Date: 201208
Local time of day: 0601-1200
Location: ZZZ.Airport, US
Flight conditions: VMC
Weather elements / visibility: 50
Light: Daylight
Aircraft: RV-8
Operator: Personal
Operating under: Part 91
Flight plan: None
Mission: Personal
Flight phase: Cruise
Airspace: Class E ZZZ1
ATC / advisory: UNICOM ZZZ1
Second aircraft: Amateur/Home Built/Experimental
Aircraft component: Engine
Component problem: Malfunctioning
Reporter organization: Personal
Reporter function: Single Pilot; Pilot Flying
Reporter qualification: Flight Crew Multiengine; Flight Crew Flight Engineer; Flight Crew Air Transport Pilot (ATP)
Human factors: Situational Awareness; Troubleshooting; Human-Machine Interface; Distraction; Communication Breakdown
Second reporter function: Pilot Flying
Anomaly: Aircraft Equipment Problem Critical; Airspace Violation All Types
Detector: Person Air Traffic Control; Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Issued Advisory / Alert; Air Traffic Control Provided Assistance; Flight Crew Landed in Emergency Condition; General Declared Emergency
Contributing factors: Aircraft; Airspace Structure; Human Factors
Primary problem: Aircraft

Narrative: I was approximately a mile in trail of my friend's CJ-6 at 2500 FT MSL in VMC. We were both left of track as a direct routing would have placed us slightly into a TFR.Approximately 10NM WSW of a major airport my engine began an intermittent; abnormal vibration. I immediately selected full rich on the mixture control and turned on high pressure from the electric fuel pump but the vibration continued to intensify. While I searched for suitable emergency landing areas; I maneuvered to the north of the track toward a four lane divided highway which offered a potential emergency landing surface. I radioed my friend ahead to slip back and look over my airplane for any sign of aircraft damage or fire.I retarded the throttle to reduce vibration and at 1200-1275 RPM the vibration decreased; however airspeed slowed to 85-90 MPH. I was able to maintain between 2000-2500 FT MSL. My GPS indicated a major airport ahead; ZZZ; as closest to my position. I continued towards that airport with my speed stabilized and holding altitude. I then asked my friend in the CJ-6 to contact the Tower and declare my emergency and intention to try for ZZZ. The Tower Controller sent me immediately to Approach Control; where I redeclared my emergency and intentions. I also advised Approach that I had another aircraft following me for possible assistance; however he had remained on Tower frequency apparently not hearing the frequency change to Approach.  Initially I picked up a  westerly heading to fly along another 4-lane highway running West toward the airport. Approach advised me that this road would place me on a right base to the airport and runways. Approach handed me off to Tower and I landed safely with the CJ-6 following on a low approach. I terminated the emergency upon clearing the active runway.  Upon taxi in; Tower instructed me and the other pilot to contact Approach Control upon shutdown. I was advised by Approach Control of a possible deviation into the TFR.


Second narrative: After approximately a minute he then informed me he heard a loud pop followed by increased vibration. At this point I was unaware that the aircraft had begun slowing down therefore taking a long time for me to maneuver into position to scan. With RV-8 off to my left I continued to slow while trying to visually pick out possible landing sites. Once in position there were no visible signs of smoke or fluids coming from the aircraft. I requested to follow the RV-8 in for a low approach to a closed pattern back for landing. It was granted and I landed; taxied clear; and parked.


Synopsis: Two homebuilts in loose formation inadvertently entered a TFR when they were distracted by abnormal vibrations in the engine of one of the aircraft.  They declared an emergency and the ailing aircraft landed at the nearest suitable airport.