Cockpit setup implicated in Houston Gulfstream crash
The probable cause of the Nov. 22, 2004 crash of a Gulfstream III during an attempted ILS Runway 4 approach to William P. Hobby Airport in Houston, according to the NTSB, “was the flight crew’s failure to adequately monitor and cross-check the flight instruments during the approach. Contributing to the accident was the flight crew’s failure to select the instrument landing system frequency in a timely manner and to adhere to approved company approach procedures, including the stabilized approach criteria.”
The full accident report and the NTSB’s analysis shed even more light on the subtle factors that contributed to this accident. These factors center on the configuration of the accident GIII’s electronic attitude director indicators (EADIs) and the configuration of EADIs installed in other jets that the two pilots flew. Other factors noted in the report are the communication between the pilots and their failure to use approved company approach procedures.
The flight was to pick up passengers at Houston for a trip to Guayaquil, Ecuador. That one of the passengers was a famous person is mentioned in the NTSB report, but the fact that the flight was supposed to transport former president George H.W. Bush to Guayaquil seems to have no bearing on the accident, and it isn’t clear why the NTSB included this information.
The pilots and a flight attendant, all employed by Business Jet Services, departed their home base at Dallas Love Field at 5:30 a.m. on November 22, a half hour later than planned due to poor weather in Dallas and Houston. The captain was at the controls, according to the NTSB.
At 5:42 the pilots listened to Houston ATIS Quebec, which noted that weather conditions were one-eighth mile visibility, RVR for Runway 4 between 1,600 and 2,400 feet, broken clouds at 100 feet and overcast at 9,000 feet.
The first officer contacted Houston Tracon at 5:58, saying he had information “Kilo” (not Quebec) and then after being cleared “when able” for the ILS Runway 4, acknowledged by saying “ILS Runway 14” instead of “Runway 4.” The first officer then said, “I’ll set up our ILS, in here, one oh nine nine.” The Tracon controller didn’t question the incorrect readbacks.
The flight proceeded, with Tracon clearing the Gulfstream to descend to 3,000 feet, then providing a vector and instructions to maintain 2,000 feet until established on the localizer and a clearance for the ILS Runway 4 approach. The first officer started the before-landing checklist.
At 6:11, according to a subsequent NTSB performance study, the Gulfstream was descending through 2,900 feet when it turned left to line up with the localizer, then leveled at 2,300 feet. The Tracon controller handed the airplane to Hobby tower, and the first officer told the controller, “With you on the ILS.” The Gulfstream was cleared to land on Runway 4.
A minute later, the captain told the first officer, “I can’t get approach mode on this thing [the flight director],” and the first officer said he was having the same problem. At 6:13 the Gulfstream had descended through 2,000 feet and was already 1,000 feet below the glideslope.
The first officer said, “Gear down” at 6:12:40, then asked, “What is wrong with this?” The captain responded that he didn’t know. The first officer then asked, “What do we have set wrong? We have long range or something that we shouldn’t have.”
The captain said, “Got NAV, VOR one.”
“OK, we’re high on the glideslope, now,” the first officer replied.
The captain said, “…just gonna have to do it this way.”
The first officer then said, “Guess so, yeah, you’re on the glideslope now.”
According to the NTSB performance study, at this point the Gulfstream was 700 feet below the glideslope, at about 1,700 feet. The Gulfstream had never been lined up with the localizer centerline and was still more than two dots off the centerline.
Just before the airplane reached 1,000 feet, the captain asked the first officer if they would be descending to 244 feet. The first officer replied, “Yeah.”
Seconds later, the captain asked, “What happened? Did you change my frequency?”
The first officer said, “Yeah, we were down there, the VOR frequency was on. We’re all squared away now, you got it.”
The captain said, “Yeah, but I don’t know if I can get back on it in time.”
“Yeah, you will,” the first officer responded. “You’re squared away now.”
The NTSB performance study revealed that after the captain’s question the Gulfstream turned right and finally intersected the Runway 4 localizer centerline. The Gulfstream was 800 feet below the glideslope and still more than three miles from the airport.
“I’m, I’m outside,” the first officer said at 6:14:32, then he added, “OK, comin’ up on two forty four.”
The automated radar terminal system minimum safe altitude warning went off at 6:14:35, with visual and audio warnings provided to Houston Tracon and Hobby tower controllers. The captain completed the before-landing checklist at 6:14:42, asking for full flaps.
The final cockpit voice recordings began at 6:14:45, with the first officer saying, “Up, up, up, up, up, up, up.” At the same time, the Hobby controller called, “Check your altitude, altitude indicates 400 feet.” There was no response.
The Gulfstream hit a light pole at about 198 feet and 3.25 miles from the Runway 4 threshold. Both pilots and the flight attendant were killed, and a person in a vehicle on the ground was injured.
In its analysis of the accident, the NTSB could not figure out why the Gulfstream’s ground proximity warning system (GPWS) did not provide any alerts to the pilots. A radar altimeter failure could have prevented the GPWS from working, the NTSB reported, but there was no evidence of such a failure. By March 29, 2005, the Gulfstream operator would have had to install EGPWS with a terrain database and positional awareness.
The NTSB noted that the first officer began the approach briefing, but that Business Jet Services standard operating practices require the captain to brief the approach. The briefing on the accident flight didn’t include all approach checklist items, omitting, for example, final approach fix altitude, the report said.
The pilots were heard on the CVR discussing deleting the Hobby VOR from the approach waypoints in the FMS. “The MFD only displays a chronological number for each approach waypoint; therefore, it is possible that the flight crew forgot that the first officer removed the HUB [VOR] waypoint from the FMS, causing them to mistakenly believe that the last waypoint displayed on the MFD (eisen) was the airport,” said the report. In fact, eisen is the final approach fix for the ILS Runway 4 approach.
The NTSB analysis then outlines what investigators thought the pilots did that led them to fly below the glideslope into the light pole. The report noted, “The pilots should have been relying on the primary navigational aids during the approach.” And indeed the NTSB believes this is what the pilots were trying to do.
After receiving the approach clearance, the first officer entered the ILS frequency into both VHF nav receivers, in the standby position, at about 5:59. Yet when both pilots said they couldn’t get apr mode on their flight directors, the first officer told the captain they were high on the glideslope and then on the glideslope, but the Gulfstream was actually 700 feet below the glideslope.
The report said that with the ILS frequency not set in the primary position of the nav receivers, “the glideslope indicator would not have been visible on the EADI. Therefore, the first officer could not have been looking at the glideslope indicator when he made the statements about the glideslope.”
So what were the pilots viewing that made them think they were on the glideslope?
The NTSB believes that the pilots were following the fast-slow indicator on the Gulfstream’s EADIs. When the first officer failed to activate the ILS frequency (move the frequency to the active position), this “prevented the flight crew from recognizing that the airplane was off course and below the glideslope,” the report noted.
The EADIs on this airplane had a fast-slow indicator that shows whether the airspeed is above or below a target airspeed. “The glideslope and fast-slow indicators are the same color and about the same size. Each indicator consists of a moving pointer on a rectangular display, and each display has markers above and below the rectangle to indicate the degree of deviation.”
In the accident Gulfstream, the glideslope indicator was on the left side of the EADI and the fast-slow indicator on the right side. According to the NTSB, five other Business Jet Services airplanes had similar configurations (one did not have the fast-slow indicator), while three had the opposite setup, with the glideslope on the right side and fast-slow indicator on the left. The NTSB report noted that FAA Advisory Circular 25-11, dated July 16, 1987, “recommends standardizing the location of the glideslope indicator to the right side of the main display; however, the accident airplane was manufactured before this guidance was issued.”
What NTSB investigators believe the pilots saw during their approach to Hobby Airport was the fast-slow indicator centered within one dot, “and that the indications would have been consistent with the first officer’s comments about the glideslope if he had mistaken the fast-slow indicator for the glideslope indicator.”
One mile before impact, according to the NTSB, the first officer finally switched the nav so the ILS frequency was in the primary position. At this point, both pilots’ EADIs would have shown a full-scale deviation below the glideslope and full- or nearly full-scale deviation of the localizer, the report noted. Neither pilot mentioned seeing these deviations on the CVR.
The NTSB report noted that the fast-slow indicator, which investigators believe the pilots were watching, would still have been displayed after the glideslope indicator finally came alive, “which may explain why the pilots did not immediately notice the glideslope indicator deviation after the first officer selected the ILS frequency. Therefore, the pilots most likely mistook the fast-slow indicator for the glideslope indicator throughout the approach sequence.”
The report faulted the first officer for not immediately calling for a missed approach when he realized that he had not switched the ILS frequency to the active position on the nav receiver, “because the airplane was not properly configured for the approach and was not receiving proper vertical guidance during the most critical phase of the flight.”
The captain also should have called for a missed approach, the report stated, instead of querying the first officer when the ILS frequency finally was switched, when he said, “What happened? Did you change my frequency?” As a result, the NTSB questioned the communication between the two pilots. “The Safety Board is concerned that the first officer switched the frequency of a primary navigational aid and failed to inform the captain. If the pilot-not-flying takes such actions without first checking with or simultaneously informing the flying pilot, confusion can occur,” the report explains.
As the pilots focused on correcting back toward the localizer, likely still following the fast-slow indicator instead of the fully deviated glideslope, the captain did not assert his authority, the NTSB said, when the first officer dismissed the captain’s concerns about getting the airplane back on the localizer in time by responding, “Yeah, you will, you’re squared away now.”
The sole required altitude callout, only one of many that were supposed to take place, occurred just before the Gulfstream hit the light pole, when the first officer said, “OK, comin’ up on two forty four.”
The NTSB said that the pilots did not activate and identify the ILS frequency at the correct time, failed to engage the apr mode on the flight director and did not adequately scan the cockpit instruments. Doing so would likely have prevented the accident, the NTSB report concluded.
While the NTSB could not determine how much sleep each pilot got before the flight, “fatigue might have also played a role in the flight crew’s degraded situational awareness.” The captain’s wife told the NTSB that he had slept four hours less than normal the night before the flight. “Regardless, their improper conduct of the approach reflected fundamental operational shortcomings that were independent of fatigue,” the report concluded.
Both pilots were highly experienced. The captain, 67, had about 19,000 flight hours and had worked for Business Jet Services since 1998. The first officer, 62, was hired in April 2004 and was also the company’s chief pilot. He too had logged more than 19,000 hours.