birdy
Active Member
- Joined
- Mar 19, 2004
- Messages
- 7,066
- Location
- Alice Springs-central Oz.
- Aircraft
- open frame single seat & a 'wasa' RAF, among other types.
- Total Flight Time
- 7000 odd, bout 5000 gyro
Gday crew, Iv had sum perplexing issues lately with a constant speed 914.
firstly, I received this machine 2nd hand with < 200 hours on the engine, and I don’t think the previous operator knew much about anythn mechanical.
Had no issues for the first 500 odd hours, cept for a slight oil weep from the cold side of the turbo.
then a few hours back I just happened to notice the oil pressure was off the dial???
quickly put it down, and as the rpm came down, so did the oil pressure. It sat at normal hot oil pressure at idle, and after checkn a few things I spun up to 100%, pressure still good so took off again. After a short while the pressure started to climb again, two steps forward, one step back, till it was off the dial again, so I made a dash for home.
pressure came down wen I reduced throttle as before.
not sure wot pressure it went to coz the vdo only go’s to 90odd psi and it went way past that.
anyway, abit of checking and it turned out the rotax recommended replacement relief valve ( mushroom shape replaced the ball) was sumhow jammen closed, in flight. Coz the fix was to put the old ball back in, all normal again.
id pay handsomely to anyone who can give a credible explanation for how an oil relieve valve can slowly close while runin at a constant rpm.
second issue was the turbo started pumpin oil out both sides after the oil pressure issue.
sumthn went throo the scavenge pump rotor, from the turbo sump and scoured it badly, but after replacing with new rotor and body, the scavenge pump is workin as it should but oil was still leakin from both sides of the turbo.
report from the turbo doc was both bearings, shaft and seal in the turbo are rooted.
not sure wot the sequence was, turbo leaked oil, it burned and scoured the bit, or the bits failed and oil
Leaked, or sumthn dislodged from the turbo and stuffed everythn down stream of it, or the over pressurised oil system caused this chain reaction, or, or......
anyway, turbo is being rebuilt, so we will see wot happens next.
still like to no how the oil pressure went off?
firstly, I received this machine 2nd hand with < 200 hours on the engine, and I don’t think the previous operator knew much about anythn mechanical.
Had no issues for the first 500 odd hours, cept for a slight oil weep from the cold side of the turbo.
then a few hours back I just happened to notice the oil pressure was off the dial???
quickly put it down, and as the rpm came down, so did the oil pressure. It sat at normal hot oil pressure at idle, and after checkn a few things I spun up to 100%, pressure still good so took off again. After a short while the pressure started to climb again, two steps forward, one step back, till it was off the dial again, so I made a dash for home.
pressure came down wen I reduced throttle as before.
not sure wot pressure it went to coz the vdo only go’s to 90odd psi and it went way past that.
anyway, abit of checking and it turned out the rotax recommended replacement relief valve ( mushroom shape replaced the ball) was sumhow jammen closed, in flight. Coz the fix was to put the old ball back in, all normal again.
id pay handsomely to anyone who can give a credible explanation for how an oil relieve valve can slowly close while runin at a constant rpm.
second issue was the turbo started pumpin oil out both sides after the oil pressure issue.
sumthn went throo the scavenge pump rotor, from the turbo sump and scoured it badly, but after replacing with new rotor and body, the scavenge pump is workin as it should but oil was still leakin from both sides of the turbo.
report from the turbo doc was both bearings, shaft and seal in the turbo are rooted.
not sure wot the sequence was, turbo leaked oil, it burned and scoured the bit, or the bits failed and oil
Leaked, or sumthn dislodged from the turbo and stuffed everythn down stream of it, or the over pressurised oil system caused this chain reaction, or, or......
anyway, turbo is being rebuilt, so we will see wot happens next.
still like to no how the oil pressure went off?