Tuesday, September 30, 2008


A funny idea came into my mind. There are couple of Petrel Amphibians in Finland. It looks like a plane of Donald Duck.

Here is one discussion thread in Finnish about it:
Nyt on suomen kolmas akuankkakone valmis

It has staggered wings (two wings, one on top of each other). What if it was completely different. Not exactly completely, but quite completely. Now on this latest Super Petrel, the engine pod is integrated to the upper wing. How if the upper wing was the only wing on the plane, the lower wing would not exist, the upper wing would be twice as long. The tail would not be angled upwards from the bottom of the fuselage, but it would be rather connected with two booms to the wing, in similar manner than it has been done on Adam A500. And finally, but not least, what if the fuselage was not a traditional fuselage, but a pod in the end of a strut, that fits the occupants, and nothing more. It would end before the prop arc. This would allow moving the propeller a bit downwards.

So the result:
- no aerodynamic penalty normally associated with the amphibian planes.
- center of thrust is at the same level as is the lift (high wing)
- because of the boom tail, the tail does not hit the water unless the plane flips.
- because you would not need to fit the tail to the fuselage, the fuselage-pod could be made a better boat shape

I could not resist, but name this idea as Podrel. Actually this is not a new idea entirely, it is partially borrowed from a NASA tech paper, but the application to amphibian use could be new twist for the configuration.

What do you think about this?

Dynaero MCR-01

I had a chance to see the Dynaero MCR-01 yesterday at Malmi airport. Here are some interesting pictures about it:


Dynaero smile:


Double slotted flaps:

Flap mechanism:


Interesting finding: the upper slot is rigid part of the flap. It does not move by itself, and the mechanism is as simple as on plain flap or the single slotted flap found on Cirrus or Diamond. When the flap is retracted, the slot hides under the wing. Very clever design.

Thursday, September 25, 2008

Good NLF airfoil

The SHM-1 airfoil seems quite interesting. It was designed for Honda Jet. There is a patent about it. I need to investigate that further it seems.

Wednesday, September 24, 2008

Toyota General Aviation aircraft

I found an interesting article about the Toyota general aviation aircraft. It looks like it has been flown again.

Read the arcticle from here:

Wednesday, September 17, 2008

A Lancair builder has collected a list of links to tech papers, e.g. NLF215F


Interesting technical papers

There is link to the NLF215F airfoil tech paper. It was particularly interesting. Now I understood the philosophy of the profile - I was always wondering, why this profile has the low drag bucket at so high Cl (around 0.5) rather than what is realized in cruise with small aircraft (up to 0.2). But, it seems, that this airfoil is designed to be used with -10 degrees flaps. With those, the low drag bucket gets into the cruise area. Heureka.

Here is a direct link to the paper:

Monday, September 15, 2008

X-plane 9 flight simulator available for iPod touch / iPhone

I just downloaded the iPod touch version of the X-plane 9. I am quite impressed about it. It is by far the best mobile game I have ever tried. The controls are done with the accelerometers and throttle and flaps are controlled with two simple finger usable sliders on the screen. The landing gear and brakes have translucent buttons on the bottom of the screen. Everything is fully finger usable as it should.

The aircraft selection consists of Cirrus Vision Jet, Piaggio Avanti, Columbia 400 (that was a positive surprise since it wasn't included with X-plane before), and the C172SP. Needless to say that the Cirrus Jet is the most fun of these to fly.

It is possible to set the weather to IMC, but because the instrument panel does not fit into the tiny screen, it is not included with the sim. Therefore flying IFR approaches with the iPod version is not possible. You can keep the attitude though inside a cloud because of the HUD that includes attitude indicator.

Anyway, this is the best iPod touch app you can find from the App store. It only costs 7.99 eur and is worth every cent. You can find it under games category.

What could be cooler than fly virtual Cirrus Jet in bus when going to work tomorrow?!

Saturday, September 13, 2008

Twin engine concept, evolved from the single engine concept

Here is what I lofted today in the iRhino:

To make reasonable place for the rear seat/seats, the wing position had to be moved lowish position. The feet of the rear passengers are below the wing spar of the wing.
The rear window is not necessarily in the best place, it might be too much forward. The idea is that the rear seat ends before the prop arc.

The single engine idea in the previous post had apparent CG issues, how to get CG to correct position other than moving the prop completely on top of the fuselage, which moved the engine pod very high. This twin engine version which places the engine pods to the wings, solves this issue obviously.

Here is how it was drawn (in the case someone is interested in learning iRhino):
- The engine pod is NACA 66-025. It is lofted from couple of cross sections which were set along a helper-line which had the airfoil contour.
- The Fuselage is lofted from 5 elliptical cross sections
- The wings are lofted from two airfoil cross sections each
- The tail surfaces are lofted from two airfoil cross sections each
- The canopy and window utilize the Project to Surface -function of the iRhino
- The picture is drawn with correct dimensions. I used measurement -lines to make the parts correct size. The grid was set to 10 cm spacing.

The fuselage height is 86 cm, length is 6.6 meters. I have not yet measured if one can fit inside or not. But basically it resembles a sail plane fuselage. The fuselage may require some scaling up to fit more than two persons inside.

Friday, September 12, 2008

Single engine concept

Here is yet another concept illustration. The engine pod would contain HKS700T, Rotax 914 or UlPower 260i with pusher propeller.

The idea of the concept is simplicity, low drag and placing the propeller so that the arc does not get under the plane and thus is not vulnerable to flying dirt etc. like it is usually on pusher designs. The high wing is selected just because that way the center of thrust gets closer to the center of lift and the high thrust line does not cause that high nose down pitching moment. The engine pod fits between the V-tail, which makes the concept similar than the Cirrus Jet.

The major idea in this is that the part count is minimal. There are only two tail surfaces, two wing surfaces, and a single fuselage + pod.

I have done an X-plane model like this. In the model, the control sensitivity is low and the plane maneuvers slowly. It is difficult to make the ailerons and elevators effective enough.

Thursday, September 11, 2008

Idea: fowler slotted flapelevators, how to improve the efficiency of a tandem wing aircraft

I have been thinking how the efficiency of a tandem wing aircraft could be improved. In tandem wing aircraft the front wing determines pretty much how high total Clmax the aircraft is going to have which translates then to the required wing area. To maximize the efficiency, because flaps can not be used in the rear wing, the Clmax of the front wing is desirable to be as high as possible. Usually on tandem wing and canard aircraft the Clmax of the front wing is around 2.0 and the elevator is a single slotted flap.

It may not be mechanically very practical, but theoretically it could be possible to increase the Clmax of the front wing by adding more high lift devices into it. There could be a fowler flap implemented so that it increases the wing area substantially while the single slotted elevator flap remains working as usual in the trailing edge. The problem is that how you do that when the whole elevator system moves as consequence when the flaps are lowered or raised (the fowler is either inside the wing or protruded out of the trailing edge). But if this was practical with any other means than using servo motors for the elevator too, it could increase the available lift from the front wing somewhat. A challenging thing in this obviously is that the shear web that connects the spar caps goes through the front wing, and the flap system can not break the integrity of the shear web. More limiting factor also is that the chord length of a tandem wing aircraft front wing is low and there is not that much space for the high lift device.

Anyway, it would be interesting to try this out with a radio controlled model.

I hereby license this invention under the terms and conditions of GNU General Public License, version 3, or any later version. (C) 2008 Karoliina Salminen. All rights reserved. By reading this text, you aknowledge this and agree with the terms and conditions of the GPL license.

Monday, September 8, 2008

NLF airfoil with low pitching moment

I have been searching the web for such airfoil, and it seems like there is no such thing in the public domain. At least I have not found one.

For a canard/tandem configured aircraft, the main wing should have very low pitching moment, preferably zero if possible. The flying wing airfoils generally don't have very extensive laminar flow and they are not that interesting except for some exceptions (found one Wortmann airfoil which has quite high L/D but does not really compare to the drag coefficient of the NLF414F at high reynolds number).

So what I would be looking for would be:
- a thick (16-20%) low reynolds number natural laminar airfoil which has low or zero pitching moment, has design cruise Cl of 0.1-0.2 and which would have comparable drag charasteristics than the NLF414F or not very much higher drag than the NLF414F and which would have design cruise reynolds number around 5 million (not 10 million like the 414F) and which would achieve unflapped Cl of 1.2...1.3 at reynolds number 0.8 million.

So am I looking for an impossible airfoil? If you know that someone has designed and tested in wind tunnel this kind of airfoil, please let me know!

The NLF-414F paper

Here is the link for the design paper about NLF-414F

NLF414 design

Interesting thesis work about NLF airfoil design

Read by yourself from here:


Interesting NASA ebook: Concept to Reality

Here is a link to the book:

Concept to Reality

I find it quite interesting.

Friday, September 5, 2008

Dynaero MCR structure description

I have been wondering how the Dynaero wing is constructed specifically. It has aluminum skin and composite structure inside. What kind of structure is pretty nicely described in the following document: