Vernier throttle for early 231's

[231LV]

My mechanic has searched high and low for a vernier throttle cable for my 1980 231. At engine overhaul when I upgraded the GB to an LB, I also put a Merlin Black Magic wastegate in. Anyone who has flown the merlin knows it is  not an automatic wastegate like the MB engined K models and requires a delicate touch to avoid overboosting the engine. Hence, a vernier throttle would make management of a Merlin wastegate equipped TSIO 360 LB a lot easier. My mechanic discovered that the only vernier throttled 231 is  the "newer" MB-engined 231's from 1987 on. I have a 1980 231. As I understand it, the old Modworks out of FL had an STC for a vernier throttle cable in their 262 upgrades.  Of course, they went out of business and the owners disappeared after a hurricane destroyed the hangar and the planes that they ran their business out of. Apparently, nobody has ever found the lost STC's for the 262 mods. 337 field approvals are nearly impossible to secure anymore as FAA attorneys have advised FSDO's that every time an individual puts his/her name to a 337, they are effectively granting an STC with all the liability that follows. So, I am facing a situation where McFarland will make a vernier throttle (owner assisted) for 1AMU but I have no legal way to install it without a 337.  The only STC that existed for early 231's to have a vernier throttle installed is lost. I guess I continue to fly my LB engined Merlin-equipped without a vernier throttle and occasionally overboost it since it is so easy to do...especially during a takeoff run when heavily loaded....unless my facts are wrong and somebody knows something I don't know...

[anthonydesmet]

Although I’m a 262 and not sure if this helps, I had to replace my cable at overhaul last year.  We got it from Lasar. I’m sure there is a 231 LB Merlin owner around here that has a vernier throttle cable. Possibly @DonMuncymight know.  I’d also call Lasar if you haven’t already, they might be able to walk you through a solution.

[231LV]

1 hour ago, anthonydesmet said:

Although I’m a 262 and not sure if this helps, I had to replace my cable at overhaul last year.  We got it from Lasar. I’m sure there is a 231 LB Merlin owner around here that has a vernier throttle cable. Possibly @DonMuncymight know.  I’d also call Lasar if you haven’t already, they might be able to walk you through a solution.

It was LASAR that said the vernier throttle cables are only for the 1987 231 models and newer but thanks for the suggestion...maybe Don will chime in...

[carusoam]

Something sounds a bit amiss…

Being able to upgrade your engine and its subsystems to a newer model likeness….

Yet not able to do the same for the controls…

There is a lot around here regarding user supplied parts… engine controls are the standard example… but, that would get you exactly what you have already… 

A good thing to do is call the engine control company that does all of the user supplied parts for us…

They are the experts, and can supply the details of what you need to do to upgrade properly….

There must be a proper way to do this…

Lets ask @M20Doc… (vernier throttle upgrade for 231, question)

Best regards,

-a-

[ArtVandelay]

When I order the throttle cable from Mcfarlane for my J, it came as a vernier without me requesting it. My original wasn’t.
Seems to me this should not require a 337, it’s a simple mod, and one that only an AP signature should be required. Mike Busch has a video on what is a simple mod vs what requires a FSDO approval.

[DanM20C]

At Airventure this past year I got a quote for a vernier throttle cable from McFarlane for my 231.  The price was around $700 I think. 

I don't think a 337 would be required.  It's just a simple mod as stated above.

McFarlane Mooney Cables

Cheers,

Dan

 

[231LV]

17 minutes ago, DanM20C said:

At Airventure this past year I got a quote for a vernier throttle cable from McFarlane for my 231.  The price was around $700 I think. 

I don't think a 337 would be required.  It's just a simple mod as stated above.

McFarlane Mooney Cables

Cheers,

Dan

 

According to my mechanic, it requires a 337 since it is a field modification and FSDO's are not granting them anymore. There is approval for non-231's (J's and earlier with the Lycoming engines) and for the MB-engined 231's built from 1987 on but there is a gap for the 79-86 231's. This is the information I have and I am hoping I am wrong and someone with the correct information can straighten me out.

[DanM20C]

8 minutes ago, 231LV said:

According to my mechanic, it requires a 337 since it is a field modification and FSDO's are not granting them anymore. There is approval for non-231's (J's and earlier with the Lycoming engines) and for the MB-engined 231's built from 1987 on but there is a gap for the 79-86 231's. This is the information I have and I am hoping I am wrong and someone with the correct information can straighten me out.

I hope you are wrong also, as I was hoping to do this in the next year. 

I'll watch this thread closely and see what it yields.

Cheers,

Dan

[Guest]

From the K model IPC.  Item 14 is the throttle cable, there are a number of numbers depending on serial number.  If the one for your sn is not available I would suggest a parts replacement to the subsequent number would be approved, just like upgrading control wheels.

Clarence

[ArtVandelay]

Might want to read this….hint: all mechanic aren’t equal.

https://www.aopa.org/news-and-media/all-news/2014/october/22/aircraft-maintenance-major-vs-minor-alterations-part-2

[LANCECASPER]

3 hours ago, 231LV said:

It was LASAR that said the vernier throttle cables are only for the 1987 231 models and newer but thanks for the suggestion...maybe Don will chime in...

1985 was the last year for the 231. The 252s started in 1986

There's enough documentation showing that a vernier cable was an  upgrade to the 231, even at the factory. I wouldn't look back.

Your 262 is an example of how the FAA was much more reasonable 30 years ago than they are today.

[231LV]

17 hours ago, M20Doc said:

From the K model IPC.  Item 14 is the throttle cable, there are a number of numbers depending on serial number.  If the one for your sn is not available I would suggest a parts replacement to the subsequent number would be approved, just like upgrading control wheels.

Clarence

OK for those who are interested, M20Doc saved the day. I sent this info to my mechanic and he confirmed my serial number is among those authorized through an FAA/ PMA cable MacFarland can make so BINGO, new cable ordered for $708.00! My mechanic now feels comfortable installing it so we are golden.

[carusoam]

Great follow-up LV!

+1 for M20Doc sharing his skills!

Best regards,

-a-

[M20F-1968]

Do you have a pop-off valve.  That would give some insurance against over-boosting.

John Breda

[231LV]

Yes it does BUT the valve doesn't pop until the engine is in the overboost zone...the engine can tolerate momentary mild overboosting but the deeper into overboost you go, the more likelihood of a head separation. Like flutter, overboost can have catastrophic consequences very quickly. The original GB engine with the fixed waste gate also had a pop off valve and still suffered a head separation in the early years according to the engine log books.

[Guest]

7 hours ago, 231LV said:

OK for those who are interested, M20Doc saved the day. I sent this info to my mechanic and he confirmed my serial number is among those authorized through an FAA/ PMA cable MacFarland can make so BINGO, new cable ordered for $708.00! My mechanic now feels comfortable installing it so we are golden.

Glad that it worked out.  Does your maintainer have the manuals for the plane?

Clarence

[231LV]

2 hours ago, M20Doc said:

Glad that it worked out.  Does your maintainer have the manuals for the plane?

Clarence

I'm sure he does