What's Your Descending Procedures (let down)?

[corn_flake]

Since I got my M20E few months ago, I spend a lot of time on studying how to operate a Mooney.  When it comes to descending procedures, it eventually comes down to the the following,  

1.  From cruising altitude, reduce manifold pressure to 17" and start pulling back prop to 1950 rpm.  This will bring the manifold pressure back to about 19.5".  The idea is an engine under load will not cool to quickly.  Of ocurse, adjust the mixture as necessary to keep the cylinder temp in a slow decline.  Continue in this configuration until traffic pattern altitude.  At which point, reduce MP to 15" and set prop and mixture full forward and start pre-landing checklist.  

2.  From cruising altitude, leave the prop at the cruise setting and reduce manifold pressure 1" per minute.  Time it so the aircraft would enter the traffic pattern altitude at 15".  At which point, move both prop and mixture full forward and start pre-landing checklist. 

 

Which one do you use?  

[EricJ]

I have a J model, but I just point the nose down to the desired descent rate.   Power stays at full throttle and cruise rpm.

Once in a while I'll pull the throttle back a bit, which is actually a little more efficient, but also slower. 

[FloridaMan]

I go as fast as I can to the pattern. This usually requires some reduction of power to stay in the correct airspeed color band. At some point approaching the field, I advance the prop full forward to aid in slowing to gear speed. I’m not sure that shock cooling isn’t an old wives tail, but I’m not willing to take that risk. I generally just ease the power back on approach (usually within five miles of the field). Gear are down before I’m within two miles. 

[carusoam]

No no no....

Pulling the MP back? That’s not Mooney speed or efficiency....

Ok, efficiency yes, but not speed....   

Stand by for a dozen various ways people plan for their descents... including IFR vs. VFR... and other limitations like Bravo airspace...

 

Many do calculations in their head, miles per minute, and feet per minute, and altitude to be lost...

 

Being prone to use GPS and automation... I used to use a G device that gave vertical guidance like an ILS...

Lately I have been using WingX that gives guidance as you get closer... it gives a descent rate based on distance away...

For a NA Mooney... you can descend at about 400fpm from a ways back and maintain a high airspeed....

As you get into more dense air, removing 1” of mp for each 1k’ is a normal expectation....

be aware of bumps and maneuvering speed... important things for keeping the wings in place....

PP thoughts only, not a CFI....

Best regards,

-a- 

[eman1200]

Nose over and bombs away!

[larryb]

It has been a couple years since I sold the J. So my numbers are a bit fuzzy. Climb and cruise are full throttle at 10k to 14k feet. On the descent, once low enough, I adjusted throttle and mixture every couple thousand feet to maintain 20” and 8.5 GPH. If you leave at cruise settings you wind up too lean and too high power as you descend.

[carusoam]

Flake,

An interesting document, available with training....

Look up MAPA... they have a weekend course around the country, four times each year...

They have a model specific data set that goes really well with your plane. See if you can find that doc.

If able, take in a Mapa weekend. 

Best regards,

-a-

[corn_flake]

Metropolitan Area planning Agency, no....

Michigan Academy of Physician Assistants, no...

Mooney Aircraft Pilots Association, got it!!  

I'll check them out.  Thanks

 

[gsxrpilot]

58 minutes ago, corn_flake said:

Which one do you use?

Neither of those. I'm curious where you were studying that you came up with those two options. 

As you can tell from the responses already, Mooney pilots, just like their airplanes don't like to slow down. There are lots of other airplanes that are really good at slowing down. But we don't like slow, and so we fly Mooneys.

Do some research on shock cooling and you'll find that theory has been well and truly debunked. Once free from that OWT, you'll be free to cash in that altitude and get the speed back you spent in the climb. 

At the top of descent, just trim down for your favorite descent rate, such as 500 ft/min down. Don't touch anything else. At pattern altitude, level off, pull the throttle back and set prop and mixture for landing.

This worked well in my M20C on descents from as high as 12K or 13K. Now in my 252, it works just as well from the flight levels.

[corn_flake]

#1 came from a Mooney specific web site which I can no longer find.  

#2 came from two CFIs for my transition training into Mooney.  One of the CFI has extensive experience with Mooney.  

I'll search for shock cooling again, but it seem most people I talk to still think it's a thing.  

@gsxrpilot  So, do you simply point the nose down at desired decent rate and only reduce MP to keep airplane from going over the max airframe speed?  

Edited October 16, 2019 by corn_flake

[RLCarter]

Very few things are free, especially in aviation. Point the nose down and enjoy the speed

[jaylw314]

I'm one of those weird Mooney owners that prefers efficiency over speed.  From altitude (>9000' MSL), I just been decreasing RPM to 2000 or less and descend.  I don't have an RPM limit, so I've gone as far down as 1600 RPM before.  There's no chance of detonation because your power is too low at that altitude.  I'll close the throttle as I descend if the engine runs rough or lugs.  From lower altitudes, though, I'll just close the throttle.

I get the need for speed on descent, and it's fun to see 180 knots on the GPS, but a slower descent has a few advantages:

• Fewer sick passengers when there's turbulence
• More time and less chance of falling behind the airplane
• Less fuel used (you start your descent earlier)
• Easier getting the plane slown down at the end

 

[carusoam]

Nothing weird about increased efficiency...

cue 201er...

But... if you’re favorite speed is named after Karsen(?)  The Vz guy...

You either fly really far.. or always spell CB with a bold C...    

 

201er likes to fly for really long distances... no stops...

Best regards,

-a-

[Hank]

Descending in your Mooney is easy. I calculate the descent by counting on my fingers how many thousands of feet from pattern to where I'm cruising; double that number; then add two or three, and when my fancy WAAS GPS shows I'm that final number of minutes from destination, I push on the yoke to establish 500fpm descent and trim for hands free.

This generally has my C indicating right around 160-165 mph. Va = 132 at gross, less when lighter, so start earlier and go slower if it's rough. This high speed descent turns altitude into free airspeed and makes up for the low speed climb at the beginning of the flight. 

Because MP increases as you descend into thicker air, periodically ease the throttle back and the mixture forward to roughly maintain your cruise MP and EGT values. You should arrive at TPA somewhat slower than your descent speed, with a few miles left to slow down. I generally walk the throttle back and keep trimming up to stay level, with the goal of entering the pattern and lowering Takeoff Flaps at 120-125 mph at about the same time.

Ain't much easier, and I can do the "mental math" even when I'm tired and / or distracted (but if distracted enough, may miss the proper beginning point . . . ).

Happy flying!

P.S.--if the given speeds for my mighty C are too high for your Mooney, please adjust them downwards by the correct amount. Some people with those hard-to-hot-start fuel injected engines have been known to not touch throttle or mixture until pushing everything forward on short final, but coming down from last trip's 10,500 msl to 1700 pattern (almost 20" up high would be ~28" in the pattern, way too high power at 2500 cruise RPM down low; 28 + 25 >> 46 Key Number for my engine!!

Edited October 16, 2019 by Hank

[SantosDumont]

I nose over and pop out the speedbrakes. 

[corn_flake]

@Hank  At what point do you push the prop and mixture full forward?  When you reach TPA? 

The last time I point the nose over, My E was doing about 190 mph coming down from 10,000'.  It doesn't seem right to be going that fast.     I promptly pull the MP back 1" at a time to keep speed under 160 mph.  It's going to take a bit to get use to the speed.  

[bob865]

I've found in my plane that pointing the nose at the ground at 20 in and 500 fpm will give me a 160mph keeping me out of the yellow in my plane.  I plan a 500 fpm decent and when that time dictacts I point the nosea at the ground and trim.  If I'm high enough, no throttle movement is needed, but as I decend I keep the MP at 20. 

To OP, if you're worried about shock cooling, I think there is an article from the mighty Mike Busch that shock cooling is a hold over from big radials and not much of a concern in our little flat fours.  Don't get me wrong, I still wouldn't recommend chopping the throttle to idle and diving right after a high power climb, but cruise to decent isn't that much of a worry.  Plus, it's a mooney.  It goes fast.  Why decend without power?  It's just slower.   

[Shiny moose]

3 hours ago, corn_flake said:

@Hank  At what point do you push the prop and mixture full forward?  When you reach TPA? 

The last time I point the nose over, My E was doing about 190 mph coming down from 10,000'.  It doesn't seem right to be going that fast.     I promptly pull the MP back 1" at a time to keep speed under 160 mph.  It's going to take a bit to get use to the speed.  

 

3 hours ago, corn_flake said:

@Hank  At what point do you push the prop and mixture full forward?  When you reach TPA? 

The last time I point the nose over, My E was doing about 190 mph coming down from 10,000'.  It doesn't seem right to be going that fast.     I promptly pull the MP back 1" at a time to keep speed under 160 mph.  It's going to take a bit to get use to the speed.  

I think you need to rethink that a little, not an insult.

[jetdriven]

The yellow arc is normal operation. Don’t fly there in severe turbulence, but otherwise use it. Lots of these planes cruise in the yellow arc. 

[rbridges]

I generally pull to 16 or 17 MP.  I get close to VNE with full throttle during a descent.  

[Shiny moose]

Yellow arc is smooth air operation, green arc for bumps, severe turbulence  you should be at VA 

[Prior owner]

Alright guys....perhaps we should define “smooth air” 

[jetdriven]

Let’s examine the certification standards and the gust loading. Then examine how many m20 airframe failures There have been. 
In short, outside of a thunderstorm or wake turbulence, you aren’t breaking the airplane at any airspeed under redline. 
Va and maneuvering speed and full control deflections are another issue altogether. 

[gsxrpilot]

7 hours ago, corn_flake said:

@gsxrpilot  So, do you simply point the nose down at desired decent rate and only reduce MP to keep airplane from going over the max airframe speed?

Yes. And my speed in the descent is almost always well over 200 knots TAS or high in the yellow on the ASI.

[steingar]

Point the nose down and get some speed.  My only problem is I wind up in the yellow when I do this, and it's often turbulent at lower altitudes.  In these cases I'm forced to lower the manifold pressure and slow down.  I usually slow down and dirty up the airframe about 5 miles out of the pattern.  On downwind I do my GUMPS checks.