Gary, you are quite correct. I was speaking of unintentional deployment. The 777 has a "squat switch" on it that will not allow the reversers to be deployed until the aircraft is on the ground and the wheels have spun up above a certain RPM to prevent air deployment.Garry Russell wrote:I think there is a confusion here with aerial deployment and unintentional/uncommanded aerial deployment
Heathrow
Moderators: Guru's, The Ministry
- Chris Trott
- Vintage Pair
- Posts: 2590
- Joined: 26 Jun 2004, 05:16
- Location: Houston, Texas, USA
- Contact:
Re: Heathrow
- forthbridge
- Concorde
- Posts: 1595
- Joined: 29 Aug 2007, 13:26
- Location: Stirlingshire, UK
Re: Heathrow
Interesting discussion.
As someone who is totally ignorant, I've a couple of questions that have got me a little baffled.
Obviously (and this is of course not to say we know the cause....) - in the absence of proof that some system failure was to blame, I'm interested in the fuel 'problem' theory so here are the questions...
1: Is it possible to under-fill a 777 in a manner similar to the 'Gimli' 767? (Note that this does not imply I am aiming any thought that the 777 was)
2: On larger aircraft, does the 'percentage' of fuel make any difference to available pressure feed to the engines?
3a: On fuel contamination, what is the primary worry? Water in the fuel or some other contaminant?
b: Is there any form of fuel filtration in-line from the tanks to the engines? Assuming filthy fuel could these clog up?
c: Assuming the other fuel theory - lack of - is there any thought as to how a leak could occur?
d: Is the reserve on large AC so low that contamination bad enough to ruin fuel left?****
***I ask as a meaningful diversion fuel qty for a 777 should be 'large' thus any contamination must be *very* significant
I suspect that like most incidents, this will prove to be a combination of factors - not simply one thing (as usual).
Of course all the above is pure interest on my part, not any attempt to theorise the cause!!
As someone who is totally ignorant, I've a couple of questions that have got me a little baffled.
Obviously (and this is of course not to say we know the cause....) - in the absence of proof that some system failure was to blame, I'm interested in the fuel 'problem' theory so here are the questions...
1: Is it possible to under-fill a 777 in a manner similar to the 'Gimli' 767? (Note that this does not imply I am aiming any thought that the 777 was)
2: On larger aircraft, does the 'percentage' of fuel make any difference to available pressure feed to the engines?
3a: On fuel contamination, what is the primary worry? Water in the fuel or some other contaminant?
b: Is there any form of fuel filtration in-line from the tanks to the engines? Assuming filthy fuel could these clog up?
c: Assuming the other fuel theory - lack of - is there any thought as to how a leak could occur?
d: Is the reserve on large AC so low that contamination bad enough to ruin fuel left?****
***I ask as a meaningful diversion fuel qty for a 777 should be 'large' thus any contamination must be *very* significant
I suspect that like most incidents, this will prove to be a combination of factors - not simply one thing (as usual).
Of course all the above is pure interest on my part, not any attempt to theorise the cause!!
Jim
Re: Heathrow
Now the reporters have commandeered a simulator to re-enact this accident.
Click on BA Pilot relied on training.
http://video.news.sky.com/skynews/video/
Nigel.
Click on BA Pilot relied on training.
http://video.news.sky.com/skynews/video/
Nigel.
I used to be an optimist but with age I am now a grumpy old pessimist.
- Garry Russell
- The Ministry
- Posts: 27180
- Joined: 29 Jan 2005, 00:53
- Location: On the other side of the wall
Re: Heathrow
As far as I know ......that's quite normal.
Garry
Garry
Garry
"In the world of virtual reality things are not always what they seem."
"In the world of virtual reality things are not always what they seem."
- Chris Trott
- Vintage Pair
- Posts: 2590
- Joined: 26 Jun 2004, 05:16
- Location: Houston, Texas, USA
- Contact:
Re: Heathrow
Possible, yes. Likely? Not in this case. The aircraft was being fueled in a country using metric unit on an aircraft using metric gauges. Gimli happened because of a failure to convert properly between metric and imperial units due to a failed gauge. In addition, the inoperable gauge refueling procedure was not properly followed, resulting in unnecessary calculations being performed leading to the failed conversion. In this case, no such conversion would have been required, although I suspect we would have heard if there was an INOP fuel gauge on the airplane already. The 777's fuel gauges are very reliable and I only had 1 occasions of an INOP gauge during my time at Denver on a 777 and it was due to the fact the valve lights on that tank were INOP so I had to manually fuel the airplane and not rely on the auto system to shutoff properly.forthbridge wrote:1: Is it possible to under-fill a 777 in a manner similar to the 'Gimli' 767? (Note that this does not imply I am aiming any thought that the 777 was)
Not usually. All pressure is created by the fuel pumps. They should be able to create a constant pressure until such time as the pump pickup becomes uncovered.2: On larger aircraft, does the 'percentage' of fuel make any difference to available pressure feed to the engines?
Water is the primary, but there could also be things like dirt, rust, and other particulates that can get into the fuel from pipelines and truck fuel tanks.3a: On fuel contamination, what is the primary worry? Water in the fuel or some other contaminant?
Yes there are screens, but depending on the amount of contamination, it is certainly possible to clog the filter which could then result in a filter bypass and the contamination reaching the engine potentially causing a shutdown. If it's a large "slug" of contamination that enters the system at the same time (as does happen) it's possible to overwhelm the filter screen and then shutdown the engines within a matter of moments.b: Is there any form of fuel filtration in-line from the tanks to the engines? Assuming filthy fuel could these clog up?
Every single joint, connection, and inspection panel could potentially spring a leak due to flexing during flight over repeated flights. Also, any removable fitting can come loose. Everything is safety wired to hopefully prevent anything coming loose, but safety wire can break, so it's possible. However, with the systems on the 777, any time the projected fuel on arrival drops below the required reserves on landing, it will scream at you that you're not going to have enough fuel. Had that happened, the crew would have reported that situation and diverted to a suitable airfield short of Heathrow.c: Assuming the other fuel theory - lack of - is there any thought as to how a leak could occur?
Depends on how much contamination there is and where it's at (i.e. floating or settled). Think of this - in a 777, a mere inch of fuel in one of the main tanks represents almost 200 gallons of fuel. So it's not hard to have plenty of fuel left in the tanks but still get contamination into the fuel pickups.d: Is the reserve on large AC so low that contamination bad enough to ruin fuel left?
- DispatchDragon
- Battle of Britain
- Posts: 4925
- Joined: 23 Feb 2005, 01:18
- Location: On the corner of walk and dont walk somewhere on US1
- Contact:
Re: Heathrow
Chris
You forgot to point out that 200 galls of JetA on any flat surface looks like a "substantial" fuel spill which is what
the Monty Orangeball crowd keep saying :roll:
Leif
You forgot to point out that 200 galls of JetA on any flat surface looks like a "substantial" fuel spill which is what
the Monty Orangeball crowd keep saying :roll:
Leif
- forthbridge
- Concorde
- Posts: 1595
- Joined: 29 Aug 2007, 13:26
- Location: Stirlingshire, UK
- Motormouse
- Concorde
- Posts: 1341
- Joined: 09 Sep 2004, 22:03
- Location: In a Hangar
Re: Heathrow
Thought I'd add a bit to Chris's reply re fuel sytems and this is 'generic' info not type specific;
1) Most of the time fuel for an individual engine will be drawn only from its' respective tank ie
left tank feeds left engine, right tank feeds right engine (in the case of the 'gimli glider' the source of the problem, a broken fuel pipe at the engine,was exacerbated by crew using 'cross-feed' to feed fuel from opposite tank to affected side)
2) Big aeroplanes usually have more than one pump in each tank, colloquially known as 'booster pumps' each one is capable of supplying all the necessary fuel to the engine driven high pressure pump, and below @ 10,000 ft, the 'suction' pressure alone from the engine pumps will keep engines running
ttfn
Pete
1) Most of the time fuel for an individual engine will be drawn only from its' respective tank ie
left tank feeds left engine, right tank feeds right engine (in the case of the 'gimli glider' the source of the problem, a broken fuel pipe at the engine,was exacerbated by crew using 'cross-feed' to feed fuel from opposite tank to affected side)
2) Big aeroplanes usually have more than one pump in each tank, colloquially known as 'booster pumps' each one is capable of supplying all the necessary fuel to the engine driven high pressure pump, and below @ 10,000 ft, the 'suction' pressure alone from the engine pumps will keep engines running
ttfn
Pete
An Elephant is a Mouse designed to
a government specification.
a government specification.
- Kevin Farnell
- Vintage Pair
- Posts: 2083
- Joined: 26 Jun 2004, 13:29
- Location: Willingham, Cambridge UK.
- Contact:
Re: Heathrow
Thanks for the clip, Nigel. It was interesting to see how the press jump to conclusions.Nigel H-J wrote:Now the reporters have commandeered a simulator to re-enact this accident.
Nigel.
A couple of points on the report.
1. The reporters have commandeered a 737 simulator. As no expert, I have no idea of the relevance of 737 glide characteristics to that of a 777-200.
2. From the clip, it appears that the simulator is flown at flight idle from 600 ft. The incident report (as I have read it), only states that no increase in thrust was available. There is no mention as to whether the engines were at flight idle or not.
Just shows, how well the press look into the facts.
Regards
Kevin
Stratospheric traces, of our transitory flight.
Trails of condensation, held in narrow paths of white...
Trails of condensation, held in narrow paths of white...