Marauder Posted January 30, 2017 Author Report Posted January 30, 2017 Ok, another update. I went through the entire engine compartment. I pushed and pulled on everything. There is nothing loose. I also determined on my 75 F, the lower cowl is held in place by two attachment points on the firewall, the bracket I showed above and the mechanical connections of the oil cooler, ram air boot, landing light and the air box containing the filter. There is nothing else. The lower cowl will move a lot as shown above. However, when the cowl is assembled, it is rock solid. Absolutely no play at all. The engineers who designed the cowl were amazing. I took a few pictures of the bracket in the center of the lower cowl. Also borescoped everything to see if I could find any issues. After reassembling the cowl, I had my CFII buddy fly with me in a cruise mode. He has probably a 100 hours in the plane with me over the past 20 years. He thinks I am nuts. Yesterday I flew up to Williamsport PA in his plane. I will admit my F is smoother than his J but I still think it is vibrating more now. One thing I did do is paint all of the nicks on the lower cowl enclosure. Including plastic welding the big nick I showed above. I will fly it some more and see if the rubbing of the lower cowl enclosure comes back. 1 Quote
carusoam Posted January 30, 2017 Report Posted January 30, 2017 Have you checked the parts manual for the lower cowl support rods? If you don't have them, I think you may want to see if they are supposed to be there. The sheet metal is pretty strong and probably doesn't notice the rods missing when all buttoned up properly. That would lead to the next question... why is it not buttoning up the same way as the last 24 years? Any loose cowl fasteners? PP thoughts, not the mechanic... Best regards, -a- Quote
Marauder Posted January 30, 2017 Author Report Posted January 30, 2017 Have you checked the parts manual for the lower cowl support rods? If you don't have them, I think you may want to see if they are supposed to be there. The sheet metal is pretty strong and probably doesn't notice the rods missing when all buttoned up properly. That would lead to the next question... why is it not buttoning up the same way as the last 24 years? Any loose cowl fasteners? PP thoughts, not the mechanic... Best regards, -a- I don't think any of the F models had support rods that were shown earlier. I do believe my mounts are still suspect since the clearance is definitely tight.I really went through the compartment carefully over the weekend. No fasteners are missing, no parts are loose and nothing looks amiss. At this point, I will continue to monitor the situation.Sent from my iPad using Tapatalk Quote
Browncbr1 Posted January 30, 2017 Report Posted January 30, 2017 My 67 has the support rods on both sides of the lower cowl. If they weren't there, the cowl would just flop down. Quote
Marauder Posted January 30, 2017 Author Report Posted January 30, 2017 My 67 has the support rods on both sides of the lower cowl. If they weren't there, the cowl would just flop down. I don't ever recall seeing them on the 74 through 76 F models. Wonder if they discontinued using them. Do you have a picture where they attached? Wonder if they were removed.Sent from my iPad using Tapatalk Quote
Browncbr1 Posted January 30, 2017 Report Posted January 30, 2017 2 hours ago, Marauder said: I don't ever recall seeing them on the 74 through 76 F models. Wonder if they discontinued using them. Do you have a picture where they attached? Wonder if they were removed. Sent from my iPad using Tapatalk I know they were omitted on J's because of the different cowl design/fiberglass, but I'm worried that you may be missing these critical parts. They make the lower cowl rigid even with cheeks and top of cow are removed. This is the best photo I could find, which has the lower cowl removed, but these tubular steel cow stays are still on there. They connect the upper firewall to the lower front lip where the cheeks attach. Quote
Marauder Posted January 30, 2017 Author Report Posted January 30, 2017 I know they were omitted on J's because of the different cowl design/fiberglass, but I'm worried that you may be missing these critical parts. They make the lower cowl rigid even with cheeks and top of cow are removed. This is the best photo I could find, which has the lower cowl removed, but these tubular steel cow stays are still on there. They connect the upper firewall to the lower front lip where the cheeks attach. Nope, never had them. The plane had 3 annuals at MSCs during my 26 years of ownership and it was never mentioned. Hopefully Yetti, Guitarman and/or TTaylor can confirm they either have them or not. They are all 75 models.Sent from my iPad using Tapatalk Quote
Guitarmaster Posted January 30, 2017 Report Posted January 30, 2017 I most definitely do not have those bars. Going from memory; to remove the lower cowl: six or eight sheet metal screws along the bottom where it attaches to the fuselage. Remove oil cooler. Disconnect landing light and ram air. Remove four bolts from the intake boot and the cowling drops right off. I don't think your problem is the cowling Chris. 1 Quote
Jim F Posted January 30, 2017 Report Posted January 30, 2017 Hi Chris, i am a little late to the game. In the photos the pilots right side showed that the bafful was hitting the engine mount. The air pressure in the upper cowl will push the bafful aft. For test you can slide some rubber in between and fly to see if it's better. I have some questions on when the vibration shows up and where you feel it most. Do you notice it in your feet when they on the cabin floor or in your gut? Frequency, does it feel one to one with the prop, higher, lower? In cruise cowl flaps closed or open a bit. Which is worse in cruise pull up push down. Which is worse in cruse bank right and left. Which is worse check nose gear doors, all of the lower belly panels, and that the flaps are up tight both sides Regards, jim Quote
Marauder Posted January 30, 2017 Author Report Posted January 30, 2017 Hi Chris, i am a little late to the game. In the photos the pilots right side showed that the bafful was hitting the engine mount. The air pressure in the upper cowl will push the bafful aft. For test you can slide some rubber in between and fly to see if it's better. I have some questions on when the vibration shows up and where you feel it most. Do you notice it in your feet when they on the cabin floor or in your gut? Frequency, does it feel one to one with the prop, higher, lower? In cruise cowl flaps closed or open a bit. Which is worse in cruise pull up push down. Which is worse in cruse bank right and left. Which is worse check nose gear doors, all of the lower belly panels, and that the flaps are up tight both sides Regards, jim Hi Jim -- I will look at the baffling a bit closer and see if I can find areas that may be rubbing. As for the vibration, funny you asked about the floor. When my buddy and I flew, it commented he didn't feel anything different in his feet. Since he is usually sitting there with his feet flat on the floor, he should know.The vibration is a constant, I first noticed it on the seat. My butt felt it. I also saw the compass has a little bit more vibration to it and a little bit more on the yoke. The cowl flaps can be open or closed, no difference. Seems to get a bit worse with more airspeed, but only if I leave the power in. Not as noticeable in a bank.Power settings for approach makes it less noticeable as well. That is why my buddy never made a comment during the IPC. With the exception of the short climbs, we weren't in cruise power.I cleaned the belly yesterday and didn't see anything amiss. Sent from my iPad using Tapatalk Quote
Guitarmaster Posted January 30, 2017 Report Posted January 30, 2017 Hi Jim -- I will look at the baffling a bit closer and see if I can find areas that may be rubbing. As for the vibration, funny you asked about the floor. When my buddy and I flew, it commented he didn't feel anything different in his feet. Since he is usually sitting there with his feet flat on the floor, he should know.The vibration is a constant, I first noticed it on the seat. My butt felt it. I also saw the compass has a little bit more vibration to it and a little bit more on the yoke. The cowl flaps can be open or closed, no difference. Seems to get a bit worse with more airspeed, but only if I leave the power in. Not as noticeable in a bank.Power settings for approach makes it less noticeable as well. That is why my buddy never made a comment during the IPC. With the exception of the short climbs, we weren't in cruise power.I cleaned the belly yesterday and didn't see anything amiss. Sent from my iPad using Tapatalk You cleaned the belly?? Well played! Lol!Sent from my XT1585 using Tapatalk Quote
Marauder Posted January 30, 2017 Author Report Posted January 30, 2017 You cleaned the belly?? Well played! Lol!Sent from my XT1585 using Tapatalk Yep, checked in each of the fat folds as well. Sent from my iPad using Tapatalk 1 Quote
carusoam Posted January 30, 2017 Report Posted January 30, 2017 (edited) 1) looks like the cowl has been established as being in the right place. 2) how do we check if the motor is really sagging? Level the plane, then check the level of the engine? 3) The only thing left is to pull the motor rubber pads for a better look at the rubber. Or add shims. The rubber parts can get split this might be a hint of what happened. 4) What is the shimming procedure? This may give a hint to measuring how much the engine is drooping. 5) Is There a maximum thickness shim allowed? If the droop is larger than the thickest shim, This would be another hint of something other than worn mounts... PP ideas being shared, not a mechanic. Best regards, -a- Edited January 30, 2017 by carusoam Quote
Jim F Posted January 30, 2017 Report Posted January 30, 2017 4 hours ago, Marauder said: Hi Jim -- I will look at the baffling a bit closer and see if I can find areas that may be rubbing. As for the vibration, funny you asked about the floor. When my buddy and I flew, it commented he didn't feel anything different in his feet. Since he is usually sitting there with his feet flat on the floor, he should know. The vibration is a constant, I first noticed it on the seat. My butt felt it. I also saw the compass has a little bit more vibration to it and a little bit more on the yoke. The cowl flaps can be open or closed, no difference. Seems to get a bit worse with more airspeed, but only if I leave the power in. Not as noticeable in a bank. Power settings for approach makes it less noticeable as well. That is why my buddy never made a comment during the IPC. With the exception of the short climbs, we weren't in cruise power. I cleaned the belly yesterday and didn't see anything amiss. Sent from my iPad using Tapatalk Ok check and wiggle all of the baffuling. Your comment that you feel it a little more with more airspeed could match baffuling as the pressure in the upper plenum increases slightly with airspeed. You can take a black sharpie and blacken the bafful where you think in might be hitting. Fly and then uncowl and look for the witness mark. More on where you feel the vibration. Get the plane in cruise and trued up. Pick your feet off the floor. Touch the center windshield frame member. Can you reach under the left side side panel and feel the frame member? Touch the seat tracks behind both seats. Touch the pilots yoke then copilot. I don't believe that engine mount sag on the ground translates to inflight sag. New mounts do a better job of engine vibration isolation but do nothing for any other induced vibration. Good luck jim 1 Quote
Yetti Posted January 31, 2017 Report Posted January 31, 2017 No rods on my F. The lower cowl is connected to the front shroud that connects to the cylinder heads. 1 Quote
Mooneymite Posted January 31, 2017 Report Posted January 31, 2017 22 hours ago, Marauder said: The vibration is a constant, I first noticed it on the seat. My butt felt it. I also saw the compass has a little bit more vibration to it and a little bit more on the yoke. The cowl flaps can be open or closed, no difference. Seems to get a bit worse with more airspeed, but only if I leave the power in. Not as noticeable in a bank. Chris, after reading this thread, it's possible you're looking at the wrong end of your plane.....instead of the engine compartment, maybe you should be checking the tail? The fact that the vibration decreases in a bank (presumably when more back pressure is applied to the elevator), may be a huge clue. A tiny wiggle in the tail can cause a lot of vibration....especially as indicated airspeed increases. 3 Quote
Marauder Posted January 31, 2017 Author Report Posted January 31, 2017 Chris, after reading this thread, it's possible you're looking at the wrong end of your plane.....instead of the engine compartment, maybe you should be checking the tail? The fact that the vibration decreases in a bank (presumably when more back pressure is applied to the elevator), may be a huge clue. A tiny wiggle in the tail can cause a lot of vibration....especially as indicated airspeed increases. Good thought Gus. I haven't look at the tail other than my normal preflight. Sent from my iPad using Tapatalk Quote
xcrmckenna Posted January 31, 2017 Report Posted January 31, 2017 What about one of your gear doors? Could one be loose? And in a bank the air flow holds it agains the belly tighter? Sent from my iPhone using Tapatalk Quote
Marauder Posted January 31, 2017 Author Report Posted January 31, 2017 What about one of your gear doors? Could one be loose? And in a bank the air flow holds it agains the belly tighter? Sent from my iPhone using Tapatalk When I did the belly cleaning I checked everything underneath. Nothing noted other than it may be time to paint my wheel wells. Sent from my iPad using Tapatalk 1 Quote
Jim F Posted January 31, 2017 Report Posted January 31, 2017 2 hours ago, Marauder said: When I did the belly cleaning I checked everything underneath. Nothing noted other than it may be time to paint my wheel wells. Sent from my iPad using Tapatalk Hi Chris, I would bet it's up front because that's there the majority of the noise makers are. On main gear doors usually the vibration will increase in a bank because cintifical force is pulling the gear out of the wells. One more check when you fly to look at the airframe you can do is with one finger load the yoke right then left, down up, same with rudder but use your foot. The best way is have your copilot do it and you close your eyes. I know it sounds weird. This would be a rodend sloppy and the control serface causing the vibration. Big hitters on the airframe are loose panels, gear doors, flaps. see ya Jim Quote
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