Investigating the Effects of Altitude and Flap Setting on the Specific Excess Power of a PA-28-161 Piper Warrior

Abstract

The high number of General Aviation (GA) accidents attributed to Loss of Control suggests that GA pilots are lacking low speed awareness and are unable to appropriately recognize when the aircraft is in a low energy state. There is, therefore, an urgent need for the development of an energy management system which is applicable to GA aircraft that can alert the pilot in situations of low energy conditions and recommends to the pilot the appropriate corrective action to restore conditions to a safe energy state. This will require the development of an algorithm that governs this energy management system that considers a comprehensive understanding of the performance capabilities of GA aircraft, particularly the ability of the aircraft to progress from one energy state to another. Given that low energy conditions are the primary concern, the aircraft’s ability to progress from a low energy state to a higher energy state, or the aircraft’s specific excess power (Ps), will be the parameter of most interest. The focus of this research study was the testing of a PA-28-161 Piper Warrior to develop an understanding of the effects of altitude and flap configuration on the ability of the aircraft to change its energy state. Level accelerations and level decelerations were performed and used to determine the Ps for the aircraft at various altitudes and configurations. The objectives of the test program were to generate Ps curves for each altitude and configuration, compare the curves obtained, and determine trends that could help model the Ps of the aircraft under any operating conditions. The results of the test program showed that there was an inverse relationship between specific excess power and altitude for both the clean-flap and full flaps configurations. The best climb speed for the aircraft was approximately 79 KIAS in the clean configuration and 62 KIAS in the full flaps configuration. Furthermore, extending the flaps resulted in a significant decrease in the maximum specific excess power of the aircraft, with the maximum specific excess power in the full flaps configuration being approximately 200 ft/min less than the maximum specific excess power in the clean configuration for all altitudes investigated. The best glide speed was observed to be 75 KIAS in the clean configuration. The data collected and trends observed will be valuable in the development of an algorithm for a GA energy management system. Further investigation into the Ps with the flaps deployed and comparison between the trends observed on the PA-28-161 with other common GA aircraft parameters will also be required.