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craig(at)craigandjean.com
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 Posted: Sat Mar 01, 2008 10:21 pm Post subject: Not your usual accident report |
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But fascinating reading. I would love to hear Brandon Tucker's feedback
since he flies one of these things:
http://www.ntsb.gov/ntsb/brief.asp?ev_id 060509X00531&key=1
NTSB Identification: CHI06MA121.
The docket is stored in the Docket Management System (DMS). Please contact
Records Management Division
14 CFR Public Use
Accident occurred Tuesday, April 25, 2006 in Nogales, AZ
Probable Cause Approval Date: 10/31/2007
Aircraft: General Atomics Predator B, registration: None
Injuries: 1 Uninjured.
The unmanned aircraft (UA), a Predator B, collided with the terrain
following a loss of engine power while patrolling the southern U.S. border
on a Customs and Border Protection (CPB) mission.
The UA's takeoff was delayed due to the inability to establish a
communication link between the UA and Pilot Payload Operator (PPO)-1 console
during initial power-up. After troubleshooting the problem, an avionics
technician switched the main processor cards between PPO-1 and PPO-2.
Personnel who were maintaining the unmanned aircraft system (UAS) stated
there were very few spare parts purchased with the UAS, which is why they
switched the main processor cards instead of replacing the card in PPO-1.
The link was subsequently established, and the flight was initiated.
The flight was being flown from a ground control station (GCS), which
contained two nearly identical control consoles: PPO-1 and PPO-2. Normally,
a certified pilot controls the UA from PPO-1, and the camera payload
operator (typically a U.S. Border Patrol agent) controls the camera, which
is mounted on the UA, from PPO-2. Although the aircraft control levers
(flaps, condition lever, throttle, and speed lever) on PPO-1 and PPO-2
appear identical, they may have different functions depending on which
console controls the UA. When PPO-1 controls the UA, movement the condition
lever to the forward position opens the fuel valve to the engine; movement
to the middle position closes the fuel valve to the engine, which shuts down
the engine; and movement to the aft position causes the propeller to
feather. When the UA is controlled by PPO-1, the condition lever at the
PPO-2 console controls the camera's iris setting. Moving the lever forward
increases the iris opening, moving the lever to the middle position locks
the camera's iris setting, and moving the lever aft decreases the opening.
Typically, the lever is set in the middle position.
Console lockup checklist procedures indicate that, before switching
operational control between the two consoles, the pilot must match the
control positions on PPO?2 to those on PPO-1 by moving the PPO-2 condition
lever from the middle position to the forward position, which keeps the
engine operating. The pilot stated in a postaccident interview that, during
the flight, PPO-1 locked up, so he switched control of the UA to PPO-2. In
doing so, he did not use the checklist and failed to match the position of
the controls on PPO-2 to how they were set on PPO-1. This resulted in the
condition lever being in the fuel cutoff position when the switch to PPO-2
was made, and the fuel supply to the engine was shut off.
With no engine power, the UA began to descend. The pilot realized that the
UA was not maintaining altitude but did not immediately identify that the
condition lever was in the fuel cutoff position. The pilot and avionics
technician decided to shut down the entire system and send the UA into its
lost-link profile, which is a predetermined autonomous flightpath, until
they could figure out what the problem was. After the system was shut down,
the UA descended below line of sight (LOS), and communications could not be
reestablished. The UA began to fly its lost-link profile as it descended to
impact with the terrain.
When the UA lost engine power, it began to operate on battery power. On
battery power, the UA began to shed electrical equipment to conserve
electrical power. In doing so, electrical power to the transponder was shut
down. This resulted in air traffic control not being able to detect a Mode C
transponder return for the UA as it descended below the bottom of the
temporary flight restricted airspace. The primary radar return was also lost
when the UA descended below the LOS in the mountainous area.
The investigation revealed a series of computer lockups had occurred since
the CBP UAS began operating. Nine lockups occurred in a 3-month period
before the accident, including 2 on the day of the accident before takeoff
and another on April 19, 2006, 6 days before the accident. Troubleshooting
before and after the accident did not determine the cause of the lockups.
Neither the CBP nor its contractors had a documented maintenance program
that ensured that maintenance tasks were performed correctly and that
comprehensive root-cause analyses and corrective action procedures were
required when failures, such as console lockups, occurred repeatedly.
Review of the CBP's training records showed that the accident pilot had
recently transitioned from flying the Predator A to flying the Predator B
and had only 27 hours of Predator B flight time. According to the CBP, the
pilot was given verbal approval to fly its Predator B with the caveat that
the pilot's instructor would be present in the GCS when the pilot was
flying. This verbal approval was not standard practice for the CBP. The
instructor pilot was in another building on the airport and did not enter
the GCS until after it was shut down and the UA entered the lost-link
procedure.
The investigation also revealed that the CBP was providing a minimal amount
of operational oversight for the UAS program at the time of the accident.
The National Transportation Safety Board determines the probable cause(s) of
this accident as follows:
The pilot's failure to use checklist procedures when switching operational
control from PPO-1 to PPO-2, which resulted in the fuel valve inadvertently
being shut off and the subsequent total loss of engine power, and lack of a
flight instructor in the GCS, as required by the CBP's approval to allow the
pilot to fly the Predator B. Factors associated with the accident were
repeated and unresolved console lockups, inadequate maintenance procedures
performed by the manufacturer, and the operator's inadequate surveillance of
the UAS program.
-- Craig
Do not archive
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bryanmmartin
Joined: 10 Jan 2006
Posts: 1018
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| Posted: Sun Mar 02, 2008 7:55 am Post subject: Not your usual accident report |
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For the amount of money this program costs, you'd think they'd have
put a little more thought in the design of the operator consoles. The
same lever operates a fuel control valve in one instance and a camera
lens in another? They didn't think to use dedicated controls for
critical flight functions?
On Mar 2, 2008, at 1:18 AM, Craig Payne wrote:
| Quote: |
>
But fascinating reading. I would love to hear Brandon Tucker's
feedback
since he flies one of these things:
http://www.ntsb.gov/ntsb/brief.asp?ev_id 060509X00531&key=1
NTSB Identification: CHI06MA121.
The docket is stored in the Docket Management System (DMS). Please
contact
Records Management Division
14 CFR Public Use
Accident occurred Tuesday, April 25, 2006 in Nogales, AZ
Probable Cause Approval Date: 10/31/2007
Aircraft: General Atomics Predator B, registration: None
Injuries: 1 Uninjured.
|
--
Bryan Martin
N61BM, CH 601 XL,
RAM Subaru, Stratus redrive.
do not archive.
| | - The Matronics Zenith-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Zenith-List |
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_________________
--
Bryan Martin
N61BM, CH 601 XL, Stratus Subaru.
do not archive. |
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