Departing Boeing 777 Came Within 500 Feet Laterally From Cessna
182
The NTSB has released factual findings in an incident which
occurred in March, 2010, in which a wide-body airliner came within
500 feet of colliding with a Cessna 182.
According to the report, on March 27, 2010, at 1112 PDT, an
operational error occurred at the San Francisco Airport Traffic
Control Tower (SFO ATCT) when United Airlines flight 889 (UAL889),
a Boeing 777 en route from San Francisco, California to Beijing,
China, and N9870E, a Cessna 182 transiting the SFO class B surface
area southbound toward Palo Alto, California, passed within
approximately 480 feet laterally and 300 feet vertically of each
other over San Bruno, California. Both aircraft were under control
of SFO ATCT at the time of the incident. The crew of UAL889 filed a
near-midair collision report and a Traffic Alert and Collision
Avoidance System (TCAS) report following the incident. There was no
damage reported to either aircraft, and no injuries to passengers
or crew.
According to a company report filed by the crew of UAL889, the
SFO local controller cleared the flight for takeoff from runway 28L
on the MOLEN 3 departure with clearance to climb to 3,000 mean sea
level (msl). The flying First Officer reported after the landing
gear was retracted at approximately the runway end, and at 1,100
msl, he heard the tower controller report traffic at 1 o'clock.
This was followed immediately by the TCAS "TRAFFIC TRAFFIC"
warning. According to the TCAS, the target was at 1,400 msl. The
pilots visually acquired a light high wing airplane in a hard left
turn at their 1 o'clock position. Both crew members reported seeing
only the underside of the airplane. Distance to the airplane
described as slant range was 200-300 feet. The First Officer's
response was to push forward on the yoke to level the airplane. The
other airplane disappeared from view through the 3 o'clock
position. The First Officer then looked back into the cockpit at
which time TCAS annunciated "ADJUST VERTICAL SPEED", followed by a
"DESCEND, DESCEND" command. The First Officer stated he complied
with a push over to comply. The climb on MOLEN 3 was then
continued.
File Photo
N9870E was operating from the area of the city of San Francisco
southbound along US 101, a freeway that passes just west of SFO.
The pilot contacted the SFO local controller at 1809:34, reporting
level at 1,600 feet. The controller instructed the pilot to,
"...keep highway 101 off your left side," and the pilot
acknowledged. The route the pilot was following is a commonly used
transition through the SFO class B surface area.
UAL889 was a scheduled 14 Code of Federal Regulations part 121
passenger flight operating from San Francisco, California, to
Beijing, China. The pilot was instructed to taxi to runway 28L for
departure. At 1810:10, the local controller cleared UAL889 into
position and hold on the runway. At 1811:47, UAL889 was cleared for
takeoff.
At 1812:50, the local controller transmitted, "70 echo traffic
off the departure end climbing out of 500 heavy triple 7." The
pilot of N9870E responded, "70E in sight." The controller then
continued, "70E maintain visual separation pass behind that
aircraft." The pilot responded, "70E pass behind 'em." At 1813:03,
the controller transmitted, "United 889 heavy traffic's uh just
ahead and to your right has you in sight Cessna 1,500 they're
maintaining visual separation." At 1813:13, the controller
continued, "United 889 heavy traffic's no factor contact Norcal
departure." The pilot of UAL889 responded, "OK, that set off the
TCAS...that was...that...we need to talk."
At 1813:47, UAL889 transmitted, "All right, trip...889's going
to uh departure," and the controller acknowledged.
At 1815:23, the pilot of UAL889 recontacted SFO tower to request
a discrete frequency to contact the tower on. The controller
instructed the pilot to contact the tower on 128.65, and the pilot
acknowledged.
At 1817:59, the controller-in-charge spoke with UAL889 on
128.65, advising the pilot, "...that was a VFR transition, and uh
he was ahead and to your right, he had you in sight, he had visual,
and he was instructed to pass behind you." The pilot responded,
"Well, his uh flight path was definitely gonna be uh converging
with ours and uh there was uh less than uh 500 feet separation
between the aircraft if you could uh pull the tapes and uh pull any
you know uh radar sweeps we'd appreciate it." The controller
replied, "...understand – he did have visual with you. We'll
uh we'll do that though, you can uh get that number from your ops
if you want to call." The pilot requested the number, and the
controller again stated that they would need to get the number from
UAL operations. The pilot acknowledged and the contact
concluded.
The CIC logged the incident as a quality assurance review item
in the Daily Record of Facility Operations. He also advised the
front-line manager, who was out of the cab working on documentation
of two previous incidents, of the United pilot's complaint.
While still in flight, the captain of UAL889 recontacted the
tower through UAL operations to discuss the incident further. The
captain stated that she was very upset over the incident because of
the close proximity of the Cessna, the lack of warning from the
tower, and the TCAS alert indicating that the two aircraft were
separated by only 200 feet vertically and horizontally. She
questioned the tower's procedures and the separation standards
applicable to the encounter, and stated that she would be filing
paperwork on the incident.
File Photo
SFO ATCT did not initially file an operational error report on
the incident. After review by service area and FAA headquarters
management, the facility was directed to file an operational error
report based on non-compliance with paragraph 7-2-1 of FAA Order
7110.65, and did so on April 5, 2010.
Radar data for this report was obtained from the ASR-9 sensor
located at Oakland, California, about 8 miles northeast of SFO. Two
graphics showing an overview of the paths of the two aircraft and a
close view of their minimum separation, have been entered in the
docket. The applicable separation standard between VFR and IFR
aircraft in class B airspace is either 1.5 miles laterally or 500
feet vertically. At closest point of approach, the aircraft were
separated by about 480 feet laterally and 350 feet vertically,
resulting in a minimum slant range distance between UAL889 and
N9870E of about 600 feet.
The local controller was assigned to SFO ATCT in 1999 and was
qualified on all control positions in the tower.
Asked about any unusual circumstances on the day of the
incident, the local controller noted that he had been
controller-in-charge earlier that morning when another controller
had an operational error. Reporting of that incident and the
associated paperwork required the attention of the front-line
manager (supervisor) on duty and resulted in the supervisor being
occupied with administrative duties outside the tower cab for
almost the whole shift. That effectively reduced available staffing
because the controllers then had to fill the CIC position as well
as the control positions.
Just before the incident, the radar coordinator asked the local
controller if she should accept a handoff from Northern California
TRACON on Cessna N9870E. As UAL889 was the only runway 28 departure
pending, he told her to take the handoff. The Cessna reported over
Hunter's Point (north of the airport), and the local controller
instructed the pilot to keep highway 101 off of his left side as he
proceeded southbound. The ground control position then began
verbally coordinating with the radar coordinator regarding an
aircraft that would be taxiing around the west end of runways 28L/R
"after the guy on the runway." (UAL889) Ground control then amended
the request to cross two aircraft instead of one. The local
controller looked at the west end taxiway to check on the positions
of the crossing aircraft and then cleared UAL889 for takeoff. He
then looked back at taxiway Z to make sure that the taxiing
aircraft were holding short of the runways while UAL889 departed.
The local controller then looked at the radar display and realized
there was a conflict between N9870E and UAL889. He pointed out the
departing United aircraft as traffic to the Cessna pilot and
instructed him to pass behind it.
When interviewed, the local controller stated that after he
recognized the conflict and told the Cessna to turn behind the
departure, he believed that he had successfully resolved the
problem. When the crew of UAL889 requested another frequency to
talk to the tower on, the local controller advised the CIC that the
pilot was upset about the transition traffic, they had gotten "too
close," and the pilot wanted to talk to someone about it. The crew
was given a spare frequency to use, and did contact the CIC to ask
about the incident.
The local controller stated that his normal scan when clearing
an aircraft for takeoff is to scan the runway, check the radar
display, then go back to the runway. He said that in this instance,
he was distracted by the ground controller's taxi coordination and
missed checking the radar display until after the departure was
rolling.
The local controller stated that the tower has a procedure for
using a flight strip as a reminder that there are aircraft on the
transition route. It is his normal practice to physically place the
reminder strip on top of the flight strips for runway 28
departures, but in this case he did not use his normal procedure
and he was not sure exactly where he placed the strip.
The radar coordinator was assigned to SFO ATCT on November 23,
2008. She was still in training, and was certified on all positions
except local control and cab coordinator.
She described the duties of the radar coordinator as
coordinating with NCT, coordinating with the ground control
position about the use of taxiway Z at the west end of runways
28L/R, serving as a second set of eyes for local control, taking
handoffs, scanning strips, and updating proposed departure times to
prevent flight plan timeouts.
The radar coordinator had been on position about two minutes at
the time of the incident. She was engaged in coordinating a request
from ground control to cross the west end of runways 28 with one or
two aircraft. It was an extended exchange, and somewhat confusing
because there was training in progress at GC. The trainee asked for
one thing, and then the instructor changed it. The coordination was
done verbally directly between the radar coordinator and the ground
controllers, not on the interphone, so it was all audible to the
local controller and may have momentarily distracted him. When the
coordination with GC concluded, the radar coordinator reported
hearing the local controller instructing N9870E to "...pass
behind..." someone. She looked at the radar display and recognized
the conflict. UAL889 had just acquired a radar tag after departure.
With the training in progress and other activity in the cab, she
stated that, "...it was pretty loud up there."
When the radar coordinator took over the position, she did
receive a recorded position relief briefing that included
information on the Cessna, but she did not recall exactly what was
said. Transition traffic is a normal part of the relief briefing,
and she was aware of the Cessna when she took over the position.
She last remembers seeing the aircraft "...pretty far north" in the
tower's airspace, maybe near the Hunter's Point area or Candlestick
Park.
The controller-in-charge was assigned to SFO ATCT in 1991, and
was qualified on all positions in the tower cab. When interviewed,
he described the CIC's duties as "...answer the phones, watch the
operation, deal with breaks, and perform other administrative
duties."
Around the time of the incident, the CIC was essentially
occupied with administrative duties, and was not monitoring the
operation. There is no local requirement for the CIC to directly
monitor control positions. The CIC first became aware of the
incident shortly after UAL889 departed, when the local controller
told him that the pilot would be calling on frequency 128.65 about
a Cessna. The CIC looked at the radar display and saw the Cessna
about halfway between SFO and San Carlos. UAL889 was off the edge
of the radar display by then.
The pilot of UAL889 did call on the spare frequency to request
information on the incident. During that discussion, the CIC asked
the local controller if traffic had been issued, if the Cessna had
the B777 in sight, and if visual separation had been applied. The
local controller responded affirmatively to all three questions.
The CIC advised the pilot of that information, and the conversation
concluded.
After this incident, SFO ATCT management and controllers
initiated a review of the event and the circumstances leading up to
it. The following actions were taken:
- The supervisor on duty on the day of the incident conducted a
Quality Assurance Review, examining radio and radar recordings,
interviewing the local controller involved, and identifying
opportunities for improvements.
- The Air Traffic Manager discussed the incident with both pilots
via telephone, and met with the captain of UAL889 at the
tower.
- The facility produced a "Summary Report" of the incident,
itemizing the existing SFO ATCT procedures that should have
prevented it – including the ability to exercise more control
over transitions, assistance to the local controller by the radar
coordinator, use of memory aids, direct supervisor or CIC
monitoring of the local control position, and better control over
the timing of runway 28 takeoff clearances vs. transitioning
aircraft.
SFO ATCT also implemented short-term followup actions,
including:
- Face-to-face supervisory briefings on new mandatory procedures
for increasing awareness of runway 28 departures, including verbal
announcements in the tower cab, mandatory use of memory aids, and
focus on the radar coordinator's responsibility to assist the local
controller.
- Team briefings on this and similar past incidents, including a
replay of the UAL889 event.
- A Safety Risk Analysis panel that included an open discussion
between management and controllers on all aspects of the UAL889
event and possible corrective or mitigating actions.
- Issuance of an Operational Notice revising coordination and
control procedures for VFR transition traffic through the SFO class
B surface area.
- Establishing a panel to review and discuss the current
transition corridor, including representatives from the tower, SFO
Airport, FAA Flight Standards, Northern California TRACON, Air
Transport Association, the Aircraft Owners and Pilots Association,
and the National Air Traffic Controllers Association.
- Coordinating with other FAA facilities having a stand-alone
class B airspace position, such as LaGuardia and Newark, to discuss
such operations and determine whether such a position would be
beneficial at SFO.