How Qantas Crew Responded In 747-400 Vibration Incident

[Guest]

How Qantas Crew Responded In 747-400 Vibration Incident

Jun 30, 2017John Croft | Aviation Daily

Australian Transport Safety Bureau

 

WASHINGTON—Australian investigators have noted the resourcefulness of a QantasBoeing 747-400 crew in attempting to isolate the problem that was causing abnormal vibrations during a flight last year, and determining the aircraft could continue to its destination safely. 

The crew noticed unidentifiable vibrations in the area around the left over-wing door on the 14-hr. flight from San Francisco to Sydney in October 2016.

“In consultation with both maintenance and operational control and cabin crew, the crew systematically isolated systems capable of generating the vibration,” the Australian Transport Safety Bureau (ATSB) says in a newly released final report on the incident. “While they were unable to identify the source of the vibration, the flight crew established that it was constant, and that the aircraft was otherwise performing normally. In the absence of any abnormal flight-deck indications or relevant checklist, the decision to continue the flight was therefore at the discretion of the flight crew based on their professional judgement.”

Investigators determined that the aircraft’s main landing gear was mostly likely struck by a bird on the night takeoff from San Francisco, according to the report, which includes further details on the incident. The bird strike sheared off a strut that connects a small door to the gear body. With the strut broken, the door would have remained open for the entire flight, creating the vibration and louder-than-normal noise levels. The door did not have a proximity sensor that would have alerted the crew to its open or closed state.

Soon after takeoff, a cabin crew supervisor seated near door L3 (the left over-wing door) contacted the cabin services manager reporting “vibration and louder than normal cabin noise” in the area, the ATSB report notes. A training captain on the flight deck later told the ATSB he also remembered “being aware of a louder than normal noise” during the climb, although there were no abnormal indications on the flight deck.

Nearing its cruise altitude, the second officer left the flight deck and inspected several sections of the cabin along with the flight attendants, finding the largest vibration near the L3 door where it was “considerably noisier than normal,” the ATSB says.

About 2 hr. into the flight, the pilots used a satellite phone to call the company’s maintenance operational control (MOC) for advice from a duty manager and senior aircraft engineer. The MOC duty manager reportedly advised the crew that the vibration and noise could be due to issues with a gear-door seal or wing-to-body seal. The duty manager also researched other possible sources, including systems near the L3 door that could generate the noise and vibration, and the aircraft’s maintenance history.

Based on that research, the ATSB says the flight crew then systematically went through a process of trying to identify the source of the problem by isolating or considering several components and systems. Included were the air-conditioning packs, air-recirculation fans, relocation of the gear handle to the up position, and checking toilets for possible vacuum leaks.

“That troubleshooting was unable to isolate the source of the vibration and noise,” the ATSB says. After asking the cabin crew to continue monitoring the noise and vibration, the pilots decided to continue the flight as the “aircraft was otherwise performing normally.”

About 4.5 hr. into the flight, with no change in noise or vibration levels, the training captain left the flight deck to make another assessment and found that it was “still quite noisy,” according to the ATSB. The flight crew then contacted the MOC again for additional guidance, asking the duty manager what other aircraft systems were in the L3 door area. The duty manager advised that there were hydraulics and center-fuel-tank transfer pumps, but the crew could not isolate the hydraulics and the transfer pumps were turned off.

“The duty manager advised the crew that maintenance services were available at the now-nearby Honolulu [International] Airport in Hawaii and inquired if the crew wished to divert” the ATSB says. “The crew advised the MOC that they did not intend to divert at that stage.”

The training captain told the ATSB that since the aircraft was otherwise performing normally, it was “not considered necessary to divert from the original destination.” The vibration and noise continued throughout the flight until the landing gear was deployed, and apparently was not noticed by the passengers.

“This occurrence highlights that, even with the assistance of sophisticated technology and systems, flight crew may experience situations that can only be managed using their professional judgement,” the ATSB adds. “The crew utilized available crew resources and maintenance expertise to troubleshoot and assess that the flight could safely continue to the destination airport."

[Boney]

An interesting CRM senerio. Good job on this crew.

[DEFCON]

The Captain was placed between a rock and a hard place on that one. There really should be a policy in place to deal with situations like that.

[blues deville]

This situation worked out but I think if you can't confirm the exact nature of a problem no one will fault a decision to land and investigate. That's a long trip over mostly Ocean to spend time troubleshooting however the skipper being a trainig Captain in this case probably altered the decision process.

[DEFCON]

Rich

I understand your position completely, but let's look at the situation through a different lense for the sake of debate; if the source of the vibration in this case was the harbinger of a coming catastrophic failure and the subsequent hull loss was later determined to have been preventable had the airplane landed before all safe landing sites were too far behind, you can bet there'd be a policy in place in short order.

I understand the ETOPS rules don't apply in this case, but I'm wondering; do said regs address unusual mechanical conditions & crew considerations?

 

 

[UpperDeck]

If I'm on a boat with no responsibility for passenger safety and I detect a constant vibration that is significant, I will assume it might impair the continued safe operation of the vessel and take all steps to mitigate. That necessarily includes deviation from my intended route to the nearest safe port.

In my humble ( honest!) opinion, everything SEEMED to be okay on the flight as evidenced by instrumentation and feel except there was a loud and unexplained vibration.

Prudence would suggest diversion.

[Vsplat]

44 minutes ago, UpperDeck said:

Prudence would suggest diversion.

That would presume a diversion is risk free.  While diversion may be low risk in domestic or continental airspace, especially if the diversion airport is served by your airline and type, that was not the case here.   Even an air return to origin has its considerations.

It is important to weigh risk, it is what we do.  When I read the number of steps and resources the crew employed, it is hard for me to call their decision imprudent. 

There is another thread on this forum, the 787 diversion.  Have a read there and consider the varying opinions of what was and was not prudent.

Hard to win in the court of public opinion.

Vs

[DEFCON]

"A training captain on the flight deck later told the ATSB he also remembered “being aware of a louder than normal noise” during the climb, although there were no abnormal indications on the flight deck."

If you can hear a noise on the FD of a 744 that's later determined to be coming from the area described, it's got to be pretty darn loud.

I wasn't there, but because I've experienced & trouble shot weird in flight noises with the help of crew & mtx myself, I can accept the decision this crew made for what it was. On the other side, I can't tell you I'd have been very comfortable as a pax knowing the crew intended to carry on with the mission in spite of the mysterious noise either.

I would only hope economics wasn't part of the decision making process in this case.

 

     

[blues deville]

I was thinking the same Defcon that I wouldn't be too thrilled about vibrating all the way to Sydney no matter how confident Captain Dundee was about his airplane. 

[UpperDeck]

3 hours ago, blues deville said:

I was thinking the same Defcon that I wouldn't be too thrilled about vibrating all the way to Sydney no matter how confident Captain Dundee was about his airplane. 

But Blues....I said the same thing before Defcon. How come you didn't agree with me.....a mere plebian?

[blues deville]

100% agree. Sorry UD. Missed fully reading your post. 

I suppose this being a 747-400 perhaps we can cut the skipper some slack. My last and only 4 engine jet across any pond was a DC8. There weren't too many flights were I was fully confident (lowly FO)  in the old Douglas. It took me a year to figure out it wasn't a safe place to stay working and I left to greener pastures and lucky for me brand new aircraft. What a treat!