Backcountry Pilot • Minimum lake size

Minimum lake size

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Minimum lake size

As a freshly stamped float pilot, I've been poring over Google maps looking at all the places a guy could land. The question is, can you take off?

Ok, I have to be honest. I'm fantasizing about owning lake property. Not all lakes are created equal, obviously. And here in Oregon they're sparse. Back east you can be quite discriminating. Lots of factors involved in choosing where you'd want to sink your money. #-o

How small is too small? After flying on Christensen Lake in Talkeetna, I came to the conclusion that's about as small as you'd want (approx 4900 ft in the long dimension) if you ever wanted to takeoff heavy or have friends visit with less powerful aircraft. A full mile would be a lot nicer. Several miles would make for something you could actually explore.

But I think you could operate on 2500 ft if no obstacles, if you had the room to make a confined area turning takeoff.

Thoughts?
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Re: Minimum lake size

Some questions: How high MSL is the lake? What is the DA during the season you'd be flying? What airplane?

Like the discussion about which airplane can operate out of a 660' strip, the answer is "it depends". My P172D has a 180hp Lycoming and CS prop. I fly out of a 4750' airport, with summer DAs ranging from 6000' to 7000'. The seaplane trainer was a 172E with a 180hp Lycoming and CS prop. When I took my SES training, it was at near sea level with DAs around 1000' in an airplane that is a virtual clone of mine. Yet my airplane has oodles more performance off a hard surface than the seaplane had off of the water. With half tanks and 2 adults, I can count on a ground roll of around 1000'. Running heavy, it can take nearly twice as long, but still under 2000'.

Once solidly in the air, the seaplane's climb performance was quite good, but getting off the water took awhile, using 20 flaps as I was taught (I never use more than 10 flaps in my airplane), carrying just two of us and minimal fuel for the lesson (or the checkride), about 15 gallons. How long was the water run? I really don't know, but it seemed to depend on how quickly I could find the "sweet spot", where the drag was least and the acceleration was best. But I'd guess that most of the time, it was at least 3/4 mile, or about twice as long running light at a low DA as my airplane takes running heavy at a high DA. At least once during my checkride, I don't think I'd ever have lifted off, if I hadn't realized after running way too far that I'd forgotten to lower the flaps!

That last sentence brings up the other issue: skill of the pilot. You and I probably have similar seaplane skills. Guys like Mike (MTV) or others here, with lots of seaplane experience, could likely handle a much smaller lake that we can.

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Re: Minimum lake size

I operated a 7GC Champ (135hp, mcCauley 7841 prop) on PK 1800s from Fire Lake in Eagle River AK. I think that lake is 3000-3500 ft, with trees at the south end and a hill with trees on the north end. I never felt it was short, although I had to be careful fully loaded. I easily flew that airplane off a 2500 ft tundra lake fully loaded while hunting. It's really going to depend on density altitude and power.
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Re: Minimum lake size

I'm a lowlander, so generally I'm talking about lakes located at 300-1500 MSL.
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Re: Minimum lake size

Lots of good lakes in Michigan, Minnesota and Wisconsin Zane! :D

I will defer to MTV to give good advice on this topic.

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Re: Minimum lake size

I figured 2500ft would be plenty of distance for a well powered seaplane. We usd to take a straight unmodified C-206 on 3430’s out of Shannon’s Pond in Dillingham and that was showing 1400’ in the supplement. Albeit with 2.5 hrs of fuel and two guys on a dead calm day that plane used every inch of pond. Look at H marker lake in Bethel or even Lily Lake in Kodiak they are well under 2500’ long.IIRC
Another depends on the plane and pilot......and insurance.LOL But this really does not answer your question cause if it’s that short your going to be light and the 3 examples I used are relatively obstacle free.
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Re: Minimum lake size

It depends.

Big difference between a skinny lake and a round lake because a curved path takeoff can make a lake with some width into a much longer effective surface.

Big difference between different airplanes and different floats as well. The top cub on floats at work needs 1200 feet at 2300 lbs calm wind. The Beaver needs more like 3,500 feet at 5,600 lbs.




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Re: Minimum lake size

Sometimes there is lots of room though.

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Re: Minimum lake size

Zane,

It totally depends on the airplane, and what sorts of loads you want to carry
As someone noted, Lilly Lake in Kodiak is narrow and ~ 2200 feet. A friend bought a Pacer on floats and asked me what I thought about running it out of Lilly Lake. My response was I'd put a Borer prop on it, and maybe wing extensions. He got a superhero sorta CFI, and I watched them attempt a takeoff out of there with min. fuel and the two of them (neither was "petite" in anybody's opinion). It worked, but they both needed clean underwear right after that takeoff. That was on a calm day.

He put a Borer prop on it, and that next winter extended the wings. Worked fine after that, but still not with big loads.

Turning takeoffs: Yes, those can work, and I've used them hundreds of times to get out of a lake that's too small for a straight running takeoff. But, the problem there is wind. With no wind, you make your J-Hook turn, and now you use the same takeoff lane again. With a wind, you have to make that second part of the takeoff run into the wind, which implies your initial "get on the step" leg is downwind. Then, the 180ish turn is done in a crosswind. With a LITTLE wind, that's not a big deal, depending on the plane and floats. A little more wind, and that turn can get hairy.

Of course, if the wind gets high enough, you MAY have enough lake to just takeoff into the wind, without the J-Hook turn. Maybe.

When I was working in the interior, I had two lakes I routinely put crews in that were small and round, and required a turning takeoff in most conditions. This was a loaded 185 or 206. I did this probably well over a hundred times in each of those lakes. I never felt I was working the edge, but......your shit needs to be stacked in a very neat pile if you're going to play that game.

One additional note on turning takeoffs: Passengers HATE them. As in variable from really nervous, even if explained prior, to just plain scared shitless. I had workers who went into and out of those lakes eight or ten times, and they were always white knuckle deals for them.

But, if you have a capable small airplane, on a good set of floats, keep the loads decent (meaning not stone empty but maybe not gross weight either), 2500 feet can work, with a little experience.

That said, I wouldn't make my first one of those takeoffs with a total of five hours of seaplane experience......Get a lot of takeoffs in THAT seaplane first, in big lakes, then start playing the confined area game.


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Re: Minimum lake size

I'm following this with great interest as I'd like to dig a float pond at my airport eventually. I could dig it 3500 feet long pretty easy and have a few hundred feet clearance to a powerline and trees. I've been wondering if that's enough, and it seems like it may be.
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Re: Minimum lake size

Couple notes after reading MTV's comments. First, he is totally correct about passengers hating curved path takeoffs. I always brief them if there is going to be more than just a turn to keep in the channel of a river. I like them to know it is coming, seems they are less fretted that way.

Second, the issue of a downwind leg for a curved path takeoff is a headscratcher that is usually glossed over in the books. I suspect it is treated as a calm water alternative in the mind of many of the authors. There are major issues with a step turn into the wind if the wind is substantial, so I do not do those if the wind is over about 10 kts. My preferred way to make a lake larger is an S turn takeoff. My initial leg onto the step is into the wind, then a step turn away from the wind about 90 degrees, and finally a crosswind, turning into the wind, curved one-float lift off. This makes use of the safest techniques for every portion of the takeoff slide but greatly lengthens the lane.

Third, as MTV says...if you need curved path takeoffs regularly then you want some real hours behind you on floats. There is a lot of work to do before things come automatically that you need to be there before you are adding complexity to the most hazardous portion of a flight.




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Re: Minimum lake size

Fuck it, I will stir the pot.

Speaking only about the j turn or 180 turn out of a short lake, not going down a river. By the time you add the drag of the floats going around a turn, the turning take offs just don't shorten the take off run, flashy yes.... useful? not really. If you have the room to get on step crosswind on the "J", or get on step down-wind on a 180 you have room to just take off straight into the wind. It is common sense, if you have the space to get on step down-wind, you have the room to get on step into the wind and takeoff. The added drag of a turn, especially while trying to get on step in a turn will negate all advantages. And, once on step how close are you gonna get to the edge of your lake? you do not want to hit rocks, or bushes, or even sand at step speed so you will stay away which cuts your take off run to where you would be if you just took off straight.

Just back up to the farthest beach and take off, or, if needed just kick folks off and shuttle.
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Minimum lake size

I’m no expert, but - from my limited experience flying various amphibs in the Northeast - you might also consider:

1. Regardless of how long the lake is, will there be a nice stretch near home * and * away from the neighbors where you can do your run-up // plow-taxi and/or start your takeoff run? Our neighbors love the first couple flights of the season for the romance of it but no-one will appreciate involuntarily living next to the run-up pad (aquatic or otherwise) and you’d rather be a good neighbor if you can help it.

2. Many lakes have trees along most of the shoreline. At our home base, there are 80’ obstacles and rising terrain in every direction on takeoff. Adjust distances accordingly.

3. As a non-professional, I find that I fly floats * way * more in summer when DAs and humidity are higher, engine-cooling less effective, storms much more frequent, and prevailing winds somewhat calmer. All of that adds up to less performance // flexibility.

4. Landing-lanes are also * way * busier in summer (boats, paddle boards, wave runners, kayaks, difficult-to-spot swimmers, etc). And none of those folks generally factor in seaplanes when they choose where to operate or stop for a break. In those conditions, a short lake can turn into * no * lake very quickly (and indefinitely) (and frustratingly). A good lake is one with multiple stretches, any one of which might be open temporarily on a busy day.

5. Lastly, one thing that I under-appreciated when I first got into this (amazing) seaplane flying is ground handling. Cubs are way easier (if not easy) to handle from a breezy dock compared to, say, a loaded 206. Many popular seaplane models can quickly become a handful at the shore even in comparatively light winds; they’re like a 25’ sailboat with a sail that stays up permanently.


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Re: Minimum lake size

Headoutdaplane wrote:Fuck it, I will stir the pot.

Speaking only about the j turn or 180 turn out of a short lake, not going down a river. By the time you add the drag of the floats going around a turn, the turning take offs just don't shorten the take off run, flashy yes.... useful? not really. If you have the room to get on step crosswind on the "J", or get on step down-wind on a 180 you have room to just take off straight into the wind. It is common sense, if you have the space to get on step down-wind, you have the room to get on step into the wind and takeoff. The added drag of a turn, especially while trying to get on step in a turn will negate all advantages. And, once on step how close are you gonna get to the edge of your lake? you do not want to hit rocks, or bushes, or even sand at step speed so you will stay away which cuts your take off run to where you would be if you just took off straight.

Just back up to the farthest beach and take off, or, if needed just kick folks off and shuttle.


That depends. Go fly in the interior for a while, where it's hot in summer. Getting ON the step can eat up a huge portion of lake, but once you're ON the step, accelerating to takeoff speed may not take long. And, it also depends on the airplane, and especially the floats. I worked PeeKay floats a lot on Cessnas, and PeeKays LOVE to step taxi, and they'll turn very tight. Some other floats, not so much.

But, I promise you, those lakes I referenced earlier....you aren't going out of those lakes by a direct straight run across them, at 100 degrees F in a 185. And, I NEVER tried takeoffs in those lakes with a full load....always made two trips. And, yes, I have come out of those lakes with a direct run, and in cool temperatures and very light, with a little breeze, it can work, barely. You of all folks should know that putting all those conditions on an operation simply means you'll never go there.

Go spend some time in the interior on floats....most of those lakes contain zero rocks....as in none. I'm not talking Katchemak Bay, Alaska Peninsula or Kodiak, where there is almost no such thing as mud. On the Yukon Flats, the muck is feet deep......I actually found a hard bottom in ONE of those lakes out there, and I've landed in literally hundreds of them.

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Re: Minimum lake size

Density Altitude can make a huge lake very small. Density altitude at 100 degrees an 100 feet at 100' MSL is pretty much the same as a lake at 2500 feet with 85 degrees (those were the temps we were seeing this summer). Turns in the water add drag, that is just a fact, even more so when you are displacing water, all that drag just adds to your total take off run. I have found high time, current, float pilots on both sides of this argument. While not even close to a high time pilot I am getting there and know which side I fall on.
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Re: Minimum lake size

One of the things this discussion illustrates is that, as I've emphasized for years, seaplane flying should ALWAYS be considered a true off airport kind of operation.

As such, there are differing techniques and many, many different kinds of scenarios that one may face doing this kind of flying. When I moved from Kodiak to the interior of Alaska, the flying was vastly different, and demanded some very different approaches. Everyplace offers different challenges, and demands techniques to meet those challenges.

And, what works in one aircraft make/model, and on one set of floats or hull, may or may not work well on a different aircraft or the same aircraft on different floats. Frankly, you really need to become very familiar with the floats you're on every time you get in another airplane with different float models. Sometimes these changes can be a real eye opener as well.

Which, of course, is one of the reasons that flying seaplanes is such great fun.

A classic example of that is the difference between the early PeeKay 3500 A and B floats on a Cessna 185 and the later, but nearly identical appearing at first glance PeeKay 3500 C and D floats. The later floats are MUCH better performers than the early floats, and PeeKay got a real black eye from the performance of those early 3500s.

And, sometimes, you have to innovate to make things work.

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Re: Minimum lake size

Zzz.. I think you pretty much nailed it. I looked for a cabin here in AK for years and my limit was 2500’ with good low trees/terrain at departure ends. If the lake had tall trees or hills, then it needed to be longer. (185 Aerocets, long wings).

I felt that I could do that near gross relatively comfortably with my family and friends on board on a regular basis.

Yeah..sure, you can do step turns and stuff to shorten things up, but who wants to do full focus takeoffs outta their lake house every time.

You can probably go shorter in a cub or similar plane.

Food for thought..
The 2500’ point in the West water lane at PALH is the beginning of the channel.. sit there on a busy day next time you are up here and watch how high most planes are at that point and where they come off the water. That will give you a gauge on what can typically be done..
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Re: Minimum lake size

Hsivany wrote:
Food for thought..
The 2500’ point in the West water lane at PALH is the beginning of the channel.. sit there on a busy day next time you are up here and watch how high most planes are at that point and where they come off the water. That will give you a gauge on what can typically be done..


I watched a Rust's Otter do a turning takeoff from their little bay into the channel and he was airborn in what looked like 100 ft.

But, the Otter is the Otter...

Good answers, thanks MTV and Wes and others. Agreed Hsivany that it wouldn't be fun to have to do seat-chewers every time from your home strip. We're in no hurry so I have time on my side.
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Re: Minimum lake size

In Dale deRemer's hard to find book "Water Flying Concepts", he teaches calculating a "Delta Ratio" for your aircraft. This is the ratio between how long your water run is and how long you need to climb to clear 50' shoreline obstacles.

Once you know it, the ratio is pretty constant while the takeoff water run distance varies with weight, wind, and DA. Say it is 60% for your machine (your EXACT machine: airframe-engine-prop-floats-mods, etc.). If you use 2,000' to get off the water at a given lake on a given day loaded to a given weight, then you need 3,333' of lake to climb over a 50' obstacle on shore. The ratio remains constant. If, due to loading, DA, and no wind, you needed 3,000' to get that same machine off the water, then you need 5,000' to clear the shoreline obatacle.

Note that if there are homes/camps on the shore, you would not be 500' above them. Passing low over someone's house on a full power climb is how lakes get closed to seaplanes.

Many lakes in Northern California are dammed reservoirs in mountainous terrain where you need to double your distance margin or more because the shore is already more than 50' above the water, and the pine trees grow 100', then the terrain rises steeper than your climb angle.

Please don't be this kinda guy. Small lake with lots of summer homes on a busy Saturday afternoon with high temps and rough water.

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Re: Minimum lake size

I used to tag along in and out of Shannon's Pond alot. Like TVAT said, its listed at 1,400' in length but for whatever reason it felt a little longer. My employer (back then) had two slips on Shannon's in the summer and we came in and out with Beavers and a 206 frequently. We were always light going out though, especially in the 206. I can honestly say I never saw anyone cut it close. I guess that's a product of what they chose to load and what they chose to leave on the dock. If we had heavy loads to haul, we made the 30 minute drive to a bigger lake with alot more room, and we did that often. It was nice to have that luxury.

Below is a little video from 6-7 years ago that I dug out of my vault on approach into Shannon's....its uncut and unedited so sorry for the length. Short finals start at 1:00 and 4:00. Shannon's is a cool little spot with alot of great pilots.

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