UTA_flyinghigh
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A Question On LCD Emergency Instruments

Tue Nov 25, 2003 6:00 pm


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...now that most, if not all latest-generation aircraft have LCD emergency instruments (and some older ones as well), how long would the batteries powering them last in the event of total engine failure ? (a la TS 332 for example)
Will
Fly to live, live to fly - Air France/KLM Flying Blue Platinum, BMI Diamond Club Gold, Emirates Skywards
 
vikkyvik
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RE: A Question On LCD Emergency Instruments

Tue Nov 25, 2003 7:09 pm

I'm no expert, but aren't most modern airliners' main (as opposed to emergency) instruments either CRT or LCD these days? Or is there a distinction that I'm not aware of (which is very possible)? I might be confused just because the picture is of a 733 which seems to have CRT main instruments, with analog/gyro or whatever backups.
~Vik
I'm watching Jeopardy. The category is worst Madonna songs. "This one from 1987 is terrible".
 
707CMF
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RE: A Question On LCD Emergency Instruments

Tue Nov 25, 2003 8:01 pm

Can you spell PLUG ?

707,Elbonian plugger
 
dw747400
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RE: A Question On LCD Emergency Instruments

Wed Nov 26, 2003 1:30 am

I'd be willing to bet they can last longer than the gliding time of the given aircraft...

Additionally, all aircraft that rely on electrical power for emergency instruments, flight control, etc. have Ram Air Turbines that can provide a little bit of power in the event of total generator or total engine failure. Additionally, you have the APU available. Some of the pilots here might be able to share some numbers or procedures, but fro my understanding, in most instances that result in loss of your engine-driven generators, you probably have bigger things to worry about.

CFI--Certfied Freakin Idiot
 
mandala499
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RE: A Question On LCD Emergency Instruments

Wed Nov 26, 2003 2:08 am

The case of the PK-GWA crash last year, both engines flamed out on descent below FL150 and instead of turning on the APU, they tried to Flight Start the engines. Those batteries went flat pretty quick...

So, don't try and FLT START the engines, get the APU on first... *unless cumulus granitus is very very near!*

Mandala499
When losing situational awareness, pray Cumulus Granitus isn't nearby !
 
avt007
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RE: A Question On LCD Emergency Instruments

Wed Nov 26, 2003 2:13 am

Look on the captains panel, there is a electronic standby horizon. From what I remember you have a typical 30 minute battery life with no other sources such as RATs. A couple of nit-picking points; you can have total generator failure without engine failure. So you could be mid-Atlantic with no generators, but the engines will still get you across. Not all aircraft have RATs, but probably the new generation ones that this thread started about do.
A lot of things have to go wrong before you are on batteries alone, but sometimes this can happen.
As far as whether electronic all-in-one standby instruments last longer, I don`t know. The only one that needs electriciity is the gyro horizon. Airspeed, altitude, magnetic compass, all these can be mechanical, and use no power at all. The reason the new units are popular is that they take up very little panel space, offer all the information in one place, and reduce the number of parts the operator has to stock and maintain.
 
dw747400
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RE: A Question On LCD Emergency Instruments

Wed Nov 26, 2003 6:27 am

Avt,

What I mentioned was that aircraft that rely on electronic flight controls or have standby instruments that are LCDs or CRTs have RATs. I know that some of the older aircraft don't, but I'm pretty sure that RATs are standard on the big FBW aircraft.

I believe the 747 also has a RAT, but it only provides hydraulic power... not sure about that. OF course, 747 doesn't have the same power demands as a 777, which I do know has a generator attached to its RAT.

As for generator failure without engine failure, I guess I was awfully vague on that... I'm with that its possible, though from what I know, it seems very unlikely. I would guess you could have bus or other electrical problems that produce the same affect as well.
CFI--Certfied Freakin Idiot
 
airplay
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RE: A Question On LCD Emergency Instruments

Wed Nov 26, 2003 6:35 am

The rules are slightly different depending on who’s rules you are operating under. In the FAA/TCCA world 30 minutes is the standard. In the JAA world, its 60 minutes.

There is some draft policy that many consider when designing these systems that increase this time to a more logical value depending on the typical aircraft operations. For example, why mandate only 30 minutes on a 180 minute ETOPS airplane?

I recently designed one such system for a business jet that meets the 180 minute constraint. With a full charge, a typical emergency battery pack can operated a typical electronic emergency instrument such as the Goodrich GH3100 for over 360 minutes.

One of the weaknesses of the electronic standby instruments is that ANY momentary disruption in power can cause them to fail and not be able to re-initialize in flight. So even minor disruptions are not tolerable.
 
avt007
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RE: A Question On LCD Emergency Instruments

Wed Nov 26, 2003 12:23 pm

dw, I hadn`t really thought about the FBW aspect, since I`ve never worked on them . Good point!

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