Fastwind67
Member
Last week in my RV-4 I was at 11,000 MSL, IMC and in moderate rain and light turbulence, and had been for 10 - 15 minutes. The OAT was about 44 degrees F.
Instantly my engine went from normal to EXTREMELY rough and it felt as though I lost about 50% power, though the RPM stayed the same - C/S prop.
I did not notice a manifold pressure change, but I'm guessing one occurred. No change in CHT or EGT or anything else I observed. Boost pump on, switch fuel tanks, mixture rich - no change. Carb heat on - at this point I got a slight change in engine sound and feel, but I can't really say it was any better. Checked Left Mag, then Right, then Both again, these of course caused a slight change in the engine, but no improvement.
Request vectors from ATC to VMC (my gyros are still vacuum, as in engine driven) and toward nearest airport over 3,000'
Still able to maintain altitude at this point.
Carb heat off, then on, still not much change and no improvement. Carb heat on and continue toward VMC. Gradually the engine smoothed out and also the rain ended.
The next 10 hours of flight were without anomaly, though I did re-enter a short period of rain. I have also flown in rain before, but never as heavy as on this occasion.
My best guess is I was ingesting water.
Setup: O-320 with Ellison EFS-4 Throttle Body Injection. The EFS-4 is mounted pointing forward and utilizes a 90 degree plenum box on the bottom of the engine. The EFS-4 has a typical carb heat selector box in front of it then about 3" of scat tube running directly forward to the cowl opening where the only filtration is a basic screen door type screen. No air filter.
Yes, it would seem that rain would proceed directly into the EFS-4 and then through the engine if the carb heat were not selected. I've flown in rain several times before however, and apparently the rain/water going through the engine causes no detectable effects. My thought is the rain collected in the carb heat box until it got "deep" enough to spill a considerable amount into the EFS-4 all at once. I've since drilled small drain holes in the low spot of the carb heat selector box to allow any pooling water to run out.
I don't think I had "carb ice" because the onset was not a gradual loss of MP but rather instantaneous extreme roughness. Also the EFS-4 is not prone to carb ice by its sort of lack of a venturi. I understand the 90 degree change plenum box does operate below freezing most all of the time and perhaps liquid rain froze in that box, but again, I'm not sure how this would have caused a sudden onset of roughness.
Any thoughts out there? Anyone experienced roughness before from rain ingestion?
Instantly my engine went from normal to EXTREMELY rough and it felt as though I lost about 50% power, though the RPM stayed the same - C/S prop.
I did not notice a manifold pressure change, but I'm guessing one occurred. No change in CHT or EGT or anything else I observed. Boost pump on, switch fuel tanks, mixture rich - no change. Carb heat on - at this point I got a slight change in engine sound and feel, but I can't really say it was any better. Checked Left Mag, then Right, then Both again, these of course caused a slight change in the engine, but no improvement.
Request vectors from ATC to VMC (my gyros are still vacuum, as in engine driven) and toward nearest airport over 3,000'
Still able to maintain altitude at this point.
Carb heat off, then on, still not much change and no improvement. Carb heat on and continue toward VMC. Gradually the engine smoothed out and also the rain ended.
The next 10 hours of flight were without anomaly, though I did re-enter a short period of rain. I have also flown in rain before, but never as heavy as on this occasion.
My best guess is I was ingesting water.
Setup: O-320 with Ellison EFS-4 Throttle Body Injection. The EFS-4 is mounted pointing forward and utilizes a 90 degree plenum box on the bottom of the engine. The EFS-4 has a typical carb heat selector box in front of it then about 3" of scat tube running directly forward to the cowl opening where the only filtration is a basic screen door type screen. No air filter.
Yes, it would seem that rain would proceed directly into the EFS-4 and then through the engine if the carb heat were not selected. I've flown in rain several times before however, and apparently the rain/water going through the engine causes no detectable effects. My thought is the rain collected in the carb heat box until it got "deep" enough to spill a considerable amount into the EFS-4 all at once. I've since drilled small drain holes in the low spot of the carb heat selector box to allow any pooling water to run out.
I don't think I had "carb ice" because the onset was not a gradual loss of MP but rather instantaneous extreme roughness. Also the EFS-4 is not prone to carb ice by its sort of lack of a venturi. I understand the 90 degree change plenum box does operate below freezing most all of the time and perhaps liquid rain froze in that box, but again, I'm not sure how this would have caused a sudden onset of roughness.
Any thoughts out there? Anyone experienced roughness before from rain ingestion?