"ICING" : ses Risques sur : "Airframes", Moteurs & "Fuel Flow Systems", Tubes Pitot ......

European safety regulators have identified another suspected dual-engine icing event, involving a Rolls-Royce-powered [Vous devez être inscrit et connecté pour voir ce lien], and ordered precautionary measures centred on the water scavenge system******.
During take-off, the aircraft's right-hand [Vous devez être inscrit et connecté pour voir ce lien] engine suffered a temporary shortfall in engine thrust - prompting an 'engine stall' warning - before it recovered.
Investigation showed that fuel flow to the right-hand engine had been restricted. But it also determined that the left-hand engine had experienced a similar flow restriction shortly afterwards.
This thrust shortfall on the left-hand engine had been "insufficient to trigger any associated warning", says the European Aviation Safety Agency, adding that it was "only note through analysis of the flight data".

After the initial 'engine stall' warning on the right-hand powerplant, the pilots responded with standard procedures, which included retarding the throttle to idle.
No action was required to restore thrust on the left-hand engine. Both engines recovered fully and the remainder of the flight was uneventful.
EASA has not disclosed the identity of the carrier or the location of the incident, describing it only as a "recent in-service event".

But it says: "Based on previous industry-wide experience, the investigation of the event has focused on the possibility for ice to temporarily restrict the fuel flow."

While no fuel system fault has been identified, EASA says the operation of the water-scavenge system******, located at wing rib 3, "cannot be excluded" as a contributing factor.

EASA has issued an emergency airworthiness directive ordering the operators of Trent-powered A330s to deactivate the automatic standby fuel pump scavenge system****** which operates during taxiing and take-off. It is also prohibiting dispatch of aircraft with any main fuel pump inoperative.
"Testing and analysis are continuing, ...... to identify the root cause of the event," it adds.

Restriction of fuel to the engine,

as a result of ice accumulation, has become a high-profile concern since the dual-engine accident involving a [Vous devez être inscrit et connecté pour voir ce lien]-powered [Vous devez être inscrit et connecté pour voir ce lien] at London Heathrow in January 2008.
Ice-related fuel restriction on Trents is also suspected in single-engine incidents involving a Delta Air Lines 777 in cruise and an [Vous devez être inscrit et connecté pour voir ce lien] A330 during a go-around at Manchester.
EASA has already mandated a modification to the fuel-oil heat exchanger in Rolls-Royce Trent 800, 700 and 500 engines. It has not been confirmed whether or not the A330 involved in the incident had been modified.

Claims:

1. A fuel system comprising: a fuel line; a fuel pump having an inlet coupled to a fuel tank and an outlet coupled to the fuel line; and a water scavenging system having an inlet for collecting water from the fuel tank and an outlet coupled to the fuel line in parallel with the pump.

2. The fuel system of claim 1 wherein the water scavenging system is powered by the hydraulic action of fuel in the fuel line.

3. The fuel system of claim 2 wherein the water scavenging system comprises a constriction in the fuel line, and the outlet of the water scavenging system is located adjacent to the constriction whereby the hydraulic action of fuel in the fuel line draws the water into the fuel line by the venturi effect.

4. The fuel system of claim 3 wherein the outlet of the water scavenging system comprises an opening in the constriction in the fuel line.

5. The fuel system of claim 3 wherein the opening in the constriction in the fuel line extends around the circumference of the constriction.

6. The fuel system of claim 3 wherein the water scavenging system further comprises:a secondary venturi line having an inlet coupled to the fuel line, a constriction, and an outlet which forms the outlet of the water scavenging system; and a water scavenging line having an inlet for collecting water and an outlet located adjacent to the constriction in the secondary venturi line whereby the hydraulic action of fuel in the secondary venturi line draws the water into the secondary venturi line by the venturi effect.

7. The fuel system of claim 6 wherein the secondary venturi line passes through a wall of the fuel line.

8. The fuel system of claim 6 wherein the outlet of the water scavenging linecomprises a jet pipe which extends into the secondary venturi line.

9. The fuel system of claim 2 wherein the water scavenging system comprises: a water scavenging pump; and a motor having a power output coupled to the water scavenging pump and a fluid inlet coupled to the fuel line whereby the motor is powered by the hydraulic action of fuel drawn from the fuel line.

10. The fuel system of claim 1 wherein the fuel pump further comprises a re-circulating outlet.

11. The fuel system of claim 10 wherein the re-circulating outlet opens into the fuel tank.

12. A method of removing water from a fuel tank, the method comprising scavenging the water from the fuel tank; injecting it into a fuel line downstream of a fuel pump; and feeding it from the fuel line into an engine.

[Vous devez être inscrit et connecté pour voir ce lien]'s Glenn Research Centre has issued a contract to Aerospace Corporation to develop artificial ice shapes that will be used for wind tunnel testing as part of the agency's plan to develop more robust automatic flight control systems for aircraft.
The ice shapes will be attached to the wings and tail surfaces of a subscale model aircraft to determine "iced aircraft" aerodynamics, key measurements needed for digital simulations that NASA will use to develop the advanced control systems.
NASA notes that current automated aircraft control methods do not account for degraded aircraft performance and operations if ice builds up on wing and tail surface leading edges, effects that can lead to loss of control accidents.

Reports of eight in-flight and four on-ground unintended shutdowns of General Electric CF6-80C2B wide-body turbofan engines have prompted the US Federal Aviation Administration (FAA) to mandate a change out of the engine's electronic control unit (ECU).

A proposed airworthiness directive, to be published on 14 November (Sevrien : 2011) , will affect 697 CF6 engines.....

.....flying on US-registered widebody aircraft.

The directive supersedes a 2007 AD requiring a software upgrade (8.2.Q1) on the same ECU to increase the engine's margin to flameout after several incidents where engines had flamed out due to exposure to ice crystals and ice shedding into the engine.

With the new software in place, problems continued.

Devrions-nous dire, comme Alan JOYCE de Qantas, quand il y a eu l'incident regrettable du RR Trent 900 sur l'A380 de Qantas, ..... 'Le logiciel n'a pu rien faire ; il doit y avoir un défaut fondamental ("fundamental flaw") dans les conception et "design" du moteur' ? :lol: :roll:

FAA said it received two reports of "ice crystal condition flameouts", which prompted GE to develop another software upgrade (8.2.R) for the ECU. The new software included "improved inclement weather capability, and enhanced fuel metering valve fault handling logic to reduce the risk of [in-flight shut down] caused by intermittent fuel metering valve feedback signals", said the FAA.

Since that time however, there have been 12 additional engine shutdowns, eight in flight and four on the ground, with engines using upgraded ECU software and other upgrades.

The problem was found to be caused by ignition system induced noise that created dual-channel faults in the ECU computer.

In response, the proposed AD mandates replacing the ECUs with a new unit developed by GE to "eliminate the potential for dual-channel [computer] faults due to ignition system noise".

If finalised as written, the AD will give operators between six months (or 450 engine flight cycles) and 60 months (or 4,500 engine flight cycles) to change out the ECUs, depending on ECU part number.

The instrument rated private pilot of a Socata TBM 700 that crashed shortly after departure from Teterboro airport near New York City on the morning of 20 December was attempting to climb out of icing conditions at 17,000ft (5,185m) minutes before the aircraft spiralled into the ground, killing all five on board.

Investigators revealed that the outboard section of the right wing and "several sections of the empennage" were found 0.25nm (0.46km) southwest of where the fuselage came to rest, leading to speculation the pilot may have over-stressed the airframe during an attempted recovery from an ice-induced stall.

A US National Transportation Safety Board (NTSB) investigator speaking to reporters several days after the accident confirmed that a common theme in reports from witnesses was that the aircraft "spiralled" into the ground.

New York centre air traffic controllers had been advising airline pilots of "moderate" rime icing between 13,000ft and 18,000ft that morning when N731CA, en route from Teterboro to Atlanta, climbed through 10,000ft toward his planned cruising altitude of 26,000ft.

Before entering the clouds at 15,000ft, the pilot was told by controllers of reports of "moderate icing" between 15,000ft and 17,000ft.

"We'll let you know what happens when we get in there," the pilot told the controller. "And, ah, we can go straight through it. No problem for us."

According to the NTSB preliminary report, the 1,400h pilot reported being in icing conditions at 17,000ft and was given clearance to climb to 20,000ft. "The aircraft reached a maximum altitude of 17,900ft feet and then began to descend," the report states.

NTSB confirmed that the Pratt & Whitney Canada PT6A-powered TBM 700, manufactured in 2005, was equipped with a deicing system, including pneumatic boots on the wings and empennage leading edges, and that parts of the system survived the crash and will be analysed.