Hi Folks,
I am scratching my head about an oscillating RPM drop and EGT rises on a recent flight. The aircraft experienced a series of oscillating drop on RPM (and power) on a climb out.
This is on an RV-10 with a fuel-injected IO-540, with dual PMAGs. This flight was on a hot day ~95-100 Def F OAT at KSZT. The airplane was performing flawlessly to KSZT prior to this flight - KSZT was a fuel stop and this episode happened on the outbound flight.
Here is the snapshot from Savvy:
image:
A few observations:
1) The fuel pressure is above 20 throughout the episode. (The fuel boost pump was on during initial climb out, turned on again after a few secs as it dropped to 15 momentarily 12:45 to 13:00 mark)
2) EGTs on All the cylinders rise and fall together.
3) The RPM oscillations and the EGT oscillations seem to be correlated.
4) I have not yet seen a similar behavior after this episode. [The aircraft returned to KSZT, spent a night and departed the following morning after a thorough inspection / run-up etc.]
Due to #1 I am inclined to believe that Fuel pressure was not a problem. Is vapor lock / bubbling fuel still a possibility and cause?
Due to #2 It appears whatever the reason is it affected the entire ignition system (both Mags) and that too in-synchrony. I am unable to figure out what - given that both the mags are independent power sources.
Any suggestions / thoughts on where I should be looking?
Thanks,
Ashish
I am scratching my head about an oscillating RPM drop and EGT rises on a recent flight. The aircraft experienced a series of oscillating drop on RPM (and power) on a climb out.
This is on an RV-10 with a fuel-injected IO-540, with dual PMAGs. This flight was on a hot day ~95-100 Def F OAT at KSZT. The airplane was performing flawlessly to KSZT prior to this flight - KSZT was a fuel stop and this episode happened on the outbound flight.
Here is the snapshot from Savvy:
image:
A few observations:
1) The fuel pressure is above 20 throughout the episode. (The fuel boost pump was on during initial climb out, turned on again after a few secs as it dropped to 15 momentarily 12:45 to 13:00 mark)
2) EGTs on All the cylinders rise and fall together.
3) The RPM oscillations and the EGT oscillations seem to be correlated.
4) I have not yet seen a similar behavior after this episode. [The aircraft returned to KSZT, spent a night and departed the following morning after a thorough inspection / run-up etc.]
Due to #1 I am inclined to believe that Fuel pressure was not a problem. Is vapor lock / bubbling fuel still a possibility and cause?
Due to #2 It appears whatever the reason is it affected the entire ignition system (both Mags) and that too in-synchrony. I am unable to figure out what - given that both the mags are independent power sources.
Any suggestions / thoughts on where I should be looking?
Thanks,
Ashish
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