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Mooney Rocket Climb


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5 hours ago, Stetson20 said:

Anybody care to comment on why this Rocket has been sitting on trade-a-plane for so long? I'm shopping now and this is an interesting plane to me. What am I missing?

https://www.trade-a-plane.com/search?category_level1=Single+Engine+Piston&make=MOONEY&model=M20K+305+ROCKET&listing_id=2390460&s-type=aircraft

UL is in the 700’s.  That’s punishing...

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22 hours ago, Schllc said:

UL is in the 700’s.  That’s punishing...

I'd be mostly using it to commute from central MI (9D9) to Chicago Midway. Occasionally, me and my wife on a weekend trip within a 800 mile radius of home. NC, TX, KS, FL where we have friends. We're empty nest and it would be us two and a couple carry on sized travel bags.

That UL is reasonable to me for my mission.

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1 hour ago, Stetson20 said:

I'd be mostly using it to commute from central MI (9D9) to Chicago Midway. Occasionally, me and my wife on a weekend trip within a 800 mile radius of home. NC, TX, KS, FL where we have friends. We're empty nest and it would be us two and a couple carry on sized travel bags.

That UL is reasonable to me for my mission.

Be a little bit cautious here.  In addition to the 3200 GW limit on the Rocket, there are two others that are less well known:

1. Max landing weight:  3083

2. Max zero fuel weight:  2900

how does this matter?  Well someone above says the UL is in the "700s" so let's guess at 750.  with 3200 GW that means empty weight is 2450.  That means you can put 450 lbs of stuff OTHER THAN FUEL in the airplane to make total zero fuel weight 2900--that means people bas and miscellaneous.  This pretty much makes my Rocket a 3 person airplane unless 2 of them are very small. 

That's a big limitation--probaby means unless you're very small people it's never more than a 2 person airplane.  I weigh about 180# fully dressed, my wife I estimate 140# (but I don't tell her that :D).  together we're 320#.  If this was my airplane the biggest 3rd person we could get in would have to be less than 130# .  IF this airplane is really around 2450 empty, you have to think about whether you EVER need a 3rd person over 130 lb in the airplane with you, because you're probably not going to be able to do it.

AND THEN:

if you're at 2900, you can carry only 300 lb of fuel or 50 gallons.  Runnning at 65% power I'll burn 37-40 gallons in 2 hours and cover about 400 miles no-wind. I wouldn't be real comfortable landing with only 10-12 gallons left on board, total, so maybe 6 gallons a side?  no thanks...

AND THEN:
You may always be loaded such that at takeoff you're ALWAYS over max landing weight.  Not a show stopper but something to keep in mind as there may be days, airports, and conditions when you don't want to be there at takeoff.

this is not all gloom and doom though. In my limited experience 231-based Rockets have a higher UL than 252 based Rockets. Don't ask me why, maybe @carusoam has a theory. So a 231 based Rocket in the 700's is a little odd.  You might luck out and find an old error in the W&B that makes this better.

Bottom line: you want to look at this airplane very carefully, including the W&B sheet, and figure out what can be done with it. FWIW my airplane lost about 70 lbs with interior and avionics total refit so that's an option.

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For major altitude changes, I climb at the "Climb 100%" power point on the 305 Rocket Power Settings chart: wide-open throttle, 38" MAP/2650 RPM/<1450F TIT.  I climb out at 1000 fpm and ~145 MPH IAS, and the engine runs cool to as high as I want to go - the CHT and oil temp needles never go higher than mid-scale, and TIT stays well below the 1450F TIT 100% power limit.  In my aircraft, this results in 35-36 GPH fuel flow, about 10% over the power chart.  The last few millimeters of throttle travel give an extra boost of fuel flow, which is critical to keeping TIT, CHT, and oil temp low at high power.  If I climb at "Climb 88%" 35" MAP/2500 RPM, I don't get the extra fuel cooling, TIT is higher, and both CHT and oil temp climb slowly towards the upper end of the scale.  I do have to keep my hand on the throttle, because otherwise in the climb it has a tendency to push out slowly, and then I lose that extra fuel cooling and temps start to go up.

I should say I worked hard with my A&P to dial in the fuel flow schedule.  I don't remember if I wrote about my experience with this before.  If not, it's probably worth a detailed post.  Anyways, for this thread, let me just say that if you are seeing high and increasing CHT/oil temp at WOT, or your TIT isn't below 1450F, you aren't getting enough fuel cooling and your system needs to be adjusted.  On the other hand, if your temps are fine but you are getting an occasional "spit", meaning a fleeting single-cylinder misfire or worse, check your fuel flow.  If it's much above ~36 GPH, you probably have too much fuel flow at WOT, and your system needs to be adjusted.

I have run calculations for overall fuel consumption on cross-country flights at 100% power climb/35 GPH/1000 fpm vs. 65% power climb/18 GPH/500 fpm and it's almost a wash.  That was a surprise, because at the lower power settings you can take advantage of some leaning (not LOP, mind you) and your specific fuel consumption (fuel flow rate/horsepower) improves.  When you are climbing at WOT, you are running so rich you are at the point where the extra fuel is only there to cool the engine, not produce more power.  65% power vs. 100% power on the Rocket is a 100% increase in fuel flow for only a 50% increase in power.  But you spend less time at lower altitudes where drag is higher and you can dial back to an economy cruise power setting sooner.  On a typical two-hour mission, the difference for me is about a gallon or so saved by climbing at 65% power.  It's hardly enough to make up for the plodding climb rate.  I'm flying a *Rocket*, after all.  My technique is to climb at 65%-75% power for small altitude changes, climb at WOT/1000 FPM/full rich for large altitude changes, and nothing in-between.

Regarding the W&B questions, I suppose that's a bit OT, but FWIW an accurate W&B was critical to my purchase decision.  The Rocket 305 with the gross weight increase STCs *can* carry good payload.  I'm currently at 1020 lbs useful, and that's even taking into consideration that the 1979 M20K that was the basis for my 305 conversion has *eight* gallons of unusable fuel.  Yep, 48 pounds of dead weight, it's right there in the type certificate data sheet.  If I had serial number 25-0447 or later, that reduces to three gallons unusable and I'd be at 1050 lbs useful.  I'd pay real money for an STC that would give me those thirty extra pounds.

More than the gross weight limit, though, is the unusual W&B profile of Rocket 305.  The gross weight increase from the STCs only applies to a certain CG range.  When I'm loaded to max gross with full fuel, pilot and copilot, and baggage, I'm often very near the forward CG limit of this limited CG range.  Here's a graph that illustrates this with a typical loading.  The top of the yellow line represents full fuel, and the bottom represents empty:

CGPlot.png.bf6e65b74830ecadb8288edce3499b4e.png

When I was looking for a Rocket 305 to purchase, I had great difficulty finding accurate W&B information.  Some sellers were reluctant to share W&B information, even though you'd find this out during the pre-purchase document review required by any lender or smart cash purchaser.  A few that did couldn't explain, with the empty weight and C.G. location they were claiming, how it was at all possible to fly full fuel with two people and baggage legally, even though that would still be below max gross.  I suspected two things: a) disinterest in putting in the effort to make sure the W&B was accurate, and b) a grand conspiracy to ignore the complex Rocket 305 W&B.  But there are safety reasons the W&B envelope is shaped as it is and they should not be ignored.  Buyer beware - ask questions - do your research.  I ended up purchasing from a gentleman who swore up and down that I was wasting my time and his, but who was at least willing to email me his full W&B history.  He insisted everything was correct until I pointed out the basic math error (decimal point in the wrong position) present on the very first STC W&B entry back in 1979 (not long after he bought the aircraft new) which, when corrected, shifted the CG rearward over one inch.  Take a look at the graph above and see what a forward CG shift of one inch would have done to the yellow line.  I would not have been willing to purchase the aircraft knowing I'd never be able to fly two people and full fuel legally.  I am so happy I found that error, because this airplane has proven to be awesome.  When I fly two with full fuel, I do need some baggage or ballast in the rear to stay inside the envelope, but I can live with that.

Edited by SpamPilot
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 Broker: Jimmy Garrison at Dmax All American Aircraft 

I looked at an 85 231 Rocket that was very "forward" like that.  Didn't buy it.

Mine has 19 lb of Charlie weights way back in the tail and is balanced almost perfectly right on the main tank fuel station when empty.  This is an example loaded with me, wife, 10 lbs of misc equipment (tow bar, cover, chocks, etc) and one 20 lb suitcase in the baggage compartment, and full main tanks at 75 gallons.

There is no condition in which I must have anything in the back seats or baggage compartment.  My UL is 920.

Screenshot_20210315-203004_Pilot.jpg

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I also have the 19 lbs. of Charlie weights.  My personal disadvantage is being rather larger than the FAA standard 170 lb. pilot for whom the aircraft was presumably designed. :)  That alone pushes the CG forward noticeably.  The need for baggage to balance things out then depends on the weight of the person in the right seat.

I'm tempted to develop an STC for tungsten Charlie weights that would eliminate the need for ballast under any loading scenario.  In the meantime, bricks or gallon water jugs are cheap.

Oh, and my personal experience buying from Jimmy Garrison, formerly of All-American Aircraft, on a different aircraft, was positive.

Edited by SpamPilot
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Interesting...

You have a zero fuel weight...

I don’t think I have seen that lately...

One reason the M20Ks have low ULs...  is all about the original owner and what they wanted to do...

 

Solo, or two up, X-C for work... load it with everything including radar in the wing....

12V systems... lots of excess wire weight...

The fun part... there are so many opportunities to improve UL... from the spinner to the tail...

Start with a composite prop...

PP thoughts only, not a mechanic...

Best regards,

-a-

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4 hours ago, spistora said:

+1 on Jimmy Garrison

I'm going one further and planning on talking to him about a few of the airplanes they have for sale there in east Texas... I like the Rocket, but am re-evaluating wants vs needs. :)

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On 3/15/2021 at 7:41 PM, PJClark said:

 Broker: Jimmy Garrison at Dmax All American Aircraft 

I looked at an 85 231 Rocket that was very "forward" like that.  Didn't buy it.

Mine has 19 lb of Charlie weights way back in the tail and is balanced almost perfectly right on the main tank fuel station when empty.  This is an example loaded with me, wife, 10 lbs of misc equipment (tow bar, cover, chocks, etc) and one 20 lb suitcase in the baggage compartment, and full main tanks at 75 gallons.

There is no condition in which I must have anything in the back seats or baggage compartment.  My UL is 920.

Screenshot_20210315-203004_Pilot.jpg

Can I ask what your empty weight CG is? I'm in an 81 231 Rocket with 19 lb weights in the back too. The empty CG is 42.9" @ 2346 lbs. This doesn't really make any sense; with two people up front and another 50 lbs of ballast in the baggage, I can fill up with 39 gallons before exceeding the forward limit. To get any sort of range, I have to load up the back to the max and put the passenger in the back seat.

This seems off, but at the same time there's no recourse because I don't have any of the old CG papers anymore. We're considering a reweigh to sort things out.

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47.3

Fuel station is 48.9.

Before my complete avionics redo the empty CG was 47.9.  Just about everything in the aft avionics Bay came out...all that KFC200 stuff, the standby vac etc.  So CG moved forward about .5"

Caution...mine was weighed twice in its prior life post-factory and Both Times empty weight went up! Everyone I've spoken to says "whenever I've been asked to weigh an airplane I've never made the owner happy".  Be careful what you wish for in other words it may not go as you hope.

I find this whole thing fascinating though. Some guys with 231 Rockets have a UL over 1000# and I WAS almost 150# less before avionics cut my empty weight. Still at least 80# less. HOW can that be true? Similarly how can our CGs be so different?  Your UL looks like 854...not too different from what mine was...but the CG is way off.

I've about concluded that 100% of these numbers are pure fantasy.

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There isn’t any magic to getting a correct WnB...

But it does take strong math skills... often seen at the college level.

And a strong desire to do it correctly...

ULs have improved with each digital update... modern paint job... appropriate tank seal...

I always expected I would find 100#s of dirt in my plane that lived outside... that never happened...

re-weighing a plane takes a lot of effort... including the proper level of fluids...

 

PP thoughts only, not a mechanic...

Best regards,

-a-

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6 minutes ago, PJClark said:

47.3

Fuel station is 48.9.

Before my complete avionics redo the empty CG was 47.9.  Just about everything in the aft avionics Bay came out...all that KFC200 stuff, the standby vac etc.  So CG moved forward about .5"

Caution...mine was weighed twice in its prior life post-factory and Both Times empty weight went up! Everyone I've spoken to says "whenever I've been asked to weigh an airplane I've never made the owner happy".  Be careful what you wish for in other words it may not go as you hope.

I find this whole thing fascinating though. Some guys with 231 Rockets have a UL over 1000# and I WAS almost 150# less before avionics cut my empty weight. Still at least 80# less. HOW can that be true? Similarly how can our CGs be so different?  Your UL looks like 854...not too different from what mine was...but the CG is way off.

I've about concluded that 100% of these numbers are pure fantasy.

Right, I've heard that too, but with the CG this far forward, the remaining envelope just isn't useful. With two adults up front (say, for a flight lesson), even with the max 120 lbs in the baggage, the plane exceeds the forward limit with more than 40 gals fuel, i.e. 30 minutes of flight with a minimal reserve. For a two-person trip, my passenger needs to sit in the back.

I'm convinced a a mistake was made in a calculation somewhere, but without the old papers, I can't prove it other than with an actual reweigh.

Last question--do you have Monroy tanks? If so, have you seen anything in your POH that says they're at a different station than the mains? An A&P (not one I usually work with, but someone familiar with the Monroy tanks) indicated that the LR tanks should be at a different station because they're aft of the spar, but I don't have any supplements that say this.

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On 3/16/2021 at 2:31 PM, Stetson20 said:

I'm going one further and planning on talking to him about a few of the airplanes they have for sale there in east Texas... I like the Rocket, but am re-evaluating wants vs needs. :)

If you're in Michigan, I'd probably recommend a rocket with TKS

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1 hour ago, louisut said:

Last question--do you have Monroy tanks? If so, have you seen anything in your POH that says they're at a different station than the mains? An A&P (not one I usually work with, but someone familiar with the Monroy tanks) indicated that the LR tanks should be at a different station because they're aft of the spar, but I don't have any supplements that say this.

I do, and I was surprised to learn here on MS sometime last summer that they are at station 71 whereas the mains are around 48. I have yet to load more than 5 gal each in the outboards deliberately after pumping 37.5 a side in the mains.  But the fact is that if you fill the mains more than about 25 gal a side some of it flows outboard into the aux tanks over the course of 10-30 min sitting on level ground. So IDK what other owners do about that...Rocket or 252 or whatever...but my position is you never know how much is out there after you take off. Or even at takeoff for that matter: I guess you could fuel up, wait 30 min, use a ruler to measure the level in the outboards to estimate gallons, then do W&B. But it would be approximate at best and would change in a non-deterministic way (I think) as you burn fuel so where your cg would be at any moment would be a complete unknown. No better and no worse than at takeoff or landing.

No doubt someone will be appalled by this assertion and forcefully correct me...but I just do it as though its all in the mains and go.  I live.

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Rockets are slightly nose heavy empty. Airplanes are more stable nose heavy. If you don’t run out of elevator on landing you are not too nose heavy. It would be tough to load a Rocket too tail heavy without being over gross. That said a tail heavy airplane is more efficient as it takes less aerodynamic downforce on the tail. But if out of envelope tail heavy the plane is less stable. That is the “Bonanza” problem. As they burn fuel they get More tail heavy. Rockets don’t. The balance point moves forward as fuel burns. Another reason Mooneys are much safer to fly.

Equipped properly with the correct amount of bob weights a Mooney with 2 standard people won’t be out of balance forward. More fuel will not move it out of balance rearward. 100 gallons/600 lbs fuel 340 in the front seats and less than 120 in the baggage compartment will always be within balance. But depending on equipment it could be over gross. Mine had about 1050 useful. 
 

If your math argues with this statement something is wrong with either your math or your paperwork.

PS as long as not out of balance to the rear (very hard to do) a Rocket is pretty happy at 3600 lbs. (unless you are landing) 

or so I’ve been told.

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