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Safety Recommendation Details

Safety Recommendation A-97-043
Details
Synopsis: ON 3/4/94, A PIPER PA-38-112 TOMAHAWK, N2496L, CRASHED DURING A BIENNIAL FLIGHT REVIEW FOR A PRIVATE PILOT IN INMAN, KANSAS, THE FLIGHT REVIEW WAS BEING ADMINISTERED BY A CERTIFIED FLIGHT INSTRUCTOR (CFI) WHO HELD AIRPLANE SINGLE ENGINE, MULTIENGINE, AND INSTRUMENT RATINGS AND HAD 7,945 HOURS TOTAL FLIGHT TIME, INCLUDING 745 HOURS IN THE PA-38-112. THE PRIVATE PILOT'S LOGBOOK WAS DESTROYED IN THE ACCIDENT, BUT HE WAS BELIEVED TO HAVE HAD APPROXIMATELY 100 HOURS TOTAL FLIGHT TIME. WITNESSES REPORTED THAT THE AIRPLANE WAS IN A 5- OR 6-TURN LEFT SPIN AND THAT THE AIRPLANE SPUN UNTIL JUST BEFORE IT STRUCK THE GROUND. BOTH OCCUPANTS WERE KILLED, AND THE AIRPLANE WAS DESTROYED. POSTACCIDENT EXAMINATION REVEALED NO MECHANICAL PROBLEMS WITH THE AIRPLANE.
Recommendation: THE NTSB RECOMMENDS THE FOLLOWING TO THE FAA: (3) SECTION 23.207 STALL WARNING TESTS, TO ENSURE THE STALL WARNING HORN ACTIVATES AT LEAST 5 KNOTS BEFORE STALL.
Original recommendation transmittal letter: PDF
Overall Status: Closed - Acceptable Action
Mode: Aviation
Location: INMAN, KS, United States
Is Reiterated: No
Is Hazmat: No
Is NPRM: No
Accident #: CHI94FA097
Accident Reports:
Report #: None
Accident Date: 3/5/1994
Issue Date: 7/10/1997
Date Closed: 11/19/1998
Addressee(s) and Addressee Status: FAA (Closed - Acceptable Action)
Keyword(s):

Safety Recommendation History
From: NTSB
To: FAA
Date: 11/19/1998
Response: A-97-43 ASKED THE FAA TO EXPAND THE UPCOMING PA-38-112 CERTIFICATION FLIGHT TEST PROGRAM TO INCLUDE SECTION 23.207 STALL WARNING TESTS, TO ENSURE THE STALL WARNING HORN ACTIVATES AT LEAST 5 KNOTS BEFORE STALL. THEREFORE, A-97-42 AND A-97-43 ARE CLASSIFIED "CLOSED--ACCEPTABLE ACTION."

From: FAA
To: NTSB
Date: 3/31/1998
Response: (Letter Mail Controlled 4/6/98 4:05:05 PM MC# 980437) The FAA conducted wings level stall tests in accordance with 14 CFR 23.201, Amendment 23-14. The flight tests were conducted using the Piper PA-38-112, S/N 38- 78A0294, Registration Number N9246T. The airplane demonstrated satisfactory stall characteristics. For clarity, it should be noted that although Safety Recommendation A-97-42 states that a stall is defined by a "...downward pitching motion of the airplane," 14 CFR 23.201, Amendment 23-14, states that a stall is produced "...as shown by an uncontrollable downward pitching motion of the airplane {or} until the control reaches the stop." The stalls for the Piper PA-38-112 were accompanied by the classic downward pitching motion as detailed in The New Piper Aircraft, Inc., Report FT-192, Revision B, dated October 28, 1997, and the FAA Type Inspection Report SP2827AT-A, dated October 29, 1997. Stall warning tests were conducted satisfactorily in accordance with 14 CFR 23.207, Amendment 23-7. The Piper PA-38-112, S/N 38-78A0294, was also used for these tests. The FAA Type Inspection Report SP2827AT-A indicates that "...stall warning, in all conditions/configurations, occurred at least seven knots prior to the stall (FAR 23 minimum is five knots)." One issue that was raised with respect to the PA-38-112 was that the wings of production airplanes were not structurally the same as the certification airplane. Consequently, as part of this progam, a review was conducted of the latest production drawings. The comparison of the development engineering orders with the latest drawing release confirms that all changes required/approved during development and certification of Piper PA-38-112 wings were incorporated into the production wings. Therefore, the production wings are equal in strength and stiffness to the certification test wings, and this conformity was verified prior to tests. This fact is germane to the stall characteristics discussion. The Board's letter dated July 10, 1997, refers to reports of significant differences in the stall characteristics between the certification-tested airplane and the production airplanes during the 1979-1982 timeframe. The review of the Piper flight test reports does not confirm this statement by the Board or the testimony of the Piper engineer cited by the Board. In September 1983, the FAA issued Airworthiness Directive 83-14-08 for all PA-38-112 series airplanes which added a second set of stall strips to the airplane. Since that date, all PA-38-112 airplanes have the four stall strip configuration. The recent test airplane (Piper PA-38-112, S/N 38-78A0294) had the required four stall strip configuration. Both the FAA and Piper flight tested this condition. The FAA Type Inspection Report SP2827AT-A includes the results of deep stall investigation, stalls with sideslip (to include stalls without rudder use), and stalls with intermediate flap setting. The results are that "...deep stalls (yoke full aft) were investigated in all configurations (flaps up, flaps intermediate, and flaps full down) at full power and with the power at idle. The airplane was fully controllable in all axes during all tests. Stalls with sideslip (ball displaced 1/2 L and R) yielded a slow roll rate (approximately 5 degrees/second) in the direction away from sideslip (away from the ball) that was repeatable, easily recognized, and easily controllable. Stalls at the intermediate flap position behaved similar to the flaps down configuration, and no adverse handling qualities were noted." The New Piper Aircraft, Inc., Report FT-192, Revision B, states that "...lateral/directional characteristics at or near the stall are acceptable with no rapid, abrupt, or unpredictable loss of lateral control observed." The New Piper Aircraft, Inc., Report FT-192 further states that "...no unpredictable behavior was observed/encountered when flying at or near the stall." As part of the normal sequence, airspeed calibration, stall warning, and wings level stall tests were conducted prior to the turning flight and accelerated stalls. The Board made an attempt, prior to issuing Safety Recommendations A-97-41 through - 45, to determine if the FAA had flight tested the four stall strip configuration. At the time of the Board's inquiry, the FAA could not locate the report. However, the FAA has located the report (Type Inspection Report A4150EA-DO dated August 27, 1979). This report documented the results of stall and spin tests on a four stall strip configured Piper PA-38. The results were satisfactory. As an element for the justification of these safety recommendations, the Board cited statements of three former Piper employees who purport that the production airplanes were unpredictable in that the pilot never knew in what direction the aircraft would roll as a result of a stall. The FAA's discussions with Piper and a review of the production flight test records show that none of the employees cited by the Board were employed as production test pilots. Additionally, one of the individuals did not work at the Lockhaven facility during the years that the PA-38-112 was produced. The production flight test reports for all PA-38-112 airplanes do not indicate that a single aircraft failed to meet all type design specifications, including those tested with the two stall strip configuration. The Board further discussed stall/spin flight tests with the two and four stall strip configuration on two different airplanes conducted in Sweden. The stated purpose of the tests was to study the low speed, stalling, and spin characteristics of the airplane. One fact not referenced was that the right wing of each airplane was tufted for the study. Further, it was not established in the report that conformity inspections were conducted prior to the tests. The test results indicated that stalls did not produce the nosedown pitching expected, but they were characterized by a roll disturbance usually to the right without pitch change. In addition, the Swedish report stated that the airplane did not meet the stall warning requirement because stall warning occurred only two knots prior to the stall. It is feasible that the tufts could have affected the stalls, since they were installed on only one wing. As for insufficient stall warning, the aircraft tested by the FAA performed satisfactorily. There is a procedure for stall warning system adjustment available in the maintenance manual. It is important to note that the Swedish report concluded that "...spin characteristics are very good throughout. The aircraft is easy to bring into a spin and the spin is stationary after three turns. Exit is distinct and repeatable." Based on the above information, I consider the FAA's action addresses the full intent of these safety recommendations, and I plan no further action.

From: FAA
To: NTSB
Date: 9/25/1997
Response: The Federal Aviation Administration (FAA) agrees with the intent of these safety recommendations. A Piper PA-38-112 has been obtained for the flight tests. The aircraft is undergoing conformity tests, after which the flight test program will be conducted. It is anticipated that the program will be completed by the end of September. As part of the wings-level stall tests, the stall warning characteristics and horn activation will be evaluated. At the completion of the flight test program, the data will be available to address the issues outlined in these safety recommendations. I will keep the Board informed of the FAA's progress on these safety recommendations.