Cheetah; Tiger; Traveler AA5 Series
Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Commercial; Flight Crew Flight Instructor
Flight Crew Last 90 Days 250; Flight Crew Total 1000; Flight Crew Type 300
Aircraft Equipment Problem Less Severe; Inflight Event / Encounter Fuel Issue
Flight Crew Diverted
Aircraft
I; pilot flying pilot 1; along with a non-required flight crew member pilot 2 who was assigned to assist navigating and working radio communications; departed to ZZZ for a practice instrument approach and then to proceed to [another airport] for a fuel-stop. We (pilot 1 and pilot 2) departed with approximately 32 gallons of fuel on board. En route; we averaged 8 gallons an hour of fuel burn; comprising of 30 minutes of burn on the left tank; and an hour and fifteen minutes on the right tank; including an increased burn due to takeoff. Upon arrival at ZZZ for our practice approach; we calculated 7.0 gallons in the left tank and 10.0 gallons in the right tank; enough for an hour and a half of flight.After our practice approach into ZZZ; we proceed to climb out in a left turn. We were expecting and experienced a 25 knot tailwind to assist us on our way to [get fuel]; resulting in an estimated arrival in 25 minutes. We calculated to land with six gallons of fuel; approximately 45 minutes of fuel at cruise.On the climbout; I began to notice abnormal Engine Exhaust Gas Temperatures on the Number 4 cylinder. Normal readings range from 1;300-1;450 degrees; whereas I was reading 1550 degrees and climbing. I also noticed an abnormally high reading from the fuel flow indicator whereas in a climb the normal readings ranged from 14.0 GPH to 17.0 GPH. I was reading 22.0 GPH. At the same time; I experienced an error message with one of our GPS units. As I was working through the situation; I asked pilot 2; 'Are you seeing these numbers?' at which he replied 'Yeah; do you feel that?' At that time; I felt the engine running rough and immediately increased full mixture (it was leaned for 1;400 degrees EGT after 3;000 feet); ensured that the fuel pump was on; and switched fuel tanks. I leveled the aircraft into a straight and level cruise and immediately searched for a nearby airport.There were no airports in front of the aircraft; which would have been the favorable glide direction; and ZZZ was the closest airport to our location. I informed pilot 2 that I was [requesting priority handling] with Center and returning to ZZZ; which we completed a safe and successful landing. Approximately two minutes after leveling the aircraft; the conditions ceased. We were met and escorted by the local Airport Rescue and Fire Fighting (ARFF) unit to the FBO.Upon landing; we performed a visual inspection of the engine and engine compartment. Other than a slightly low oil level (to which we added a quart of oil); we did not notice any issues with the engine exterior. We called for fuel from the local FBO and asked for a top off. We received 19 gallons in the right tank; and 17 gallons in the left tank; leading us to calculate having 7 gallons remaining in the right tank; and 9 gallons in the left tank upon landing (a normal two hours at cruise). After receiving fuel; we performed a through engine run-up and determined that there was no further issue concerning safety of flight and we departed.Prior to departure; we determined that the engine roughness; high EGT indications; and high fuel flow indications were caused by a partial fuel starvation of the engine induced by a steep climb attitude causing the fuel to fall to the back of the fuel tank. In the Grumman Tiger; fuel pumps are located at the forward position of the fuel tank. Therefore; in a steep climb; fuel will have difficulty being pumped to the engine if there is less than approximately 7 gallons.In my personal opinion; I believe that the situation was handled with care and safety in mind. The limitation of low-fuel levels in a climb was unknown to myself; and to my current knowledge; is not published in the aircraft POH or other information manuals. Pilot 1 and pilot 2 both performed pre-assigned duties during the emergency and handled the aircraft in a safe manner.
Grumman American Tiger (AA5B) pilot reported having to divert in a climb out due to a rough running engine. Pilot reported the opinion that a steep climb angle caused the fuel to fall to the back of the tank away from the forward mounted fuel pumps.