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Boeing 787 faces new risk: limits on ETOPS

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Boeing 787 faces new risk: limits on ETOPS

Old 29th Mar 2013, 10:02
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A330 can dispatch for an ETOPS flight with the APU INOP. Emergency generator powered by hydraulics is an alternative power source.
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Old 29th Mar 2013, 10:06
  #22 (permalink)  
 
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The 787 can dispatch and operate 180 minutes ETOPS with the APU battery inop or even removed, as long as the Variable Frequency Starter Generator is working.

The same restriction applies to the APU itself. You can operate 180 minutes ETOPS with it inop or removed, (as long as the VFSG works).

Last edited by whatdoesthisbuttondo; 29th Mar 2013 at 10:10.
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Old 29th Mar 2013, 12:54
  #23 (permalink)  
 
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kaikohe76
as a matter of interest, can someone please confirm the current limit on the B777 thanks. Just wonder, if very unfortunately the 787 saga lingers on & with operating restrictions as well, could more 777s fill the gap?
As of December 2011, the 777 is now certified for ETOPS-330.

Air New Zealand 777s use ETOPS-240 for their Aukland-Los Angeles route.
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Old 29th Mar 2013, 15:33
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kiskaloo
And I understand that being from the UK, you must love all things Airbus since they design and build the wings for their commercial airplane families there.
You are trying to bring this discussion into a battle between Airbus and Boeing by your comment.
I have done longhaul on A330's and 767's with no inclination to favour either, but,and it's a big but, I have no intention of stepping onboard a 787 until the cause of the battery problem has been rectified, not the lashup that Boeing is presenting as a "fix".
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Old 29th Mar 2013, 17:17
  #25 (permalink)  
 
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matkat

You also mention above about the main battery powering the brakes am I to take that the B787 does not have a RAT?
It does have a RAT, but it wouldn't provide enough power to operate the brakes at landing speeds, so the battery is the backup.
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Old 29th Mar 2013, 18:13
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As above, the main battery is only the backup source for electric brakes. The normal source of brakes is the 28VDC.

The main battery provides power for:
• airplane power-up
• APU start (assists APU battery)
• refueling operations
• towing operations
• electric braking (as backup power source)
• captain’s flight instruments (energizes essential instruments until RAT
deployment)


The APU battery provides power on the ground for:
• APU start
• navigation lights (during battery-only towing operations)

Clearly the 787 isn't short of electric power sources. There are . . .

• four variable frequency engine starter/generators
• two variable frequency APU starter/generators
• three external AC power receptacles
• one Ram Air Turbine (RAT)
• one main battery
• one APU battery
• three flight control Permanent Magnet Generators
• two EEC Permanent Magnet Alternators

Last edited by whatdoesthisbuttondo; 29th Mar 2013 at 18:14.
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Old 29th Mar 2013, 23:05
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Clearly the 787 isn't short of electric power sources. There are . . .

• four variable frequency engine starter/generators
• two variable frequency APU starter/generators
• three external AC power receptacles
• one Ram Air Turbine (RAT)
• one main battery
• one APU battery
• three flight control Permanent Magnet Generators
• two EEC Permanent Magnet Alternators
All the other power supplies able to supply enough power for braking require a fuel powered generator when when in flight (Engine Generators or APU). The scenario that others have referred to is the "Gimli Glider" where an aircraft ran out of fuel and glided in for a deadstick landing.

My understanding is that many believe that the RAT won't be able to provide enough power for braking as the aircraft slows upon landing (note: I haven't seen this assumption confirmed or denied by Boeing).

So the question is: Will the FAA/JTSB, etc accept the statistical probability being execeedingly low that a 787 would not run out of fuel and lose a battery on the same flight, and therefore have no wheel braking?
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Old 30th Mar 2013, 00:31
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So the question is: Will the FAA/JTSB, etc accept the statistical probability being execeedingly low that a 787 would not run out of fuel and lose a battery on the same flight, and therefore have no wheel braking?
I would think, statistically,

run out of fuel
would be enough of an improbability that the FAA would not even have to consider it, even if the battery failed on EVERY flight.
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Old 30th Mar 2013, 00:44
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My understanding is that many believe that the RAT won't be able to provide enough power for braking as the aircraft slows upon landing (note: I haven't seen this assumption confirmed or denied by Boeing).
Whatever 'many believe', the Boeing manuals tells us this:

The main battery provides power for:
• airplane power-up
• APU start (assists APU battery)
• refueling operations
• towing operations
• electric braking (as backup power source)
• captain’s flight instruments (energizes essential instruments until RAT deployment)
In-Air Rat Only mode is active if loss of all electrical power to captain’s and first
officer’s flight instruments occurs in flight. The RAT energizes the captain’s flight
instruments and other essential equipment for flight controls, navigation, and
communication. The main battery provides standby power until RAT deployment.
There is no mention, in the entire manual, of the RAT having any effect on the wheelbrakes.
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Old 30th Mar 2013, 02:20
  #30 (permalink)  
 
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Pub User & whatdoesthisbuttondo

Its good to read some good technical facts. I am curious:

1. What drives the three flight control Permanent Magnet Generators and the two EEC Permanent Magnet Alternators.

2. What happens to the captain’s flight instruments etc if the main battery fails to provide standby power until the RAT deploys.
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Old 30th Mar 2013, 06:35
  #31 (permalink)  
 
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As For the Ram Air Turbine (RAT)

A Ram Air Turbine (RAT) serves as an emergency source of electrical and
hydraulic power. It has no operating time limits, airspeeds, or altitudes.

Nothing to suggest it won't power the brakes on the ground if the battery isn't working AND then somehow the aircraft is then run out of fuel. (I think someone asked about this highly unlikely scenario)

Hi Cool Guys,

Apologies for answering your question by click and pasting,

Permanent Magnet Generators

Three engine driven Permanent Magnet Generators (PMG) are the primary source
of power for the flight control electronics. These power sources are independent
from the main airplane electrical system, and are also independent from each
other.
A secondary source for flight control power is provided by the airplane’s 28 Vdc
bus distribution system, and the main battery. In addition, a backup system is
provided by dedicated batteries to assure positive flight control operation during
temporary power interruptions.

Permanent Magnet Alternators

Two engine driven Permanent Magnet Alternators (PMA) (one per engine) are the
primary source of power for the EEC. PMAs are independent from the main
airplane electrical system, and are also independent from each other.
A secondary source for EEC power is provided by the airplane’s 115v AC bus
distribution system. During engine start, initial EEC power is provided by the
airplane until the PMA is able to provide power. The airplane also serves as a
backup EEC power source if a PMA is inoperative.

So engine driven is the short answer. Like most aircraft, the methods of producing electrical power are Ground external, APU, Engine and Batteries and RAT.

As for you second question about flight instruments if there were no battery and then the RAT deployed? Remember the RAT is only required if

• both engines have failed (and in your scenario there wasn't an APU battery available to start the APU or fuel to run it)

• loss of all electrical power to captain’s and first officer’s flight
instruments

In this (again) extremely unlikely example, I expect there might be a short power interruption until the RAT came online. That would be seconds rather than minutes though.
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Old 30th Mar 2013, 11:34
  #32 (permalink)  
 
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A Ram Air Turbine (RAT) serves as an emergency source of electrical and hydraulic power. It has no operating time limits, airspeeds, or altitudes.
According to this link (Question 6): https://cramberry.net/sets/63118-757-hydraulics the RAT on a 757/767 requires a minimum airspeed of 130 knots. I don't know what the limit is for the 787, but it is clear that this equipment is designed and certified to provide emergency power in the air, not for electrical braking on a landing roll.

To claim that it has no operating airspeed limits would logically imply that that it could produce sufficient power if it was deployed while the aircraft was being towed. That would solve the battery rundown while being towed problem - just deploy the RAT and the aircraft will power itself!
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Old 30th Mar 2013, 13:04
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whatdoesthisbuttondo,

Thks for the reply. The 787 sure has a few power sources.

Just ignore eppy's little head banging exercise. I am sure everyone else understands you did not mean the RAT could be employed while towing
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Old 30th Mar 2013, 16:39
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everyone else understands you did not mean the RAT could be employed while towing
Yes! We do!....But the "Boeing Bullcrap" implies that the RAT will be the saviour IF all other power-sources fail.
This clearly isn't the case.

Main engines each drive 3 gennies (2 starter-generators, 1 alternator)

but, hold on, there are 3 alternators, 1 to each engine

Smell the bull**** yet???

APU drives 2 starter-gennies.
RAT= a glorified windmill-generator..... as such, it's SPEED-DEPENDANT

Basic physics, it turns apparent wind into electrical energy
Irrespective of fuel-levels ,a "dead-engine" scenario is VERY possible

Remember the "over the fence" BA Heathrow flight???
Plenty of fuel, but it didn't turn and burn...that was a "Tin" 'plane, with years of development and Empirical knowledge behind it.

Now we have a Plastic Fantastic and a whole lot of new issues to learn.

SO, We lose both engines in flight.....the batteries are U/s (but that's OK) RAT is deployed, but can't start the APU (making the sweeping assumption that it has enough capacity to start it)

Heroic aircrew plonk it on the ground into the teeth of a 120mph gale!....all our problems are solved....headwind reduces groundspeed and also powers the RAT so the brakes work.

IN real life, As airspeed drops, so will the RAT's output...that presents a real problem, as the likelihood of both batteries failing is currently , statistically very high....2 holes in the cheese are ALREADY lined-up.
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Old 30th Mar 2013, 19:57
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"Remember the "over the fence" BA Heathrow flight???
Plenty of fuel, but it didn't turn and burn...that was a "Tin" 'plane, with years of development and Empirical knowledge behind it."
Yes, but even as a lowly SLF. I also understand that the engines, while unable to provide the required thrust, were still producing adequate electrical power. They were turnin and burnin, just not quite fast enough! As I understand, even Capt. Sully's A320, with both engines damaged and not producing usable thrust, the engine generators were still producing electrical power and the A320 remained in normal law until splashdown.
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Old 30th Mar 2013, 23:58
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Seems 737 has serious issues

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Old 31st Mar 2013, 00:07
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Cockney steve.

"Irrespective of fuel-levels ,a "dead-engine" scenario is VERY possible

. . . . . . And later . . . . .

IN real life, As airspeed drops, so will the RAT's output...that presents a real problem, as the likelihood of both batteries failing is currently , statistically very high....2 holes in the cheese are ALREADY lined-up."

I don't agree with you that a double engine failure is "VERY possible", it is an extremely rare event. Especially one where a restart isn't possible. Also to say the likelyhood of both batteries failing is "statistically very high" is also simply untrue.

The 787 has had two individual battery incidents. I'm not sure how you decide a double engine failure or a double battery failure are at all likely. It's a bit sensationalist to suggest you think the aircraft might suffer a double engine failure and a double battery or even single battery failure on the same flight. You also don't know what speed the RAT will provide electric braking down to. I don't know why you're contradicting the Boeing statements about the RAT when you don't seem to have any relevant technical knowledge of it whatsoever.

The same kind of tiny probability leading to a double engine failure and then an unrelated failure of another crucial system would leave most aircraft in a very poor state to land and stop on a runway. A similar example might be a 757/767 suffering a double engine failure followed by a double hydraulic failure. Sure it's possible but let's not pretend its likely or some kind of design fault.
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Old 31st Mar 2013, 00:26
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Perhaps but it will still have an accumulator full of 1800psi nitrogen and hydraulic pressure to power the emergency brakes. Somerhing a 787 wont have
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Old 31st Mar 2013, 00:49
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Right but the 787 has engine generators, batteries, an APU and a RAT. Do you really think its likely, it will suffer a combination of failures that would leave it unable to stop on a runway?
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Old 31st Mar 2013, 09:01
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As I understand, even Capt. Sully's A320, with both engines damaged and not producing usable thrust, the engine generators were still producing electrical power
As I understand it he started the APU.
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