JimD

Diminishing Useful Load

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20 hours ago, kortopates said:

But only the legal useful load is what matters. 

I would contend that physics is far more important than “what’s legal” when it comes to useful load....

if you violate the legal useful load, the feds might catch you.  If you violate the absolute useful load (plus the safety buffer)... well... physics is less lenient than even the FAA.

so quibbling over 10-50lbs of inaccurately calculated useful load becomes more of a exercise in either willful ignorance... or is mainly a bargaining chip when it comes time to sell.

Even the most diligent amongst us are somewhat “cutting butter with a chainsaw” when it comes to precise W&B calculation... and those that haven’t had their aircraft weighed and balanced (on scales) recently- even more so... either too heavy, or too light.

has anyone here had their aircraft re-weighed and found that the old numbers that had been added and subtracted to over the years were actually accurate (let’s say.. within 6-9lbs of the “calculated” number?). Very curious- but highly doubtful.

and I contend that reweighing, on certified scales, by someone that knows what they are doing, is more accurate than the addition/subtraction method.  It accounts for intangibles (grease, mud nests, rats nests, extra wiring, leather yoke coverings, etc, etc).

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The pre 2900 lbs Js are in a interesting limbo. Nothing changed with an exception of 1 piece of the steel frame IIRC. So, I would think that getting it STCed for 2900lb on takeoffs, 2740 on landing would be doable.


Tom

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I would contend that physics is far more important than “what’s legal” when it comes to useful load....

if you violate the legal useful load, the feds might catch you.  If you violate the absolute useful load (plus the safety buffer)... well... physics is less lenient than even the FAA.

so quibbling over 10-50lbs of inaccurately calculated useful load becomes more of a exercise in either willful ignorance... or is mainly a bargaining chip when it comes time to sell.

Even the most diligent amongst us are somewhat “cutting butter with a chainsaw” when it comes to precise W&B calculation... and those that haven’t had their aircraft weighed and balanced (on scales) recently- even more so... either too heavy, or too light.

has anyone here had their aircraft re-weighed and found that the old numbers that had been added and subtracted to over the years were actually accurate (let’s say.. within 6-9lbs of the “calculated” number?). Very curious- but highly doubtful.

and I contend that reweighing, on certified scales, by someone that knows what they are doing, is more accurate than the addition/subtraction method.  It accounts for intangibles (grease, mud nests, rats nests, extra wiring, leather yoke coverings, etc, etc).

All good points and most certainly no plane can defy physics. But I would contend with respect to the Mooney fleet, the most important aspects of the physics is the CG and staying within the CG envelope. The fleet isn't nearly as challenged with max takeoff weight as many other aircraft are. I certainly understand your desire to rely on a fresh weighing for a more "accurate" weight and CG. But based on what I have seen in reality, with weigh-in's all over the map, I personally have much more faith in making simple additions and subtractions to the weight and balance sheet based on precise stations and weights than I do on re-weighing. But that's just my opinion seeing results of re-weighings vary greatly. The Mooney's built pretty strong but max gross weight isn't just limited by the performance of the airframe/engine combo but by the engineering of maximum G loads model is certified too.

 

Edited to remove comments on Rocket Engineering max gross weight takeoff changes and M20 K in-flight breakups that don't really go together.

 

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3 hours ago, M016576 said:

Even the most diligent amongst us are somewhat “cutting butter with a chainsaw” when it comes to precise W&B calculation... 

Hah!  "Cutting butter with a chainsaw."  I'll have to remember that one! :lol:

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54 minutes ago, kortopates said:

The Mooney's built pretty strong but max gross weight isn't just limited by the performance of the airframe/engine combo but by the engineering of maximum G loads model is certified too. As such I am always amazed by how little engineering Rocket Engineering seems to have done to raise the max gross weight substantially in the Missile and Rocket STCs. For example, contrast Rocket's  Perhaps it has bearing on the fact that all of the very few Mooney in-flight break-ups where Rockets IIRC.

I found two in flight breakups of M20K models.  One is a rocket.  The rocket first departed controlled flight in icing conditions near bakersfield- then was assessed to break up (probably due to departing controlled flight and exceeding its placarded speeds). The tail number is N231BY... it’s definitely worth a read just for the ADM discussion.  Totally applicable to some of the icing threads I’ve been reading lately.

the second is attached below- it’s a stock K.  Looks like the autopilot failed in some way that also caused its speed to exceed placarded limits, and the tail ripped off.

I cannot find any evidence of inflight breakups of missiles (the J based rocket product), or in flight breakups that were not attributed to a Mooney airframe exceeding its placarded speed limits.

if you have- I’d love to read the report- but to claim rocket engineering didn’t do their due diligence in their design process is a bit misleading, I believe.

BA632383-BF1C-4352-8A36-2B76464DAD39.png

Edited by M016576
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14 minutes ago, M016576 said:

I found two in flight breakups of M20K models.  One is a rocket.  The rocket first departed controlled flight in icing conditions near bakersfield- then was assessed to break up (probably due to departing controlled flight and exceeding its placarded speeds).

the second is attached below- it’s a stock K.  Looks like the autopilot failed in some way that also caused its speed to exceed placarded limits, and the tail ripped off.

I cannot find any evidence of inflight breakups of missiles (the J based rocket product), or in flight breakups that were not attributed to a Mooney airframe exceeding its placarded speed limits.

if you have- I’d love to read the report- but to claim rocket engineering didn’t do their due diligence in their design process is a bit misleading, I believe.

BA632383-BF1C-4352-8A36-2B76464DAD39.png

All break-up's are due to overstressing the airframe; usually from exceeding air speed limits. Of course I can't blame it on Rocket Engineering only they stand out statistically because I do recall most it not all were Rocket. But obviously the one above was not a rocket.  There is at least one more that went down in the Caribbean that I could not find in the NTSB, but agreed I should not go just by memory to make that statement without re-checking first. 

 

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The only one I was aware of was not a Rocket and went down in the Republic of California from an obvious over stress event.  I'm not going to take the time to research it as it's not germaine to the topic being discussed (IMHO).  Until this point I was with Paul........................ ok, I still am, with exception to beating down Rocket conversions.

I had to weigh the Lancair MANY times, prior to paint and interior, and a final time (or more accurately, several times) when completed.  We calibrated the scales and NEVER found any discrepancy in them.  That said, I was amazed at what 1/2 of one degree OR LESS of air frame difference could make on those damn scales for weight.  I'm talking Mooney empty weight equivalents.  I went from dancing and celebrating to cussing in more than one scaling session.  Paul is right, you better be the most anal person in the world if you desire ABSOLUTE ACCURACY in weights derived from scales on an airplane.  I am, and because of that we must have final weighed the Lancair 6 times.  And as a qualifier, that comment is coming from a Oshkosh Lindy Award winner......... I didn't just throw an airplane together.  Getting a weight you can "take to the bank" is no where near as easy as it sounds.

Tom

 

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You both are right, out of respect for all Rocket engineering conversion owners I am going to remove my comments on that. Even if it was 2 out of 3 it's still only conjecture.


Sent from my iPhone using Tapatalk

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How you set the plane on scales should have no affect on the empty weight and useful load.  But it could definitely have an affect on the CG.

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I have found the best method, and one with some collateral benefits, to raise the useful load is to manage my own gross weight :-). My Acclaim has gained 20# of useful load so far this year, much to the detriment of local fast food places and maybe a tap room or two.

 

it will be interesting to see what mooney announces at S&F this year regarding useful load increases.  Lighter batteries? Lighter electrical stuff? VG’S?

-DE

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35 minutes ago, exM20K said:

I have found the best method, and one with some collateral benefits, to raise the useful load is to manage my own gross weight :-). My Acclaim has gained 20# of useful load so far this year, much to the detriment of local fast food places and maybe a tap room or two.

See, now you've just gone from preach'n to meddle'n.  

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One really nice thing about my vintage Mooney is that I doubt I could fit enough in it to go past my 960 lb useful weight. There just isn’t that much room. The heaviest thing you will ever carry are pax, and they have to be quite diminutive to fit in my back seat. Not that I don’t always have an eye to the situation. I have to admit I did come close to hitting  gross the one time I filled all the seats with adults. Might have busted it by a little with full tanks.

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6 minutes ago, steingar said:

 Might have busted it by a little with full tanks.

Every Mooney will fly over weight.... but none will fly without fuel.

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Wow, amazing how long this thread has gone :). A few observations:

1. The marketing dept. always advertises base price and standard empty weight. These do not include options. Once loaded up with options, as most Mooneys are when originally purchased, the list price and basic empty weight apply and useful load decreases. 

2. Whether or not you include oil in the empty weight depends on the definition of empty weight as noted previously. 

3. Over many years of adding and removing equipment, painting, interior upgrades, etc. the empty weight and CG will be incorrect by some unknown amount. Unless a gross calculation error was made, the error will not significantly affect the performance or handling qualities of the airplane since a lot of margin is built into the gross weight and CG ranges. 

4. If you want to know the correct weight and CG of your airplane, the only way to find out is to weigh it as outlined in the maintenance manual and FAA Weight and Balance Handbook. Any competent A&P with appropriate equipment can do this. To get accurate results, the procedure must be followed carefully and exactly.

5. Airframe failures in Mooneys (and most GA airplanes) are rare and do not happen from excessive airspeed alone. Rather, they happen due to loss of control and excessive g during recovery. Always insist on unusual attitude recovery practice during a flight review.

Skip

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Skip, you may be channeling your inner Anthony.

Jus' sayin.

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3 hours ago, kortopates said:

You both are right, out of respect for all Rocket engineering conversion owners I am going to remove my comments on that. Even if it was 2 out of 3 it's still only conjecture.


Sent from my iPhone using Tapatalk

You’ve made some excellent points too, though- 

 

one thing that your posts got me pondering: why? Why would their be a higher instance of rocket structural failures (real or perceived).

 

my speculation:  the rocket cruises sooooo close to the yellow arc on the airframe... any descent practically requires either a 10nm “coast” to a lower airspeed or speed brakes.  The Missile is the same way (cruising up against the yellow arc). 

I cant speak for the rocket.. but the missile- the KIAS limits for the yellow arc drop down even further due to the 3200lbs max gross... so if you’re heavy, you’re really up against it.  if the rocket is the same way- then any descent would put you up into the yellow. 

Add a little turbulence, a “slam dunk approach” and a pilot that’s behind the airplane... and there you have it....  they are fast airplanes with some amazing features, but I can see how it could get away from a pilot.

just a couple thoughts- totally speculative

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10 hours ago, gsxrpilot said:

Every Mooney will fly over weight.... but none will fly without fuel.

I'm so damned anal about fuel that on that trip, even though we were only flying for about 20 minutes I think I had sufficient fuel to get us to Georgia.  I think I still had enough to outfly my bladder.   My Mooney sips gas, it just doesn't take that much.   

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8 hours ago, M016576 said:

You’ve made some excellent points too, though- 

 

one thing that your posts got me pondering: why? Why would their be a higher instance of rocket structural failures (real or perceived).

 

my speculation:  the rocket cruises sooooo close to the yellow arc on the airframe... any descent practically requires either a 10nm “coast” to a lower airspeed or speed brakes.  The Missile is the same way (cruising up against the yellow arc). 

I cant speak for the rocket.. but the missile- the KIAS limits for the yellow arc drop down even further due to the 3200lbs max gross... so if you’re heavy, you’re really up against it.  if the rocket is the same way- then any descent would put you up into the yellow. 

Add a little turbulence, a “slam dunk approach” and a pilot that’s behind the airplane... and there you have it....  they are fast airplanes with some amazing features, but I can see how it could get away from a pilot.

just a couple thoughts- totally speculative

Older Mooneys, like my '66E, cruise in the yellow and descend nicely at (just below) the red line. SOP. A Mooney is a wine bottle, not an egg, is it possible to break it but it takes an awful lot. 

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9 hours ago, M016576 said:

................one thing that your posts got me pondering: why? Why would their be a higher instance of rocket structural failures (real or perceived)..................

Since flutter is a function of TAS, not IAS, could that be of note?   Rocket turbocharged conversions are flying at higher TAS than most other Mooney mid-body airframes.  

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19 hours ago, exM20K said:

I have found the best method, and one with some collateral benefits, to raise the useful load is to manage my own gross weight :-). My Acclaim has gained 20# of useful load so far this year, much to the detriment of local fast food places and maybe a tap room or two.

 

it will be interesting to see what mooney announces at S&F this year regarding useful load increases.  Lighter batteries? Lighter electrical stuff? VG’S?

-DE

I talk about bicycles the same way.  I kind of laugh when someone will go out and spend thousands of dollars to get a bike that weighs 3 pounds less than one that only costs hundreds.  Just lose three pounds and you get to the same total weight that you have to haul uphill.

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Jim, my C descends at 170-175 mphi at 500 fpm, whether I've been cruising at 3000 msl or 10,000 msl. But I have a fancy, modern, electric C with yellow from 175-200 mph. Even then, I sometimes reduce throttle to slow down for uncomfortable bumpiness.

I, too, would love a Missile . . . . but there are so few.

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6 hours ago, Bob - S50 said:

Just lose three pounds and you get to the same total weight that you have to haul uphill.

I weight 50 pounds less than I did when I bought my current E. More than offset the weight of the 64 gallon bladders, 1 piece belly, and speed brakes. Or Nancy's absolutely necessary luggage.:o

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5 minutes ago, Bob_Belville said:

I weight 50 pounds less than I did when I bought my current E. More than offset the weight of the 64 gallon bladders, 1 piece belly, and speed brakes. 

Not as good as you, but I now weigh 6.5 gallons of 100LL less than I did a couple years ago.

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50 minutes ago, Bob - S50 said:

Not as good as you, but I now weigh 6.5 gallons of 100LL less than I did a couple years ago.

Increased load / range is a great side benefit. My Useful Load is up 4 gallons the last several months.

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On 3/14/2019 at 11:47 AM, M016576 said:

willful ignorance

Best description of most W&B discussions I have ever seen.  If you watch carefully what follows next will be rationalization of the ignorance. 

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