British Airways Flight BA38 Crash Lands At Heathrow Airport

[SteveHd]

The 777 is essentially "fly-by-wire" but the physical media is mostly fiber optics. Electronic control of the throttles has used for decades and FADEC [full authority digital engine control] since ~80s. "Full authority" means no manual override.

 

[viking1]

That's an amazing story Claire! See?! Every pilot should learn how to glide!

I hope they find the root cause of this and are able to discover how to fix it should it happen again. I take it the 777 is completely fly-by-wire? The throttle doesn't actually mechanically change the flow of fuel?

If it's like most "by wire only" control systems (including those on modern automobiles) the operator input tells the computer control system that you want more power, the computer actually changes the fuel rate via electrical actuators. Throttle by wire autos work the same way.

 

[2322]

What I figured. There is no mechanical linkage from the throttles themselves to the fuel flow controller.

I ran into that problem with my Saab 9000. Damn throttle computer fried and cost $1000 to be replaced and right after that the second computer that manages accelerator pedal input died too. That was another $800.

If it's like most "by wire only" control systems (including those on modern automobiles) the operator input tells the computer control system that you want more power, the computer actually changes the fuel rate via electrical actuators. Throttle by wire autos work the same way.

 

[viking1]

What I figured. There is no mechanical linkage from the throttles themselves to the fuel flow controller.

I ran into that problem with my Saab 9000. Damn throttle computer fried and cost $1000 to be replaced and right after that the second computer that manages accelerator pedal input died too. That was another $800.

Yep, my Toyota pickups are the same way. What gear, how much throttle,
what actual fuel mixture, what ignition timing, what valve timing, are all controlled by the computer. When the operator pushes the accelerator, the computer decides how the engine and transmission respond based on many sensor inputs. You are only telling the computer "I want more power".

It's very weird until you get used to it a bit. Very different from older all mechanical vehicles.

 

[dong20]

....Every pilot should learn how to glide!

They do!

I hope they find the root cause of this and are able to discover how to fix it should it happen again. I take it the 777 is completely fly-by-wire? The throttle doesn't actually mechanically change the flow of fuel?

Yes, as stated by others it's decoupled. Many modern commerial aircraft use this methodology.

 

[ClaireTalon]

They do!

But unfortunately real experience of gliding long distances is reserved to glider pilots (the captain in the Air Canada incident I mentioned above was a spare time glider pilot). The main difference between gliding a glider and gliding a several hundred tons airliner is that the latter one is not optimized for gliding, plus the engines don't only deliver propulsion, but also electric energy for the instruments and electric drives (flap actuators, trim, ...), plus the pressure in the hydraulic systems is delivered by pumps driven by the engines. The functions of both systems are reduced if both engines fail.

 

[SteveHd]

Claire, if all engines fail, does the APU provide enough power to run those systems minimally?

 

[ClaireTalon]

Claire, if all engines fail, does the APU provide enough power to run those systems minimally?

No, what should it run with? It's basically just another, smaller turbine that drives a generator and a generator through a CSD transmission. But it requires fuel just as any other engine. As the name says, it's auxilliary, not back-up.

There is another gadget, called a RAT (ram-air turbine), which is a propeller that drops free from between the main landing gear wells through gravity extension if the electricity fails. However, it only provides minimum pressure for the hydraulic pressure, and for absolutely essential electric systems. It works basically like a wind turbine.

 

[aussiebum20]

As a flight attendant I have to say good for the flight attendants on that flight. The training that we repeat once a year mandates that we evacuate the plane in ninety seconds if there should be an emergency. They did this that day! Its actually really tough! Amazing that there was no prep or notification.

 

[earllogjam]

More likely La Ceiba than San Pedro Sula which is a few miles inland. I only passed through SPS on the way to San Salvador. That was a flight to remember, into San Salvador right through an early evening storm. Talk about rough. I never went to Roatan or Guanaja though I heard the diving on Roatan was good.

The thing I liked best about La Ceiba was the little park with a small pond full of alligators! I used to fly back every couple of weeks for the luxury of 24hr power, a/c a decent bed and a change of diet! One night was enough. I did the boat trip once or twice, for a short crossing it could be rough. They introduced a newer bigger boat but it was worse than the small one so mostly I flew. I think it was about $20 but it was a while back.

Roatan was a very sleepy paradise when I went in the late 80's but I've heard it is very developed now. Beautiful white sand beaches. The diving not so great a week after a storm however. The thing I remember most of the trip were the vicious sand fleas on Cayos Cochinos, where I stayed and the bucket full of lobster tails picked off the sea floor for dinner.

I may have gone thru La Ceiba coming back but I don't remember it very well, not even the alligator pond. I was there in the late 80's.

 

[SteveHd]

Claire, does the R.A.T. *They could have made a better acronym.* produce more power than the APU? I know that in some [most?] aircraft the APU can provide enough power to start the engines.

-------

aussiebum20, I second your compliment to the flight attendants. They often don't get the kudos they deserve.

 

[dong20]

But unfortunately real experience of gliding long distances is reserved to glider pilots (the captain in the Air Canada incident I mentioned above was a spare time glider pilot). The main difference between gliding a glider and gliding a several hundred tons airliner is that the latter one is not optimized for gliding, plus the engines don't only deliver propulsion, but also electric energy for the instruments and electric drives (flap actuators, trim, ...), plus the pressure in the hydraulic systems is delivered by pumps driven by the engines. The functions of both systems are reduced if both engines fail.

Well yes of course, I couldn't be bothered to go into detail.:smile:

My experience of gliding a 'powered aircraft' was pretty much limited to certification requirements though I sometimes did it for fun. I've never flown or even been in a glider.

If it will fly it will glide, well apart from some modern jet fighters it seems at least without computer back up. They finally moved the wreckage over the weekend. I bet it made a sobering sight for passengers!

 

[dong20]

Claire, does the R.A.T. *They could have made a better acronym.* produce more power than the APU? I know that in some [most?] aircraft the APU can provide enough power to start the engines.

Jet engines require air flow/pressure to start not (just) electrical power. The APU provides this on the ground. Inflight; in simple terms, engines are restarted in variety of ways, rapid restart (to take advantage of the existing rpm speed - but beware of overheat), APU assisted restart (as on the ground) or as last resort by flying at the appropriate speed to generate the required airflow/inlet pressure, introducing fuel and then igniting it. Et Voila, a windmill restart occurs, one hopes! This isn't first hand knowledge, only what I've learned over the years from flight crew and reading - my hands on experience is single prop only, I'm sure Claire can fill in the details.

On the gliding theme; a 'typical' passenger jet will fly for about 85 miles even if it lost all power at about 35,000 feet. Basically count on about 10-12 feet forward for each foot lost (Lift/Drag ratio). I seem to recall that the B747 has a ratio of about 17.5 but that's a maximum and I've seen other calculated values. That of a B777 is a maximum of about 19.5 I believe. These values vary with speed, decreasing as speed increases. Naturally other factors will come into play, experience being a key one, as mentioned by Claire.

They are respectable figures but a decent glider will do close to double that of a passenger jet. By comparison, a Cessna 172 is about 11/12.

Yes, RATs are generally not considered welcome on commercial planes, they tend to chew things...

 

[2322]

I agree! Attendants are primarily there for passenger safety. If they didn't serve drinks or toss you peanuts they'd still have to be there. It takes a top crew to prevent panic amongst the foreigners while getting everyone to safety. Thank goodness most of the people on that flight were British:

"I say Nigel, aren't we descending prematurely?"
"Quite right Muriel, I believe so. Isn't that interesting?"
"Oh! Nigel! I do believe we have crash landed!"
"We certainly have Muriel. Are you altogether? Do you see any flames?"
"No, I'm not alright! My stockings have a run in them!"
"Blasted airlines. Air travel these days. Say Muriel, isn't that your nanny's old house?"
"Where?"
"Just over there. No dear, look through the crack in the fuselage."
"Why yes it is! Dear Brooks! I wonder if she's still alive?"
"Perhaps we should walk over and pay a call?"
"Not with this ghastly run in my stocking."
"What was that? I can't hear you over these infernal panicked foreigners."
"I said, "NOT WITH THIS GHASTLY RUN IN MY STOCKING!"
"Oh yes, of course. Quite right."

As a flight attendant I have to say good for the flight attendants on that flight. The training that we repeat once a year mandates that we evacuate the plane in ninety seconds if there should be an emergency. They did this that day! Its actually really tough! Amazing that there was no prep or notification.

 

[SpeedoGuy]

My experience of gliding a 'powered aircraft' was pretty much limited to certification requirements though I sometimes did it for fun. I've never flown or even been in a glider.

I finally earned a glider certificate endorsement on my private license. Soaring is a very interesting and valuable experience. In fact, I would think it would be beneficial for student pilots to fly a few hours in gliders first before taking to a powered aircraft. Why? Because the subtleties of the craft's aerodynamics can be sensed much more directly through the stick, rudder, and seat-of-the-pants than in a powered craft. Its a very, shall we say, intimate, way to learn basic flight characteristics. :smile:

 

[dong20]

Roatan was a very sleepy paradise when I went in the late 80's but I've heard it is very developed now. Beautiful white sand beaches. The diving not so great a week after a storm however. The thing I remember most of the trip were the vicious sand fleas on Cayos Cochinos, where I stayed and the bucket full of lobster tails picked off the sea floor for dinner.

Sounds good. I was in Utila in '94 it was pretty sleepy by day but woke up at night. The diving was good but did deteriorate markedly after storms.

I may have gone thru La Ceiba coming back but I don't remember it very well, not even the alligator pond. I was there in the late 80's.

May have been a later addition, it wasn't a very big pond. I don't recall La Ceiba that well almost 15 years on. I spent a short while in Trujillo (down the coast), there is (or used to be) an annual music festival but I missed it.

I recall the sandflies on Utila used to bug most people but they mostly left me alone, I must have smelled bad, or something! I used to laugh at the folk trying not to scratch then giving in and letting rip. The relief on their faces was great but that changed if they suffered the common resulting sores. I always expected to be next but it never happened.

I did get some nasty coral cuts on my lower leg and ankle not long before I left, justice I suppose as they took weeks even a couple of months to heal fully.

 

[dong20]

I finally earned a glider certificate endorsement on my private license. Soaring is a very interesting and valuable experience. In fact, I would think it would be beneficial for student pilots to fly a few hours in gliders first before taking to a powered aircraft. Why? Because the subtleties of the craft's aerodynamics can be sensed much more directly through the stick, rudder, and seat-of-the-pants than in a powered craft. Its a very, shall we say, intimate, way to learn basic flight characteristics. :smile:

I agree. I imagine many PPLs had had some glider experience as teenagers (ATC clubs etc) but I never did.

I wasn't a 'club' person. I even hated the cub scouts. After one, enforced attendance I never returned, it seemed stupid having people run around in silly outfits going dib dib dib and calling each other strange animal names and getting badges for stuff.

 

[ClaireTalon]

I finally earned a glider certificate endorsement on my private license. Soaring is a very interesting and valuable experience. In fact, I would think it would be beneficial for student pilots to fly a few hours in gliders first before taking to a powered aircraft. Why? Because the subtleties of the craft's aerodynamics can be sensed much more directly through the stick, rudder, and seat-of-the-pants than in a powered craft. Its a very, shall we say, intimate, way to learn basic flight characteristics. :smile:

I'm absolutely with you on the gliding experience, it's among the things I have never tried in an aviatory sense (the other thing is helicopter piloting, I only trust in fixed wings!). But I have tried a no-power glide in a MD-11 simulator. From an altitude of 35,000 I got a gliding distance of 85 miles with headwinds, didn't put me on the runway though. That is about 15 miles less than it should have made (the KC-10 had an optimum glide ratio of ~ 1:17.7 - 18), but my initial descent was... harsh.

Jet engines require air flow/pressure to start not (just) electrical power. The APU provides this on the ground. Inflight; in simple terms, engines are restarted in variety of ways, rapid restart (to take advantage of the existing rpm speed - but beware of overheat), APU assisted restart (as on the ground) or as last resort by flying at the appropriate speed to generate the required airflow/inlet pressure, introducing fuel and then igniting it. Et Voila, a windmill restart occurs, one hopes! This isn't first hand knowledge, only what I've learned over the years from flight crew and reading - my hands on experience is single prop only, I'm sure Claire can fill in the details.
<.>

If you had left me any to fill in. However, rapid restart is hardly ever executed since it has to be executed as long as the intake pressure is still high enough, even with a spooling down engine. It's either restarting with APU power, which in turn requires starting the APU, or windmilling with the help of a descent or other way to generate the required speed (depending on aircraft and engine type, around 200 kts). Needless to say, at 600 ft AGL and 2 miles short of the runway, all these options can be trashed well and good.

I wasn't a 'club' person. I even hated the cub scouts. After one, enforced attendance I never returned, it seemed stupid having people run around in silly outfits going dib dib dib and calling each other strange animal names and getting badges for stuff.

Are you referring to the Naval Air Service? :tongue:

 

[SpeedoGuy]

I wasn't a 'club' person. I even hated the cub scouts. After one, enforced attendance I never returned, it seemed stupid having people run around in silly outfits going dib dib dib and calling each other strange animal names and getting badges for stuff.

Much the same for me.

I grew up in the "wilds" of northern California. My boyhood was spent fishing, hiking, swimming, mountaineering and generally being the master of my own fate from early on. I was trusted with firearms and wasn't afraid to venture off alone whenever the urge arose. And I often did.

When my mother tried to send me to a summer camp for boys in my teens it didn't work out very well. As an individualist, I was appalled by the regimentation of the camp, the constant oppressive supervision, and enforced communal games and activities. It was very juvenile. It often seemed like I wasn't even trusted to visit the outhouse without a permission slip from a camp counselor. I lasted about 3 days before asking to be sent home.

 

[dong20]

"Initial Report Update 23 January 2008

Since the issue of the Air Accidents Investigation Branch (AAIB) 1st Preliminary Report on Friday 18 January 2008 at 1700 hrs, work has continued on all fronts to identify why neither engine responded to throttle lever inputs during the final approach. The 150 tonne aircraft was moved from the threshold of Runway 27L to an airport apron on Sunday evening, allowing the airport to return to normal operations.

The AAIB, sensitive to the needs of the industry including Boeing, Rolls Royce, British Airways and other Boeing 777 operators and crews, is issuing this update to provide such further factual information as is now available.
As previously reported, whilst the aircraft was stabilised on an ILS approach with the autopilot engaged, the autothrust system commanded an increase in thrust from both engines. The engines both initially responded but after about 3 seconds the thrust of the right engine reduced. Some eight seconds later the thrust reduced on the left engine to a similar level. The engines did not shut down and both engines continued to produce thrust at an engine speed above flight idle, but less than the commanded thrust.
Recorded data indicates that an adequate fuel quantity was on board the aircraft and that the autothrottle and engine control commands were performing as expected prior to, and after, the reduction in thrust.

All possible scenarios that could explain the thrust reduction and continued lack of response of the engines to throttle lever inputs are being examined, in close cooperation with Boeing, Rolls Royce and British Airways. This work includes a detailed analysis and examination of the complete fuel flow path from the aircraft tanks to the engine fuel nozzles.


Further factual information will be released as and when available."


Air Accidents Investigation Branch: Accident to Boeing 777-236, G-YMMM, at Heathrow Airport on 17 January 2008 - Initial Report Update