Glen Davis Posted November 12, 2020 Report Posted November 12, 2020 When pre-flighting yesterday, I stood behind the aircraft on the co-pilot side, grabbed the horizontal section of the elevator, moved it up and down and found it had about 1/2 inch play. What is the allowable tolerance of movement? The other side was about the same. Quote
N201MKTurbo Posted November 12, 2020 Report Posted November 12, 2020 You should measure it. It may be less than you think. if it is actually 1/2 inch, you should fix that. 1 Quote
carusoam Posted November 12, 2020 Report Posted November 12, 2020 Glenn, This is a pre-flight step... grab the rudder from the bottom and lift up... measuring from both sides...? Seems to be the same, because you are measuring the same thing twice... The movement... It’s actually not too hard to measure... See Skips details above... A little wear in the bolt turns into a lot of motion... As far as swapping out the old part goes... it takes some effort... but not terrible... My 65C moved a lot... but without measuring it... it felt like a lot more than it was actually moving... A new long Body barely moves at all... you will be able to perceive that it moves, but it feels like a tenth of an inch... Al Mooney famously replaced the bolt with one a diameter size smaller to generate intentional slop... proving that when the system wears, it doesn’t become an immediate hazard to flight... So... Measure it twice... Then plan the parts swap... Best regards, -a- Quote
Ragsf15e Posted November 12, 2020 Report Posted November 12, 2020 29 minutes ago, carusoam said: Glenn, This is a pre-flight step... grab the rudder from the bottom and lift up... measuring from both sides...? Seems to be the same, because you are measuring the same thing twice... The movement... It’s actually not too hard to measure... See Skips details above... A little wear in the bolt turns into a lot of motion... As far as swapping out the old part goes... it takes some effort... but not terrible... My 65C moved a lot... but without measuring it... it felt like a lot more than it was actually moving... A new long Body barely moves at all... you will be able to perceive that it moves, but it feels like a tenth of an inch... Al Mooney famously replaced the bolt with one a diameter size smaller to generate intentional slop... proving that when the system wears, it doesn’t become an immediate hazard to flight... So... Measure it twice... Then plan the parts swap... Best regards, -a- I think (but could possibly be wrong) @carusoamand the OP are talking about two different “slops” in the tail... from the OP, he grabbed the elevator, so I think he was talking about slop in either his control hinges or in the elevator control rods. I think that matches up to what @PT20Jposted. the Slop Anthony mentioned is found by grabbing under the tail, behind the tail tiedown and lifting the entire empennage section. You should hear a thunk and perceive a very small movement. Not being a mechanic, I haven’t figured out what this is telling me or how to know if it’s good or bad , but I hope to learn that soon. Anyone? 1 Quote
MikeOH Posted November 12, 2020 Report Posted November 12, 2020 10 minutes ago, Ragsf15e said: I think (but could possibly be wrong) @carusoamand the OP are talking about two different “slops” in the tail... from the OP, he grabbed the elevator, so I think he was talking about slop in either his control hinges or in the elevator control rods. I think that matches up to what @PT20Jposted. the Slop Anthony mentioned is found by grabbing under the tail, behind the tail tiedown and lifting the entire empennage section. You should hear a thunk and perceive a very small movement. Not being a mechanic, I haven’t figured out what this is telling me or how to know if it’s good or bad , but I hope to learn that soon. Anyone? I am a little confused as to what the OP was referring to, as well. I think the excerpt from PT20J is actually a THIRD 'slop' limit: note it refers to the horizontal STABILIZER (NOT elevator, NOR the tail assembly you refer to), and it is allowed movement at the TIP. Unfortunately, I can't point to specifications (except PT20Js) but I check three items during preflight: 1) I grab under the tail section like you do, and lift. I'm checking for how much free play and I use the limit of 0.125" (1/8 inch), but I can't tell you where I got that number. At my first annual I was told it was excessive and had the issue fixed. There is NO perceptible slop now. 2) I'll grab the left elevator in my left hand and the right one in my right hand and check for the slop when I more them in opposite directions. There's a very slight amount of play but I can't quantify it, but I'm really looking for a big change to indicate something has changed significantly. 3) As I walk around the tail I try to move the horizontal stabilizer up and down by the tip. There's just the slightest amount of slop there. I'd be concerned if I ever felt much more than that. I've never tried moving the tips fore and aft, however. May have to check that... 1 Quote
PT20J Posted November 12, 2020 Report Posted November 12, 2020 The section of the service and maintenance manual I posted specifies the limits for movement at the empennage attachments. If the issue is the elevator itself, I don't know of any limits. The left and right elevators are connected via tubes and rod ends and there will be some very slight movement noticed if one is held while you try to to deflect the other. The elevator is free to move up and down to the stops, but the trim bungees will rapidly add increasing force as you move away from the trimmed position. The low bungee force at the trim point that rapidly increases with deflection in either direction could feel like slop if you are comparing the feel to something like a C-172 that has no springs. Skip 2 Quote
larrynimmo Posted November 12, 2020 Report Posted November 12, 2020 If you grab the elevator by the side, there is flex...a natural design characteristic...but in my plane there is no slop or free play from loose or worn bolt Quote
M20F-1968 Posted November 12, 2020 Report Posted November 12, 2020 If you are grabbing the horizontal stabilizer you are testing play at the "Jesus bolts." if there is a 1/2 of play you are in trouble. If you are grabbing the empennage below the rudder, you are testing either play in the trim or the Jesus bolt. The Jesus bolts (one each side) are structural, minimal tolerance bolts that should show almost no play at all. Rather than guess, have someone who knows the Mooney airframe to take a look at it. John Breda 2 Quote
Immelman Posted November 12, 2020 Report Posted November 12, 2020 I usually lift the empennage a bit during walkaround by placing a hand under the tail cone... I seldom push the horizontal stabilizer much. Last annual: Inspector found up & down play in the horizontal stab. One of the "Big" bolts back there had wear. Glad they found it! Was not a huge deal to fix. 1 Quote
cliffy Posted November 15, 2020 Report Posted November 15, 2020 If the horizontal stabilizer tip moves more than specified in the MM you have wear in the two hinge bolts OR someone has changed them to standard AN bolts. They are actually "close tolerance" bolts (they have a triangle symbol stamped on the head around the "x" mark of a normal AN bolt), Found 1/2" of play in one Mooney a few years ago and it turned out that the bolts had been changed to regular ANs. Put in close tolerance bolts and the play went away. You can visually check to see if the close tolerance bolts are in there by taking off the tail cone. Also pay attention to lubing those bolts every chance you get. I actually "quietly" check for that play in every Mooney I walk past. Just a habit of mine. Its unclear just what the OP was looking at. Quote
Missile=Awesome Posted November 16, 2020 Report Posted November 16, 2020 18 hours ago, cliffy said: If the horizontal stabilizer tip moves more than specified in the MM you have wear in the two hinge bolts OR someone has changed them to standard AN bolts. They are actually "close tolerance" bolts (they have a triangle symbol stamped on the head around the "x" mark of a normal AN bolt), Found 1/2" of play in one Mooney a few years ago and it turned out that the bolts had been changed to regular ANs. Put in close tolerance bolts and the play went away. You can visually check to see if the close tolerance bolts are in there by taking off the tail cone. Also pay attention to lubing those bolts every chance you get. I actually "quietly" check for that play in every Mooney I walk past. Just a habit of mine. Its unclear just what the OP was looking at. We got us a tail lifter...perv. Quote
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