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747-400 ISFD Fun

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A photo taken of a real world 747-400 Integrated Standby Flight Display...

 

ISFD90.JPG

 

... and I survived :Tounge:

 

Questions for the experts  (sorry, no prizes given)...

1) What are those big red arrows?

2) Why is the (brown) horizon still visible when the pitch scale shows 90 and 70 degrees?

3) Not shown.. .but what happens when you push the "APP" and "IN/HP" buttons on top of the ISFD simultaneously for two seconds? =@

4) What type of gyro is fitted?

5) What option is there regarding ILS information?

6) How did I survive?

 

Cheers

John H Watson

 

 

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1) Big arrows help you have some sort of reference in order to recover from unusual attitude (latest trend is to refer to it as upset recovery) and put the nose in the right direction.

2) For the same reason as 1) Giving you a hint where is the sky and where is the ground

3) APP will display LOC and G/S scale on the ISIS, LOC and G/S signal when available. I think it is well simulated in PMDG products.

4) I can't speak for Boeing as I'm an Airbus guy, on Airbus the data source for the ISIS is one or more ADIRU, Standby pitot and static probes and it has an accelerometer/gyrometer of its own, what type I wouldn't know, but it's the non noisy type. :-)

5) as per 3)

6) If you applied the correct Upset Recovery Procedure for big airplanes, you pitched down, level the wings and gradually and gently applied thrust. If you were very very good you also avoided a secondary stall by maintaining the stick down and accepting the altitude loss until well out of the stall.

 

On this picture, the HDG red flag is probably due to Air Data Reference source failure.

 

Merry Xmas

 

Mike

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6) - you were in a sim

 

before people say it was a real-world gauge, so are sim gauges (full simulators)  :wink:

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If you consider this fun, are you sure your name is not Sheldon Cooper?

 

 

A long lost relative (of Sheldon) :Tounge:

 

Not a sim, folks... It was on the real aircraft ... However...

 

The ISFD comes with a rear electrical harness which allows you to pull the instrument out of the main panel without powering down (and you can put the ISFD in some unusual attitudes). This is not recommended, however (at least not for very long periods). If the instrument is in a certain position for a while, it assumes it's back to straight and level flying and starts looking for "local gravity". It thinks these unusual attitudes are normal. When you put the instrument back into the main panel, the reset button has to be pushed.  

 

Mike had some pretty good answers :wink: Well done.

 

Regarding the APP button, there is an option to show Back Course (ILS). My old airline didn't think flying Back Course was prudent, so didn't have this option.

The internal gyro uses the principle of piezoelectrics. Force applied on (an array of) quartz crystals due to gravity/acceleration produces an electrical output which is converted into attitude. Some time ago, Boeing got into trouble by selling a 777 with this type of standby instrument display to China. The same technology is used in sophisiticated missiles, so the USA didn't want this technology falling into the hands of non-aligned foreign powers.

As Mike says, the instrument doesn't make any noises (no moving parts... unless viewed at an atomic scale). In this respect, it's even more advanced than laser gyros. Even the laser gyros in the IRUs use a vibrator (not to overcome friction in moving parts, but to help overcome one of the shortcomes of laser gyro technology... "laser lock")

 

It's interesting to note (especially for sim developers) that the roll pointer doesn't disappear behind the altitude and speed displays at extreme attitudes (it appears on top of them, so you don't lose your roll pointer)

 

Geek lesson over for the day..

 

Cheers

John H Watson

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Missed one...

 

"3) Not shown.. .but what happens when you push the "APP" and "IN/HP" buttons on top of the ISFD simultaneously for two seconds?"

 

This is secret engineer stuff. It switches the display to a maintenance page which allows testing of the ISFD (and viewing of fault data). If you should accidentally find yourself on this page, immediately push the RST button :Tounge:

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