jcarter Posted September 29, 2014 Report Posted September 29, 2014 Hello All, (I've posted in the general section as similar trim issues probably apply to all models) Intro... I've had a beautiful '67 F for 4 years based here in the UK. I regularly use the machine for airways trips around Europe in the FL80-160 range, quite frequently between the UK and Germany. The Mooney flies sweetly and it very stable. When trimmed, its doesn't drift. On the Ground the tailplane assembly has minimal play. Most flights are pretty much hands off, being flown with the KFC200 AP. Issue... I've noticed when in the descent from the flight levels, which I'd usually do with power (say 20 inches MP), I obviously trim for the descent to relieve my arm in pitch down input but I run out of pitch down trim. As I trim down with the electric trimmer (left thumb) I can feel the the manual pitch trim wheel turning and it will eventually stop at its limit -and indeed, when i leave the electric trim and try the wheel manually, it doesn't go any further (i.e. the electric trimmer has taken the trim to its full down position) and beyond that, I don't force it obviously. So in other words with full trim forward in a 'with power' descent, hands off, the max rate of descent is about 400FPM. If i need a faster rate of descent, I need to hold the yolk forward with a little more pitch down. Its not a big issue, but in a descent from say FL140 at a high-ish rate of descent, my arm aches eventually! Obviously, I could cut more power and this would aid the rate of descent (slower aircraft = less lift and all that) but I presume i should have trim range which allows me to fly in a powered descent at >500FPM fully trimmed (i.e. without having to hold further pitch down 'manually') I'm guessing that, over the years, some kind of trim adjustment has become needed so the trimmer is 'centred' and I get as much 'down' as well as 'up'? At the moment I seem to lack pitch down trim travel. Has anyone any experience of this or its fix or other comments / knowledge which would help my understanding? Thanks for taking the time! Justin Carter
N201MKTurbo Posted September 29, 2014 Report Posted September 29, 2014 I would guess the trim jack screw is out of sync with trim wheel assembly. I assume you have plenty of up trim when landing. Where is the trim indicator when you take off. Does it take off without much effort or does it seem out of trim on takeoff?
carusoam Posted September 29, 2014 Report Posted September 29, 2014 Welcome aboard Justin, This is the first time I have heard of this situation. Most Mooney pilots usually comment how they cannot get enough up trim in the traffic pattern. How long has the KFC200 been installed? Not a very common device in '67 Mooneys? One of the common situations regarding Mooney trim screws is the age of the grease that may have accumulated on the threads. This is something you can check while on the ground. Using the hand wheel, operate the trim from one end to the other. It should operate smoothly and pretty easily. Of course a visual inspection would be good at this time as well. Keep in mind I am a private pilot and not a mechanic... Best regards, -a-
Bob_Belville Posted September 29, 2014 Report Posted September 29, 2014 My E will trim down to red line IAS (and, I'm sure, to beyond red line).
John Pleisse Posted September 29, 2014 Report Posted September 29, 2014 From level cruise trim, a simple reduction to 20" mp should give you a hands off -500fpm decent. No trim changes...just a simple power reduction and the nose will lower. Please clarify....you are getting 20"mp at 17,000 msl??? 2
Guest Posted September 29, 2014 Report Posted September 29, 2014 Hello All, (I've posted in the general section as similar trim issues probably apply to all models) Intro... I've had a beautiful '67 F for 4 years based here in the UK. I regularly use the machine for airways trips around Europe in the FL80-160 range, quite frequently between the UK and Germany. The Mooney flies sweetly and it very stable. When trimmed, its doesn't drift. On the Ground the tailplane assembly has minimal play. Most flights are pretty much hands off, being flown with the KFC200 AP. Issue... I've noticed when in the descent from the flight levels, which I'd usually do with power (say 20 inches MP), I obviously trim for the descent to relieve my arm in pitch down input but I run out of pitch down trim. As I trim down with the electric trimmer (left thumb) I can feel the the manual pitch trim wheel turning and it will eventually stop at its limit -and indeed, when i leave the electric trim and try the wheel manually, it doesn't go any further (i.e. the electric trimmer has taken the trim to its full down position) and beyond that, I don't force it obviously. So in other words with full trim forward in a 'with power' descent, hands off, the max rate of descent is about 400FPM. If i need a faster rate of descent, I need to hold the yolk forward with a little more pitch down. Its not a big issue, but in a descent from say FL140 at a high-ish rate of descent, my arm aches eventually! Obviously, I could cut more power and this would aid the rate of descent (slower aircraft = less lift and all that) but I presume i should have trim range which allows me to fly in a powered descent at >500FPM fully trimmed (i.e. without having to hold further pitch down 'manually') I'm guessing that, over the years, some kind of trim adjustment has become needed so the trimmer is 'centred' and I get as much 'down' as well as 'up'? At the moment I seem to lack pitch down trim travel. Has anyone any experience of this or its fix or other comments / knowledge which would help my understanding? Thanks for taking the time! Justin Carter Justin, Your trim does not sound correct. You will need to find someone with the correct Mooney travel and rigging board for your plane and have the rigging of the tail checked. Either the stops are set incorrectly or the neutral position is wrong. Clarence
takair Posted September 29, 2014 Report Posted September 29, 2014 Someone mentioned above, 5" manifold pressure should give you 500fpm with no trim change and it should roughly maintain cruise speed. Are you trying to go faster than cruise while descending? This is the only time you should need any trim. What kind of cruise speed are you getting. Something doesn't sound right....
Hank Posted September 30, 2014 Report Posted September 30, 2014 I descend with cruise MP at 500 fpm every time I fly. The only time I reduce throttle in the descent is if I start down late. Yes, I walk the throttle out and the mixture in as I come down to maintain cruise settings on MP and EGT, but no reduction to descend. This usually puts me around 170 MPH indicated, and groundspeed can exceed 200 knots. Wheeee!! If you can't descend with MP reduced and full nose-down trim, there's a problem. Next time I'm out, I'll check the trim position at 500 fpm, I've never paid the indicator any attention. Time to descend means push forward to establish 500, then trim the force away from the yoke. Works well whether I'm cruising at 11,000 msl or 3000 msl. I would start by running full trim down on the ground, and check position of the indicator, then remove the belly and check the jack screw. Old grease builds up there, increasing required force and possibly limiting travel. Good luck, and keep us posted!
John Pleisse Posted September 30, 2014 Report Posted September 30, 2014 5" manifold pressure should give you 500fpm with no trim change and it should roughly maintain cruise speed. No...not speed...you added that. Just a decent r-a-t-e.
takair Posted October 1, 2014 Report Posted October 1, 2014 No...not speed...you added that. Just a decent r-a-t-e. Not sure I follow. The airplane attempts to settle at its trim speed, which results in a descent while roughly maintaining trim speed. Add power and it climbs while trying to maintain trim speed... Not precise, but close...
justincarter Posted October 1, 2014 Report Posted October 1, 2014 Thanks everyone, To answer some of the queries... I probably get about 20inches at FL120. I don't seem to lack up trim. It handles well in all phases - including take off. I think (but ill have to check) the trim indicator is below the centre marker on take off -so i guess that might suggest the trim run isn't centred? Ill run the trim manually on the ground end to end and report back- as well as checking the trim marker position on T/O and level flight. (I suppose it should be up on T/O and centred on level flight) Cruise speed - 130Kts indicated at WOT, 50-75F ROP, 2400 rpm at FL100-110 I like the idea that I may be hitting an artificial trim stop early (on trimming down) due to an old block of grease. As mentioned in a previous thread i found.... http://mooneyspace.com/topic/12162-running-out-of-trim-as-speed-passes-175-mph/ Looks like a careful inspection is in order- the annual is up-coming
Hank Posted October 1, 2014 Report Posted October 1, 2014 When flying light, I set trim just ABOVE the takeoff mark. Like tonight, going solo to warm the engine and drain the oil. On landing, often half flaps but sometimes more, the indicator is usually right near the Takeoff mark again. Good luck with the jack screw cleaning!
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