Date of Award
Master of Science (MS)
Aerospace, Physics, and Space Sciences
The purpose of this thesis is to discuss the performance, modification, and recertification of the test aircraft, a Cessna 172N that has been equipped with an O-360-A4M power plant, tuned exhaust, and variable timing electronic ignition, and to compare the aircraft to a stock aircraft and other high-performance aircraft to determine the feasibility of the modifications. 65 knot, 80 knot, and 95 knot steady state climb and 2000 ft and 5000 ft level acceleration tests were performed with the test aircraft at the Melbourne Orlando International Airport. The weather was clear with calm wind, and there was only one issue of excessive cooling when attempting idle descents during testing. The aircraft was forward loaded with 150 lbs of ballast. Time stamps, ambient temperature, and engine speed were recorded manually, and all other values, including indicated airspeed and altitude, were recorded using onboard equipment. The data was reduced, finding important values including calibrated airspeed (Vc), instrument and weight corrected power and rate of climb (PIW and CIW), rate of climb (ROC), and specific excess power (Ps). Standardized performance charts, such as PIW vs CIW and VC vs Time, and expanded charts, such as ROC vs VC and ROC on a Standard Day at Various Altitudes, were generated. The modified Skyhawk was compared to an unmodified stock aircraft, a Diamond DA40, a Mooney M20C, and a Grumman American AA5B Tiger using Ps vs Vc charts from a thesis by a former student, Yohan Forbes Auguste, cruise performance charts for pilot’s operating handbooks (POHs), and aircraft resale marketplaces. The analysis showed that the modified Skyhawk, with a best rate of climb (ROC) of 720 ft/min at 3000 ft, has superior climb performance to that of the Stock Cessna 172N, at 400 ft/min, and comparable performance to that of the DA40, M20C, and AA5B Tiger at 700-760 ft/min. The market
value for the modified Skyhawk, at $100-$175, is roughly equivalent to that of the unmodified Skyhawk. With variable timing and electronic magneto technology, the modified Skyhawk has a fuel consumption and fuel cost of 10.3 gph and $68.40/hr that is equivalent or better than that of the other high-performance aircraft at 9.2-15.1 gph and $61.10/hr-$95.60/hr. The cost of the modifications is affordable, $30k-$31k, and the average cost of an existing modified Skyhawk, $139k, is between the average costs of the other high-performance aircraft at $81k-$347k. After considering all factors, the recommendation to pilots is to upgrade a stock Skyhawk rather than purchase a newer, high-performance aircraft. If a pilot cannot afford every upgrade, it is recommended that the electronic ignition variable timing installation be done first because, in addition to providing fuel savings, it is the most cost-friendly, and potentially decreases maintenance costs. Recertification requires at least one supplemental type certificate (STC), and companies, such as Air Plains, Electroair, and Power Flow Systems provide kits for engine, variable timing electronic ignition, and tuned exhaust and approved STCs and support. It is recommended that pilots consider the inability to perform idle descents, upfront cost, higher future fuel costs over stock, and time to modify and recertify when considering the upgrades, and hire a lawyer, flight test engineer, and/or test pilot and contact the FAA early to facilitate recertification. Replacing other high-performance aircraft in the industry with 180 Hp Skyhawks with variable timing electronic ignition would not only help owners but would also increase sustainability of the aviation community by increasing flight safety, reducing fuel consumption, reducing operating costs, and providing a good, gradual solution to the energy crisis while other electronic and hybrid technologies are explored.
Kaht, Kelsey Lee, "Analysis of the Performance, Recertification, and Sustainability of a Cessna 172N Modified with an O-360-A4M Powerplant, Variable Timing Electronic Ignition, and Tuned Exhaust" (2023). Theses and Dissertations. 1311.