Boeing 777 - it's quite safe as long as you are flying to somewhere warm

[Fred Bloggs]

Although redesigned Trent for the 777 will be reaady by 2010, boeing have stoped alot of orders for new developments and aircraft as they are on the S**t.

Versions of the Trent desinged by RR are in service on the Airbus A330, A340, A380 so do you wish to avoid those as well then!

No, I understand it is a Trent + 777 = Problem thing, Airbus should be OK.

[gingerjedi]

"Boeing 777 - it's quite safe as long as you are flying to somewhere warm "

At 30,000 feet it's going to be -50c no mater where you are in the world, the problem came about when the plane descended and the ice thawed leaving small chunks floating about in the fuel lines, this could be just a freak accident but it could potentially happen anywhere.

In fact you could argue that it would be a bigger problem in a warmer area as the thaw could happen at a greater altitude.

[scooterscot]

"Boeing 777 - it's quite safe as long as you are flying to somewhere warm "

At 30,000 feet it's going to be -50c no mater where you are in the world, the problem came about when the plane descended and the ice thawed leaving small chunks floating about in the fuel lines, this could be just a freak accident but it could potentially happen anywhere.

In fact you could argue that it would be a bigger problem in a warmer area as the thaw could happen at a greater altitude.

The problem only occurs as the plane approached the runway not at altitude - why is that?

I would expect a blockage to be less of a problem in a warmer climate.

[centurian]

The problem only occurs as the plane approached the runway not at altitude - why is that?

I would expect a blockage to be less of a problem in a warmer climate.

It can happen at altitude as well. It's happened on at least two occasions. Once on final approach (Heathrow) and another at altitude over the US.

The main difference is that when it happens at altitude, the blockage can be cleared quickly by going to max throttle and melting the ice - flight BA38 stalled before the ice melted.

[DaveB]

The reason it was happening at all was because of the flight procedures being used. The engines were being run at flight minimum during decent - Idling to you and me. This is done to conserve fuel, and therefore money. With the engines at idle speeds there is not as much heat in the oil/fuel heat exchanger to keep the fuel above freezing point. This is the part that is being redesigned to make it more efficient at lower oil temperatures.

In the mean time flight procedures have bee changed to periodically run the engines at higher thrust to maintain the temperatures needed for the fuel to be kept warmer.

The are also introducing a new procedure to pump fuel between tanks when a temperature difference is indicated to mix the fuel and maintain a higher temperature.

[centurian]

The reason it was happening at all was because of the flight procedures being used. The engines were being run at flight minimum during decent - Idling to you and me.

777 is a plane where it is quite difficult to lose altitude quickly - a good thing as it gives it a huge range if both engines fail.

As you say, you need to throttle back to idle just to get from 36,000 ft down to 3,000 in a reasonable timeframe. Even just a bit of thrust will mean the bird will stubornly refuse to descend quickly enough.

But once flaps and landing gear are down on final approach - then you need some thrust to keep the plane in the air - just when all the ice has built up...

[scooterscot]

So what's needed is a heater for fuel prior to use to make sure optimum temperature is achieved. A small reservoir will also be required I guess for sudden fuel consumption, i.e. landing.

Hard to believe something like this does not already exist, FMEA would have shown this.

[OwlHoot]

Maybe what they need is to incorporate some kind of vibrating mechanism to keep shaking off the ice before it has a chance to build up. Either a lightweight ultrasonic gadget, or even a programmed adjustment to the air or fuel intake to run the engines a bit "juddery" for a few seconds if that makes sense and wouldn't strain anything too much (besides the ice).

Heck, I'm wasted in IT - I should be an aircraft designer

[sasguru]

Something's not quite right here. The US safety board used the words "high probability" for another event. Yet 777s with Trent engines have presumably been operating for years and there are several with airlines round the world. So is it reasonable to assume there have been thousands of flights by this aircraft with these engines? Say, being conservative, 1000 flights?
And yet there have been only 2 events (Delta and BA)? So there is 0.002 probability of an event in any particular journey.
I wouldn't worry about odds of that nature.


It's in the US interests to play it up - they want to boost their local (GE) engines and discredit the RR ones.


PS Recently came back from holiday long haul in a BA 777 - I think it had the RR logo on the engines.

[scooterscot]

being conservative, 1000 flights?
And yet there have been only 2 events (Delta and BA)? So there is 0.002 probability of an event in any particular journey.
I wouldn't worry about odds of that nature.

I'm glad these planes all have the same amount of flying hours on the clock.