M3.1 Wing Charecteristics, Stalls, Groumd Effect

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Embry-Riddle Aeronautical University *

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ASCI 309

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Mechanical Engineering

Date

Dec 6, 2023

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docx

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- What phase of flight was the aircraft in when the incident/accident occurred? (Take-off, cruise, pattern, landing) - What attitude was the aircraft in when the incident/accident occurred? (Turn, straight and level, climb, descent, accelerating, decelerating) - What were the wings' aerodynamic characteristics, and how do they relate to the accident/incident? - What could have been done differently to prevent this accident/incident? - Include a reference so your classmates can read the article you are referring to. Utilize the Hunt Library! https://youtu.be/X1NOtAyZja0?si=Kh_eVdm0rWv6m1oo Hi all On April 24, 2021, a Cirrus SR22 stalled and crashed while attempting to land at Mustang Beach Airport, on the southern end of Texas (NTSB, 2022). Onlookers from the ground reported watching the aircraft come in low and slow, appearing to almost touch down short of the runway, when the pilot increased power in an attempt to go around. The aircraft’s nose pitched up sharply, the left wing dropped, and the nose impacted the ground killing one occupant and seriously injuring the other two. Footage from inside the aircraft showed the flaps fully retracted eight seconds before the crash. The National Transportation Safety Board (NTSB) determined that the aircraft did not have the correct flaps configuration for ago-around, adequate airspeed was not maintained, and the correct angle of attack was not held. What phase of flight was the aircraft in when the incident/accident occurred? The aircraft was on final approach, about to land. What attitude was the aircraft in when the incident/accident occurred? (Turn, straight and level, climb, descent, accelerating, decelerating) The Cirrus was in a wings-level attitude, although with low airspeed and a high Angle of Attack (AOA). What were the wings' aerodynamic characteristics, and how do they relate to the accident/incident?

The Cirrus SR 20 and SR22 airframes use a Roncz airfoil, designed by John Roncz. This particular type of airfoil is designated as a “low drag flying wing airfoil” and has similar characteristics to other piston aircraft common in-flight training (Airfoil Tools, 2023). However, although similar in size and objective to popular training aircraft such as the Cessna 172, this airfoil is not as forgiving with lower AOAs, and has a zero lift AOA of about -0.5, compared to the Cessna 172’s of -2.25. This essentially means that there better be a lot of power at a zero AOA to make up for lack of lift the wings generate – and this works, in cruise flight. At final approach, though, the aircraft comes in at a high AOA in order to generate more lift, and any reduction in wing camber (such as bringing the flaps up) will immediately bring the aircraft over its stall AOA. With a wing not designed to generate lift at 0, or sub-zero, AOAs, this is a definite recipe for disaster at low altitudes because this means the aircraft will spend more time in a nose- low angle attempting to start generating lift again. What could have been done differently to prevent this accident/incident? This seems like an incident stemming from a lack of situational awareness and/or training. Retracting flaps all at once on a go-around is a common student pilot mistake, but with a lack of situational awareness or training this can occur with licensed pilots as well. Additionally, from the onlooker’s description it seemed power increased dramatically and then reduced before the wing stalled. The pilot may have realized that all flaps were brought up and immediately pushed for max power on the throttle, however, the sudden increase in power may have brought the nose up sharply, adding to an already overly high AOA and bringing the aircraft to a stall. It is important to foresee the results of certain actions and implement reactions accordingly to avoid these kinds of situations. References Airfoil Tools. (2023). Roncz low drag flying wing airfoil (marske7-il). Airfoiltools.com. http://airfoiltools.com/airfoil/details?airfoil=marske7-il National Transportation Safety Board. (2022, July 20). Aviation investigation final report (Accident No. CEN21FA199). https://www.ntsb.gov/Pages/ResultsV2.aspx?queryId=234e57d4- 67d8-4409-8b37-fa8639ced871