In our experience, there are many methods that prospective customers have used in the past. A few include:

  1. Reading a magazine article on a particular machine
  2. Sending for a brochure or video
  3. Talking to a salesman
  4. Talking to the builder of a particular machine

These are all good ideas, however we believe there is an even better way. It is not a quick and easy method, but it will unquestionably yield good results. It's still based on the question and answer method, but with a computational twist. It's performed in two parts. (a) We will provide a list of the right questions to ask and comment on the answers you might receive, & (B) we will then provide you with a very novel comparison formula. If you knew nothing about kit helicopters before you read this, by the time you're finished you should be able to evaluate relative quality right along with the experts. We'll begin by listing the areas we are concerned about.

I. The history and track record of the design and flight-test team. (This might be only one person, in the kit business)

II. The evolution of the prototype.

III. The performance and longevity parameters of the machine.

IV. What is supplied in the kit, what's the quality level, what kind of Instructions?

V. What is the cost of the kit and how do you pay for it.

VI. How and by whom is this kit manufactured and what is the level of in-process quality control?

VII. What final check out service is performed or available? Next is a list of the correct type of questions to ask for each area. We will also comment on the type of answer you might receive and how to evaluate it. Ok, we told you this was not going to be quick or easy, but just hang in there. You may want to copy these questions, because they can be asked word for word. If you're an engineer, you might re-phrase some of the technical ones, however if you're not, you will probably want to ask them verbatim.

Group I Questions:

    1. Who did the original design and when?
    2. How long was the designer involved in helicopters before this design? How many helicopter designs is he responsible for and what are the gross weights?
    3. Was the designer also the test pilot or not?
    4. If the flight test program was not performed by the designer was the test pilot truly a "Test Pilot".


  • Any capable helicopter designer has paid his dues and has a long history of involvement.
  • It takes a while to explain why, but in the kit helicopter business, the designer needs to also be the test pilot.
  • A wide spectrum of gross weights signifies a designer with broader experience, i.e. from say 600 lbs. to 3000 lbs.
  • If a test pilot was employed, he needs to be a true "Experimental Test Pilot", not just a helicopter pilot with 5000 or more hours. This is a lengthy subject but if the designer is the test pilot, he does not need a great deal of flight experience. It's just the extreme opposite for the hired "Test Pilot". (Maybe we should make the reason for this the subject of a future question.)

Group II Questions:

    1. What kind of rotor hub system is used? What type of blade retention Is utilized? How are the centrifugal force loads dealt with?
    2. What is the safety factor in the blade retention area?
    3. What materials are used in the rotor blades?
    4. Is a geared main transmission utilized? If so, are the gears designed and produced specifically for this application or not?
    5. What type of crashworthiness testing has been performed?
    6. How much component longevity testing has been done? How are component lifetimes going to be finally determined and how will that information be made available?
    7. What power plant modifications have been made to get the engine working properly in this design?
    8. How much routine maintenance is necessary and how does the designer or company know this for sure.


    • A design utilizing surplus or timed out parts from other helicopters is not a good idea, but it takes a very experienced designer to come up with a new high quality rotor hub system.
    • Ball bearings are not the best solution for dealing with high blade centrifugal force loads.
    • Rotor cross section areas near the root should provide an 8 to 1 safety factor, not 4 to 1.
    • Blade materials should not be mixed. Aluminum spars with wrap around composite skins are questionable. 6061-T6 aluminum alloy belongs in window frames, not on helicopter blades. Helicopter blades, if aluminum must be 2024-T351 or 7075-T6. Blades formed of a one piece metal extrusion must be carefully avoided on powered shaft machines.
    • Automotive gears are not suited for helicopter spiral bevel geared main transmissions. Single spur gears are not used in commercial helicopter transmissions. If spur gears are used, they are in planetary form where 3 or more small spur gears engage the drive gear.
    • Drop testing is required to meet FAA type certification requirements. Can the designer or company provide you with photo proof of this type of testing?
    • It takes five times or more as long to log hours on a new rotorcraft than it does on a fixed wing. It's a big job to fly, tear down, inspect and reassemble the hub & gearboxes every 5-10 hours for the first 100-150 hours of flight on a brand new rotorcraft. If a salesman flippantly gives you some impressively large number, be very cautious.
    • Long term high component lifetimes must be determined by the factory and possibly a few other customers who may desire to participate in the extended hours program. The data from this operational testing must be shared with all operators regularly. No operator is allowed to exceed the current hourly limit, which was previously established by the test group. This information is easily disseminated these days through a web site.
    • Power plant installation in a helicopter is several times as difficult as in a fixed wing. The power take off and clutching system requires extensive testing. Vibration analysis to determine that no harmful effects are being transferred to the power plant crankshaft is vital. Engine cooling capability in a hover at gross weight in hot weather is always a tough problem to solve. A fixed wing at high power is moving fast, so it's easy to shed BTU's. It's just the opposite in a whirly bird.
    • If you build a kit helicopter and find out when you start to operate it that you have to work on it 3 or 4 hours for every hour of flight, don't be surprised. The first generation of kit helicopters, including my original Scorpion and EXEC designs were no better. The second generation of kit designs including the HELICYCLEŠ strive to model the ultra-low maintenance of the R-22.

Group III Questions:

    1. What's the power to weight ratio?
    2. What altitude can the ship hover IGE (in ground effect) at or near gross weight?
    3. What seat load specification was the ship designed for?
    4. What is the overall vibration level at maximum cruise speed?
    5. What is the percentage of increase from normal cruise speed to maximum speed in level flight at gross weight?


    • A 10 to 1 power to weight ratio will allow in ground effect operation at relatively low altitudes i.e.: 4000/6000 ft. a 7.5 / 1 ratio like the Hughes 500 will provide great performance at high altitudes like 9000/11000 ft. A recent kit helicopter, which enjoyed brief popularity, had a ratio of 12 / 1. If customers had only asked this question up front
    • Performance specifications on type-certificated machines have to be verifiable. The list of specifications you read for most kit helicopters could be what ever the sales team decides will sell. Use some common sense here. High cruise speeds and high altitude performance are not generated by low power to weight ratios.
    • The FAA considers a 175-lb. pilot to be the norm. If a helicopter is designed around this number and a 220-lb. pilot flies it, the fatigue life on highly loaded components would be dramatically effected.
    • Vibration isolation in any helicopter is a very complex task. When the source is determined, it's not always easy to attenuate or get rid of it. It usually takes extensive redesign. It's the designer's responsibility to take care of this issue during the design and testing phase. If the designer is not the test pilot, needed refinements might not have been attended to. Please understand we are not talking about rotor static or dynamic vibrations here. These are easily adjusted during and after the construction phase. A kit helicopter builder should not deceive himself into thinking that he will solve a vibration problem, which is caused by some inherent design deficiency in the rotor or drive train system.
    • A wide spread (over 7 - 10%) between normal cruise and flat out maximum level flight should raise eyebrows. Some manufacturers quote a VNE speed, which is a maximum dive speed. It will be necessary to be very specific here to get the correct answer.

Group IV Questions:

    1. All kits are not equal. You must ask specific questions to find out just what it is you will be doing to complete a kit. Do you need to do any welding, machining, hand forming or moldless composite work? Will you be doing enough fabrication work to qualify you to receive an airworthiness certificate?
    2. To judge quality you will need to talk to a customer, be knowledgeable enough to quiz the designer or salesman or make a trip to the factory.
    3. How are the kit components packaged?
    4. Kit instructions are given in two formats. Picture and caption with some drawing & prints or a video presentation. Manufacturers commonly start out with paper instructions and then later include video. The best method is a combination of the two, however the level of detail in either method is what is important. Ask to see some portion of the instruction package, so you can determine whether it meets your expectations.


    • To be legal to fly, an amateur built aircraft must be issued an airworthiness certificate. FAA advisory circular 20-27D covers this in detail with straightforward step by step instructions. The key to receiving a certificate lies in compliance with the rules. Individuals who believe they will purchase a kit and get someone else to completely build it for them will probably not be successful in obtaining an airworthiness certificate. Beware of 50-100 hour construction times published by any kit builder. The phrase "Fast Build Kit" is now common, however this is primarily a marketing technique. A kit that does not comply with the FAA Amateur Built 51% rule will not be licensable.
    • It's hard to see inside somebody's main transmission to find out about the quality of the gears and bearings. Ask if any technical video's are available which would help to enlighten you. Look at the fit and finish of the assemblies supplied in the kit. If you have an engineering background, ask questions about the materials used in construction.
    • A manufacturers part numbering system is a great indicator of his ability to produce quality. Ask for a copy of this system and see how organized it looks. All kit components or assemblies should come with part numbers denoted. Parts may be shrink wrapped or packaged in a separate plastic bag with a label. Whichever way it's done, the last thing you want to receive is a box full of unlabeled bits and pieces.

Group V Questions:

    1. Price cannot be judged until the quality level is known. That's the whole purpose of this article. Good marks are given for high quality and reasonable prices. High marks are given for high quality and low prices.
    2. Beware of anyone who requests full payment up front for a new design.
    3. Ask about the business history of the designer, manager or C.E.O. of the company. A bonifide operation will be happy to provide this information.


      This group of questions is self-explanatory.

Group VI Questions:

    1. Is the machining done in-house?
    2. If machining is done outside, ask to see a copy of the first 3 or 4 pages of the quality control manual. (This is the manual used by the kit company to check out parts made outside.)
    3. Are company assembly manuals written for use in assembling the main and tail rotor gear boxes and the rotor hub and blades. Are sign-offs required during the assembly process?
    4. If metal blades are supplied are blade bonding coupons catalogued on each production group? If composite blades are supplied what type of permanent records are kept.
    5. What parts are serialized and traced? How is the parts tracibility system set up?
    6. What is the company policy in regard to a part that wears out or fails prematurely, even if no formal warranty is offered?


    • If machining is done in-house, you can be pretty confident that machining tolerances are being held to specifications. The most probable reason for machining being done outside is that management is just not too familiar with the machinist trade. It is vital to have a world class quality control system set up in-house to check the tolerances on parts made outside. A co-ordinate measuring machine is a vital piece of quality control equipment in this case. These machines cost five figures, so if the shop has one, you can be pretty sure they know what they're doing. To find out, you must of course ask. If they don't have this piece of equipment and parts are made outside, beware.
    • If the company doesn't use in-house produced assembly manuals, with the need for quality control sign offs at critical assembly points, you need to look for a different kit supplier. Assembling a main transmission for an R-22 or an Apache or a HELICYCLEŠ is at least a 100-step process. Once this process is worked out, it is impossible to remember each detail from memory. You must have a manual to refer to.
    • Some permanent record must be kept in regard to rotor blade bonding procedures on each batch of blades that is constructed. This goes for metal or composite blades. Ask what method the kit company utilizes.
    • Serialization of critical parts is more important to the company than it is to the customer. How can the company possibly stay in business if they find out a part has failed in the field and they have no record of what production batch it was in. They simply can't afford to ground every ship and replace every part! Be aware that in the amateur built category there is no requirement for the company to keep these kinds of records. If the kit manufacturer you're looking at doesn't keep these records, you need to find someone who does.
    • Most amateur built kits don't have a warranty, but a quality company will make every effort to solve field problems in the most equitable manner. See what kind of an answer is given to the warranty question.

Group VII Questions:

    1. Is a final construction checklist supplied?
    2. Is the customer (even if they are helicopter rated) going to be the first person to fly this machine?
    3. What type of checks and balances are in place to insure the customers safety and success as he begins to operate his newly finished machine?


    • A final construction checklist for double checking the adjustment of each system or component is a vital must for any helicopter. You can't afford to miss one item. You would want to comply with this checklist for two reasons. First, you wouldn't be ready to have your ship inspected for airworthiness without it and second, when the factory test pilot comes to fly it, if it's not ready, you'd be running up a higher bill than necessary.
    • Every commercial helicopter, when it comes off the production line, is handed off to two people. A production test pilot and a flight-test engineer. These folks test fly the helicopter side by side for many hours in order to check out and adjust all the systems and calibrate them to meet the operational type specifications. This is a critical task, performed by specially trained, very experienced personnel. If the kit manufacturing company does not provide this kind of personal check out service either at your place or at the factory, beware. Be sure to ask this critical question.
    • It comes down to this. It takes years of experience before a kit helicopter manufacturer gets his arms around the whole banana. Learning the kind of mistakes kit builders make, and designing a construction and flight program which will keep the customer out of trouble, is no small task. It requires lots & lots of experience. Go with the company or the designer who has paid their dues & been through the fire.


We have provided a list of 33 questions. Pick out 15 or so of those you feel most appropriate. You may wish to add a couple more of your own. Use this exact list to evaluate each prospective design in order to achieve apples to apples comparison.

Answers are to be weighted according to the following scale:



Now it's time to use the "Compound Equation" to achieve a bottom line number for each design.

I cannot take credit for this elegantly simple, foolproof method of assessing relative quality. The "Compound Equation" was promulgated by my friend Tom Stuelpnagel, who was for many years the C.E.O. of Hughes Helicopters, Summa Corporation.

This formula was used to provide a comparison of value for their equipment. It helped confirm the value of the Apache during the period of time when Mr. Stuelpnagel was selling this major helicopter program to the U.S. Army.

Here's how it works, and its sooo simple. Multiply the rating weight number of each question together to calculate the total value of each design.

A design, which answers .9 to each of 10 questions for example, has a final rating of .348. a design, which answers 1.1 to each of 10 questions, has a final rating of 2.59. This is a 7.4 times improvement! Of course, every design has its strengths and weaknesses so the spread will be much closer than 7 to 1.


Utilizing this simple rating system in conjunction with the compound equation not only is an eye opener; it's a qualitative method of determining what designs it would be prudent to avoid.

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