PT20J Posted December 31, 2021 Report Posted December 31, 2021 1 hour ago, WAFI said: Am I reading this right? I have SN# 24-210, is there away with some type of landing gear mod I can get to 2900 MTOW? No. Read the whole thread. The 2900 lb upgrade had nothing to do with the landing gear. There is a SB describing which Js are eligible, and there are threads on MS that discuss it. Eligible SNs begin with 24-1686 due to a change in wall thickness of a structural tube. See TCDS snippet below. Skip 1
carusoam Posted December 31, 2021 Report Posted December 31, 2021 That is a confused airplane owner… the MGTW for the mid bodies changed with serial number and lower cage tubes… or Missile/Rocket STC.. the MGTW for the long bodies changed with different landing gear when the M20M was built… If you don’t have the proper serial number, you probably didn’t get the right tubes… Unfortunately, the Rocket engineering STC isn’t being offered for sale anymore… See what it takes to get the right tubes installed, and see if that allows for the increase in MGTW….? Invite @takair new Mooney STC idea… Know that swapping cage tubes is a really expensive endeavor… Best regards, -a- 1
1980Mooney Posted December 31, 2021 Report Posted December 31, 2021 (edited) 1 hour ago, carusoam said: the MGTW for the mid bodies changed with … or Missile/Rocket STC……Unfortunately, the Rocket engineering STC isn’t being offered for sale anymore… @WAFI And the Rocket Engineering STC SA00472SE GW Increase was NEVER applicable to standard J models. It was only applicable when completely removing the Lycoming IO-360 and replacing it with a Continental IO-550. It is totally irrelevant to any standard J. Somehow Rocket convinced the FAA 30 years ago that that even the earliest m20J’s (with a couple thinner wall tubes) could be loaded with an additional 460 lbs. without modifications. Rocket did the same thing with the M20K conversion to a Continental TSIO-520. I don’t think you will find anyone today that believes the FAA will ever approve anything like that again. Don’t even think about it as an option. Rocket has no incentive to try to apply it to all mid bodies (due to liability- 3200 lbs with only 200 hp - and only if the engine is perfect) and the FAA has no incentive to approve it for same liability reasons https://rgl.faa.gov/Regulatory_and_Guidance_Library/rgSTC.nsf/0/AFC4BFE41F13EB9885256CC1007DC951?OpenDocument Edited December 31, 2021 by 1980Mooney 1
carusoam Posted December 31, 2021 Report Posted December 31, 2021 Use caution with the wording… it is complex to write about… easy to be misunderstood… The missile STC applied to planes outside the known S/N limitation… to get the MGTW, it came as a package… including the IO550A. Kind of a really expensive work around… So… a standard M20J was known to get the increase without having the added structure of the newer fatter tubes…. Quirky oddity that got by without being rejected… It makes a great example of how large government organizations worked 30 years ago… before the internet search had a name…(?) Getting an STC today…. Same, but different… it probably doesn’t get any easier with time… Now… if an owner of an older M20J wanted to update his plane to be identical to a newer M20J… that would technically require replacing tubes. Which is done as a maintenance repair procedure… swapping like for like tubes… The hard part.. technically possible… welder with tube experience needed… Legally possible… STC writer needed… FAA possible… Review of a repair using newer parts and all of the proper methods, it’s still an M20J… Using standard M20J parts… Need to answer… how does a tube welder weld in the newer tubes… In the end… If using an IO550 is too expensive…. Swapping out tubes is going to be in the too expensive category as well… It is much more affective to buy the right plane for the mission… even if that means selling today’s steed. So I invited my favorite Mooney STC writer to join us… to see if anything makes sense from an STC writer’s point of view… Some people have had their Mooney so long… they would rather spend a ton of dough to modify it… than to swap it out for a different Mooney… Kind of a very limited market, very expensive to modify, unless insurance is paying for it… and the sheet metal is pulled away exposing the tubes… Next steps… say you got the new tubes installed in accordance with a set of maintenance documents… would that physical change automatically enable the use of the modern MGTW? (Expect not without somebody’s approval…) it would be wise to have the Mooney factory onboard for the project… and your favorite DER(?) Consult with somebody that has done this before… Go Mooney! PP thoughts only… not a mechanic. -a- 2
takair Posted December 31, 2021 Report Posted December 31, 2021 10 hours ago, carusoam said: That is a confused airplane owner… the MGTW for the mid bodies changed with serial number and lower cage tubes… or Missile/Rocket STC.. the MGTW for the long bodies changed with different landing gear when the M20M was built… If you don’t have the proper serial number, you probably didn’t get the right tubes… Unfortunately, the Rocket engineering STC isn’t being offered for sale anymore… See what it takes to get the right tubes installed, and see if that allows for the increase in MGTW….? Invite @takair new Mooney STC idea… Know that swapping cage tubes is a really expensive endeavor… Best regards, -a- Thought I had replied…hope I do t duplicate. As you say, would likely be very expensive. Mooney has the advantage of having tons of structural data on which to base a a gross weight increase. Even if we knew exactly which tubes need upgrading and even if we were able to make the mod, the FAA would expect a structural analysis of everything, not just the upgrade. Test data might suffice, but that is likely the equivalent of a drop test….might require a sacrificial airframe. Beyond the physical structure, there are the dynamics. Stall speeds…not just low speed, but accelerated. We know, for example, that Jose Monroy had to do spin testing just for his wing tanks. Not for the feint of heart. These things would all be negotiated with the FAA. Good analysis can limit some testing, but one must have a basis for the analysis. I suspect Rocket Engineering went through some of the above hoops….likely lots of analysis….which usually requires multiple engineering disciplines and much labor. I don’t think the market would be big enough today to support the required investment…one could likely find an aircraft with increased gross weight for less…. I’m sure there are companies who could do this, but it would be beyond my capabilities without others…. 1 1
WAFI Posted December 31, 2021 Report Posted December 31, 2021 12 hours ago, 1980Mooney said: @WAFI And the Rocket Engineering STC SA00472SE GW Increase was NEVER applicable to standard J models. It was only applicable when completely removing the Lycoming IO-360 and replacing it with a Continental IO-550. It is totally irrelevant to any standard J. Somehow Rocket convinced the FAA 30 years ago that that even the earliest m20J’s (with a couple thinner wall tubes) could be loaded with an additional 460 lbs. without modifications. Rocket did the same thing with the M20K conversion to a Continental TSIO-520. I don’t think you will find anyone today that believes the FAA will ever approve anything like that again. Don’t even think about it as an option. Rocket has no incentive to try to apply it to all mid bodies (due to liability- 3200 lbs with only 200 hp - and only if the engine is perfect) and the FAA has no incentive to approve it for same liability reasons https://rgl.faa.gov/Regulatory_and_Guidance_Library/rgSTC.nsf/0/AFC4BFE41F13EB9885256CC1007DC951?OpenDocument The confusing part is it seems the FAA allowed an early model thin wall tube M20J to get a heavier motor and received 2900 MGTW. Which makes no sense. That would be more structural strain with the 550 on the airframe than a thin wall tube with an IO-360. All I want is an extra 50lbs of MGTW. LOL! Which will come in time, once I get rid out all the old tech. 50lbs of usable load I mean.
1980Mooney Posted December 31, 2021 Report Posted December 31, 2021 5 hours ago, takair said: As you say, would likely be very expensive. Mooney has the advantage of having tons of structural data on which to base a a gross weight increase. Even if we knew exactly which tubes need upgrading and even if we were able to make the mod, the FAA would expect a structural analysis of everything, not just the upgrade. Test data might suffice, but that is likely the equivalent of a drop test….might require a sacrificial airframe. .. We know, for example, that Jose Monroy had to do spin testing just for his wing tanks. Not for the feint of heart. These things would all be negotiated with the FAA. Good analysis can limit some testing, but one must have a basis for the analysis. I suspect Rocket Engineering went through some of the above hoops….likely lots of analysis….which usually requires multiple engineering disciplines and much labor. I don’t think the market would be big enough today to support the required investment…one could likely find an aircraft with increased gross weight for less…. I’m sure there are companies who could do this, but it would be beyond my capabilities without others…. 1 hour ago, WAFI said: The confusing part is it seems the FAA allowed an early model thin wall tube M20J to get a heavier motor and received 2900 MGTW. Which makes no sense. That would be more structural strain with the 550 on the airframe than a thin wall tube with an IO-360. All I want is an extra 50lbs of MGTW. LOL! Which will come in time, once I get rid out all the old tech. 50lbs of usable load I mean. Look at page 64 in Flying Magazine May 1994. Darwin Conrad, founder of Rocket Engineering said there were 1,200 flight-testing hours conducted on the Rocket STC. It is probably even more difficult today. Flying Magazine - Google Books 3
A64Pilot Posted January 1, 2022 Report Posted January 1, 2022 (edited) You would be surprised at how little actual data a small Manufacturer has, Design can be done by analysis, but it takes a LOT of work and analysis requires a larger “scatter factor” meaning a larger margin. Most of the time it’s much easier and cheaper to just pull the thing. Very rarely is a structure pulled to failure, almost always it’s pulled to ultimate load and if it doesn’t break it passes, if it breaks you weld in a thicker tube and re-pull it. It’s very difficult and expensive to design structure to the point where everything is just barely strong enough, so in order to save time and money you build something that your awfully sure will pass, so most of the time there can be a rather large margin. The big boys like Airbus, Boeing etc can design to very close tolerances, but the little guys with a one or two man Engineering dept just can’t. This is why so many small airplanes can have BIG motor STC’s etc and don’t suffer structural failure from the greatly increased weights and aerodynamic loads from higher air speeds. Personally I worry about aft CG and aircraft performance at higher weight in a stock non modified aircraft, but I don’t worry much about actual weight. Vast majority of GA aircraft if flown within a reasonable envelope run out of performance before they reach a structural limit. I fly a heavily loaded aircraft differently then a light weight one, just as I drive a heavy pick up truck differently. Put a 550 in a C-182 and you might can load it with enough weight to break it, but the stock configuration will probably run out of excess power first. Personal opinion only of course. Edited January 1, 2022 by A64Pilot 1
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