Freedom Master AirSharkII

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AirSharkII

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Hello all, I have recently acquired an uncompleted Freedom Master Airshark kit. Some of you may remember the AirShark's debut in the '80's. A fast 4 place amphibian which still holds a speed record today. A few kits were produced (a dozen I think). Several aircraft flew with mixed results. They went out of business before the design could be refined. I was excited about this design back then and I believe with proper design and engineering this aircraft can be saved. I have begun consulting with designers and looking for any available information on the AirShark. There are a few more kits out there and I would like to make contact with those builders if possible. All ideas and criticisms are welcome. I'm entertaining the following changes to the AirShark: lengthen the fuselage ahead of the pylon( for a CG issue, more room for rear passengers, and more hull displacement for better performance on the water), improved flaps, replacing the O-360 with push/pull Rotax 914(EFI with a potential 140hp each x 2). The Rotax configuration is 100lbs lighter and would be unique! I'm looking forward to your responses, Tom
 

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AirSharkII

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The Aerostar has the same problem. If that is the only down side I might be able to live with it.
 

bmcj

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I was going to say "cooling", but then I remembered that you are liquid cooled. Are the props goinf to turn the same or opposite? What about noise or blade stress (and vibration) from the prop interaction?
 

AirSharkII

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I've only talked to Air Master Props so far and they don't see a problem yet. Dornier has done this with several of their designs with reasonable success. The jury's still out.
 

autoreply

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Given the original t/o distance (2800ft) I doubt whether 200hp is enough, compared to the original 350 (right?).

Also, how do you think to get 140 hp out of the 914?
 

AirSharkII

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The AirShark has never flown with 350 hp. That was their third generation design which never happened. The plane flew well on 200hp, but seaplanes always like more HP. I did say potential. There is a turbo EFI package for 914s claiming 140hp. They even have a low compression turbo EFI option for the 912s which has a larger displacement than the 914. I can see the latter possibly working out into a reliable power plant. Before I get to the engine installation, a proper analysis needs to be done on the airframe. The AirShark has also flown with an O-540(250hp).
 
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autoreply

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The AirShark has never flown with 350 hp. That was their third generation design which never happened. The plane flew well on 200hp, but seaplanes always like more HP. I did say potential. There is a turbo EFI package for 914s claiming 140hp. They even have a low compression turbo EFI option for the 912s which has a larger displacement than the 914. I can see the later possibly working out into a reliable power plant. Before I get to the engine installation, a proper analysis needs to be done on the airframe. The AirShark has also flown with an O-540(250hp).
Do you know the T/O distance with the O-360? If that's reasonable I wouldn't recommend against proceeding if you do realize that prop protection is necessary. You don't want to kill a passenger because a valve or piston breaks since those things DO happen.

A simple laminated sandwich might do the trick, while it dubs for sunscreen.

As for the 914, I don't believe any claim about that. I've seen the certified one passing by the maintenance shop... every dozen of hours or so and while an excellent engine it's squeezed out to as far as anyone should go, with regular problems in any wear-related part.

I wouldn't trade 20% more power for 20% of the original reliability :gig:

Expect that you ruin the rear prop in 25% of it's TBO time and the forward in 50%, or maybe it's even down to 10% for the rear.
 

AirSharkII

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I know it's a long shot, but you must admit, if it could be made to work it could be an amazing twin! I fly a SeaRey now and find the 914 very reliable when they are operated properly. I know of two planes in our fleet who have installed these hi output 914s. I will be watching them closely. Take off runs with 200 hp are around 14 seconds on land and about 28 seconds on water. Please explain what you think will happen with the propellers. Passenger protection can be managed. An IO-540-C (250hp) is our first choice and would be the easiest to install.
 

autoreply

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I know it's a long shot, but you must admit, if it could be made to work it could be an amazing twin! I fly a SeaRey now and find the 914 very reliable when they are operated properly. I know of two planes in our fleet who have installed these hi output 914s. I will be watching them closely.
I personally wouldn't trade a bit more hp for a lot of extra costs, risk and such, but then again, that's up to you.
Take off runs with 200 hp are around 14 seconds on land and about 28 seconds on water. Please explain what you think will happen with the propellers.
Water spray ruins props. Vibrations from the two engines, the pylon and the front prop will cause severe vibrations for the rear prop/engine, including unpredictable wear. No problem, as long as you design for it.
An IO-540-C (250hp) is our first choice and would be the easiest to install.
How about the claimed weight gain? I don't see how the 2X rotax is lighter than a single O-360. Two props, two gearboxes, twice oil, the installed weight of those two 914's is going to be at least 100 kg each (440 lbs).

Whatever you do, your rear engine is going to cook over the first flights ;)

All in all there's a lot that's changing in your design. Is the structure designed for that or do you essentially have to do a re-design?

In your situation I would aim at twice the 912 S which is 40 kg's lighter in total (90 lbs) and it also avoids the extra complexity of a turbo. I would also not stretch the fuselage, but instead tilt the engine pod backwards a bit since that's a lot easier.

A single engine alternative is the new IO-390X, much lighter and 210HP compared to the concrete block of IO-540 :)
 

AirSharkII

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I'm comparing to the IO-540-C (375lbs +Hartzell HC-E3YR-1RLF 82lbs+mount= approx 492lbs to 914 EFI (175lbs + AirMaster Prop 26lbs + mount= approx 432lbs). The difference is closer to 60lbs. Let's say they are equal. I find this acceptable. Pylon loading can be designed properly. The concerns will be how the propellers interact. The Air Master propeller uses a WarpDrive nickel edge blade. I have 500hrs on this prop with a lot of spray having gone through it. The propeller has held up amazingly well(no detectable wear). The turbo does add complexity, but the Rotax makes rated hp up to 8000'. This is very desirable when on a high density altitude lake. A small turbo prop sounds good, but I know nothing about them. At least I know a little about Rotax:). From experience, I do know you want instant throttle response when operating on the water. This can be difficult with a turbo prop. Fuel burn is an issue with turbo props also. The attraction to the push/pull Rotax, again, would be having a light twin that might even fly on one engine. I've had a recent communication with the designer of the Equator. This is the origin of the AirShark design(copied:)). He considers the Equator and AirShark "failed" designs. Siting several short coming of both designs. I think he's being a little harsh on himself for he was seeking perfection in his design. Amphibious aircraft are alway full of compromises and generally don't have great flying qualities. From what I have observed of the AirShark's performance, I find it acceptable. I also believe improvements can be made to the design at this stage of the project. Below is a photo of the Equator proto type and a push/pull model that was tested.
 

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Starman

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I'm curious to know what about this plane that the designer considers to be a failure? The things that stand out to me as possibilities are the very high thrust line and the low wing placement.

I'm sure that the low wing is there to avoid the need for outrigger floats and would be fine on smooth water but it could slow takeoff in rougher water due to waves hitting the wing. It seems that the engine could be lowered quite a lot if the top rear of the fuselage was lowered quite a bit, which would be pretty easy. You couldn't do that with a push/pull setup though.

Concerning the push/pull engine setup, I don't see that as being a problem, particularly cooling issues for water cooled engines.
 

PTAirco

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Looking at the top photograph, it seems it has a German registration. That ought to give you some peace of mind regarding the structure of the aircraft - few countries are as tough on homebuilt design and build standards as Germany. Nothing flies without a fairly comprehensive stress and aerodynamic analysis.
 

autoreply

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Why? What is the basis for this assumption? Any actual data?
Nope, pure speculation and especially the 10% is outrageous.
After having heard the operations of some waterpilots though it seems common that props, operated high above the water are replaced within 50% of their TBO or just above. I've also read about the problems of a tandem "box" on top of your wing where the vibrations from the front prop have a lot of nasty side-effects. I think it was in a German magazine a couple of years ago (about Dornier), but I'm far from sure that I'll be able to look it up.

I'm comparing to the IO-540-C (375lbs +Hartzell HC-E3YR-1RLF 82lbs+mount= approx 492lbs to 914 EFI (175lbs + AirMaster Prop 26lbs + mount= approx 432lbs). The difference is closer to 60lbs. Let's say they are equal. I find this acceptable. Pylon loading can be designed properly.
I presumed the original design was designed than to handle the 180HP and mass of the O-360. If it's indeed designed to handle a heavier and more powerfull engine I wouldn't see a problem in the Rotax setup either. Is it?
The concerns will be how the propellers interact. The Air Master propeller uses a WarpDrive nickel edge blade. I have 500hrs on this prop with a lot of spray having gone through it. The propeller has held up amazingly well(no detectable wear). The turbo does add complexity, but the Rotax makes rated hp up to 8000'. This is very desirable when on a high density altitude lake.
I always though lakes were on the lowest point of a valley. But then, our highest mountain is just over 1000' :ponder:
As for the turbo, if your aircraft is already designed for the weight and power we're speaking of I'd definitely favor the turbo indeed.
The props might make a hell of a lot of noise more compared to an original one (that's also the source of the vibrations), which might be a consideration when you're operating in a noise-sensitive environment.
For the rear prop I would look for a certified one, simply because you cannot afford to throw a blade (which occasionally has happened) because - even protected well - it still poses a risk. That ofcourse is a personal decision as well.
A small turbo prop sounds good, but I know nothing about them. At least I know a little about Rotax:). From experience, I do know you want instant throttle response when operating on the water. This can be difficult with a turbo prop. Fuel burn is an issue with turbo props also. The attraction to the push/pull Rotax, again, would be having a light twin that might even fly on one engine.
In the air it might (just), but don't expect any engine failure take-off posibility until you're up to 100' or so.
A turboprop is the best thing to have, almost vertical t/o, huge climb, if only because your wallet empties so quickly..


@ Starman,

I always though the low wing idea was horrible in a amphibious design as well. 2 years ago (Ila Berlin) however I spoke to a Russian designer of (I think) Beriev, who convinced me it really does work. The Russians are using it for decades and are very pleased with the concept.
 

AirSharkII

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We have quite a few high lakes here in the Sierra Nevada's. Photo is on Lake Tahoe, density altitude that day was 8700'. I not a fan of low wing seaplanes either. Mostly for docking reasons. When I watched a demonstration of a pilot walking out to the wing tip like on a surfboard I felt a little better about trying to make this work. Structurally the AirShark appears to be built like a tank. It is designed for 10g loading(this has not been confirmed yet). It will be heavier than I would like. However, if she ends up only being a two place 160 knot cross country aircraft that can only land on the best of lake conditions, I think I'll still be okay with that.
 

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autoreply

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We have quite a few high lakes here in the Sierra Nevada's. Photo is on Lake Tahoe, density altitude that day was 8700'. I not a fan of low wing seaplanes either. Mostly for docking reasons. When I watched a demonstration of a pilot walking out to the wing tip like on a surfboard I felt a little better about trying to make this work. Structurally the AirShark appears to be built like a tank. It is designed for 10g loading(this has not been confirmed yet). It will be heavier than I would like. However, if she ends up only being a two place 160 knot cross country aircraft that can only land on the best of lake conditions, I think I'll still be okay with that.
Well, I came to talk with the Russian guy because of the BE-103:

The low wing really does work and the very moment it doesn't anymore; well you can't land a high-wing then either :)

How about your design; was it designed from the start to absorp the loads of a 500 lbs, 250 hp engine?
 
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