K vs. C Model Short Field performance

[bencpeters]

As the topic implies - I'm interested in hearing experiences from people who upgraded from a C to a K and have a decent amount of experience operating on short (< 2500') fields with both. I currently have a '64 C model based at a paved 1800' runway (850' elevation, reasonably significantly upsloping in one direction, +100' displaced threshold on one end, no obstacles directly in approach paths, but some noticeable 50' trees offset from the extended center lines), and I've been wondering whether a K model would work for the same mission. With the C I treat every landing and takeoff as a short field, and have some personal minimums around density altitude and loading, but it generally feels safe, albeit without as much margin as I'd have on a longer runway. Without having ever flown a K model, my impression is that it would be more power and better climb, so perhaps better taking off, but heavier (and more slippery), so more challenging on the landing side? But I'd love to hear from people who actually have flown both and can make the direct comparison!

Thanks!

[M20F]

A little short for a K

Link to performance charts

[kortopates]

The upslope for landing and downslope for takeoff can be a big advantage.
The K will use up more runway both on takeoff and landing.
It’s all about weight!
So suggest you run the numbers using a POH. Assume the average K has about 980 useful load. Calculate the difference in takeoff run and landing distance (without the 50’ obstacles) to get a good comparison.
But if you’re already good with short field landing techniques then you already know you can beat POH landing distance easily, but not takeoff performance.
Although doable, personally to tight for me to be based on such a short field.


Sent from my iPhone using Tapatalk

[Z W]

Well.. I upgraded from a C to a K model, so I guess I'm your target audience.

The C had a 3-bladed prop and was a pretty good short field plane.  I don't think I ever had it in and out of any 1,800 foot runways but I could imagine it working.

I would not take my K to an 1,800 foot runway.  It just needs a more, landing and taking off.  Not enough margin for error for this pilot.

I've done 2,700 feet in the K and it felt tight, though within safety margins.  It has a 2-blade prop and I've heard a 3-blade can improve the short field performance, both for takeoff and for landing (extra drag on landing). No personal experience.

The K is a much more slippery plane with significantly more weight and mass than the C, and not that much more horsepower.  It does better significantly under gross, but that's not its mission - it likes to get up high and fly long distances, so I'm usually putting as much fuel in the tanks as I can, while staying under max gross.  Basing it at an 1,800 foot strip would be a no-go for me personally, after several hundred hours in the plane.  I'd say 2,500 minimum for routine use.

Good luck, hope that data point helps.

[jrwilson]

I also had a C with a 3 blade prob and upgraded to a K  (231) with a 2 blade.  My shortest runway limit is about 2,400’ with the 231 and that’s fine most days.  Weight can be a factor of course.  Something that’s not considered is the 231 throttle is finicky, you can’t just go full throttle like on a 252.  So my takeoffs eat up a bit more runway because that initial acceleration is slower and I’m being careful with the throttle throughout the takeoff roll so I don’t overboost.  I’d say 1,800’ is much too short of a runway.  

[hubcap]

I have a little over 400 hours in my K. My personal minimum is 3000’ of runway. It will do shorter, but on a hot day with no wind at max gross (2900lbs) you could use up most of 3000’ if you come in a little fast.

[Hank]

@DanM20C should be able to contribute to this discussion. He should now have several hundred hours in each.

From what I've read, the K is a bit of a runway hog on takeoff; those with the Encore conversion use much less runway. But all K owners here seem more concerned with landing performance, which as a C pilot I find surprising. That's where (their) actual experience trumps (my) book knowledge. 

Whaddaya say, Dan?

[Will.iam]

I have a K based at a 2600ft runway. Had to remove other pilot operators from my insurance or pay and extra $500. There is a bad bump in our runway at 2000ft mark. Even max weight 100degree summer day i was off the ground before the bump but i had a downward sloping hill to help. The landing is more tricky either trying to slow down before the bump landing south or landing after the bump going north but i have the hill to help slow me down. I also operate at night too ahd the landing height system has really helped me at night. I would be ok with 2000ft flat runway and no 50ft obstacle off the ends but that would be my limit and i would definitely get a 3 blade MT prop instead of my 2 blade now for both the weight savings and better takeoff and landing performance . My dad operated a 201 J model back when the runway was only 2000ft and had a 5ft fence at tye end of the south end of the runway. He once landed there with 4 adults and 3 kids in the baggage compartment knowing what i know now we were at max weight landing.  K doesn’t perform as well as a J at sea level for solely the fact a k has a higher empty weight than a J and those 10 extra horse  power does not makeup that extra weight difference in sea level takeoff performance. 

[Z W]

My K model likes to float in ground effect, a lot more than the C did.  The only way to stop the float is to come in slower, but how much slower depends on your weight.  We're talking about approaching at 70 KIAS vs 75 KIAS and the difference can be 1,000 feet of runway use on landing.  It also really matters when you pull the throttle over the fence.  Wait a couple seconds too long and you will float 500 feet.  Pull it too early and you'll be flaring over the grass before the runway and hoping you float as much as you thought you were going to, or adding power back in.  I find it's easier to land short when heavy, oddly enough.

I flew with a very experienced Mooney instructor at a MAPA PPP who kept telling me I was too fast, we shouldn't be floating that much, etc.  He said here, let me demonstrate, and proceeded to float more than I had for a few landings.  He said he hadn't been in another Mooney that liked to float that much.  We eventually got some real short field landings done but it's not easy to nail every time.  Add in some wind gusts, some traffic in the pattern, obstacles to clear, a bit of fatigue, and it's not something I'd want to have to do on every landing at home.

[Shadrach]

 @bencpeters
I’ve been enjoying a lot of the first hand experiences from C to K owners. There is a lot of good info here.

I am not trying to be contrary but some of the comments don’t comport with my understanding of physics. Which is to say that there may be operational procedures that account for and contribute to the differences in “feel”

Some of the difference mentioned that I think are likely more perception than reality:

Airframe cleanliness - yes the modern (post 1978) airframes are cleaner and this will make a noticeable difference in cruise speed.  However, the "slipperiness" from these aerodynamic improvements at approach, climb and landing speeds, is likely more perception than reality. 

Float - why would a K model be more prone to float?  It’s the same airframe as a C model, just 10” longer with higher wing loading.  Same wing, same flaps. What’s more likely is that pilots for whatever reason (perhaps the aforementioned higher wing loading), are flying approaches at a higher multiple of Vso in the heavier airplane.  Operated by the numbers, there should not be a lot of daylight in the landing performance of the two airframes flown at the same weight and approach speed.

Weight is where there is a significant difference in these models. I don’t have any K model time, but I think 1800’ is tight for most of them based on book performance numbers alone.  Most C models weigh in at <1700lbs empty. Most K models are going to be >2000lbs empty. So ~400lb or more delta in weight.

It’s entirely plausible that the single pilot, take off, operating weight of your C model would be less than the empty weight of a K model for many missions.

I fly a mid-body (F) with a fairly large range of operational weights (op weights at take off range from 2050-2740lbs). It’s a different experience when operating at <2200lbs as you are likely accustomed.  Most K models with you, gas and bags are going to be within spitting distance of your C’s 2575lb mgw. The K model has a 17% horsepower advantage but compare operating weights for the same trip and in many cases you’ll find that you’ll likely be operating with a lower power to weight ratio unless operating both at max gross.

Climb and cruise performance will be better in the K model but not significantly so until above DAs of 5000’ or more

Has your mission changed or are you just wanting an upgrade?

 

[exM20K]

That’s not enough runway for me.  I operated a 231 out of LL10 for 5 years with runways of 2250 &2500 paved, and 1750 grass 720’ MSL.  I never used the grass runway in the Mooney, even with the wind straight down the runway. The 2250 was fine.

How much heavier is the as-flown K than the C?  It’s the same wing and a little more tail.  In my plane, and most Mooneys, I’d expect, each 100# additional landing weight equals another 100’ in landing distance.

It might work when light with the right conditions, but you’d be putting a lot of pressure on yourself.

-dan

[KSMooniac]

I'm in the conservative camp as well and would not routinely operate out of an 1800' strip in a Mooney, and especially a K or heavier.  The slope and lack of obstacles certainly help, though, so it is not like other short strips.

In a Caravan formation clinic several years ago, I took a turn at Lead and had a wingman in a K.  Granted, our standard formation takeoff is one on a wide and long runway and not a max-performance or short field procedure, but I was shocked at how I was able to run away from the K in my J on takeoff and initial climb.  I was lighter weight and have a 3 blade MT so that helped of course, but I thought a turbo and +10 book horsepower would help considering it was a warm day and he could boost it, but it was surprising to me nonetheless.

If you're going to do it, I would consider mods to increase the safety margin to include an AOA system to nail the approach speeds, and the MT prop to reduce weight on the nose, improve initial acceleration and climb and to provide increased aero braking when you pull the power in the flare as well.  Perhaps those improvements and some good training and practice will make it a bit safer for routine operation.

[Shadrach]

27 minutes ago, exM20K said:

That’s not enough runway for me.  I operated a 231 out of LL10 for 5 years with runways of 2250 &2500 paved, and 1750 grass 720’ MSL.  I never used the grass runway in the Mooney, even with the wind straight down the runway. The 2250 was fine.

How much heavier is the as-flown K than the C?  It’s the same wing and a little more tail.  In my plane, and most Mooneys, I’d expect, each 100# additional landing weight equals another 100’ in landing distance.

It might work when light with the right conditions, but you’d be putting a lot of pressure on yourself.

-dan

Isn't it the same tail save for the shorter rudder on the early C models?

[kortopates]

24 minutes ago, KSMooniac said:

I'm in the conservative camp as well and would not routinely operate out of an 1800' strip in a Mooney, and especially a K or heavier.  The slope and lack of obstacles certainly help, though, so it is not like other short strips.

In a Caravan formation clinic several years ago, I took a turn at Lead and had a wingman in a K.  Granted, our standard formation takeoff is one on a wide and long runway and not a max-performance or short field procedure, but I was shocked at how I was able to run away from the K in my J on takeoff and initial climb.  I was lighter weight and have a 3 blade MT so that helped of course, but I thought a turbo and +10 book horsepower would help considering it was a warm day and he could boost it, but it was surprising to me nonetheless.

If you're going to do it, I would consider mods to increase the safety margin to include an AOA system to nail the approach speeds, and the MT prop to reduce weight on the nose, improve initial acceleration and climb and to provide increased aero braking when you pull the power in the flare as well.  Perhaps those improvements and some good training and practice will make it a bit safer for routine operation.

The K normally take more time to accelerate to Vy on takeoff over a J but now that I have the MT prop on my 252/Encore I was literally shocked at how much faster the plane gets off the runway and how much steeper Vx is - too steep for my comfort and I fly every Mooney at Vx  for a short field takeoff on flight reviews. 

[Shadrach]

9 minutes ago, KSMooniac said:

In a Caravan formation clinic several years ago, I took a turn at Lead and had a wingman in a K.  Granted, our standard formation takeoff is one on a wide and long runway and not a max-performance or short field procedure, but I was shocked at how I was able to run away from the K in my J on takeoff and initial climb.  I was lighter weight and have a 3 blade MT so that helped of course, but I thought a turbo and +10 book horsepower would help considering it was a warm day and he could boost it, but it was surprising to me nonetheless.

I had a similar experience departing my home base.  I was feeling a bit outclassed in my vintage, guppy mouthed, M20F as I admired a beautiful 231 in line just ahead of me for departure.  I was cleared for take off about 30 secs after him. We were both westbound. I followed his climb gradient thinking he'd pull away. Oddly, he seemed to be getting larger in the windscreen. Then Tower called to verify I had "that Mooney in insight".  I confirmed and asked him if I was faster and he just said he had gotten a collision alert. I increased my pitch slightly and offset my track to the right 20°. I was slightly ahead and roughly 500' above him when we arrived at the VOR (5.5NM from the runway) where he turned south. It was a much nicer, newer plane then mine, but it was hard not to admire how the old girl goosed the turbo until we parted ways.

[PT20J]

Acceleration is a function of thrust,  (F=ma). So, the MT prop must generate more static thrust than the original prop.

Vx is defined as the speed where the thrust available exceeds the thrust required (drag) by the maximum amount. So, a prop that is more efficient at creating thrust at low speeds will also improve Vx. 

Thrust falls off as true airspeed increases at constant horsepower.

Vy and cruise speed are determined by available excess horsepower rather than thrust. 

[exM20K]

51 minutes ago, Shadrach said:

Isn't it the same tail save for the shorter rudder on the early C models?

More arm on it, and there’s a 1” extension on the trailing edge,IIRC.  

-dan

[PeteMc]

I used to routinely fly in/out of a 2500ft strip, but it was at sea level.  So it was doable even on hot days, but again, it's all about the load.  I've also gone into 1800ft strips, but I don't think I'd make it a norm.  Again at sea level and there were no obstructions (the ocean off the end of the Rwy).  And I would not do an 1800ft Rwy today.  I'm not "as practiced" on my short field landings as I used to be.  It was no biggie going into short fields back when we were trying to simulate a Mooney Carrier Landing for an article at BDR (stop before the intersection on Rwy 29).  But not only do you need to be right on the numbers, you actually have have the "feel" for if everything looks right.  And that takes CURRENT experience, not just experience.

If this is your home airport and you're always flying into it, the I guess it would be doable.  But you'll really need to crunch the numbers at different weights and temps as the K will fly much different than your C.  But the Ks are good planes. 

 

[Bolter]

17 hours ago, bencpeters said:

As the topic implies - I'm interested in hearing experiences from people who upgraded from a C to a K and have a decent amount of experience operating on short (< 2500') fields with both. I currently have a '64 C model based at a paved 1800' runway (850' elevation, reasonably significantly upsloping in one direction, +100' displaced threshold on one end, no obstacles directly in approach paths, but some noticeable 50' trees offset from the extended center lines), and I've been wondering whether a K model would work for the same mission. With the C I treat every landing and takeoff as a short field, and have some personal minimums around density altitude and loading, but it generally feels safe, albeit without as much margin as I'd have on a longer runway. Without having ever flown a K model, my impression is that it would be more power and better climb, so perhaps better taking off, but heavier (and more slippery), so more challenging on the landing side? But I'd love to hear from people who actually have flown both and can make the direct comparison!

Thanks!

I am guessing Cashmere.  What other aircraft do you see there?  Anything comparable?  It is a pretty short runway, near hills, and in the middle of town, so not very forgiving.  Summers can get hot, too.  What are the winds like?

I have never landed there in my former J or current R.  Too short for me, at least for as long as I want to carry any useful load. 

-dan 

[Shadrach]

@bencpeters  Given your location, I am curious if have you have ever been into Stehekin (6S9)?  I inquired about the strip when I was backpacking there last summer but the locals implied that while it is maintained it is largely unused.

[bencpeters]

Great info everyone, thanks for the replies! There are enough comments here about worse takeoff/climb performance that it seems like it's probably not the right option. I'm conditionally comfortable operating there with my current C, but it feels demanding enough that I'm not really interested in making a change that would decrease margins over what I'm doing now.

 

2 hours ago, Bolter said:

I am guessing Cashmere.  What other aircraft do you see there?  Anything comparable?  It is a pretty short runway, near hills, and in the middle of town, so not very forgiving.  Summers can get hot, too.  What are the winds like?

Yep, 8S2. Definitely not very forgiving. Fortunately, EAT is close by, so if I need some combination of high DA, heavy payload/lots of fuel I end up bumping over there (I flew to KSUN once with 4 people, and just met passengers over at EAT). I'm pretty diligent about going around if anything's not feeling good on short final down to the flare - really want to be wheels down and braking in the first 1/3 on the runway.

Most of the other aircraft there are a mix of Cessnas (170, 172, 182s), which I think are all a bit more forgiving. I've seen a J there once too, and I heard there used to be a J based on field in the past. I have a friend who said he's flown a C210 in there from time to time too.

Winds generally follow whatever's happening in Wenatchee but quite a bit weaker - the airport's a lot more sheltered. Usually that means fairly well aligned with the runway (east/west), but I've definitely sometimes had some interesting cross-winds to contend with. The biggest wind-related concern is usually when you've got strong westerlies - that blows over the higher terrain on the west end of the valley and can cause some funky rotor/turbulence on the west edge of the valley at pattern altitude - need to make sure you're ready for some big airspeed variations and potential sink if you take off on Runway 25 (upslope) due to winds when turning crosswind if departing to the east.

 

1 hour ago, Shadrach said:

@bencpeters  Given your location, I am curious if have you have ever been into Stehekin (6S9)?  I inquired about the strip when I was backpacking there last summer but the locals implied that while it is maintained it is largely unused.

I haven't, but it's on the list for sure! I'd love to fly in there some day and go climb Goode from there instead of Rainy Pass. I've seen one video online somewhere of a Mooney landing there, but I can't imagine it's common... If you're part of the FAT PNW (Flights above the PNW) faceboook group, I've seen a number of conditions reports for Stehekin posted there. My impression from these is that it gets better over the course of each season - it can start out a bit rutted/rocks but people do some work as it dries out to improve things. I'd guess it's a bit rougher than usual this year due to the Pioneer fire cutting off access for a lot of the summer, but I don't know for sure.

[Bolter]

1 hour ago, bencpeters said:

I haven't, but it's on the list for sure! I'd love to fly in there some day and go climb Goode from there instead of Rainy Pass. I've seen one video online somewhere of a Mooney landing there, but I can't imagine it's common... 

I assumed it would have been Piper Painter, but its another bush flying Mooney:

 

[Will.iam]

Ok i know this is sacrilegious but if you really wanted to get a K in there you can put stall vanes on the leading edge of your wing which will drop your stall margin by about 7-8 knots which is huge for landing roll out. You will sacrifice 2 to 4 knots top end speed but mooney’s with fiki also take a top speed hit to gain icing flexibility you would be taking the hit for short field performance. My neighbor has stall vanes on his 182 and I’m amazed at how slow he gets in the flare before touch down with very effective aileron control even at that slow speed. He also has them on his barron twin but that can be dangerous as he can get way slower than VMCA and if he lost an engine would be forced to put it down as go around is now impossible at that slow of speed. 

[PT20J]

9 minutes ago, Will.iam said:

Ok i know this is sacrilegious but if you really wanted to get a K in there you can put stall vanes on the leading edge of your wing which will drop your stall margin by about 7-8 knots which is huge for landing roll out. You will sacrifice 2 to 4 knots top end speed but mooney’s with fiki also take a top speed hit to gain icing flexibility you would be taking the hit for short field performance. My neighbor has stall vanes on his 182 and I’m amazed at how slow he gets in the flare before touch down with very effective aileron control even at that slow speed. He also has them on his barron twin but that can be dangerous as he can get way slower than VMCA and if he lost an engine would be forced to put it down as go around is now impossible at that slow of speed. 

Did you mean vortex generators?  https://microaero.com

[Hank]

Someone here has VGs on their Mooney. Seems they also have FIKI. Who is it?

@aviatoreb?