www.eaa407.org

South East Idaho Officers:

    Austin Moses, President

    Jerry Phillips, Vice President

    John Bakken, Treasurer

    Pete Stewart, Secretary

    Harold Mothersill, Website

    Dale Cresap, Newsletter

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President's Message:

It appears that we dodged a bullet when the Idaho State House of Representative's delayed passage of SB 1364, which would have mandated all gasoline to have 10% ethanol within 5 years.  Although the bill exempted aircraft fuel, I don't know any local retailers that would put in a separate tank for the few gallons I purchase each year.  I mean no disrespect towards our State Legislators, but for years the Federal and State governments have provided tax and other incentives to promote the supply side of ethanol, with very little success.  Now they seem to want to change the carrot for the stick and mandate it.  I, for one, think that when it is feasible economically and environmentally, it will succeed on its own, without all the assistance.

 

O.K., enough of my soapbox, let's get down to the business of building and flying airplanes.  Our next meeting will be March 18th, 2005, at the Blackfoot airport for a builder's tour.  We will meet at 4:00 pm at the terminal building then go to Pete Stewart's hangar at the north end of the airport to see his current project.  If you are a little late, just go down where all the cars are on the north end and join us.  After Pete's project, we view a completed Rans, also on the airport; then we will journey out to my neck of the woods in Moreland to view Terry and Natalie Bergevin's Sonex project.  Hope to see you there!

 

Our thanks go out to Ken McCune for his great program last month about flying in South America.  It was very well done and we had a great crowd.  Thanks everyone for your attendance.

Austin Moses 

 

February Meeting:

The chapter met in Idaho Falls at Aero-Mark at 6:00 PM.  The meeting was called to order by

Austin Moses.  John Bakken gave a summary of our financial status and Pete Stewart

summarized the minutes from the January meeting.

 

New Business:  Hal Johansen said that Steve Hendricks had sent him a description and pictures

of 5" wheels and tires that he has for sale: 3-5" wheels, two have axles and disc brakes, tire size

300/380X5 and a castering nose wheel 280/250X4.  The tires are Carlisle racing slicks and

appear new Selling price is open.  Any one interested should contact Hal @ 522-7297.  The next

meeting will be a project tour in Blackfoot.  Members agreed to meet at 4:00 PM instead of 6 so

we wouldn't be trying to find the locations in the dark.  Members are to meet at the FBO building

at the Blackfoot Airport .  The bring-a-buck contest was by Jim Tibbets.  The question was "What

is the highest altitude ever recorded for a bird strike?"  Answer: 36,000 ft and the bird was a

vulture.  Jim's answer was the closest at 31,000 ft.

 

Program: Ken and Lori McCune gave a presentation on backcountry flying in South America.

They had lived in South America for 13 years as members of the South American Missionary

Pilot group which is part of South American Missionary Air.  Ken flew a Stinson 108, an M-5

Maule and a Cessna 206.  All three planes were flown on both wheels and floats.  Which plane

was used depended on the weight of the mission.  Ken is also and A&P/IA and his presentation

brought home the fact that with good ol' Yankee ingenuity you can repair just about anything.

Lori said that anyone interested in reading about living in this kind of situation should read

"End of the Spear" and/or "Jungle Pilot". Ken is presently rebuilding a Cruise Air with High

School students from Driggs.  He also has a Murphy Rebel in a state of disrepair that is for sale.

 

Pete Stewart, Secretary

 

Editor’s Column:

The special YE rally with the Idaho School for the Deaf and the Blind in Gooding is set for Thursday April 20. Please reply to dale.cresap@icp.doe.gov if you will be able to fly students in this special event, and the number of seats in your plane. Thanks to all those who expressed general interest. Now the plan is coming together and we need specific commitments.

 

Technical Report

As an aircraft design and build organization, I thought the following question would be of interest to our members. Here is a question I posed, and the answers I received: Planes can be either tractors or pushers. Virtually all GA planes are tractors, both factory built and home built. There were some Rutan pusher designs that were successful, but they are a scant minority. Why is this? What are the design trades that favor tractors?

 

I think there is really only one reason for the tractor design - it is much easier to balance the plane with the engine forward of the CG considering the short moment available.  The longer moment aft of the CG demands most of the weight be forward of the CG.  Notice how little mass is available to use aft of the CG.  Look at the Cessna that has both a tractor and a pusher:  the CG is between the two engines, but still about 1/3 of the way back of the leading edge of the airplane.  Burt Rutan's designs are not so obvious because he uses a delta or swept wing design with a short fuselage, but he still has to use most of the dead weight to balance the design.  I suspect those of who build model airplanes are more sensitive to the CG than you guys who fly the "real thing", but the aerodynamics are the same.  We went to the movie "8 below" (highly recommended) and in the movie they use a plane that has a turbo prop and it looks way out of proportion because the weight to power ratio with these engines means they have less mass to use to balance the airplane so the moment forward of the GC used with the engine mass is relatively long.
Allan R. Bringhurst

 

As I was once told about 40 years ago, the air to the propeller is undisturbed for a puller prop.  Whereas, the air is disturbed by the wing for the pusher prop.  In other words the puller prop is more efficient.  The technical theory why this is the case will have to be supplied by some expert in laminar and turbulent flow theory. - Evert

 

1) Aerodynamic efficiency, usually.  For example, in a C-337 Mixmaster, the front engine is the critical engine.  Generally, you don't want the prop sitting in the turbulent wake of the fuselage.  You ought to be able to minimize this with clever design, but it would be an extra design constraint, and designing is hard enough already.

2) A tractor prop lowers the power-on stalling speed.

3) Weight distribution.  The engine is heavy.  It needs to be close to the main wing.  If you put it in the back, it almost forces you to use a canard design.

 

On the other hand:

A) A pusher results in less noise in the cabin, especially if you have centerline thrust (as opposed to engines way out on the wing).

B) A pusher makes a positive contribution to angle-of-attack stability, i.e. what pilots call trimmability.  It's like having a larger horizontal tail.  I'm quoting a "famous result" here; I haven't thought about it, and I don't have a solid understanding of how it works or why it must be true. Beware that in my experience, not all "famous results" are true.

(John Denker)

 

For a single engine plane, there are huge advantages in both structure and aerodynamics (drag) to have the prop/engine aligned with the fuselage. So do you put it in front or back? You will either have the fuselage flying through the prop wash, or the prop flying through the fuselage wash. Both would prefer to be flying through undisturbed air, but the prop has a stronger claim on it for aerodynamic efficiency.