M20J Takeoff Performance at 8,000+ DA?

[oisiaa]

Any perspectives on how J models perform on takeoff at 8,000+ DA? My planned mission will likely see me transiting Gallup, NM (KGUP) or Santa Fe, NM (KSAF) fairly regularly since it's a nice 3 hour mid-point between two primary destinations. Today KGUP's DA is 8,500' and KSAF is 8,100'. 

How's climb performance? The highest SID out of KSAF is 310'/NM to 8,200' (field elevation is ~6,400').

My home field's DA is currently 5,300' so that will be a factor too.

What I'm really trying to do here is pin down J vs K for how I plan on flying the plane. I think it's pretty obvious that a turbo will make a big difference in this case.

All comments appreciated. Thanks!

[Fly Boomer]

12 minutes ago, oisiaa said:

Any perspectives on how J models perform on takeoff at 8,000+ DA? My planned mission will likely see me transiting Gallup, NM (KGUP) or Santa Fe, NM (KSAF) fairly regularly since it's a nice 3 hour mid-point between two primary destinations. Today KGUP's DA is 8,500' and KSAF is 8,100'. 

How's climb performance? The highest SID out of KSAF is 310'/NM to 8,200' (field elevation is ~6,400').

My home field's DA is currently 5,300' so that will be a factor too.

What I'm really trying to do here is pin down J vs K for how I plan on flying the plane. I think it's pretty obvious that a turbo will make a big difference in this case.

All comments appreciated. Thanks!

Get the turbo.  Quiz the person who looks at the airplane for you.  Be circumspect.  If they harbor a deep-seated belief that turbochargers will kill all your cylinders every 500 hours, or that your engine will blow up on first takeoff, or that turbocharged engines cost twice as much to maintain, then you need to find someone who has experience with turbochargers.

[0TreeLemur]

Took off from Los Alamos, NM (LAM) twice a couple of weekends ago in our two-bladed J with a DA over 8k and no wind.  Both of those takeoffs were 100-150 lb below gross weight. My observations:

1) acceleration on the ground at that DA is not impressive.  It takes quite a while to get up to flying speed.  We had 6000 ft of runway and I reckon we were off the ground in less than 2000 ft.

2) after liftoff, I leveled out to increase to 95 KIAS.  After that climb rate was about 400 ft/min. 

3) all departures from LAM are to the east, which has the runway 1.5% sloping downhill.

Took off from SAF one mid-morning in July with gusty winds and turbulence loaded with two adults and full tanks.   DA about 8,500 IIRC.   Climb performance was muddling in the turbulence.  It never created a situation, just took a while to get up to 10,500.  A J can handle it just fine.

 

[oisiaa]

1 minute ago, 0TreeLemur said:

Took off from SAF one mid-morning in July with gusty winds and turbulence loaded with two adults and full tanks.   DA about 8,500 IIRC.   Climb performance was muddling in the turbulence.  It never created a situation, just took a while to get up to 10,500.  A J can handle it just fine.

Sounds okay/safe for day VMC, but not for an IFR departure. I'll have to pull some performance charts to run the numbers to see what the book says. 

[N201MKTurbo]

It is in your POH.

I flew my first 3000 hours in Mooneys out of Denver, servicing towns in the mountains. Never had a problem. 
 

I’ve flown a NA M20F out of KTEX at gross without issue.

Just check your takeoff charts to make sure you have enough runway. 

[KSMooniac]

I've taken my J into and over the Rockies and it does OK, but I only venture in there in good weather/low-ish wind days.  I've gone into Leadville, IIRC the density altitude was ~13k when I took off solo, with maybe 2/3 or 3/4 fuel and some cargo... ground roll felt like an eternity, perhaps 2500 or 3000' and climb rate was <500 FPM, but the terrain is gentle so I could climb out without excitement before proceeding on course to the east.  Other airports in the Rockies are more challenging IMO even though they're lower elevation.  Sante Fe and Alburquerque are much less dramatic too.  

If your planned regular trips are longish (>500 NM) and involve high altitude stops, I think you would be wise to go for a K instead. You'll find very few that have a turbo would want to go back.  I want to add a turbo normalizer to my J and have the best of both worlds. 

[oisiaa]

6 minutes ago, KSMooniac said:

I've taken my J into and over the Rockies and it does OK, but I only venture in there in good weather/low-ish wind days.  I've gone into Leadville, IIRC the density altitude was ~13k when I took off solo, with maybe 2/3 or 3/4 fuel and some cargo... ground roll felt like an eternity, perhaps 2500 or 3000' and climb rate was <500 FPM, but the terrain is gentle so I could climb out without excitement before proceeding on course to the east.  Other airports in the Rockies are more challenging IMO even though they're lower elevation.  Sante Fe and Alburquerque are much less dramatic too.  

If your planned regular trips are longish (>500 NM) and involve high altitude stops, I think you would be wise to go for a K instead. You'll find very few that have a turbo would want to go back.  I want to add a turbo normalizer to my J and have the best of both worlds. 

Thanks for the datapoint. J sounds marginal, but doable. 

Hopefully someone with firsthand knowledge of a K will be able to provide inputs. 

[EricJ]

In the southwest and across the middle-west of the country the summer typically involves a lot of high-DA flying if you go very many places at all.   8800 ft is not at all unusual and 10k or higher isn't unheard of.    Full-throttle leans for takeoff before brake release are SOP in these conditions.   FWIW, there's a flight school at Flagstaff (7000 ft field elev) that instructs all summer in their C172s and they get DA over 10k feet in the summer.    They have a sign near the runup area that'll show the DA in real time sometimes.   One of the old grizzled instructors there says they just lean for takeoff and plan for slow climbs.

I've not had any trouble getting off the ground in high DA, even near gross weight, but climb definitely slows down.   Most airports that experience high-DA have very long runways, so once off the ground pulling the gear up and accelerating in ground effect or near it gives the best chance of getting to desired climb speed quickly or accelerating with some margin.

This summer I had to circle a little over an airport in UT to get enough altitude to clear a ridgeline in our departure direction, and that was with two adult males, full tanks, and a fair amount of luggage/crap.   That's unusual for me, but can happen.   It's one of the few times I wished I had a turbo, but it was very doable without.

[0TreeLemur]

3 hours ago, oisiaa said:

Thanks for the datapoint. J sounds marginal, but doable. 

Hopefully someone with firsthand knowledge of a K will be able to provide inputs. 

I don't think of a J is marginal for high DA ops.  It's a J at 8,000+ ft.  It's not going to perform like it does closer to SL or an airplane with a turbo.  Most high altitude runways are 6,000 ft long or more.  It never felt unsafe.   It still flies if it's going fast enough.  It has the same limitations on the gross weight regardless of DA.  Training and practice make high DA ops safe- not Turbo vs. non-Turbo.

I've flown C210's at high DA.   Rockin' it, dog.   Practically jumps off the ground at gross weight-  no problemo.  But it burns close to 30 gph in the climb and 18-19 in cruise.  All aircraft are tradeoffs.

[0TreeLemur]

On 10/25/2023 at 5:35 PM, oisiaa said:

Sounds okay/safe for day VMC, but not for an IFR departure. I'll have to pull some performance charts to run the numbers to see what the book says. 

In the summer when DA is super high, Santa Fe is VFR >95% of the time.  The mountain wave turbulence in that area from noon through late afternoon is ridiculous sometimes.   IMC departures in that part of the world don't often coincide with high DA's. 

[PT20J]

I'm based on the west coast and have owned two M20Js. I used to fly a lot over and around the Sierra Nevada mountains and I've flown quite a bit in the Rockies including getting my T-shirt at Leadville many years ago. I've had no problems flying a J VFR at high density altitudes but you have to know mountain flying and you have to plan carefully. But if you need to fly consistently in the high country IFR, I would get a turbo. The margin for IFR ops is just not there in a NA airplane. Just my $.02.

[T. Peterson]

@oisiaa You are planning trips that are in excess of 500 miles and to high elevations. I believe you will be much happier with a K than a J. Call Jimmy Garrison and visit with him. I had the same question and he steered me to a K. I am grateful for his advice. J’s are wonderful airplanes but your mission almost screams turbo.

[1980Mooney]

5 hours ago, oisiaa said:

Sounds okay/safe for day VMC, but not for an IFR departure. I'll have to pull some performance charts to run the numbers to see what the book says. 

It is rare to see many GA aircraft flying in the combination of high DA and IMC in much of New Mexico.  First of all, Gallup and Santa Fe (and the entire state) are usually severe clear.  The only way that the arid New Mexico air becomes IMC is generally in a violent thunderstorm  or snowstorm that makes it all the way to the ground (you frequently see Virga falling that evaporates in the arid air before reaching the ground).  My brother had a plane at Double Eagle for many years.  He was Instrument rated but never got to fly real IFR approaches for that reason.  If the weather was IMC, it was generally so bad that you did not want to fly at all.   I have flown to NM many times - the worst IMC that I ever experienced was a dust storm back around 1999-2000 between between Roswell and Midland.  It was a complete brown-out so we made an unplanned stop at Hobbs ( I was worried about engine damage) and spent the night.  A Cessna 206 hauling checks back then landed at the same time.  The Commercial Pilot told me that he tried to get above it but could not so he also made a precautionary landing and spent the night.

However if you are intent on having a plane that can fly in high DA and IMC, i.e. do it all and dispatch at any time in all conditions, you also need to think about having FIKI.  Santa Fe is on the southern edge of the Rockies.  MSA east of KSAF is 13.5K.  Aviation weather is showing trace to light icing right now at 15K.  You ideally desire VMC when flying in the Rockies but conditions can change fast.

The alternative is wait out the IMC weather (it generally blows through fast in the SouthWest) and only depart in the cool morning air. - esp. if you land at Angel Fire, Taos, Sierra Blanca.

Edited October 26, 2023 by 1980Mooney

[haymak3r]

As a J owner, and living up against the cascades. If the situation would arise where I could get what I have right now, but with a K, I would jump on it. While the J does it, I would like to not be right at the limits for departures with higher DALT. I too have taken off with DALT in excess of 8k, from places like Lakeview, or over in eastern oregon. She DOES do it, but it just doesn't feel that great doing 400fpm and barely keeping 100mph while climbing. Plus with the slow speed and long climbs CHT's have a harder time coming down, as well as oil temps. 

Get a K if you have the option to. Heck, there is a rajay turbo thread on here that was recently brought up again. All I see there is MAN I wish I could get that on my J. lol.

[oisiaa]

There are so many factors to balance when deciding on a plane. I'm 99% in the Mooney camp, and it's pretty much 50%/50% for me for J vs. K with a slight lead on the J side. When it comes down to it, one of the main reasons I want a plane is to travel, and taking my dogs is a part of that. Without an easy way to get them on oxygen, I'm stuck below O2 levels anyway. My wife will want to sleep and I'm not comfortable with her sleeping on O2. Sound like climb performance at my intended high DA stopovers is low, but manageable. 

[ttflyer]

Here's some data from foreflight if you're interested.  310' per nm is possible depending on weight and temp in a J.  IMO if you are anti O2 (my wife is the same) no reason to get the K.  I'm not a fan of flying non-pressurized airplanes above 10K myself.  Many reasons to prefer the J. YMMV. 

ForeFlight Field Performance - KSAF KGUP - N333CD Oct 27.pdf

[oisiaa]

Those climbs aren't bad actually. I'm used to flying multi-engine where all we care about is engine out climb performance, and these numbers are better that what I'm used to seeing for 3-engine climb performance in a 4-engine jet. ....of course 4-engine climb capability is much higher, but you can't count on that.

[Z W]

@oisiaa

I've spent a fair amount of time flying in and out of the Rocky mountain range in a K.  Before that, a little time trying to do the same in a C model, which is not as good as a J for high altitude ops.  I like the mountains so the area is a common destination for me.

The C model did OK, I had it in and out of Sante Fe at least once, Denver area / front range a few times.  Not a lot of margin for error.  Clear skies and low winds required.  Forgetting to lean for takeoff could be fatal.  Generally needed to be at minimum fuel to maximize performance for safety.

In the K, it's a great feeling to line up for takeoff at max gross weight, go full rich mixture, spool up the turbo, and take off.  I've departed Telluride with 3 adults and 3+ hours of fuel at 80 degrees Fahrenheit and climbed out at 750+ FPM. 

It's also really nice to just point the plane at a mountain range, knowing you'll shortly be at a safe altitude to clear the highest peak if you want.  Examples - leaving Jackson Hole or Bozeman.  They're down in the bottom of a valley, with mountains in most directions.  The K can just take off and go and easily climb through the nearest passes.  In a NA, you're probably flying out of the Class D airspace down the valley, then flying circles in the climb to get to a minimum safe altitude, right in the middle of arriving and departing jet traffic.  You're burning fuel, which you're light on to try to stay well under gross weight.  You're nose-high on attitude with climbing CHT's.  The POH says it's doable, and I'm sure it is on most days, but it won't be comfortable.  If there's a 300 FPM downdraft from mountain wave (pretty common), you maybe aren't climbing at all or are even descending. 

Other factors - Go-arounds, if required, are a non-event at any airport.  I don't generally fly IFR in the mountains, but on the rare days when it's a safe option, SIDs are no big deal.  I flew a SID out of Sante Fe earlier this year and I'm not sure it would have been safe or doable in a naturally aspirated plane.  Wouldn't have looked safe out the windscreen, even if the performance charts say so.  Sometimes you're departing to fly away from the mountains, need to be IFR, and you're going to get assigned a SID.  Best to plan for it.

I've never felt the need for FIKI in the mountains.  If it's icy up there, I'm not going in any piston single.  But the turbo makes it comfortable on most other days, to any airport.

The turbo is not about speed, for me.  It's about safety, comfort, and options. 

On maintenance cost, over 12 years of ownership, the turbo's addition to the overall cost of the plane has really been not much, compared to what we've spent on hangar, insurance, fuel, annual inspections, hotels, rental cars, and general maintenance items.  It's an incremental cost for sure, but far worth it to me.

Every time this comes up, I notice that the people who are pro-turbo have all flown NA before.  The people who are pro-NA and are quick to say it's not needed and not worth the cost have never owned and operated one.  It's pretty rare to read a post from someone who used to own a turbo, sold it because it was too expensive and not worth it, and now flies a NA plane.  Especially for mountain flying.

Not knocking anyone's J model or other NA plane.  But for what you want to do, it sounds like a K or other turbo model might be a better fit.

[larryb]

The problem with the plan of being well below gross at high elevation airports is that if you are on a long trip you will have luggage and want full fuel. So you will be heavy.

That said I’ve taken off at flagstaff at gross weight, in the morning, with my J and had no difficulty. But ultimately I wanted a plane with more capability and replaced that J with a K.

[Utah20Gflyer]

You didn’t mention what kind of load you’re expecting to be carrying which is one of the bigger variables.  In my G model if I’m light I can take off at 8k DA and climb is excellent.  If I’m heavy climb rate is going to be poor and I won’t even try it.  I do have 20hp less than the J though.  
 

Turbulence and turning are big climb rate killers so depending on terrain and how bumpy the air is will be a factor in what is doable, unfortunately high DA is heavily correlated with bumpy air and there is a lot of terrain out west which can require turning.  If you can take off and fly straight for 10 miles that gives you more margin than if you have to turn a mile off the end of the runway.  
 

If you have to “circle” make your turn and then fly a long straight leg, turn, long straight leg.  If you are turning too much you won’t get the climb you are looking for.  
 

If you fly along the upwind side of terrain you can sometimes greatly improve your climb rate,  if you fly on the downwind side it can make climbing very difficult.   

[A64Pilot]

A J will do it, sure.

But a K will do it better.

Your use case pretty well describes the marketing brochure for a turbo aircraft.

A turbo aircraft will cost more to fly, those who say it won’t haven’t owned one long enough to have to fix the turbo and associated systems yet, just remember TANSTAFL.

”There ain’t no such thing as a free lunch”. Every increase in performance will cost $$, it’s just a fact of life, whether it be a boat, car or airplane.

[Shadrach]

OP asks a question about take off distances and not a single post with actual numbers. POH takeoff data for 77 J model and 85 K model. My gosh the mid 80s Mooney performance graphs were horrendous. I guess they thought that America would soon go metric and they would be ahead of the game.

1977 M20J

 

1985 M20K

[EricJ]

No data for the M20J at 8000 ft PA above 68F!   It gets over 100F at KFLG at 7015 ft elevation. 

[Shadrach]

28 minutes ago, EricJ said:

No data for the M20J at 8000 ft PA above 68F!   It gets over 100F at KFLG at 7015 ft elevation. 

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.

[0TreeLemur]

3 hours ago, EricJ said:

No data for the M20J at 8000 ft PA above 68F!

This plot from my '83J provides that.