M20K 231 - family plane?

[M20F]

4 minutes ago, MikeOH said:

I'm used to 8.5-9 gph....any idea what a pair of fire-breathing IO-720s burn per hour?

Where is Clarence when you need him.  This is what owner shared. 
 
At altitudes below 8000 this is what I’ve observed.
Cruise at 36 GPH and 220 MPH
Cruise at 34 GPH and 210 MPH
Cruise at 30 GPH and 195 MPH

 

[MikeOH]

1 minute ago, M20F said:

Where is Clarence when you need him.  This is what owner shared. 
 
At altitudes below 8000 this is what I’ve observed.
Cruise at 36 GPH and 220 MPH
Cruise at 34 GPH and 210 MPH
Cruise at 30 GPH and 195 MPH

 

Ugly, but I was betting over 40 gph!

Still, over three times the fuel burn for only 30 mph speed increase doesn't really make me envious. YMMV

[M20F]

11 minutes ago, MikeOH said:

Ugly, but I was betting over 40 gph!

Still, over three times the fuel burn for only 30 mph speed increase doesn't really make me envious. YMMV

30 GPH to do 170kts for 7hrs with 6 people, baggage, and a toilet ain’t bad.  I got a thing for Tbones but not conducive to my mission

[m20flyer]

20 minutes ago, MikeOH said:

I'm used to 8.5-9 gph....any idea what a pair of fire-breathing IO-720s burn per hour?

Or GO-480s.

That "G" is something I want nothing to do with.  Geared engines are great when they're happy, but I don't want to overhaul one.

I called on the OH cost of a GSTIO-520 a little while ago.  $100K, $120k if you needed new parts.  No support for the earlier variants.  That's per engine, by the way.

[Shadrach]

18 minutes ago, MikeOH said:

I'm used to 8.5-9 gph....any idea what a pair of fire-breathing IO-720s burn per hour?

Twin Bonanzas have been equipped with a verity of geared, Lycoming sixes but never a 720 to my knowledge. The GO engines magnificent sounds…

 

 

[MikeOH]

3 minutes ago, Shadrach said:

Twin Bonanzas have been equipped with a verity of geared, Lycoming sixes but never a 720 to my knowledge. The GO engines magnificent sounds…

 

 

I was referring to M20F's post regarding the Excalibur Tbone on Beechtalk: https://www.beechtalk.com/forums/viewtopic.php?f=43&t=231535

Pretty certain it's sporting twin 720s

[M20F]

6 minutes ago, Shadrach said:

Twin Bonanzas have been equipped with a verity of geared, Lycoming sixes but never a 720 to my knowledge. The GO engines magnificent sounds…

 

 

Excalibur conversion is 720’s it is dope. 

[Shadrach]

16 hours ago, MikeOH said:

I was referring to M20F's post regarding the Excalibur Tbone on Beechtalk: https://www.beechtalk.com/forums/viewtopic.php?f=43&t=231535

Pretty certain it's sporting twin 720s

Indeed it is. They’re probably cheaper to keep than the geared sixes.

[MikeOH]

1 minute ago, Shadrach said:

Indeed it is. They’re probably cheaper to keep than tge geared sixes.

Trust me when I tell you that's something I'll never find out

[jlunseth]

On 8/15/2024 at 10:41 PM, m20flyer said:

 

• The -LB is more desirable, and I'd expect the -GBs to have been worked out by now.  If I find one with a -GB, should that be considered a dealbreaker?
• The earlier models and even some of the Js have SB208 for corrosion in the roll cage on the pilot side.  Are the 231s subject to this SB?  If so, how common is this problem on 231s.
• Takeoff distances and climb rates will work for the high-DA operations I expect to see (~7,500' @ 30*C near MGTOW; cruise into the teens but rarely into the FLs).
• It'll cruise 160-170 at 12gph or I can loaf around in on local flights at around 6gph.
• XC will be about 20% of the use, virtually all to high DA airports.  Local flights and currency will be about 80%.
• I can get insurance.
• I will rarely have to top the tanks for the flights that we intend to do.

What I need:

• 1,000lb useful
• Four usable seats
• Enough baggage space for light packers

Questions:

• How is the back seat legroom for people >6'?
• Are there any major gotchas for the 231 with an -LB engine?
• What are owners seeing as an all-in cost/hr for a 231?

Finally, if there is anyone in the Phoenix area willing to go for a demo flight, I'll buy the gas!

I have about 2,000 hours in my 231, am working on my second engine, and have flown quite a few trips into and over the western mountains. I also fly for Angel Flight often so am used to managing loads that might seem excessive for the plane, including, once, a wheelchair. I will go through your questions here and give you my perspective for what it is worth.

The LB is more desirable. The GB was known for high engine temps. That can be a problem even for the LB under the wrong conditions. As a practical matter, if you want engine life, the GB would limit you to the mid teens. I would want the Merlyn and the intercooler, both of which I have. The absence of the Merlyn limits you to a Critical Altitude of around 15k, where the Merlyn lets you fly well into the flight levels. Without the intercooler, the Compressor Discharge Temp redline is 280 and as a practical matter you will see that in the summer at somewhere between 15 and 17k in the GB, but if you have the LB and intercooler the Induction Air Temp will always be under the 280 limit. The GB engine will also run generally hotter.

I don’t know if the 231 is subject to that SB for roll cage corrosion, but I can tell you what to look out for. There was an insulation used back in the day that was textured like wool. It would be cut to fit between the cage bars and the edges would rest on the cage bars. That insulation would absorb moisture and the constant contact with the cage bars would cause corrosion. During a pre-buy it would be worth it to have the side panels come off and inspect for that type of insulation and for corrosion.

With the turbo I have not encountered any high DA airport that the aircraft cannot handle easily, including Leadville in the summer. Most western airports have longer runways than what we generally have here in the Midwest. In practical fact, runout is the only thing that changes, and the longer runways take care of that. You do need to stay aware of climb rates though. Many of the western airports have departures where there is a VOR north or south of the airport. You fly to the VOR and if need be you can circle the VOR to climb to cross the rocks. It might seem in theory that you could climb on a direct course over the rocks, but if you try that on the wrong day with strong western winds aloft you will be at the rocks faster than you anticipated. Having tried it the wrong way a couple of times early on, I now use the departures every time.

You don’t ever want to fly at a cruise speed with a 12 in it for fuel flow. That may be what the POH says, but it is the dead wrong place to operate the engine. You have two cruise choices, Lean of Peak or Rich of Peak. Either way you want to be far enough away from peak EGT to be easy on the engine. I fly regularly at 11.1 GPH/2450 RPMs/34” MP, that’s LOP and will give you great speeds up to somewhere around 12-16k in the summer. If you try to go higher you will find that the TIT becomes unmanageable. To fly LOP however, the engine must be set up to do it and you may need GAMInjectors. The other way is ROP, which would be around 29.7 MP/2450RPMs/13.3-14.5 GPH. ROP or LOP you want to keep the CHTs at or under 380 as much as possible. When you are flying ROP, if the temps start creeping up, you just add more fuel to lower them. You need to be at least 125 degrees rich of peak EGT. You can fly ROP anytime you want to, whether your engine will fly LOP or not, and ROP is particularly useful when you want to go over the 12-16k area where TIT becomes a challenge if you are LOP. Either way, you will see 160 at around 10-12k and 170 in the mid to higher teens.

If you fly locally you can leave out fuel to create more payload. I do this regularly for Angel Flights. However, I can’t remember ever having flown with less than 50 gallons to start a flight (max in the normal tanks is 75.6). I have CiES senders and a JPI930, so my fuel readout is about as accurate as you can get. Even so, I don’t consider it good enough to fly a tank under 10 gallons and I never start with less than 50. If you are going to fly a trip where fuel is an issue you really need to supervise the fueling or do it yourself. The plane has anti-siphon flappers in the neck and it is pretty easy for a line kid to be fooled into thinking that the tank is full when there is fuel on top of the flapper but a big hole underneath.

As others have said, it is a reach to expect 1,000 lbs., although there are some 231’s with that UL, Mine is 980. I have been able to manage some pretty big loads by leaving out fuel, including carrying a 295 pound passenger, his wife and 50 lbs of baggage. For Angel Flights, which are generally not over 2 hours, I can fly with 50 gallons, myself (200 these days), and about 450 lbs. The leg room is not great in back, but if you put a smaller passenger in the copilot seat and roll the seat forward, the legroom in the seat behind is not bad. I have managed a collapsible wheelchair plus two passengers and baggage. I have also flown several hundred pounds of medical cargo. Unfortunately, people are getting bigger these days and the 450 lb loads are pretty common.

I wouldn’t say there are “gotchas” for the TSIO360LB, it is a pretty nice engine. There are weaknesses. You are limited to one 12V battery and one alternator, and the alternator is direct drive. The clutch in the drive is a weakness and if that goes, the house battery does not last long. If you are going to fly anywhere near IMC conditions over the mountains you need much redundancy for your AI. I have dual redundant GI275’s plus one standard AI operated by the vacuum pump so if I lose all electrical I still have an AI. If you are over the top and over mountains you won’t necessarily find a place to land for awhile. I have had the pleasure of losing the alternator and flying with the Master off (completely dark panel). You want to convert all the lights to LED if they are not already, the old incandescent lights are way too much load on the 231s electrical system. The engine can run hotter than later models, but I have found that with proper fuel management (staying out of the 12s) it is very durable. I flew my first engine to nearly 2400 hours, which is 600 over TBO.

[m20flyer]

Great writeup.  Thank you.

[Falcon Man]

This is a very informative summary. I took my LB engine 700 hrs past TBO with one top OH of cylinders. The engine shop said the bottom had just one "scuff" on a bearing, otherwise it was in good shape. (I elected for OH to new limits).

 

My 1979 231 and 1984 262 both had the old insulation and there was moisture @ the fire wall insulation also. Removing the firewall panel was really labor intensive. 

[jlunseth]

16 hours ago, Falcon Man said:

This is a very informative summary. I took my LB engine 700 hrs past TBO with one top OH of cylinders. The engine shop said the bottom had just one "scuff" on a bearing, otherwise it was in good shape. (I elected for OH to new limits).

 

My 1979 231 and 1984 262 both had the old insulation and there was moisture @ the fire wall insulation also. Removing the firewall panel was really labor intensive. 

That is excellent. The engine had such a bad reputation for running hot that I never expected to get the kind of longevity I ultimately saw, as did you. The problem, it turns out, was us - pilots - running the thing the wrong way.

[Falcon Man]

I followed my Mooney IA's and Savvy's advice on operating parameters: full throttle/MP/full rich in climb, 2200 rpm/65% HP in cruise, keeping TIT ~1550 and CHT's ~ 350F, usually ~ 25 F LOP. Fortunately my stock fuel injectors had a GAMI spread of 0.3 gph and we adjusted the cylinder baffles to keep the # 3 cylinder CHT's cooler than the stock setup.

I am using the same operating parameters in my 252, so I am planning on the similar results.

[jlunseth]

3 hours ago, Falcon Man said:

I followed my Mooney IA's and Savvy's advice on operating parameters: full throttle/MP/full rich in climb, 2200 rpm/65% HP in cruise, keeping TIT ~1550 and CHT's ~ 350F, usually ~ 25 F LOP. Fortunately my stock fuel injectors had a GAMI spread of 0.3 gph and we adjusted the cylinder baffles to keep the # 3 cylinder CHT's cooler than the stock setup.

I am using the same operating parameters in my 252, so I am planning on the similar results.

That is a perfectly acceptable way to operate the aircraft. The only thing I will say, is that it is premised on GAMI's statement (entirely true) that you can't hurt the engine if you operate at 65% HP or less, regardless of where you set the fuel (ROP, LOP or at peak). So your really aren't taking full advantage of the potential of LOP ops, you are just reducing power to a place where it does not matter how far LOP you are operating, or if you are even LOP. When I went to the GAMI seminar and first began to experiment with LOP fuel settings, it seemed to me that wastes the potential of the turbo. LOP is an air/fuel ratio. There are two ways you can affect that ratio. One is by leaving the MP static and reducing the fuel flow, and that is the only real option open to pilots of NA aircraft, because the MP is capped at whatever ambient pressure is, which will be low at anything other than sea level. The GAMI guys were/are fond of LOPWOTSOP, which means to just firewall the throttle on an NA and then manage HP with the fuel flow. You can't do that in the 360 because you will overboost. The other way is to add air, which you can do with the turbo. When I experimented, I found that I could take the MP as high as 34" and that allowed me to use a somewhat higher fuel flow and still stay safely lean of peak.  11.1 GPH worked out great. If you run it through the HP formula for LOP operations on the 360LB, that works out to 71.1% HP and the TIT would be right at or under 1600. I use 1600 as my limit, and if the TIT starts to go much over that I either adjust the fuel flow up just a little (i.e. 11.3-.7) or I reduce the MP, and if neither works it is time to fly ROP. As I said above, that usually happens around 12-16k depending on day temps. I worried at first that I was overworking the turbo, and at 1,000 hours on it (a rebuild in about 2010) I started to have my A&P borescope it. There were no problems and it was still going strong at some 12 or 1,300 hours from rebuild when I replaced the engine. The 71.1% results in really nice speeds and its hard to argue with 11.1 GPH. 

[Fly Boomer]

6 minutes ago, jlunseth said:

I worried at first that I was overworking the turbo, and at 1,000 hours on it (a rebuild in about 2010) I started to have my A&P borescope it.

How is this done?

[Falcon Man]

Thanks for the suggestions. I will try out those settings once I get my airplane back from the avionics shop. It has been hostage for 26 months! I have friends who are close to 2 years waiting for parts an engine or for factory OH. It's a sad state of affairs.

[DanM20C]

36 minutes ago, jlunseth said:

I use 1600 as my limit, and if the TIT starts to go much over that I either adjust the fuel flow up just a little (i.e. 11.3-.7) or I reduce the MP

Here you stated you add fuel flow to reduce the TIT? When lop it should be opposite.  Add MP or reduce FF to lower TIT. 

I operate my 231 very similar to you but I set my arbitrary tit limit at 1550.  I usually fly at 34", 2300rpm, and 9.5-10gph.  Typically that will yield a TIT in the 1515-1525 range.  The engine seems to love being flown this way.  @jlunseth proved this by the longevity he got with his, while pushing a little harder.  

Cheers,

Dan

 

[1980Mooney]

37 minutes ago, Falcon Man said:

Thanks for the suggestions. I will try out those settings once I get my airplane back from the avionics shop. It has been hostage for 26 months! I have friends who are close to 2 years waiting for parts an engine or for factory OH. It's a sad state of affairs.

You mention an overhaul above. How long has it been “hostage” since the O/H engine last started/got it warmed it up to operating temp/flown ?…surely not the entire 26 months. Or will this be your break-in flight?

Edited August 21 by 1980Mooney

[jlunseth]

2 hours ago, DanM20C said:

Here you stated you add fuel flow to reduce the TIT? When lop it should be opposite.  Add MP or reduce FF to lower TIT. 

I operate my 231 very similar to you but I set my arbitrary tit limit at 1550.  I usually fly at 34", 2300rpm, and 9.5-10gph.  Typically that will yield a TIT in the 1515-1525 range.  The engine seems to love being flown this way.  @jlunseth proved this by the longevity he got with his, while pushing a little harder.  

Cheers,

Dan

 

Yes, I am talking about a tiny addition. A very few tenths sometimes corrects and sometimes it doesn't. The more dependable correction is to reduce a little.  

[Falcon Man]

My OH engine in the 252 had ~ 100 hrs since last flown. It's been "pickled" according to the IA. It will have a "pre-oil procedure" before being run. Borescope of cylinders looks fine. We will see!

[Pinecone]

On 8/21/2024 at 12:59 PM, jlunseth said:

I use 1600 as my limit, and if the TIT starts to go much over that I either adjust the fuel flow up just a little (i.e. 11.3-.7) or I reduce the MP, and if neither works it is time to fly ROP. 

That is backwards.  If you are LOP, adding fuel flow will INCREASE temps.  If you are lean of peak, adding fuel moves you closer to peak.

Same with air (MP).  If LOP, you ADD MP to run cooler.