NATIONAL TRANSPORTATION SAFETY BOARD Office of Research and Engineering Vehicle Performance Division (RE60) Washmgton, D.C

Transcription

1 NATIONAL TRANSPORTATION SAFETY BOARD Office of Research and Engineering Vehicle Performance Division (RE6) Washmgton, D.C. 4 Specialist s Report of Investigation by Daniel V. Venne, Mechanical Engineer A. ACCIDENT: Location: Wood Cross, Utah Date: February. Time: Aircraft: 4:OO Mountain Standard Time (MST) Bell GARLIK OH-A Registration: N7UT NTSB Control No.: DENOOGA5 B. INVESTIGATIVE GROUP: Not Applicable C. REFERENCES: NTSB Prelirmnary Factual Report Aviation ID No. DENOOGA5 dated // FAA m ort Surveillance Radar (ASR) data BT. RT. and RE3 dated // D. SUMMARY: At about 4:OO central mountain time (MST). :OO PM local. on February., a Bell GARLIK OH-A rotary wing aircraft, registration number N7UT. impacted terrain while on approach to Skypark PLlrport (BTF), Woods Cross. Utah. The commercial pilot and his mechanic passenger were both fatally injured as a result of the accident. The public use helicopter was being operated by the Utah Department of Public Safety under Title 4 CFR Part 9. Visual meteorological conditions prevailed for the maintenance test flight which originated approximately 5 minutes before the accident. No fight plan had been filed. According to mechanics at the shop where the helicopter had been worked on. N7UT was going to fight test the fiee wheeling unit s sprag clutch. The pilot intended to conduct the test by performing an autorotation. During the helicopter s approach to I DENOOGA5

2 runway 6. witnesses stated that the aircraft appeared to shake violently and the main rotor blades began flexing. One witness said that the tail rotor separated fiom the aircraft as N7UT approached the grown. The helicopter impacted terrain on its left side. Air Route Traffic System (ARTS) format radar data of the Approach Surveillance Radar (ASR)/Continuous Data Recorder (CDR) type. was obtained fiom the Federal Aviation Administration (FAA) for the approximate time of the accident. CDR data was provided fiom both the Salt Lake City. Utah Center (SLC) and the BTF Air Traffic Control Tower (ATCT). CDR radar data can provide primary (reflection of radar signal) and secondary (transponder) radar target information tracking data (predicted radar target position information), conflict alert information and other types of data in either an ARTS IIIA or common ARTS (ARTS IIIEBIE) data format. depending on the type of radar facllity reporting the radar data. ARTS IIIA and common ARTS IIIE format data are recorded on optical disk and common ARTS IIE format data is recorded on hard disk. The CDR data provided to NTSB for this accident was of the ARTS IIIA type and included beacon target (BT) reported (secondary) data, radar only target (RT) reported (p-) data, radar reinforced target (RB) reported (primary and secondary) data. and radar tracking (TD) data. Only the SLC data set containing the BT. RT and RB information was used for this study. The TD data set obtained from the BFT ATCT was not used since it provides predicted position information and is not as accurate as the BT. RT and RB data. The radar data used for this study provided radar information for the accident area between 3:5: and 4:5: local time (:5:J and :5: UTC), including minutes and 37 seconds. between 3:5:4 and 4:3:8 (:5:4 and :3:8 UTC) for the accident aircraft. Since the FAA radar data is recorded in UTC time, all times for the plots of radar data are shown in the matching FAA recorded UTC time. Local times (3 hour clock) with corresponding UTC times are used in the body (text) of this report. The radar data included secondary radar information (including time. altitude and position) for N7UT and several other aircraft in the general vicinity of the airport during this time period. Position lnformation for all three data sets included target range and azimuth fiom the ASR antenna. All secondary returns are correlated beacon (BT) returns. The BT radar targets for N7UT are correlated to the assigned transponder beacon code. No primary radar returns were found to be associated with N7UT in the RT and RB data sets. Therefore, only the BT radar data was used in this study. The BT data for N7UT was processed by computer, examined and plotted for study. Al radar data, data files and plots used for this study are provided as separate attachments to the enclosures. The ASR radar antenna site is the origin for all graphical plots of ground track. The ground impact site and the airport location are shown in the ground track displays. BTF indentifies the location for the Woods Cross. Skypark airport. E. DETAILS OF INVESTIGATION: I All FAA radar times are in Coordinated Universal Time (UTC) 7 DENOOGA5

3 3 Section I - Recorded Radar Data: The BT CDR radar data recorded at the SLC for this accident was recovered from computer storage by the FAA and provided to the NTSB on a 3 '/z inch computer floppy disk. The data was examined and processed to identlfy the aircraft's position and ground track for the time prior to ground impact. The transponder beacon code I provides the Mode C secondary information for N7UT. All radar information was recorded approximately every 4.6 seconds and provided target position and altitude for all secondary targets at resolutions of +/- /64 nm and +/- 5 feet, respectively. Attachment - to this report contains the BT data from the SLC for N7UT. Section - Pertinent Data Files: The reference position used for CDR radar data is the site location for the ASR antenna. The ASR antenna used to capture the BT radar data for N7UT is a class ARTS ASR 9 antenna. Since the latitude. longitude and elevation of the ASR antenna site is readily availabie. this information can be used to georeference the akcraft position information derived fiom the data. For this study, the ASR antenna site location of 4 degrees 48 minutes 38.3 seconds North lattitude, degrees minutes.9 seconds West longitude, and 435 feet antenna elevation ( 7 feet antenna height plus 4 8 feet ground elevation), was used as the basis (origin) to plot the radar target position information. The ground impact site is located at 4 degrees minutes 3.6 seconds North latitude and degrees minutes 34. seconds West longitude. The magnetic variation for the ASR antenna is 5. degrees East longitude. Processing of radar data for the accident aircraft included converting the rangeazimuth coordinates for the radar targets to distances east and north of the ASR antenna site, and preparing processed data for display by other programs. The Radar ViewPoinr' program was used to discern and display the ground track for the accident aircraft. The BT data was imported into Radar Viewpoint in order to identlfji, follow and plot the ground track for N7UT. The program's animation capability was used to follow the successive radar targets in time. Attachment - represents the BT radar data used to develop the ground track for N7UT in Radar ViewPoint. The Origin3 data analysis and technical graphics program was used to provide detailed plots of position, ground track, and altitude profile for the accident aircraft. Lastly, the mapping programs TOPO USA4 and Sfreets98j. were used to supplement the displays of ground track for N7UT. The position data for ground track are shown overlain on a topgraphic map from the TOPO USA program and a street map fiom the Streets98 program. Each display shows a plan view of the projection of the radar targets onto the Radar Viewpoint is owned and copyrighted by Airways Technology Corporation. Scottsdale. Arizona. Origin is owned and copyrighted by Microcal Software Incorporated. Northharnpton. Massachusetts. TOPO USA is owned and copyrighted by Delorme Incorporated. Yarmouth. Maine. Streets98 is owned and copyrighted by Microsoft Corporation, Seattle. Washington. 3 DENOOGA5

4 4 ground. The ground impact site. airport and other geographic features are also shown. These displays are discussed in more detail in Section below. Section I - Calculations & Graphical Plots of Radar Data: Summary of calculations: First. an altitude profile was constructed in order to view the vertical ascent and descent track for N7UT. Second. the radar target range-azimuth mformation was converted to latitude-longitude position information and to nautical mile distances in x (east-west) and y (north-south) horn the ASR antenna site. The NAD83 (WGS84) earth model was used for an ellipsoid earth aproximation in the radar coordinate conversion routine and the radar antenna position information was used to correct for slant range. Lastly, the data was smoothed (resampled in time) and a smoothed ground track and altitude profile were developed for N7UT prior to ground impact. Graphical plots for ground track and altitude profile are hrther described in the plotting sub-sections below. Radar ViewPoint plots: The original BT data was converted into a Universal Radar Format (URF) for processing by the Radar Viewpoint program. in order to identi@ and follow the radar targets in time on a scaled aeronautical chart. Animating by keyboard was used to discern N7UT fiom other aircraft and follow N7UT on its ground track. According to the BT radar data. N7UT was at feet altitude at 3:5:4 (:5:4 UTC). then varied between feet and 5 feet before dropping from radar coverage following the last radar return at 4:3: 8 ( :3: 8 UTC) at feet altitude. The reconstructed ground track created by Radar Viewpoint shows the target positions for N7UT up until 4:3: 8 (:3:8 UTC), which is the time of last radar target appearing in the BT radar data. Attachments - and - represent the BT radar targets and reconstructed ground track for N7UT on scaled aeronautical charts. Attachment - focuses on the ground impact site. The BTF airport location and the ground impact site. as well as several pertinent times and altitudes. are displayed. Origin plots: The radar data was also plotted using the Origin plotting and graphics program to support the findings for this report. Attachments -3 and -4 show plots of ground track and altitude profile. respectively. Time is the independent (x-axis) variable for the altitude plot and is displayed in both UTC time (hour:min:sec) for a standard 4 hour clock and in elapsed time (sec). Elapsed time. horn to 7 seconds. covers the minutes and 37 seconds offlight from 3:5:4 to 4:3:8 local time (:5:4 to :3:8 UTC). 4 DENOOGAO5

5 5 TOPO USA and Streets98 displays: Displays of the BT radar target positions and reconstructed ground tracks for N7UT are provided using digital maps developed from the TOP USA and Streets98 programs. Attachment -5 shows a topographic map generated with the TOPO USA program and attachment -6 shows a street map generated using the Streets98 program. Both maps display the BT radar targets for N7UT projected onto the ground. The BTF airport. ground impact site. and other geographic features are shown relative to the radar target positions and the projected ground track in each display. Notes & Observations: Based on the BT radar data. N7UT flew north f?om 3:5:4 (:5:4 UTC) at feet altitude. turned left heading south at 3::7 (7 UTC) and feet altitude, and dropped from radar coverage at 4:3:8 (:3:8 UTC) at feet altitude. The ground impact location is almost directly below the last recorded radar target position. 4- Dame V. Venne Mechanical Engineer Vehicle Performance Division (RE6) Enclosures: Art. I-: Att. -I: Aft. - through -6: FAA CDR format ASR Data Pertinent Computer Data Files Calculations & Graphical Plots of Radar Data DENOOGAOSO

6 Attachments I - FAA CDR format ASR Data

7 HOUR MIN SEC I ALT RANGE ACP

8

9

10 Attachments I - Pertinent Computer Data Files

11 5:4.8 N4-5-7 W-- 5:46.45 N4-5-3 W--5 5:5.8 N W--44 5:.83 N W--38 :.47 N W--33 : 5. N4-5-5 W--9 : 9. N4-5- W--6 :4.9 N4-- 3 W--3 :8.77 N4-- 9 W--3 :3.4 N4--6 W-- :7.89 N4--3 W--9 :3. N4--3 W-- :37. N4--38 W-- :4.76 N4--44 W-- :46.39 N4--5 W-- :5.96 N4-- W-- :.6 N4-- W-- :.9 N4-- W--3 : 4.8 N4--6 W-- : 9.46 N4--4 W-- :4.9 N4--9 W--4 :8.67 N4--35 W--4 :3.3 N4--4 W--3 :7.9 N4--49 W-- :3. N4-- W-- :37.8 N4-- W-- :4.75 N4-- 8 W-- :46.38 N4--5 W-- :5. N4-- W--3 :.49 N4--3 W-- :.4 N4--37 W-- : 4.7 N4--44 W-- : 9.36 N4--49 W-- ~3.99 N4-- W-- ~8.6 N4-- W-- :3. N4-- W-- :7.85 N4--7 W--9 :3.43 N4--3 W-- :37. N4--3 W--7 :4.67 N4--39 W-- :46.3 N4--45 W--9 :5.93 N4--5 W-- :. N4-- W-- :.5 N4-- 3 W--9 : 4.79 N4-- 9 W--3 : 9. N4--3 W-- :4.7 N4--9 W-- :8.63 N4--4 W--9 :3.6 N4--9 W-- :8.3 N4--34 W--8 :3.6 N4--4 W--8 :37.4 N4--47 W--8 :4.75 N4-- W--9 :46.33 N4-- W--7 :5.96 N4-- 4 W--5 :. N4-- W--8 :. N4--9 W--8 : 4.8 N4--5 W--8 : 9.43 N4--3 Wlll--8 :4.6 N4--39 W--8 :8.69 N4--46 W--9 :3.7 N4-- Wlll--9 :7.87 N4-- W--8 :3.5 N4-- 3 W--8 :37. N4-- 9 W C

12 :4.74 N4--4 W--9 :46.33 N4--8 W--3 :5.8 N4-- W-- :. N4--7 W--9 :. N4--3 W--3 : 4.79 N4--35 W--9 : 9.4 N4--39 W--3 :4.5 N4--43 W--34 :8.69 N4--48 W--36 :3.8 N4--5 W--39 :7.76 N4-- W--44 :3. N4--49 W--48 :37.6 N4--43 W--46 :4.75 N4--39 W--45 :46.4 N4--34 W--45 :5.99 N4--8 W--39 :.63 N4--3 W--35 :. N4--7 W--3 : 4.87 N4-- W--9 : 9.45 N4-- 5 W--6 :4. N4-- W-- :8.69 N4--5 WI.-- :3.3 N4--4 W-- :7.95 N4--36 W--4 :3. N4--3 W--4 :37.7 N4--3 Wlll--4 :4.8 N4--5 W--5 :46.4 N4-- 8 W-- :5.4 N4-- W--3 :.66 N4-- W--4 :.9 N4--48 W--3 : 5. N4--4 Wl-- : 9. N4--35 W--6 :4. N4--8 W--5 :8.75 N4-- W--5 :3.5 N4--5 W--3 :7.95 N4-- 7 W--5 :3. N4-- W--5 :37.8 N4-- W--5 :4.83 N4--45 W--6 :46. N4--39 W--4 :5.6 N4--33 W--7 :.7 N4--6 W--6 :.8 N4--7 W--5 : 4.9 N4-- W--5 : 9. N4-- 4 W--4 :4.3 N4-- W--3 :8.75 N4--5 W--6 :3.38 N4--4 W--3 :8. N4--37 W--6 :3.6 N4--3 W--6 :37.5 N4--4 W--5 :4. N4--6 W--9 :46. N4-- W--8 :5.4 N4-- 4 W--8 :.83 N4--6 W--3 :.47 N4-- W--37 : 5.9 N4--5 W--4 : 9. N4--47 W--47 :4. N4--43 W-- :8.78 N4--4 W-- ~3.43 N4--4 Wlll-- 4 :8. N4--37 W--i3 ~3.66 N4--35 Wlll--E :37.6 N4--34 W--7 48q 48C

13 :4.84 N4--33 W--35 :46.49 N4--3 W--39 :5.3 N4--3 W--48 :.73 N4--33 W-- :.3 N4--3 Wlll-- 3 : 9.6 N4--9 W--5 :4. N4--7 W-- :8.83 N4--5 W--5 :3.43 N4--9 W--9 :8.6 N4--5 W--35 :3.69 N4-- W--37 :37.7 N4-- 8 W--37 :4.9 N4-- 4 W--38 ~46.5 N4--6 W--36 :5.4 N4-- W--38 :.73 N4-- W--38 3:.37 N4--49 W--37 3: 5. N4--44 W--38 3: 9.63 N4--4 W--38 3:4. N4--35 W--36 3:8.97 N4--3 W--3

14 Attachments - Calculations & Graphical Plots of Radar Data

15 ::7 ft.: I - /..,- F. ** r r I- :3:8 ft Q.7.i BTF 6 63 :5:4 ft

16 I 48 3 *TO5 u :37!-')' 5 :46 /-!5 \J :5 -~:5 -.'/9 j49 3:4 43l5 3: 8 Impact N4-.6 W..63 BTF DENOOGA5 :4.897 (.nrn per inch) Radar ViebvPoint(tm) by Airnays Technoloa. lnc

17 . m

18 P -4 P 3 P i i l C 3 vi i Crl N (nn ::3 L C> (3 ----"e ::oob-"/-.--- :: ::8.-- -e==---* ::4 ::3--3-= ,I :3:O9-4 :3: (3 (3

19

20 DE NOOGA5 Wi N 3 M \AI 4 i\l \N 4 S Cn E I- Vi/ i 5CO S N7UTL , - 9 -_ 3 8 5OOOt MSL,- VI L Streets98