Our industry does a great job in presenting the amateur builder with flight proven designs which are fun and, for the most part, reasonable to build. The "Experimental" category aircraft tend to be of higher performance and efficiency, at times significantly more so, than anything available from the "certified" marketplace. Along with these features the safety records of amateur built craft are often as good if not better than their established production counterparts. But, as in other industries, here too it is unfortunately not uncommon to come across situations and decisions which result in substandard products. The difference however between aviation and other sectors is that if you make a design error or fabricate a poor part for a car for instance, the buyer may get a lemon but in general life is not at risk. On the other hand, when parts are supplied for aircraft use, it is most important to exercise a level of caution not often seen in other products and professions.
But while controls can be put in place for many mechanical operations, it is difficult to overcome ignorance, especially when combined with ingrained attitudes, prejudices and egos, of the people actually manning the lines. To complicate things further, when these effects are part of the company’s management, the whole organization is put at risk. When applied to design, engineering and manufacturing, these "human factors" will often lead to the detriment of the product’s quality and durability before it ever leaves the door.
Having been in the aerospace industry for over seventeen years as a configurator and structural design engineer, the last ten devoted nearly exclusively to general aviation and the "Experimental" industry, I have seen several examples of decisions which I felt were made using ego and "the good old eyeball", with only a minimum of information or experience, rather than hard data and established design guidelines. The resulting designs or parts, while not always dangerous, could have been better and/or safer with only a minor amount of extra effort. With the exception of a few cases, each item on its own did not represent a catastrophe waiting to happen, but looking at all the items together indicated a trend which I felt more companies should consciously address before bringing their products to market.
The actual impetus for writing this came as a result of one of my earlier articles (Reduction Drives: An Engineering Perspective, Sport Aviation - November '92) in which I came out somewhat critical of reduction drive suppliers and the lack of engineering savvy our company encountered in searching for candidate systems for one of our engine projects. In writing an article that’s critical of a product or business, an author takes a chance of alienating those readers who have formed emotional ties to that section of the market. This is especially true in a niche industry such as ours where individuals often develop strong opinions and loyalties. Imagine my surprise then when out of over sixty letters and phone calls only one was negative (a reduction supplier), one was a little of both, and the rest were very positive and reaffirming. The respondents ranged from pilots and aircraft owners to engineers.
The common theme in the responses was the feeling that some suppliers to our industry seem to hide behind the "Experimental" label, as if it was an excuse for not doing all that was reasonably possible to assure the safest product. Now, does this mean that people expect suppliers to have large design staffs, testing their product(s) for years before bringing them to market? Of course not. Neither was any form of certification or regulation suggested - let's face it, we're in this industry to get away from all that bureaucracy. But in the same breath it is clear that many individuals would like to see more responsible design work and documentation in producing aircraft and their components, and a more responsible presentation of applicable data to the market’s prospective customers.
In the course of these discussions a number of individuals thought it would be appropriate to generate an article which would list a set of examples illustrating some of the questionable decisions and practices. But, as I write this, I think its also important to say that the purpose of this piece is not to condemn our industry, nor any companies or individuals in it; it is only to submit for review a few situations to which I have been a first hand witness, situations which may have affected the parts you buy.
As in most markets, the purchaser should be aware of the product, and the technology necessary for its development, in order to make a sound and informed choice. This of course doesn’t mean that we should all be engineers, but a good helping of common sense is necessary in order to be able to discern between those who are trying to provide a good product and those that have a good dog and pony show and are trying to peddle something less than adequate. If the customer doesn’t feel that he or she is qualified to make that judgment, it might be a good idea to be represented by someone who can.
But, on the other hand, we must be fair to the suppliers also. They cannot open their books and design documentation to everyone who walks through the door. First of all they’d need a separate staff just to handle the customer questions. Secondly, they have a self preservation interest in protecting their proprietary work. Opening their technical information to anybody who walks through the front door is just not good policy. In short, companies must be able to substantiate their product, but at the same time, they must balance responsibility and openness to customers with protecting their interests and intellectual information.
The companies and/or individuals in the following examples range in experience from relatively new ventures to well established and known organizations, located all over the United States and Canada, providing equipment and services ranging from reduction drives to airframe kits. None of these cases are hearsay or rumor - I was a first hand witness to each one, or in one instance, have interviewed the key individuals involved in the incidents.
Example 1 - In discussing a reduction drive design with one supplier I asked which material is used for the gears, so that I could determine the toughness and durability of the components for myself. The owner of the company replied "It’s a good, tough gear material". Wanting a bit more data than that, I then asked which one. The owner replied "It’s a good tough material which we’ve been buying for a while now, but I don’t know which one off hand". A few questions later it was pretty clear that I was not going to get the information I needed so I changed the subject to other parts of the design.
Some time later however I discovered that the company doesn’t make the gears but buys them from an outside source. Furthermore they aren’t cut, instead they’re powdered metal (sintered) gears as used in the automotive industry. While this is not necessarily bad, a truthful answer would have given me more confidence about the company and the individual.
But further discussions with this gentleman revealed that although he was a machinist with substantial experience, he had no engineering background nor did anyone else associated with his company. He had no understanding of fatigue or endurance criteria, the effects of propeller flight loads, nor why a simple static run was not enough of a substantiation to prove the design. His final argument was that a customer bought his drive, installed it on his airplane there at the factory and, after a few short tests, flew it almost five hours to his home field. When questioned as to how he knew the same drive would hold up beyond the five or ten hours, to fifty or five hundred hours, he hung up.
In essence, the result of this attitude is that the customer becomes an involuntary test pilot for the developer - something I’m sure many of us would not want to be. Overall we were very surprised to find that many reduction drive suppliers have little or no engineering capability, almost solely depending on "eyeball" design and some level of machining or manufacturing experience to develop this relatively critical part of the aircraft powerplant.
Having been a machinist for a number of years before getting my engineering education, I have often said that I would prefer to have as an employee a machinist who knows the design process rather than a staff of engineers who have little or no fabrication experience. Many industries are plagued by problems associated with over-engineered items which cannot be made due to the lack of understanding and foresight of the manufacturing process.
But, at the same time, I would never wish to depend on a product that had no engineering design or analysis to back it up. The experienced fabricator or machinist may have the expertise to design a functional reduction drive but in general he does not have the background or experience to prove the drive's reliability, its life expectancy and its functionality at other than ideal conditions. Manufacturing know-how is important and critical to the development process, but is only a small part of the products' design, analysis and substantiation. Imagine an individual who designs an outwardly good looking airplane but neglects to take into account the effect of gust loading on the wing structure, or the effect of an extended fairing on the stability envelope - the airplane may be functional but at some point down the line could provide the owner with a nasty surprise. Responsible engineering needs to be a primary part of the development process regardless of the product. "Eyeball" designs rarely pass the test of time.
Situations such as this often remind me of the phrase "Buyer Beware!", especially in this marketplace where the product you buy may have a significant effect on the rest of your life. Personally I don’t think this attitude is too wide spread but it is not uncommon at times for a company’s enthusiasm (translated "owner’s ego") in presenting their product to the market to go a bit beyond the reasonable limits of the product. The following example illustrates an extreme case of this "enthusiasm".
Example 2 - Another drive design we considered for our project was being advertised suitable for applications up to 250 horsepower. This company puts on a good show with its high tech appearance of computerized operations and has individuals who, for the most part, sound authoritative in the field of engines and reduction drives. Most people who’ve gone through the premises are impressed with their technological prowess and thus are convinced of their expertise.
Personally, I always though this drive sounded suspiciously too light for the horsepower range advertised so I requested a couple drawings and key components of the box so I could analyze them for myself. Surprisingly enough the information and components were provided. As I expected, the analysis showed my concerns to be valid: Due to a number of very basic design errors (sharp decreases in shaft diameter, reaction bearings too close to each other, case too thin and fabricated from cast aluminum rather than machined from billet) the analysis determined that the drive was sufficient for no more than 90 horsepower with a propeller weighing no more than fifteen pounds.
Upon reading the analysis report, the company’s owner suggested that I was too conservative in my flight load assumptions (our requirements were for a wide variety of flight and propeller loads) and that for the average airplane the numbers could be somewhat higher. I agreed but since I also ran numbers for a less conservative case I cautioned that the change would add at most only twenty horsepower to the power rating and less than ten pounds to the allowable prop weight. At the time he seemed to agree but within a week, in my presence, the owner boasted to visiting customers about his 250 horsepower gear box.
Recently the same company was visited by a well known flight demonstration pilot who was searching for a reduction drive for one of his airplanes, along with a friend who was a gear system design engineer for Pratt and Whitney. Within seven minutes of entering the door, the engineer heard enough "horse hooey" to walk out of the meeting and recommend to his pilot friend not to have any further associations with this organization.
But reduction drive suppliers aren’t the only entities with examples of human factors entering the process. The same type of questionable decisions just discussed are in evidence throughout the industry, including the airframe suppliers. The following are examples from a couple of kit producers. In each case decisions were made which have, or could have had serious consequences.
Example 3 - In order to get into kit production, a company bought a two place kit, built it, then copied the design incorporating a number of modifications to accommodate four seats. To an aircraft designer the copy was obvious since design errors of the first aircraft were incorporated into the new one. Since the company owner tended to hire only younger, less experienced engineers who tended not to contradict his decisions, very little core engineering analysis was done prior to the flight of the first prototype. This resulted in an airplane that was plagued by structural and flight problems including a tendency for tail flutter, poor horizontal tail effectiveness, fuselage flow separation and spar carry-through failure.
To complicate things further, a few years ago the company falsified the flight test logbooks of their new prototype in order to meet a demonstration schedule. The chief engineer (an FAA DER) at the time insisted that the log record be corrected or his duty would be to report the discrepancy to the FAA. The gentleman was fired. Within a few weeks of this action the aircraft crashed due to an in-flight structural failure, killing the occupants (the first prototype also crashed but with no fatalities).
Soon thereafter the company went out of business and was to be sold to interested investors. One of these investor groups called me to get more information on the airplane and to get an idea of what type of engineering would be required to fix some of the problems. After going through their list it was clear that the buyers did not have a complete story on the airplane. They however were still interested in purchasing the kit company but felt that not all the problems needed to be addressed. Our conversation ended with the representative making this statement: "... and besides, it’s an "Experimental" category airplane. The individuals buying the kit know that there’s an element of risk."
Unfortunately, as scary and irresponsible as the statement sounds, in essence it is correct: The amateur built aircraft owner does take a chance in purchasing and building a kit, putting faith in the quality of the factory’s design and in his (or her) fabrication ability, to minimize the operational risk of the craft. The key question to ask then is: "How high should this risk be?"
With the maturing of the kit built industry, the allowable risk seems to be reduced markedly, in most cases to the point that errors are becoming more a function of construction quality rather than component design and fabrication. It is therefore, in my opinion, a negligent decision to ignore a number of known design flaws, assigning them instead to the "element of risk".
A variation of the last example is where decisions are made based on production costs or schedules rather than engineering analysis or part quality. This often occurs when the original developers are out of the loop of day to day operations and cannot be present to assure the continued reputation of their product.
Example 4 - In composite construction a part often has some amount of excess material (flashing) which needs to be trimmed prior to shipping. One company supplies pre-molded spars which are trimmed with an angle grinder, a tool commonly used in welding production. On one occasion the person trimming the flashing momentarily lost control of the grinder and accidentally ground a substantial gouge across the unidirectional fibers in the spar cap. This resulted not only in a 1/8" deep groove across the cap but also in creating a sharp edged stress concentration which could potentially initiate a crack in the spar.
The grinder operator, to his credit, reported the damage to his supervisor, who examined the part and suggested it be scrapped for obvious safety reasons. To double-check, the quality inspector was also brought in - she also recommended scrapping.
The plant manager was notified in order to approve the removal of the part. He however was of the opinion that the part was too expensive to scrap and recommended that it be cosmetically fixed and shipped. To double-check this he called the senior engineer and asked for an opinion. The individual inspected the part and recommended scrapping. The manager (not an engineer) however over-rode this decision by insisting that the part be somehow fixed and shipped anyway.
Other inconsistencies encountered in this company included little or no engineering documentation of the design, many critical parts "eyeballed" for prototype then considered "good enough" for production, material properties and technical information ignored - material selection was based on cost more than applicability, and poor manufacturing specifications resulting in mismatched parts or components with poor fit.
A manufacturer, especially one in our industry, that does not heed its engineering and manufacturing staff puts everyone connected with the company in a serious liability risk, one that could cost a lot more than a scrapped part.
So, those are four examples showing that regardless of the best intentions, lack of sound judgment can result in a risk for the buyer. The good news however, is that there are many component and airframe suppliers who truly want to serve their customers in not only providing good and safe parts but also in providing excellent technical support. Since I started this article with what in my opinion were examples of bad human factor influences, I’ll finish with a couple of examples of where I think individuals and companies have done a good job.
One of the best ways to guarantee a satisfied kit building customer is to provide him (or her) with quality parts. By that I mean that the parts not only have to look good but they must fit well too. At times this is not always easy (as many builders will probably attest) especially with composite materials where curing and shrinkage continues well after removal from the mold, often resulting in slightly distorted parts. It is therefore pleasant to find kit components which assemble right the first time with a minimum of fuss and grinding. In my experience, some of the best composite components I’ve seen came with the Wheeler Express kit, an impressive feat considering the wet lay-up techniques the company was using. A few years ago I helped assemble a set of Wheeler wings for a customer and was very impressed with the part quality, fit, and marking. With two of us working part time we had both wing panels assembled, plumbed and closed off within two weeks. Other, more serious issues aside, part quality was certainly not an area of complaint for this airplane.
Using prepregs and elevated temperature cures, Lancair also delivers professional looking components which provide their customers with a minimum of assembly fussing. According to a number of local builders I’ve been in contact with, the kits go together well, with only a few occasions of minor misfits. The only significant and ongoing complaint I hear from Lancair builders is that the documentation does not have much dimensional information, leaving many positioning decisions up to the builders. Those most sensitive to this situation are engineers who are used to a higher level of specifications in their jobs and thus expect the same amount of information in the kit instructions also.
Speaking of documentation, along with quality parts, a good kit should also have concise and clear assembly instructions. My choice for the best manual is Glasair’s. The writing is very clear and detailed, accompanied by excellent photos and illustrations. The technical drawings, including exploded views and assembly views, in the manual are some of the best I’ve seen. The Glasair is a complex and time consuming kit, but the excellent manual makes the assembly job somewhat easier.
But of course composite airplanes are not the only ones out there. For many years kit manufacturers of metal airplanes only provided a material bundle, leaving the greater majority of the fabrication up to the builder. But due to demand, the parts provided for metal kit builders have been steadily increasing in quantity and quality over the past few years, to the point where many suppliers provide parts with which the builders have little or no problem working. Although not "all metal", most builders I’ve talked to seem to agree that the Christen Eagle has set the standard for kit quality and manual completeness years ahead of others in the arena. Many with whom I discussed the subject feel that this tube and fabric kit was so well documented and complete that no one has as of yet met or surpassed the overall quality at any price.
The highest quality and the most complete "all metal" kit I’ve seen is that of Murphy Aircraft Manufacturing, Ltd. company’s Rebel. Having on a number of occasions talked to their engineers, and having seen their manufacturing capabilities and of course the resultant kits, I must say that this company provides an airplane with excellent structural integrity and almost an "Erector Set" ease of assembly. If I was to build a metal airplane, this would be it.
Looking at a higher performance level I also like the RV series (specifically the RV-4) but since until recently their kit has been only a material bundle, I still have to go with the Murphy Rebel for kit quality and completeness.
Another kit, similar in size to the Rebel, whose design team should be recognized for a job well done, is that of the Glastar. Recently I poked my head in at Glasair to purchase some raw materials. While waiting for the order to be filled I took a close look at one of the Glastar kits being packaged prior to shipping. The hybrid structure uses a combination of composites, welded tube and riveted aluminum to form a light, yet durable structural combination. Although I haven’t seen the assembly manual, the overall feeling the kit gave me is that it is a simple, yet quality airplane which gives the impression of relatively easy fabrication. In general, I think that this airplane will deliver safety, configuration flexibility and reasonable performance to the recreational pilot, thus filling a long empty low end niche. On a personal note I think they could’ve done a better aesthetic job with the vertical tail but overall I think it’s a pleasing airplane.
As far as composite kits are concerned I won’t list a best overall since I might be a bit prejudiced. For years now I’ve been looking for a composite airplane to build but haven’t yet found one I like enough to buy therefore, last year my company decided to do one of our. I’d like to think that we’d be the best composite kit but only time and the marketplace will tell.
In conclusion, I think that most individuals and organizations serving our industry want to provide the best product they can, minimizing the effects of "human factors" on their products. However, it is still important for the buyer to discern between quality and glitz, after all, most of us don’t want to be "volunteered" test pilots. If you don’t feel you can make that judgment or if you feel a bit uneasy about the sales pitch the marketing department may be giving you, get someone to ask the necessary questions for you. If the company declines to provide the information or you’re not satisfied with the answer, it might be best to just walk away and look somewhere else. Fortunately, in our market you usually don’t have to look too far.