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b. The basic technique used to get a clean spin entry is to continue to reduce airspeed at about a 1-mph/knot-per-second rate in level flight, carburetor heat on, and the power at idle.
(1) As the aircraft stalls, APPLY FULL RUDDER in the desired spin direction, followed immediately by full aft movement of the control stick keeping the ailerons neutral.
(2) The transition from a horizontal to a vertical flight path takes approximately three or four turns and is referred to as the incipient stage of the spin.
(3) During the incipient spin, the dynamic and inertia forces have not achieved equilibrium. Many aircraft can recover from the incipient spin phase, but may not be able to recover from a steady spin.
(4) The normal spin recovery technique is to apply full rudder opposite to the direction of yaw (check the turn needle). Move the control stick smoothly and fairly rapidly forward towards the instrument panel until the rotation stops.
(5) Quickly center the rudder and ease out of the dive. Do not attempt to pull up too rapidly because the structural limits of the aircraft can easily be exceeded, or the aircraft can stall again. Recover from the first deliberate spin after a half a turn.
(6) If the aircraft is not built for aerobatics, no further spin testing is required. It is recommended the instrument panel be placarded “SPINS PROHIBITED.”
(7) If further spin testing is required, it is strongly recommended the services of a professional flight-test pilot be used.
SECTION 6. ACCELERATED STALLS “Does it pass the Common Sense test?” U.S. Air Force, Thunderbird
5-12. OBJECTIVE. To further explore the stall characteristics of the aircraft.
a. An accelerated stall is not a stall reached after a rapid deceleration. It is an in-flight stall at more than 1 G, similar to what is experienced in a steep turn or a pull up.
NOTE: Do not attempt this or any other extreme maneuver unless the designer or kit manufacturer has performed similar tests on a prototype aircraft identical to the amateur-builder’s aircraft.
b. The two standard methods for accelerated stalls are the constant G (constant bank) and constant speed (increasing bank). Most preferred of the two is the constant bank method in which the airspeed is decreased and the angle of bank is held constant, until the aircraft stalls. It is the most preferred because the potential violence of any accelerated stall is largely governed by the increasing g load and airspeed.
c. Performing recommended constant bank method. First, review the techniques described for wing level stall tests card and apply them here as well. If you are not spin-qualified
Par 5-12 Page 75 and comfortable, hire a professional test pilot for these tests. Start with light forward CG. The amount of fuel in the tanks while performing the stall test should be enough fuel for 1 hour minimum.
(1) Normal takeoff and climb to 8,000 feet AGL.
(2) Verify engine readings in the green.
(3) Trim airplane to 1.5 times estimated stall speed.
(4) Set the flaps (and landing gear) appropriate to test.
(5) Power to idle (carb heat if applicable).
(6) Establish—and maintain—a coordinated 30-degree bank turn.
(7) Decelerate at 1 knot/mph per second.
(8) Note positive stick/yoke force: it should increase.
(9) Note control reversal: abort if evident.
(10) Note speed of pre-stall buffet.
(11) Recover, climb to starting altitude, and continue series until complete.
(12) At stall, note indicated airspeed, pitch changes, roll direction, and amount.
(13) Recover, climb to starting altitude, and continue series until complete
(14) You should have a detailed description of the expected behavior in an accelerated stall available (either from the kit manufacturer or through design analysis) prior to beginning the test. The objective is to verify (or not) that the behavior of your aircraft matches the expected behavior.
d. Make separate test flights to evaluate the airplane’s performance at different weights and CG locations. Start with lighter gross weight and forward CG locations. Each test series includes six runs, left and right coordinated turns with the indicated flap settings. If your airplane has retractable gear, run the series with the gear up and down.
(1) For each stall test fly the aircraft at a safe altitude (8,000 feet AGL or as appropriate for aircraft type, in smooth air), trim the airplane to 1.5 times the predicted stall speed and set the flaps as required for the test (this should be slower than VFE).
(2) Apply carburetor heat (if required), pull the power to idle, and establish a coordinated turn in a 30-degree bank; ensure the slip/skid ball is centered. Reduce speed to 10 knots/mph above the straight and level stall speed for that flap setting. Then decelerate at 1 knot/mph per second.
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(a) As the airplane slows, make sure it requires an increasingly greater stick/yoke pull force. If the force lightens or changes to a push force—abort the test. This may indicate an aft CG location or insufficient elevator authority. Either of these may cause the nose to pitch up at stall.
(b) As the airplane slows, normal control inputs should maintain the 30-degree bank attitude and nose position. When you feel the pre-stall buffet, note the speed, roll level, and recover to straight and level flight.
NOTE: Stalling the airplane is a personal decision that should be based on the wing drop it exhibited in your wings-level stall tests. Accelerated stalls usually exacerbate this roll, especially when you’re turning to the direction the wing drops. Even a properly rigged airplane may roll up to 60 degrees into the turn, or up to 30 degrees in the opposite direction. If the possibility of a roll to 60 degrees is deemed unsafe—do not perform this test.
Par 6-1 Page 77 CHAPTER 6. PUTTING IT ALL TOGETHER: 36 HOURS TO —————?
“Beware of false knowledge; it is more dangerous than ignorance.” George Bernard Shaw SECTION 1. MAXIMUM GROSS WEIGHT TESTS
6-1. OBJECTIVE. To develop aircraft performance data across the weight and CG ranges.
a. Up until this point, all tests have been performed well below the test aircraft’s maximum gross weight, with the possible exception of single seat aircraft designs. A complete series of flight tests at maximum gross weight from stalls, rates of climb, angles of climb, stability, retraction tests, slow flight, through accelerated stalls should be investigated.
b. These tests should demonstrate that the aircraft has been successfully flown throughout the CG range, and will operate in and at the full range of aircraft weights from minimum to full gross weight. The findings should be documented in the aircraft’s flight manual.
c. Each phase of the testing should be done slowly, incrementally, with the same careful attention to detail that should characterize all the flight testing.
d. Increases in the aircraft weight should be done in a series of steps. Usually, 20 percent increments of the maximum payload (e.g., sandbags, lead shot) are added in the aircraft to simulate passengers or baggage weight. The pilot should carefully weigh and secure the ballast. A new weight and balance and CG location must be worked for each new increase in weight. Stop testing when the aircraft’s maximum gross weight is reached.
e. The testing up to this point has been done at, or near, the forward CG limit. During these tests, the CG should be slowly, but progressively, moved aft between each test flight. Limit the change to the CG range to about 20 percent of the range. Again, the pilot should weigh the ballast and work a new weight and balance for each flight. With each CG change, the aircraft longitudinal static stability and stall characteristics should be carefully evaluated by using the same technique discussed earlier. Stop testing when the designer’s or kit manufacturer’s aft CG limit is reached.
f. If the aircraft develops either a neutral or negative longitudinal stability problem, or the aircraft displays unsatisfactory stall characteristics at any CG location being tested, STOP FURTHER TESTING!
g. These tests should confirm the designer’s aft CG limit or establish the last satisfactory aft CG location. If the aft CG range is not satisfactory, consult with the kit manufacturer, aircraft designer, or a flight-test engineering consultant.
h. The pilot should avoid the temptation to take a live ballast weight up for a ride for three reasons:
(1) The aircraft has not been proven safe for the higher gross weights.
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(2) The pilot and passenger are at great risk. It is a sure sign the pilot has become complacent and sloppy in his flight-test program.
(3) In most cases unless otherwise approved by the FAA the pilot will be in violation of the Operating Limitations for Phase I flight testing that if discovered will result in an enforcement action.
i. Pilots should ensure that the added ballast weight in the cockpit is secured. A seat belt over some sand bags will not stop the weight from shifting and getting loose in a cockpit. The last thing a test pilot needs is a 20-pound lead-shot bag free in the cockpit during a climb test, a landing, or a spin. Tie each weight down individually, and cover all the weights with a cargo net.
j. Ensure the ropes/nets and airframe attach points are strong enough to take the added load. Make sure the passenger seat can take that much localized weight safely.
k. The maximum gross weight test results should be recorded in the flight manual. If there are any changes to the stall speed initially marked on the airspeed indicator, it should be changed to reflect the aircraft stall speed at maximum gross weight.
SECTION 2. SERVICE CEILING TESTS “Man is made for error; it enters his mind naturally and he discovers a few truths only with the greatest effort.” Frederick the Great
6-2. OBJECTIVE. To determine the highest altitude at which an aircraft can continue to climb at 100 feet per minute (service ceiling).
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a. Pilots who wish to determine the actual service ceiling of their aircraft are offered the following suggestions:
(1) Ask the local FSDO to amend the Operating Limitations to permit a climb to the aircraft’s service ceiling, if that altitude is above 18,000 feet.
(2) Contact the local Flight Service Station (FSS) or ATC facility, and reserve a time and airspace to make the test.
(3) Install a transponder (refer to part 91, § 91.215) or get a waiver.
(4) Install a portable oxygen bottle, if plans are to go above 12,000 feet. (Recommend the pilot becomes familiar with the symptoms and cures of hypoxia and hyperventilation.)
(5) Review the engine manufacturer’s mixture leaning procedures.
(6) Maintain communications with an air traffic facility at all times.
b. The climb to the aircraft service ceiling should be made in a series of step climbs during which engine performance, temperatures and pressures are recorded. At the slightest indication of engine performance or aircraft control problems, the pilot should terminate the test and return to the airport.
SECTION 3. NAVIGATION, FUEL CONSUMPTION, AND NIGHT FLYING “That’s one small step for a man, one giant leap for mankind.” Neil Armstrong
Par 6-3 Page 80
6-3. 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.
(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/navigation 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.
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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 online at:
http://www.faa.gov/air_traffic/publications/ATpubs/AIM/index.htm. The following is an abbreviated summary of the VOR procedure in the AIM.
(1) For a ground test of the VOR, you must use a VOR test facility (VOT). To use the VOT service, tune the VOR receiver to the VOT frequency, normally 108 MHz. With the course deviation indicator 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: You can find the VOT facilities closest to the flight-test location in the FAA’s Airport/Facility Directory publication, available in digital format for a charge from the FAA at http://www.faa.gov/air_traffic/flight_info/aeronav/productcatalog/digitalpro ducts/dafd/, or by contacting a 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.
(a) 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.
(b) If the aircraft has dual VORs, the maximum permissible variation between the two receivers is 4 degrees.
c. Fuel Consumption. The amount of fuel consumed is 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 racetrack 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 racetrack 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.
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(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. You should conduct night operations during Phase II using the aircraft’s FAA operating limitations and limiting operations to normal climbs and descents, such as rates of 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. However during Phase I there are some checks you should perform prior to accomplishing night operations in Phase II.
(1) Some night testing requirements should be determined on the ground during Phase I. For example:
(a) The electrical load review of lights, pumps, instrumentation, and avionics did not exceed 80 percent of the aircraft’s charging system capacity.
(b) The cockpit instrumentation lighting is adequate and was tested for reliability of operation during daytime flights.
(c) The pilot has at least 30 minutes of night-time practice taxiing the aircraft.
The pilot needs this practice to familiarize the pilot with a different operating environment. Do not exceed engine operating temperatures during taxiing.
(d) The position and brightness of instrument panel lights, anti-collision strobe lights, and rotating beacons will not adversely affect the pilot’s night vision.
(2) Once Phase I flight testing is complete the main concern for initial night testing during Phase II should be the availability of a horizontal reference, such as a bright moon or artificial horizon.
(3) Before every night flight, place a reliable flashlight with fresh batteries and a set of flight-test plan procedures on board.
(4) The first actual night flight should be conducted with a single pilot and no passengers on board.
(5) 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, takeoff, and landing. The pilot should note any glare on the windshield or light flicker on the instrument panel.
Par 7-1 Page 83 CHAPTER 7. THOUGHTS ON TESTING CANARD TYPE AMATEUR-BUILT
AIRCRAFT “FLY.” Jonathan Livingston Seagull SECTION 1. CANARDS
7-1. OBJECTIVE. To discuss canard flight characteristics.
a. Canard configured aircraft generally fall into two 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 its critical AOA and continues to fly. This self-limiting stall characteristic prevents spins in a properly designed and built canard aircraft. You should note that the accident rate for canard designs are about the same as conventional designed amateur built aircraft because of the following:
(1) During takeoff, 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 takeoff characteristics than conventional configured aircraft. Canard aircraft with pusher propellers need a substantially higher rotation speed on takeoff.
(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 takeoff 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:
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(a) The load carried by the nose wheel, plus
(b) 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 takeoff roll.
(7) Since the main wing may reach flying speed before the canard, the nose wheel will stay firmly on the runway until takeoff 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 takeoff).
(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 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 HP 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.
SECTION 2. FLIGHT TEST CONSIDERATIONS.
7-2. GENERAL. 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 CG problems, the main wing may stall before the canard surface. In this case, extreme pitch-up can occur until the canard surface
Par 7-2 Page 85 (and 86) 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.
(1) 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.
(2) Neutral pitch stability is achieved when the aircraft remains in the pitch attitude attained when a control force is applied.
(3) 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 CG carefully calculated. At the same time, determine the weight needed and the moment calculated to load the aircraft at the most forward and aft CG limits recommended by the designer. Beginning at the most forward CG, 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 CG further aft and observing the tendency of the aircraft. At some point near the aft CG 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 CG 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 CG to be adjusted forward or aft during flight. If testing is to be accomplished outside the recommended range, it is advisable to consider the installation of a ballistic recovery system or spin parachute system. In addition, the pilot should make a decision about leaving the aircraft if the test becomes unmanageable.