Sponsor Message:
Aviation Technical / Operations Forum
My Starred Topics | Profile | New Topic | Forum Index | Help | Search 
Why Does 777 Have Glass "backup" ADI  
User currently offlineJhooper From United States of America, joined Dec 2001, 6204 posts, RR: 12
Posted (11 years 3 weeks 4 days 3 hours ago) and read 6127 times:

I was wondering why the 777's backup ADI is glass rather than a physical instrument such as in the 767. Isn't the idea of a backup instrument to be as redundant is possible? By that logic, you shouldn't have both depend on electricity. I know people say that it's impossible to have a total electrical failure on the 777, but I'd never say "impossible".


Last year 1,944 New Yorkers saw something and said something.
15 replies: All unread, jump to last
 
User currently offlineN243NW From United States of America, joined Jul 2003, 1632 posts, RR: 20
Reply 1, posted (11 years 3 weeks 4 days 3 hours ago) and read 6118 times:

I too realize that a total electrical system failure in a 777 is possible, but it is extremely unlikely. Plus, the electronic backups are probably more reliable than their mechanical counterparts anyway.
-N243NW Big grin



B-52s don't take off. They scare the ground away.
User currently offlineCPH-R From Denmark, joined May 2001, 5999 posts, RR: 3
Reply 2, posted (11 years 3 weeks 4 days 2 hours ago) and read 6100 times:

But still, an analogue instrument would still have a very hard time to break down, compared to a EADI

[Edited 2003-08-26 20:55:27]

User currently offlineCancidas From Poland, joined Jul 2003, 4112 posts, RR: 11
Reply 3, posted (11 years 3 weeks 4 days 1 hour ago) and read 6087 times:

they are requred by the FAA, i'm pretty sure.

i once got caught using a garmin gpsmap 196 inflight. when i talked with the pilots later they explained to me not only why it was taken away from me but also that electronic instrumentation does update quicker that the instruments on board the a/c. shocked, i tried it in my 172. sure enough, it did update faster and was more acurate than the anologs.



"...cannot the kingdom of salvation take me home."
User currently offlineVC-10 From United Kingdom, joined Oct 1999, 3701 posts, RR: 34
Reply 4, posted (11 years 3 weeks 4 days 1 hour ago) and read 6079 times:
Support Airliners.net - become a First Class Member!

I too realize that a total electrical system failure in a 777 is possible, but it is extremely unlikely. Plus, the electronic backups are probably more reliable than their mechanical counterparts anyway.

Correct, they are more reliable than a mechanical stby instrument. Don't forget a mechanical stby ADI also has a gyro in it so it too needs electrical power. LCD's consume less power than conventional instrument


User currently offlineDash8tech From United States of America, joined Jul 1999, 732 posts, RR: 5
Reply 5, posted (11 years 3 weeks 3 days 23 hours ago) and read 6048 times:

It probably (dash8tech, not 777tech) runs off of the battery bus and thus with a complete electrical failiure it's still running off the batts.

User currently offlineLstc From Canada, joined Jun 2003, 320 posts, RR: 0
Reply 6, posted (11 years 3 weeks 3 days 19 hours ago) and read 6002 times:

But still, an analogue instrument would still have a very hard time to break down, compared to a EADI

This was the case not too long ago. Its taken a long time, but these electronic instruments have finally achieved a reliability level that makes them suitable as a standby instrument but with MTBF rates that are still slightly lower than many mechanical instruments.

FAR 25 requires that the loss of all sources of altitude or heading or attitude or airspeed must be extremely improbable. That includes the standby and main instruments. The term "extremely improbable" relates to a failure rate of 1x10E-09 per flight hour. So in many cases, to bring this failure rate to an acceptable level while using a less reliable electronic instrument, the main instruments may have to be a more robust (expensive) type or they may be a requirement to raise the redundancy. ie: 3 main altimeters instead of 2.

Of course the electronic standby instrument must be paired with a power supply that is independant of the aircraft generating system. This is usually in the form of a battery pack that is charged, but isolated from the main aircraft electrical system.

The battery packs must be capable of supplying power to the standby instruments for times varying from 30 minutes to a few hours depending on the operational approval sought.

It is interesting to note that the standby instruments must become operational with no flight crew action following a failure of the electrical system.



User currently offlineCdfmxtech From United States of America, joined Jul 2000, 1341 posts, RR: 26
Reply 7, posted (11 years 3 weeks 3 days 17 hours ago) and read 5977 times:

The B777, is of course different than most other airplanes. There is a SAARU (Secondary Attitude Air Data reference Unit) that contains the gyros and processes all of the information. It then sends this info to the Standby Attitude Indicator. The indicator is just a display...there is no gyro inside. The SAARU is powered by 28VDC. So in theory (as it has been said already), it is the same as other aircraft. You need 28VDC regardless.


User currently offlineFredT From United Kingdom, joined Feb 2002, 2185 posts, RR: 26
Reply 8, posted (11 years 3 weeks 3 days 14 hours ago) and read 5949 times:

There are even certified aircraft with no backup instrumentation visible. The backups are built into the displays, driven directly and will pop up automagically if the normal instrumentation fails, of at the press of a button.

How you do it is secondary to showing that it can provide the demanded reliability and redundancy!

Cheers,
Fred



I thought I was doing good trying to avoid those airport hotels... and look at me now.
User currently offlineMD-11 forever From , joined Dec 1969, posts, RR:
Reply 9, posted (11 years 3 weeks 3 days 13 hours ago) and read 5949 times:

The MD-11's operated by Swissair and later on Swiss also are equipped with a "glass backup instrument". The reason for this upgrade was the lesson learned from the SR111 accident. One finding was, that the position as well as the visibility of the standard backup instrumentation is not satisfying in case of smoke in the cockpit.

Cheers, Thomas


User currently offlineUTA_flyinghigh From Tunisia, joined Oct 2001, 6495 posts, RR: 50
Reply 10, posted (11 years 3 weeks 3 days 12 hours ago) and read 5938 times:

As you can see, even some classic 737's have glass backup instruments :
http://www.airliners.net/open.file/344388/L/
I don't know if that particular aircraft is an exception though.



Fly to live, live to fly - Air France/KLM Flying Blue Platinum, BMI Diamond Club Gold, Emirates Skywards
User currently offlineAJ From Australia, joined Nov 1999, 2391 posts, RR: 24
Reply 11, posted (11 years 3 weeks 3 days 12 hours ago) and read 5939 times:

The Boeing 747-400ER has also incorporated a LCD standby ADI (as well as the other electronic displays).

View Large View Medium
Click here for bigger photo!

Photo © Jason Milligan



User currently offlineLstc From Canada, joined Jun 2003, 320 posts, RR: 0
Reply 12, posted (11 years 3 weeks 3 days 7 hours ago) and read 5889 times:

FredT,

I'm curious. Is the "certified" aircraft you are talking about a FAR/JAR 25 aircraft or a GA aircraft?

I have a hard time believing you can meet the FAR/JAR 25 regulations with such a setup:

Sec. 25.1333

[Instrument systems.]

[For systems that operate the instruments required by Sec. 25.1303(b) which are located at each pilot's station--
(a) Means must be provided to connect the required instruments at the first pilot's station to operating systems which are independent of the operating systems at other flight crew stations, or other equipment.
(b) The equipment, systems, and installations must be designed so that one display of the information essential to the safety of flight which is provided by the instruments, including attitude, direction, airspeed, and altitude will remain available to the pilots, without additional crewmember action, after any single failure or combination of failures that is not shown to be extremely improbable; and
(c) Additional instruments, systems, or equipment may not be connected to the operating systems for the required instruments, unless provisions are made to ensure the continued normal functioning of the required instruments in the event of any malfunction of the additional instruments, systems, or equipment which is not shown to be extremely improbable.]




User currently offlineCx flyboy From Hong Kong, joined Dec 1999, 6603 posts, RR: 55
Reply 13, posted (11 years 3 weeks 1 day 7 hours ago) and read 5768 times:

In our 777s we have two standby instruments, one AH, and the ASI. The 777-300ER aparently has one single intergrated standby instrument just like a mini PFD, and we are considering having this retrofitted to our current 777s.

User currently offlineS.p.a.s. From Liechtenstein, joined Mar 2001, 967 posts, RR: 2
Reply 14, posted (11 years 3 weeks 1 day 7 hours ago) and read 5757 times:

Speaking about the backup ADI from the MD11, I made this same question to a friend who happens to be a F/O with Swiss and he told me that indeed it provides better reading and also no parallax errors.. About power source, he told me that it is connected to the INS 2 battery and to the plane's battery bus.

Lufti(LH) is also installing those to their MD11's and perhaps it will be standard retrofit from now on for another MD11s around.

Rgds

Renato



"ad astra per aspera"
User currently offlineCrosswind From United Kingdom, joined Nov 2000, 2598 posts, RR: 58
Reply 15, posted (11 years 3 weeks 1 day ago) and read 5734 times:
Support Airliners.net - become a First Class Member!

Newer B757s (so I would assume this also applies to 767s) have an electronic standby ADI. It appears to be an option on any new-build Boeing aircraft...

Regards
CROSSWIND


Top Of Page
Forum Index

Reply To This Topic Why Does 777 Have Glass "backup" ADI
Username:
No username? Sign up now!
Password: 


Forgot Password? Be reminded.
Remember me on this computer (uses cookies)
  • Tech/Ops related posts only!
  • Not Tech/Ops related? Use the other forums
  • No adverts of any kind. This includes web pages.
  • No hostile language or criticizing of others.
  • Do not post copyright protected material.
  • Use relevant and describing topics.
  • Check if your post already been discussed.
  • Check your spelling!
  • DETAILED RULES
Add Images Add SmiliesPosting Help

Please check your spelling (press "Check Spelling" above)


Similar topics:More similar topics...
Why Does Ksea Have Class D Airspace posted Thu Jun 16 2005 04:13:05 by Qxeguy
Tomahawk. Why does it have a bad safety record? posted Thu May 6 2004 16:37:04 by Bragi
Do Aircraft Controls Have To Be "calibrated"? posted Sun Nov 12 2006 21:26:09 by Jamesbuk
"I Have The Plane" Still Used In Flight Training? posted Fri Jun 2 2006 09:46:11 by Varig767
Why Did Soviet Airliners Have Glass Nose? posted Sun Sep 11 2005 15:13:26 by TaromA380
Does The 777 Have Outboard Flaperons Or Not? posted Mon Aug 15 2005 00:54:45 by UAL747
Why Does Airbus Not Have C/n Numbers? posted Sun Jan 2 2005 15:29:23 by DeltaWings
What Does The Personal Suffix "A.A.E." Mean? posted Wed Dec 1 2004 04:34:35 by Corey07850
To Continue The "777 Brakes On Fire..." Topic posted Wed Jul 12 2000 12:14:50 by Cricri
Why Does The Tower Give Out Altimetric Reading posted Fri Nov 10 2006 02:58:14 by YULspotter

Sponsor Message:
Printer friendly format