SR22
Flight Crew Commercial; Flight Crew Instrument
Flight Crew Last 90 Days 75; Flight Crew Total 550; Flight Crew Type 450
Situational Awareness; Troubleshooting
Aircraft Equipment Problem Critical
Flight Crew Overcame Equipment Problem; General Flight Cancelled / Delayed
Human Factors; Aircraft
On the second flight of the day I was departing on a hot and muggy late afternoon.  I called Tower for a full length departure as per my own personal Standard Operation Procedure (SOP) to maximize climb with available runway surface.  This enables me to maintain off engine over runway as long as possible prior to reaching parachute activation altitude. As I began my takeoff roll I noted; airspeed alive; oilT; oilP; CHT; EGT; RPM all in good ranges; then I noticed the Fuel Flow (FF) is 27.3 GPH (gallons per hour) when normally this is steady 29 GPH.  I paused for a moment and then decided to abort the takeoff to check into this anomaly.  I reduced power to idle and slowly increased brake pressure to a stop.  The Tower asked if I needed assistance; I declined and asked to taxi back for another run-up.  During the Static Full Power run-up I discover the FF was back to a normal range of 29 GPH; I performed a Full Static Power Mag Check as well; all indications are normal.  It was then I noticed the Brake Temp alarm caution is on; I ask Ground to taxi back for a shutdown while brakes cool down. I called Cirrus Field Service Manager who is also a current Airframe/Powerplant (A/P) and Inspection Authorized (I/A) Mechanic.  He reported to me it was probably the hot fuel causing some minor vapor locking and soon after takeoff it should return to a normal level.  After letting the brakes cool down I elected to depart per his approval based on:1.) The aircraft had recently undergone inspection about 7-hours ago with excellent compression ratios; excellent boroscope inspection; and excellent oil analysis.2.) I inspected the aircraft engine through cowling and observed no leaks of oil or fuel. 3.) Teledyne-Continental Motors (TCM) specifications (spec) are between 26-30 GPH and we were still in a normal range.  During subsequent takeoff; I noted FF of 28 GPH and shortly after takeoff the FF was capable of reaching 29 GPH again.  While I am not sure exactly why this event occurred; I plan to research more about the cause of this for future knowledge.
Reporter stated he has not acquired any further information as to the cause of the fuel flow differences from what he normally sees in the SR-22 aircraft; other than what the Field Service Representative indicated was most likely the cause of the lower fuel flow readings. The aircraft had already flown a previous mission that morning and the day was hot and humid; all of which probably did contribute to the lower fuel flow reading. Different RPMs would also affect the FF flow.
A single pilot in a Cirrus SR22 aircraft describes his concerns about lower than expected fuel flow readings from a Teledyne-Continental engine on takeoff roll.