Aerobatic Airplane Developed in a Brazilian University

Hi Paulo,

Very good looking airplane. I understand this is a tubular frame construction with a wood wing and a 4 cylinder Lycoming engine. It seems to be in the same class as the Lazer, DR107 and the Capena.

I also understand the concept of using a 4 cylinder to minimize the operating costs; however would you develop a higher power version for international competition?

Best Regards,

Olivier

Dear Olivier,

thanks for commenting on our post!

Yes, Mehari has some similarities to DR-107, Lazer, and Extra 230. But at the same time, there are many differences. The airplane size is smaller then an Extra230, but it is bigger then DR-107. We try to use high aspect ratios on wing, tail and also fuselage (length / mean diameter) in order to give to the airplane a good visibility at the sky. We also believe that a  more "stretched" airplane is better for flight qualities. During the design we spent many time trying to adjust the flight qualities (deflections and force per g in any position and airspeed, as well as post-stall behavior) in order to have an airplane that is easy to fly, despite its small size.

The ailerons design is quite innovative. We try to make it more effective on the wing tip, as well as Mr.Extra try to put on his new 330SC, but with a different approach.

This prototype was build with wood spars on the wing and tail in order to save money. Now, after flight test programs, when we are sure about the airfoils and geometry, we will use these wings as a model to build new ones, with molds, and in carbon fiber (vaccum pre-preg). With this we intended to save, at least, 30 kg.

About a six-cylinder... yes, the heart beats to it... Take a look on three views.

Hi, Paulo,

I note the construction of your airplane is much the same as on my Dalotel DM165, which I'm restoring. I am most interested in your upcoming flutter tests. Do you have a counterweight in the rudder? My airplane came to me with all of the top of the rudder missing (that's it in the image to the left, with a GIMP-added top), and I don't know if there was a counterweight in it. I don't think there was, although my ailerons (made of aluminum) have counterweights. I've attached a photo of my new, somewhat redesigned rudder. It would require a lot of weight to counterbalance it, another reason I doubt it had any weight in there. Best luck with your project.

.......Ray

Very nice plane!

Aircraft design and aerobatics, my two favorite things!

Oliver,

nice video. Is it yours airplane?

About the video... Now we are using a HD camera produce by GOPRO company (www.goprocamera.com). It is an amazing machine. We are using it not only to produce midia but also to help on flight tests. Now we are starting a study about flow detachment on wing-fuselage junction (to optimize this fairing) and this camera is helping a lot to visualize the flow using wool tufts.

Soon I will post some videos!

Best Regards,

Paulo Iscold

Ray,

in our case we don't have weight balance on the vertical tail, mainly because we have a large horn. Our ailerons is almost 100% balanced and the elevator was balanced, but in order to improve the flight qualities (specially the difference of force per g on positive and negative maneuvers), we reduced it a little bit (I can't tell you know the correct value). This is always a fight on aerobatic airplanes, prevent flutter or improve flight qualities. Recently we was involved in the preparation of two airplanes for Red Bull Air Race and on both we reduced the elevator balance to make the airplane more confortable to fly near the ground.

In your case, I don't believe that you need 100% balance on the rudder. Just check how much balance you have now and then we can think to put a little bit more (not 100%) on nothing. What is your VNE?

About the tests. In your case you can performer old tests to estimate the flutter speed. The older BCAR give a good approach to this. In our case we are build a data acquisition system to collect data of many accelerometers installed through the airplane and a aerodynamic shaker to produce low energy vibration in many frequencies... It is too complicated and I don't believe that you need this. 

I hope I am helping you!

Best Regards,

Paulo Iscold

Jason,

these subjects are really interesting.. In my case I am in doubt about aerobatic or race airplanes... Take a look on this airplane, the first one that I developed with students at the university...

http://www.youtube.com/watch?v=B9pveZMfhNc

http://www.youtube.com/watch?v=KwRxAzN23jA

Best Regards,

Paulo Iscold

Paulo,

No this is not my plane, mine is still being worked on. I was lucky enough to have a friend let me fly is DR-107, this is where the video comes from. I used a CONTOUR HD camcorder.

Cheers,

Olivier

 Hi, Paulo,

Unfortunately I do not know the VNE of the Dalotel. That information was not provided in all the paperwork I have on this unique airplane. I know the maximum speed (190 mph, or 164 knots, or 300 kph ), the 75% cruise (170 mph), the 60% cruise (147 mph), and the stall speed (56 mph), but not the VNE, Vx or Vy. Judging from the max speed I would guess the VNE to be in the neighborhood of 250 mph. The elevator is not counterweighted at all. Like yours, my airplane has no flaps. Mine originally weighed 630 kg empty, and I expect to reduce that to around 600.

When you said your aircraft has "a large horn," did you mean the forward extension of the rudder, or the control horn to which the rudder wires attach?

 I've attached a photo of my airplane as it looked in 1969.

........Ray

Ray,

my suggestion... no counter weight for first flight, and keep it under 190mph!

Horn for me is the forward extension of the rudder.

Good luck on your airplane! Keep in touch!

PIscold

That's GREAT advice. Wilco! Thanks for the good words, and happy landings to you with your project.

 ...........Ray

Hello everybody, take a look on these new photos of our airplane!

http://www.flickr.com/photos/acrobrasil/

Hi Paulo,

What's about the flight tests of the Mehari 309? Can you compare its performances vs the DR107?

Vertical penetration, etc.I see the bottom of the fuselage is flat, is there any reason for that or is it only

for simplicity? I like the design of the Mehari 309.  Do you plan to publish / sell the set of plans?

 Thank you.

Patrick

Patrick,

after almost one year of flights we decide to stop the airplane to produce a carbon fiber wing and paint it. During this time we realize that the wing aerodynamic design was correct (maybe just a little bit larger aileron span) and a investment on a lighter wing will worth. We remove the wing and now we are using it as a model to make molds that will be used to build the new wing. Just now we are dealing with the new structural layout and design. Take a look here to see some pictures (www.demec.ufmg.br/cea). A good thing with this new wing is that we will put the airplane very close to 400kg (889lb) (empty) or even lighter.

I never did a formal comparison  with other airplanes but it is a good idea. Just give me few days to finish the structural design and I will do it.

The fuselage is flat in order to simplify the fairings and reduce wet area. 

I don't know if we will provide plans, kits, or airplanes. In fact the university will not do it, maybe a private company.

Best Regards,

Paulo Iscold

Hi Paulo

Do you want to create a new bigger aerobatic airplane with 300hp and carbon wings,or a you going to do modifications from the MEHARI CEA-309.Do you save weight with wood tail compare to a steel tail as on Lazer.It seems,that your main landing gear is made from 4130N tube with filler and fiberglass;is that true?Is it lighter.

Jean-luc

Paulo

Nice work. I have followed your work since it came published in the EAA magazine  

..PLEASE PLEASE PLEASE...keep the 4 cyl engine...AEIO-360......  several good acro rides such as the Giles 200 and 202 have had that engine for ever.....Especially with that EW of 400KG!!!!!

Any chance of seeing your aircraft sold as a kit? I'll be interested!