231 vs 252

[jrwilson]

On ‎6‎/‎17‎/‎2017 at 7:16 PM, gsxrpilot said:

A cowl and cowl flap redesign between the 231 and 252 leads to better cooling of the engine which improves engine life and reduces maintenance.

The intake on the 252 is improved as well.

I've got the airflow systems intercooler and GAMI injectors and run ROP in my 231.  I actually have to watch my #5 and #6 cylinders to make sure it doesn't get below 250 (Its right in front) in cooler temps and in climbs.  The hottest cylinder doesn't get above 380 in cruise in the summer with cowl flaps in trail...  So an LB 231 with intercooler can run pretty darn cool. 

[GaryP1007]

I need to get me one.  April 2018 is my target purchase date and I am itching as it gets closer.

[johncuyle]

jlunseth,
 
  My apologies for leading you astray, was not my intention.  I am sure I've seen the mod, I cannot say I've seen the STC to perform the mod.  The B&C pad mount shaft driven unit would be my choice also,  Is there any precedence for a field approval on such a mod?  I've seen the 28v version on a Bravo with the whole emergency buss isolation process, would love to have the ability to do something similar on the 231 (after I'm done with the vacuum pump of course).
 
Ron

There is precedence for a field mod for the B&C. Email them and they'll send you the info.


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[byrdflyr]

What did Mooney do to get the 230 lb increase in useful load from the 252 to the Encore?  I think the engine went from 210 to 220 HP, but that alone wouldn't justify a 230 lb UL increase. If you own a 252 (or a 262 Trophy conversion with an MB engine, 252 cowling, dual alternators, etc.), and you wanted to get the 230 lb increase in UL, could that be done through the FSDO?

 

[milotron]

16 minutes ago, byrdflyr said:

What did Mooney do to get the 230 lb increase in useful load from the 252 to the Encore?  I think the engine went from 210 to 220 HP, but that alone wouldn't justify a 230 lb UL increase. If you own a 252 (or a 262 Trophy conversion with an MB engine, 252 cowling, dual alternators, etc.), and you wanted to get the 230 lb increase in UL, could that be done through the FSDO?

 

Hi, There are upgrades to the brakes also as, going to the dual puck units. I have a 262 Trophy and looked into this also and don't believe it to be possible as the 262 upgrade is not a factory 252, or so I have been told.

[byrdflyr]

OK, answering my own question, leaves me with more questions: according to an article on the Encore in AOPA from 1997, there's this:

As it turns out, a modern-day 252 is the answer, according to Mooney. First announced last fall, the new Encore takes all that was good about the 252 and adds a decade's worth of panel and interior refinement along with a little engine tweak that boosts horsepower by 10, to 220 hp. Those extra horses don't really affect the cruise performance, however. Instead, the additional power is needed to lift the 230-pound maximum gross weight increase that comes with the Encore, a greatly needed improvement over the 252.  AND THIS

The increase in max gross weight required Mooney to run nearly a complete recertification program on the 252, according Thomas A. Bowen, Mooney's director of engineering. To handle the extra loads, the Encore uses the beefier landing gear found on the longer and heavier Ovation and Bravo. The 252 used the same landing gear as Mooney's other short-body product, the 200-hp MSE (soon to be renamed the Allegro).

So it appears that the combination of 10 more HP,  and beefier landing gear is the basis for 230 more HP, and I'm speculating that it is really more about the landing gear (and perhaps beefier brakes) than the HP.  Anyone know how much each of these variables affect the UL calculation?

[gsxrpilot]

The conversion from a 252 to an Encore requires complying to a specific Mooney Drawing. It's getting more and more difficult to get ahold of the drawing and the required parts as the years go by. But here are the requirements:

Engine -
- Change prop governor to reduce max RPM to 2600.
- Change wategate to increase max boost to 39".
- Change fuel pump to supply fuel flow required for increased boost.
- Remark engine instruments accordingly.
= increase from 210hp to 220hp and engine designation change from MB to SB.

Airframe -
- Change brakes from single caliper to dual caliper.
- This requires new brake rotors/disks.
- This requires new master cylinders. *not 100% sure on this one
- This requires new inner and middle gear doors to enclose the larger disks and calipers.
- All of the above now requires new counter weights for all control surfaces.

Logbook entry
Weight and Balance with new gross weight of 3200 lbs.

This should result in a net UL increase of +230 lbs.

[KLRDMD]

22 minutes ago, gsxrpilot said:

This should result in a net UL increase of +230 lbs.

It results in a *gross weight* increase of 230 lb. Net useful load increase is only a little over 100 lb, about 110 lb on average after you put the heavier gear, brakes, gear doors, counter weights, etc on. When I was looking for more useful load than I had with my 231, Jimmy had an Encore available so I discussed this with him and decided it wasn't worth the expense for a small net gain in UL.

[gsxrpilot]

8 minutes ago, KLRDMD said:

It results in a *gross weight* increase of 230 lb. Net useful load increase is only a little over 100 lb, about 110 lb on average after you put the heavier gear, brakes, gear doors, counter weights, etc on. When I was looking for more useful load than I had with my 231, Jimmy had an Encore available so I discussed this with him and decided it wasn't worth the expense for a small net gain in UL.

Correct, my mistake.

Gross weight goes from 2900 to 3130. But there's no change in gear. Only brakes, doors and counter weights.

[Jungle Pilot]

I am looking for the digital version (.pdf) of the  M20K-252 IPC (Illustrated Parts Catalog).  Thank you Dave. 

[gsxrpilot]

8 minutes ago, Jungle Pilot said:

I am looking for the digital version (.pdf) of the  M20K-252 IPC (Illustrated Parts Catalog).  Thank you Dave. 

You can order that from Mooney through your local MSC.

[kortopates]

It results in a *gross weight* increase of 230 lb. Net useful load increase is only a little over 100 lb, about 110 lb on average after you put the heavier gear, brakes, gear doors, counter weights, etc on. When I was looking for more useful load than I had with my 231, Jimmy had an Encore available so I discussed this with him and decided it wasn't worth the expense for a small net gain in UL.

The net gain in useful load is nearly all of the 230 lbs, double puck calipers, thicker rotors etc only weigh a couple pounds more, heavier control weights only weigh ounces more. I can’t recall exactly to the pound, but I got within just a few pounds of all of that 230 lb gain. That’s absurd to suggest the brakes weight 100 lbs! The heaviest component of all is the spindles, but the only mod is for the beefier torque plate for the brakes. So their difference in weight was negligible. It’s a very worthwhile mod and highly coveted. It brought my 252 to nearly a 1120 lb useful load!

 

 

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[KLRDMD]

27 minutes ago, kortopates said:

The net gain in useful load is nearly all of the 230 lbs, double puck calipers, thicker rotors etc only weigh a couple pounds more, heavier control weights only weigh ounces more. I can’t recall exactly to the pound, but I got within just a few pounds of all of that 230 lb gain. That’s absurd to suggest the brakes weight 100 lbs! The heaviest component of all is the spindles, but the only mod is for the beefier torque plate for the brakes. So their difference in weight was negligible. It’s a very worthwhile mod and highly coveted. It brought my 252 to nearly a 1120 lb useful load!

Simply repeating what Jimmy told me. The example he had that I was considering wasn't worth it for the small gain in useful load. I have a really sweet S35 Bonanza now with plenty of useful load so I'm fine.

[kortopates]

Simply repeating what Jimmy told me. The example he had that I was considering wasn't worth it for the small gain in useful load. I have a really sweet S35 Bonanza now with plenty of useful load so I'm fine.

I realize and understand, but that was more of a comparison between airframes with different empty weights than the added weight from the Encore conversion which is very small.


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[KLRDMD]

11 minutes ago, kortopates said:

I realize and understand, but that was more of a comparison between airframes with different empty weights than the added weight from the Encore conversion which is very small.

He was discussing this specific Encore conversion. That's the only one I ever seriously considered at the time so it is all I had to go on.

[larryb]

The factory encores have the beefier landing gear from the long bodies. Does the conversion get that?

[kortopates]

3 hours ago, larryb said:

The factory encores have the beefier landing gear from the long bodies. Does the conversion get that?

Sorry, beefier landing gear is a misnomer. The IPC shows this. WRT the gear, the difference is in the spindles/axles and brake/gear doors. And the spindles are actually identical except for a beefier torque plate for the double puck calipers to mount to. Also the the earlier Bravos came with single puck brakes, even with the higher max gross weight. Later before the Encore came out, Bravo's went to a double puck brake with a retrofit kit - later that Mooney drawing made for the Bravo was also made available for the 252 to convert to double puck brake system and used for the Encores. 

There is similar rumor to a change in the tubular cockpit frame with the 252 which made the 252 eligible for the gross weight increase but not the earlier 231 airframe - don't know if there is any truth to that one either.

Edited June 19, 2019 by kortopates

[carusoam]

From L to M... beefier landing gear was used to describe the changes, to allow the higher MGLW as the Long Bodies evolved.

Hard to tell without looking at the part numbers...

Best regards,

-a-