Date: 201909
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Aircraft: Cessna Aircraft Undifferentiated or Other Model
Operator: Personal
Operating under: Part 91
Flight plan: VFR
Flight phase: Cruise
Airspace: Class E ZOA
ATC / advisory: Center ZOA
Aircraft component: Cylinder
Component problem: Malfunctioning
Reporter organization: Government
Reporter function: Enroute
Reporter qualification: Air Traffic Control Fully Certified
Human factors: Confusion; Human-Machine Interface; Situational Awareness; Troubleshooting
Anomaly: ATC Issue All Types; Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Provided Assistance; Flight Crew Landed in Emergency Condition; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Diverted
Contributing factors: Human Factors; ATC Equipment / Nav Facility / Buildings; Aircraft; Chart Or Publication
Primary problem: Aircraft

Narrative: Aircraft X called as a VFR call up. We processed the call using a code and established the destination. Then they advised they were diverting to ZZZ due to the loss of a cylinder. A few minutes later they asked for the closest road. The sector team had to move to the next scope to correlate with the overhead sectional for the closest road but it was a best guess as we were trying to tell where it was in relation to where he was on the scope and was mostly guess work. The aircraft had lost power in one cylinder in a largely uninhabited area and [presumably] with reduced power. I gave the pilot [the] option of ZZZ1 as it was less mountainous but would still require travel over rolling terrain with peaks around 9;000 ft. [and] not many roads but again had to estimate the location of them because they are separate from the scope. Landing on the road was becoming a real possibility for the emergency condition. Eventually the pilot got the [road] in sight and then [went] below the radar coverage of [the] sector. We suggested and they finally took the option of landing at ZZZ2 instead of ZZZ since it would require going past a perfectly good airport and then up into another valley.While they did not end up landing on the road; it was a real possibility. A road map overlay on the scope could have been the difference in an off-airport forced landing in a field versus on an open road. I assume this data exists in the government database somewhere since it is charted in the sectionals. Having at least the major highways and dual lane roads; as categorized on the sectionals; would [be] immensely helpful in situations such as this. Both as off-airport landing locations and for lost aircraft. Additionally the ERIDs (En-Route Information Display system) digital sectionals are not good for quick access. Loading them takes forever as they are very large PDF files and the PCs seem underpowered for them; PDFs sometimes fail to load or crash Adobe reader. They also do not support multi touch which is the standard to navigating digital maps and screens now; instead using awkward single point dragging. Even paper sectionals would be more useful at times but are not maintained at all. Even a mounted iPad with ForeFlight would be more effective than ERIDs at this.




Synopsis: Center Controller reported an issue tracking a distressed aircraft that needed to land as map overlay tools were unreliable.