remaining avionics were operating normally. Dispatch worked up [a new release] with a re-dispatch intermediate destination. I agreed and accepted the RLS (release) and we proceeded on to FRA at FL270; but it was going to be tight at the re-dispatch point and as we continued on we definitely felt the need for a higher altitude to make a successful dispatch all the way to FRA. Referencing FOM (Flight Operations Manual) we managed to get FL330 from Gander Oceanic as they guaranteed 2;000 ft vertical separation. We were very proactive entering each ATC area that all were aware and approved 2;000 ft vertical separation. This worked thru London airspace; then it was back down to FL270. Landed uneventfully in FRA with 12.5 fuel at touchdown. Just an awkward and unusual situation for me. Great crew; teamwork and resource utilization.

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.