231/252/201 useful loads

[cnoe]

1 hour ago, N9201A said: '78 J with 1070 UL.

It appears to me that the older J's have a higher useful load. Why is that?

My '78 J has a UL of 1,000#. Includes a backup vac pump and AP gear in the tail. Old avionics weighs a lot and new stuff gives back considerable UL.

At 10k in a NA I can fly pretty much whatever mixture I want (LOP in my case) but I think about 11 gph ROP is typical up there.

The trip across W Texas, N Mexico, into Colorado is awesome. Just watch out for those pesky rattlesnakes in the fuel hut at Andrews County.

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[N9201A]

Older Js that have been updated are UL wonders. Faster and more efficient than turbos below 10k with longer legs.

[KSMooniac]

'77 J with 1025 UL. Modern loaded panel (no legacy avionics), MT prop, STEC 30 A/P, no electric trim, ultra leather (much lighter) interior, standard/thin windows, etc. yield a lightweight plane. No fiberglass belly, wing tips, etc.

All models got fat with options as they matured. Later J's can get the GW bump from 2740 to 2900 lbs, but of course still have 200 HP so performance will suffer at the higher weights. 252's can get the Encore conversion for +10 HP and +230 lbs so that should get those useful loads back to around 1000 lbs. That gives tremendous flexibility to trade fuel for payload since fuel burns are lower than the bigger engine variants that will have 900-1100 lb useful loads.

Gig 'em!

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[ArtVandelay]

My 78J weighed 1744lbs as delivered, thats 996 UL. My electronic version of a POH from 1981 weighed 1838 as delivered, thats 902 UL.

Then wingtips, thicker glass, gapseals, wing lights, cowl bridge whatever that is, and all the other speed mods added 52 lbs.

[N5756v]

Kinda jealous of those J numbers

1984 231 and I have 916 UL , i have Ap , turboplus Intercooler , built In oxygen

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[Bob - S50]

21 hours ago, aviatoreb said:

Probably makes the airplane a tad faster with aft CG with here back there too.

There you go, forcing me to think again...  How much faster by moving 200 lb from the front seat to the back seat?

Short answer:

At higher speeds (75% power) about 0.25 knots.

At lower speeds (45% power) about 1 knot.

That makes sense since the weight distribution will have the biggest effect when induced drag is a bigger player.  As speed increases and parasite drag becomes the main factor, the distribution has less impact. So fly fast!

Long answer:

Using my J POH...

Assume 15 feet from CG to tail center of lift and also assuming an average weight of 2400 lbs.

Moving the CG 0.1' (1.2") will change the pitching moment by 240 #'.

Divide that by 15' to determine the change in tail lift required to offset the moment and you get 240/15 = 16 lbs for each 1.2" change in CG location at 2400#.

Looking at my particular airplane, moving 200 lbs from the front to the rear seat moves the CG about 3.6" (or close anyway, a little poetic license).

That means a change of 48 lbs change in tail lift with corresponding 48 lb change in required wing lift.  Call it the equivalent of 50 lbs less weight.

According to my POH, a 440 pound difference in weight makes (approximately) a 2 knot difference in speed at 75% power, about a 4 knot difference at 65% power and about an 8 knot difference at 45% power.

Since the CG shift resulted in about 1/9 th that amount, I can probably assume it have an a proportional effect on speed.

Now, back to football.

Bob

[ArtVandelay]

My Js elevators are in the down position, ie its already tail heavy, I wouldn't want any more weight back there, probably make the plane slower.

[cnoe]

My Js elevators are in the down position, ie its already tail heavy, I wouldn't want any more weight back there, probably make the plane slower.

This has been discussed a lot on MS, and still I don't entirely understand it. My elevator too is slightly down while trimmed for cruise on most configurations but I believe the horizontal stab is still applying a "downforce" on the tail (perhaps attributable to the Mooney's unique hinged tail.

I, among others, believe my plane would be faster if the elevator was perfectly aligned with the horizontal stab during level flight. Somebody remind me if this was resolved earlier.

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[Tx_Aggie]

20 hours ago, cnoe said:

My '78 J has a UL of 1,000#. Includes a backup vac pump and AP gear in the tail. Old avionics weighs a lot and new stuff gives back considerable UL.

At 10k in a NA I can fly pretty much whatever mixture I want (LOP in my case) but I think about 11 gph ROP is typical up there.

The trip across W Texas, N Mexico, into Colorado is awesome. Just watch out for those pesky rattlesnakes in the fuel hut at Andrews County.

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That's a great stop, home of  world famous Buddy's drive inn steak fingers! Also the lowest fuel in west Texas. 

Edited September 12, 2016 by Tx_Aggie

[ArtVandelay]

When they lengthen the tails, did they move the wing backward to compensate for the extra weight aft? My theory is they didn't, so the J with a small engine and long tail is tail heavy, once they went with bigger engines in the K, the CG move forward again.

[gsxrpilot]

On September 11, 2016 at 5:45 PM, Tx_Aggie said:

That's a great stop, home of  world famous Buddy's drive inn steak fingers! Also the lowest fuel in west Texas. 

Actually, most days, the cheapest fuel in Texas is Rusk Co. which is only 5 Mooney minutes from KGGG which is famous in our world.

[johncuyle]

On 9/9/2016 at 10:56 AM, M20Kid said:

I know Jerry probably got the LAST Airflow Systems intercooler.  I was very interested in finding one but haven't yet.  I have a TurboPlus Intercooler in my hangar but I'm just not as interested in their product as the Airflow Systems.  I guess that's why it's still in the hangar

 

My 231 does not have an intercooler.  The only one I've found that's available is the TurboPlus.  I'm curious what the differences are between their unit and the Airflow Systems.

[jrwilson]

On September 9, 2016 at 8:24 PM, Tx_Aggie said:

It appears to me that the older J's have a higher useful load. Why is that?

Less goodies on the older ones?

[M20Kid]

2 hours ago, johncuyle said:

The only one I've found that's available is the TurboPlus.  I'm curious what the differences are between their unit and the Airflow Systems.

The TurboPlus takes about 30 hours+ to install because it requires the NACA duct in the right side of the cowl and all the associated duct work.  The Airflow Systems intercooler just bolted to the back of the engine without any additional duct work, so only required about 10 hours to install.  At the usual cost for a mechanic, that 2AMUs would be nice to keep.  I also understand the Airflow Systems intercooler was more efficient and had a greater temperature drop across the system.

[Jsavage3]

On 9/11/2016 at 0:33 AM, N9201A said:

Older Js that have been updated are UL wonders. Faster and more efficient than turbos below 10k with longer legs.

Faster than a 231 perhaps, but not a 252.  I owned an 86' J and now I have an 87' 252...the J is a great machine, but I'm in love with my 252!

[smccray]

1987 M20J 205 with 1024 useful load. That's @ the upgraded 2900 gross weight.  The 205 is the early model of the 2900 lb J models. 

[cnoe]

When they lengthen the tails, did they move the wing backward to compensate for the extra weight aft? My theory is they didn't, so the J with a small engine and long tail is tail heavy, once they went with bigger engines in the K, the CG move forward again.

You got me wondering about this so yesterday I measured the distance between the wing and horiz stab on my '78 J. Can somebody provide similar measurements on a SB and a LB for reference?

See pics but I measured between the inboard flap corner and the leading edge of stab at the rib ~directly aft of that point. The distance was ~93" (hard to be precise doing this solo).

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[carusoam]

Parking an LB next to a J, you can see the added length up by the baggage door.  201er and I parked together at a fly-in and made a few observations.

I believe they are chunks of 10" sections from short to mid, and mid to LB....

Folding the rear seats down of an LB, provides for a lot of room.

If your financial administrator has big bags and likes to sit in the back seat, the LB is perfect for her!

Best regards,

-a-

 

[gsxrpilot]

2 hours ago, cnoe said:

You got me wondering about this so yesterday I measured the distance between the wing and horiz stab on my '78 J. Can somebody provide similar measurements on a SB and a LB for reference?

See pics but I measured between the inboard flap corner and the leading edge of stab at the rib ~directly aft of that point. The distance was ~93" (hard to be precise doing this solo).

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My K should be the same as your J. I'm curious and will put the tape on it next time I'm at the airport.

[johncuyle]

16 hours ago, M20Kid said:

The TurboPlus takes about 30 hours+ to install because it requires the NACA duct in the right side of the cowl and all the associated duct work.  The Airflow Systems intercooler just bolted to the back of the engine without any additional duct work, so only required about 10 hours to install.  At the usual cost for a mechanic, that 2AMUs would be nice to keep.  I also understand the Airflow Systems intercooler was more efficient and had a greater temperature drop across the system.

I see.  I was under the impression that the NACA duct reduced drag somewhat and also slightly improved cooling airflow so I figured that would be the more desirable route, excepting the cost.  I did wonder which kit had the better heat exchanger, though.  Thanks.

[johncuyle]

On topic:  1980 231, 910 useful.  Built-in oxygen, Merlyn but no intercooler, vinyl and cloth interior, two-blade hot prop, original radio stack plus an ancient VFR GPS.  I sort of expect any improvements I do to it to eventually net out to about its current load, or possibly pleasantly surprise me (that radio stack has to have a lot of dead weight in it.)

[Mcstealth]

Don't Eagles have the most UL in our fleet? I think I remember seeing 1125# by someone here on the site.

df

[carusoam]

A 310hp Eagle is quite the performer.  it's MTOW is limited by the POH, but it's empty weight is the lowest of the LBs.

Of course, the empty weight increases with each upgrade.

Best regards,

-a-

[FlyDave]

I had a J and now a Bravo.

I think the 201 is the most increadible airplane ever built! The perfect balance between speed and efficiency!

That being said, the Bravo ain't a bad ride.

[jonhop]

84J with a useful load of 913.7 and stock avionics except for the GTN 650 that was added instead of the KNS-80 before I bought her... Don't fly so much for speed yet, as I have been building cross country and simulated IFR time, while working towards my IFR certificate. On a couple of occasions I have bumped up the throttle and have no doubts that my J can cruise at 150+kts at or above 9500. She doesn't have an engine monitor, so I fly strictly by the POH, which requires 100° ROP for best power and 25° ROP for best economy at cruise MP settings. I've observed 130+kts average at 7-8GPH while flying at 25° ROP at 22 to 23" MP at 9500 and 8500 when I escape the San Diego area to the east and north on long cross countries...

Edited September 29, 2016 by jonhop