LAX00FA041

The DC-10 captain, in response to a Traffic Collision Avoidance System (TCAS) alert, made an aggressive pitch change and felt a slight buffet as the airplane decelerated. The maneuver resulted in wrinkling of the elevator skins. Air Traffic Control (ATC) instructed a DC-9 crew to maintain visual separation and the DC-9 crew accepted the instruction. The airplanes were about 7 miles from each other in night conditions on converging courses; the DC-9 was descending out of 5,000 feet and the DC-10 was climbing through 3,800 feet. The controller had to repeat instructions to the DC-10 crew, as well as other crews. One crew informed ATC that their radio transmissions were weak. Douglas Flight Operation Letter AOL, C1-E60-HHK-L033 dated January 21, 1988, explained probable resultant damage to aircraft components when speed was reduced to buffet speeds indicated on the Cruise Buffet Onset Boundary Chart as presented in the DC-10 Aircraft Flight Manual. It noted that in some cases this buffeting resulted in wrinkled outboard elevator skins. It emphasized that speed reduction down to or near the clean configuration stalling speed greatly increased the chance of experiencing elevator damage.

History of flight

On November 7, 1999, about 2120 Hawaiian standard time, Gemini Air Cargo Flight GCO7580, a McDonnell Douglas DC-10-30F, N602GC, responded to a Traffic Collision Avoidance System (TCAS) alert 5 minutes after departure from the international airport (HNL) at Honolulu, Hawaii. Gemini Air Cargo of Dulles, Virginia, was operating the nonscheduled international cargo flight under the provisions of 14 CFR Part 121. The airline transport pilot (ATP) rated captain and four crewmembers were not injured. The airplane sustained substantial damage to both elevators. Night visual meteorological conditions prevailed and an IFR flight plan had been filed. The flight originated in Los Angeles, California, made an en route fuel stop at Honolulu, and was continuing to Fiji with an ultimate destination of Sydney, Australia. The flight departed Honolulu about 2115.

The captain was flying the airplane and the first officer made the radio transmissions. The captain stated that he was familiar with this airport and route. He thought the clearance and departure instructions were routine. He said that at 3,000 feet, the airplane normally climbed at 1,500 to 3,000 feet per minute (fpm). This flight was heavy and the company's operating manual allowed climb rates between 500 and 1,000 fpm; he chose 500 fpm.

The TCAS alert involved an Hawaiian Airlines DC-9, Flight 561, which was en route to HNL. The Safety Board Investigator-in-charge (IIC) made a transcript of recorded radio transmissions. All times are local (HST); altitudes are mean lea level (msl); and the same controller was working arrivals and departures for air traffic control (ATC). The Hawaiian flight was labeled as H561 and the Gemini flight as GAC. ATC was also working other flights.

Honolulu Center Enroute Radar Approach (CERAP) provided recorded radar data, which included computed latitude and longitude positions for both airplanes.

At 1916:13, H561 was at 10,000 feet when they checked in with ATC on Frequency 118.3. ATC instructed them to fly a heading of 260 and descend to 1,500 feet.

After departure from runway 8 right, GAC checked in at 1917:58 and reported they were in a right turn to 155 degrees and climbing through 1,300 feet. ATC advised that they had radar contact, instructed GAC to climb and maintain Flight Level 280, and turn right to a heading of 220. At 1918:18, GAC repeated their check in call, but they were now climbing through 2,500 feet. ATC repeated that they had radar contact, and instructed GAC to fly a heading of 140 degrees.

At 1918:59, ATC advised H561 of traffic at the 1 to 2 o'clock position, 8 miles, a heavy DC-10 climbing through 3,000 feet. H561 reported the traffic in sight, followed immediately by instructions from ATC at 1919:15 to maintain visual separation. H561 acknowledged, "Visual with him." At 1919:23, ATC informed GAC of traffic at the 12 o'clock position, 7 miles; it was a westbound DC-9 descending through 5,000 feet that had GAC in sight. ATC informed GAC to maintain visual separation. GAC responded at 1919:31 that they had the traffic in sight, but did not acknowledge maintain visual separation. At 1919:58, ATC advised H561 to maintain 1,500 feet.

At 1920:31.655, the CERAP readout of recorded radar data indicated that the mode C reported altitude of H561 was 100 feet less than that of GAC. The IIC used Safety Board software and computed the distance between the targets to be 0.3 nm on a magnetic bearing of 136 degrees.

At 1920:41, GAC acknowledged instructions to resume own navigation. At 1921:06, another airplane informed ATC that ATC was coming in weak at times, but ATC made no query or response to that transmission. The transcript indicated that several airplanes asked ATC to repeat instructions. At 1923:11, GAC acknowledged ATC instructions to contact Honolulu Center on frequency 126.5.

The IIC interviewed the GAC crew. The captain said he was maintaining assigned vectors and course when ATC pointed out traffic at the 10 o'clock position at 5,000 feet. He had not heard any previous conversation between ATC and his traffic, and did not recall ATC informing him what the traffic's flight profile would be. He was climbing through 3,800 feet when he saw the traffic at the 10 o'clock position, and the TCAS said it was 1,200 feet above his position. He thought the traffic would stay above him. The captain did recall the first officer acknowledging an instruction from ATC to maintain visual separation. He did not recall any communications problems with ATC or of them informing him of any problems.

The GAC first officer advised the captain to shallow the climb to maintain separation. H561 appeared to still be descending at the 10 o'clock position. The first officer recalled acknowledging the traffic in sight.

According to the GAC crew, the TCAS in the DC-10 alerted "traffic, traffic" followed shortly by the alert "climb, climb, climb." The TCAS indicated a resolution advisory of 1,200 feet per minute rate of climb in the red on the vertical speed indicator. The captain made an aggressive pitch change to 15 degrees or more nose up attitude to attain 1,200 to 1,500 feet per minute rate of climb. Passing 4,000 feet the TCAS reported, "clear of conflict." The captain noted that as the airspeed bled off from 282 knots to about 250 knots, he felt a slight buffet. The first officer and flight engineer also felt the buffet. The captain resumed his normal climb profile.

After passing through 10,000 feet and switching to the en route frequency, the captain passed control of the airplane to the first officer. The captain contacted departure control to inform them of the close encounter, but he did not file a near midair collision report. Departure control informed him that they did not receive a traffic conflict, and they did not know if the DC-9 received a TCAS alert.

The H561 captain submitted a written statement. He stated that they received a TCAS traffic advisory that GAC was about 6 miles away, 500 feet below their altitude, and climbing in excess of 500 fpm. They maintained a 2,000 fpm rate of descent and expected that they would pass well below GAC. A couple of seconds after the traffic advisory, they received a TCAS resolution advisory to monitor vertical speed. Per their operating procedures, they maintained or slightly increased their rate of descent. ATC repeated the clearance for them to descend to 1,500 feet, but gave no indication of a pending conflict with GAC. They received no other aural advisories from the TCAS, but the display lit up red except for a small green band in the 4,000 to 6,000 fpm descent range. The captain increased the rate of descent substantially and passed directly below GAC, which indicated +500 on the TCAS display. He said he could hear the engines of the DC-10, and more than one passenger remarked to a flight attendant about the proximity of the other airplane.

The H561 captain said he called ATC from company offices and tried to speak to the controller. He was transferred to another number and spoke to a person who identified himself as a supervisor. The captain said the supervisor told him that they were having communications problems with GAC and had been unable to issue him turn directions. The captain said the supervisor did not know if the controller had received a conflict advisory on his screen, but said that once pilots agree to visual separation, controllers tend to ignore such warnings.

The DC-10 proceeded to its destination of Nandi, Fiji, for a fuel stop and scheduled crew change. The crew consisted of a captain, first officer, flight engineer, and a flight mechanic. Both crews inspected the airplane during the night (0300 local time) prior to its departure for Sydney, Australia, and detected no discrepancies.

During a walk around inspection at Sydney during daylight, maintenance personnel observed that both ele