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Slowing the E down


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The way I was trained (rental checkout in an M20B), way way out you start pulling the throttle back, an inch of manifold pressure per minute (to avoid shock cooling), while keeping the same altitude (increasing pitch as necessary), to get the Mooney slowed down for arriving in the terminal environment. It works, but it's a slow and cumbersome procedure and, especially around here, where you might be at 6500' and then chop-and-drop for an airfield (e.g., IFR into KIZA, surrounded by mountains; gotta get from 6,000' to 1,120' in 21 miles), it can be ... awkward.

Then I read this article: http://www.mooneyland.com/how-to-land-a-mooney-properly/

The other day, after getting new tires1 spooned on my M20E, I did a quick cobweb-shaker flight SMO to CMA and back, and tried this technique: “When I need to slow down, I will reduce my manifold pressure down to around 17″ initially, and then reduce my RPM to around 1900. When reducing the RPM, the manifold pressure will begin to climb as we have discussed, and when equalized, you will see something like 19-19.5 squared.”

Bonus: I never spend any time (other than “passing through”) in the placarded tach range; when I used to leave the prop fully forward and manage approaches with just the throttle, I'd glance up and see “bad” RPMs and manage that, but that often left me doing gymnastics as I rapidly adjusted other inputs to get back into a stabilized approach - less than ideal.

Using that technique, I drop from ~160mph IAS cruise to spitting range of VLE (120mph IAS) in a minute or so.

Somehow, seems too good to be true; too easy, you know...?

 

 

1 Goodyear Flight Special IIs for all three, 'cause that's what Bill's had in stock (also what I would have gotten anyway, from AircraftSpruce). The mains were Condors and wore out over 50 hours (though part of that was my "still getting used to my new plane and whaaaa? No flaps?!" landing(s)). The nose was already a FSII with a bad tube or valve; whatever the cause, it sat flat for >1 week and I'm not willing to chance it, not when peace of mind is $80 for new rubber.

Edited by chrixxer
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5" reduction in MAP gives you about 500fpm constant speed decent.  After that, slow reduction in power to pattern speed while holding 500fpm.  Slow increase in rpm....prop in, low pitch, increases drag.  Pulling the prop tends to go course pitch and should decrease drag. In fact, with engine out and engine rotating, you can extend the glide by pulling the prop.  Gotta say, I did not read the article and not sure I understand the technique you described.

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I generally push for 500 fpm and trim, periodically reducing throttle to keep cruise MP and enrichening to maintain cruise EGT. I level off 3-5 nm from the field and reduce throttle, holding altitude to start slowing; for additional braking, ease the middle lever forward. Once I'm below 125 mph, I lower Takeoff flaps and enter the pattern (OK, sometimes I lower them as I enter the pattern  :rolleyes: ), dropping gear and beginning descent abeam my point of intended landing.

Slowing was difficult as a new owner (I bought half of the Mooney with 62 hours in my logbook), but it becomes routine. Now after ten years, I have to think to remember just what I do . . . But it still isn't possible to slow appreciably while descending, the Mooney will go down or slow down, but not both. 

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I don't know I just start a 300-500 fpm decent far enough out (GS/distance to go) and just keep the MP at what ever it was when I started my decent. Usually about 19-20 inches ( I cruise near 10K all the time). Seems to work out for me. I don't normally see the yellow arc on decent too much because I don't like the rough ride out here in the west in the summer and I;m not in that much of a hurry. 

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I set the portable GPS for vertical guidance, 400fpm, pitched the nose down to match the vertical guide... the MP was as much as was available (often flying at 12,500')

Chose the 400fpm experimentally.  Keeps The AS below redline...

as you get lower, dial out the MP as the 1" per thousand feet increases...

make adjustments for rough air and yellow range on the ASI.

Selected three miles out for level flight to finish the slow down process.... a setting in the portable gps...

Fuzzy memories of flying my M20C....

My magenta line was black LCD... :)

PP thoughts only, not anywhere close to being a CFI...

Best regards,

-a-

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In an older Mooney. Just plan your descent, from cruising altitude every 1000' you need to loose, plan 5 miles. so from 12k to 1k = 11 x 5 = 55 miles out pitch over to top of green (150mph) this will give you roughly 500-600 fpm, slowly reduce your power( 1" per 1k is an old big cont thingy but gets the mp moving backwards not forward in the decent) control egt with mixture all the way down. Plan to level off a few miles from your airport pattern or FAF, at 14-15 inches and you will slow to gear speed
Now this isn't always perfect, do to that pesky ground speed thingy, but it's simple math.
Remember the days without GPS! How did we ever descend properly.


Sent from my iPad using Tapatalk

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To what's been already suggested I would add that you paid for the energy that it took to climb to your cruise altitude and you want to redeem that energy by lowering the nose and going really fast. Unless the bumps are moderate I generally will trim to near red line IAS.  At that speed descent is assured but if the vertical speed is not adequate I start pulling back the throttle to maintain the descent rate I need to get to pattern altitude a few miles from the airport. When I get to about 1000 AGL I trim to level flight with the MAP below 18" and the speed quickly bleeds off to Vle. 

I am based on a field where approaching from the west on an instrument flight keeps me at 8000' AGL until about 15 nm from the field. If I can't cancel I may have to swing wide but I would still prefer coming in fast to slowing down far from the field.

If your E model is like my '66 the yellow arc starts at 130 kias (150 mias). I don't fly in the yellow in actual moderate or severe turbulence but otherwise I like to live there.   

 

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18 hours ago, Shiny moose said:

In an older Mooney. Just plan your descent, from cruising altitude every 1000' you need to loose, plan 5 miles. so from 12k to 1k = 11 x 5 = 55 miles out pitch over to top of green (150mph) this will give you roughly 500-600 fpm, slowly reduce your power( 1" per 1k is an old big cont thingy but gets the mp moving backwards not forward in the decent) control egt with mixture all the way down. Plan to level off a few miles from your airport pattern or FAF, at 14-15 inches and you will slow to gear speed
Now this isn't always perfect, do to that pesky ground speed thingy, but it's simple math.

Yeah, that doesn't really work in mountainous terrain. Like in my example, flying the instrument approach into IZA. You've got about 5,000' to lose and 16.3 miles to do it in (not the 25 your method would require). If I started descending 500fpm 25 miles out at cruise speed, that's called CFIT. And on instrument approaches (at least precision approaches) there's no such thing as "plan to level off a few miles from your airport pattern or FAF." For instance, the SMO LPV brings you down to DA at 270' AGL and about 500' from the end of the runway.

I'm asking specifically about the method described in the article (bringing manifold pressure down then governing the prop at a lower RPM). Seems to work and definitely keeps the prop from spending any time in the placarded harmonic danger zone, and allows for much more stabilized and comfortable instrument approaches (you can get established on the glideslope without gobbling up ground at 145+ knots ground speed, and you don't have excess speed to bleed off after the FAF).

It seems very controllable, very effective, works well in my (limited) experience (used it again today coming into AVQ), but no one (as anecdotally confirmed by this thread) seems to be using it. Which raises red, or at least yellow, flags: Why not?

Edited by chrixxer
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There are a lot of non-precision approaches that require a steep descent due to terrain. What I always did for the NDB 3 into MRN years ago was to slow to 90 kias or less while flying the procedure turn ahead the fix that defined the steep approach then gear down, power back to near idle, prop full forward. The profile calls for losing 1000' after the procedure turn then another 2300' in 6.8 nm from the FAF to MAP. Forty years ago that was our only approach and it usually was downwind. The key is to stay ahead of the aeroplane in this case by being slowed down before beginning the approach.   

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Chris, I see you are reducing to 17" and then going up to 19" with prop reduction.  What are you starting at for MAP?  What speed are you starting at.  i can't  say this technique is wrong, I've not tried it.  It clearly worked for you.  Perhaps the question is, have you tried the opposite technique of pushing the prop forward to increase drag or are you saying that you can't stay in the green using that technique?  If that is the case, you are probability flying the extended approach slower than what we are describing above. Doesn't make it wrong, just different.  I don't recall having this as an issue in a 500fpm descent at those power settings.  

The red flag might be that you are doing more work at a more critical time.  When you level off, you need to be more careful with power and if you needed go around power you may overspeed momentarily if you push in power and then prop.  Basically, you have more steps to do at a rather critical time.....where I am pushing my prop in to get to landing configuration, you are pulling it out.   Just a consideration.  

 

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Jeeze, I feel like I was spanked! I guess I didn't read your first post close enough, all I can say after reading it again is when doin the IZA approaches just be slowed down before the IAF. In a utopian no wind situation IAF 6000 airport 674 need to loose 5300 feet in 16.3 miles, at  90kts approach speed or 1.5 miles per min that gives you 10.8 min time to descend that's 530fpm Set the power,  configure early stabilized approach. this descent rate is not unlike most. At a midwest flat lander airport ILS you would need to loose 1700 feet in 4.1 miles that's 640fpm if your on the glide slope and at 90kias no wind. steeper than your approach.  I was just trying to help

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For instrument approaches, I generally slow to 90 knots by the IAF, and ATC generally gets me down to a decent altitude for the approach (even in WV, where I earned my license, bought the Mooney and became instrument rated). For the mid-altitudes that most approaches start, even at Asheville, NC, I generally start at 17" / 2300 on the first leg or turn, and adjust throttle to maintain my desired speed and descent rate. Dropping flaps requires some changes to throttle and trim, depending if I'm on a level or descending leg.

It's a natural setting for me, as I generally run 23 / 2300 of  short breakfast / lunch runs around 3000 msl. Up around 5000-6000, I tend more towards 22 / 2400. So that would be my preference for beginning an approach, both obviously with much less throttle as these are cruise settings.

My red tach area is 2000-2250, so my numbers may not work for you. But they work well for me, since they are what I often use for short cruise settings. Print out the table from your IFR book and make a test flight or two (one per starting altitude) and record the MP & RPM settings for level flight, 500 fpm climbs, descents, etc., and use those.

Like others here, I've heard of pulling the prop back to extend glide range, and sometimes push mine forward for extra braking.

Whatever works for you is best, as long as you remember what to change and what the correct order is. 

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I used to leave the prop in a cruise setting (2500) until I was basically on final; if I pushed it forward it might overspeed (the first couple of times I tried it when I first got it, I watched RPMs spike to 2750 and yanked it immediately). (Might be different now that the governor seems to be exercised and happy again; when I first picked her up, cycling the prop during run-ups was a two-handed affair, now the control moves freely and smoothly.)

2300 is in my "bad" range (2000-2350). So it's easy to end up in that range on an approach if I haven't set the governor lower. Which is one of the reasons this technique is so appealing (that and it really does seem to "slam on the brakes," aeronautically speaking, in much the same way going full-fine did on the 3-blade Arrow I used to fly; I don't get the same braking function with the two-blade prop on the E).

On final, I do the usual GUMPS check, pump on, check gear (again, and again), mixture set properly, prop full forward (at that point, I'm probably 15" or less MP, so it's NBD), etc., so a go-around/missed approach is a non-issue. I only use the "get slow" 19 squared technique when first beginning an approach / descent / etc. from cruise...

 

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I was taught to leave everything where it is, just pull the throttle back.  Someone posted about getting left at 5000 feet till 5 miles out by ATC.   So I went and tried some high approaches.   The first one was field at 1300 and I started at 4500' due to clouds and such.  Cruise speed up to 5 miles out.  Throttle to idle,  Fly level, Let the plane slow.  Wheels down.  Half flaps.  about 95 mph on the decent.   about a 12knot headwind.   Worked out fine.   Had to add a little throttle to make the runway.  The next one was 4000' at the 5 mile point.  about a mile out.  I was still high, so I went to full flaps.     I could have made it if I had gone to full flaps earlier or, s turned, or slipped , but chose the go around.   One thing I think helped on the first landing was choosing a  point a 1/4 mile from the end of the run way to aim at instead of the end of the runway.

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I always get slammed coming into Montrose. MSA is 13K, and the field is 5751'...so it always translates to a super steep descent. Which sucks for our ears. I've ended up just saying I have the field in sight so I can start my decent early. One point a few weeks ago, I was screaming into the aerodrome and made a turn to 4 mile final at 180kts. I thought, "ok, let's see how easy it will be to slow down...i can always go around." So, power back to idle, pitched slightly up, and shed 80kts in 10 seconds. Flaps, gear, and a minute later I crossed the numbers at 85mph, and she was down a few hundred feet after that. I was pretty surprised how quick she slowed with just a little nose up pitch. 

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21 minutes ago, Brian Scranton said:

One point a few weeks ago, I was screaming into the aerodrome and made a turn to 4 mile final at 180kts. I thought, "ok, let's see how easy it will be to slow down...i can always go around." So, power back to idle, pitched slightly up, and shed 80kts in 10 seconds.

Isn't 180 knots well past VNE in an F? Also, the "power back to idle" step is the one I was specifically taught to avoid (insert debate about shock cooling here).

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16 minutes ago, chrixxer said:

Isn't 180 knots well past VNE in an F? Also, the "power back to idle" step is the one I was specifically taught to avoid (insert debate about shock cooling here).

I believe most of us here consider "shock cooling" to be an OWT.

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53 minutes ago, chrixxer said:

Isn't 180 knots well past VNE in an F? Also, the "power back to idle" step is the one I was specifically taught to avoid (insert debate about shock cooling here).

Ah, yes...that was GS. IAS was more like 160kts...

And I was already at 15 inches coming down, so idle was no biggy, plus I was well leaned to keep EGTs hot and CHTs relatively normalized around 280-300. 

On my decent, I typically pull 2 inches every 30 seconds or so...not sure if shock cooling is an OWT or not, but I don't do anything fast (except travel over the ground) in the cockpit. 

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On August 5, 2017 at 6:14 AM, Bob_Belville said:

If your E model is like my '66 the yellow arc starts at 130 kias (150 mias). I don't fly in the yellow in actual moderate or severe turbulence but otherwise I like to live there.   

 

My 1966 E is probably very similar to your 1966 E... :) 

Lycoming doesn't think shock cooling is an OWT: https://www.lycoming.com/content/how-avoid-sudden-cooling-your-engine 

Generally speaking, pilots hold the key to dodging these problems. They must avoid fast letdowns with very low power (high-cruise RPM and low manifold pressure), along with rich mixtures that contribute to sudden cooling. It is recommended that pilots maintain at least 15” MP or higher, and set the RPM at the lowest cruise position. This should prevent ring flutter and the problems associated with it.

Then there's John Deakin: “I'm not a big fan of the various "shock cooling" theories, and I get a case of the giggles when I hear some of the elaborate methods of handling this "problem." But if you do all these improper things, maybe there is such a thing!”

He uses an approach similar to Zef's: “Nose down gently to maintain the speed, running it back up to the limit speed if necessary, pull the prop right back to 2100 or less, then do the other big pull, the "Big Throttle Pull" (BTP). Go on, just pull off anywhere between 10 and 15 inches of manifold pressure, all in one fell swoop. (What the heck IS a fell swoop?) Anyway, one smooth pull, over some seconds, perhaps five or ten. ... After you do this a few times (from a LOP cruise), you'll be able to pull the prop back to 1800, the throttle back to 15 inches MP ...

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Lycoming published that note on sudden cooling about 50 years ago and isn't about to change anything for fear of you lawyers.

I sat through the APS class with John Deakin last fall. On the test stand at GAMI in Ada, they've tried everything Lycoming says "might" cause shock cooling problems on an engine that is carrying much better instrumentation than Lycoming even has. They've not been able to cause any of the problems or effects of "shock cooling". 

John said in the class, the only way to shock cool the engine would be in a straight dive right into Lake Michigan from 15K feet. And it wouldn't suffer any cooling damage until it hit the cold water.

It's a myth.

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You would think shock cooling would go out the window with the first flight into rain...

Nothing cools a hot piece of metal as quickly as dowsing it in copious amounts of cold rain...

In the theory of shock cooling, the cylinders shrink faster than the uncooled piston.  This would cause some binding ... The binding would occur first with the pistons rings.

Done often, the rings would be showing some really heavy wear followed by broken and bent varieties found at annual with the compression test...

How often do airplane pistons get re-ringed?  

I haven't had a re-ringed piston yet that wasn't in need for some other reason.

Best regards,

-a-

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