Incidente B-777 della British Airways

[paperinik]

Fuel feed interruption still in frame for BA 777 Heathrow accident: AAIB

By David Learmount

 

Partial interruption to the fuel flow still appears to be in the frame as a potential cause of the British Airways Boeing 777 crash-landing at London Heathrow airport on 17 January, according to a just-issued UK Air Accident Investigation Branch special bulletin (AAIB).

 

The Agency is careful not to state it as a cause, but concludes the interim report by saying that “a comprehensive examination and analysis is to be conducted of the entire aircraft and engine fuel system, including the modelling of fuel flows and taking account of the environmental and aerodynamic effects”.

 

The aircraft was descending through 720ft (220m) on final approach with the runway in sight when autothrottle, and then the crew, demanded an increase in thrust, but they only got a temporary response, following which the power reduced to the same level.

 

The report says: “By 200ft the airspeed had reduced to about 108kt (200km/h). The autopilot disconnected at approximately 175ft, the aircraft descended rapidly and its landing gear made contact with the ground some 1,000ft [300m] short of the paved runway surface.” At 108kt the aircraft was within a couple of knots of stalling speed.

 

The AAIB says it has tested all the electric and electronic engine and fuel system controls and found them to be working perfectly, and there is no indication in the flight data recorder of any such malfunction during the flight or the event itself.

 

Flight data shows that, at the moment of thrust reduction, the right-hand engine’s electronic control system was responding correctly to a reduction in fuel flow to the right engine.

 

This was followed by a similar response from the control system in the left engine when fuel flow to that powerplant also diminished.

 

The agency remarks, however: “Detailed examination of both the left and right engine high pressure fuel pumps revealed signs of abnormal cavitation on the pressure-side bearings and the outlet ports.

 

"This could be indicative of either a restriction in the fuel supply to the pumps or excessive aeration of the fuel. The manufacturer assessed both pumps as still being capable of delivering full fuel flow.”

 

The AAIB does not say whether it associates this evidence with the accident cause or not, but adds: “Investigations are now under way in an attempt to replicate the damage seen to the engine high pressure fuel pumps and to match this to the data recorded on the accident flight.”

 

When the report refers to studying the fuel flow system “taking account of the environmental and aerodynamic effects”, it appears to be referring to the fact that the temperature at high level right from the start of the cruise until well beyond the Ural Mountains in Russia, was “unusually low compared to the average”.

 

The minimum recorded outside air temperature was minus 76°, and the crew was monitoring the fuel temperature carefully.

 

The bulletin makes clear that, although the fuel freezing point of a sample of the fuel taken from the aircraft was minus 57°, the minimum temperature the fuel dropped to during the flight was only minus 34°.

 

Insignificant quantities of water and no other contaminants were found in the fuel, says the bulletin, but there were a few small items of debris found in the tanks, and the AAIB says it will be examining this evidence to see if it was relevant to the accident.

 

“There was no evidence of a mechnanical defect or ingestion of birds or ice,” says the AAIB special bulletin.

[paperinik]

Sarà mera coincidenza, ma si è verificato un problema analogo al triple-7 della BA, su un 777-200ER della American Airlines che si trovava in avvicinamento a Los Angeles ad una quota di 2000 piedi.

Se la causa del problema fosse confermata sarebbero almeno 3 gli incidenti legati alla manetta dei motori (ed al sistema di auto-manetta) del Boeing.

 

Vi posto l'articolo da Flightglobal (ovviamente in inglese, non ho tempo per tradurlo)

 

American investigates as 777 engine fails to respond to throttle

 

American Airlines is investigating an incident yesterday during which the engine on one of its Boeing 777-200ERs apparently failed to respond to throttle commands for several seconds during approach to Los Angeles.

 

The incident involved American’s flight AA299 from Miami and occurred at a height of around 2,000ft as the aircraft was descending to Los Angeles.

 

In an information statement to members, the Allied Pilots Association – which represents American Airlines cockpit crew – says the aircraft experienced a “hang-up” of its left-hand engine.

 

“The auto-throttles were on and the left engine hung at approach idle as the right engine accelerated normally,” says the association.

 

“It is believed that the left engine would not respond to throttle inputs for 10-15 seconds before finally responding and accelerating to the commanded thrust.”

 

All of American’s 777-200ERs are fitted with Rolls-Royce Trent 800 powerplants.

 

Maintenance personnel have downloaded the flight-data recorder information and will examine the fuel tanks and engine fuel filters for possible contamination. Tests will also be carried out on the electronic engine control.

 

Neither the US FAA nor the US National Transportation Safety Board has given any further information on the incident. The pilots’ association has not identified the specific aircraft involved. American Airlines could not immediately be reached to confirm the incident.

 

Investigators in the UK are still trying to determine the reasons why both Trent 800 engines on a British Airways 777-200ER failed to respond to throttle-increase commands during final approach to London Heathrow on 17 January, resulting in the aircraft crashing short of the runway

[Flaggy]

E' un po' che non se ne parla e visto che sono passati i mesi e l'inchiesta è andata avanti, sono andato in cerca di qualche sviluppo...

Ebbene? L'unica cosa certa è che il flusso di carburante è crollato quando invece doveva aumentare...

Le cause?

Al momento ancora nulla di definitivo...

Una causa che può scomparire senza lasciare traccia (che in effetti ad oggi non si trova...) è il ghiaccio, ma le temperature registrate durante il volo dovrebbero essere ben al di sopra di quelle che possono far ghiacciare il carburante e creare un'ostruzione localizzata da qualche parte fra pompa e serbatoio...

Mi sa che sarà un indagine che farà storia..

 

http://www.atwonline.com/news/story.html?storyID=12787

[Flaggy]

Un video aggiornato allo stato attuale delle indagini...

 

 

Interessante l'invito finale alla prudenza, visto che l'indagine non è giunta ancora a una spiegazione ufficiale dei fatti, e anzi si sta vagliando il concorso di più fattori, anche inusuali, ma che insieme possono spiegare l'incidente.

 

I link ad altri eventuali aggiornamenti in video verranno messi QUI

[-{-Legolas-}-]

Sembra incredibile, il 777 è pure un progetto nuovo di pacca.

 

Grazie degli aggiornamenti.

[Flaggy]

Un link che deve far riflettere su quanto siano serie e approfondite le inchieste sugli incidenti in aviazione, di quanto richiedano tempo e su quante e quali conseguenze effettive portino nella sicurezza.

 

Se non si fosse capito e' l'ennesima conferma che bisogna ad andarci con i piedi di piombo e attendere sempre le indagini tecniche prima di sbilanciarsi.

La la tragedia in Spagna va trattata con la stessa cautela...e a maggior ragione visto che sono morte tante persone.

 

http://www.flightglobal.com/articles/2008/...-fuel-flow.html

[Flaggy]

Visto che in un'altra discussione si era tirata in ballo la sicurezza in aviazione, ecco un esempio di come una seria e approfondita analisi di un incidente determini delle automatiche misure correttive, sia progettuali che procedurali, volte a evitare che si ripeta.

 

http://www.flightglobal.com/articles/2009/...-exchanger.html

[helio94]

Visto che in un'altra discussione si era tirata in ballo la sicurezza in aviazione, ecco un esempio di come una seria e approfondita analisi di un incidente determini delle automatiche misure correttive, sia progettuali che procedurali, volte a evitare che si ripeta.

 

http://www.flightglobal.com/articles/2009/...-exchanger.html

 

interessante..

[-{-Legolas-}-]

Visto che in un'altra discussione si era tirata in ballo la sicurezza in aviazione, ecco un esempio di come una seria e approfondita analisi di un incidente determini delle automatiche misure correttive, sia progettuali che procedurali, volte a evitare che si ripeta.

 

http://www.flightglobal.com/articles/2009/...-exchanger.html

 

Fondamentale direi...