Controlled Flight Into Terrain

8

Controlled Flight Into Terrain

Era Aviation

Sikorsky S-76A++, N579EH

Gulf of Mexico, About 70 Nautical Miles South-Southeast of

South-Southeast of

Scholes International Airport, Galveston, Texas

March 23, 2004

〔图〕插图

Aircraft Accident Report

NTSB/AAR-06/02

PB2006-910402

Notation 7646B

Aircraft Accident Report

Controlled Flight Into Terrain

Era Aviation

Sikorsky S-76A++, N579EH

Gulf of Mexico, About 70 Nautical Miles

South-Southeast of

Scholes International Airport, Galveston, Texas

March 23, 2004

〔图〕L3VgOARD\n NTSB/AAR-06/02

PB2006-910402

Notation 7646B

Adopted March 7, 2006

National Transportation Safety Board

490 L'Enfant Plaza, S.W.

Washington, D.C. 20594

References

Comparison of SPZ-7000 and SPZ-7600 Dual Digital Automatic Flight Control Systems

Comparison of SPZ-7000 and SPZ-7600 Dual Digital Automatic Flight Control Systems

References

Factual Information

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Aircraft Accident Report

1.2 Injuries to Persons

Table 1. Injury chart.

1.3 Damage to Aircraft

The helicopter was destroyed as a result of impact forces with the water.

1.4 Other Damage

No other damage was reported.

1.5 Personnel Information

1.5.1 The Captain

The captain, age 50, held an airline transport pilot certificate with a rotorcraft-helicopter rating. The captain also held a Federal Aviation Administration (FAA) first-class medical certificate dated May 12, 2003, with a limitation that required him to wear lenses to correct for distant vision and possess glasses to correct for near vision.

The captain served in the U.S. Army from July 1977 to August 1988, during which time he graduated from Army flight training and became an Army pilot (December 1980). From October 1988 to October 1999, the captain served in the U.S. Coast Guard as a pilot. The captain was hired by Era Aviation in November 1999.

According to company records, the captain had accumulated 7,288 hours total flying time, including 5,323 hours as pilot-in-command (PIC) of multiengine helicopters, 1,489 hours aboard S-76 helicopters, and 1,028 hours at night. Company records also showed that the captain had accumulated 3,913 hours total flying time in the Gulf of Mexico. Further, the captain had flown in the Gulf of Mexico 389, 64, and 32 hours in the

Factual Information

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Aircraft Accident Report

section 1.6.3.2.2); flight control computers, which provide all computations for autopilot and flight director operation; air data components,$^{26}$ which provide the flight control computers with information about the helicopter's airspeed, altitude above sea level, vertical speed, and radar altitude (that is, the helicopter's altitude above the surface);$^{27}$ and an autotrim system. Figure 1 is a preaccident photograph of the helicopter's cockpit that shows the location of DDAFCS components and indications.

〔图〕8109235。\n

1. Air data command display (AL-300)

1. Captain's electronic flight information system (EFIS) displays

1. Captain's digital automatic flight control system (DAFCS) caution panel and decouple (DCPL) indication

1. Captain's flight director mode selector

1. Autopilot controller

1. Copilot's flight director mode selector

1. Copilot's EFIS displays

1. Copilot's DAFCS caution panel and DCPL indication

1. Copilot's flight director indication

1. DAFCS indication

Figure 1. Location of DDAFCS Components and Indications in the Accident Helicopter's Cockpit

Source: Era Aviation.

Factual Information

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Aircraft Accident Report

1.6.3.2.1 Autopilots

Dual autopilot systems provide stability to the S-76 helicopter through a stability augmentation system (SAS) and an attitude retention mode (ATT). Both SAS and ATT modes provide heading hold,$^{28}$ yaw damping and autotrim, and automatic turn coordination. The SAS mode provides short-term rate damping during manual flight and is selected when extensive maneuvering is required; this mode is commonly used during the initial and final phases of flight and while hovering. The ATT mode provides pitch and roll attitude retention, through the autotrim system, during manual flight. Thus, after an in-flight disturbance, the helicopter will automatically return to the reference attitude. The ATT mode engages automatically when either autopilot is selected. Upon initial ATT mode engagement, the helicopter's reference attitude is its current attitude. The reference attitude can be reset by pressing a button on the cyclic.

Only one of the stability modes (SAS or ATT) can be engaged at a time. The autopilot controller is used to engage SAS or ATT and autopilots No. 1 and No. 2 (AP1 and AP2). (Autopilot coupling, which refers to automatic flight, is discussed in section 1.6.3.2.3.) When selected, the SAS button illuminates in amber, the ATT button illuminates in green, and the AP1 and AP2 buttons illuminate in green and indicate “ON.” Figure 2 shows the autopilot controller, which is located on the center pedestal (as shown by number 5 in figure 1).

〔图〕AP1FD 1/2AP2HOVONON2ON1SAS/ATTTESTCOLLCPL仑SASONONATTFD|RAD\n

Figure 2. Autopilot Controller

Note: The "FD1/2" button allows the pilot to select flight director 1 or 2 (as discussed in section 1.6.3.2.2). The "CPL" button automatically illuminates when the autopilot and the flight director are coupled (as discussed in section 1.6.3.2.3). The "HOV" button allows the pilot to select the hover mode. The "COLL" button allows the pilot to select either the flight director or the radar altimeter to provide collective commands. The "TEST" button allows the pilot to test the autopilots before they are engaged.

Source: Honeywell.

1.6.3.2.2 Flight Directors

The flight directors assist pilots in maintaining a specified flightpath or attitude through the presentation of command cues $^{29}$ on the attitude director indicators (ADI).$^{30}$

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Aircraft Accident Report

Flight director 1 is used when the left seat pilot is flying the helicopter, and flight director 2 is used when the right seat pilot is flying the helicopter. Flight director selection is made on the autopilot controller (see figure 2) with the FD1/2 button, which illuminates in white and indicates “1” or “2” depending on which flight director was selected. (Each press of the FD1/2 button alternates between flight directors 1 and 2.) When FD1 is selected, a “CPLT FD” light illuminates in green on the caution/advisory panel on the front instrument panel (see number 9 in figure 1). No light illuminates on the caution/advisory panel when FD2 is selected.

The command cues that are presented on the ADS generally correspond to the selected flight director modes, which include heading (HDG), vertical speed (VS), altitude (ALT), navigation (NAV), altitude preselect (ALT PRE), and standby (SBY). Figure 3 shows the flight director mode selector, which is located on the front instrument panel (as shown by numbers 4 and 6 in figure 1).

〔图〕HDGVSALT④ONONONNAV·DECELILS④ARMARMCAPARM|CAPGSONARMCAPARM|CAPVORAPRIAS-ALT PREARM|CAPONONSBY--GABC\n

Figure 3. Flight Director Mode Selector

Note: Other buttons on the flight director mode selector are ILS, instrument landing system mode; DECEL, deceleration mode; VOR APR, very high frequency omnidirectional range approach mode; IAS, indicated airspeed mode; BC, instrument landing system backcourse; and GA, go-around mode.

Source: Honeywell.

1.6.3.2.3 Coupling Function

For the SPZ-7000 DDAFCS, whenever a flight director mode is selected, FD1 or FD2 becomes automatically coupled to the autopilot as long as AP1, AP2, and the autopilot's ATT mode are engaged. Coupling allows the flight director's computed pitch and roll attitude corrections to be input to the autopilot so that the pilot does not have to manually control the helicopter according to the command cues on the ADIs. The CPL button on the autopilot controller (see figure 2) automatically illuminates in green and

Factual Information

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Aircraft Accident Report

in blue in the lower right corner $^{37}$ and the pilot-selected decision height $^{38}$ in blue in the lower left corner.$^{39}$ Figure 4 shows an electronic ADI and its various displays. The AIDs do not show which flight director has been selected or whether it has been coupled to the autopilot.

〔图〕RollFlight directorFlight directorRollattitudemode annunciationmode annunciationscalepointerPitch and rolHDGALTPcommand

Figure 4. Electronic Attitude Director Indicator

Source: Honeywell.

1.6.4 Maintenance Records

Maintenance records for the accident helicopter indicated that it was being maintained in accordance with an FAA-approved Continuous Airworthiness Maintenance Program. This program consists of regularly scheduled inspections, parts replacements, and tests and uses a computer database to track an aircraft's flight and maintenance activities. The database also tracks the requirements for inspections, overhauls, retirement of components, airworthiness directives, service bulletins, and survival equipment.

Factual Information

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Aircraft Accident Report

flight crew. As shown in figure 5, the following indications of descent were seen on the pilots' ADIs during the scenarios:

● The radar altitude appeared in blue at the bottom right of the ADIs followed by an “RA” indication in white.

● The decision height was displayed in blue at the bottom left of the ADIS followed by a DH indication in white. A white square box appeared above the radar altitude (at the bottom right of the ADIS) when the helicopter was 100 feet above the decision height (based on the radar altimeter). When the decision height was reached, an amber DH indication appeared inside the box and remained there as the helicopter continued to descend.

● A yellow rising runway symbol appeared at the bottom center of the ADIs at 180 feet (based on the radar altimeter). As the helicopter's altitude decreased, this symbol ascended until it met the aircraft symbol at 0 feet.

〔图〕0040100\n

Figure 5. Indications of Descent on the Attitude Direction Indicator

Other indications of descent seen on the pilots' instrumentation during the scenarios were the following:

● The barometric altimeters showed decreasing altitude by the counterclockwise rotation of the needle. ${}^{72}$

● The vertical speed indicators (VSI) showed a rate of descent of 250 to 300 fpm, which placed the needle below the centerline position.$^{73}$

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Aircraft Accident Report

In addition, for one scenario, an altitude of 900 feet was selected on the air data command display (the AL-300).$^{74}$ At an altitude of 600 feet (300 feet below the preselected altitude), an amber altitude alert light at the top left of the barometric altimeters illuminated,$^{75}$ and a 1-second aural tone sounded over the pilots' headsets. The light remained illuminated for the rest of this simulation.$^{76}$ Figure 6 shows the amber altitude alert light on one of the simulator's barometric altimeters.

〔图〕09C10172811450AL373003-450\n

Figure 6. Altitude Alert Light

Of the numerous possible scenarios that could lead to an inadvertent descent, the Safety Board focused on the four scenarios that were deemed to be the most likely to have occurred during the accident flight if the flight crew had engaged the DDAFCS. For detailed information about each of the four scenarios, see appendix C.

Factual Information

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Aircraft Accident Report

1.18.2 Gulf of Mexico Helicopter Operations

According to the latest statistics from the Helicopter Safety Advisory Conference (HSAC),$^{77}$ 561 oil industry helicopters (single engine, light twin, medium twin, and heavy twin) operated in the Gulf of Mexico during 2004, transporting more than 2.3 million passengers aboard 1.3 million flights. Table 2 shows the 2004 Gulf of Mexico oil industry helicopter accident rate and fatal accident rate per 100,000 flight hours compared with the same information for all U.S. air carrier operations under on-demand Part 135 (charter and air taxi).$^{78}$ (Even though the FAA's General Aviation and Air Taxi Survey$^{79}$ distinguishes between fixed-wing airplane and rotorcraft flight hours, the survey estimates of flight hours for rotorcraft do not reliably compare to HSAC's flight hour estimates for offshore helicopter operations. Thus, only the overall rates for on-demand Part 135 accidents are reported.) Table 3 shows this information for the 5-year period between 2000 and 2004. Appendix D provides a list of Gulf of Mexico helicopter accidents from March 2000 to February 2006.

Table 2. 2004 Accident Rates for Gulf of Mexico Helicopter Operations and On-Demand Part 135 Air Carrier Operations

Factual Information

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Aircraft Accident Report

Table 3. Accident Rates for Gulf of Mexico Helicopter Operations and On-Demand Part 135 Aircraft Operations for 2000 Through 2004

$^{a}$ The Gulf of Mexico accident rates were calculated using estimates of flight hours from the HSAC's Gulf of Mexico Offshore Helicopter Operations and Safety Review.

$^{b}$ Accident rate calculations for on-demand Part 135 operations (fixed-wing airplanes and rotorcraft) were estimated using data from the FAA's General Aviation and Air Taxi Survey.

Safety Board staff members visited two Gulf of Mexico helicopter operators—PHI of Lafayette, Louisiana, and Air Logistics of New Iberia, Louisiana—to compare and contrast their operations with Era Aviation's operations. Although each company's fleet consists of similar helicopter models, PHI and Air Logistics operate a larger fleet of helicopters than Era Aviation (more than 220 at PHI and more than 170 at Air Logistics compared with about 100 helicopters at Era Aviation). Also, PHI and Air Logistics operate both domestically and internationally, whereas Era Aviation operates domestically in Alaska, the West Coast, and the Gulf Coast. All three operators' helicopters fly at low altitudes while en route.

All three operators have dispatchers at their Gulf Coast headquarters (Era Aviation has 3 dispatchers, PHI has between 8 and 12 dispatchers, and Air Logistics has 2 dispatchers), but only Air Logistics has additional dispatchers at all of the locations where the company's helicopters are operating (one dispatcher per location). All three operators currently use flight-tracking software and hardware purchased from commercial vendors. $^{80}$ The software displays chevrons to indicate aircraft in flight and their direction along with weather overlays, and the hardware allows company pilots and dispatchers to relay text messages to each other. As with Era Aviation pilots, Air Logistics pilots call a company dispatcher to provide a position report every 15 minutes and to close out the flight plan; PHI pilots do not call a company dispatcher with position reports unless the

Factual Information

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Aircraft Accident Report

Both the SPZ-7000 and the SPZ-7600 have the capability to display pitch and roll command cues in either a dual- or a single-cue format. With the dual-cue format, pitch attitude is represented by a horizontal line, and roll attitude is represented by a vertical line, as shown in figure 7. With the single-cue format, angular bars integrate pitch and roll guidance, as shown in figure 8. When both pitch and roll commands are selected in either mode, the guidance provided by the command cues is intuitive and well understood by pilots who have been trained on either flight control system.

〔图〕C4M20201010101020200-\n

Figure 7. SPZ-7000 Dual-Cue Format

〔图〕oseywed20201010101020200\n

Figure 8. SPZ-7000 Single-Cue Format

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Aircraft Accident Report

Also, both the SPZ-7000 and the SPZ-7600 have the capability for the pilot to select a command cue for only one axis, either pitch or roll, at a time. The displayed cue for the selected axis is functionally the same as when command cues for both axes are selected. However, depending on the system and the command cue format, the command cue for the unselected axis may or may not be displayed. In addition, no annunciation appears on the ADIs regarding the source of guidance for the unselected command cue presented in the SPZ-7000 dual- and single-cue formats and the SPZ-7600 single-cue format.

Table 4 summarizes the command cues presented on the SPZ-7000 and SPZ-7600 DDAFCS and highlights the differences in attitude synchronization between the two systems. These differences, which are not intuitive, are analyzed in section 2.3.2.

Table 4. Command Cues Presented on the SPZ-7000 and SPZ-7600 DDAFCS With Single-Axis Command Selections

In addition, the indications for coupling and decoupling are distinctly different between the SPZ-7000 and SPZ-7600 DDAFCS. As stated in section 1.6.3, the SPZ-7000 does not annunciate the coupling status on the front instrument panel, and the SPZ-7000 DCPL warning indicator on the DAFCS caution panels illuminates only during abnormal operations. For the SPZ-7600, the DCPL warning indicator on each DAFCS caution panel illuminates during normal and abnormal operations whenever the autopilot and flight director become decoupled for an activated mode. Once the DCPL warning indicators are annunciated, annunciations can be cleared by either coupling the autopilot and flight director or resetting the couple logic by disengaging and reengaging one or both of the autopilots.

Finally, the SPZ-7600, as delivered from the manufacturer (Honeywell), is not equipped with an aural alert to indicate system decoupling under normal operations. Operators that use the SPZ-7600 can install an after-market product to provide this aural

Analysis

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〔图〕1283467\n

1. Landing gear warning light

1. Captain's ADI, showing radar altitude readout, rising runway symbol, decision height box, decision height indication, and command cues

1. Captain's barometric altimeter and altitude alert light

1. Captain's VSI

1. Landing gear warning light

1. Copilot's VSI

1. Copilot's ADI, showing radar altitude readout, rising runway symbol, decision height box, decision height indication, and command cues

1. Copilot's barometric altimeter

Figure 9. Indications of Descent in the Accident Helicopter's Cockpit

Source: Era Aviation.

Another indication, a rising runway symbol on the ADIs (numbers 2 and 7 in figure 9), did not require previous pilot action but would not have appeared until 180 feet above ground level (agl). The rising runway symbol would have continued upward until it met the aircraft symbol on the ADIs at 0 feet.

In addition to the indications of the helicopter's descent and proximity to the water that would have been present regardless of pilot action, several indications could have been present depending on the actions taken by the pilots during the accident flight. For example, if the flight crew had set a decision height above 0 feet (a decision height of

Appendix B

99

Time (CST)VOICE ID CONTENT OR COMMENT

1847:42 START OF RECORDING START OF TRANSCRIPT

[Conversational-tone voices audible and intermittent throughout the recording from 1847:42 through 1918:13, but unintelligible – except where transcribed.]

1848:18CO-PILOT * Lake Charles **

1848:46 CO-PILOT * Lake Charles five seven nine ***

1849:40 CO-PILOT *** five seven nine. there you are. we're off at ah four five High Island * five five seven... ***

1850:20 CO-PILOT Lake Charles ... ok four five High Island five five seven ***

1851:05 CO-PILOT give High Island five five seven a call and

1912:54 PILOT I dunno we have enough ...'bout another hour of (flight)/(flying) to do *

1914:00 CO-PILOT Lake Charles this is five seven nine ... five seven nine we (have) enough to ah fly to ah spirit ... ... seven three eight. five... * four five and ten... and one point ah six.

Appendix B

99

Time (CST)

VOICE ID

CONTENT OR COMMENT

1918:13 [unintelligible conversational tone voices not discernable at this point through the end of the recording]

1918:25 [sound of decreasing background noise]

1918:33.3 [sound of tone, 640 Hz frequency for 0.4 seconds duration, recorded on CVR audio channel 1]

1918:33.4 [sound of electronic static clicks, recorded on CVR audio channels 1 and 4 (CAM channel)]

1918:33.5 [sound of electronic static click, recorded on CVR audio channels 2 and 3]

1918:33.8 END OF TRANSCRIPT END OF RECORDING

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Appendix D Gulf of Mexico Helicopter Accident Data March 2000 Through February 2006

The following is a list of Gulf of Mexico helicopter accidents from 2000 to February 2006:

Appendix D

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