NTSB Report Details How Close United Airlines Flight 889 Came To A
April 18, 2011 - United Airlines Flight 889 (N216UA) had just departed San Francisco Airport, California for Beijing, China with 268 onboard on March 27, 2010, when an operational error occurred at the San Francisco Airport Traffic Control Tower (SFO ATCT).
Flight 889 (UAL889), a Boeing 777 and a Cessna 182 (N9870E) 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).
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.
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 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 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
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.
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.
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.
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
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
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 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.
SFO ATCT also implemented short-term follow-up actions, including:
|?AvStop Online Magazine Contact Us Return To News|