M20J Takeoff Performance at 8,000+ DA?

[Ragsf15e]

7 hours ago, Shadrach said:

That may be true.  Even so, the K model is not really the take off champ that people would have you believe.  Perhaps I am misreading the convoluted graph.

Nope.  Even with ~100% of its hp available (but maybe a little less due to lost propeller efficiency), a ~200 hp airplane fully loaded isn’t going to takeoff really quick.  I think it’s really weight vs thrust on takeoff, and thats probably not where a k shines.  Cruise at 17,000’ makes it look awesome though!

[Shadrach]

1 hour ago, Ragsf15e said:

Nope.  Even with ~100% of its hp available (but maybe a little less due to lost propeller efficiency), a ~200 hp airplane fully loaded isn’t going to takeoff really quick.  I think it’s really weight vs thrust on takeoff, and thats probably not where a k shines.  Cruise at 17,000’ makes it look awesome though!

This has always been my view of where they shine. I looked at some real world W&B numbers on line. Most are 300 to 400lbs heavier than my F model. According to my POH the engine will make 83% hp at 7500’ and 77% at 10,000’ on a standard day.  It would interesting to see the real world delta in runway performance at altitude. 

[oisiaa]

Higher DA also requires higher TAS for the same IAS (rotation/climb speed). In other words, that lower horsepower must accelerate the plane to a higher actual velocity. 

[Fly Boomer]

9 hours ago, Shadrach said:

Even so, the K model is not really the take off champ that people would have you believe.

Turbo gets you all the power you need, but the two airfoils still feel the effects of the altitude.

[Shadrach]

44 minutes ago, Fly Boomer said:

Turbo gets you all the power you need, but the two airfoils still feel the effects of the altitude.

Using my F as an example. At 8,000’ the turbo is pulling an airframe that is 20-25% heavier with 18-22% more horsepower. That spread gets better as the DA goes up. That being said I think the takeoff advantages at DAs below 10K are probably overstated. 

[larryb]

Don’t forget that at high DA you have to go faster to achieve your takeoff IAS. 10% or so depending. So even with a turbo at full sea level power it will take longer to accelerate to what is actually higher ground speed.

[Fly Boomer]

18 hours ago, larryb said:

Don’t forget that at high DA you have to go faster to achieve your takeoff IAS. 10% or so depending. So even with a turbo at full sea level power it will take longer to accelerate to what is actually higher ground speed.

That's what I meant by "two airfoils" above -- wing and prop don't gain anything from turbo.

[oisiaa]

36 minutes ago, Fly Boomer said:

That's what I meant by "two airfoils" above -- wing and prop don't gain anything from turbo.

Well...the prop has more power turning it so it takes a bigger bite. 

[mhrivnak]

As others have indicated, summers see a lot of convective turbulence out there, which is made worse by the hot desert floor being around 6000ft. July at 9500ft is miserable after 10am. I love my J, but if I was flying through there regularly in the summer, I'd want a turbo and O2 to get well above the turbulence.

When calculating climb rates based on 310ft/nm, just keep in mind that 90kts indicated at altitude could be more like 105kts TAS. With no headwind, that comes to a 542.5 fpm climb rate. The J performance charts suggest that should be achievable. But it's worth keeping a close eye on it, especially if you end up climbing with a tailwind.

On the other hand, if you find yourself in a J looking for a stop in that area on a hot day with a heavy load, just stop at ABQ where you'll be at "only" 5355ft MSL and have almost 14k ft of runway to work with.

[Z W]

The takeoff roll in the K is in fact pretty long at any altitude when heavy.  Of the Mooneys, I believe it may be one of the worst short-field performers at 2900lbs max gross and 210-220 HP.  But once it gets to speed, it climbs 500 FPM+ regardless of altitude or temperature.  And 3,000 feet of runway is plenty which gets you most places.

However, taking off from mountain airports is not the difficult part of mountain flying.  Most mountain airports have very long runways for just this reason.  Few non-turbo models will struggle taking off from a 9,000 foot long runway at any altitude.  You might read the POH charts and think your NA plane can make the trip, and it probably can.

However, after takeoff is when the challenge starts.  You'll be pulling it up off the runway, having to accelerate in ground effect, staring at your ASI to verify you're at Vy, and glancing over at your VSI to verify you're actually climbing (you may not be able to tell by looking out the window).  You'll need to have planned your departure route to be towards declining terrain, for safety, which may or may not be your intended direction of flight.  You probably need to be at least 200 lbs under gross.  You may need to fly on the windward side of the pass to avoid downdraft and gain updraft to be able to climb at all.  You have to be careful not to enter a blind canyon that you may not be able to climb out of, if the terrain climbs faster than your plane is capable of that day.

The Colorado Pilots' Mountain Flying course teaches all this stuff and it's really good. 

The turbo makes it all much easier.  Just takeoff and go with some basic weather and flight planning.  A NA Mooney does not do it better because it's a little lighter.

[oisiaa]

4 hours ago, Z W said:

The takeoff roll in the K is in fact pretty long at any altitude when heavy.  Of the Mooneys, I believe it may be one of the worst short-field performers at 2900lbs max gross and 210-220 HP.  But once it gets to speed, it climbs 500 FPM+ regardless of altitude or temperature.  And 3,000 feet of runway is plenty which gets you most places.

However, taking off from mountain airports is not the difficult part of mountain flying.  Most mountain airports have very long runways for just this reason.  Few non-turbo models will struggle taking off from a 9,000 foot long runway at any altitude.  You might read the POH charts and think your NA plane can make the trip, and it probably can.

However, after takeoff is when the challenge starts.  You'll be pulling it up off the runway, having to accelerate in ground effect, staring at your ASI to verify you're at Vy, and glancing over at your VSI to verify you're actually climbing (you may not be able to tell by looking out the window).  You'll need to have planned your departure route to be towards declining terrain, for safety, which may or may not be your intended direction of flight.  You probably need to be at least 200 lbs under gross.  You may need to fly on the windward side of the pass to avoid downdraft and gain updraft to be able to climb at all.  You have to be careful not to enter a blind canyon that you may not be able to climb out of, if the terrain climbs faster than your plane is capable of that day.

The Colorado Pilots' Mountain Flying course teaches all this stuff and it's really good. 

The turbo makes it all much easier.  Just takeoff and go with some basic weather and flight planning.  A NA Mooney does not do it better because it's a little lighter.

Very valuable context. I'm used to flying a hotrod that can sustain 8,000-10,000 ft/min at normal weights below 10,000 feet and >2,000fpm at at max gross (all engines operating...cut it in half with 1/4 engines out). I have a grand total of 20 hours in something under 1,100 horsepower....I have a lot to learn.

[Shadrach]

On 11/5/2023 at 6:42 AM, Z W said:

The takeoff roll in the K is in fact pretty long at any altitude when heavy.  Of the Mooneys, I believe it may be one of the worst short-field performers at 2900lbs max gross and 210-220 HP.  But once it gets to speed, it climbs 500 FPM+ regardless of altitude or temperature.  And 3,000 feet of runway is plenty which gets you most places.

However, taking off from mountain airports is not the difficult part of mountain flying.  Most mountain airports have very long runways for just this reason.  Few non-turbo models will struggle taking off from a 9,000 foot long runway at any altitude.  You might read the POH charts and think your NA plane can make the trip, and it probably can.

However, after takeoff is when the challenge starts.  You'll be pulling it up off the runway, having to accelerate in ground effect, staring at your ASI to verify you're at Vy, and glancing over at your VSI to verify you're actually climbing (you may not be able to tell by looking out the window).  You'll need to have planned your departure route to be towards declining terrain, for safety, which may or may not be your intended direction of flight.  You probably need to be at least 200 lbs under gross.  You may need to fly on the windward side of the pass to avoid downdraft and gain updraft to be able to climb at all.  You have to be careful not to enter a blind canyon that you may not be able to climb out of, if the terrain climbs faster than your plane is capable of that day.

The Colorado Pilots' Mountain Flying course teaches all this stuff and it's really good. 

The turbo makes it all much easier.  Just takeoff and go with some basic weather and flight planning.  A NA Mooney does not do it better because it's a little lighter.

The honest assessment is indeed appreciated. I have never flown a K model.  Last spring, I was admiring one that was just ahead of me in the queue to take off from my home drome.  I took off about minute after him in the same direction. I thought I was imagining it as he got larger in the windshield, then tower called notifying me that they had gotten a collision alert and to ask me if I still had the traffic in sight. I was above him and overtaking on the right when he turned south at the VOR just 5.5nm from the the departure threshold.  I was initially surprised that my stock, 56 year old Mooney would keep up with, much less overtake but after checking his flight track and doing a little research on the flight profile of other Ks I understood. It's a heavier aircraft with ostensibly the same HP but a more temperamental powerplant necessitating conservative operation.  It's a specialized aircraft. It climbs and takes off consistently but it is meant for high altitude, long distance XCs where no other 4 plc single will go as far, as fast on so little gas. What it is not is a low altitude hot rod nor a short field take off champ.

[1980Mooney]

2 hours ago, Shadrach said:

The honest assessment is indeed appreciated. I have never flown a K model.  Last spring, I was admiring one that was just ahead of me in the queue to take off from my home drome.  I took off about minute after him in the same direction. I thought I was imagining it as he got larger in the windshield, then tower called notifying me that they had gotten a collision alert and to ask me if I still had the traffic in sight. I was above him and overtaking on the right when he turned south at the VOR just 5.5nm from the the departure threshold.  I was initially surprised that my stock, 56 year old Mooney would keep up with, much less overtake but after checking his flight track and doing a little research on the flight profile of other Ks I understood. It's a heavier aircraft with ostensibly the same HP but a more temperamental powerplant necessitating conservative operation.  It's a specialized aircraft. It climbs and takes off consistently but it is meant for high altitude, long distance XCs where no other 4 plc single will go as far, as fast on so little gas. What it is not is a low altitude hot rod nor a short field take off champ.

Don’t forget - the Lycoming IO-360 compression ratio is 8.7 vs 7.5 for the Continental TSIO-360. That’s 16% greater compression pressure immediately and greater peak combustion pressure during initial acceleration. Until the turbo over boosts about 16% compared to the Lycoming manifold pressure, the Continental is playing “catch-up”. 

[Shadrach]

4 minutes ago, 1980Mooney said:

Don’t forget - the Lycoming IO-360 compression ratio is 8.7 vs 7.5 for the Continental TSIO-360. That’s 16% greater compression pressure immediately and greater peak combustion pressure during initial acceleration. Until the turbo over boosts about 16% compared to the Lycoming manifold pressure, the Continental is playing “catch-up”. 

I take all of that into consideration. There is a lot more to manage.  If I was looking for a "Mountain" Mooney that would handle shorter strips, I would be looking for the lightest TN'd M20E or M20F I could find. 

>1700lb empty weight

Excellent engine cooling

High Comp Engine

 

 

[A64Pilot]

4 hours ago, 1980Mooney said:

Don’t forget - the Lycoming IO-360 compression ratio is 8.7 vs 7.5 for the Continental TSIO-360. That’s 16% greater compression pressure immediately and greater peak combustion pressure during initial acceleration. Until the turbo over boosts about 16% compared to the Lycoming manifold pressure, the Continental is playing “catch-up”. 

I don’t have any turbo experience either, just Supercharger, but the turbo ought to be on boost prior to brake release I’d think, if not I don’t know why not?

I know in turbines I set torque prior to brake release if it’s a short field, surely a turbo can do the same?

[Pinecone]

Ona short field, I would run up the power.  Most takeoffs are rolling and bring the power up smoothly, the turbo kicks in a bit down the runway.

As for catching a K in the climb, you don't know how the other pilot was running their engine.  They may be one of the reduce power after take off crowd.  I run all three knobs full forward until I level off.

[Z W]

You also don't know how many hours of fuel the K had on board or what weight it was flying at.  Many have extended range tanks that hold 105+ gallons.

My standard operating procedure is to fill the tanks to max gross for the anticipated payload for the flight, so most takeoffs are heavy.  Most often I have 6+ hours of endurance.  I like having extra gas in the tanks.  A J model might pass me taking off and climbing out 300+ lbs lighter at low altitude, but it wouldn't be able to go as far. And somewhere around 10,000 feet MSL I'd expect the K to pass it right back.

I would bet that at similar weights they have very similar performance down low.  Higher compression in the J cylinders would likely be offset by extra manifold pressure in the K, unless it was dialed back like Pinecone points out.  When I do fly solo and half tanks (still 3+ hours of endurance) the plane jumps off the runway and climbs very well.

[1980Mooney]

23 hours ago, Shadrach said:

I take all of that into consideration. There is a lot more to manage.  If I was looking for a "Mountain" Mooney that would handle shorter strips, I would be looking for the lightest TN'd M20E or M20F I could find. 

>1700lb empty weight

Excellent engine cooling

High Comp Engine

Another reason, rarely discussed here, why that makes great sense - reduced wing loading.  Mooney hangar/shop talk is usually all about "power loading" like here.  Generally, about how to get more power - like with a turbo.

But every Mooney since 1961 flies on the same wing.  Steady flight/state lift decreases about 2-3% per thousand feet.  Depending on the temperature at the 8,000 ft DA airport, you will have lost about 20% of your wing lift at takeoff as compared to what you are accustomed to at sea-level. 

How do we compensate for loss of lift - especially on take-off?

• Greater speed ( get more power loading and/or longer runway).
• Greater AOA - too much and we stall
• Reduce Wing Loading
  • Stay well below MGW
    • Don't fill seats
    • Don't fill tanks

But MGW is just a number on the same wing for all models.  Just like the "FAA average passenger weight" has risen since 1961, our Mooney's have also gotten "fatter".  As @Shadrach recommends, a TN'ed M20E at 2,575 lbs. or a TN'ed M20F at 2,740 lbs. will stack up well compared to a 3,380 lb Acclaim on high DA takeoff.  Although the power loading is less, the wing loading is also less.  

 

[Shadrach]

9 hours ago, 1980Mooney said:

Another reason, rarely discussed here, why that makes great sense - reduced wing loading.  Mooney hangar/shop talk is usually all about "power loading" like here.  Generally, about how to get more power - like with a turbo.

But every Mooney since 1961 flies on the same wing.  Steady flight/state lift decreases about 2-3% per thousand feet.  Depending on the temperature at the 8,000 ft DA airport, you will have lost about 20% of your wing lift at takeoff as compared to what you are accustomed to at sea-level. 

How do we compensate for loss of lift - especially on take-off?

• Greater speed ( get more power loading and/or longer runway).
• Greater AOA - too much and we stall
• Reduce Wing Loading
  • Stay well below MGW
    • Don't fill seats
    • Don't fill tanks

But MGW is just a number on the same wing for all models.  Just like the "FAA average passenger weight" has risen since 1961, our Mooney's have also gotten "fatter".  As @Shadrach recommends, a TN'ed M20E at 2,575 lbs. or a TN'ed M20F at 2,740 lbs. will stack up well compared to a 3,380 lb Acclaim on high DA takeoff.  Although the power loading is less, the wing loading is also less.  

 

I would highly recommend anyone in the market for Mooney at least get some time in a light weight vintage airframe. Just for the sake of comparison. It feels different.  My plane is far from the lightest (1680lbs) of the breed. Nevertheless, I regularly fly at operating weights ~2100lbs (me+3hrs+reserves). They are truly in their own class of 4 cyl, 4plc, singles in terms of speed, climb and runway performance. I think it is a much more forgiving airframe with a lightly loaded wing. The only challenge is getting new pilots to slow to 1.2x before the threshold.

[dzeleski]

Im kinda late to this party but being on the east coast this was never even a concern until I flew across the country in July this year. The J will do it, its not happy about it, and its not a comfortable place to be on a regular basis in my opinion. The book numbers always lined up pretty close to what I actually got in real life but I made sure I was 150-200lbs under gross and I tried to be on the ground before 12pm every day.

I took off from Centennial, CO with DAs around 7-9k, the take off roll was easily double what I was used to at sea level. Similar story in Page, AZ and St. George, UT. Getting used to feeling like you are doing 100mph over the ground and it doesnt want to fly is very strange to deal with for the first time but you get used to it after a few take offs and landings.

Doing that a few times a year is one thing, but if I lived in these locations there is absolutely no chance I would still own my J. It would be put up for sale and I would get into a 6 cylinder or a turbo 4 cylinder immediately. Climbing out at 200-400fpm with such a shallow climb gradient is not a comfortable feeling, im sure some of you will laugh at that since this is just normal for you but Im just personally not ok with it. Its just way too marginal for me and I was easily able to see how so many people kill themselves in these situations with just a touch of a mistake somewhere.

Edited November 7, 2023 by dzeleski