i believe that most people here decide upon a particular aircraft and then choose an appropriate engine for that aircraft? How many others pick a particular engine for a variety of reasons and then seek out an aircraft that is suitable for that chosen engine?
Cart before the horse?
- Thread starter TerryM76
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D Hillberg
Well-Known Member
I pick a line of power plants then design the airframe - mission, materials, mechanics
Excellent question! I was researching the Corvair conversions quite seriously when I decided to quit flying two strokes. At that time William Wynne was about the only one that was seriously in the Corvair game and was flying a Zenith 601XL with a Corvair conversion on it. I followed that development closely and watched others that were flying Corvair power.
I considered building a Zenith 601 but a couple of the design features put me off of it i.e. the thin wing skins that would "oil can" in the heat of the day, the lack of roll over protection for the occupants, and the reclined seating position. Later would come the famous "folding wing" problems but that was after I had already decided not to go that way.
I ended up with a VW powered Sonex and for reasons I won't get into on a public forum I found it not to be the airplane I wanted. I loved the handling characteristics but the performance could be lethargic at times. For various reasons it needed a different engine on the nose.
Early on I seen a Corvair engine mounted to a Sonex air frame and it was quite nicely done. Performance was really good but Dan Weseman was the designer that really took a clean sheet approach to a successful marriage of the Corvair engine to the Sonex air frame. This is, in my not so humble opinion , the engine that the Sonex air frame needs. I began with the Corvair mostly from an economical standpoint and have since learned that these engines, when properly converted, installed, and maintained, are quite reliable, smooth, and make this particular air frame come alive. It will never be endorsed or supported by the kit manufacturer and is quite verboten in their world. That is to their shame.
Apologies for the long essay!
I considered building a Zenith 601 but a couple of the design features put me off of it i.e. the thin wing skins that would "oil can" in the heat of the day, the lack of roll over protection for the occupants, and the reclined seating position. Later would come the famous "folding wing" problems but that was after I had already decided not to go that way.
I ended up with a VW powered Sonex and for reasons I won't get into on a public forum I found it not to be the airplane I wanted. I loved the handling characteristics but the performance could be lethargic at times. For various reasons it needed a different engine on the nose.
Early on I seen a Corvair engine mounted to a Sonex air frame and it was quite nicely done. Performance was really good but Dan Weseman was the designer that really took a clean sheet approach to a successful marriage of the Corvair engine to the Sonex air frame. This is, in my not so humble opinion , the engine that the Sonex air frame needs. I began with the Corvair mostly from an economical standpoint and have since learned that these engines, when properly converted, installed, and maintained, are quite reliable, smooth, and make this particular air frame come alive. It will never be endorsed or supported by the kit manufacturer and is quite verboten in their world. That is to their shame.
Apologies for the long essay!
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TFF
Well-Known Member
Inheriting an engine might make one push for certain decisions. If you gave me a Lycoming O-145 I would either build an original Pitts S1 or a single seat Parasol. You gave me a Continental 470, I would probably be calling Bearhawk the next best thing. 540 would be Pitts S1-11B. Lycoming four would be the hardest because so many great designs. Corvair would be a parasol. VW would probably be a Sonerai. I have moods of what just seems right. Definitely not going to try and make a RV8 fly on a 1/2 VW.
Well with me it was. I got a couple of horses (Corvair and VW) and many choices for a sturdy Cart (Starduster, Taylor -mono, Mustang II , PDQ, and it was best for me to take what power plant I know and have wrench time on and match to Cart on hand. Like most horses ya got to keep in mind how much you have to feed it and how hard to replace and the Cart how much weight can it hall. Most folks have a good horse first and look for a Cart depending on what task is at hand. If I was to build another Cart I'd first get a good horse and see just how many bottom plow it could pull.
Aircraft or engine is largely irrelevant. "Mission" is the prime requirement. Pick the mission, then choose the best of the aircraft that will satisfy that mission.
Over the years I have developed certain prejudices toward certain engines. I've noticed that if an airframe is limited to one specific Powerplant that is not favorable to me then I am less interested in that aircraft......must be an age thing or Ive used too much MEK over the years. There are certainly way more aircraft designs available than different engines and in my eyes the engine is the horse and airplane is the cart.
Mission requirements will certainly dictate the aircraft to be used and many performance factors will be influenced by engine choices. Fortunately one specific engine can be utilized across several different mission requirements. My thoughts are toward cross-utilization for an aircraft design so therefore it isn't going to be the best choice for any particular mission. Engine choice for me is based on reliability, affordability, availability and adaptability to the airframes of interest.
I had a handful of different designs I was thinking of building when I was given a 1/2 VW. Since the Hummelbird was on my list and it uses a 1/2 VW, that's what I have been building. Had that not happened, I may have built something else, but would have definitely started later.
I also have been since given a McCulloch O-100 (2 stroke, 72 hp, 78 lbs) that I might use on whatever I build/buy next (Rans S-9 Chaos would probably be a good match), or might end up in the Hummelbird if I ever get bored with it.
I also have been since given a McCulloch O-100 (2 stroke, 72 hp, 78 lbs) that I might use on whatever I build/buy next (Rans S-9 Chaos would probably be a good match), or might end up in the Hummelbird if I ever get bored with it.
could not start detail design until I had an engine. I had to know how much it was going to weigh to configure the rest of the fuselage.
There have been a number of airframes designed around a particular engine, then that engine went out of production! Jabiru is one example where they were stuck with an airframe specifically designed for the KFM112 engine. When the Italians pulled the plug, Jabiru pretty much had no choice but to design their own engine to fit the now certified airframe.
I think it is better if an airframe can accommodate more that one engine, especially if the engine is not a Lycoming, Continental, Rotax, VW or any other engine configuration out there in large numbers or is not available from multiple suppliers.
I think it is better if an airframe can accommodate more that one engine, especially if the engine is not a Lycoming, Continental, Rotax, VW or any other engine configuration out there in large numbers or is not available from multiple suppliers.
If it is a "one off" design and you have the engine already, might as well run with it. That it is experimental it is not such a big issue to change the engine and air-frame as necessary when it comes time to change the engine. If you plan to sell plans, or kits then that is a different matter.
TFF
Well-Known Member
If you go too deep into specialized components like engines, you have to be ready to loose the airplane to parts that can never be sourced again. It’s ok if you want to be cutting edge. It’s not ok if it has to last decades. Going straight to the Smithsonian, who cares. Flying your family around for sunset flights, you want to sustain.
