Mooney Aircraft Performance

[JohnB]

I have an M20M/Bravo, and these are some typical numbers for my bird.

 

10,000 ft / 185 kts TAS / 18 gph / @ 29" MP / 2400rpm / ~65% HP.

 

Higher altitude get me much faster with the same power settings and fuel burn, I only go 10k or below on short trips, or if winds or furry passengers limit my climbing.

 

 

 

JB

[BorealOne]

Robert,

With the O3, you have 2700rpm available in the quiver...

And a (at least one?) recommended cruise power setting of 2550?

Are you using 2550 or avoiding it for any reason?

Speed vs. Noise vs. Efficiency...

Best regards,

-a-

I'm getting similar numbers to Robert at those settings, although I typically dial down to 2400 rpm for burns in the 14.8 range at 176 tas. Little quieter, little less fuel burn and little difference in time enroute. I'm hoping that the Continental recommendations for lower cruise rpm settings will payoff in longer engine life, but we'll see what happens. Only 300 hours on the new 550 with the 310 stc so we'll see what happens.

Sent from my iPhone using Tapatalk

[Tx_Aggie]

On 9/21/2014 at 11:10 PM, Cruiser said:

this will give you the first two (most important) values.

http://mooneyspace.com/files/file/16-mooney-model-altitude-vs-speed/

This is an interesting file, are the turbo numbers = or great than 75% power? The graph seems to indicate the K rocket is faster than acclaim and bravo until beyond 19,000’. Also the K rocket has a true airspeed of ~203 ktas at 9,000’ - is this correct?

Edited January 16, 2023 by Tx_Aggie

[1980Mooney]

2 hours ago, Tx_Aggie said:

This is an interesting file, are the turbo numbers = or great than 75% power? The graph seems to indicate the K rocket is faster than acclaim and bravo until beyond 19,000’. Also the K rocket has a true airspeed of ~203 ktas at 9,000’ - is this correct?

The Rocket numbers do not represent reality.  Read the past posts.  Most talk about seeing 195-205 kts at 16,000 ft.  That puts the Rocket right between the Bravo and Acclaims.  Think about it - it is the same wing, basically same plane, similar power - you would expect it to be in the pack.  It is not as refined as the Acclaim S.  Frankly all the numbers are exaggerated.  And they don't show weights or air temperatures, power settings or fuel burn - it is complete apples to oranges.

 

Edited January 16, 2023 by 1980Mooney

[exM20K]

10 hours ago, 1980Mooney said:

The Rocket numbers do not represent reality.  Read the past posts.  Most talk about seeing 195-205 kts at 16,000 ft.  That puts the

Ditto the acclaim.  I do know one guy who flies ROP lat 21+ GPH to get very high TAS numbers, but most don’t. There are two major differences with respect to performance vs the acclaim for both the Rocket and Bravo.

1. Acclaim cowling is cleaner than either.  The cowling is optimized not to need cowl flaps and is a much more modern design, and the Type S changes are meaningful.
2. It’s my understanding that Bravo’s will fly LOP. All Acclaims will very happily.  Not sure about TSIO520NB lop.
3. Vs the long body planes, the mid body must generate more downforce to balance the heavy engine, which creates more drag.

Speed reports without corresponding fuel flows are meaningless.  My plane can be a 210 KTAS 16.5 GPH at 16-17,000, or it can be 220 KTAS at 21 GPH. I don’t find that juice worth the squeeze.

TKS costs 8-10 KTAS. I do find that juice worth the squeeze. 
i imagine being able to sustain 12-1500 FPM climbs (310 HP) does more to shorten a trip than does a 5-10% cruise difference.
 

-dan

[Austintatious]

I can chime in with rocket numbers from experience with 2 aircraft.  The only difference aerodynamically is that one does not have a step and it has a smaller towel bar type antenna... The other has a step and a blade antenna.  Both have smooth bellies.

What Dan says above is the most important takeaway for the rocket... The juice being worth the squeeze. 

I typically fly 30/22 at 17.5 GPH... at 10k I see around 185 KTAS and at FL210 I see about 210 KTAS at the same settings.  You can basically Rule of thumb ballpark an extra 2 knots per 1000 feet.  

You can put the power up higher, but you absolutely trash your economy.  You will easily burn another 3-5 gallons for 10 more knots.  I have only seen this make sense in really big headwinds that couldn't be avoided...  and it didn't save any gas but the time was shorter with the same burn or close to it anyway ....  so why not.

That all being said, I love the rocket.  The power is great for climbing, taking off at high elevations or at max gross where I still see 1000FPM at about 130-40 KIAS.

Then you pull it back and still go fast pretty economically.  In a tailwind, you can get silly.  Pull it way back to 26/22 and about 14 GPH and still true 165 (10k) or 185 (20k).  When you have a 30+ knot push you would be foolish not to.  When I am really stretching it, I will descend at 19/22 at about 10 GPH 500 FPM... and If I am up at FL210  that could be 40 min of descending.

[carusoam]

Climb rate of 310hp in a Mooney IS worth the squeeze….   

Especially if you want to climb over a nearby Class Bravo…

Best regards,

-a-

[Austintatious]

Just now, carusoam said:

Climb rate of 310hp in a Mooney IS worth the squeeze….   

Especially if you want to climb over a nearby Class Bravo…

Best regards,

-a-

Yea I mean WRT cruise speed...

I leave out of Galveston a lot and I rocket (pun intended) right up to 10.5 and go straight over all the Houston mess.  So believe me I know!

[jlunseth]

You have to be really careful about using numbers in published articles. For most part, those use marketing numbers. Yes, the numbers are probably achievable under some set of circumstances, but not if you don't want to change engines often. For example, the factory 231, which had a fixed wastegate and no intercooler, was so named because it would make 231 mph top speed. Well that's 200 kts, and what they had to do to achieve a speed like that is go up to max altitude for the aircraft where it would get best TAS and crank the engine to full power. I don't fly the factory version but I can see the numbers on my JPI that it would produce. If they did that work in Texas they would have to have waited until the dead middle of winter with very cold temps for TX in order to be able to climb to max altitude at all. Under summer conditions you will achieve Compressor Discharge Temp redline at somewhere around 15-17k and you will not be able to climb any higher. Even if you could get higher you pass critical altitude in the fixed wastegate version at around 15k and I can tell you from experience that once you do that and the power starts to fall off with further altitude the climb rate is very anemic, so whoever did the 231 top speed flight test would have to have been very patient, it would have taken maybe an hour to get up there. The Merlyn and intercooled engines can do better than that. Critical altitude is around 22.5k and CDT is not relevant. Pretty much every statement I have seen of aircraft speed fails to take into account all the variables that affect it on a given day such as OAT.

All that said, my favorite cruise setting for 10k would be 34"MP/2450 RPM/11.1 GPH and at that altitude and setting I would get around 160 kts and on some days 165. After many hours of flying you discover that differences in airspeed, unless they are orders of magnitude, tend to make a difference in mere minutes in the length of a flight.

You also have to account for the fact that prevailing winds at high altitudes are west to east. It rarely pays to go high if you are going west. On the other hand, when you come home, even in a lowly 231 you will routinely see cruise speeds in the 200+ kts range, and in the winter when the winds are very strong up high I have seen 300.

[T. Peterson]

On 9/21/2014 at 5:24 PM, JohnD said:

 

-a-

 

I will be flying between Dallas and Houston 70 - 80% of the time but I will definitely do some longer trips. I feel the Ovation is perfect for what I want but would consider the TC'd aircraft if the price is right. The reason I listed the TC'd aircraft is because I am looking more for speed and there are a lot more of them fore sale.  Plus there are not as many ovations to choose from in my price range of $150,000 - $200,000. I'm not really avoiding the O2 levels. I just don't think it is very beneficial based on my trip length. Thank you for your input.

 

JD

I enjoy my K, but most of my trips are over 350 miles. I fly at 11 and 12000. I burn 13 gallons an hour to get 165 kts true. Most do much better but I don’t have Gami injectors or intercooler. I find there is a big difference even within the same model because some guys have the technical savvy to really dial in their engines. Unfortunately, I don’t.

One fellow here gets the same speed as do I while sipping fuel at 10 gallons per hour or less. He is running LOP and up to 34 inches of MP. And his engine is over TBO! That’s dialed in!! My engine starts to melt just thinking about those numbers! If I run anything over 30 MP, I have to cool with fuel. In the winter the cylinders stay cooler than TIT, but in the summer I have to closely monitor both. 
That’s just my experience and my experience is based on less than a year of Mooney ownership.

[T. Peterson]

5 hours ago, jlunseth said:

You have to be really careful about using numbers in published articles. For most part, those use marketing numbers. Yes, the numbers are probably achievable under some set of circumstances, but not if you don't want to change engines often. For example, the factory 231, which had a fixed wastegate and no intercooler, was so named because it would make 231 mph top speed. Well that's 200 kts, and what they had to do to achieve a speed like that is go up to max altitude for the aircraft where it would get best TAS and crank the engine to full power. I don't fly the factory version but I can see the numbers on my JPI that it would produce. If they did that work in Texas they would have to have waited until the dead middle of winter with very cold temps for TX in order to be able to climb to max altitude at all. Under summer conditions you will achieve Compressor Discharge Temp redline at somewhere around 15-17k and you will not be able to climb any higher. Even if you could get higher you pass critical altitude in the fixed wastegate version at around 15k and I can tell you from experience that once you do that and the power starts to fall off with further altitude the climb rate is very anemic, so whoever did the 231 top speed flight test would have to have been very patient, it would have taken maybe an hour to get up there. The Merlyn and intercooled engines can do better than that. Critical altitude is around 22.5k and CDT is not relevant. Pretty much every statement I have seen of aircraft speed fails to take into account all the variables that affect it on a given day such as OAT.

All that said, my favorite cruise setting for 10k would be 34"MP/2450 RPM/11.1 GPH and at that altitude and setting I would get around 160 kts and on some days 165. After many hours of flying you discover that differences in airspeed, unless they are orders of magnitude, tend to make a difference in mere minutes in the length of a flight.

You also have to account for the fact that prevailing winds at high altitudes are west to east. It rarely pays to go high if you are going west. On the other hand, when you come home, even in a lowly 231 you will routinely see cruise speeds in the 200+ kts range, and in the winter when the winds are very strong up high I have seen 300.

John D,

This is the gentleman to whom I was referring. What he just wrote is excellent. Never mind my dribble!

T.Peterson