Looking at a M20K 231

[Goldonomic]

On 1/20/2021 at 8:14 AM, RJBrown said:

People like this one do a real service to buyers of 231s. Their uninformed posturing scares people off and pushes down prices.

A J may be the best N/A airplane ever built but it is a downright dog compared to a 231.

I’ve owned both. Before I bought a 231 I flew N9136N a near new 1992 MSE. First flew her in July of 1993 I loved flying that plane. I rented it about 20 times over the next year.

After flying high time Cessnas to learn how to fly that 18 month old MSE was the greatest airplane I’d ever flown. Until I flew a 231. I lived in Denver with MEAs of 16600’ just 15 miles to my west. The difference in safety and dispatch reliability is night and day.

by the way that 231 in Dothan is the most expensive 231 I’ve ever seen. Engine beyond TBO, original panel with a bad KNS80, paint and interior. No wastegate or intercooler. If money is no object and you want a blank canvas you could dump another hundred grand into it tomorrow.

GET a 231 !!! it is the BEST Mooney manufactured ever.

[Mike A]

Here is my flight down to FL yesterday. Yes I know #3 is a little higher than I’d like too, but I got it down below 180 shortly after by leaning my FF to 10.3 gph and only lost 2 ktas. At 2550 rpm. Cowl flaps closed. 
 

 

[whiskytango]

4 hours ago, jlunseth said:

You should get a copy of the Turboplus STC and give that to him. It has specific instructions for modifying the - SID 97-3 (something). The "something" part is that they continually update the SID, so there is a letter at the end and the last time I looked I think it was G. Here is what you will find. The STC requires making adjustments to the manifold pressure at which fuel flow is set depending on ambient pressure and temp. Generally, the fuel setting is made at a number somewhere around 37", rather than the 40" in the POH or the 36" we have all been told. It has always seemed to me that there is an abrupt rise in the fuel flow when the engine is at full power, meaning that every inch or even decimal place will marketly affect the flow. As you probably know, it is not easy to set the TSIO360LB to the tenth of an inch. The fuel flow settings in the SID are made from that base.

I have come to the conclusion that it is wrong to think the engine should not be operated at more than 36", depending on flight regime. Here's why. On the ground, while a maintenance run up is being conducted, the aircraft is not moving and therefore the cooling airflow over the intercooler is not what it would be in flight. Nearly the same thing happens on takeoff, until the aircraft picks up some speed. Moreover, the Turboplus STC uses a higher number, as I said, around 37 or even higher, for the max fuel flow setting. That said, I still don't like operating the engine for a prolonged period, such as in a climb to the flight levels, at a number over 36", but bear in mind that if you do as I do, you are likely not operating at full power. Certainly you are not operating the engine where the STC says you should be for full fuel flow, so you are going to get something in the 22 range from my experience, not 24 gph. That is if the mechanic set the fuel up exactly according to the STC. "Do not operate over 36" " is something we have all read somewhere, but it is not in the POH

I have on occasion gotten my mechanic to set the fuel a little higher, 25GPH. I then need to manage the throttle a little more to keep the fuel flow at 24" which is the POH max. As you know, the throttle and fuel flow are interlinked, so if you firewall the fuel flow and then put in 36" MP, the fuel flow automatically rises. If you put in 37" it rises higher still.

The other issue is the low idle setting. I think the mechanics set the max fuel first, and then they screw the idle adjustment down to where they want it. But the two seem to be interconnected, so that lowers the max fuel even if they set it right to begin with. They need to do it the other way around, set the low fuel first and then tweak the max flow to whatever setting is desired. That results in a slightly higher fuel flow at idle, but it is not idle fuel flow that we worry about in the 231, it is the full power climb to altitude.

I wish I knew the magic bullet to get it set correctly every time.

This is all great information, and makes sense.  I will have it in hand, along with the Turboplus STC you referenced, the next time I have my A&P adjust fuel flow.  

Maybe the MB engine designation stands for the "Magic Bullet" we LB owners have been seeking!