J Model Gross Weight STC

[John Mulvey]

I have seen a previous discussion on this forum about the STC to increase Gross Weight in J Model Moonies.  My aircraft is NOT in the favorable serial number group, so I don't know if an STC is available to me; anyone out there have a path to the higher MGW for a J Model Mooney with low serial number?  

[toto]

Someone can correct me if I'm wrong, but I believe that for the relevant serial number range, this is *not* an STC. The 2900# gross weight is part of the a/c type certificate. Some of the late J models benefit from the higher gross weight that became available for the MSE. 

[epsalant]

toto, you are right.  It's a retrofit or something like that.  I had it done on my plane by the fine folks at the KLNS MSC.  It's mostly a paperwork job, changing all the pages in the POH that contain 2740 and changing them to a page with 2900 lbs.  There's one minor thing they have to check, the rudder balance.  Mine was fine, if not they put on a washer or something to correct the rudder w&b for the new gross weight.  Oh, they also have to do a crazy silk screening of the ASI to indicate the new gross weight stall speed a knot or two faster.

IIRC it's only available to those serial numbers that had the frame beefed up but left the Mooney factory before the FAA had approved the beefed-up plane to 2900lbs.

With an empty weight of 1851, and weighing only 140lbs myself (wife smaller !) I have a major hauler on my hands !  No problem ever.  1049 lbs useful load.  Even with full fuel 665 of available load !  So that's me + 515 lbs !

I flew into LNS to get the job done 600 bs under gross, had the POH and ASI undated and hence left 760 lbs under gross, but strangely the plane performed the same :)

[ArtVandelay]

IIRC, the beefed up frame is 1 part that’s different between the models. Since it’s a landing limitation, I wonder if a document only STC could be developed so takeoff weight is 2900, landing weight remains at 2740.


Tom

[epsalant]

 BTW, I once made this excel file that I've given to a few people, very helpful for weight and balance.  It'll tell you if you are within "the box" and show you how your CG will change with fuel burn down to zero fuel.  I find it helpful.  Disclaimer--always check your POH, use this only as a supplement...

WEIGHTandBALANCE.xlsx

[KSMooniac]

Rocket Engineering got a GW increase on the J with their Missile STC, but I do not know if they actually changed anything that structurally matters like a fuselage tube, landing gear, etc. It was applicable to all J models...not just the later versions.

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[kortopates]

Yes, not an STC. Manufacturers do not use the STC process for anything. Instead they provide drawings for mods and can sell retrofit kits for the needed parts. But kits aren’t necessary as long as the changes are made in accordance to the drawing. STC’s are sought by third parties to modify the TCDS as a supplement to it.

 

As long as their has been a gross weight increase for the J’s their have been owners of older Mooney wanting to get a similar gross weight increase in some fashion. But given it never happened back in the days of when J’s sold for double of what they do today, I seriously doubt we’ll see it happen now. But sure anything is possible with enough $. Cheaper to trade up though. Years ago too, owners had a second option with the Rocket Engineering Missile mod, but that’s also gone today. We have the same issue with the K max weight gross weight being eligible only for 252’s. It raised my useful load to just under 1130 lbs.

 

 

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[PTK]

1 hour ago, KSMooniac said:

Rocket Engineering got a GW increase on the J with their Missile STC, but I do not know if they actually changed anything that structurally matters like a fuselage tube, landing gear, etc. It was applicable to all J models...not just the later versions.

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Which leads me to believe it’s not a structural thing, if I’m not mistaken. All M20J’s were eligible for the Missile conversion which got a 3200# gross. That’s a whopping 460# increase on same tubular structure!  

[kortopates]

Which leads me to believe it’s not a structural thing, if I’m not mistaken. All M20J’s were eligible for the Missile conversion which got a 3200# gross. That’s a whopping 460# increase on same tubular structure!  

I believe you are right and I am also pretty certain (but can't say 100%) that Rocket Eng did nothing for the Missile. I do know they did nothing for the Rocket. So you can interpret that way anyway you want. Mod'ed owners will claim the FAA thought it was perfectly save to add all that extra weight to the gear, in contrast to the Mooney which some and myself would interpret as being more engineering conservative and perhaps thorough. But I have noticed everyone interprets it their own way so I won't even try to justify any interpretation.

 

I can share a data point. I new one owner of an older Mooney. We shared the passion of Mooney adventure travel flying to many international destinations. In his early J, he always traveled long range with 2 couples and about the equivalent of 1 carry on roller bag per person. Yes, he was hundreds of pounds over weight! I always worried about him having a traffic pattern accident or landing incident or takeoff accident. We did some dirt field destinations together. But he was a smart guy (engineer) and a careful pilot; other than not respecting the regs concerning his plane limitations. But he never got into trouble from that and died happily in his sleep. I am not judging, but I could never take unsuspecting passengers like that and expose them unknowingly to that risk. Besides I also would hate to risk my estate to the lawsuit that would undoubtedly transpire when some lawyer figured that out. You know that will be the "cause" even if it was truly for something unrelated. NTSB findings are not admissible in court by design - perhaps civil court they are. Anyway my solution was always to get the legal increased gross weight before ever taking off overgross with a pax; lack of confidence in the airframe was never the issue for me but concern over liability I found very frightening.

 

 

 

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[John Mulvey]

So how do I pursue that?  Just ask my local mechanic?  

[toto]

16 minutes ago, John Mulvey said:

So how do I pursue that?  Just ask my local mechanic?  

 

SL92-1_SN24_1686-2999.pdf

Granted you already know that your aircraft is not eligible, I thought maybe the document would add something to the discussion..

[kortopates]

So how do I pursue that?  Just ask my local mechanic?  

Since your serial number is not listed as eligible for the higher J gross weight (2900 lbs) your only option is to trade up to a newer plane that is either elibgle or with the 2900 lb max now.
Your mechanic can only symphasize with you as their are no legal options - the Missile conversion is no longer available either.


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[PTK]

14 minutes ago, kortopates said:

I am not judging, but I could never take unsuspecting passengers like that and expose them unknowingly to that risk. 

Absolutely agree Paul. I was not in any way implying doing anything of the sort! This is purely a philosophical discussion as far as I’m concerned.

[KSMooniac]

My guess that I've stated here long ago is that it could be purely a paperwork exercise for Mooney, or an engineer that really digs into the structural details, which perhaps is what Rocket did back then. I bet Mooney bumped the J GW up when they did to offset the fat that creeped in during the 80's...sales were declining as the liability suits went crazy, and an older J at the time (which means ~10 years or less, not 40 like today!) could carry significantly more than the new ones. Voila, suddenly they have 1000+ lb useful loads again, just like my '77. But they couldn't let the early ones end up with 1150 lbs of useful load...so they have the cutover point and claimed some minor tube change in the fuselage was the reason, which would be too difficult to retrofit...

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[gacoon]

10 hours ago, John Mulvey said:

I have seen a previous discussion on this forum about the STC to increase Gross Weight in J Model Moonies.  My aircraft is NOT in the favorable serial number group, so I don't know if an STC is available to me; anyone out there have a path to the higher MGW for a J Model Mooney with low serial number?  

Mine is and I investigated about 18 months ago.  Cant remember the exact cost, but it was some insane amount.  I bagged it.

[Oldguy]

14 hours ago, kortopates said:

Since your serial number is not listed as eligible for the higher J gross weight (2900 lbs) your only option is to trade up to a newer plane that is either eligible or with the 2900 lb max now.

Or try to find a Missile for sale....

[ArtVandelay]

Or try to find a Missile for sale....

And put the IO 360 back in? I’m assuming the missile was a firewall forward only mod.


Tom

[Oldguy]

15 minutes ago, ArtVandelay said:

And put the IO 360 back in? I’m assuming the missile was a firewall forward only mod.

Tom

Along with a few other items.

http://web.archive.org/web/20070220145102/http://www.rocketengineering.com/missile/conversion.html

But the kicker is, as noted above, the GW increase was achieved with no structural modifications other than the addition of 4 engine mounts, from what I can read.

[kortopates]

Along with a few other items.
http://web.archive.org/web/20070220145102/http://www.rocketengineering.com/missile/conversion.html
But the kicker is, as noted above, the GW increase was achieved with no structural modifications other than the addition of 4 engine mounts, from what I can read.

Actually a different style of engine mount for the 6 cyl Continental.

But if you did that, the plane would revert back to it's pre-missile max gross weight - whatever it was. You don't get to keep the Missile max gross weight!


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[bradp]

Now if someone wants to dig up the approved data - ie the engineering documents that Mooney or Rocket Eng used for the gross weight increases, that could be used as a basis for a 337 or an STC to GW increase earlier J models.  It might end up with a 2900 MGTO and 2740 MAx landing weight, but the data exits. 

If a bunch of early J owners want to get together and try to find the data to develop a STC application to submit to the FAA, I’d consider that a fun project.  

Anyone on Mooneyspace a DER? 

[jetdriven]

I’m pretty sure the Feds won’t let you use STC data as approved data for your own STC. intellectual property and all.