777 Heathrow crash

[berettafan]

I thought airplanes were shielded to avoid such things?

I can't imagine that such a thing can be possible and yet isn't occuring on a regular basis with all the nutjobs we have in the world.

[red-beard]

Originally Posted by berettafan

I thought airplanes were shielded to avoid such things?

I can't imagine that such a thing can be possible and yet isn't occuring on a regular basis with all the nutjobs we have in the world.

Most electronics are shielded. But you can over come anything with enough power.

Early cellphones used up to 3 watts for sending. Most today, to increase battery life, use a few millewatts while in standby and use 50-60 millewatts while transmitting. But, if you have a single point transmitter, and you want to interfere with 50-60 millewatts at up to 1 mile away in all directions, I expect you would need several thousand watts.

2 things about this. If the antenna were designed properly, like a 5/8 wave antenna, it would be more powerful towards the horizon, and less towards the sky. The interference occurred at a lower altitude, so this may show it was "properly" designed.

Most industrial analog electronic control circuits work on the industry standard 4-20 mA signal. I'm not sure if aircraft use the same. They are tested to work against RFI. But, I can tell you that if I focused 2000 watts against most industrial equipment, it would not have a chance.

I can legally transmitt up to 2000 watts on any authorized frequencies, with the exception that I cannot purposefully or knowingly cause interference. Some of these are close too the cellular bands. In fact, with my license, I am only power restricted in the HF bands. Above about 60 MHZ, I pretty much can run 2000 watts. I could legally tune a microwave oven to an authorized frequency and transmitt.

A lot of this has been concidered over the year. Use a high power microwave transmitter to "cook" a pilot. I think most have found that at the combat distances, the power required or the time required would be too high.

I wonder if the PM knows he's being cooked?

[rick-l]

what does this mean? "abnormal cavitation
on the pressure-side bearings and the outlet ports"

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.

Continuing investigation
Investigations are now underway 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. In addition, comprehensive examination
and analysis is to be conducted on the entire aircraft and
engine fuel system; including the modelling of fuel flows
taking account of the environmental and aerodynamic
effects

aaib.dft.gov.uk

[Joeaksa]

Cavitation usually means there is not enough "head pressure" and the pump is not pumping evenly. Usually talking about air in the pumps but could mean several things in this instance.

To have both pumps do it at the same time is simply almost impossible unless there is something else going on.

[red-beard]

Cavitation occurs when the pressure in a fluid system is reduced to the point where it will start flashing to vapor. Air has nothing to do with it. It can occur in the suction side of a pump, due to low static pressure and high velocity. Pumps usually require a certain amount of static pressure (or head) to prevent cavitation.

The other way to create cavitation is with a restriction. The Bernouli Priniciple shows that total pressure is a combination of the static and dynamic pressures. If you increase the velocity, say with a restriction, the pressure goes down. This is the same way a wing works. You increase airflow over the top of a wing, reducing pressure, while maintaining normal pressure on the bottom of the wing. With enough surface area, a small differential creates a very large force.

The noise and destructive properties of cavitation come from the rapid creation of vapor, then collapse. This leads to erosion and eventually failure.

[rick-l]

So should it have said the damage to the bearings / outlet could have been caused by cavitation in the pumps?

I guess it must be the translation from British to English.

[red-beard]

These pumps use the fuel as a lubricant. You bleed some of the fuel back from the high pressure side into the bearings. If the bearing races were contaminated, it could cause cavitation.

However, this does not appear to be the problem. The fuel pumps were tested and shown by the manufacturer to still be within spec. There still is a problem where it appears that the fuel valves were comanded to close, but they weren't commanded to close by the fuel management system. RFI certainly could be a possibility here.

Maybe they need a tin foil hat for the valves?

[svandamme]

Originally Posted by stuartj

What this, "it refuelled in China". Whats the significance of that?

maybe it had lead in it too?

[red-beard]

According to the testing done on the 2 uncontaminated tanks, the fuel was fine. The center tank was damaged in the landing and had fire foam in it.

[MFAFF]

Originally Posted by rick-l

So should it have said the damage to the bearings / outlet could have been caused by cavitation in the pumps?

I guess it must be the translation from British to English.

Its not a matter of 'translation'; its a matter of meaning.....
The report aims to make clear what is observed, so 'signs of abnormal cavitation' are revealed.

It then illustrates potential causes of abnormal cavitation... however as it has not yet tested whether the signs are consistent with either potential cause they are not going to link one to the other as you have in your 'rewritten' phrase.

Once they can link the two they will or if they cannot they will not and the meaning will be clear, until then they take particular care to not put forward 'cause and effect' statements in interim reports.

Its written in English.. its just that you are reading it in American

[Normy]

The high-pressure engine-driven fuel pumps [injection pumps, mounted on the engine itself] are fed by lower-pressure electric boost pumps that exist inside the fuel tanks, kind of like some of the CIS cars. At low altitudes, most turbine-engine aircraft don't actually need the boost pumps, the engine pumps will provide suction feed. At high altitudes, however, the boost pumps are needed or the engine will likely flame-out.

Failure of the engine-driven pumps is an immediate flame-out no matter where you are at. The cavitation they are talking about could lead to excess shaft wear, since the lubricant [fuel, in this case] forms air bubbles in the bearings.

N

[nostatic]

is this related to Kimi's retirement in qualifying?

[surflvr911sc]

Originally Posted by Joeaksa

Well, the British aircraft accident investigation board has finally come around to the conclusion that I made several weeks ago: The event was RF( Radio Frequency )-induced.

Prime Minister Dr. Gordon Brown's motorcade was passing under the approach path of BA038. His security system utilized an RF transmitter to block out any cell-phone triggered devices. Apparently this system has a two mile range, and it caused the Boeing 777 EEC's (electronic engine controls) to sense a "overboost" situation, thereby commanding a reduced-thrust situation for the engines, simultaneously. Most interesting.

Joe, I know you know what you're talking about when it comes to aviation, but I am calling a big BS on this one (knowing that you weren't the source either).

I deal w/ some very impressive jamming (including cells) on a very frequent basis. It will block out most com, but you would have to be much closer than two miles even if it was powerful enough to take out electronics, unshielded included.

[Joeaksa]

Originally Posted by Normy

The high-pressure engine-driven fuel pumps [injection pumps, mounted on the engine itself] are fed by lower-pressure electric boost pumps that exist inside the fuel tanks, kind of like some of the CIS cars. At low altitudes, most turbine-engine aircraft don't actually need the boost pumps, the engine pumps will provide suction feed. At high altitudes, however, the boost pumps are needed or the engine will likely flame-out.

Failure of the engine-driven pumps is an immediate flame-out no matter where you are at. The cavitation they are talking about could lead to excess shaft wear, since the lubricant [fuel, in this case] forms air bubbles in the bearings.

N

Correct in some cases but in others there is not an electric but a jet pump (motive flow pump) that feeds the engine driven pump. These would have to had fail on both sides (extremely unlikely) then the engine fuel pumps also fail at the same time, which is even more unlikely.

At high altitudes I agree with the second statement but at lower altitudes the engines will not necessarly flame out if the engine driven pump goes out. Depends on the airplane, altitude, and so on but we have demonstrated that motive flow fuel pressure will keep the engine lit up to 15,000 ft in the Challenger.

[Normy]

Originally Posted by Joeaksa

Correct in some cases but in others there is not an electric but a jet pump (motive flow pump) that feeds the engine driven pump. These would have to had fail on both sides (extremely unlikely) then the engine fuel pumps also fail at the same time, which is even more unlikely.

At high altitudes I agree with the second statement but at lower altitudes the engines will not necessarly flame out if the engine driven pump goes out. Depends on the airplane, altitude, and so on but we have demonstrated that motive flow fuel pressure will keep the engine lit up to 15,000 ft in the Challenger.

I've always heard of the jet pumps as "ejector pumps". I'm not sure if the 777 has these or actual in-tank electric pumps [motor outside, impellor inside] as the 727 and 747 have. The engine driven pumps I am talking about are the primary high pressure pumps, mounted to the engine. Fuel from these is fed to the injectors, and at least on JT8D's and JT9D's, if these fail things tend to get disturbingly quiet...



I doubt it was a fuel pump issue anyhow; there's some sort of "bug" in that autothrottle system. Whether it is a hardware problem or a software problem is hard to say. Also, whether or not the whole of the fleet has this bug is another issue.

N

[Joeaksa]

Want to see what Boeing says?

If you can make heads or tails out of this missive from Boeing, you are a better man than I am...

~~~~~~~~

----- Forwarded by XXXX XXXXX/HEATHROW/BRITISH AIRWAYS/GB on 18/03/2008
07:47 -----

g.com>

To
18/03/2008 01:01
cc

Subject
777-200 G-YMMM ACCIDENT AT HEATHROW
AIRPORT LONDON, ENGLAND - 17 JANUARY
2008


FROM: THE BOEING COMPANY
TO: MOM [MESSAGE NUMBER:1-790833391-1] 17-Mar-2008 17:50:37 US
PACIFIC TIME
Multi Operator Message

The following is sent to all customers, field service bases, regional
directors, customer resident representatives and other selected
organizations. The following message contains confidential commercial
information and is intended only for the internal use of the individual or
entity to whom it is addressed and not for disclosure to others.

SERVICE REQUEST ID: 1-790833391
ACCOUNT: BOEING CORRESPONDENCE (MOM)
PRODUCT TYPE: Airplane
PRODUCT LINE: 777
PRODUCT: 777-200
ATA: 0230-00

SUBJECT: 777-200 G-YMMM ACCIDENT AT HEATHROW AIRPORT LONDON, ENGLAND - 17
JANUARY 2008

REFERENCES:
a) SR 1-753328471 (17 Jan 2008)
b) SR 1-754054424 (18 Jan 2008)
c) SR 1-756950441 (23 Jan 2008)
d) SR 1-765880033 (8 Feb 2008)
e) SR 1-771566362 (18 Feb 2008)

--------------------------------------------------------------
UPDATE 5 UPDATE 5
UPDATE 5 UPDATE 5
--------------------------------------------------------------

References a), b), c), d) and e) provide Boeing's previous fleet
communications on the subject event. Boeing, NTSB, FAA, Rolls-Royce, the
operator and other organizations continue to actively support the Air
Accidents Investigation Branch (AAIB) in the investigation of the accident.

Boeing has received reports on a number of 777 events over the past few
weeks regarding perceived non-normal operation of Rolls Royce 895 engines.
All reported events have been thoroughly investigated by both Boeing and
Rolls Royce with oversight by the appropriate government authorities. To
date, most of these reported events were determined to be normal operation.
None of these reported events are related to the landing accident at London
Heathrow on 17 January 2008.

Boeing appreciates that until the AAIB investigation of the subject
accident confirms a probable cause and appropriate resolution, 777
operators and flight crews may be highly sensitive to any perceived
anomalies with engine operation. To date, there are no recommended changes
to existing operational or maintenance procedures.

Boeing is working closely with Rolls Royce to support the on-going UK AAIB
investigation. The priority for all involved is to find the cause for the
G-YMMM accident and to determine any required mitigating actions.

Operators should continue their normal process of notifying Boeing of
non-normal operation of Trent 895-equipped 777s. These reports will be
investigated immediately. The key to performing these investigations
promptly is ready access to the Quick Access Recorder (QAR) and Flight Data
Recorder (FDR) data.

Boeing has no additional recommended operator action at this time. If the
investigation shows any specific actions are recommended or required,
operators will be notified.

Tom Dodt
Chief Engineer - Air Safety Investigation
The Boeing Company

BOEING PROPRIETARY
This message and any attachments to it contain or may contain Boeing
proprietary material which is protected by law and/or per the terms of
existing agreements with Boeing. Proprietary material may be used by the
recipient only as permitted under the terms of any such prior agreement
with Boeing. This message is intended only for the named recipients. If you
are not an intended recipient, you are hereby notified that any further
review, copying, use or dissemination of this message is strictly
prohibited. If you have received this message in error, delete it from your
computer and/or other storage medium and notify the sender immediately.

[rick-l]

Looks like Boeing has a form letter they send out when an engine anomaly is reported.

I bet there is a lot more sensitivity in the area of "perceived non-normal operation of Rolls Royce 895 engines" since that incident.

[Jim727]

Originally Posted by beepbeep

Ironic enough, it's often Boeing crew that attacks Airbus for being "plastic jet" and having FBW but now Beings only FBW jet seems to have belly-flopped beacuse of FBW??

Well, OK. Fbw only; hull losses only; all causes....

Boeing:

B777 (1):
This accident - and it may not be a hull-loss.
http://aviation-safety.net/database/dblist.php?field=typecode&var=107%&cat=%1&sorteer=datekey&page=1


Airbus:

A319-321 (16): http://aviation-safety.net/database/dblist.php?field=typecode&var=022-0%&cat=%1&sorteer=datekey&page=1

A330 (4):
http://aviation-safety.net/database/dblist.php?field=typecode&var=023%&cat=%1&sorteer=datekey&page=1

A340 (4):
http://aviation-safety.net/database/dblist.php?field=typecode&var=024%&cat=%1&sorteer=datekey&page=1

[air-cool-me]

water in fuel. ice.. a little turb... clogged up pumps.. thats my theory

[Jim727]

We shall see (unless, perhaps, it's from Brown's ecm). For a/c like this freezing of the fuel itself can occur.

I've heard the a/c will fly again.

Jim