How does your Rocket/Missile compare?

[aviatoreb]

Question:  

If you are a rocket owner or a missile owner, how does your airplane perform compared to book settings, fuel flow, and speed?  Let's not get into a LOP-ROP debate - let's keep the discussion tight. I am asking simply if your airplane matches the predicted book setting, and POH is written in ROP.

 

Background:

My rocket seems 5 to 7 kts slower than book generally at all altitudes and all settings, and I have been blaming my tks which is not a particularly smooth tks install.  The tks was installed in 1994 before it was converted to a rocket in 1997.  So the tks is a particularly early adopter install.  It almost sits on top of the leading edge instead of flush with the leading edge that I see on the latest installs.  I have been wondering lately if something can be done to smooth it out, some kind of puddy or something (during a repaint?)

 

But then I was just looking and comparing the following tables and I realize that something is not right with these tables.

 

http://www.rocketengineering.com/content/rocket-performance

http://www.rocketengineering.com/content/missile-performance

 

Check out the lines in the missile:

 

%    alt       TAS hp  MAP rpm   gph

65 12500 183 195 20.0 2550 15.7

55 12500 180 165 18.0 2250 13.9

 

compared to the rocket lines, 

 

%    alt       TAS hp  MAP rpm   gph

65 12000 195 200 30.0 2200 18.0

55 1200 186 170 26.0 2200 15.0

 

Those horsepower lines are mostly the same for 65% and 55% since the engines are 300 and 305 at 100% respectively.  So why would the rocket at almost the same altitude be doing at 65% and 55% 7 and 6 knots faster respectively?  It doesn't seem possible since the airframes are almost identical, esp with almost the same long noses on the 201->missile mod, and mostly the only difference is the missile has what I would have guessed is an even better scimitar prop, vs the rocket's mccauley, tipping the favor in the direction of the missile not the rocket.

 

Hmmmm…. I wonder if rocket was exaggerating the rocket numbers and those missile numbers are more realistic?

 

I always figured I was 5-7 slower than book due to my tks, and also I was guessing book was made on the most modern 252 converted to a rocket, with all the very latest aero tricks, whereas my 1981 M20k formerly 231 has many but not all the best aero tricks.

 

All that said, check out the engine efficiency difference between these two engines.  Eg. for the rocket to produce 200hp it calls for 18.0gph for book (and I typically run ~18.5 since I like the egt setting better since the book was made during an era when 50ROP was considered a good place to operate), and the missile calls for 15.7 to produce 195hp.

[BobAustin]

Eric,

 

My Missile is #5 conversion (1995) and I have all logs and flight test results from Rocket as well as all my tests.

 

The speeds are influenced by atmospheric pressure, weight, cg and temps.  Must be colder in Washington state than in Texas where most of my flying is done.

 

Anyway my speeds are about 5 kts under book at lower altitudes but increasing to equal to book at 9,000 and above.  My typical flight with 90+ gallons, 310 lbs up front and about 100 lbs baggage at 11,500 and 13.5 gph is 183K.  

 

Rocket is like all other manufactures stating speeds at best conditions not real world .

 

The support for information and parts from Rocket is better than Mooney in recent years.

 

I have had two Mooney 201, Cessna 340 , Eclipse500 Jet and Cirrus SR22TN and the Missile is the best speed/economy/maintenance/reliability compromise of them all for me.

[Seth]

Erik-

 

I'll post with numbers soon. 

 

-Seth

[Seth]

Eric,

 

My Missile is #5 conversion (1995) and I have all logs and flight test results from Rocket as well as all my tests.

 

The speeds are influenced by atmospheric pressure, weight, cg and temps.  Must be colder in Washington state than in Texas where most of my flying is done.

 

Anyway my speeds are about 5 kts under book at lower altitudes but increasing to equal to book at 9,000 and above.  My typical flight with 90+ gallons, 310 lbs up front and about 100 lbs baggage at 11,500 and 13.5 gph is 183K.  

 

Rocket is like all other manufactures stating speeds at best conditions not real world .

 

The support for information and parts from Rocket is better than Mooney in recent years.

 

I have had two Mooney 201, Cessna 340 , Eclipse500 Jet and Cirrus SR22TN and the Missile is the best speed/economy/maintenance/reliability compromise of them all for me.

 

Bob - You're conversion is #5, but I note that your airframe states M20J/G - was your's a G converted to a J converted to a Missile since technically the G is a mid body?

 

-Seth

[aviatoreb]

Bob - You're conversion is #5, but I note that your airframe states M20J/G - was your's a G converted to a J converted to a Missile since technically the G is a mid body?

 

-Seth

 

Thanks Seth.

 

Look at the bottom of his email…it sounds like he has many airplanes.  Maybe 2 Mooneys.

[aviatoreb]

Eric,

 

My Missile is #5 conversion (1995) and I have all logs and flight test results from Rocket as well as all my tests.

 

The speeds are influenced by atmospheric pressure, weight, cg and temps.  Must be colder in Washington state than in Texas where most of my flying is done.

 

Anyway my speeds are about 5 kts under book at lower altitudes but increasing to equal to book at 9,000 and above.  My typical flight with 90+ gallons, 310 lbs up front and about 100 lbs baggage at 11,500 and 13.5 gph is 183K.  

 

Rocket is like all other manufactures stating speeds at best conditions not real world .

 

The support for information and parts from Rocket is better than Mooney in recent years.

 

I have had two Mooney 201, Cessna 340 , Eclipse500 Jet and Cirrus SR22TN and the Missile is the best speed/economy/maintenance/reliability compromise of them all for me.

 

Wow - that is a lot of airplanes!

 

Thanks Bob.

 

My perception all - esp when looking at the two sets of tables I posted above, is that perhaps the rocket is exaggerated but maybe the missile is not, esp when comparing how the rocket table is suggesting the rocket is significantly faster than a missile - at the same altitudes and horsepowers.

 

So as I said, mine seems 5-7 kts. slower than book, so I am questioning if I am expecting to much to match book.

[BobAustin]

Seth,

I should change my listing to M20J/Missile.  The "G" was for equipment suffix.

[RJBrown]

When I had a Rocket (1000 hours 12 years ago) I used Rocket Engineering's data to set power. I found their data to be a bit conservative. Mine always out performed the chart. If you are not getting the performance shown in their charts there is something wrong with YOUR plane. TKS can hurt, even more if it is as rough an install as you describe. Being "out of rig" can cause a slower plane also. Never flew a Missile enough to comment there. Conrad was very proud of the fact that his were "real world numbers" There are a lot of planes that don't reach advertised numbers, can you say 201 and 231 for example. All the manufacturers seem to have flown a specially prepped plane to achieve the book numbers. That said I believe Conrad succeeded in publishing real world, achievable numbers. The numbers I doubt are Mooneys. How can an Acclaim with a larger airframe, more weight and LESS horsepower out run a Rocket? Can't.
 

[aviatoreb]

When I had a Rocket (1000 hours 12 years ago) I used Rocket Engineering's data to set power. I found their data to be a bit conservative. Mine always out performed the chart. If you are not getting the performance shown in their charts there is something wrong with YOUR plane. TKS can hurt, even more if it is as rough an install as you describe. Being "out of rig" can cause a slower plane also. Never flew a Missile enough to comment there. Conrad was very proud of the fact that his were "real world numbers" There are a lot of planes that don't reach advertised numbers, can you say 201 and 231 for example. All the manufacturers seem to have flown a specially prepped plane to achieve the book numbers. That said I believe Conrad succeeded in publishing real world, achievable numbers. The numbers I doubt are Mooneys. How can an Acclaim with a larger airframe, more weight and LESS horsepower out run a Rocket? Can't.

 

Thanks RJ.  Well there you go - I guess it is probably my less smooth than usual TKS.  It hasn't been bothering me terribly since I really do like having TKS and even 5-7kts slower it is still such a darned fast airplane that no one complains when they ride with me.

 

I do not believe my airplane is out of rig - it flies beautifully hands off - that is a definitive test isn't it?

 

RJ I would be curious of your perspective though - besides asking about my plane, and do people make book in general, I am really curious how the rocket and missile might be 7 knots different from each other at almost the same altitude and absolute power setting.  Eg, shouldn't they be going about the same speeds at 12,000 and 200 vs 195 horsepower?

[aviatoreb]

Sorry, Erik, but flying hands off doesn't necessarily mean that your plane is rigged properly. I think that you'll need travel boards, jacks, a level and a copy of the service manual in order to make that determination.

OK, back to your regularly scheduled Rocket and Missile programming . . .

Jim

 

Oh - I didn't know that Jim.  I always figured mine was well rigged since it flies straight, so I have nothing to gain there.  I would like nothing more than to discover that my airplane is not well rigged and that some better rigging will eek out some missing efficiency.  Well - annual is in 6 weeks, so I will put a rigging check on the to do list.  Thanks!

 

Now - yes - back to the regularly scheduled rocket-mssile program.

[aviatoreb]

Oh - I didn't know that Jim.  I always figured mine was well rigged since it flies straight, so I have nothing to gain there.  I would like nothing more than to discover that my airplane is not well rigged and that some better rigging will eek out some missing efficiency.  Well - annual is in 6 weeks, so I will put a rigging check on the to do list.  Thanks!

 

Now - yes - back to the regularly scheduled rocket-mssile program.

 

And related.... why does an airplane go out of rig?  I mean supposedly our airplanes are perfectly rigged when they leave the factory - or at least after they are repainted.  Does an airplane need to be periodically re-rigged?  If it has not been rigged for many years, is it likely to be out of rig?  And if so, what makes an airplane drift out of rig with time?

[M016576]

When I had a Rocket (1000 hours 12 years ago) I used Rocket Engineering's data to set power. I found their data to be a bit conservative. Mine always out performed the chart. If you are not getting the performance shown in their charts there is something wrong with YOUR plane. TKS can hurt, even more if it is as rough an install as you describe. Being "out of rig" can cause a slower plane also. Never flew a Missile enough to comment there. Conrad was very proud of the fact that his were "real world numbers" There are a lot of planes that don't reach advertised numbers, can you say 201 and 231 for example. All the manufacturers seem to have flown a specially prepped plane to achieve the book numbers. That said I believe Conrad succeeded in publishing real world, achievable numbers. The numbers I doubt are Mooneys. How can an Acclaim with a larger airframe, more weight and LESS horsepower out run a Rocket? Can't.

The first place I'd look if your plane is not making book numbers, but "feels" or "seems" to be performing well is your instrumentation. This goes the same for a plane that always "beats" book numbers. 30 year old ASI's aren't getting any more accurate with age. If you can rule out instrument error, next thing to look at is rigging and modifications.

In my limited experience with my missile I'm finding the numbers to be somewhat inflated possibly- BUT! I'm still getting used to the aircraft's engine instrumentation, which is different enough from my previous J to make me want to hold my judgement. Also, I know for a fact that the OAT install is poor, giving a 10-15 degree delta to true OAT. Data out is only as good as data in....

[Seth]

Seth,

I should change my listing to M20J/Missile.  The "G" was for equipment suffix.

 

Ahh, that makes perfect sense.

 

-Seth

[RJBrown]

You might want to compare numbers between your ASI and a GPS over a 3 legged course and do the math to verify.

I rarely flew anywhere below 12,500. At cruise I burned 20gph. I always flight planned 200 kts. These numbers were always consevative. If I needed to watch my reserve I simply throttled back untill the GPS/Fuel flow meters showed a 30 minute reserve.

[David Mazer]

As RJBrown notes, one of the great things about a Rocket is the ability to fly very fast or throttle back and go forever (a little hyperboly, I know).  A J can make it all the way cross country on one tank but the J just can't make the headway a Rocket can if you maximize the altitude and power settings.  On the low end you still burn more fuel but at 13.5 +/- gph and 8,000 ft, I still cruise about 150-160 kts.

[aviatoreb]

As RJBrown notes, one of the great things about a Rocket is the ability to fly very fast or throttle back and go forever (a little hyperboly, I know).  A J can make it all the way cross country on one tank but the J just can't make the headway a Rocket can if you maximize the altitude and power settings.  On the low end you still burn more fuel but at 13.5 +/- gph and 8,000 ft, I still cruise about 150-160 kts.

 

True - but - Problem is I never seem to have the patience to go that slow when I can go much much faster with a small push of my finger tips.

[aviatoreb]

Ok - I spent a few hours today, at Weber aircraft, a Mooney Service Center at Lancaster, PA.  They have rigged many Mooneys and they came highly recommended.  Nice people.  A cool shop full of very nice Mooneys and also several Aerostars.  I chose them because besides their experience, they go through iterations which include test flying, adjust, test fly, adjust.

 

I was not there long enough to do the iterations, but I was there long enough to bring out the rigging boards and to make a complete evaluation.  They tell me there are indeed several things that can be improved.  Overall they said my plane looks good and it is straight and true.  That's good.  But they said my rudder is rigged slightly to one side, my gear doors aren't quite right, my aeleron positions can be rigged improved for cruise, and also I have a farm of old and no longer used antenna including Loran, ADF, and sky-phone.  Wohoo - so I will return sometime soon when I have a bit more time to address all these adjustments.  I am hoping it will net a few "free" knots.

 

Also by the way, I have the old school many part belly, not the modern one piece belly, but that is too much to change for a few vanity knots.

 

ALso we discussed my TKS install.  They said it is not all that rough - true not as smooth as the newest, but not so bad either.  There was an acclaim in the shop and I was looking very closely.  It was not so different.  They said that simply TKS does rob a few knots. We discussed if the joining could be improved with tape or puddy or something - they said they tried once on an ovation, to no avail.  Despite smoothing the joining to the wing, there was no change in cruise speed.  Oh well.  Good to know though. There was also a Columbia in the shop with its plastic wing and tks, and the tks joining was much smoother than the acclaim that was in turn a bit smoother than mine.

 

Anyway it was a good trip.  And looking forward to squeezing out a few knots in the next month or two.

[David Mazer]

In what world do you think taking your plane to an MSC and having it worked on for unknown number of hours and flights will turn out to be "free"?  If it is, let me know as entropy has reversed and I need to get ready for the end of the world.  Or is the beginning?

[aviatoreb]

In what world do you think taking your plane to an MSC and having it worked on for unknown number of hours and flights will turn out to be "free"?  If it is, let me know as entropy has reversed and I need to get ready for the end of the world.  Or is the beginning?

 

I have several verbose and overly complicated replies to your protest.

 

a) When I quoted the word, "free" the quotes were deliberately chosen to denote that the word free is being used in its opposite form.  The quotes negate the word, in a humorous way, meaning I was tipping my hat to the understanding that airplanes are never free.  So a few "free" knots really means both "a few expensive knots" in terms of dollars, but also "a few "free" knots" in terms of mechanical work.

 

What kind of entropy are you discussing?  Boltzman's interpretation?  Shannon?  Now the former relates to the arrow of time, but the later relates usefully for compression but also has a link to the former.  Since you then refer to the arrow of time, I am thinking you mean the former.  I am a fan of the later in terms of evolution of density, and probability in dynamical systems - I just wrote a book on this topic that came out last week by the way - look me up on Amazon.  Please be sure to buy a copy for yourself and all your friends for the Christmas holidays.  Why the gratuitous plug here....Somehow I have to pay for the expensive trip to the MSC for a few "free" knots.

 

(I discussed how much time he needs, and he said it was roughly a day long project to do a few iterations - mostly because it is already good and true and he would just be doing the small things I said).

[Robert Flood]

I have a 1995 missile conversion. Wondering if anyone has had muffler cracks and problems? Any advice would be appreciated.

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[BobAustin]

I have a 1995 missile conversion. Wondering if anyone has had muffler cracks and problems? Any advice would be appreciated.Sent from my iPhone using Tapatalk

Robert the entire exhaust system on my 1995 Missile conversion was replaced in 2012. . Bought from Rocket cost about 5K. Work done by DuGosh Aircraft in Kerrville. Not excessive after 17 years of use. You may not need complete replacement if you have a capable shop that can repair yours.

[Robert Flood]

Bob thank you so much for the reply. I also have a 1995 missile conversion. The exhaust is a constant problem. I'll take your advice and contact rocket thank you. N888df.

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[Robert Flood]

Bob did they give you any warranty or guarantee on their work?

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[philiplane]

No one has mentioned CG yet. 

 

Manufacturers optimize the CG when doing tests. You can find 3-7 knots on most planes by simply moving your CG back to 3/4 to 7/8 of the allowable envelope. All the way forward slows it down, and all the way back slows it down too. Two people, full fuel, and bags means the CG is pretty far forward. 

[BobAustin]

Robert,  I don't recall any warranty discussion but Rocket is a first class outfit and will be worth dealing with.  I expect the replacement to last about 17 more years...longer than I will be flying...