Encore newbie questions

[Z W]

When planning descents from cruise, I watch the required descent rate to hit my target.  It displays on my 496 by default.  Any Garmin product can be programmed to display it, I think. My 430W will do it, with alerts.  Or you can do the math the old fashioned way.

 

When it says I need 400 FPM descent to hit the airport, I start reducing my power to 20" of MP by gradually rolling the throttle out.  That way, when it hits 500 FPM, I'm slowed down enough to point the nose down and descend.  I can then do a 500 FPM descent rate, not pop anybody's eardrums, and stay out of the yellow arc.  Usually, ATC will clear me for lower right around the 500 FPM calculation mark.  If I don't get cleared by then, I ask for lower.

 

My engine stays nice and warm, and no need to pop the speed brakes, unless something goes wrong (ATC holds you higher, or you want to reduce your airspeed for turbulence).  The brakes are always there if you find yourself too fast, and make a great tool, but I find with planning I rarely need them any more.

 

Hope that helps you get it figured out.

[Awful_Charlie]

The whole shock cooling thing seems to be contentious in its own right, my view is that it takes little effort to avoid it, and if that means the cylinders last longer, then that is a good thing. As for rain creating shock cooling, unless you're planning on creating the rain by ploughing into a lake, fuggedabouit - I've gone through some horrendous showers (the ones where it hammers the aircraft, and you can't see through the screen) and only managed to get 20degF/min - have a look about 1h38 into this flight where it came down in stair rods, and you can see the bigger effect on #1 and #2 which get the brunt of the rain in a Lycoming configuration. I suppose if it gets very lumpy at the same time and you yank the throttle, then you might be able to make it cool quicker, but that is not really the fault of the rain.

 

For descent planning I find 5nm per 1000' works out pretty well, plus a bit for a hefty tailwind, minus a bit for a headwind (but if it's a headwind, I'll tend to be trying for lower earlier anyway). I sometimes get up the Garmin for a 500'/min warning, and when it goes off use 600'/min for the descent - as the ground speed tends to go up in the descent, then the available time will decrease.

 

At the BoD, just tip the nose over maintaining the MP (mine seems to need a gentle removing a bit of throttle occasionally on the way down to do this), and then start reducing to try to get to about 18" of MP in the overhead for a standard overhead join.  I open the cowl flaps when the gear goes down, or the CHTs seem to go up when the wheel based air brakes go down, I don't often use the air brakes themselves, unless ATC denies my request, or there's another operational reason.  None of it is difficult, you just need to ensure you stay ahead of the game

[Z W]

There are two different situations you will see referred to as "shock cooling" on the internet and in literature:  

 

One, the sudden cooling of the engine overstresses the metal in your cylinders and other engine parts, and the overstress causes damage and decreased engine life.  There are lots of theories on both sides of this, and little to no empirical data on either side.

 

Two, during a prolonged descent without power in very cold air, your engine will cool below it's proper operating temperature.  The concern then is that if you jam the levers forward for a go-around, your engine will not make 100% power.  Also related to this, is that without enough MP (about 15" as you state) the prop drives the engine, versus the other way around.  There is consensus from everyone that this does bad things to your cylinders and rings.

 

I've never seen any empirical evidence, myself, of type #1.  So I'm not currently much of a believer.  Nobody can ever tell me how many degrees per minute is "safe" and at what point it becomes "shock cooling," either.

 

For type #2, I have seen that if you open the cowl flaps, chop the throttle, and point the nose down, my engine will quickly go below its green operating range.  I don't think I need to be a Mooney test pilot to determine that's not the condition you want your engine in on short final.  So I avoid that.

 

So when somebody starts talking to you about "shock cooling" you might clarify what they are referring to, and ask for their sources.  

 

As a general rule, watch your engine monitor and keep the CHT's between 250 and 380 at all times (maybe as high as 400 during the occasional prolonged climb), and you'll have a happy engine.  With my 252 engine, I do not open the cowl flaps in the pattern.  I leave them closed to keep the temps up.  Cowl flaps open is part of my go-around procedure.  So, a little different than Charlie's Bravo.

[nickmatic]

Lots of great advice on here, thanks everyone. In particular you guys made me more aware to keep the engine warm should I need a go-around. I'll be taking more care in that area.

 

I'm looking into advancedpilot.com as well. Looks good.

[aaronk25]

Lots of great answers so far....smooth power transitions are important!

I think that once oil is 70-80 degrees or so rpm can be brought from 1000-1050 to 1200rpm to expedite warm up.

I don't take off tell oil is 140ish but more importantly if it's really cold out before doing the run up ill limit rpms to 1500 until CHTs get upto 250-280 or so.

That's about it I'm not much of a believer in shock cooling on decent. But using full flaps for landing normally ensures some power is kept on to keep the cylinders ready for a go around, unless it's a steep decent.

[Z W]

Nickmatic - I have noticed a more serious problem you have.  You bought a 252/Encore and I don't see any pictures of it in your gallery.  Pics or it didn't happen, my friend.

 

Welcome to the Mooney family.

[nickmatic]

Nickmatic - I have noticed a more serious problem you have.  You bought a 252/Encore and I don't see any pictures of it in your gallery.  Pics or it didn't happen, my friend.

 

Welcome to the Mooney family.

Good catch! Serious airworthiness issue. Resolved And thanks.

[carusoam]

On the topic of using engine drag to slow down....

No down-shifting into the corners???

Best regards,

-a-

[Nemesis]

nickmatic et all,

 

I have only been slam dunked by ATC a couple of times but reducing to 25" and nosing over for a high rate of decent has never resulted in excessive speed in my K model. I will be at the top of the green for sure. If there were some bumps involved then I would have to coordinate a more appropriate rate with ATC. For me, a slam dunk has never been the norm but it is something that has to be dealt with from time to time.

 

I have been to Advance Pilot and believe the shock cooling thing is bunk, OWT, etc, but I also will not subject my engine to large rapid power changes beginning the decent. ie. 30" reducing to 15" is not a good idea and not my practice.

 

Under normal circumstances in relatively calm conditions, I have a different take on the whole thing. Part of my decent planning depends on an accurate measure of time remaining on the flight plan. In other words, a GPS is required. Installed or hand held does not make any difference. My preferred decent rate is 500 fpm. That is slow enough for passengers and for regaining some of the waste of fuel from the climb and also normally fast enough for ATC. Cowl flaps are always closed. My home field is at sea level so my target altitude for the decent is 1000 msl. I want to be at 1000 msl as I close in on the field (nothing new here). If I am cruising at 17000, then I want to descend 16000 feet. At 500 fpm it will take 32 mins to get down to pattern altitude. I will add 8 to 10 mins to that figure so that with about 40 mins remaining on my flight plan, I begin a 500 fpm decent. I reduce MP by 2" only and as the MP rises back to 30" (cruise power setting) in the decent, reduce by 2" again. In other words, I make a relatively full cruise power decent. I have an LB engine with Merlin so my MP is not well regulated while climbing or descending. I am not sure, but I think your MB engine handles the MP better during climbs and descents.

 

The 8 to 10 mins that I added to decent time is so that I have time to slow down, decide on entering the pattern or a straight in approach, and to configure for the approach and landing. Also, descending at a high power setting means that I am again pretty high in the green arc for IAS so I am covering more ground. It is not unusual to see 170 to 175 kias during decent so also remember best practices if there is some turbulence. At about 1500 msl (or agl) I begin to round out the bottom of the decent and reduce to 25". Consistently that is about 8 or 10 NM from the field (even though my decent was based on time). Slow down a bit, make a radio call, check on my now very slow decent rate and altitude, and I can reduce to 20". By this time I am at 1200 agl and 5 NM. I can drop the gear and begin a 5 mile final or continue onward into the pattern. Reduce power to 18" and with the gear down and approach flaps, that gives me a nice 90 to 95 kias on long final (20" if in the clag and close to 105 kias). Add full flaps the last 2 miles and that produces a comfortable 80 kias for short final.

 

In terms of power management, heat in the engine, loading of the rings, etc., going from 30" directly to 25" does not bother me at all. Going from 25" to 18" happens over the course of about 2 to 3 minutes, so for me that is plenty gradual and not abrupt. I am never below 18" until I reduce power on very short final so that I can be at 75 kias over the fence and to flare and touch down.

 

I do not have speed brakes and have never really needed them. They would however be a nice tool to have in the case of an ATC slam dunk.

 

After writing all of that out it seems like a lot of steps to take but it really is not. The key is choosing the correct number of minutes remaining on the flight plan. Add more time in addition to decent minutes for long descents, add less time for more shallow descents. It is the same as programing a vertical decent profile in a GPS I just prefer to do it in my head.

 

As the many posts have shown, there are just as many methods as there are pilots. The best advice from all of these posts is to get with that Mooney specific instructor until such time as you know what your machine can do all the while keeping all of the instruments in the green. By that time you will likely have your own best practices and methods for accomplishing a given task.

[fluffysheap]

First step to a happy engine in descent is not to get it too hot in the first place.  LOP below FL200 for me usually means CHTs around 330.  Pull off 1 or 2 inches before descending and it will drop to around 310.  So, at that point, it's so cool that it isn't going to get much colder in the descent.  If my cruising altitude happens to be above FL200, I usually ask for a descent down to 170-190 if conditions permit.

 

Descent profile for me is to reduce to 25" and descend at about 500 FPM.  The engine will gradually cool into the mid-200s.  At that point, I reduce to minimum prop speed, and about 17-20" of MP.  Minimum prop speed will tend to increase the manifold and cylinder pressure for a given power level, keeping things (relatively) warm.  At this point I also enrich slightly, to peak instead of LOP.  The engine will get a little cold at this point, maybe low 200s, but never seems to get much colder than that no matter how long the descent is.  If the weather is warm, it doesn't even get quite that cold, maybe 230.  Once I reach my target altitude, I set about 2200 RPM and about 22-25" MP.  This allows the engine to warm back up under gentle power application.  It's usually around 230-250 when it's actually time to land, which is quite cool but still warm enough in case I have to go around.  Finally, I set full rich mixture as part of the GUMPS check in the pattern, or at the FAF if IFR.

 

There are two descent procedures in the POH, either to descend "clean" at the top of the green arc (or even in the yellow) if air is smooth, or "dirty" at low speed if air is rough.  Both will allow you to come down 1000FPM or faster, but of course the dirty procedure is a much steeper path.  I don't have speed brakes and don't see the need.  I use the high-speed descent profile 90% of the time.  The low-speed profile is plenty steep enough, and I can't see why you'd need speed brakes on top of that.

[mike_elliott]

You should advise us in what region you live and then we can maybe point you to a CFI that will have expertise in your make/model airframe and engine.

 

Think really hard about this.  Would you want to spend 10 minutes going from 30" to 20" of manifold pressure to set up an approach? 5 minutes?

 

That's quite a long time...

 

I don't hold myself out for giving initial training in certain airframes, though I might give a flight review or IPC.  Why?  Because that person needs to learn the correct habits for his/her new plane from someone with expertise in that airframe.  Your initial training should be based on facts, not rules of thumb.  Why?  Because you need to get the most out of YOUR plane!

 

Parker makes an excellent point. Send him an airplane ticket, spend a few hours with him, and really learn how to fly an Encore the way it should be flown.

[fantom]

Parker makes an excellent point. Send him an airplane ticket, spend a few hours with him, and really learn how to fly an Encore the way it should be flown.

+1

.....and Parker, like Mike, knows how to find really inexpensive airline tickets.

[Bill737NG]

Who does the Encore conversion, and what is the cost (converting a 252?)

Also, how much of the 230 pounds max gross increase ends up as useful load increase? Thanks.

[Parker_Woodruff]

Who does the Encore conversion, and what is the cost (converting a 252?)

Also, how much of the 230 pounds max gross increase ends up as useful load increase? Thanks.

Call a Mooney Service Center to have them quote you the parts and labor (Mooney might have to make some parts first). Almost all of it ends up being extra useful load.

[Jungle Pilot]

Hello Encore / 252 conversion owners. I am in the process of an engine overhaul of my 252 MB engine and upgrading to an SB. How did you guys upgrade your brakes to get the dual piston calipers. Someone has told me I need new gear doors too?

Dave K

[gsxrpilot]

57 minutes ago, Jungle Pilot said:

Hello Encore / 252 conversion owners. I am in the process of an engine overhaul of my 252 MB engine and upgrading to an SB. How did you guys upgrade your brakes to get the dual piston calipers. Someone has told me I need new gear doors too?

Dave K

There's a lot of research to do on this topic. @kortopates and @Parker_Woodruff are good resources as they've gone through this already. I can help you as well as I'm in the middle of it.

But the short answer is you have to get a hold of a Mooney drawing that details the part numbers for all the pieces you need. As you noted, you'll have to upgrade the brakes to dual piston calipers. That opens a whole can of worms that includes new disks, master cylinder, and gear doors to fit around the new calipers. You'll also need new/larger counter weights for the control surfaces. The gear doors and counter weights can be bought from Mooney... when they have them in stock. The brake parts can probably be source from Aircraft Spruce. 

The drawing is very difficult to find, and I don't have one myself. Converting a 252 to an Encore is certainly a worthy effort and will increase the value of the plane. But it's gonna take a lot of research on your part to make it happen. 

[kortopates]

5 hours ago, Jungle Pilot said:

Hello Encore / 252 conversion owners. I am in the process of an engine overhaul of my 252 MB engine and upgrading to an SB. How did you guys upgrade your brakes to get the dual piston calipers. Someone has told me I need new gear doors too?

Dave K

Hi Dave,

That's great! But you're kinda of attacking it backwards in that there is no existing approval for installing the -SB engine in the 252 airframe until after you have accomplished all the airframe mods per the drawing which includes more than double puck brakes, it also includes new (larger) master cylinders, some new gear doors to fit over the larger brakes and heavier control weights on all the control surfaces. I did mine in two stages by doing the airframe first, since that is an approved mod by itself.  But the engine installation is only approved per the drawing after the airframe mod drawing has been accomplished. I expect any MSC can order the drawings for you through the factory and accomplish all the mods, they're not expansive but they provide the approval to make mods.

Edited May 26, 2019 by kortopates

[Parker_Woodruff]

On 5/26/2019 at 10:23 AM, gsxrpilot said:

There's a lot of research to do on this topic. @kortopates and @Parker_Woodruff are good resources as they've gone through this already. I can help you as well as I'm in the middle of it.

But the short answer is you have to get a hold of a Mooney drawing that details the part numbers for all the pieces you need. As you noted, you'll have to upgrade the brakes to dual piston calipers. That opens a whole can of worms that includes new disks, master cylinder, and gear doors to fit around the new calipers. You'll also need new/larger counter weights for the control surfaces. The gear doors and counter weights can be bought from Mooney... when they have them in stock. The brake parts can probably be source from Aircraft Spruce. 

The drawing is very difficult to find, and I don't have one myself. Converting a 252 to an Encore is certainly a worthy effort and will increase the value of the plane. But it's gonna take a lot of research on your part to make it happen. 

This.  And do it all at once or do the airframe first then the engine.