59 SECTION 3. NAVIGATION, FUEL CONSUMPTION, AND NIGHT FLYING ‘‘That’s one small step for man, one giant leap for mankind.’’ Neil Armstrong
1. OBJECTIVES. To ensure all the small but important aspects of flight have been tested and found reliable.
a. The Magnetic Compass. The magnetic compass should have been checked for accuracy prior to the first flight. However, the addition and removal of equipment, changing of wire bundle routing, and other airframe modifications may have affected the accuracy of the instrument. The following recommendations are offered:
(1) The magnetic compass can be checked for accuracy by using a compass rose located on an airport, or using a hand held ‘‘master compass.’’ The master compass is a reverse reading compass with a gun-sight mounted on the top of it. With the aircraft facing north and the pilot running the engine at 1,000 rpm, a second individual standing 30 feet away facing due south ‘‘shoots,’’ or aligns, the master compass with the aircraft’s centerline. Using hand signals, the pilot aligns the aircraft with the master compass. The pilot then runs the aircraft engine up to approximately 1,700 rpm to duplicate the aircraft’s magnetic field and reads the compass.
NOTE: Conventional gear aircraft builders will have to position the magnetic compass in a straight and level position for this test.
Raise the tail or mount the compass level with the horizon.
(2) If the aircraft compass is not in alignment with the master compass (start at north), correct the error by adjusting the north/south brass adjustment screw with a non-metallic screwdriver (can be made out of stainless steel welding rod, brass stock, or plastic) until the compass reads correctly. Go to the reciprocal heading (south) and remove half the error. On the east/west headings, use the other brass adjustment screw to make the corrections using the same procedures that was used to correct the north/ south errors.
(3) Check again for errors at each cardinal heading. Record the last readings and prepare a compass correction card. The maximum deviation (positive or negative) is 10 degrees on any one heading.
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(4) If the compass cannot be adjusted to meet this requirement, install another one. If the new compass is not available, try a different location in the cockpit, away from all ferrous metals and electrical bundles.
NOTE: A common error that affects the compass’s accuracy is the mounting of magnetic compass on/in the instrument panel with steel machine screws and nuts rather than brass.
(5) If the aircraft has an electrical system it is recommended that two complete compass checks be made, one with all electrical accessories on (e.g., radios/nav lights), and one with all electrical accessories off. If the deviation in level flight is more than 10 degrees on any heading with the accessories on, make up a separate compass correction card that shows the magnetic heading with the equipment on.
(6) Record the findings in the aircraft’s flight manual and create a compass correction card, mounting it near the magnetic compass in the cockpit. Make two cards; one with radios on and one with radios and non essential electrical accessories off.
b. Very High Frequency (VHF) Omni-directional Radio Range (VOR) Check. The best guide to check the accuracy of the VOR on board equipment is the VOR Receiver Check found in the Airman’s Information Manual (AIM), available from the Superintendent of Documents. The following is an abbreviated summary of the VOR procedure in the AIM.
(1) For a ground test of the VOR, a VOR Test Facility (VOT) must be used. To use the VOT service, tune in the VOT frequency on the VOR receiver. It is normally 108 Mhz. With the Course Deviation Indicator (CDI) centered, the omni-bearing selector should read 0 degrees with the to/from indicator showing ‘‘from,’’ or the omni-bearing selector should read 180 degrees with the to/from indicator showing ‘‘to.’’ The maximum bearing error should never be more than four degrees.
NOTE: The VOT facilities closest to the flight test location can be found in the Airport/Facility Directory. It is available by subscription from NOAA Distribution Branch N/CG33, National Ocean Service, Riverdale, MD 20737, or contact the nearest FAA FSS.
(2) For the airborne test, select a prominent ground point along the selected radial, preferably more than 20 miles from the VOR. Maneuver the aircraft directly over the point at a reasonably low altitude.
(i) Note the VOR bearing indicated by the receiver when over the ground point. The maximum permissible variation between the published radial and the indicated bearing is six degrees.
(ii) If the aircraft has dual VOR’s, the maximum permissible variation between the two receivers is 4 degrees.
c. Fuel Consumption: a good indication of how much the engine is working for each rpm produced. For a new or recently overhauled engine, the fuel consumption should improve each flight hour until the engine finishes its ‘‘break in’’ period, i.e., after approximately 100 hours of operation.
(1) To determine the aircraft fuel consumption, lay out a race track course with 8 to 10 mile legs. If the aircraft has one fuel tank or cannot switch tanks, do the following: Determine the approximate fuel burn to reach 1,000, 3,000, 5,000, 7,000, and 9,000 feet of altitude. With full tanks, climb to 3,000 feet and run the race track course for half an hour at 55 percent power.
(2) Land and measure the fuel used by dipping the tanks with a calibrated fuel stick, or by adding measured amounts of fuel to the tank until the tank is full. Subtract the approximate fuel burn to altitude, and multiply the remainder by two to get the fuel burn per hour.
(3) The tests are much easier and the results more accurate if the aircraft has two independent fuel tanks. Take-off on one tank and switch to the opposite tank at the test altitude. At the completion of the test, switch back to the first tank; land and measure the amount of fuel added in both tanks and multiply the quantity by two to get the amount of fuel used per hour.
(4) Run the same test at 65 percent and 75 percent power at the same altitude, using the same procedures. Move up to the next altitude and run the same tests.
d. Night Operations: should be conducted in accordance with the aircraft’s FAA Operating Limitations and limited to normal climbs and descents (e.g., 500 feet per minute), pitch angles of less than 5 degrees, straight and level flight, and coordinated turns of no more than 20 degrees of bank angle.
(1) The main concern for night testing should be the availability of a horizonal reference
(e.g., bright moon or artificial horizon).
(2) Prior to every night flight, ensure a reliable flashlight with fresh batteries and a set of FLIGHT TEST PLAN procedures are on board.
Some night testing requirements should have already been determined on the ground. For example:
(i) The electrical load review of all the lights, pumps, instrumentation, and avionics did not exceed 80 percent of the aircraft’s charging system capacity.
(ii) The cockpit instrumentation lighting is adequate and was tested for reliability of operation during daytime flights.
(iii) The pilot has at least 1⁄2 hour of night time taxiing the aircraft. This practice is needed to familiarize the pilot with a different operating environment. Do not exceed engine operating temperatures during taxiing.
(iv) The position and brightness of instrument panel lights, anti-collision strobe lights, and rotating beacons will not adversely affect the pilot’s night vision.
(3) A suggested night flight test plan is a series of takeoffs and landings and traffic pattern entries and exits. The tests should begin while there is still enough light to read a newspaper and transition to true night flying. The actual night flight will consist of an evaluation of the effectiveness of the taxi/landing light system, during taxi, take-off, and landing. The pilot should note any glare on the windshield or light flicker on the instrument panel.
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63 CHAPTER 7. THOUGHTS ON TESTING CANARD TYPE AMATEUR-
BUILT AIRCRAFT ‘‘FLY.’’ Jonathan Livingston Seagull SECTION 1. CANARDS
1. OBJECTIVE. To discuss canard flight characteristics.
a. Canard configured aircraft generally fall into 2 categories: the LongEze design (pusher prop, tandem seats) and the Quickie (Q2) design (tractor prop, side by side seats). Canard configured aircraft do not ‘‘stall’’ in the conventional sense. All successful ‘‘loaded canard’’ designs have the angle of incidence (AOI) of the canard set higher than the main (rear) wing.
b. As the airplane’s angle of attack (AOA) increases, the canard should stall first, lowering the AOA of the main (rear) wing. Since the rear wing doesn’t stall, a characteristic ‘‘buck’’ or ‘‘nod’’ takes place. Full aft stick results in the canard alternately stalling and flying while the rear wing never reaches it’s critical AOA and continues to fly. This self-limiting stall characteristic makes a properly designed and built canard aircraft un-spinable. It should be noted, however, that the accident rate for canard designs are approximately the same as conventional designed amateur-built aircraft because of the following:
(1) During take-off, the transition from ground roll to flight can be a more critical procedure in some canards as compared to more conventional designs.
(2) Some canards with combinations of CG and pitch control sensitivity will be more likely to over rotate at lift-off.
(3) Some canards have less visible airframe structure in front of the pilot and in his peripheral vision. Others have more than enough. These differences in design can produce a different reference frame for pilots with many hours of conventional aircraft time and may cause initial errors in pitch attitude, such as the nose too high on takeoff and landings.
(4) In addition, canard aircraft by design have very different take-off characteristics than conventional configured aircraft. Canard aircraft with pusher propellers need a substantially higher rotation speed on take-off.
(5) To rotate a conventional design aircraft, all that is required is enough airspeed to provide sufficient control to attain a positive angle of attack due to the long moment arm from the main gear (the axis of rotation) to the tail, a relatively small amount of lift is required. This lift, generated at a relatively low airspeed, makes it possible to rotate the aircraft into the take-off position slightly below flying speed. Allow the aircraft to accelerate to flying speed and lift off.
(6) In contrast, the canard nose wheel will stay firmly on the ground until an airspeed is reached at which the canard, with full up elevator, can generate enough lift to equal the following:
(i) the load carried by the nose wheel, plus
(ii) the nose down moment caused by the friction of the nose and main gear tires with the surface, and the down-thrust vector provided by the propeller during the take-off roll.
(7) Since the main wing may reach flying speed before the canard, the nose wheel will stay firmly on the runway until take-off speed is reached.
Rotation will then occur, and the aircraft will literally jump off the ground.
(8) Canards with a thrust line above the CG will have appreciable pitch trim change with power. Forward stick motion is required when power is reduced. While this may not be of any consequence to an experienced pilot, it can be a serious surprise to an unwary and inexperienced pilot. This unfamiliar flight characteristic might cause pilot-induced pitch oscillations with disturbing consequences under some conditions (e.g., an aborted take-off).
(9) Due to its unique design, the canard aircraft needs a higher nose up attitude when landing compared to conventional configured aircraft. Many canard pilots are reluctant to raise the nose high on
64 5/24/95AC 90-89A landing due to the limited forward visibility while the nose is up. Consequently, many canard pilots tend to make their approach angle shallow. This shallow angle results in approach speeds quite a few knots faster than what is necessary. For pilots who prefer visibility to shorter runways, it is recommended that canard designed aircraft be tested on runways a minimum of 1,000 feet longer than what would be used for a conventional aircraft of the same horsepower and performance capability.
Longer runways should be used until the pilot becomes more experienced with the landing characteristics of the aircraft.
(10) If the nose is held at a too high an angle on landing, the canard will stall while the main wing is still generating lift. The stalled canard will drop the nose rapidly onto the runway with enough force to damage the nose gear.
(11) Quickie (tractor engine designs) configured canard designs have a limited ability to rotate nose up while on the ground. This tends to increase takeoff speeds because the canard and the main wing angle of attack are limited while the aircraft is on the ground. That is why this design appears to ‘‘levitate’’ off the ground without much apparent pitch change.
(12) Some canard designs are very sensitive to rain or other types of contamination on the leading edge and/or top of the airfoil. Contamination in the form of water droplets, frost, crushed insects, or even poorly applied paint will disturb the laminar flow over the canard and lift is lost. When decreasing lift over drag (L/D) performance, the chances for an accident increase.
2. FLIGHT TEST CONSIDERATIONS.
Technically, a canard type aircraft cannot stall, or at least it will not stall in the normal fashion. A pilot testing the aircraft for stability characteristics should approach such testing with caution in mind.
a. Under certain conditions, usually consisting of aft c.g. problems, the main wing may stall before the canard surface. In this case, extreme pitchup can occur until the canard surface or strakes stall.
The aircraft would then pitch down to a near-level attitude, however the airspeed would be approaching zero and the angle of attack could approach or exceed 45 degrees. This condition (high-alpha), could be so stabilized, with the aircraft in a deep stall, that recovery might not be possible.
b. Testing for pitch stability in a new design or a just-completed aircraft built from a kit or from plans is a requirement the pilot needs to consider prior to carrying passengers. Pitch stability tests are conducted to ensure that the aircraft does not exhibit any dangerous flight characteristics but must be approached and conducted in a logical and sensible manner.
(i) Positive pitch stability is exhibited when the aircraft trimmed for hands off level flight, returns to that state when a control force is applied and released.
(ii) Neutral pitch stability is achieved when the aircraft remains in the pitch attitude attained when a control force is applied.
(iii) Negative pitch stability is demonstrated when the aircraft departs from the pitch attitude attained when a control force is applied and continues to increase in amplitude.
c. The aircraft should be weighed and the c.g.
carefully calculated. At the same time, determine the weight needed and the moment calculated to load the aircraft at the most forward and aft c.g. limits recommended by the designer. Beginning at the most forward c.g., trim the aircraft to a hands off condition and slowly reduce the power, maintaining altitude by increasing pitch attitude. When the stick reaches the full aft position, momentarily release the back pressure followed by full aft stick. The aircraft, in demonstrating positive stability, should return to its original pitch attitude and remain there. The aircraft should display positive stability characteristics.
d. Other tests may be conducted by adjusting the c.g. further aft and observing the tendency of the aircraft. At some point near the aft c.g. limit, you may experience neutral stability, or the point where the aircraft no longer recovers by itself from the upset. Moving further aft in the c.g. range from this point will cause the aircraft to diverge from the trim path in the direction of the upset (neutral stability).
e. Some designers and builders have installed adjustable, moveable ballast containers in the aircraft to allow the c.g. to be adjusted forward or aft during flight. If testing is to be accomplished outside the
65 recommended range, it is advisable to consider the installation of a ballistic recovery system or spin chute system. In addition, the pilot should make a decision about leaving the aircraft if the test becomes untenable.
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67 CHAPTER 8. ULTRALIGHT AIRFRAME INSPECTION ‘‘You can learn 10 things by learning one.’’ Japanese proverb SECTION 1. DIFFERENCES
1. OBJECTIVES. To serve as additional resource for ultralight test pilots and to help the new owner develop a flight test plan for the ultralight.
2. DEFINITION. The term ‘‘Ultralight’’ means a fixed wing vehicle that is powered by a conventional 2 or 4 cycle, gasoline powered engine and is operated under Part 103. It has one seat and does not exceed 254 pounds, excluding floats and safety devices. In addition, the ultralight can be unpowered, in which case the weight is restricted to 155 pounds.
The powered ultralight’s fuel capacity cannot exceed 5 U.S. gallons. The vehicle should not be able to exceed 55 knots calibrated airspeed at full power and level flight and cannot exceed a power-off stall speed of 24 knots calibrated airspeed. The term also includes two place ultralight training aircraft of 496 pounds or less operated under either the EAA or USUA exemption to FAR Part 103.
a. Be aware that both single and dual seat ultralights in this performance class are not restricted only to FAR Part 103 operation. If they qualify, they can be operated under FAR Part 91, if they meet § 21.191(g) amateur-built category or § 21.191(h) operating kit built aircraft in primary category. Only single seat ultralights of less than 254 pounds empty weight, however, can operate legally under FAR Part
103.
b. Many in the general aviation community view amateur-built and ultralights as one and the same design category, therefore all flight testing procedures should be identical. While in many cases this assumption is true, there are several major differences between the two designs.
(1) Most ultralights are assembled from complete kits, unlike amateur-built aircraft of which the major portion (51 percent) of the aircraft and its component parts are manufactured by the builder.
Most of the kit/ultralight manufacturer’s pilot operating handbooks/flight manuals are usually accurate and address the majority of the information covered
68 5/24/95AC 90-89A in the first eight chapters of this AC. The FAA recommends the pilot’s operating handbook always be consulted by the new owner prior to flight.
(2) The changes in ultralight ownership are more frequent than amateur-built and general aviation aircraft ownership. Although the ultralight is ‘‘used,’’ the new owner is usually unfamiliar with the its operating characteristics. A comprehensive flight testing/training program should be a high priority safety consideration of the new owner.
(3) New flying skills should be developed.
Each ultralight pilot/owner should address the effects smaller size, lighter wing-loading, lower weight, and higher drag designs have on low-speed flight.
c. Due to these differences, the FAA recommends that each ‘‘new’’ ultralight owner design a FLIGHT TEST PLAN regardless if the ultralight was bought, used, and/or the ultralight has a Flight Manual supplied by the manufacturer. The ultralight FLIGHT TEST PLAN does not have to be as extensive as the one recommended for amateur-built aircraft but should address all flight conditions and emergencies called out in the ultralight’s flight manual.
d. With these differences in mind, the next three chapters will address problems associated with both NEW and USED ultralight flight testing. Chapter 8 will address pre-test flight inspection, chapter 9 will cover engine and fuel system operation and inspection, and chapter 10 will cover ultralight flight testing.
e. In keeping with that professional approach towards flight testing, it is suggested that a FLIGHT TEST PLAN and other relevant safety recommendations found in the chapters 1 through 7 be adopted by the ultralight owner/operator prior to test flying a new or used ultralight.
SECTION 2. THE TEST PILOT ‘‘There is always a harder way to flight test an aircraft, but that path does not need to be followed. ’’ George Kaseote, FAA Test Pilot
1. GENERAL. Whether the ultralight is brand new or used, it needs to be properly evaluated. A new owner should enlist the services of an experienced ultralight flight instructor who is authorized to give dual instruction under the EAA or the USUA exemption.
a. The instructor should test fly the ultralight only after it has been properly assembled, inspected, engine run-in, and taxi tests have been performed.
It is not recommended that a ‘‘new’’ pilot and a new/used ultralight ‘‘learn’’ to fly together.
b. The test pilot should be experienced and competent. He/she should have made a minimum of 100 solo flights in similar make, model, and type of ultralight and must follow the FLIGHT TEST PLAN exactly. The FLIGHT TEST PLAN should examine the ultralight and its performance capability, beginning with the pre-flight inspection and ending only after the test pilot has explored the ultralight’s published flight envelope as described in the flight manual.
SECTION 3. PRE-FLIGHT AIRFRAME INSPECTION
1. GENERAL.
a. Ultralight owners should remember that the light-weight, thin wall tubing design of an ultralight fuselage/wing structure is particularly susceptible to metal fatigue. When aluminum tubing has been stressed beyond its elastic limit, it takes on a chalky white appearance (corrosion) at the point of highest stress. Warpage and deformation are other signs of high stress points and once discovered, the ultralight should be grounded until the damaged is repaired.
b. The tolerance limit of a tube or fitting can be significantly lowered by over-torquing a bolt. If a bent or damaged support tube or structure is not repaired, the bend or dent will become a crack, and ultimately the crack will become a structural failure.
69 NOTE: If a used ultralight has been purchased, it is highly recommended that the owner perform a detailed acceptance inspection on the aircraft assisted by an experienced individual who is familiar with the make and model aircraft. It is also recommended that all existing hardware (e.g., nuts, bolts, springs) be replaced with new aviation quality hardware.
c. If possible, remove the fabric envelope and check the airframe structure underneath for dents, cracks, and corrosion. Check the top and bottom of the spars for compression (wrinkled metal) damage.
Double check all wings, landing gear, strut, engine, and tail surface attach points for wear, elongated holes, or damage.
d. If any previous repairs are found, check with the manufacturer to see if damage in that area can be repaired and if the repair that was made is airworthy.
2. CHECKLIST. Each ultralight FLIGHT TEST PLAN should include a pre-flight inspection CHECKLIST. The CHECKLIST should include a step-by-step approach to inspection that covers all the manufacturer inspection items as well as the following suggested items starting at the landing gear.
a. Landing Gear. The landing gear is the last part of the light-weight aircraft to leave the earth and the first part to arrive. Since the majority of these aircraft fly from unimproved strips, the stress on the gear is high. The checklist should include inspection items recommended by the manufacturer and inspection for the following:
(1) The condition of the landing gear attach points and alignment of the landing gear and wheels to the longitudinal axis of the fuselage. If the attach points are mis-aligned, the landing gear will not track in a straight line and this will affect take-offs and landings.
(2) Elongated bolt-holes, loose AN hardware, bent tubing, condition and attachment of wheels, wheel bearings, tire inflation, tire condition and brakes.
(3) Brake condition and operation, including chafing of brake lines/cables against the gear struts.
(4) Condition and operation of the steerable nose gear, if applicable.
(5) Condition and attachment of the tail wheel/skid, if applicable.
b. Wing Assembly. The vast majority of ultralight aircraft use a man-made sailcloth material stretched over a tubular frame. This type of fabric is susceptible to ultra-violet radiation from the sun.
If left unprotected, it can become unairworthy in less than 6 months. The checklist should include the following inspection items:
(1) Ensure the sailcloth has not suffered any tears, or abrasion, due to wear or foreign object damage.
(2) Check the sailcloth for obvious ultraviolet (UV) degrading of fabric strength by examining the condition of the fabric on top of the wing.
Compare it to the fabric on the bottom of the wing.
If the top wing fabric shows a significant difference in color (faded), the fabric should be tested for strength with a fabric tester (Maule or Quicksilver) to see if it tests within the manufacturer’s serviceable limits. If no minimum service limits are listed, the fabric should test out at 46 pounds, or 70 percent or more, of its original tensile strength, whichever is greater, to be considered airworthy. If the fabric fails the tests, it must be replaced before further flight.
(3) Flying and landing support cables should be checked for tension, routing, attach points, and condition. Scrutinize the swaged cable ends. It is recommended that a red reference mark (nail polish works fine) be painted on each of the cables abutting the swaged end. If the cable is growing, i.e., a gap forming between the swaged end and the painted referenced mark, there is an impending failure of the swaged terminal. Do not fly the aircraft until the cable is replaced.
(4) Flight control cables should be checked for frayed wires and proper routing. Run a rag over all of the flying and landing wires and control cables (wings and tail). If the cloth snags, this may indicate a frayed wire which demands further inspection. If possible, bend the cable to form a ‘‘U’’ and inspect for internal broken wires. Also, check the cable pulleys for wear and operation. Extreme wear patterns
70 5/24/95AC 90-89A on pulleys indicate misrouting and must be corrected prior to flight.
(5) Check wing leading/trailing edge, wing struts, aileron, flaps, spoiler hinges and attach points for loose rivets, cracks, elongation and wear. Ensure that all hardware (nuts and bolts) are of aviation quality.
(6) Ensure that the bungee, or return springs for wing spoilers (if applicable), are serviceable and will keep the spoiler down flat against the top of the wing when not being deployed.
(7) Check the aircraft’s flight controls rigging every time the aircraft is re-assembled. It is recommended that the cables/rigging for easier assembly be color coded (e.g., red to red, blue to blue).
(8) Check for corrosion on all metal surfaces. Corrosion on aluminum usually appears as a white powder, rough to the touch. On steel parts, corrosion takes the common form of rust. Dissimilar metal corrosion occurs when two different types of metal make surface contact. To obtain additional information on corrosion and treating it, refer to FAA AC 43.9, ‘‘Corrosion Control for Aircraft.’’
(9) Make sure the leading edge of the wing and tail surfaces are clean and free of insects, grass, or mud prior to flight.
c. Fuselage Assembly. The fuselage is the backbone of the light-weight aircraft. All the flight and ground operating stresses encountered by the wings, tail, landing gear, and engine are transferred to the fuselage at the attach points. Exercise extra care when examining these high stress areas because failure of any of these attach points and associated hardware will cause catastrophic structural failure.
(1) Flight controls should be checked for proper operation, travel, and condition of the stops.
There should not be any sharp bends in the flight control cables.
(2) Check engine controls for proper operation; they should be free of bends and properly secured. Ensure that all control cables are securely clamped to the fuselage to prevent the cable from slipping, hence not transferring the desired movement to the engine control.
(3) Check the instrument panel for security and instruments for attachment, proper operation, and range/limit markings.
(4) Inspect for bent or damaged structural tubing. If a tube is bent, it must be properly repaired or replaced. Straightening out a bend will only workharden the tube in the damaged area and hasten the time of failure.
(5) Fiberglass structures should be checked for cracks, delaminations, and holes -- especially on the bottom of the fuselage.
(6) Examine the seat, seat brackets, and seat belt/shoulder harness, attach points, clips/rings, brackets or tangs and other hardware, for security, safety (cotter pins or safety wire), and condition.
(7) Check the shoulder/seat belt harness for condition and proper operation.
(8) Check the ballistic chute hardware and mounting assembly (review information in chapter 1, section 3).
d. Tail Surfaces. The tail, or empennage group, contains two of the ultralight’s three primary control surfaces: the rudder (yaw control) and the elevator (pitch control). In two-axis ultralights, the elevators are the only flight controls on the tail. Special attention must be given to the attach points, hardware, and proper operation for both control systems.
(1) Ensure that the primary controls and trim systems if applicable, have the proper travel, that control cables are properly tensioned, and that all turnbuckles are safetied.
(2) Examine the control hinges and attach points on the elevator and rudder horn for wear, cracking, and elongation of bolt holes, and security of the rudder and elevator stops.
(3) Check the leading and trailing edges of the flight controls for damage.
(4) Check for wear/UV deterioration to the fabric cover.