Date: 201710
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Flight conditions: VMC
Weather elements / visibility: 10
Light: Daylight
Aircraft: RV-12
Operator: Personal
Operating under: Part 91
Flight plan: None
Mission: Personal
Flight phase: Taxi
ATC / advisory: Ground ZZZ
Second aircraft: Light Transport; High Wing; 2 Turboprop Eng
Reporter organization: Personal
Reporter function: Single Pilot; Pilot Flying
Reporter qualification: Flight Crew Private; Flight Crew Instrument
Human factors: Communication Breakdown
Anomaly: ATC Issue All Types; Conflict Ground Conflict; Critical; Ground Event / Encounter Other / Unknown
Detector: Person Flight Crew
When detected: Taxi
Result: Flight Crew Took Evasive Action
Contributing factors: Airport; Procedure
Primary problem: Procedure

Narrative: I was parked in the transient parking area and called to taxi to run up with the current ATIS. I was cleared by ground control to taxi to run up which took me to the end of [the runway]. I completed my run up and called ground and was cleared to taxi to departure RWY and hold short. Which I did. I switched to the Tower and requested departure. The Tower repeated hold short. I repeated back holding short. A Cessna was turning base to final while I held short. In the minute waiting for the Cessna to land; three firefighting airplanes taxied up next to me. The Cessna landed barely able to squeeze between me holding at the RWY 27 hold line and the taxi lights on the far side of the taxiway. I repeated my question to the tower if I should continue to hold or not? The Tower repeated for me to hold. Note: I did not hear any radio communications between the Tower and firefighting planes so I assumed they were talking on another frequency. They just started scrambling past my plane even though they didn't have enough room to get their big airplanes past my RV12 without their wings passing over the top of my wing. By that time; my little RV12 was bucking and bouncing like a bronco in the turbo prop blast and I just held on praying my plane wouldn't flip over. This repeated three times in rapid succession for each of the three firefighting airplanes. I did not call Tower at that moment because I was too busy trying to keep my plane on the ground using the controls. (Note: my RV12 will fly at 42 kts.)As soon as the last of the firefighting planes had barely lifted off the runway a foot or two feet; the Tower immediately called me and said I was cleared for takeoff. I responded to the Tower with a loud terse statement that 'THAT WAS UNSAFE. MY LITTLE PLANE ALMOST FLIPPED OVER.' The Tower paused for an awkward time then repeated I was cleared for T/O. I taxied into position on [the runway] and could see the heavy [aircraft] had left swirling wing tip vortices that were kicking up dust all the way down the runway. The Tower did NOT mention to me any caution about wake turbulence so I called back to the Tower that I couldn't T/O with the vortices. They were still visibly kicking up dust. After 30 sec to a minute wait; the dust settled and I took off shaken but safe.The unsafe operations: The Tower and Ground Control should never have cleared the much larger firefighting airplanes to taxi so close to me that the wing of the [firefighting aircraft] passed over the top of my wing as it taxied past. Also; the prop blast from the much larger turbo prop airplanes only a few feet away could have flipped my aircraft over resulting in severe damage to my airplane and possibly severe bodily injury to my wife and me.The firefighting airplane pilots also ignored the safety of my airplane. They should have refused to taxi past my small plane since it was obvious they had to be way too close to be safe.




Synopsis: RV-12 pilot reported that when he was lined up for takeoff two firefighting airplanes squeezed by his airplane and took off in front of him causing wake turbulence.