GaryP1007

231 vs 252

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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. 

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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.


Sent from my iPhone using Tapatalk

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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?

 

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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.

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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?

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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.

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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.

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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.

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