Performance evaluation proposal

Builders:

Here is a proposal for a comparative performance evaluation.  While it could be done for many types of aircraft, I’m primarily picturing this event taking place at the Zenith Aircraft factory’s annual Homecoming in September.  It is focused on highlighting the aircraft created by builders, and gathering data from them to assist current and future builders in making choices which tailor their projects to better suit their particular needs.

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In recent years, STOL contests have become very popular, and Zenith has run them at the Homecoming as far back as eight years ago. In national and international STOL contests, regular Zenith STOL planes have consistently demonstrated their performance and value, even against purpose built, trailered in, aircraft costing many times more.  This is good, but STOL contests only provide one facet of a planes performance, and most pilots don’t fly that way on a typical day. This performance evaluation is aimed at gathering comparative data over a much broader flight envelope, one that represents more typical use of the designs.

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Although I am an engine guru, I have grown weary of nearly every opportunity for builders to learn, being distorted into a marketing opportunity for somebody. I have spoken at many Zenith gatherings in the last 15 years, and other than the engine panel discussions, I make a point of not using the word “Corvair”,  when doing so. Marketing has a place, but it should never be allowed to displace builder camaraderie or learning.  While the very nature of the evaluation will provide accurate, useful data for comparing power plants, my goal is to provide a much broader overview of the performance potential of the designs, their utility and to specifically highlight the achievement of individual builders and encourage those currently building.

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Here are the steps a builder takes , participating in the evaluation: 

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A ) After being warmed up, the plane’s fuel tanks are topped off to the bottom of the filler necks, a level that can be visually replicated at the completion of the flight.

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B ) The plane is placed on electronic scales and weighed in, without the pilot.

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C ) Plane heads to the designated runway and takes off.  At he 800′ mark there is a very light tape spaning the runway, 6′ off the ground. Any Zenith model will clear this without difficulty, even with full tanks, but we have it to preclude anyone using a very high prop pitch setting which would skew the cross country speed evaluation.

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D ) Plane proceeds to fly a designated 3 leg course, approximately 100 miles.  Two very visible land marks are used as pylon turn points. The flight is done at a set altitude, perhaps 2,500′. There are observers at the turns, pilots make a radio call when approaching. The visual is just a back up, the data can be collected for any aircraft with a GPS with a system like this: https://www.cloudahoy.com.

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E ) The three legs are flown, the last one over flying the point of origin at 2,000′. The time to fly the course is halted there. Plane comes back to land and proceeds immediately to the fuel pumps.

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F ) The plane is re-weighed for fuel burn.  The plane is topped off, refilled to the exact same location on the filler necks, and re-weighed to confirm the fuel consumption.

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G ) Plane goes back out. It must use the exact same configuration as the cross country course, particularly the prop pitch setting.  Pilot climbs to 2,000′ and flies at a stable, level speed of 75mph for one minute. From there, he climbs at any airspeed he chooses, directly to 4,000′.  He calls on the radio, but again the performance is measured electronically.

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H ) Builders can fly the cross country portion at any pace they like, but they are encouraged to demonstrate flat out performance. I  would also like at least some of the planes to do a second run at the course completing A – F again, but at a typical cruise power setting for comparative purposes. This could be run at a single model appropriate speed, such as running the 601/650’s at 115 mph, as it would give a comparison of fuel burn rates at casual cruise setting.

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What do we get from this? Real data. If you have been in the EAA for 30 years, you can remember the CAFE foundation’s performance evaluations, published for many aircraft, in long articles in Sport Aviation. This was information I treasured. The EAA was pressured by some kit manufactures to not publish information that contradicted their marketing departments. That was a transition point of the organization being asked to serve the manufacturer and not the member. In the internet age, things have deteriorated, and quality information is even harder to find, and the hidden compensated relationships between the ‘evaluator’ and the product being harder, not easier to see. We can lament a bygone time, or we can take actions to provide our own real data. These projects have lasting value. Ask any Pietenpol builder, the W&B work done a decade ago by Ryan Meuller and myself has improved a generation of Piet’s by by giving their builders real data to plan their builds and making the operation of the design safer. It is hard to overstate the lasting effect of real, accurate information.

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Who does this serve? Builders. I speak to people potential builders who mistakenly think they must have a STOL model to fly off a 2,200′ airstrip; there are also people who float on the choice between a STOL and a Cruiser, have questions about typical builders useful loads vs factory design prototypes. The 100 mile cross countries will provide a very good look at the general potential utility of each design. Comparisons of a sustained 2,000′ climb under known conditions will answer many questions builders have. This type of data will be much more useful than pictures of glass cockpits with a single set of information.  The better data builders have going into the process, the much more likely they are to finish their plane, and they are vastly more likely to be happy with their creation.  The current data available is ok, but a lot of it is really marketing and not an evaluation. This can be corrected in one weekend, and it will have the additional benefit of being a deterrent to future excessive marketing claims.

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This will be a builder focused event. I don’t want to include data from aircraft that belong to, or were built by engine guys as demonstrators….  Between parts from myself and Dan from SPA, I can assemble a 3,550cc Corvair, and I have nearly 40 years of experience with nitrous oxide installations on all kinds of vehicles. But a $22K Corvair festooned with Fogger nozzles isn’t what I teach builders to assemble nor what we sell. It would be useful if this was a ‘contest’ but it is not, it’s an evaluation.

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Additionally, the factory planes will be left out also, because, like planes coming out of professional shops, they are not representative of current builders creations. The evaluated planes will be in the stock airframe configuration with only minor mods like fairings.

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Additionally, each plane must complete all the steps A-G. If the weight of the plane is a ‘secret’ or a plane with a very high pitched prop and poor climb performance doesn’t want section G recorded, it will not give a complete data set, and that would only serve someones ego or marketing plan, not builders.

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I value everyone’s constructive input here. Please use the comments section to add any thoughts which might improve this concept, or explain how you would find this data useful.  Thanks in advance.

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WewJr.

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