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dc10
Topic Author
Posts: 122
Joined: Sun Apr 01, 2007 11:53 pm

Standby Instruments

Wed May 03, 2000 7:30 pm

Look:
B717

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Photo © Justin Cederholm


B777

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Photo © Steven Ashley Wilson



I'm very surprised to see that the standby instruments are no more mechanical: in the B717, there is apparently no more standby intruments! and on the B777, the artificial horizon is apparently numeric...
If there is no more electricity, there is no more instrument then... okay, you can't move aileron because of the fly by wire!
Is there another security?
Thanks
DC10
 
FDXmech
Posts: 3219
Joined: Sun Mar 19, 2000 9:48 pm

RE: Standby Instruments

Thu May 04, 2000 1:41 am

The standby horizon, airspeed indicator and altimeter
are in one integrated instrument in front of the throttles
between the MFCDU's on the 717.
 
critter
Posts: 258
Joined: Thu Jan 13, 2000 1:36 am

RE: Standby Instruments

Thu May 04, 2000 2:00 am

The B717 has what is called an ISIS (Integrated Standby Instrument System). The Indicator is an LCD display and gives the following info.
1) precision Mach
2) baroset value
3) precision airspeed on a tape
4) slip/skid
5) pitch attitude
6) roll attitude
7) precision altitude on a tape

Power is supplied from the 28vdc Transfer bus which is essentialy one switch from the battery. The ISIS internally sends power to the Auxilliary ADM's (Air Data Module) to recieve the proper pitot and static readings. The rest of the information comes from the ADIRU's (Air Data Inertial Reference Unit), which are powered by there respective Right AC bus and 115 vac emergency bus. Therfore all power required to give indication on the ISIS is from a backup source and is displayed on a 6" X 6" display located in the forward center console between the two MCDU's (Multi Function Control Display Unit). The B717 is not fly by wire and therfore has cables running to all of the flight controls to provide attitude control.

critter
 
dc10
Topic Author
Posts: 122
Joined: Sun Apr 01, 2007 11:53 pm

RE: Standby Instruments

Thu May 04, 2000 3:34 pm

Thanks, I didn't know the 717 wasn't fly-by-wire!
Regards
DC10
 
Buzz
Posts: 694
Joined: Sun Nov 21, 1999 11:44 pm

RE: Standby Instruments, Part 4

Sat May 06, 2000 12:40 pm

Hi Dc-10, Buzz here. Critter had a good answer with the Super-DC9 cockpit, it looked like there was an "electronic meatball" up forward of the power levers.
And he touched on one topic that might be confusing: there's more than one source of electricity in an aircraft. The DC-8's and DC-10's had one knob to switch the Capt instruments and radio to the battery, which seldom melts down. Boeing airplanes usually run the Capt's instuments and radio off a "standby bus" which will take power from whoever it can (engines,APU, battery) so at least the left seat can fly and talk....
I don't know a lot about "Bigfoot", the 777. It's got LCD standby gauges which can run a long time on battery power. I don't know how it backs up the fly -by-wire stuff. The DC-8, DC-9, and DC-10 are also "fly by wires" airplanes, they use lots of steel cables and pulleys and bellcranks to move things. So what's the big deal? (grin). On the A320 series airplanes, the pitch is backed up by the manual horizontal stabilizer, and roll happens when you use the manual rudder, both steel cable. I guess it'll get you down to a runway...... In general i like the Airbus. You just have to learn a new language. g'nite
Buzz Fuselsausage, Line Mechanic by night, DC-3 Crew Chief by choice.
 
Guest

RE: Buzz 777 Pfcs Backup?

Wed May 10, 2000 12:59 pm

The 777 has cables to operate PCU on spoilers #4 and #11. Pitch control is done with alternate pitch control levers to operate left and right stabilizer trim control modules, porting hyd. fluid to the stab. trim motor/brake.
 
Buzz
Posts: 694
Joined: Sun Nov 21, 1999 11:44 pm

Thanks Yaki1

Wed May 10, 2000 7:42 pm

Hi Yaki1, Buzz here. Thanks for the info. I was asking around at work to find out the answer. I haven't been to Bigfoot school, they don't come to PDX. (well United's doesn't)
g'day
Buzz Fuselsausage Line Mechanaic by night, DC-3 Crew Chief by choice.

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