6/29/15 Appendix 3 APPENDIX 3. LIGHT CONTROL FORCES AND/OR RAPID AIRPLANE RESPONSE
1. DEFINITION. Light control forces coupled with strong control authority for rapid maneuvering about one or more axis. This section includes airplanes that have substantial disharmony between two or more axes.
2. DISCUSSION.
a. Example Accident from the National Transportation Safety Board (NTSB) Records.
(1) Accident. The pilot had constructed the homebuilt aircraft, and had flown it twice before, totaling 1.2 hours. After rotation and liftoff on his third flight, the aircraft pitched up and down several cycles then settled down. The airplane climbed slowly, and at 200 feet altitude, the pitch oscillation began again. The aircraft climbed another 50 feet, then rolled to the left and impacted the ground.
(2) Probable Cause. The pilot not maintaining aircraft control during the initial climb after takeoff and the inadvertent stall/spin. A factor to the accident was the pilot’s total lack of experience in the accident airplane.
b. Analysis and Avoidance.
(1) Unfortunately, it is impossible to understand the exact cause of this accident. One possibility is the pilot’s lack of experience with the accident airplane, as stated by the NTSB.
Airplanes like the Extra 300 and Pitts are safe airplanes, with some versions holding FAA type certification. However, most pilots would not be safe flying these airplanes without training because they maneuver quickly with low control forces. Of course, most pilots can look at these airplanes and understand that they will probably want additional training in them before trying to fly them solo.
(2) There are many more experimental airplanes that may look more like type-certificated (TC) airplanes, but they actually have light control forces and/or very quick maneuvering response. Lightweight and lightly wing-loaded airplanes can also have the same quick, light response as many aerobatic airplanes. The hazard of light forces and rapid response is that without some level of training, the pilot may over-control the airplane. This can manifest itself during any phase of flight. The risks can vary from frustration to damage during takeoff and landing, to loss of control up to and including overstressing the airframe and structural failure.
(3) Unfortunately, there are control characteristics like these frequently on airplanes with poor stall handling characteristics. This is a deadly combination when aggressively maneuvering close to the ground. Too large a percentage of fatal experimental accidents fit in this category.
Pilots considering purchasing an experimental airplane need to appreciate how much effort TC’d airplane manufacturers expend to ensure good handling characteristics. It may take weeks of trial and error flight testing to get an airplane to handle the way the manufacturer desires. This effort may include redesigning parts of the wings and tails, and their control surfaces. The General Aviation (GA) pilot community is very familiar with the handling characteristics of TC’d airplanes that have been around for decades, like the Cessna C-172 and the Piper PA-28. That
6/29/15 Appendix 3 same level of widespread familiarity does not exist with the small number of experimental airplanes. Transferring conventional GA handling techniques to aircraft with light control forces and/or rapid maneuver response can result in inadvertent stalls, loss of control, or structural failure.
3. RECOMMENDED FLIGHT TRAINING. Pilots transitioning from any one of the majority of TC’d airplanes may tend to over control an experimental airplane with light controls and quick responses. Design the pilot training needed for an airplane with light control forces and/or rapid maneuvering capability, to tailor control inputs appropriately. This cannot be simulated in an airplane that does not have similar characteristics. There are several avenues that would help to prepare you for your experimental airplane.
a. Best Training. The best training is accomplished in the specific airplane the pilot intends to fly with a well-qualified instructor who has recent experience in the specific make and model.
b. Second Best Training. The second best choice would be in the same model as the one the pilot is planning to fly.
c. Third Best Training. The third best choice is to fly an airplane with similar characteristics.
6/29/15 Appendix 4 APPENDIX 4. LOW-INERTIA AND/OR HIGH-DRAG
1. DEFINITION. Airplanes which rapidly lose energy (airspeed and/or altitude) when there is a loss or reduction of power.
2. DISCUSSION.
a. Example Accident from the National Transportation Safety Board (NTSB) Records.
(1) Accident. It was the first flight of a newly completed homebuilt airplane. The 600-hour private pilot had no previous time-in-type. On his first landing, he misjudged the amount of power required during the landing flare and the airplane struck the runway nose-first.
The nose gear collapsed.
(2) Probable Cause. The pilot misjudged the power required during the landing flare, which resulted in a hard landing on the nose wheel. A factor associated with the accident was the pilot’s lack of experience in the airplane.
b. Reduction of Drag.
(1) One major theme throughout aircraft development over the past 100 years of aviation is the reduction of drag. Airplanes with less drag require less thrust for the same performance, requiring less fuel and thus increasing efficiency and utility. High-drag airplanes have all but disappeared in the production-airplane world. However, they still exist in surprising numbers in the experimental airplanes ranks.
(a) First, some pilots do not want to be in an enclosed fuselage; they want the wide-open freedom of an open-structure airplane like a Breezy or a Quicksilver MXL.
(b) Second, many pilots want to build a good-quality airplane in the least amount of construction time and at the lowest cost. For example, consider a high-drag round aluminum tube that would be exposed to the airstream when the aircraft is in flight. A builder could spend tens of hours sculpting a low-drag fiberglass fairing to cover the tubing, or elect just cover the tubing with fabric and move on to the next part of the project. While the streamlined fairing adds time and money to the construction, it would result in an aircraft with less overall drag. A builder should consider a structure’s effect on drag when designing and building the aircraft.
(c) Third, some pilots want to get off the beaten path in Short Takeoff and Landing (STOL) airplanes like the Zenith CH-701 or the Highlander. The highly cambered airfoils used by these airplanes produce a lot of lift, allowing the airplane to safely fly slowly, but with a high-drag penalty.
(d) Finally, there are people who prefer the look of airplanes designed before drag reduction became popular. There is something special about flying open cockpit biplanes like the Hatz or Baby Great Lakes, or classic monoplanes like the Pietenpol or Fly Baby. These airplanes are often light in weight. When combined with high-drag, this means the airplanes slow quickly when reducing power or when the G Load rises.
6/29/15 Appendix 4
(2) Most pilots don’t take their initial training in these types of airplanes. They become accustomed to the drag characteristics of the type-certificated (TC) airplanes in which they learned to fly. Many “low and slow” experimental airplanes glide at a much steeper angle than these pilots are accustomed to, and this can cause problems.
(3) In the accident described in the beginning of this appendix, the pilot was flying a popular, low-cost STOL airplane with a fat, high-lift airfoil. He reduced the power for landing, and probably expected a glide path like the TC’d airplane he had learned to fly in. Instead, he got a much steeper approach than he expected, and found himself nearing the ground at a high rate of descent. He undoubtedly attempted to flare to flatten the approach, and probably tried to add some power. But the lightweight airplane quickly decelerated and kept descending at an excessive rate.
(4) Since power is often the method of compensation for the effects of low-inertia and high-drag airplanes, engine reliability can be critical. Light, low-cost homebuilt airplanes often use non-TC’d engines. These can provide more power in a smaller, lighter package, but reliability may suffer. The consequences of an engine failure in this family airplane may be significant.
(5) These characteristics affect a surprising number of pilots. Half the accidents involving one popular low-inertia/high-drag airplane occur during landing, versus about 30 percent of homebuilt accidents overall. Half the pilots involved had less than 12 hours in type versus 60 hours for the overall homebuilt fleet.
3. RECOMMENDED GROUND TRAINING. Pilots operating low-inertia/high-drag airplanes with experimental engines should avail themselves of any available training on operating their engine. For example, to minimize the chances of power interruption, operators of two-stroke engines should receive training on how to avoid cold seizures and how to properly manage the engine to maximize reliability. Another example is that pilots operating airplanes using propeller speed reduction units should understand the power modes and revolutions per minute (rpm) ranges to avoid.
4. RECOMMENDED FLIGHT TRAINING.
a. Choice of Aircraft. The following lists methods of flight training, in preferred order, when seeking to transition to an experimental and/or unfamiliar airplane:
(1) Best Training. The best training is accomplished in the specific airplane the pilot intends to fly with a well-qualified instructor who has recent experience in the specific make and model.
(2) Second Best Training. The second best choice would be in the same model as the one the pilot is planning to fly.
(3) Third Best Training. The third best choice is to fly an airplane with similar characteristics (which may include a TC’d airplane).
6/29/15 Appendix 4 Page 3 (and 4)
b. Simulating. In some cases, simulating the drag characteristics of these airplanes using a TC’d training airplane, such as a Cessna C-150 maneuvering with 40 degrees of flaps (in accordance with the airplane limitations), is possible. The deceleration upon power loss can be similar, and the steeper descent rates can help prepare them for operation of their own airplanes.
This is especially important for simulated forced landings after engine failures. By flying the conventional airplanes in a high-drag configuration, pilots can experience how fast the speed decays and how lowering the nose further achieves a normal approach speed.
c. Power Landing. Pilots should also consider using power-on, controlled approaches with power maintained throughout the transition to touchdown. Use of power during landings can approximate the glide angle that the pilot is used to flying. Delay experimentation with throttle-closed approaches and landings until the pilot has sufficient experience with the airplane.
d. Other Hazards. Hazards of low-inertia/high-drag airplanes are not limited to power management issues. While all airplanes experience an increase in stall speed with an increase in load factor, such as during turns, these airplanes may also experience significant airspeed decay with increased load factor. This, coupled with low cruise speed to stall speed margin, make these airplanes particularly susceptible to unintentional stalls.
6/29/15 Appendix 5 APPENDIX 5. HIGH-INERTIA AND/OR LOW-DRAG
1. DEFINITION. Airplanes that slowly decelerate when power is removed.
2. DISCUSSION.
a. Example Accident from the National Transportation Safety Board (NTSB) Records.
(1) Accident. The homebuilt airplane landed long and could not make a complete stop on the available runway; the airplane bounced three times. On the third bounce, the pilot lowered the tail wheel; the main landing gear came off the ground, indicating too much airspeed. He applied power to go around with 300 feet of runway remaining. To avoid trees, he pulled up abruptly, then pushed over again. The engine quit momentarily during the pushover (likely due to negative G Load), and the airplane crashed on a nearby golf course.
(2) Probable Cause. The pilot’s failure to maintain airspeed and his failure to perform a go-around. The pilot’s misjudgment of speed and distance during the landing is a contributing factor.
b. Inherent Risks/Hazards.
(1) As stated in Appendix 4, drag reduction was and still is a major objective in airplane design. These airplanes are on the leading edge of this design trait. They are beautiful, sleek, and even sitting on the ground just look fast. Airplanes in this family are generally fast, efficient, and may have significant range; however, the hazard is that unless managed, these airplanes can build excessive speed during critical flight phases such as approach and landing. The risks of unmanaged speed include overshooting final approach, inadvertent stalls, loss of control, wheel barrowing, and runway excursions.
(2) These risks are not inherent to only high-performance airplanes. For example, airplanes resembling motor gliders may experience substantial float and overshoot a substantial amount of runway with only a few knots of extra speed on landing. This family also includes airplanes designed for high-speed cruise. In some cases these airplanes have relatively high stall speed and, consequently, high approach and landing speeds. Airplanes with high landing speeds can be a challenge for pilots experienced only in type-certificated (TC) airplanes. High landing speed can easily translate to long touchdowns, runway overruns, and late go-around decisions.
Also challenging for pilots of these airplanes is following a slower airplane into the traffic pattern or a fly-in event such as AirVenture.
3. RECOMMENDED GROUND TRAINING. Pilots transitioning to this family of airplanes should spend some time reviewing the proper power, airspeed operating limits, altitude, and configuration for their specific airplane’s approach and landing. Discussion should include configuration and speed control for a stabilized descent and approach. Performance calculations for landing distance and safe margins for runway length should be done so pilots are aware of the runway lengths needed for safe operations. Decisionmaking on when to reject landings and go around should be made before flying.
6/29/15 Appendix 5
4. RECOMMENDED FLIGHT TRAINING. A thorough airplane check-out by a qualified instructor, preferably with recent experience in your airplane make and model, is always a good idea. Flight training should include descents from altitude, pattern work, and landing distance awareness. Practice descents to determine distance versus altitude to begin a proper descent profile. A properly planned descent should permit the aircraft to descend without large reductions in power and to avoid over-speeding the aircraft. If the airplane is equipped with speed brakes, incorporate them into the training. Pattern practice should emphasize proper power, altitude, and configuration for the approach and landing phase of flight. Demonstrate the landing distance required under various aircraft configurations and then practice for repeatability.
There needs to be an emphasis on control and understanding your airplane’s stopping distance.
6/29/15 Appendix 6 APPENDIX 6. NONTRADITIONAL CONFIGURATION AND/OR CONTROLS
1. DEFINITION. An airplane whose external configuration is sufficiently different from traditional type-certificated (TC) single-wing, empennage-mounted tail designs so that it displays nontraditional handling qualities. Flight control surfaces different from typical elevator-aileronrudder-engine/prop arrangements and/or flight control systems are different from typical stick/yoke-pedals implementations.
2. DISCUSSION.
a. External Configuration. TC’d airplanes follow a fairly standard external configuration.
There is usually one main wing, each with one aileron and possibly a flap, and a tail consisting of a vertical and horizontal stabilizer with trailing edge rudder and elevator. There can be slight variations such as a stabilator instead of a stabilizer and elevator, or a V-tail design that uses ruddervators to perform both yaw and pitch functions. Compliance with regulations ensures that regardless of the configuration, all TC’d airplanes behave in expected, intuitive, and acceptable ways.
b. Innovations. The experimental aircraft community has a long history of innovation, including nontraditional configuration and controls. Traditional wing/tail combinations are common, but so are canards and wing-mounted pushers. There might be flaperons performing double duty as roll controllers and high-lift devices leading edge slats, multiple lifting wings, differential spoilers, all-moving vertical tails, etc. In the cockpit, an experimental airplane might have a yoke or a stick, and that stick could be an outboard side-stick or one between two seats. It might pivot traditionally or translate/slide for pitch control while pivoting for roll control. Some experimental airplanes have the throttle on the pilot’s left, some on the right, and some have both, leaving the option of which hand to use to the pilot. There are even some with the throttle on the floor between the pilot’s legs. The hazard is that such variety of cockpit control locations and operation can lead to potential misuse of the controls due to the unfamiliar human-machine interface.
c. Canards.
(1) Canards are very popular in the experimental airplane world. While they offer several aerodynamic advantages, they also carry unique risks. Since both the canard and wing lift upward, this is a more aerodynamically efficient design than a traditional wing/tail airplane.
Designed properly, the canard should always stall before the main wing, thereby generating a recovering nose-down pitch. Unlike traditional wing/tail airplanes, however, there may not be noticeable buffet prior to the stall. A canard that stalls during the landing flare will likely result in airplane damage or worse.
(2) Canard designs typically have a rudder on each swept wing tip with each rudder only deflecting outward. This can feel natural to the pilot and actually helps minimize adverse yaw.
Unlike traditional airplanes, both rudders can be deflected simultaneously. While this can be a useful speed brake, it can also produce an unexpected pitching moment, due to the fact that the deflected rudder changes the air flow over the outboard wing section, which is aft of the
6/29/15 Appendix 6 airplane’s center of gravity (CG). Likewise, aileron effectiveness could be affected if it is within the influenced air flow.
(3) The dramatic wing sweep of canard design exists to locate the rudders far enough aft to be effective. An inevitable consequence of the sweep is a strong rolling tendency during uncoordinated flight. A sideslip can be generated by rudder deflection or a wind gust. In both cases, the airplane will likely weathervane back into the relative wind, but it will also roll away from the sideslip. In some canard designs, particularly during slow flight, this rolling tendency can be more powerful than can be countered with the ailerons.
(4) These designs often incorporate wheel brakes operated by applying force to the rudder pedal after fully deflecting the rudder. This design saves weight and space that normally accompanies a traditional toe brake system, but it means there is no braking without full rudder.
The system usually works well for taxi steering, but it warrants consideration and familiarity for crosswind takeoffs and landings.
d. Configurations. Other risks exist in the variety of control configurations.
(1) Some airplanes employ hand levers to operate the wheel brakes. Properly designed, these systems can perform adequately, although arm strength can become a factor in braking effectiveness. Unlike traditional foot-operated brakes, using hand brakes requires the pilot to release either the stick or the throttle (unless the lever is mounted on the stick). Applying differential braking with one hand operating two levers can be challenging. A setup where a single lever operates both wheel brakes works well only if it is perfectly rigged. Cable stretch, uneven brake wear, or uneven linkage wear can cause the application of more braking to one wheel without any way for the pilot to deal with it besides rerigging.
(2) Thrust lines vary among experimental airplanes. High-wing-mounted pusher configurations are common. Unlike traditional airplanes where increasing power usually causes a nose-up pitch, some of these designs produce the opposite airplane response. Although pilots can get used to applying an opposite direction stick displacement with every throttle change, it complicates maneuvers such as an aborted landing go-around. Thorough familiarity with your airplane’s power-pitch characteristics is essential for safe flight.
(3) How the pilot interfaces with the control surfaces has a large influence on workload, handling qualities, and overall satisfaction with the airplane. A short side-stick that requires a lot of effort to move limits maneuverability and will likely be worse at faster speeds. Finding the centered or neutral stick position as a primary step in an out-of-control situation can be very difficult with a side-stick. There’s no flying with your knees while you fold a chart or copy a clearance with a side-stick.
(4) Some pilots enjoy a tactile reference for their stick arm, usually by resting a forearm on their thigh. Side-stick designs without an arm rest deprive the pilot of this reference, which can make fine adjustments difficult and generate unwanted control inputs in turbulence. There are side-stick applications that have the stick between side-by-side seats. Poor design implementations can limit roll control due to interference with either occupant’s leg or hip.
6/29/15 Appendix 6 Page 3 (and 4)
3. RECOMMENDED GROUND TRAINING. Pilots should become thoroughly familiar with the location and force, displacement and operative sense requirements of their cockpit controls.
Practice blindfold cockpit exercises and simulated emergency procedures on the ground. Know your airplane’s systems, limits and recommended procedures before you begin flying. Consult the designer/kit vendor for advice. Discuss your situation with type club members and owner/builders of your airplane model. Internet forums and chat rooms may provide valuable information, but remember that the participants may or may not have the technical expertise you seek, and their airplanes may not exhibit identical handling qualities to your airplane.
4. RECOMMENDED FLIGHT TRAINING. A thorough airplane check-out by a qualified instructor preferably with recent experience in your airplane model is always a good idea. If you built the airplane yourself, consider obtaining this training from the kit vendor, preferably in your airplane, but the company demonstrator may provide sufficiently similar characteristics. If you purchased your airplane from a previous owner, learn all you can from him or her. Your training should emphasize the unique aerodynamic behavior of your airplane’s nontraditional configuration and any pilot compensation required to safely fly your airplane. If your airplane’s cockpit controls are different from what you are accustomed to, become familiar with the advantages and disadvantages of the design and explore your airplane’s handling qualities under safe, supervised conditions.