newsletter · 2015-02-25 · february2015!! you should know that…! qwertyuiopas "...
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EWSLETTER
FEBRUARY 2015
YOU SHOULD KNOW THAT…
QWERTYUIOPAS
This month’s meeting is Thursday, February 26th, 2015 at 19h30
EAA 266 is pleased to announce that the February Meeting is about Aircraft Instruments. Our host is Mr. Paulo Nunes at Aeroneuf. The visit includes exhibits-‐ instruments information and a question and answer period. Bring your questions on aircraft instruments so our host can
help you out while you enjoy a coffee and pick up a few business cards to pass along to your aviation friends!
IMPORTANT NOTICE: THE MEETING ON FEBRUARY 26TH at 7:30 PM, WILL BE HELD OFF SITE, AT AERONEUF.
DETAILS:
COMPANY NAME: AERONEUF INSTRUMENTS LTD. WEB SITE: http://www.aeroneuf.com
CONTACT INFO: Paulo Nunes ADDRESS: 600, 3éme Ave, Laval, Quebec, H7R 4J4
DIRECTIONS: FROM THE SOUTH -‐ TAKE HWY 13 NORTH, EXIT AT BOULEVARD DAGENAIS O , GOING WEST. REMAIN ON BOULEVARD
DAGENAIS O TILL YOU REACH 3éme ave. IF YOU REACHED BOULEVARD ARTHUR SAUVÉ, YOU HAVE GONE TOO FAR! FROM THE NORTH -‐ TAKE
HWY 13 SOUTH, EXIT AT BOULEVARD DAGENAIS O, GOING WEST. REMAIN ON BOULEVARD DAGENAIS O TILL YOU REACH 3éme ave. IF YOU REACHED BOULEVARD ARTHUR SAUVÉ, YOU HAVE GONE TOO
FAR! ALSO: SEE GOOGLE MAPS FOR MORE DETAILS.
FEBRUARY 2015
QWERTYUIOPAS
Mike Lustig: President [email protected]
David Cyr: Secretary [email protected]
Ed Hannaford: Librarian [email protected]
Kris Pinnow: Vice President [email protected]
Roberto Cea Campo: Treasurer [email protected]
Michel Moreau: Membership Director [email protected]
Tony Molle: Webmaster [email protected] Nora Nikkinen: Caterer
Jasmine Molle: Editor [email protected] Frank Hofmann: Technical
Counselor [email protected]
Graham Batty: Flight Advisor [email protected]
FEBRUARY 2015
PRESIDENT’S MESSAGE Mike Lustig
Last month’s meeting featured two topics, which I found to be quite interesting. However, a snowstorm that night appears to have reduced the number of members who could attend. Noticeably, few if any members who normally commute from Ontario where there, I assume due to road conditions on the 417. The good news is that some of this disappointment can be overcome.
The first topic was the presentation of an EAA webinar entitled -‐ ADS-‐B: A Pilot's Guide -‐, followed by a brief talk by Frank Hofmann with his take on the implications of ADS-‐B for Canada. For those who missed out on this, here is a link to the EAA webinar.
http://www.eaavideo.org/video.aspx?v=3990999242001
(It is not known how long it will be still available)
After the break, Bill Evans gave a presentation on the design and construction of Hoerner wing tip fuel tanks for the Sonerai II. Included in the presentation. Accompanying the presentation was a 13 min. video Bill and I made showing the various steps in the wingtip construction. This video has now made it to YouTube, garnering (as of Feb 18) 176 views, one “Like” and one new subscriber to the channel. Here is the link for those who missed it: https://www.youtube.com/watch?v=jgvLQ1flt1s. Clearly, Bill has the makings of a successful homebuilding vlogger!
Best Regards to All,
Mike Lustig
President
Submitted by Past President Michel Moreau; Feelings shared by all of us:
“It is with great sadness that we learnt our friend Roberto Cea-‐Campo’s tragic loss of his loved little girl Daniela.
Our thoughts are with him and his family.
We hope that he will recover his “joie de vivre” and love of flying but we know that it will take time.
We love you Roberto!”
FEBRUARY 2015
MICRO CONTROLLERS FOR AN INEXPENSIVE INSTRUMENT PANEL David Cyr
Two years ago I started helping Tony Molle with the electrical wiring of his Lancair 360. Aside from the learning curve involved with a sophisticated aircraft with glass panel technology, electric/hydraulic retractable gear, electric flaps, etc., we ran into an incompatibility between the capacitive fuel probes and the Grand Rapids EFIS. The output of the probes is a variable frequency square wave, while the EFIS display wants a variable DC voltage proportional to fuel level.
So, to address the problem, I decided to resurrect my teenage amateur radio electronics hobby to see if we could build an interface. Fortunately, technology has evolved somewhat since then; from vacuum tubes to integrated circuits and inexpensive micro computer controllers. A quick search of the Internet turned up an integrated circuit that does variable frequency to voltage conversion. Using this IC, we built 3 circuits for the two wing tanks and the header tank.
Then I learned that Tony had a Dynon heated Pitot probe that also has an angle of attack port to allow display of AoA; but only if you have a Dynon EFIS of course! The Grand Rapids EFIS does not support this Pitot/AoA probe.
Note the small hole on the bevelled lower face of the Pitot probe
Wouldn’t it nice if we could take advantage of this probe to display angle of attack? Commercially available indicators sell for $1500 and up, and one unit seen at Oshkosh in 2013 didn’t even take into account the speed of the aircraft, even though an aircraft can stall at a much higher airspeed than the “advertised” or understood stall speed if the it is heavily loaded or flying with high “G” loading, as in a steep turn or pulling hard out of a dive.
Well, it shouldn’t be all that hard to build the logic to calculate and display AoA on the instrument panel… A friend in the business of designing drone navigation and control systems suggested a micro controller would be the best approach, but this was unknown territory to me, so I designed
FEBRUARY 2015
and built a discrete component AoA indicator. However, adjusting the 6 potentiometers (variable resistors) turned out to be impossible.
The failed attempt to build an AoA using discrete components and a 10-‐segment LED
So, let’s take the earlier advice and try a micro controller even though it involves a steep learning curve with a new programming language, understanding dozens of new acronyms and hardware characteristics to make sure various components are compatible. Since the cost of an Arduino micro controller and an LCD display is about $12 including shipping, the investment is minimal. The Pitot tube is the only expensive item at about $200.
We could program the AoA calculation using a table of values from empirical data (actual measurement), but we looked at the math first to see if that might work. My trigonometry was rusty at best, however, with help from my airplane building buddy, George Heintzman, I think we have it figured out. Let’s assume we have a Pitot with a second port below and behind the tip on an angled surface as shown in the diagram below, as is the case with the Dynon Angle of Attack Pitot probe.
PPitot = Pitot pressure PAoA = Angle of Attack pressure
FEBRUARY 2015
The formula for air pressure as a function of speed is:
P = ½ ρ V2 where ρ is air density and V is velocity
PPitot = ½ ρ (V cosθ)2
where θ (theta) is the actual angle of attack and cosine is involved because the Pitot angle into the oncoming air changes with AoA
PAoA = ½ ρ (V sin2(30° + θ)) or cos2(60° -‐ θ)
where the surface with the AoA port is 60° “out of the wind”
PAoA / PPitot = sin2(30° + θ) / cos2θ or cos2(60° -‐ θ) / cos2θ
We can measure both PAoA and PPitot with differential pressure sensors. MPXV7002 Differential Pressure Sensor measures up to 2 kPascals for the AoA port and MPXV7007 is rated to 7 kPascals or 232 mph. Now since we don’t know the angle of attack, and that is what we want to solve for, we have to either develop the formula for θ (angle of attack), or we can iteratively substitute the value of θ to match the pressure ratio of PAoA / PPitot . So we propose an angle and compute the pressure ratio PAoA / PPitot and compare this to the measured value from the pressure sensors. If the difference is positive, we subtract a portion of the error from the proposed AoA and recompute the pressure ratio. If the difference is negative, we add… After several iterations, we converge on the true AoA. This result is displayed on the 10-‐segment LED display along with an audible warning in the headset or with a simple buzzer.
This method of calculating AoA is independent of air density, temperature, altitude, etc, because the wings and the pressure probes “see” the air the same way. Thus no compensation is required for any of these variables.
Now that the hardware and software are done, we need to package it all. Even that is provided in the form of 3D print files that are ready to go. Airborne testing this spring.
FEBRUARY 2015
Currently the Arduino-‐based AoA indicator is in breadboard format with syringes providing the air pressure to simulate the Pitot and AoA inputs. By the time we’re ready to go flying, the Arduino, the “keyboard” and the circuit with the pressure sensors and power supply will be will be completely enclosed in the box shown above with the 10-‐segment LED showing through the end of this enclosure.
Enclosure for Arduino controller Micro controller and debugging display
FEBRUARY 2015
The interesting thing about all this is the revelation that anyone can make an affordable AoA indicator or most any other instrument that appears on the panel. There are online forums that offer free code for many instruments so there is very little work required unless you want to customize or combine instruments on a glass panel display. You will easily find controllers, special function peripherals and software for instruments like an artificial horizon, air speed, altimeter, VSI, directional gyro compass, tachometer, oil temperature, oil pressure, fuel level, etc. With some study and research, there is the opportunity to populate your panel with state-‐of-‐the-‐art instruments at a fraction of the price of conventional instruments.
David Cyr
FEBRUARY 2015
Presented above for your enjoyment is an extract from Jane's Pocket Book of Home-‐built Aircraft, Copyright 1977 by Michael J.H. Taylor. This aircraft, the Issacs Fury II, is representative of many homebuilt aircraft designs from around the world that have remained popular for decades. Please
note that the sales and mailing information is from 1977.
FEBRUARY 2015
CLASSIFIEDS Free Ads for Paying Members
For Sale: Hangar doors (sliding) complete with rails for 40 foot hangar. Door height is 11'5½" all metal. As removed from hangar at Cornwall. $1200.00. Ed Hannaford. [email protected]
For Sale: 1 ea. H -‐ Type shoulder harness 2 inch, black with metal to metal fittings. New never used, from Aircraft Spruce, no lap belts, $100.00. [email protected]
For Donation: Vari-‐viggen Ruttan, designed by Burt Rutanu inspired by the SAAB 37 Viggen. It is 60% complete with almost everything you need to complete, except the engine and the propeller. Located at the airport of Louiseville, QC. CSJ4. Gaston Girard 438-‐495-‐5253.
Seeking: Active aircraft builder looking for old projects or materials. Specialized in old wood aircrafts and restoration. Ron Gosselin 514 8081808 -‐ [email protected]
For Sale: 1946 Aeronca 7ac. Continental A65 engine. Mid time engine. 2450 TT. Slick magnetos. New Fabric. Long range fuel -‐ 5 Gal. New tires, main & tail. Maul Tundra tailwheel. Engine and windscreen covers included. Beauty to fly. 9/10 inside and out. Asking $22,900. 514 636 8101 or E-‐Mail: [email protected]