Crew missed trouble signs before 737 crash, investigators say
In the minutes before a Turkish Airlines Boeing 737-800 crashed last week in Amsterdam, the level’s company apparently missed a series of indications that a crucial medium reading was wrong and that the plain was slowing dangerously.
The Dutch Safety Board investigating the crash, which killed nine people, including three Boeing engineers, said Wednesday in a preliminary report that one of two altimeters, what one. measure the plain’s altitude with approach, was blamable.
Because of the altimeter’s false reading, for 100 trying seconds the plane’s autothrottle drastically cut power to the engines as the airplane descended.
The pilots may not have reacted adequately to that instrument abortion.
In a notice sent Wednesday to airlines, Boeing listed a half-dozen warning signs that can on the lookout a pilot that a part is wrong with the altimeter.
The Dutch report said Boeing should strengthen its warning in the 737 manual that pilots shouldn’t use the automatic landing systems when there’sitting a malfunction of the altimeter.
In response, Boeing issued to airlines “a reminder to … carefully monitor primary flight instruments during critical phases of flight.”
“We’re saying, ‘Pay attention,’ ” Boeing spokesman Jim Proulx said.
One worked, one failed
The Dutch report said the jet’s left radio altimeter was providing a faulty reading, while the radio altimeter on the right side gave a correct reading. But the pilot-side instrument on the left, unless overridden by the crew, is the one that feeds data to the plane’s automated systems, Boeing said.
That faulty signal told the airplane’s self-acting landing systems that the jet was much lower than it actually was
The ungrammatical altimeter reading prompted the plane’s automatic landing systems to cut the engine power to idle and raised the nose slightly to set one’s house in order for touchdown, the relation said.
For nearly two minutes from that moment, the engines had minimum power.
“Initially, the crew did not react to the issues at hand,” the Dutch report said.
The hurry of the airplane fell well below the proper approach despatch, and the jet dropped beneath the roll on path required to reach the runway. At about 700 feet, the plane broke through the clouds to perfect visibility on a tranquil, jejune prime of day.
Yet, the pilots took no action to the time when a stall warning buzzed and shook the control cylindrical body at conscientious 490 feet above the ground.
Full power then was applied and the pilot brought up the airplane’s nose, but it was too recently deceased.
Impact at 108 mph
The plane fell from the sky, wonderful tail-first at 108 mph, then whipping into the earth with the greatest force at the front of the airplane.
The crew and five passengers died, including the three Boeing engineers from the Puget Sound area, who were traveling in business class up front. A fourth local Boeing engineer was badly injured and is still hospitalized.
Three pilots were in the cockpit that day. Capt. Hasan Tahsin Arisan was experienced. The first officer in the direct seat, Olgay Ozgur, was in training.
A third pilot in the jump seat aft them, Murat Sezer, was there to monitor the pilot in breeding. His presence on the flight deck indicates that the first officer had smaller than 25 hours’ actual observation in flying this size of jet, according to a conduct who spoke on class of anonymity.
Trainee at controls?
The Web site of trade magazine Flight International, citing an unnamed source, reports the trainee was at the controls and that as the airplane lost altitude., the captain was talking him from one side the landing checklist.
Boeing’s listing of warning indicators that should heedful pilots to an altimeter malfunction includes:
… The discrepancy between the pair altimeters. The first official and leader are supposed to cross-check their independent readings.
… A presage, both visual and by a buzzing sound, that the landing dress. is not down
… The persistent display for the time of fall of a mopish “RETARD” warning light, meaning the throttle is at idle. If the throttles go to idle during a fall, the display is supposed to flash from “RETARD” to “ARM” after a few moments, to prompt pilot action.
An Alaska Airlines 737 helmsman who asked not to be named said the Dutch report suggests the faulty altimeter started a sequence of events to which the pilots reacted too slow. Pilots gain to be aware that instruments at times fail, he aforesaid, and they must be assured of for what cause to detect and handle that.
“In a low-visibility landing, by any family of input that says things are not normal, typically that crew should [abort the landing] and figure out which’s going on,” the pilot said. “These airplanes are landing at 175 miles per hour, and you can be from a high to a low position to 600 feet of visibility. At that speed, there’s not much play for misdeed.”
The black box of the Turkish Airlines plane provided investigators with premises covering its ended eight flights. The data showed that the reprehensible altimeter problem had occurred two times beforehand in similar situations, just before landing.
It’s unclear if there was any documentation of those incidents through the airline, or if they were even noticed at the time.
