- Joined
- Mar 17, 2007
- Messages
- 758
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Alright guys,
I need your collective experience and in a bad way. About 2 years ago while flying from WA to Lompoc, CA at about 500' AGL (it was about 96 F and that's as high as I could get) I had an abrupt drop in RPM and made an emergency landing in a graded field. Long story short...no damage. But the engine was "gone through" by very experienced antique engine guys at Santa Paula, CA and no culprit found. Also, the condition was never able to be duplicated, yet has now happened twice relatively recently but again, not able to be duplicated. Even more frustrating is that I can't seem to find any commonality during any of the episodes.
This will be a long post, but I'm running into a frustrating brick wall of my own so I'm going to list each of the occurrences and see if the symptoms look familiar to any of you.
The engine is a stock, otherwise very smooth running A-65, metal Macauley 7445 prop. About 400 SMOH, Airwolf firewall mounted oil filter, and Brackett Air Filter, but no mods otherwise. I religiously change the oil and clean the plugs every 25 hours. I use MMO as an additive. but probably not all the time...just when I remember it, and I don't run auto gas.
July 07: Flying at the above San Joaquin Valley at about 9 am at 90-95 F and 500' agl and about 80% power, the RPM abruptly dropped from 2,000 to about 1,500 just like someone has yanked the throttle back. But, the engine continued to run smooth at that RPM. Carb heat made no difference. Once safely on the ground, a static run-up was conducted and full power was attained with no probems. The wings were still taken off and it was trucked out for inspection. The mechanics were unable to find a definitive cause, nor were they able to duplicate it.
The plane was subsequently flown for 2 years in varied summer and winterWX conditions and about 100 tach hours with no problems and then it reappeared;
June 09: It was about 2pm and 65 F here in Washington state. I took off with a student and told him to climb to 1,500' msl. Around 1,000 ft, the RPM again came abruptly back as if it were yanked by but otherwise smooth. We turned back for an uneventful landing. Carb heat made no difference, nor did retarding the throttle and reapplying it. Thank goodness, the J-3 climbs so slow that 1,000 only gets me just outside pattern range. As with before, once on the ground, a static run-up was conducted and worked normally with full RPM and good mag check/drop. This time I had a different. local antique engine and knowledgeable J-3 guy go through the engine. he said he found some minor debris in the gascolator, but nothing that would cause an immediate RPM drop. He reassembled it, and flew pattern for 30 minutes with no apparent faults.
July 09: I take off with the same student as above (he's the best 16 year old student pilot in dealing with power loss that you've ever seen
), as we climb through about 500' - 600' agl, I detect a slight roughness and drop in RPM. I immediately turned back to the runway, and with the landing assured I pulled throttle back and advanced it, with no more gain in RPM. Carb heat did nothing. Once on the ground and the throttle to idle, another run-up was done and everything checked normal. Determined to trouble shoot under controlled circumstances, I flew close in touch and goes for an hour trying to duplicate the condition, but to no avail!
On a slightly unrelated note, before anyone starts sharp shooting my technique of turning to the runway, keep in mind that here in Olympia, straight ahead more than likely means you're hitting 150 - 200' trees, and much like anyone at their home airport, I've bounced around my pattern enough time to instinctively know how high I have to be and the given distance from the runway to safely make it back. That obviously wouldn't be the case at an unfamiliar airport.
So, I'm now afraid to take the plane anywhere but the pattern and still unable to either isolate or duplicate the problem. I'll be happy to answer any other questions that might assist any of you experienced A&Ps/IAs in figuring this out.
Much thanks for your expertise,
Mike-
I need your collective experience and in a bad way. About 2 years ago while flying from WA to Lompoc, CA at about 500' AGL (it was about 96 F and that's as high as I could get) I had an abrupt drop in RPM and made an emergency landing in a graded field. Long story short...no damage. But the engine was "gone through" by very experienced antique engine guys at Santa Paula, CA and no culprit found. Also, the condition was never able to be duplicated, yet has now happened twice relatively recently but again, not able to be duplicated. Even more frustrating is that I can't seem to find any commonality during any of the episodes.
This will be a long post, but I'm running into a frustrating brick wall of my own so I'm going to list each of the occurrences and see if the symptoms look familiar to any of you.
The engine is a stock, otherwise very smooth running A-65, metal Macauley 7445 prop. About 400 SMOH, Airwolf firewall mounted oil filter, and Brackett Air Filter, but no mods otherwise. I religiously change the oil and clean the plugs every 25 hours. I use MMO as an additive. but probably not all the time...just when I remember it, and I don't run auto gas.
July 07: Flying at the above San Joaquin Valley at about 9 am at 90-95 F and 500' agl and about 80% power, the RPM abruptly dropped from 2,000 to about 1,500 just like someone has yanked the throttle back. But, the engine continued to run smooth at that RPM. Carb heat made no difference. Once safely on the ground, a static run-up was conducted and full power was attained with no probems. The wings were still taken off and it was trucked out for inspection. The mechanics were unable to find a definitive cause, nor were they able to duplicate it.
The plane was subsequently flown for 2 years in varied summer and winterWX conditions and about 100 tach hours with no problems and then it reappeared;
June 09: It was about 2pm and 65 F here in Washington state. I took off with a student and told him to climb to 1,500' msl. Around 1,000 ft, the RPM again came abruptly back as if it were yanked by but otherwise smooth. We turned back for an uneventful landing. Carb heat made no difference, nor did retarding the throttle and reapplying it. Thank goodness, the J-3 climbs so slow that 1,000 only gets me just outside pattern range. As with before, once on the ground, a static run-up was conducted and worked normally with full RPM and good mag check/drop. This time I had a different. local antique engine and knowledgeable J-3 guy go through the engine. he said he found some minor debris in the gascolator, but nothing that would cause an immediate RPM drop. He reassembled it, and flew pattern for 30 minutes with no apparent faults.
July 09: I take off with the same student as above (he's the best 16 year old student pilot in dealing with power loss that you've ever seen
), as we climb through about 500' - 600' agl, I detect a slight roughness and drop in RPM. I immediately turned back to the runway, and with the landing assured I pulled throttle back and advanced it, with no more gain in RPM. Carb heat did nothing. Once on the ground and the throttle to idle, another run-up was done and everything checked normal. Determined to trouble shoot under controlled circumstances, I flew close in touch and goes for an hour trying to duplicate the condition, but to no avail!On a slightly unrelated note, before anyone starts sharp shooting my technique of turning to the runway, keep in mind that here in Olympia, straight ahead more than likely means you're hitting 150 - 200' trees, and much like anyone at their home airport, I've bounced around my pattern enough time to instinctively know how high I have to be and the given distance from the runway to safely make it back. That obviously wouldn't be the case at an unfamiliar airport.
So, I'm now afraid to take the plane anywhere but the pattern and still unable to either isolate or duplicate the problem. I'll be happy to answer any other questions that might assist any of you experienced A&Ps/IAs in figuring this out.
Much thanks for your expertise,
Mike-
