Friday Afternoon Smackdown: Bravo vs. Rocket

[aviatoreb]

If you're far enough LOP over 80% power, detonation likely won't be a problem. Would you rather be 50dF LOP or 50dF ROP at 80% power?

True - but at 80% the Advanced Pilots seminar boys would say to run 200dF ROP to keep safe engine ops.

80% is a pretty high setting though.

[jetdriven]

TAT turbo Bonanzas run at 90% power LOP all day long. 325 CHTs as well.

[aviatoreb]

TAT turbo Bonanzas run at 90% power LOP all day long. 325 CHTs as well.

Yeah - I have read that - stunning. Their engine installs are obviously fundamentally different from mine, in that I would not be able to do that and keep the TiT within the green.

[jetdriven]

They are TN, Eric. So, 29" of MP or less and intercooled air charge. It is the same to that engine as running at sea level NA, but cooler air aloft.

A lot of this talk of not running LOP above 65% is a bunch of hooey. I have ran my Io-360 LOP at 84% power for hours on end.

[AndyFromCB]

You all are probably right, but I'm not going to test the theory in my Bravo. Too many AMUs spent. My airplane was always run 100 ROP TIT and the cylinders /valves looked brand new when we took it apart. If I was running a IO550, I would run LOP too, but with my TIO540, it's not worth the loss of speed.

[aviatoreb]

They are TN, Eric. So, 29" of MP or less and intercooled air charge. It is the same to that engine as running at sea level NA, but cooler air aloft.

A lot of this talk of not running LOP above 65% is a bunch of hooey. I have ran my Io-360 LOP at 84% power for hours on end.

I suspect it is a lot more than simply that it is NA - I can simulate NA by running my MP at 29'' even though take-off power is 38'' and max allowable cruise is 34''. But at 29'' I cannot run at 75% LOP without butting up against the factory limit 1650TiT - and running the turbo that hot makes me uncomfortable so I don't as a cruise setting. I suspect both baffling and the different compression values make those TNIO550s run fundamentally differently from my TSIO520 install. It would be pretty cool to have 85 or 90% of my 305hp actually available for cruise. Wow would that be a fast commute.

[carusoam]

Don't forget the nicely balanced and curved intake runners on the IO 550. It works on Chevys as well. Could probably work on Bravos...

-a-

[aviatoreb]

Don't forget the nicely balanced and curved intake runners on the IO 550. It works on Chevys as well. Could probably work on Bravos...

-a-

And on Rockets?

I don't know anything about what you are talking about - do tell. Is that the missing link?

Then again - it doesn't matter if it would work nicely - it would take an STC, a 337 field approval, act of God and all that to legally install.

[carusoam]

EB,

Balancing the flow of air has been around commercially since the mid 80's on Corvettes. Each intake runner is the same length and diameter.

This allows for the delivery of a uniform shot of air to each cilinder. Overall delivery of identical shots of air to match the balanced shot of fuel.

Act of god will be required...

-a-

[Hank]

If you're going to "simulate" NA operation with your Rocket, limit MP to 29" at sea level, and drop it an inch per 1000'. I get a whopping 20.2" at 10,000 . . . producing a powerful 128 hp . . . using Book values. My MP needle is calibrated in whole inches. My Sea Level chart shows 28.0" at 2700, dropping to 24.0" at 2400 RPM to 23.0" at 2400 RPM to get below 75%.

[aviatoreb]

EB,

Balancing the flow of air has been around commercially since the mid 80's on Corvettes. Each intake runner is the same length and diameter.

This allows for the delivery of a uniform shot of air to each cilinder. Overall delivery of identical shots of air to match the balanced shot of fuel.

Act of god will be required...

-a-

Oh wouldn't it be sweet though. Sometimes I wish I had an experimental and I could just modify as I see fit.

[aviatoreb]

If you're going to "simulate" NA operation with your Rocket, limit MP to 29" at sea level, and drop it an inch per 1000'. I get a whopping 20.2" at 10,000 . . . producing a powerful 128 hp . . . using Book values. My MP needle is calibrated in whole inches. My Sea Level chart shows 28.0" at 2700, dropping to 24.0" at 2400 RPM to 23.0" at 2400 RPM to get below 75%.

True - I meant to say I can simulate TN - turbo normalized - by maintaining 29''MP at all altitudes as would a TN install.

[KSMooniac]

True - I meant to say I can simulate TN - turbo normalized - by maintaining 29''MP at all altitudes as would a TN install.

Actually, that isn't correct because you have low compression pistons so 29" in your plane is like 25" in a normally aspirated high compression engine.

[aviatoreb]

Balancing the flow of air has been around commercially since the mid 80's on Corvettes. Each intake runner is the same length and diameter.

That is really cool - of course it makes sense but I never thought about it. Gami's for balanced fuel flow but then you need to balance the airflow for perfect tuning.

Actually, that isn't correct because you have low compression pistons so 29" in your plane is like 25" in a normally aspirated high compression engine.

Oh - makes sense. I stand corrected.

[carusoam]

On the topic of Acts of God required...

My Ovation is coming up time for an overhaul. Since everything FWF is going out to be improved, I did some homework.

I can replace the NA IO550(g) with TN IO550(g) for a few dollars more (the cost of two turbos and a new exhaust system)

This essentially would be an Acclaim without the Garmin G$MM Avionics.

EVERYTHING is a documented, well proven system, accept for one thing, my serial number begins with a 29 and real Acclaims begin with a 31....?

Real turbocharged engines benefit from low compression ratios, but TN engines continue to run even with major intake leaks.

Notice the (g) tag in both their names... Nearly identical except for the turbos and exhaust...

I was pretty excited about the opportunity to achieve Acclaim like performance at the minimal up charge of additional key hardware.

The discrepancy in SN would cost a mint in FAA documentation...or an act of God.

The next version of the Rocket would use something like the TN IO550(g), and it would be a mean traveling machine!

Back to the drawing board...

Best regards,

-a-

[RJBrown]

I only had my Rocket for about 1000 hour so I never had any engine issues. Another Rocket distributor, Irv Fehr, got over 2000 hour out of his without cylinder work.

Here is an excerpt from the for sale ad on N305PF:Equipment Specifications Year 1980 Manufacturer MOONEY Model M20K 305 ROCKET Price US $175,000 Location Melba, Idaho Condition USED Serial Number 25-0486 Registration Number N305PF Total Time 7000 Hours Overhaul 30 SMOH Flight Rules IFR Number Of Seats 4 General Information The first rocket, my personal aircraft, well taken care of garmin530 Detailed Description 305PF has won the air race from Denver to Oshkosh Airframe: Has one piece belly with special runners. Has three wheels up landings, on the special runners, with no damage to the interior of the fuselage.Engine Specs: A Continental TSIO 520 NB. Rebuilt at 2000 hours after the conversion with no tops in between.40 hrs or so since rebuldProp(s):

The Rocket uses the complete power package as certified in the Cessna 340. That is where the full feathering prop came from. One very large turbo, large enough to meet certification requirements for single engine cockpit pressurization at service ceiling. Way over kill for our needs. They outlast the engine, unlike the little one on the 231 or the 2 little ones on the Acclaim . A Rocket has a motor mount that attaches to the fuselage at 8 points instead of 4 like the Bravo. The cowl flap setup is one reason the engines last, they never run hot unless you screw up bad. Full power climb from 6000 to 26000 never a temp issue. Rockets usually have about 1000# useful load. The gross weight is limited by the landing gear not the climb rate. 400# over gross will perform about the same as a Bravo. Hot? High? Humid? who cares! At gross from Leadville in the summer climbs better than my current J 600# under at sea level.

The Rocket is still the ultimate Mooney. They all share the same wing this one has the most HP. The others just weigh more.

[carusoam]

RJ,

That's compelling!

Who wouldn't want that?

-a-

[KSMooniac]

Is Irv still around/alive/in business? I used to see his many ads but haven't in quite a while. I never met him, but he sure was a Rocket fan!

[RJBrown]

Is Irv still around/alive/in business? I used to see his many ads but haven't in quite a while. I never met him, but he sure was a Rocket fan!

I believe he passed or at least retired. He was a Corsair pilot in WW11 and was getting quite old last I saw him. We met at Rocket in 95 and worked Fun and Sun and Oshkosh together in 96 he did help sell my Rocket in 2003. 4 years ago when I was looking to buy I contacted him and he did not remember me. I have not been able to contact him since.

[fantom]

I'm fairly certain ol' Irv has gone to that big hanger in the sky...RIP.

[KSMooniac]

I bet so... if he was fighting age in WWII, then he would be very old today. He seemed to have a half-dozen Rockets at any one time.

[aviatoreb]

I bet so... if he was fighting age in WWII, then he would be very old today. He seemed to have a half-dozen Rockets at any one time.

Holy Moly?! Really? He had his own Rocket fighter squadron! I wish I met him.

[rocketman]

I'll never forget Irv. Always pleasant and smiling and a big fan of the Rocket. I first met him at a MAPA homecoming maybe around 1989 and he asked me if I was interested in flying in the Rocket. Of course I said so I met him the next day at the airport and he let me in the front seat. Well, little did I realize there were two huge people in the back seats including someone I would estimate weighed nearly 375 pounds, with another passenge in the reat at over 200 pounds. Irv was maybe 175 pounds and myself then (before I got into this crazy sport of marathon running) was maybe 200 pounds. So us passengers wighed a little under 1000 pounds and I knew even in my budding years that it was way over gross. I do not remember the amount of fuel on board. I told Irv I was not going to go but in is usual smiling answer he said get in. And so I went. And darn if the plane flew fantastic. Not a hiccup or anything. Landing was great too. What this tells me is that the Rocket can fly anything you can put into it (not that I would ever go over the legal limits of the plane (3200 pounds) but its nice to know that it has great reserves (icing?)!.. I am sure that was the test flight of loading a Rocket.

And BTW, the previous owner of my Rocket once had my plane up to 31,000 feet and still climbing. The plane can do amazing stuff, a one of a kind bird that will never be duplicated again!

And another thing, Rocket Engineering is still in business in Spokane Washington modifying other planes and has everything one will need for the Rocket and Missle for a long time. Way to go Darwin Conrad!

[fantom]

Irv also had a habit of advertising Rockets for sale that actually weren't. All he needed was a photo or two and a little information on the plane. Instead of starting with an owner interested in selling, he'd start with a customer interested in buying. Quite a character...

[Mcstealth]

(Still ride a Honda VFR, hard, with but small "chicken strips.")

 

Great bike! What year though all the years are good!? Not sure what chicken strips are?