4-10 stick, this will result in a cross-control stall and a roll to a near vertical bank attitude at the beginning of a spin with no altitude left for recovery.
4.10.2.12 On final approach, the aircraft speed should be no less than 1.3 but no more than 1.4 times the recorded first flight pre-stall speed. Homebuilt biplanes— high drag aircraft—should use an approach speed of 1.5 times stall speed on landings.
4.10.2.13 Landings, especially the first one in an amateur-built or kit plane, are always exciting. Proceed slowly and do not over control. If the landing conditions are not ideal, be prepared to go around.
4.10.2.14 The actual touchdown should take place within the first 1,000 feet with braking action being applied before the red (abort) flag marker on the runway.
4.10.2.15 After taxiing in, secure the aircraft, debrief the flight with members of the team, and then together perform a careful post-flight inspection of the aircraft.
Note: Remember to allow enough time to absorb what has been learned about the aircraft’s performance and the pilot’s and ground crew’s responses to it.
5-1 CHAPTER 5. THE FIRST 10 HOURS SECTION 1. THE SECOND FLIGHT
5.1 Objective. Reaffirm the first flight findings.
5.1.1 Before the second flight, you should correct all discrepancies noted on the first flight.
Additional ground run-ups, rigging adjustments, or taxi tests may be required. Under no circumstances should a pilot takeoff in an aircraft with known airworthiness problems.
5.1.2 The preflight inspection should be the same as performed for the first flight, including draining the oil and inspecting the oil and fuel screens for contamination.
5.1.3 The second flight, again lasting approximately an hour, should be a carbon copy of the first one, with the exception that all first flight discrepancies are corrected. If problems are not corrected, all further flight testing should be canceled until solutions are found.
SECTION 2. THE THIRD FLIGHT
5.2 Objective. Validate the engine reliability.
5.3 General. The third flight should concentrate on engine performance. Do not forget to record the engine’s response to any application of carb heart, leaning of the fuel mixture, changes to airspeed, and switching fuel tanks.
5.3.1 You should monitor and record engine oil pressure, oil temperature, fuel pressure, and CHTs from 55 percent through 75 percent engine power. At the higher rpm, be sure not to exceed 80 percent of the maximum cruise speed. This action avoids the possibility of encountering a flutter condition. Do not forget to record the engine responses to any applications of carb heat, leaning the fuel mixture, changes to the power settings, such as rpm and manifold pressure, changes to airspeed, and switching fuel tanks. Certain EFIS and MFD can record these events automatically and make them available for viewing at any time.
5.3.2 Resist the temptation to explore the more exciting dimensions of flight. Stick to the flight test plan and perform a conscientious evaluation of the engine. After landing, review the data with ground crew members. Make adjustments as needed, perform another post-flight inspection of the aircraft, and record oil and fuel consumption.
5.3.3 After 3 hours of flight testing, the pilot should be able to confirm that the aircraft is stable and the engine is reliable in cruise configuration.
5.3.4 If installed, calibrate the angle of attack indicator (AOAI) or lift reserve indicator as per the manufacturer’s instructions and use it during all subsequent flights. This will require wings-level stalls in various flight configurations. Be sure to climb to a safe altitude of at least 5,000 feet AGL before performing these tests.
5-2 Note: In an effort to reduce maneuvering accidents in all aircraft the FAA and the EAA strongly urge all amateur builders to install an AOAI or lift reserve indicator in their aircraft and learn how to use it effectively. Since most experimental amateur-built aircraft do not have any stall warning device installed, the AOAI can fulfill the need to serve that safety function. In addition, it is very useful to determine best angle and rate of climb airspeeds and best glide airspeed. The potential life-saving benefit of these devices should not be underestimated.
SECTION 3. HOURS 4 THROUGH 10
5.4 Objective. Build on data established by the first 3 hours and start expanding on the flight test envelope in a thorough and cautious manner. This operational data will be added to the AOH.
5.5 General. These next seven 1-hour test segments should confirm the results of the first 3 hours and explore/include:
1. Gear retraction, if applicable.
2. Climbs and descents to preselected altitudes, and monitoring of engine performance.
3. Airspeed indicator in-flight accuracy check.
Note 1: After each test flight, all discrepancies are cleared before the next flight.
You also thoroughly inspect the aircraft before the next flight.
Note 2: The FAA recommends that all flight test maneuvers be preceded with two 90-degree clearing turns to ensure that the flight test area is free of other aircraft.
5.6 Gear Retraction.
5.6.1 Before you retract the gear in flight for the first time, the FAA advises that you put the aircraft up on jacks and perform several gear retraction tests, including the emergency gear extension test. These tests will determine if, in the last 3 hours of flight testing, any structural deformation or systems malfunctions have occurred. Added to the gear retraction test, the pilot/chase pilot/ground crew should use this time to review the aircraft’s kit/designer instructions and emergency checklist procedures for malfunctioning gear and plan accordingly. If at any time the aircraft has suffered a hard landing or side loading on the gear during flight testing, the aircraft and its gear should be tested for operation and condition on the ground.
5.6.2 You should conduct the first gear retraction test with the aircraft flying straight and level at or above 5,000 feet AGL, over an airport or emergency field. The airspeed should be well under the maximum landing gear retraction airspeed. When the gear is being retracted, note if there is any tendency for the aircraft to yaw, pitch, or roll. Record what changes to the aircraft’s trim are required to maintain straight and level flight. If there are no adverse flight reactions or system malfunctions, cycle the gear several times. When
5-3 satisfied with the straight and level gear retraction test, try an emergency gear extension, but only if this is practical.
5.6.3 With the gear extended, slow the aircraft to 1.3 times the predetermined stall speed, stabilize, lower the flaps to the takeoff position, trim, and maintain straight and level flight.
5.6.4 Simulate a normal takeoff by increasing rpm to full power. Raise the nose 3 degrees, trim, and then retract the gear. Observe the following: aircraft reaction, such as pitch or roll; length of time for gear to retract; trim requirements, and the time necessary to climb 1,000 feet higher in altitude before leveling off.
5.6.5 Practice a simulated takeoff several times to confirm that the aircraft’s response is predictable and the gear retraction system is mechanically reliable.
5.7 Climbs and Descents. These tests monitor engine performance and reliability. The pilot should start the test only after the aircraft has been flying straight and level for a minimum of 10 minutes. This time in level flight will help stabilize engine oil pressure and temperatures. Engine oil pressure and temperatures should be kept within the manufacturer’s limits at all times during these tests. High summer temperatures restrict the flight test program because both oil and CHTs will increase 1 degree for each 1-degree increase in outside temperature. As applicable, an EFIS, MFD, or paper log should be utilized for recording the following indications below.
5.7.1 Climbs. Start the first climb at a 15-degree climb angle, full power, at a predetermined altitude. Maintain the climb angle for 1 minute. Record the engine temperatures and pressures. Reduce power, stabilize the engine temperature, and repeat the test. For the second climb test, the flight test plan should call for increasing the climb time. Record the results of the second climb test. When satisfied that an engine-cooling problem does not exist at the 1-minute duration, repeat the tests increasing the duration until the pilot has:
1. Reached 15 degrees climb angle and whichever occurs first;
2. Has been in climb for 5 minutes at full throttle; or
3. Encountered an engine manufacturer’s limit.
5.7.2 Descents. Should begin above 5,000 feet AGL with both the engine temperatures and pressures stabilized.
5.7.2.1 The test pilot should apply carb heat and also clear the airspace below the aircraft before starting the descent. The first descent should be at a shallow angle, at low rpm and last for 30 seconds, not exceeding 1.5 times the estimated stall speed of the aircraft. During long, low-power descents, the pilot should be aware of rapid engine cooling, usually marked by a large drop in oil temperature and CHT. If a noticeable drop occurs, increase the engine rpm and reduce the angle of descent. If not corrected, the repeated rapid cooling of the engine may cause thermal shock to the engine cylinders and eventually cause cylinder head cracking or seizure.
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5.7.2.2 Conduct each test as before, but increase the time by 30 seconds until you either are: (1) limited by the engine manufacturer’s restrictions, or (2) you reach a 5-minute descent. Record temperatures, pressures, altitudes, and airspeed data for climbs and descents for addition into the AOH.
5.8 Airspeed In-Flight Accuracy Check. The following procedures are commonly used to calibrate airspeed:
5.8.1 The measured course method uses a stopwatch with readily identifiable landmarks at each end. The landmarks should be a known distance apart, and the length of the course should be at least 1 to 2 miles long.
5.8.1.1 The pilot should fly a precision course, maintaining a constant altitude, such as 1,000 feet, constant airspeed, constant magnetic heading, and constant engine rpm. The pilot should record the temperature, altitude, indicated airspeed and the time over each landmark for both directions. The average of these speeds is the ground speed of the aircraft. An E6B computer will convert the temperature, altitude, and ground speed into true indicated airspeed for the tests.
5.8.1.2 The air should be as smooth as possible with a minimum of turbulence and wind. The wind velocity, while conducting the test, should not exceed approximately 10 knots.
5.8.1.3 The pilot should make several airspeed calibration runs in opposite headings for selected airspeeds the pilot wants to check. Such accuracy test runs should start at the lowest safe airspeed and work up to cruise speed using 10-mph/knot increments. Most errors will be found at the low end of the speed range due to the angle of the pitot mast to the relative wind and/or the location of the static ports.
Note: Flight testing of all amateur-built aircraft is restricted to a flight test area. If a pilot needs to run additional aircraft tests requiring more airspace, the pilot should notify FSDO personnel who issued the aircraft’s operating limitations, and request a change to those limitations. The FAA reminds you that the pilot must operate an experimental aircraft in accordance with the aircraft’s operating limitations. Otherwise, the FAA may take certificate action.
5.8.2 The Global Positioning System (GPS) method provides an accurate and easy-to-use means of determining speed during the flight test period. Since it measures ground speed it will be necessary to calculate true airspeed, and from that confirm indicated airspeed.
5.8.2.1 A triangular course with each leg 120 degrees apart from the previous one will ensure accurate results in any wind condition. The ground speeds from each of the three legs should be averaged to get the no-wind ground speed, which is equal to the true airspeed.
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5.8.2.2 A true airspeed can be calculated using an E6B or other aviation computer if the indicated airspeed, temperature, altitude, and barometric pressure are noted for each test course. This true airspeed can be compared to the previously determined no-wind ground speed in step one for clarity.
5.8.2.3 The pilot should fly precisely during these tests to get accurate numbers.
Altitude, airspeed, heading, and engine rpm need to be held as steady as possible during each test. Allow the aircraft to stabilize for at least one minute after any change in heading, altitude, or power setting before taking a speed reading.
5.8.2.4 Most errors will be found at the low end of the speed range due to the angle of the pitot mast to the relative wind and/or the location of the static port(s).
5.8.3 If the aircraft has retractable gear or flaps, test the accuracy of the airspeed indicator using the applicable method with the gear/flaps up and down.
5.8.4 Record all the data in a log if not automatically recording on an electronic primary flight display (PFD) unit.
6-1 CHAPTER 6. EXPANDING THE ENVELOPE SECTION 1. GENERAL
6.1 Objective. Move from a known flight environment to an unknown flight environment using a series of planned and carefully executed steps.
6.1.1 Before beginning the next series of test flights, the FAA highly recommends that the aircraft undergo the same condition inspection that would normally only be done annually at this time. The FAA strongly recommends that the builder and/or pilot take the time to inspect the aircraft because within the previous 10 hours, the test pilot has subjected the aircraft to a “shakedown cruise.”
6.1.2 During the inspection, check the torque paint marks on the engine mounts, propeller bolts, and landing gear. Double check the flight control hinges and rod end bearings for attachment and play. Check all cable installations, cable tension, and control travel, and complete all the standard inspection and maintenance items. This inspection also should include checking the oil and fuel filters for metal or other forms of contamination.
6.1.3 Even if there have been no indications of CO contamination, perform another CO test using the floodlight procedure—review Chapter 2, Section 7—or an industrial CO test meter. There is a strong possibility that operational vibration and landing stresses may have opened new paths for CO to enter the cockpit.
SECTION 2. HOURS 11 THROUGH 20
6.2 O bjective. Focus the next 10 hours of flight testing on stall speed, best rate of climb speed, best angle of climb speed, and slow flight. The FAA recommends that stall speed tests be conducted with the aircraft’s fuel tanks full.
Note: Stall speeds, best rate of climb, best angle of climb, best glide speed, and various slow flight maneuvers are best and most safely performed with the aid of an AOAI. The installation, calibration and proper use of such a device is highly recommended.
6.2.1 As with any unknown, approach flight testing slowly, incrementally, and follow the flight test plan. The stall test objective is to verify the aircraft conforms to the expected responses for this particular design in this flight regime. Acquire a thorough description of how the aircraft is expected to behave near, at, and after stall. This provides a reference point to compare against the flight test results. To improve safety and reduce the possibility of spins, the aircraft should be tested with a forward CG loading. Starting the stall tests at 8,000 feet above ground level (AGL) is good for most homebuilts, but it depends on the aircraft type. Make clearing turns and stabilize the airspeed and altitude.
The first full stall should be conducted with power off, no flaps, and gear up if applicable.
After clearing the area, reduce the airspeed to 1.3 times the predicted stall speed and trim.
Note 1: Make sure the engine’s idle speed is properly set; faster idle speeds result in higher nose-up attitudes and lower indicated stall speeds.
6-2 Note 2: Don’t trim within 10 knots of stall.
Note 3: Some clean, high performance aircraft may not have any noticeable pre-stall buffet. The actual stall may be abrupt and violent with a large amount of wing or nose drop.
6.2.2 The preferred pre-stall and stall behavior is an unmistakable warning buffet starting lightly about 5 to 10 mph/knots above the eventual stall speed, growing in intensity as the aircraft slows down.
6.2.3 The desired stall characteristics should be a straight forward nose drop with no tendency for roll or pitch up. This docile and forgiving behavior implies a stall that has started at the wing root and progressed smoothly outboard. The buffet warns the pilot about separated airflow over the wings and or tail in the form of the buffet. The ailerons will continue to operate in the attached air flow until the aircraft’s stall speed is reached and the wing stalls.
6.2.4 Use the same procedures as on the first flight. Secure cockpit items and use carb heat.
Begin by stabilizing in level flight at 15–20 knots above the predicted stall speed. When stable, make a control input in each axis; roll, pitch and yaw. The inputs should be just enough to generate about 3–5 degrees of aircraft response, then move the controls right back to neutral (usually a 1–2 second input pulse).
6.2.4.1 Then watch for the aircraft response. In roll, is there any accompanying adverse yaw? Does the aircraft stop rolling when the input is released to neutral? In pitch, does the aircraft return to the previous attitude? Is there any tendency for the pitch to continue to rise after releasing the stick? Does the pitch attitude continue to oscillate? The same questions apply in the yaw axis.
If all is as expected, slow 3–5 knots and repeat the process.
6.2.4.2 At each incremental airspeed point ensure that you still have nose down control authority, since that is your most important recovery input. Make note of any changes in response as the aircraft gets slower (it is normal for the aircraft to be more sluggish, but it should still respond positively). Make note of any warning cues. Watch closely for any uncommanded motions. At the first sign of any uncommanded motion (nose rise, or nose slice, wing rock, or nose drop), recover the aircraft by lowering the nose, adding power and increasing speed. Uncommanded motions are likely linked to being at a higher AOA than previously flown. The most correct initial response is to lower that AOA with a nose down input. Even if the uncommanded motion is a roll off, the quickest way to stop it is most likely a pitch down, not a countering roll input. After the airspeed increases and the aircraft still continues to roll, use opposite rudder to stop it with ailerons neutralized.
6.2.5 If there are no surprises down to 3–5 knots above expected stall speed, then continue to a complete stall by applying backpressure on the stick/yoke to slow the airplane down at
6-3 roughly 1 knot/mph per second. Stall warning should occur about 5 knots/mph before the stall itself. Do not depend too much on an uncalibrated stall warning system.
6.2.5.1 As the airplane decelerates, ensure that the airplane requires an increasingly heavier pull force. If the force lightens or changes to a push force, abandon the test. Once you get to the stall, initiate recovery and record the altitude required to return to level flight as well as the stall speed. Also make note of aircraft responses during the recovery such as wing rock, secondary stall or any uncommanded motions. All these observations need to be compared in your post-flight analysis to the expected behavior written down before the test.
Note: Some airplanes reach the up elevator stop before the wing stalls.
This is acceptable as long as the elevator has the authority to flare the aircraft at its maximum landing weight with the forward most CG allowed for that weight. Also, at the stall, many airplanes tend to roll toward one wing or the other. A properly designed and rigged airplane will be able to maintain the wings within 15 degrees of level with normal aileron inputs. Make sure you’re not cross-controlling the airplane (the slip-skid ball is centered). If you need excessive aileron or rudder inputs to keep the airplane straight and the wings level, abort the test. On the ground assess the airplane for misrigging or some inadvertent wing twist or asymmetry.
6.2.6 Practice the same stall sequence several times at a ½-mph/knot-per-second deceleration rate to determine the power off, 1-G stall speed. Practice the same stall series with flaps, starting with the lowest setting first and working slowly to the full flap configuration.
Record the findings.
6.2.7 After exploring the stall and recovery behavior in a slow deceleration with ball centered, try a series of stalls with flaps up and flaps down, with a faster deceleration. Do not exceed the deceleration rate expected in normal operations.
6.3 Stalls.
6.3.1 Po wer -On Stalls. As before, use the same procedures moving from the known to the unknown. Increase power incrementally and run a stall test at each new power setting until full power is reached. We do not advise jumping straight from idle to full power with the resultant large changes in pitch attitude, torque reaction, and slipstream effect on the wing and tail.
6.3.2 Conducting Power-O n Stalls. The FAA recommends that you stabilize the aircraft in level flight at low cruise power. The power-on stall is reached by slowly increasing the power to the desired power setting. The pilot then steadily increases the pitch attitude until the aircraft experiences the stall buffet. Remember to keep the ball centered until the onset of the stall buffet.
6.3.2.1 T he power-on stall may be more likely to cause a wing drop than one at idle.
This is due to torque reaction and because the propeller slipstream tends to
6-4 keep the flow of higher velocity air over the inboard, or root, section of the wing despite the higher AOA. This allows the root portion of the wing to continue flying after the wing tip stalls, dropping a wing.
6.3.2.2 Tip stalls usually do not give advance warning and will almost invariably result in severe wing drop. These stalls are more likely to result in a spin, even if the controls are not mishandled. If the spin does not develop, considerably more height will be lost in the recovery than if the stall had been straight-ahead nose down.
6.3.2.3 If the pilot yields to instinct and tries to correct the wing drop with aileron, it could result in a spin. Since a sharp wing drop could be regarded as the onset of spin auto-rotation, the recommended corrective action is reducing power, full opposite rudder, and lowering the nose to the horizon or below. Take care to avoid this situation until the aircraft’s spin behavior has been tested.
6.3.2.4 Perform the same sequence of events for power-on stalls as power-off stalls, unless limited by the designer’s instructions. Record all findings in a log if not automatically recording on an electronic PFD for the flight manual.
Note: Aircraft with retractable gear will have to go through a separate series of slow flight and stall checks with gear extended, with and without flaps. Record the different stall speeds for each configuration in the AOH.
Figure 6-1. Climb Airspeed and Altitude Graph
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6.3.3 B est Rate of Climb Speed Tests. To determine the best rate of climb for the aircraft, the FAA suggests the following procedures:
6.3.3.1 P erform the tests in smooth air, free from thermal activity. Select an altitude such as 1,000 feet AGL, as a BASE attitude. Use a heading 90 degrees to the wind, and for the best results, reverse the heading 180 degrees after each climb test.
6.3.3.2 Begin a full throttle climb well below the predetermined BASE altitude and stabilize at a preselected airspeed approximately 15 mph/knots above the predicted best rate of climb speed. As the aircraft passes through the base altitude, begin a 1-minute time check.
6.3.3.3 After 1 minute, record the altitude gained. Descend down below the base altitude. Decrease the airspeed by 5 mph/knots and run the test again. After each succeeding test, the pilot should decrease the airspeed by 5 mph/knots until reaching an airspeed that is 10 mph/knots higher than the stall speed of the aircraft. Record the airspeed and altitude gained for each climb on a graph similar to Figure 6-1. The airspeed that shows the greatest gain in altitude is the aircraft’s best rate of climb speed (VY).
Figure 6- 2. Best Rate of Climb Speed Graph
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6.3.4 Best Angle of Climb Speed Tests. You can find the best angle of climb speed can by using the same chart developed for the best rate of climb tests. Draw a line (tangent) from the zero rate of climb feet per minute (see Figure 6-2) outward to a point on the rate of climb airspeed curve. The airspeed that the line intersects is the best angle of climb airspeed.
6.3.5 S low Flight Test. For added safety, the slow flight tests should be performed at 6,000 AGL or higher to allow room for spin recovery. These tests primarily show the pilot the aircraft’s handling qualities at the minimum gear up/down airspeeds and power settings.
6.3.5.1 You should do the tests with and without flaps. Start the tests at an airspeed of
1.3 times the stall speed of the aircraft. Once the aircraft is stabilized and maintaining its altitude, reduce the airspeed by 5 mph/knots. Maintain the altitude. Keep reducing the airspeed until approaching a stall.
6.3.5.2 Maintain 5 mph/knots above the previously determined stall speed; this is the initial slow flight airspeed. Practice with each flap setting, noting its effect on the aircraft’s performance. If the aircraft has retractable gear, test in all gear and flap combinations. These tests will have to be run later in the flight test program—but with the aircraft at gross weight—to determine the actual slow flight airspeed and stall speeds.
6.3.5.3 Remember, to help reduce the possibility of unplanned stalls in slow flight configurations, avoid bank angles of more than 5 degrees. When all the test data has been evaluated, and if the aircraft is equipped with a stall warning horn or indicator, set the stall warning at 5 mph/knots above the aircraft’s highest stall speed.
SECTION 3. HOURS 21 THROUGH 35: STABILITY AND CONTROL CHECKS
6.4 Objective. Determine the aircraft’s stability limits and range of control.
6.5 General. You should do two things before declaring that the aircraft is controllable throughout the normal range of speeds per part 91, § 91.319, Aircraft Having Experimental Certificates: Operating Limitations.
6.5.1 F irst. Perform another complete inspection of the aircraft, including oil changes and fuel system filter checks.
6.5.2 S econd. Carry out a close examination of the stability and control characteristics of the aircraft. Stability and control checks will be centered around the three axes of the aircraft:
longitudinal or roll axis (ailerons), the lateral or pitching axis (elevators), and the vertical or yaw axis (rudder).
6.5.3 A ll Tests Need a Starting Point. The starting point for stability and control checks is called the state of equilibrium. An aircraft is said to be in a state of equilibrium when it