1、Lessons Learned Entry: 1714Lesson Info:a71 Lesson Number: 1714a71 Lesson Date: 2003-07-4a71 Submitting Organization: LARCa71 Submitted by: Leslie Johnsona71 POC Name: DanielYuchnovicza71 POC Email: Daniel.E.Yuchnovicznasa.gova71 POC Phone: 757-864-7272Subject: Uninhabited Aerial Vehicle (UAV), Fligh
2、t Test Operations, Accident Investigation Abstract: A high performance jet-powered UAV crashed on landing. A subsequent investigation into the root cause(s) found that the ground support crew did not follow all of the steps in a complex checklist and the pilot did not adhere to the flight parameters
3、 dictated by the flight test card. Omission of pre-flight steps resulted in lower than expected engine thrust performance. This off-nominal thrust condition caused the pilot to attempt to compensate throughout the flight. This compensation, along with other complicating factors, caused the pilot to
4、mismanage the UAVs energy, resulting in a landing touchdown speed that was well above rated touchdown speeds, resulting in the collapse of the left main landing gear. The pilot did not have any previous experience with this UAV. A primary complicating factor was that the pilot did not know and was n
5、ot briefed on several key UAV performance factors, primary of which was maximum touchdown speed. Less than adequate communications between the pilot and ground support crew both in preflight and flight was also a complicating factor. During the crash, the flight crew was exposed to potential injury
6、since they were situated at the runway edge near the UAV touchdown point. Execution of each step in a checklist should be independently verified, especially the complex checklists used in these operations. A pilot briefing on critical vehicle performance parameters should be given even if the pilot
7、is expected to know critical flight parameters. Communications between pilot and ground support crew should be full and open during preflight and flight. Real time warnings should be provided to the pilot when deviating from the planned flight test parameters. The flight crew should maintain a safet
8、y barrier device between themselves and the vehicle during the landing sequence.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Description of Driving Event: A UAV was landed at a speed well above the design speed for the landing gear. The left main
9、gear collapsed and the UAV veered off of the left edge of the runway while tumbling and shedding parts of the airframe, resulting in extensive damage to the vehicle. The pilot experienced time pressure to land the UAV as he though it was about to run out of fuel (typically resulting in a crash in th
10、is type of UAV). The UAV actually had triple the flight time that the pilot thought was available. The pilot was unable to adequately manage the UAVs energy throughout the entire flight and ultimately landed at 35 knots above the design speed for the gear, resulting in landing gear failure. The pilo
11、t did not know and was not briefed on the design speed limit for the landing gear. The flight crew, standing unprotected at the runway edge, could have been injured if the UAV had landed sooner and the right main gear had collapsed.Lesson(s) Learned: 1. It was clear that the UAV pilot did not know s
12、everal key flight critical parameters that a pilot should know in order to execute a flight test. Chief among them were maximum landing speed and maximum flight time at cruise power. 2. The ground support crew used a complex preflight checklist and skipped a key step that reduced the thrust time rat
13、e-of-change to be less than expected by the pilot, resulting in a longer take off roll, and a re-contact with the runway during departure. 3. Steps in checklists maybe missed if the checklist is overly complex. There was no independent or second check that each step in the preflight checklist was ex
14、ecuted. 4. The preflight checklist did not include a briefing of flight critical parameters to the pilot. The pilot was new to this UAV. 5. The pilots lack of knowledge in a key area of engine thrust trim contributed to the pilots perception of off nominal thrust performance during the flight. 6. Th
15、e flight crew did not give the pilot real time warnings when flight critical parameters were being exceeded due to the erroneous assumption that the pilot was familiar with the parameters. 7. UAV pilots cannot be expected to make the best decisions when operating with incomplete or erroneous knowled
16、ge of critical flight parameters. 8. Flight crews tend to dislike protective barriers between themselves and the UAV, thinking that they can quickly move out of the path of an oncoming UAV during a loss of control incident.Recommendation(s): Provided by IHSNot for ResaleNo reproduction or networking
17、 permitted without license from IHS-,-,-1. Complex checklists should be simplified for daily operations to the maximum extent possible and a second, independent check should be made to verify that each step is completed before moving on to the next. 2. A pilot briefing just prior to the flight shoul
18、d be conducted covering all flight parameters critical to the flight test. The flight test program should provide the pilot with a UAV performance handbook covering the vehicle performance parameters. 3. The flight crew should practice the actual flight test procedures with a low-cost radio controll
19、ed model to dry run the procedures and facilitate critical communications between the flight crew during flight, e.g., do not land and go around if the airspeed exceeds a target value. 4. The pilot should be allowed some time on the first flights to perform handling qualities maneuvers at altitudes
20、that support safe recovery from low airspeed maneuvers such as slow flight, stalls and landing configurations. 5. Safety barriers should be used to protect the flight crew during the landing phase.Evidence of Recurrence Control Effectiveness: N/ADocuments Related to Lesson: N/AMission Directorate(s)
21、: a71 Space Operationsa71 Aeronautics ResearchAdditional Key Phrase(s): a71 Missions and Systems Requirements Definition.Crew operations and support conceptsa71 Mission Operations and Ground Support Systems.a71 Safety and Mission Assurance.a71 Additional Categories.Additional Info: a71 Project: UAVProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Approval Info: a71 Approval Date: 2006-15a71 Approval Name: dkruhma71 Approval Organization: HQProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
