erich weaver
Well Known Member
Had an event yesterday that shook me up and I would like some assistance in sorting things out. Yesterday was the second flight of my RV-7A. Shortly after takeoff, I had just turned cross wind when I had a momentary loss of power - maybe a couple of seconds - followed by a backfire, then return of power. Got it back on the ground without incident after reducing power and staying in a tight pattern. Confidence was severely shaken however.
Here are the circumstances, as best I know them. Not sure what is relevant to the power loss and what is not. Keep in mind it was only the second flight - its still pretty much a sensory overload experience for me.
Equipment: IO-360B1B, AFP boost pump, GRT EIS and EFIS, dual p-mags
Possibly relevant issues from the first flight:
(1) fuel pressure reading was usually normal, about 25 psi I think, but occasionally went erratic, jumping up into the 40s, 50 and 60s and jumping all over before settling back down to normal again. Ii didnt notice any changes in engine performance when it did go nuts, and I later attributed it to faulty readings, maybe due to vibration
(2)Warning light for high fuel flow went off, although I cant say now exactly what the fuel flow reading was at the time. Light went off after power reduction, but I later reset the alarm to go off at a higher flowrate - I believe it was set to 21 or 22 gph for the second flight.
Second flight details:
During the abbreviated second flight, I remember the fuel flow alarm again going off shortly after lift-off and seeig a reading of 22 gph. This seems too high to me, even at full power. Im not sure now whether or not the alarm was still going off when I had the loss of power a short time later. At some point I hit the Ack button, but dont remember now exactly when I did this.
My limited analysis: Momentary loss of power means a momentary loss of air, fuel or spark occurred. Im ruling out an air problem, at least in the grossest sense - my inlet is clear of obstructions.
The fact that there was a backfire leads me to believe there was a spark/timing problem. I know p-mags have had their issues, but I have a hard time seeing how I could have been so unlucky as to have had a simultaneous dual failure. No product bashing here please. Mag check at runup showed both ignitions to be functioning properly. I checked timing after shutdown and both gave me a geen light at TDC like they should. Brad at Emagair has aready offered to go over them with a microscope to check them out and I will definitely do that.
Not sure about a fuel problem. Tanks were sumped prior to take-off - no water observed. Will check filter in boost pump, but seems unlikely that a clogged filter would result in only a momentary loss of power.
With respect to the occasionally erratic fuel pressure readings, is it even possible that my boost pump/engine driven pump combo could generate pressures in the 40-65 psi range? Is my high fuel flow rate at take-off truly abnormal? If it is abnormal, could that result in momentary loss of power and a backfire?
Any insights would be appreciated. Im hoping to make this project fun. Right now it definitiely is not.
thanks
erich
Here are the circumstances, as best I know them. Not sure what is relevant to the power loss and what is not. Keep in mind it was only the second flight - its still pretty much a sensory overload experience for me.
Equipment: IO-360B1B, AFP boost pump, GRT EIS and EFIS, dual p-mags
Possibly relevant issues from the first flight:
(1) fuel pressure reading was usually normal, about 25 psi I think, but occasionally went erratic, jumping up into the 40s, 50 and 60s and jumping all over before settling back down to normal again. Ii didnt notice any changes in engine performance when it did go nuts, and I later attributed it to faulty readings, maybe due to vibration
(2)Warning light for high fuel flow went off, although I cant say now exactly what the fuel flow reading was at the time. Light went off after power reduction, but I later reset the alarm to go off at a higher flowrate - I believe it was set to 21 or 22 gph for the second flight.
Second flight details:
During the abbreviated second flight, I remember the fuel flow alarm again going off shortly after lift-off and seeig a reading of 22 gph. This seems too high to me, even at full power. Im not sure now whether or not the alarm was still going off when I had the loss of power a short time later. At some point I hit the Ack button, but dont remember now exactly when I did this.
My limited analysis: Momentary loss of power means a momentary loss of air, fuel or spark occurred. Im ruling out an air problem, at least in the grossest sense - my inlet is clear of obstructions.
The fact that there was a backfire leads me to believe there was a spark/timing problem. I know p-mags have had their issues, but I have a hard time seeing how I could have been so unlucky as to have had a simultaneous dual failure. No product bashing here please. Mag check at runup showed both ignitions to be functioning properly. I checked timing after shutdown and both gave me a geen light at TDC like they should. Brad at Emagair has aready offered to go over them with a microscope to check them out and I will definitely do that.
Not sure about a fuel problem. Tanks were sumped prior to take-off - no water observed. Will check filter in boost pump, but seems unlikely that a clogged filter would result in only a momentary loss of power.
With respect to the occasionally erratic fuel pressure readings, is it even possible that my boost pump/engine driven pump combo could generate pressures in the 40-65 psi range? Is my high fuel flow rate at take-off truly abnormal? If it is abnormal, could that result in momentary loss of power and a backfire?
Any insights would be appreciated. Im hoping to make this project fun. Right now it definitiely is not.
thanks
erich