NTSB report from the Eagle BOS gear up problem
Aviation Week and Space Technology, July 14, 2008
Seeing Green
American Eagle crew averts a gear-up accident with a just-in-time go-around
FRANCES FIORINO/WASHINGTON
Human-machine interface, crew decision-making and the value of "seat-of-the pants" flying will likely be discussed late this summer when the NTSB determines the probable cause of an American Eagle incident in 2007.
The event-an attempt to land with the gear retracted-nearly became one of aviation's fatal statistics. NTSB documents made available to Aviation Week & Space Technology reveal what transpired in the cockpit the morning of June 20, 2007,when the Embraer 135 regional jet (Flight 4539)was on approach to Boston Logan International Airport with 37 passengers and three crew on board. The crew told investigators that the flight was normal from pre-flight and takeoff from Toronto Pearson International Airport at 7:04 a.m, through en route and final approach to Runway 22L.
The first sign of trouble came when the crew noticed the "landing-gear lever disagree" light appear shortly after the first officer (the pilot flying) had pulled down the landing-gear lever. At this point, the aircraft was at about 1,500 ft. and on close-in final approach.
The cockpit voice recorder transcript (see excerpts) shows that the captain and first officer discussed the meaning of the gear lever indication. The captain was opting to continue the approach and the first officer concurred, although they continued the approach without following the checklist for the landing-gear lever disagree alert.
The flight crew said their decision was based on having "overwhelming indications "that the gear was down: Those indications included seeing a "three green" light on the lever and a written "three-green" on the radio management unit.The pilots also heard the gear doors opening.In addition, none of the normal alerts sounded in the cockpit to indicate the gear was not down-not the "landing-gear' warning when the aircraft was below 1,200 ft., nor the "too low gear" warning below 500 ft.
The first officer told investigators that he would not have continued the approach if there had been another sign that something was wrong.
Even the landing felt normal until just prior to touchdown, the crew told the NTSB. The first officer,with "seat-of-the-pants" flying instincts emerging, repeatedly remarked that "something feels weird ... it doesn't feel right," before calling for and executing a go around.
At this point, the aircraft fuselage scraped the runway, and controllers advised the crew that sparks were observed when the aircraft touched down, according to the NTSB. When the captain raised the landing gear during the go-around-he noted an immediate three-green landing-gear-up indication, which does not normally appear so quickly. Then, following the flight manual, the crew performed the checklist for the landing-gear lever disagree alert, which calls for recycling the landing gear. With the recycle, the crew noted a "three-green," indicating that the gear was extended. The crew, agreeing that "something was not right," then performed the Abnormal Landing Gear Extension checklist. After using the electrical override system, the crew said they felt three "clunks," which led them to believe the gear had extended normally.
The captain said he informed the first officer that he did not need to perform the emergency landing checklist because they were time-limited and he was familiar with the procedures on the checklist, according to the NTSB.
The crew discussed the situation with American Eagle maintenance operational control, and performed a flyby for a visual check of the gear extension by tower controllers. The tower advised that a pilot on the ground thought the gears to be canted at a 45-deg. angle. When extending flaps for the flyby, a "flaps fail" indication appeared, and flaps remained retracted for the remainder of the flight.The pilots executed a second fly by at lower altitude, at which time the tower observed that the extended gear position looked normal. The crew of Flight 4539 then decided to proceed with a second approach, with the captain flying. The crew debated whether to declare an emergency, then did so. Controllers vectored the flight to a longer runway, 33L, while passengers were briefed for a "brace-brace" landing. This time the aircraft touched down safely,and no injuries were reported.
The day after the incident, American Eagle issued a Safety Message to operators that reads in part: "Whenever the EICAS [engine indicating and crew alert system] warning 'LG/Lever Disagree' message is shown after gear extension, the landing gear should be considered unsafe, regardless of gear position indications on the EICAS or radio management unit. An immediate go-around must be initiated and the 'emerge/abnorm procedures LG/Lever Disagree' must be followed."
The NTSB, which has been engaged in more incident investigations in recent years, is likely to issue incident-related safety recommendations along with probable cause.
Excerpts from
NTSB Cockpit Voice Recorder Transcript
Recording Span 07:37:48 - 9:38:59am
08:18:06 [Boston Logan tower clears Flight 4539 to land Runway 22L.]
08:18:36 [Sound similar to altitude alerter)
08:18:48 [Sound of click and roar similar to landing gear operation)
08:19:10 [Sound similar to aural warning)
08:19:12 HOT-2 Landing gear disagree. We can't land with that, can we?
08:19:12 HOT-1 [Unintelligible) the[expletive) does that mean?
08:19:21 HOT-2 I don't know, but we can't land with that...got 22 ...What do you want to do?
08:19:33 HOT-1 We got three green
08:19:34 HOT-2 We do, but it's a discrepancy. What do you think?
08:19:38-08:19:40 HOT-l Keep going I think... I think we're alright with three green.
08:20:09·08:20:15. [Before-landing checklist is completed, aircraft approaching minimums.]
08:20:13 HOT-2 I hope that light's not broke.
08:20:34 HOT·2 If it doesn't feel right, tell me to go around.
08:20:51 HOT-2 Doesn't feel right, doesn't feel right (sound of impact)
Crew initiates go-around, consults with airline maintenance, performs two flybys and runs through abnormal emergency landing procedures, attempts second landing.
09:29:32 HOT-2 Brace, brace, brace
09:30:00 [Sound similar to aircraft touchdown on runway]
Legend: HOT-1: Captain; HOT-2: First Officer
Source: National Transportation Safety Board, cockpit
Voice Recorder Transcript from the Group Chairman
Factuol Report (June 25, 2008)