DC_Brasil Posted November 20 Report Posted November 20 Hello everyone. I am having my 1990 M20J go through the 2900lbs gross weight increase procedure as per SL92-1. The shop is doing the rudder balance check as directed by SB-M20-252 but the rudder seems to be out of specs: the measured moment is not within limits and we'd need to add weight to the rudder horn counterweight. As we're discussing the best approach to fall within limits, I am suspecting the plane has been painted with a heavy coat in the past (before I purchased it) and it is affecting the surface weight. However, since I live in Brazil and there are very few Mooneys around here, I suspect there is also a possibility that the A&Ps at the shop aren't measuring the distance to calculate moment at the correct spot. Consequently, I'd like to ask members here if someone might have pictures of this balancing procedure and where they actually measured the underbalance weight. Thanks!
cliffy Posted November 20 Report Posted November 20 Very detailed balancing instructions are shown in section 27-93-01 of the Mooney J maintenance manual available right here on MS in DOWNLOADS (up top on drop down menu for Browse) It is very serial number specific - so check carefully. If its out of spec it is probably too much paint.
DC_Brasil Posted November 20 Author Report Posted November 20 I have downloaded and have read the manual. The only question I have - and I want to check the mechanics are doing it right - is where along the length of the rudder is the correct spot put the scale support point (in red in the image below).
PT20J Posted November 20 Report Posted November 20 It doesn’t matter where along the span you measure the force so long as you accurately measure the distance between the scale and hinge line in order to calculate the moment. I would just put the scale approximately in the center between the two hinges. 1
Aerodon Posted November 20 Report Posted November 20 6 hours ago, DC_Brasil said: Hello everyone. I am having my 1990 M20J go through the 2900lbs gross weight increase procedure as per SL92-1. The shop is doing the rudder balance check as directed by SB-M20-252 but the rudder seems to be out of specs: the measured moment is not within limits and we'd need to add weight to the rudder horn counterweight. As we're discussing the best approach to fall within limits, I am suspecting the plane has been painted with a heavy coat in the past (before I purchased it) and it is affecting the surface weight. However, since I live in Brazil and there are very few Mooneys around here, I suspect there is also a possibility that the A&Ps at the shop aren't measuring the distance to calculate moment at the correct spot. Consequently, I'd like to ask members here if someone might have pictures of this balancing procedure and where they actually measured the underbalance weight. Thanks! Hi DC, The Mooney balance instructions are rather hard to read. They have a 'known weight' and variable distance method as well as 'absolute limits'. I prefer absolute limits as it is more consistent with other manufacturers procedures. I did a gross weight increase on a 252 to Encore. Similar procedure. The process called for a 'more balanced' rudder and a new part number for the lower balance weight. I installed the new lower balance weight and it balanced within limits without further ado. Your mod is similar, it also calls for a new balance weight, I assume it's the lower balance weight, not the rudder horn balance weight? If you have not installed it, I am not surprised that you are out of balance? To say it another way, if you have not changed the weight already, and your shop is trying to balance the rudder to the new specs, you should not be surprised that it is out of balance. I can't remember where the lower balance weight is, I will go look later. Aerodon
cliffy Posted November 20 Report Posted November 20 On the SB 20-252 paragraphs 4-8 deal specifically with the rudder balance being "out" of limits The SB itself deals with rudder balance on Gross Weight Increase Google it 1
DC_Brasil Posted November 22 Author Report Posted November 22 I have had a back-an-forth with Mooney support as well. My rudder is out of specs. I discovered it has been painted in the past without stripping the old paint and that is what is probably making it too heavy. I'll have to strip the paint, repaint it and redo the static balance check 2
ArtVandelay Posted Saturday at 08:29 PM Report Posted Saturday at 08:29 PM I have had a back-an-forth with Mooney support as well. My rudder is out of specs. I discovered it has been painted in the past without stripping the old paint and that is what is probably making it too heavy. I'll have to strip the paint, repaint it and redo the static balance check When I had my plane repainted, I also made sure not to add stripes, decals etc to the rudder which would add weight.
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