After looking at EFIS data uploaded to SavvyAviation's web site, trying to see if there were speed and cooling improvements, found it was difficult to glean from different flights since the altitude, power setting, CG varied quite a bit.
I asked Grok how to establish a baseline and got this:
To establish a performance baseline for speed improvements on an experimental aircraft, follow a systematic, repeatable, and data-driven approach. The goal is to create a reliable reference point for the aircraft’s current speed performance under controlled conditions, which you can use to measure the impact of modifications. Here’s how to do it effectively:
- Define Key Performance Metrics:
- Focus on speed-related metrics such as maximum level speed, cruise speed, climb rate, and acceleration time to a specific speed (e.g., time to reach 200 knots).
- Include related parameters like fuel consumption, engine RPM, and airspeed (indicated, true, and ground speed) to provide context.
- Specify units (e.g., knots, mph, or km/h) and ensure consistency across measurements.
- Standardize Test Conditions:
- Environment: Conduct tests in consistent weather conditions (e.g., calm winds, standard temperature, and pressure). Use a day with minimal turbulence and stable atmospheric conditions (e.g., clear skies, no significant thermal activity).
- Altitude: Test at a fixed altitude (e.g., 5,000 ft above sea level) to minimize variations in air density. Record density altitude for each test.
- Weight and Balance: Ensure the aircraft is at a consistent weight, including fuel, payload, and pilot. Use a standard configuration (e.g., 50% fuel, solo pilot) and document the center of gravity.
- Configuration: Test with a fixed aircraft configuration (e.g., flaps up, gear retracted if applicable, and a specific propeller setting for variable-pitch props).
- Use Precise Measurement Tools:
- Airspeed: Use calibrated onboard instruments (e.g., pitot-static system) and cross-check with GPS-derived ground speed, adjusted for wind.
- Data Logging: Employ a flight data recorder or avionics system (e.g., Garmin G1000, Dynon SkyView) to log airspeed, altitude, engine parameters, and GPS data at regular intervals (e.g., 1 Hz).
- External Validation: If possible, use ground-based radar or a chase plane with calibrated instruments to verify speeds.
- Time Trials: For specific tests (e.g., acceleration), use a stopwatch or automated timing system synced with GPS.
- Conduct Controlled Flight Tests:
- Test Plan: Develop a detailed flight test plan with specific procedures for each test. For example:
- Max Speed Test: Fly level at full power for a set distance (e.g., 10 nautical miles) in two opposing directions to average out wind effects.
- Cruise Speed Test: Fly at a fixed power setting (e.g., 75% power) and record stabilized speed over a set time or distance.
- Climb Rate Test: Measure time to climb between two altitudes (e.g., 3,000 to 5,000 ft) at a constant airspeed or power setting.
- Repetition: Perform each test at least three times to ensure repeatability and calculate average values. Discard outliers only if there’s a clear error (e.g., instrument malfunction).
- Flight Path: Use GPS to maintain a consistent flight path (e.g., straight and level or a specific climb angle). Fly in areas with minimal air traffic to avoid deviations.
- Document and Normalize Data:
- Record all relevant data, including airspeed, ground speed, altitude, temperature, pressure, wind speed/direction, and aircraft configuration.
- Normalize data to standard conditions (e.g., sea-level equivalent speed) using formulas like true airspeed (TAS) calculations:
\text{TAS} = \text{IAS} \times \sqrt{\frac{\rho_0}{\rho}}whereis indicated airspeed,\text{IAS}is sea-level air density, and\rho_0is actual air density at test altitude.\rho - Account for wind by averaging speeds from reciprocal headings or using GPS ground speed with wind vector corrections.
- Establish the Baseline:
- Compile the averaged, normalized results into a performance baseline. For example:
- Max speed: 180 knots TAS at 5,000 ft, 100% power, 50% fuel.
- Cruise speed: 160 knots TAS at 75% power, 8,000 ft.
- Climb rate: 1,200 ft/min from 3,000 to 5,000 ft.
- Document the baseline in a detailed report, including test conditions, equipment used, and any deviations from the plan.
- Validate and Refine:
- Cross-check results with theoretical performance models (e.g., drag polar, engine power curves) or manufacturer data (if available).
- Conduct a second set of tests on a different day to confirm consistency.
- If results vary significantly, investigate sources of error (e.g., instrument calibration, pilot technique, or unaccounted wind).
- Use the Baseline for Comparisons:
- After modifications (e.g., aerodynamic fairings, engine upgrades), repeat the same test procedures under identical conditions.
- Compare new results to the baseline to quantify improvements (e.g., “Max speed increased by 5 knots after installing wingtip fairings”).
- Use statistical methods (e.g., t-tests) to confirm that changes are significant and not due to random variation.
Additional Tips:
- Safety First: Ensure all tests comply with FAA (or relevant authority) regulations for experimental aircraft. Use a qualified test pilot and conduct a thorough pre-flight inspection.
- Calibration: Verify instrument accuracy before testing. For example, perform a pitot-static system check or calibrate GPS units.
- Incremental Changes: When testing modifications, change one variable at a time (e.g., propeller pitch) to isolate its effect on speed.
- Real-Time Monitoring: If possible, use telemetry to monitor performance live and abort tests if parameters (e.g., engine temps) exceed safe limits.
By following this approach, you’ll create a robust, repeatable baseline that allows you to accurately measure speed improvements and make data-driven decisions for your experimental aircraft. If you have specific details about the aircraft (e.g., type, engine, or mods planned), I can tailor the advice further.
